阅读说明：本技术 润滑剂喷涂器 (Lubricant sprayer ) 是由 E·艾泽巴赫尔 K·比纳 于 2020-02-13 设计创作，主要内容包括：本发明涉及一种润滑剂喷涂器,其包括填充有润滑剂的储存容器(1)和连接或可连接到储存容器(1)上的泵(2),通过该泵可从储存容器(1)输送润滑剂,所述泵包括具有入口(4)和出口(5)的泵壳体(3)、在泵壳体(3)中可线性移动地被引导的活塞(6)和作用于活塞(6)的驱动器(7),所述泵(2)借助其泵壳体(3)与储存容器(1)连接或可连接,活塞(6)可借助驱动器(7)循环地升高和下降,以便将润滑剂从入口(4)输送到出口(5)。所述润滑剂喷涂器的特征在于,所述活塞(6)构造成阶梯状并且具有限定上排挤室(8)的上活塞面(10)和限定下排挤室(9)的、相对于上活塞面(10)减小的下活塞面(11),所述上排挤室(8)通过第一阀(13)邻接入口(4),所述第一阀(13)被加载或可被加载到关闭的基本位置中,在活塞(6)中或上设置有通流开口(12a、12b),该通流开口在中间连接有第二阀(14)的情况下连接上排挤室(8)与下排挤室(9),所述下排挤室(9)通过出口通道(16)过渡到出口(5)中,当活塞(6)下降时,一方面通过在上排挤室(8)中产生的负压第一阀(例如克服弹簧力)打开并且润滑剂从储存容器被吸入上排挤室(8)中并且另一方面第二阀(14)关闭并且润滑剂从下排挤室(9)被压入出口通道(16)中,当活塞(6)升高时,一方面第一阀(13)关闭并且另一方面活塞(6)中的第二阀(14)打开并且润滑剂不仅从上排挤室(8)流到下排挤室(9)而且润滑剂也从下排挤室(9)被压入出口通道(16)中。(The invention relates to a lubricant applicator comprising a reservoir (1) filled with lubricant and a pump (2) connected or connectable to the reservoir (1), by means of which lubricant can be delivered from the reservoir (1), said pump comprising a pump housing (3) having an inlet (4) and an outlet (5), a piston (6) guided in the pump housing (3) in a linearly displaceable manner, and a drive (7) acting on the piston (6), the pump (2) being connected or connectable by means of its pump housing (3) to the reservoir (1), the piston (6) being cyclically raisable and lowerable by means of the drive (7) in order to deliver lubricant from the inlet (4) to the outlet (5). The lubricant sprayer is characterized in that the piston (6) is designed in a stepped manner and has an upper piston surface (10) which delimits an upper displacement chamber (8) and a lower piston surface (11) which delimits a lower displacement chamber (9) and is reduced relative to the upper piston surface (10), the upper displacement chamber (8) adjoining the inlet (4) by means of a first valve (13), the first valve (13) being loaded or loadable into a closed basic position, a through-flow opening (12a, 12b) being provided in or on the piston (6) which connects the upper displacement chamber (8) to the lower displacement chamber (9) with a second valve (14) being connected in between, the lower displacement chamber (9) passing into the outlet (5) via an outlet channel (16), the first valve being opened on the one hand by a negative pressure (for example, a spring force) which is generated in the upper displacement chamber (8) when the piston (6) is lowered and the lubricant being sucked from the reservoir into the upper displacement chamber (8) and the lower displacement chamber (9) being sucked in that the piston (6) and the lubricant is discharged from the reservoir On the other hand, the second valve (14) is closed and the lubricant is pressed from the lower displacement chamber (9) into the outlet channel (16), when the piston (6) is raised, on the one hand the first valve (13) is closed and on the other hand the second valve (14) in the piston (6) is opened and the lubricant flows not only from the upper displacement chamber (8) into the lower displacement chamber (9) but also from the lower displacement chamber (9) into the outlet channel (16).)

1. Lubricant applicator comprising a reservoir (1) filled with lubricant and a pump (2) connected or connectable to the reservoir (1) by means of which lubricant can be delivered from the reservoir (1), the pump comprising

-a pump housing (3) having an inlet (4) and an outlet (5),

A piston (6) guided in a linearly displaceable manner in the pump housing (3) and

-a drive (7) acting on the piston (6),

the pump (2) is connected or connectable to the reservoir (1) by means of its pump housing (3), the piston (6) can be raised and lowered cyclically in the piston receptacle (6') by means of a drive (7) in order to convey lubricant from the inlet (4) to the outlet (5),

it is characterized in that the preparation method is characterized in that,

the piston (6) is designed in a stepped manner with an upper piston surface (10) that delimits an upper displacement chamber (8) and a lower piston surface (11) that delimits a lower displacement chamber (9) and is reduced relative to the upper piston surface (10),

the upper displacement chamber (8) adjoins the inlet (4) via a first valve (13), the first valve (13) being loaded or loadable into a closed basic position,

a through-flow opening (12a, 12b) is provided in or on the piston (6), which connects the upper displacement chamber (8) to the lower displacement chamber (9) with a second valve (14) connected in between,

the lower displacement chamber (9) merges into the outlet (5) via an outlet channel (16),

when the piston (6) is lowered, on the one hand the first valve is opened by the negative pressure generated in the upper displacement chamber (8) and lubricant is sucked from the reservoir into the upper displacement chamber (8) and on the other hand the second valve (14) is closed and lubricant is pressed from the lower displacement chamber (9) into the outlet channel (16),

when the piston (6) is raised, on the one hand the first valve (13) is closed and on the other hand the second valve (14) in the piston (6) is opened and lubricant not only flows from the upper displacement chamber (8) into the lower displacement chamber (9) but also is pressed from the lower displacement chamber (9) into the outlet channel (16).

2. The lubricant sprayer according to claim 1, characterized in that the first valve (13) is loaded into the closed basic position by means of a spring force and is opened against the spring force by the negative pressure generated in the upper displacement chamber (8) when the piston (6) is lowered.

3. The lubricant sprayer according to claim 2, characterized in that the first valve (13) has a movable valve element (28) and a separate valve spring (29) loading the valve element (28).

4. The lubricant sprayer according to claim 2, characterized in that the first valve (13) has a resilient valve element (28') or is configured as such, which at the same time forms a valve spring (29').

5. The lubricant sprayer according to any one of claims 1 to 4, characterized in that the piston (6) with its upper piston face (10) can be moved in the upper end position against a first valve (13), for example a spring-loaded movable valve element (28) of the first valve (13) or a valve element (28') formed by a spring element (30').

6. The lubricant sprayer according to any one of claims 1 to 5, characterized in that the through-flow opening (12a) is integrated in the piston (6), for example in the upper piston part (6a), for example as a central through-hole (12a) in which a second valve (14) is provided, for example having a valve element which is guided movably and which is loaded by a valve spring (30).

7. The lubricant sprayer according to any one of claims 1 to 5, characterized in that the through-flow opening (12b) is formed by an annular space (12b) surrounding the piston (6), for example the upper piston part (6a), and the second valve (14) has a (resilient) seal (14') provided on the piston (6), as on the upper piston part (6a), or is formed by such a seal.

8. The lubricant applicator as claimed in one of claims 1 to 7, characterized in that the lubricant is delivered exclusively by suction by the pump (2) without additional pressure loading of the reservoir (1).

9. The lubricant sprayer according to any one of claims 1 to 8, characterized in that the storage container (1) is configured as a collapsible container or has a collapsible inner container during emptying.

10. The lubricant sprayer according to claim 9, characterized in that the storage container (1) is configured as a collapsible cup with a cylindrical flexible cup tube (18') or with such a collapsible cup (17'); or the storage container is designed as a bellows with an accordion-like container barrel (18) or with such a bellows (17).

11. The lubricant sprayer according to any one of claims 1 to 10, characterized in that the drive (7) is configured as an electromotive drive, preferably as a rotary drive, for example with a reversible direction of rotation.

12. The lubricant applicator as claimed in one of claims 1 to 11, characterized in that the drive (7) is connected to the piston (6) via a transmission (33, 34) which converts the rotary movement of the drive into a reciprocating or linear movement of the piston (6).

13. The lubricant sprayer according to any one of claims 1 to 12, characterized in that the upper piston surface (10) and the lower piston surface (11) are mutually coordinated such that the same volume flow is always delivered from the lower displacement chamber to the outlet channel (16) or outlet (5) when the piston (6) is raised and lowered.

14. The lubricant sprayer according to any one of claims 1 to 13, characterized in that the piston (6) is guided in a pump housing (3) such as a cylinder chamber therein in a rotationally fixed manner.

15. The lubricant sprayer according to any one of claims 1 to 14, characterized in that the stepped piston (6) has an upper first piston part (6a) and a second piston part (6b) connected to the first piston part (6a) on the lower side, the upper side of the first piston part (6a) forming an upper piston face (10) and the lower side of the first piston part (6a) forming an annular lower piston face (11).

16. The lubricant sprayer according to any one of claims 1 to 15, characterized in that the piston (6) has a cross section which differs from a circular shape, for example an oval or oblong or elliptical cross section, at least in sections, for example the upper first piston part (6 a).

17. The lubricant sprayer according to any one of claims 1 to 16, characterized in that a third valve (15) is provided in or on the outlet (5) or in an outlet channel (16), which third valve is loaded in the direction of the lower displacement chamber (8, 9).

18. Pump (2) for a lubricant sprayer according to any one of claims 1 to 17, having a pump housing (3), an inlet (4), an outlet (5) and a piston (6) guided in the pump housing (3) so as to be linearly movable, and a drive (7) acting on the piston (6),

the piston (6) can be raised and lowered cyclically by means of a drive (8) in order to convey lubricant from the inlet (4) to the outlet (5),

it is characterized in that the preparation method is characterized in that,

the piston (6) is designed in a stepped manner with an upper piston surface that delimits an upper displacement chamber (8) and a lower piston surface that delimits a lower displacement chamber (9) and is reduced in relation to the upper piston surface,

the upper displacement chamber (8) adjoins the inlet (4) via a first valve (13), the first valve (13) being loaded into a closed basic position,

a through-flow opening (12a, 12b) is provided in or on the piston (6), which connects the upper displacement chamber (8) to the lower displacement chamber (9) with a second valve (14) connected in between,

the lower displacement chamber (9) merges into the outlet (5) via an outlet channel (16),

when the piston (6) is lowered, on the one hand the first valve is opened by the negative pressure generated in the upper displacement chamber (8), for example against the spring force, and lubricant can be sucked from the reservoir (1) into the upper displacement chamber (8) and on the other hand the second valve (14) is closed and lubricant can be pressed from the lower displacement chamber (9) into the outlet channel (16),

when the piston (6) is raised, on the one hand the first valve (13) is closed and on the other hand the second valve (14) in the piston (6) is opened and not only does the lubricant flow from the upper displacement chamber (8) into the lower displacement chamber (9) but the lubricant is also pressed proportionally from the lower displacement chamber (9) into the outlet channel (16).

19. Storage container (1) for a lubricant sprayer according to any one of claims 1 to 17, wherein the storage container (1) is connectable to a pump (2) of the lubricant sprayer, characterized in that the storage container (1) is configured as a collapsible container or has a collapsible inner container during emptying, the storage container (1) being configured as a collapsible cup (17) with a cylindrical flexible cup (18') or has such a cup.

20. Storage container according to claim 19, wherein the cylindrical flexible cup is connected, for example materially connected, with a rigid end cap (20) having a connection opening (21) for lubricant outflow, which rigid end cap is configured for connecting the storage container (1) with a pump.

Technical Field

The invention relates to a lubricant applicator (Schmierstuffdivider) comprising a reservoir filled with lubricant and a pump which is connected or can be connected to the reservoir and by means of which lubricant can be delivered from the reservoir (to an outlet or to a lubrication point connected to the outlet), the pump comprising a pump housing with an (upper first) inlet and an (lower second) outlet, a piston which is guided in the pump housing in a linearly displaceable manner and a drive which acts on the piston,

the pump is detachably connected or connectable to the reservoir by means of its pump housing, and the piston can be raised and lowered cyclically or cyclically by means of a drive in a piston receptacle (for example in a cylinder chamber) of the pump housing in order to convey lubricant from the inlet to the outlet.

Background

Such lubricant applicators are used, for example, for the automatic lubrication of machine or equipment parts, such as rolling bearings and sliding bearings, linear guides, chains or the like. The lubricant applicator is connected to a lubrication point (e.g., a bearing), for example, and can deliver lubricant at predetermined intervals or during the operation of the machine. As the lubricant, grease or oil is used, for example. The storage container is also referred to as a cartridge and such a cartridge can be detachably and replaceably connected to the pump or its pump housing to form a structural unit, for example by means of a screw connection, a plug connection, a latching connection, a bayonet connection or the like. In order to convey the lubricant from the reservoir to the outlet, the piston is raised and lowered cyclically by means of a drive, which is preferably designed as an electric drive, and the lubricant is thus sucked out of the reservoir and pressed out of the outlet. Such a lubricant applicator can be designed in particular as a single-point lubricant applicator, in which the lubricant applicator is connected to the lubrication point via an outlet directly or with a hose connected in between. Alternatively, the lubricant sprayer is used as a multipoint lubricant sprayer, in which either a plurality of outlets are present or a separate distribution device is connected to the outlets, by means of which distribution device a plurality of lubrication points at different locations can be supplied by means of a single lubricant sprayer via hoses. Such single-point and multi-point lubrication systems are known in practice in various embodiments.

A lubricant sprayer of the type mentioned at the outset is known, for example, from DE 10234881B 4. The reservoir is connected to a drive head which, via a tappet device having a control surface, converts the rotary motion of the control surface into a reciprocating motion of the tappet and thereby conveys lubricant from the reservoir to a lubricant outlet at the end of the tappet. In addition, a piston connected to the spindle is provided in the reservoir, through which piston lubricant is pressed out of the reservoir and supplied to the lubricant through-flow channel of the drive shaft.

From WO 2009/068135 a 1a lubricant applicator is known, which has a reservoir and an outlet channel, and a pump element for delivering lubricant, which is arranged between the reservoir and the outlet channel and has a piston which is sealed in a cylinder and is guided movably between two positions, in the intake position the cylinder being in flow connection with the reservoir. The piston and the cylinder are adapted to one another in such a way that, when the piston is moved in its intake position, a negative pressure can be generated in the cylinder relative to the pressure in the reservoir, which negative pressure serves to suck lubricant from the reservoir into the cylinder or to force it into the cylinder. When the piston moves in the cylinder in the opposite direction from its intake position, an overpressure is generated for the delivery of lubricant from the cylinder to the outlet channel. A check valve is arranged between the cylinder and the reservoir, which check valve is loaded into a closed position in which it prevents a flow from the reservoir. In one embodiment of the lubricant sprayer, a spring element is provided which acts on the pressure piston with a spring force, so that the lubricant in the reservoir is pressurized. In particular in the case of highly viscous lubricants, the spring element should be able to improve the discharge behavior of the lubricant from the reservoir. Alternatively, a membrane can be provided in the storage container, which membrane separates the region filled with lubricant from the region emptied. The diaphragm is deformable by gas pressure so that the filled area becomes smaller as the evacuation increases.

DE 10004778 a1 describes a piston pump for delivering liquids, more precisely in particular for delivering fuel, with constant pressure control. An opening to the storage container is provided on the suction side and an opening connected to the liquid consumer is provided on the pressure side. A cylinder chamber is provided in the pump housing, in which a pump piston is guided to be able to reciprocate by means of a drive. Furthermore, a storage chamber is provided, which is connected to the cylinder chamber via an overflow opening which can be closed by means of a control valve, in which a pressure piston which is acted upon by a spring element is arranged so as to be movable back and forth. On the intake stroke of the pump piston, liquid is pumped from the reservoir to the consumer.

It is known, for example, from DE 69223245T 2 in conjunction with paint pumps (farbpump) to transport media from a container by means of a piston which can be moved back and forth.

DE 112012000091T 5 describes an electromagnetic pump which is intended for conveying hydraulic fluid in a motor vehicle. The cylinder of the pump has a stepped inner diameter section, in which a piston is guided, which is designed with a stepped outer diameter section. A discharge check valve with a spring-loaded valve ball is integrated in the piston. Furthermore, an inlet check valve is provided, which also has a spring-loaded valve ball.

DE 2336282 describes a pump for liquids, in particular a lubricant pump, by means of which lubricant is circulated, in particular in an internal combustion engine, a transmission or the like.

Furthermore, DE 102016002263 a1 describes a delivery device for delivering a flowable medium, for example from a container designed as a cartridge.

Furthermore, a double-acting piston pump is described in CH 630443.

A pump element for a lubricant outlet is also known from EP 2128443B 1. A cylindrical pump chamber is formed in the housing, in which pump chamber a piston is movably arranged, said pump chamber having an inlet, an outlet provided with a check valve and at least one bypass opening. The bypass opening is arranged such that the piston can be moved back and forth between a first position, which releases the inlet and closes the bypass opening, and a second position, which closes the inlet and the bypass opening, for delivering lubricant through the check valve into the outlet, and can be retracted beyond the first position into a pressure relief end position, which releases the inlet and the bypass opening, for pressure relief between the outlet and the inlet, such that in the pressure relief end position the outlet and the inlet are connected in a flow manner by a bypass channel bypassing the check valve.

For example, DE 10148455 a1 describes a device for metering fluid to different points in conjunction with multipoint lubrication.

DE 102012220297 a1 relates to a lubricating device comprising a piston pump with a linearly movable piston which is movably arranged in a bore of a cylinder element in order to convey a defined amount of lubricant from a lubricant supply to a lubricant outlet, which piston is connected to a moving element to which the piston can be linearly connected. The moving element is configured as a linear stepper motor comprising a lead screw nut system.

Furthermore, EP 2538126 a1 describes a lubricant applicator with a reservoir and a pump device in which a piston can be moved back and forth to deliver lubricant. The storage container can be constructed as a bellows or be equipped with a bellows which contracts during the emptying process.

DE 102016101727 a1 also describes a lubricant applicator with a lubricant cartridge. The emphasis here is that the lubricant cartridge and the piston are made of biodegradable plastic and are each produced as an injection-molded part.

DE 102008038580 a1 discloses a collapsible storage container for a lubricant supply.

Another embodiment of a lubricant sprayer is known, for example, from EP 3330590 a 1. In the storage container, a piston is provided, which is lowered by the screw during the transport of the medium, so that in this embodiment the lubricant is also pumped by the piston in the pump region.

In order to ensure reliable emptying of the storage container and a defect-free delivery, in practice, in addition to the suction delivery by the pump, the lubricant is usually also pressurized, for example by means of a piston, more precisely in particular when viscous lubricants or greases are used and/or the lubricant applicator is to be operated at very low temperatures. The known pump of a lubricant sprayer has the disadvantage, on the one hand, of being complicated and expensive in construction and, on the other hand, of having the disadvantage and having only a pump function with reduced pump delivery performance.

Disclosure of Invention

Based on the known prior art and the described disadvantages, the technical task of the present invention is to provide a lubricant applicator of the type mentioned at the outset, which is characterized by an optimized delivery concept and at the same time is simple in construction.

In order to solve this problem, the invention provides the following teaching in a lubricant sprayer of the generic type mentioned at the outset: the piston has a stepped (lower) upper (first) displacement chamberAnd a lower piston face which is reduced in relation to the upper piston face and which defines a lower (second) displacement chamber on the upper side, which upper displacement chamber adjoins the inlet opening via a first valve which is loaded (for example by spring force) into a closed basic position,

a through-flow opening or a piston opening, which connects the upper displacement chamber with the lower displacement chamber with a second valve connected in between, is integrated or provided in or on the piston,

the lower displacement chamber passes into the outlet via the outlet channel, when the piston is lowered (for example from its upper end position), on the one hand the first valve is opened by the negative pressure generated in the upper displacement chamber (for example against the spring force) and the lubricant is sucked from the reservoir into the upper displacement chamber and on the other hand the second valve (in the piston) is closed and the lubricant is pressed from the lower displacement chamber into the outlet channel,

when the piston is raised (from the lower end position or in the direction of the upper end position), on the one hand the first valve is closed and on the other hand the second valve in the piston is opened and the lubricant not only flows from the upper displacement chamber to the lower displacement chamber but also (proportionally) is pressed from the lower displacement chamber into the outlet channel.

The cylinder chamber or displacement chamber formed by the piston receptacle, in which the piston of the piston pump is guided, is thus divided into an upper and a lower displacement chamber, more precisely by the stepped piston according to the invention having differently sized piston faces. In conjunction with the first valve and in particular the second valve arranged in or on the piston, a double-acting, continuously delivering piston pump is realized in the lubricant sprayer, so that lubricant is delivered each time the piston is moved and thus when the piston is raised and lowered. There is no empty or fill stroke to fill the chamber. A continuous or at least quasi-continuous delivery is achieved with only one piston, i.e. without idle stroke, in which lubricant is delivered during each piston movement. This is achieved in a structurally simple design by realizing a stepped piston with an integrated (second) valve, so that a minimum of components is required. The system also works very economically, since the driving energy is used for conveying the medium in each stroke, without idle strokes in between.

The drive for the pump piston is preferably designed as an electric drive, more precisely as a conventional rotary drive, the rotary motion of which or the drive shaft is converted into a reciprocating motion of the piston. For this purpose, the drive can preferably be connected to the piston via a transmission mechanism, which converts the rotary motion of the drive into a linear or reciprocating motion of the piston. It is particularly preferred that the electric rotary drive has a reversible direction of rotation, i.e. the direction of rotation of the drive is cyclically or periodically reversed, so that the cyclically reversed rotary motion of the drive is converted into a cyclically reversed linear or reciprocating motion of the piston.

The expressions "upper" and "lower" or "raise" or "lower" do not relate according to the invention to an absolute orientation in space, but rather to a relative movement or relative orientation with respect to the storage container, that is to say the storage container defines the expression "upper" such that the upper displacement chamber is directed towards the storage container and the lower displacement chamber is directed away from the storage container, and "raise" denotes a movement in the direction of the storage container and "lower" denotes a movement away from the storage container.

According to the invention, the storage containers and the pumps are not only functionally connected to one another (by means of lines), but they are also connected to one another in a mechanically detachable manner, for example by means of a screw connection, a snap connection, a bayonet connection or another type of form-fitting connection, to form a separable structural unit. During the connection of the pump housing to the storage container, a functional connection between the (upper) inlet of the pump housing and the (lower) connection opening of the storage container is also made.

The upper piston surface and the lower piston surface are preferably coordinated with one another in such a way that, when the piston is raised on the one hand and lowered on the other hand, the same volume flow is always conveyed from the lower displacement chamber into the outlet channel.

As already described, the upper displacement chamber adjoins the inlet opening via a first valve, which is preferably designed as a check valve, which is closed in the basic position and is preferably loaded into the closed basic position by means of force, more particularly preferably by means of a spring force. This means that, when the piston descends, the first valve is opened by the negative pressure generated in the upper displacement chamber, preferably against the spring force. The first valve may be realized in different ways in the structure. For example, the first valve can have a movable valve element and a separate valve spring which acts upon the valve element, more precisely preferably into a closed basic position. Alternatively, the first valve forming the suction valve can have an elastic valve element or be designed as an elastic valve element in a very simple embodiment. The spring action is thus produced by the valve element, which can be embodied, for example, as a structurally simple leaf spring. In order to achieve a defect-free sealing effect, such a spring element can be configured, for example, as a resilient metal sheet with an elastomeric sealing surface, which in the closed position is pressed against a (hard) mating surface. Alternatively, however, it is also possible to use only a resilient hard metal sheet without an elastomer sealing surface, which in the closed position is pressed sealingly against the elastomer mating surface. In a further simplified embodiment, a non-return valve without a spring or elastic element can also be realized, in which, for example, a valve element (such as a valve ball or the like) is pressed into a valve seat by the action of the medium to be pumped and is thus loaded into the closed position. Such a valve element can be moved into the open position by gravity when a negative pressure is generated in the upper displacement chamber.

The through-flow opening in or on the piston, as in the above-mentioned piston part, which has already been mentioned in connection with the second valve, can be configured, for example, as a through-hole, such as a central through-hole or a bore hole, in the piston or the piston part, in which the second valve is arranged, which second valve has, for example, a valve element that is movably guided and that is spring-loaded by the valve. In this regard, the check valve may be disposed in a through bore in the piston or piston member. In an alternative embodiment, the through-flow opening can be formed by an annular space surrounding the piston or the piston part thereon, which annular space is formed by dimensioning, for example, between the piston or the upper piston part and the wall of the piston receptacle or the cylinder chamber, respectively. In this embodiment, the medium therefore does not flow past the piston during the delivery process, but flows past the piston on the outer circumference (via the annular space). Here, a correspondingly designed seal, which surrounds the piston on the outer circumference and can be configured, for example, as an elastic seal, such as a V-seal, through which lubricant can bypass in one direction and which prevents passage in the other direction, assumes the function of the second valve.

In a particularly preferred embodiment and in particular in order to form the smallest possible dead volume, the piston can be moved with its upper piston face in the upper end position (with a reduction in the dead volume) directly against the first valve in its closed position, for example a (spring-loaded) movable valve element, for example a valve disk. Preferably, the first valve has a spring-loaded or elastically movable valve element, such as a valve disk, which, in the closed position, is flush with an inner upper stop surface of the pump housing or with an inner upper stop surface of the cylinder for the piston. In the upper position, the piston with its upper piston face moves directly against the stop surface and the valve element arranged flush in the stop surface, so that no dead volume remains or is reduced to a minimum. This results in a self-priming pump, by means of which lubricant can be sucked out of the reservoir without defects, without the reservoir or the lubricant having to be loaded with additional force or pretension (e.g., by a spring). According to the invention, in particular, an additional spring loading of the cartridge can be dispensed with, and a defect-free emptying can be achieved by means of an optimized pump action even for poorly flowing media and/or at low temperatures. By omitting the spring element, for example, the exudation of grease (ausblaten) which can occur in the prior art can be prevented. Furthermore, a piston in the storage container and thus also a downward movement (herunterspindel) or adjustment (nachfluen) of such a piston can be dispensed with, so that a particularly simple-structured storage container or cartridge can be used and also a complicated coupling of the piston or the threaded spindle in the storage container to the drive can be dispensed with. Overall, a self-priming pump with a minimum dead volume can deliver even viscous media without defects, while the construction of the pump on the one hand and the storage container on the other hand is very simple. Although it is particularly preferred to dispense with such additional force application, the continuous feed pump according to the invention can optionally also be realized by additional springs, to be precise, for example, at very low temperatures and/or for lubricants having a particularly high viscosity and therefore very poor flow properties.

In this connection, it is particularly preferred, though, to supply the lubricant from the reservoir only by suction by means of a pump, without additional pressure loading (by means of a spring, a piston or the like), i.e. to achieve a self-priming only construction. The invention may alternatively also comprise embodiments with additional force loading, such as with additional springs, in the described manner.

In a preferred embodiment of independent significance, the storage container is constructed as a (self-) collapsible container during emptying or the storage container has such a collapsible inner container. This means that during emptying of the container, the container self-collapses on account of the negative pressure generated inside the container and the container bottom is sucked in the direction of the pump. Thereby providing a storage container with significantly reduced waste products. Since not the container with the original container volume but only the collapsed container with a significantly reduced waste volume remains as waste, the handling is simplified. It is particularly preferred that, in addition to the collapsible storage container, a rigid, non-collapsible protective cap is provided, so that the filled storage container is arranged in the installed state in the protective cap. It is particularly preferred that the storage container can be fastened to the pump or pump housing by means of the protective cap. The cap itself is reusable, while the storage container is replaceable as a collapsible inner container and thus forms a disposable product with a minimum remaining volume.

In a first embodiment, the storage container (or its inner container) is configured with an accordion-like container cartridgeThe bellows of (1). In the case of lubricant applicators, such storage containers are known in principle as bellows. According to the invention, they are realized in the described continuous feed pump and particularly preferably in a self-priming pump without additional spring loading.

In a second embodiment, the storage container (or its internal container) is constructed as a collapsible cup with a thin-walled, flexible cylindrical sleeve (bechmantel), similar to that known for example in conventional disposable drinking cups. During the emptying process, the container bottom or cup bottom is sucked in the direction of the pump and the thin-walled cup is folded together here, leaving waste with a minimum residual volume, similar to a bellows. The solution with collapsible cup also has the following advantages compared to the solution with bellows: the residue can be emptied optimally, since no residual amounts remain in the bellows folds.

As already described, according to the invention, a double-acting piston having an upper piston face and a lower piston face is guided linearly within a pump housing or within a cylinder chamber or displacement chamber realized in the pump housing. In principle, during the reciprocating movement, the piston can be rotated in the cylinder chamber or displacement chamber, so that the rotary movement of the motor is converted into a reciprocating movement by means of a screw guide of the piston in the cylinder. In a preferred embodiment, however, the piston is guided in the pump housing or in the cylinder chamber in a rotationally fixed and thus non-rotatable manner. The rotational movement of the motor (e.g., an electric motor) can be converted, for example, by a screw drive (gewinnertree eb), in which a spindle or a spindle is rotatably guided. Such a screw drive may have, for example, a wheel which is designed with an internal toothing for a threaded spindle or a spindle guided therein, which is connected in a rotationally fixed manner to the piston. The screw drive is driven in rotation by the motor and during this rotational movement raises or lowers the threaded rod guided therein and thus the piston.

The piston is realized as a stepped piston and thus as a stepped piston, preferably T-shaped in cross section. The piston has a first piston member (upper part) and a second piston member (lower part) connected to the first piston member at the lower side, the upper side of the first piston member forming an upper piston surface and the lower side of the first piston member forming an annular lower piston surface. The lower displacement chamber may be configured as an annular displacement chamber. In principle, the displacement chamber can be cylindrical. In a preferred variant, however, the upper displacement chamber is not cylindrical in shape, i.e. it does not have a circular cross section, but rather a cross section which differs from a circular shape, for example an oval cross section. Thus, the upper first piston part and thus also the upper piston face have such a cross section. By this design, the piston is (without further measures) arranged in the housing/cylinder in a rotationally fixed manner, i.e. without additional anti-rotation means. But the lower second piston member may alternatively have a circular cross-section.

The first valve and/or the second valve are designed as check valves and are particularly preferably designed as spring-loaded check valves, the closing element of which is spring-closed in one direction and is relieved in the other direction by the medium pressure. Embodiments are also included in which the closing element on the one hand and the spring on the other hand are combined with one another to form a component, such as a self-elastic closing element, which can be made, for example, of an elastic sheet metal or the like. This applies in particular to the first valve. For the second valve, a valve-forming seal, such as a V-seal, can be used, for example, in the manner described.

In principle, the invention can be realized very simply by only the two valves described, namely the first valve and the second valve. In an advantageous embodiment of the invention, however, a third valve can also be provided in addition, that is to say in or on the outlet or in the outlet channel, which third valve is spring-loaded into its open position in the direction of the lower displacement chamber, i.e. counter to the conveying direction.

In principle, the lubricant applicator according to the invention with the first and second valves and the minimum dead volume already has the feature of a defect-free function, so that even a gas lock in the reservoir or in the case of a cartridge mounted on the pump does not lead to a malfunction. In the known embodiments, in which only a very low negative pressure is generated, such a gas lock leads to a malfunction, since no negative pressure is generated in each case, the pumping action is disturbed and only the enclosed air is compressed or expanded. A sufficient negative pressure is not generated and therefore no lubricant is delivered. In the embodiment according to the invention, a sufficiently high negative pressure is very quickly built up by the volume of the dead space minimized according to the invention, and the air which may therefore be enclosed is conveyed further without interfering with the lubricant conveying. A third valve, which can be optionally provided, ensures a faster delivery of the air possibly enclosed by the pump. The negative pressure required to suck in the medium is established more quickly. The manual venting required in the known pumps is not carried out, that is to say the pumps are self-venting. The air vented from the system through the third valve does not then interfere with the generation of negative pump pressure. It is also important that a hose is usually connected to the outlet of the pump, which hose leads to the lubrication point. Such hoses can be very long and the lines or lubrication sites can become clogged for various reasons. The long lines are sometimes interrupted and a T-piece with a grease gun interface is installed between them. Once the fitter has attached the grease gun to the interface, he can blow (freiblasten) the lines on the left and right sides of the T-piece with, for example, 200 bar pressure without any problems. An optional third valve prevents such high pressure from entering the pump from the outside. Thus, the third valve protects mechanical components within the lubricant sprayer.

In the context of the present invention, the motor is controlled in such a way that the piston is moved from the upper end stop to the lower end stop and thus a maximum delivery volume is achieved. Alternatively, however, the spray quantity (spendmenge) can be adjusted in a flexible and stepless manner, to be precise without any constructional adjustment, simply by controlling the drive accordingly in such a way that it runs for a longer or shorter time and thus limits the stroke. The spray quantity can thus be adjusted steplessly in situ electronically, more precisely by means of suitable motor control electronics, without any mechanical modification of the device. The suction volume can be designed relatively large by the large dimensions of the displacement chamber. In this way, a pump with very good suction capacity can be realized with a minimum of dead space.

In principle, the diameter or area difference at the piston can be designed such that the piston always delivers the same volume flow to the outlet, regardless of the direction of movement. Alternatively, however, the diameter difference can also be selected in such a way that only a very small amount of feed is pushed into the outlet during intake, and then only a short lifting movement in the direction of the intake valve occurs during further displacement.

The invention also relates to a pump of the type described for a lubricant applicator. The pump forms a single structural unit which is assembled with the reservoir into a lubricant applicator. The pump according to the invention is therefore also independently protected.

The invention also relates to a storage container for such a lubricant applicator, i.e. a storage container which is also independently protected, and more particularly preferably in the embodiment as a collapsible cup with a collapsible cup cartridge.

In summary, the present invention is based upon the following considerations in particular and overcomes in particular the difficulties in the prior art outlined below.

On the one hand, there is a challenge or need, particularly in single point lubricant sprayers, to achieve a small, desired spray volume per pump stroke. Such devices should generally force only a very small amount of lubricant (e.g., grease) into the respective lubrication points during each spraying action so that excessive pressure increases are not generated there (e.g., using a manual grease gun when manually adding lubricant). The pump chamber size of such devices is therefore typically correspondingly small. In order to feed the required quantity of lubricating oil to the lubrication points as precisely as possible in the sum of a number of sprayings, it is therefore important to comply with these quantities precisely, so that over a longer period of time no excessive or insufficient lubrication occurs. The smaller the stroke volume of the pump, the greater the disturbance of the dead volume, even the smallest dead volume, since these prevent the generation of negative pressure during suction and thus reduce the ability to suck grease at low temperatures. Therefore, there is a problem in the prior art that: even a minimal gas lock can prevent the suction chamber from filling, particularly in the case of viscous conveying media. To solve this problem, additional preloading or pre-conveying elements (such as springs acting on the storage container, etc.) are often used in the prior art. This can result in the grease in the storage container being kept at a more or less low pre-pressure and thus tending to ooze out. As an alternative, therefore, systems without a spring but with a positively guided pre-delivery piston are also used.

On the other hand, in practice, flexibility in the delivery rate is desired, i.e. it is desirable to be able to adjust the delivery rate per spray application to the respective requirements of the respective user. This is why the delivery of the pump element is preferably kept very small, so that a slightly larger spray quantity can be achieved by a plurality of spray strokes in direct succession. However, the prior art lacks the possibility of being able to adjust the amount of spray at will, since it must always accept multiples of a single spray.

These disadvantages are generally overcome by the design according to the invention, since on the one hand a large pump intake volume is provided and on the other hand a small delivery volume is still provided. Furthermore, by means of a corresponding control in combination with quasi-continuous delivery, an arbitrarily adjustable delivery volume can also be achieved for each spray application request during the intake stroke.

Drawings

The invention is elucidated below by means of one of the figures, which shows only an embodiment. The attached drawings are as follows:

fig. 1a, 1b show a vertical section through a lubricant applicator according to the invention in two different functional positions;

fig. 2a, 2b, 2c show enlarged partial views of the solution according to fig. 1a, 1b in three different functional positions;

fig. 3 shows a storage container according to a first embodiment of the lubricant sprayer of fig. 1a, 1 b;

FIG. 4 illustrates a storage container of a modified embodiment;

FIG. 5 shows the pump of the lubricant sprayer according to FIG. 1a without a storage container nested thereon;

fig. 6 shows a horizontal section (partial view) according to the solution of fig. 5;

fig. 7 shows a partial view of the solution according to fig. 5 in the region of the threaded spindle;

fig. 8 shows an embodiment according to a variant of the solution of fig. 1b, with an additional spring;

figure 9 shows a variant embodiment of the pump according to the invention;

fig. 10 shows in a schematic simplified diagram (partial view) another embodiment of a pump according to the invention, having two outlets;

fig. 11a shows a variant embodiment of a first valve element for the pump according to fig. 1 to 10;

FIG. 11b shows a perspective view of the valve element according to FIG. 11 a;

fig. 12 shows a modified embodiment of a second valve element for the pump according to fig. 1 to 10.

Detailed Description

In the figures, a lubricant applicator and thus a device for dispensing lubricant are shown, which lubricant applicator has, in its basic configuration, on the one hand a storage container 1 and, on the other hand, a pump 2, which can be assembled detachably into a structural unit, i.e., the pump 2 is connected or connectable with its pump housing 3 to the storage container 1, so that lubricant can be delivered from the storage container 1 by means of the pump 2. The pump 2 comprises a pump housing 3 with an upper inlet 4 and a lower outlet 5, in which pump housing 3a piston or pump piston 6 is guided in a linearly displaceable manner. For this purpose, the piston 6 is driven by means of a drive 7, which is designed, for example, as an electric motor. The pump 2 is connected or can be connected with its pump housing 3 directly to the storage container 1, i.e. the pump housing 3 is assembled with the replaceable storage container 1 as a structural unit. In order to convey lubricant from the inlet 4 to the outlet 5, the piston 6 is raised and lowered cyclically in the piston receptacle 6' by means of the drive 7, i.e. the piston 6 is moved in a first direction toward the reservoir 1 during the raising process and is moved away from the reservoir 1 in a second direction during the lowering process.

The piston 6 is configured in a stepped manner such that it has an upper piston face 10 defining an upper (first) displacement chamber 8 and a lower (second) piston face 11 defining a lower, second displacement chamber 9. The lower piston face 11 is configured with a reduced area compared to the upper piston face 10, i.e. the lower piston face 11 is smaller than the upper piston face 10. The upper displacement chamber 8 adjoins the inlet 4 via a first valve 13, which first valve 13 is configured as a check valve and is loaded into the closed basic position by the force of a valve spring 29. A through-flow opening 12a, which connects the upper displacement chamber 8 with the lower displacement chamber 9 with a second valve 14 connected in between, is integrated in the piston 6 as a piston opening. The second valve 14 is also configured as a check valve with a valve spring 30. The lower displacement chamber 9 merges via an outlet channel 16 into the end-side outlet 5.

As can be seen from a comparative examination of fig. 1a and 1b, when the piston 6 is lowered from its upper end position (fig. 1a), on the one hand the first valve 13 opens against the force of the valve spring 29 by generating a negative pressure in the upper displacement chamber 8 and the lubricant is sucked from the reservoir 1 into the upper displacement chamber 8, and on the other hand the second valve 14 closes and the lubricant is pressed from the lower displacement chamber 9 into the outlet channel 16 in the direction of the outlet 5. Fig. 1a shows the piston 6 in an upper end position, whereas the piston 6 in fig. 1b is in a lower end position. When the piston 6 is raised from the functional position shown in fig. 1b to the functional position shown in fig. 1a, on the one hand the first valve 13 is closed and on the other hand the second valve 14 in the piston is opened, whereby lubricant not only flows from the upper displacement chamber 8 into the lower displacement chamber 9, but lubricant is also pressed (proportionally) from the lower displacement chamber 9 into the outlet channel 16 and thus towards the outlet 5.

Thus, a cylinder chamber or displacement chamber is provided in the pump housing 3, in which the piston 6 is guided, which cylinder chamber or displacement chamber is divided by the piston into an upper displacement chamber 8 on the one hand and a lower displacement chamber 9 on the other hand. According to the invention, lubricant is delivered at each piston movement without an idle stroke or a filling stroke being achieved.

The functional principle can be seen in the enlarged views according to fig. 2a, 2b and 2 c. Fig. 2a shows the functional position according to fig. 1a, in which the piston 6 is in the upper end position. Correspondingly, fig. 2b shows the functional position according to fig. 1b, in which the piston is in the lower end position. Fig. 2c shows the functional position between them, i.e. the piston 6 is in the functional position between the upper end position according to fig. 2a and the lower end position according to fig. 2 b.

The drive 7 is designed as an electric motor, which can be equipped with its own (integrated) gear mechanism. The motor 7 acts on the piston 6 via an (external) gear or screw gear 33, so that the rotary motion of the motor is converted into a linear motion. For this purpose, the thread drive 33 is in the present exemplary embodiment designed as a rotary part or wheel, in which the threaded spindle or spindle 34 engages, to be precise by means of an internal thread or internal toothing provided in the thread drive 33. The piston 6 itself is arranged in a rotationally fixed manner in the housing or in a piston receptacle 6' of the displacement chamber 8, 9. The motor 7 drives the screw transmission mechanism 33 to rotate. Thereby, the lead screw 34 is raised or lowered and thus the piston is raised and lowered. The screw mechanism 33 is rotatably supported in the housing by a bearing 35.

As described above, the piston 6 is guided in the pump housing 3 or the cylinder chambers 8, 9 in a rotationally fixed manner. The stepped piston 6 has a first piston member 6a at an upper portion and a second piston member 6b connected to a lower portion of the first piston member 6a at a lower side. The upper side of the first piston member 6a forms an upper piston face 10. The lower side of the first piston part 6a forms an annular lower piston surface 11. In the exemplary embodiment shown, the piston 6 has a cross section other than circular, for example oval or elliptical, at least in some regions for the non-rotatable arrangement. This in the present exemplary embodiment relates to the upper first piston part 6a (see fig. 6). The upper displacement chamber 8 and/or the lower displacement chamber 9 are therefore not of cylindrical design, but rather have an oval cross section or a slotted or elliptical cross section, so that at the same time an anti-rotation function is achieved. In contrast, the lower second piston part 6b can be of cylindrical design.

A self-priming pump is particularly preferably realized, in which lubricant is supplied from the reservoir 1 without additional force being applied to the lubricant reservoir. This is achieved by minimizing the dead volume, so that a negative pressure is produced without defects during the pumping process. The piston 6 with its upper piston face 10 moves directly against the first valve 13, i.e. its spring-loaded valve element 28, in the upper end position shown in fig. 1a, with a reduced dead volume. In the closed position, this valve element 28 or valve disk 28 is flush with the inner upper stop face 26 of the pump housing 3, i.e. the piston 6 in the upper end position with its upper piston face 10 abuts this upper stop face 26 and the valve element 28 flush with the upper stop face 26, so that only a minimum dead space can be reserved. Thus, as shown in fig. 1a, 1b and 2a to 2c, a complete self-priming pump can be achieved without additional pressure loading and therefore without additional springs or additional pistons or the like in or on the storage container. The storage container 1 is preferably constructed as a self-collapsible container, i.e. the storage container is self-collapsible during emptying by generating a negative pressure, so that the collapsed container remains after emptying as waste product with a minimum residual volume.

For this purpose, fig. 1a, 1b and 2a to 2c show a first embodiment in which the storage container 1 is designed as a bellows or has a bellows 17. The bellows 17 has accordion-like side walls 18 and a container lid 19. On the end of the side wall 18 facing away from the container lid 19, a circumferential flange 19a is provided, by means of which the bellows 17 is connected to a rigid end cap 20 (which forms the container bottom). Such a separate storage container 1 with bellows 17 and end cap 20 is shown in fig. 3. The rigid end cap 20 has a connection opening 21 which is connected to the inlet 4 during connection to the pump. After the storage container 1 has been placed on the pump housing 3, a mechanical connection in the sense of a fastening is made by means of a protective cap 22, which is connected to the pump housing 3 of the pump 2 by means of a screw connection or bayonet connection 23, to be precise with seals 24 and 25 being connected in between.

The design of the side wall 18 of the bellows 17 shown in the drawings is referred to as accordion-like. In principle, such a bellows with accordion-like side walls looks like a stack of parallel disc springs, i.e. the folds are parallel to each other. Such an embodiment is shown in fig. 3 and is also included in the term bellows. In the embodiment of fig. 1a or 8, the accordion-like side wall has a single or multiple spirals. This is intended to make it easier for the folds to lie against one another and, in particular, to prevent the taller container from bending or buckling sideways. Furthermore, the emptying can be improved, since the remaining medium does not easily remain in the folds, but slides down in the spiral-shaped folds to the outlet.

For better understanding, fig. 5 shows the pump 2 without the sleeve storage container 1 and fig. 3 shows the storage container itself without the pump. Finally, fig. 1a, 1b and 2a to 2c show a complete lubricant sprayer with a storage container 1 connected to a pump 2 and a protective cap 22.

It can also be seen in fig. 5 that the housing 3 of the pump 2 has an upper connecting pin 27, in which the first valve 13 is integrated. The connecting pin 27 has a seal 25 on the outer circumference and a seal 24 is also visible on the outer circumference of the housing 3.

Fig. 3 shows an embodiment of the storage container 1 with bellows 17, while fig. 4 shows a modified embodiment of the storage container 1 with a collapsible cup 17 'with a thin-walled container barrel 18'. The collapsible cup 17 'with the thin-walled cylindrical vessel cylinder 18' is in turn connected by means of a flange 19a to a rigid end cap 20, for example by welding or adhesive bonding. During the emptying process, the thin-walled cup 17 'or its cartridge 18' is folded together, so that waste products with a minimum residual volume are also left behind.

It is also shown in fig. 7 that the conversion of the rotary movement into the reciprocating movement can be achieved by means of special threads, similar to trapezoidal threads, by means of the teeth 34a of the threaded rod 34 and the teeth 33a of the screw drive 33 or its nut. Thus, the metal screw 34 can be realized with a reduced load-bearing ratio, but for this purpose the plastic nut 33 can be realized with an increased load-bearing ratio. This makes it possible to achieve increased force absorption in the same installation space. Such special threads are known in principle from the prior art for other fields of application and can be used.

Furthermore, the figures show an embodiment in which, in addition to the first valve 13 and the second valve 14, a third valve 15 is provided, to be precise in or on the outlet or in the outlet channel 16. This third valve is also configured as a check valve and is spring-loaded into its open position counter to the conveying direction. This third valve 15 ensures a faster delivery of the air possibly enclosed by the pump. The negative pressure required for sucking in the medium is established faster. Manual venting as required in the prior art is not performed. Thus, the air delivered through the third valve 15 no longer interferes with the generation of negative pump pressure.

Even if the pump according to the invention is in principle particularly preferably self-priming and can therefore be operated without additional spring force loading of the storage container, it is still possible to optionally additionally load the storage container 1 by means of the spring 36. This variant is shown by way of example in fig. 8. This variant is suitable, for example, for operating at particularly low temperatures or for delivering high-viscosity lubricants.

Fig. 9 shows a modified embodiment of the pump 2, in which the piston 6 is not arranged in the displacement chambers 8, 9 in a rotationally fixed manner, but can be rotated by a screw thread. The rotary movement of the driver 7 thus results in a rotation of the piston and this rotation is directly converted into a reciprocating movement of the piston by means of a threaded coupling. In other respects, however, corresponding components are indicated with the same reference numerals in the modified embodiment, in particular the first valve 13 and the second valve 14.

Fig. 10 shows a variant embodiment of the double-acting pump according to the invention, which has two outlets 5, 5'.

The embodiments according to fig. 1 to 9 show preferred embodiments with only one single outlet 5, i.e. the lubricant sprayer is preferably designed for single-point lubrication. Alternatively, such a lubricant applicator can also be used for multipoint lubrication, for example, a distribution device, not shown, can be connected to the outlet 5, by means of which a plurality of lubrication points can be supplied by means of hoses or the like.

With reference to fig. 1 to 10, an embodiment having a first valve 13 is described, which has a movable valve element 28 on the one hand and a separate valve spring 29 for loading the movable valve element 28 into the closed position on the other hand.

Fig. 11a and 11b show a modified embodiment in which the first valve 13 has an elastic valve element 28 'which at the same time forms a spring 29'. This is therefore a very simple valve, which essentially comprises the spring leaf 28', 29' shown in fig. 11b and which, in its basic position, is loaded into the valve seat according to fig. 11a on the basis of its own spring force, fig. 11a showing the upper connecting pin 27 of the housing 3. Fig. 11b also shows that the resilient valve element 28', which at the same time forms a spring 29', is constructed as a simple rigid sheet metal part 28a, which is provided with an elastomeric sealing surface 28 b. By means of which elastomer sealing surface 28b the element is pressed into a corresponding valve seat of the housing. The design of the first valve 13 shown in fig. 11a, 11b can also be realized in all embodiments according to fig. 1 to 10.

Fig. 12 shows a modified embodiment of second valve 14 or of the throughflow opening of piston 6. While in the embodiment according to fig. 1 to 10 the through-flow opening 12a is integrated as a central through-opening 12b in the piston 6 or the upper piston part 6a, fig. 12 shows a modified embodiment in which the through-flow opening 12b is formed by an annular space 12b surrounding the piston 6 or the upper piston part 6 a. This annular space as the through-flow opening 12b is thus realized by dimensioning the outer circumference of the piston 6 or of the piston part 6a and the inner circumference of the piston receptacle 6' accordingly. During the conveying process, the medium therefore does not flow through the central through-opening of the piston, but flows past the outer circumference of the piston 6 through the described annular space 12 b. In this case, the second valve 14 is formed by an elastic seal 14', which is designed in cross section as a V-seal or V-seal 14', namely such that the medium can flow past the piston in the conveying direction on the outside and the V-seal has a blocking effect in the opposite direction. This embodiment according to fig. 12 can be used in the embodiments described with reference to fig. 1 to 10 and 11a, 11b and can therefore be combined with the solutions described in connection with these figures.