阅读说明：本技术 比例夹管阀 (Proportional pinch valve ) 是由 内尔·巴奇 于 2018-05-30 设计创作，主要内容包括：一种用于控制连续流系统中的流体的压力的比例夹管阀(10),该比例夹管阀包括：砧座(22),该砧座用于夹压连续流系统中的一段管道(12)；以及驱动机构,该驱动机构包括用于使砧座朝向管道(12)移动的移位元件。砧座(22)借助于弹性的弹簧元件(36)间接地联接至移位元件。弹性的弹簧元件(36)至少在管道(12)没有被完全夹紧的情况下为砧座(22)提供限定的游隙(即弹性),使得砧座(22)的移位由弹性的弹簧元件(36)进行力控制。一种利用这种比例夹管阀(10)来控制连续流系统中的流体的压力的方法。(A proportional pinch valve (10) for controlling the pressure of a fluid in a continuous flow system, the proportional pinch valve comprising: an anvil (22) for crimping a length of pipe (12) in a continuous flow system; and a drive mechanism comprising a displacement element for moving the anvil towards the pipe (12). The anvil (22) is indirectly coupled to the displacement element by means of an elastic spring element (36). The resilient spring element (36) provides a defined play (i.e. resilience) to the anvil (22) at least in case the tube (12) is not fully clamped, such that the displacement of the anvil (22) is force controlled by the resilient spring element (36). A method of controlling the pressure of a fluid in a continuous flow system using such a proportional pinch valve (10).)

1. A proportional pinch valve (10) for controlling pressure in a continuous flow system, the proportional pinch valve (10) comprising:

an anvil (22), the anvil (22) for crimping a section of tubing (12) in the continuous flow system, and

a drive mechanism comprising a displacement element for moving the anvil towards the pipe (12),

the anvil (22) is indirectly coupled to the displacement element by means of an elastic spring element (36),

the resilient spring element (36) provides a defined play for the anvil (22) at least in case the tube (12) is not fully clamped, such that a displacement of the anvil (22) is force-controlled by the resilient spring element (36).

2. Proportional pinch valve (10) according to claim 1, characterized in that the spring element (36) is a helical spring.

3. Proportional pinch valve (10) according to claim 1 or 2, characterized in that the displacement element is a lead screw nut (32) arranged on a lead screw (34).

4. Proportional pinch valve (10) according to claims 2 and 3, characterized in that one end of the helical spring is supported on the lead screw nut (32) and the other end of the helical spring is supported on the anvil (22).

5. Proportional pinch valve (10) according to any of the preceding claims, characterized in that the drive mechanism comprises an automatic drive, preferably a stepper motor (40), for displacing the displacement element.

6. Proportional pinch valve (10) according to any of the preceding claims, characterized in that the proportional pinch valve (10) has a support member (16) and a cover plate (18), the support member (16) having one or more receptacles (14), the cover plate (18) cooperating with the support member (16) to hold the tubing (12).

7. Proportional pinch valve (10) according to any of the preceding claims, characterized in that the length of the front surface of the anvil (22) contacting the tubing (12) is greater than 5mm, preferably in the range of 5mm to 10mm, for the diameter of the tubing (12) that is not pinched.

8. Proportional pinch valve (10) according to any of the preceding claims, characterized in that the proportional pinch valve (10) has a ridge (50) protruding from the front surface of the anvil (22) facing the pipe (12).

9. Proportional pinch valve (10) according to claim 8, characterized in that the ridge (50) extends perpendicular to the longitudinal direction of the tube (12).

10. Proportional pinch valve (10) according to any of the preceding claims, characterized in that the proportional pinch valve (10) has a seal, preferably a rubber diaphragm (26), for sealing a free space (28) around the pinched pipe (12) against the drive mechanism.

11. Proportional pinch valve (10) according to any of the preceding claims, characterized in that the proportional pinch valve (10) has a pin (44) coupled to the shifting element, the pin (44) cooperating with a slot (46) disengaged from the shifting element to prevent accidental rotation of the shifting element.

12. Proportional pinch valve (10) according to any of the preceding claims, characterized in that the proportional pinch valve (10) has a position sensor (48) for detecting at least the home position of the shifting element.

13. Proportional pinch valve (10) according to any of the preceding claims, characterized in that the shifting element is displaceable into an end position in which the tubing (12) is fully clamped, in which it is in contact with the anvil (22).

14. Proportional pinch valve (10) according to any of claims 1 to 12, characterized in that the shifting element is displaceable into an end position in which the tubing (12) is fully clamped, in which it is not in contact with the anvil (22).

15. Proportional pinch valve (10) according to any of the preceding claims, characterized in that the proportional pinch valve (10) has a switching mechanism for switching the drive mechanism between a first mode, in which the anvil (22) is directly coupled to the displacement element, and a second mode, in which the anvil (22) is indirectly coupled to the displacement element by means of the spring element (36).

16. A method of controlling the pressure of a fluid in a continuous flow system using a proportional pinch valve (10) according to any of the preceding claims.

17. Method according to claim 16, characterized in that the resilient spring element (36) provides a defined play for the anvil (22) at least in case the tube (12) is not fully clamped, so that the displacement of the anvil (22) is force-controlled by the resilient spring element (36).

18. A method according to claim 17, wherein the pinched surfaces of the tube (12) are urged apart against the bias of the resilient spring element (36) in response to back pressure acting on fluid flowing through the tube (12).

19. The method of any one of claims 16 to 18, wherein the continuous flow system is a cross-flow filtration system.

Technical Field

The invention relates to a proportional pinch valve (proportional pinch valve) for controlling the pressure in continuous flow systems, in particular in cross-flow filtration systems. The invention also relates to a method of controlling the pressure of a fluid in a continuous flow system using a proportional pinch valve.

Background

In accordance with the basic working principle of pinch valves, pinch valves generally employ a member that acts directly on a length of elastic process tubing. Pushing the tubes together will create a seal that is comparable to the permeability (permeability) of the tubes. Pinch valves are commonly used to control the pressure of media in applications where the media needs to be completely isolated from any internal valve parts or traps. Thus, pinch valves are preferred for use in sterile single use systems. While standard proportional valves for controlling pressure are typically designed not to provide a simple disposable flow path, pinch valves allow the use of a clean and very low cost disposable flow path-i.e., the process tube itself. The process piping may be made, for example, of an elastomeric material suitable for gamma sterilization.

However, pinch valves are typically used only for simple on/off flow control. In theory, a small solenoid actuated pinch valve for small pipes might be designed for optimal proportional control, but in practice, the pinch valve is usually designed only as a shut-off valve. It must also be considered that larger pipes and/or higher pressures require higher pinch pressures, and that the solenoid-driven pinch valves thus become large and expensive. Accordingly, larger pinch valves typically use a motor driven lead screw or ball screw to move an anvil to directly pinch the tubing.

An important problem when using pinch valves for proportional control is the fact that small changes in the size of the "pinch" inside the pipe cause large changes in pressure or flow. This means that small movements of the crimp anvil can result in large changes in pressure or flow. This can result in coarse pressure or flow control and/or frequent control point changes during operation. To achieve good control, a slight movement of the anvil of about 1 micron is required, but still does not necessarily result in stable control. Very little motion can be achieved by using a high resolution lead screw and/or other precision mechanism. However, a high resolution lead screw will typically only move at a low linear speed, which can be problematic when a valve needs to be opened or closed quickly.

Disclosure of Invention

It is an object of the present invention to provide a low cost pinch valve that allows stable proportional control of pressure over a wide operating range.

The above problem is solved by a proportional pinch valve according to claim 1. Advantageous and convenient embodiments of the invention are apparent from the dependent claims.

The present invention provides a proportional pinch valve for controlling pressure in a continuous flow system. The proportional pinch valve comprises: an anvil for crimping a length of pipe in a continuous flow system; and a drive mechanism comprising a displacement element for moving the anvil towards the pipe. According to the invention, the anvil is indirectly coupled to the displacement element by means of an elastic spring element. The resilient spring element provides a defined play (i.e. resilience) for the anvil at least in case the tube is not fully clamped, such that the displacement of the anvil is force controlled by the resilient spring element. This means that the anvil is not simply pressed into the pipe by the moving displacement element. According to the invention, the pinching of the tube is controlled exactly by the force applied to the anvil via the spring element interposed between the displacement element and the anvil. The present invention makes use of the following findings: changing from a displacement controlled anvil used in a typical design to a force controlled anvil implemented in the present invention provides significant advantages in pressure control. In a typical design, the pressure control is very sensitive to the displacement caused by the drive mechanism, since the anvil is directly coupled to the displacement element and acts directly on the pipe. This means that the pinching of the pipe is directly proportional to the movement of the displacement element. However, these common designs do not take into account the effects of back pressure caused by the medium flowing through the conduit and its possible variations during operation. For example, if the back pressure increases, the flow through the pinched conduit cannot be increased to offset the increase in pressure. In contrast, in the design according to the invention, the anvil has a defined "play" (i.e. elasticity) when the pipe is pinched, since the pipe is coupled to the elastic spring element. Thus, if the back pressure increases at a given nip pressure, the increased fluid pressure will be able to force the pinched surfaces of the tubing apart, resulting in an increased flow rate. This makes the pressure set point more stable and reduces control sensitivity. In this way, the proportional pinch valve according to the invention also advantageously provides the basic function of a pressure relief valve, which will be discussed further below in connection with the preferred embodiments.

The contemplated application of the present invention is to control the pressure in an ultrafiltration/diafiltration (UF/DF) system, but is not so limited. As already indicated, a basic advantage of the present invention is the stable pressure control over a wide pressure range for a low cost disposable flow path.

According to a preferred embodiment of the proportional pinch valve, the resilient spring element is a helical spring. The coil spring can be easily incorporated in the drive mechanism. Coil springs with appropriate spring rates are generally readily available depending on the application and the force/displacement performance desired. However, a specially configured gas cylinder or suitable elastomeric member may be used in place of the coil spring.

The displacement element used in the drive mechanism is preferably a lead screw nut arranged on the lead screw. The lead screw can be easily rotated by a stepper motor or a handwheel, and the lead screw nut translates this rotational motion into the required linear motion. The lead screw and lead screw nut are well proven linkage components and can be selected according to given requirements.

In the combination of a lead screw and a lead screw nut used in the drive mechanism and a coil spring used as a spring element, one end of the coil spring may be supported on the lead screw nut and the other end of the coil spring may be supported on the anvil to provide the required resilient coupling.

In an automatic version of the proportional pinch valve, the drive mechanism comprises an automatic drive, preferably a stepper motor, for displacing the displacement element. The stepping motor has the following advantages: as long as the motor is carefully sized in terms of torque and speed relative to the application, the position of the motor can be commanded to move and hold in one of a plurality of equal steps without any feedback sensors.

To retain and secure the tubing in the proportional pinch valve, a support member having one or more receptacles and a cover plate cooperating with the support member may be used. The cover plate preferably provides a resting surface against which the pipe is pressed when the anvil is moved towards the pipe.

In conventional pinch valves, the length to be pinched is rather small, i.e. less than 5mm, to minimize the force required to close the valve. However, it has been recognized that the distance by which the elongated conduit is pinched is possible and advantageous compared to previous designs. Thus, the length of the front surface of the anvil contacting the duct is application specific, but preferably in the range of 5mm to 10 mm. For low pressure applications (less than 1bar), longer contact lengths may be required. In addition to improved control performance, the lengthened pinched conduit also reduces the peak shear stress of the liquid passing through the valve compared to conventional (pinch) valve designs, since the pressure drop across the valve occurs over a longer distance.

If a higher pressure differential is required across the proportional pinch valve, the problem is that a large portion of the inner surfaces of the pinched tubing contact each other, with flow only being possible at either edge of the pinched tubing. In these cases, the sensitivity to the pressure in the pipe is significantly reduced. To overcome this problem, a (further) increase in the length of the pinched tube is achieved by providing a ridge projecting from the front surface of the anvil facing the tube. The ridge preferably extends perpendicular to the longitudinal direction of the duct. The purpose of the ridge is to more effectively use the pressure in the duct to act on the anvil and thus on the spring. In particular, the ridges serve to cause most of the pressure drop to occur over a shorter length of the ridges, and thus allow the inner conduit surfaces elsewhere in the nip section to not contact each other. In this way, those tube surfaces are subjected to the pressure within the tube and may thus act on the anvil. The ridge may be located upstream, downstream, mid-way, or any other location along the length of the pipe being pinched, depending on whether it is important to control pressure upstream or downstream. The universal proportional pinch valve will have a ridge located in the middle of the tube being pinched.

According to an advantageous aspect of the invention, a sealing element, preferably a rubber diaphragm, is provided for sealing the free space around the pinched pipe against the drive mechanism. The seal prevents process fluid from entering and contaminating the drive mechanism inside the valve in the event of damage to the pipe being pinched.

According to another advantageous aspect of the invention, the pin coupled to the displacing element cooperates with a slot disengaged from the displacing element to prevent accidental rotation of the displacing element. The slot may be formed in a housing member of the proportional pinch valve in which the displacement element moves.

A position sensor may be provided to detect at least the home position of the displacement element. In order to detect the home position, the pin described above can be used as a position indicating element, thereby giving the pin a dual function.

Regarding the performance of the proportional pinch valve in an end position in which the tubing is fully clamped by the anvil, the present invention provides different concepts as will be explained below.

According to a first design principle, the displacement element is in contact with the anvil when the displacement element is displaced to the end position in which the pipe is fully clamped. Thus, it is possible to apply a high force to the tube and ensure that the anvil remains in its position.

According to a second design principle, the displacement element is not in contact with the anvil when the displacement element is displaced to the end position in which the pipe is fully clamped by the anvil. This design allows the proportional pinch valve to act as a pressure relief valve in the event that the maximum allowable system pressure is exceeded. The maximum pressure may be controlled during operation or by design by setting the maximum displacement of the displacement element to define the end position and thus the maximum force applied by the spring element to the anvil.

According to a more elaborate design, a switching mechanism is provided for switching the drive mechanism between a first mode, in which the anvil is directly coupled to the displacement element, and a second mode, in which the anvil is indirectly coupled to the displacement element by means of a spring element. Depending on the circumstances, a more suitable control, i.e. force-controlled nip or displacement-controlled nip, may be selected as desired.

The present invention also provides a method of controlling the pressure of a fluid in a continuous flow system using a proportional pinch valve as described above. The spring of the proportional pinch valve allows for self-correction of pressure, particularly in the event of back pressure or other conditions where pressure undesirably deviates from a set point.

In particular, according to an important aspect of the invention, the elastic spring element provides a defined play (elasticity) for the anvil at least in case the tube is not fully clamped, such that the displacement of the anvil is force-controlled by the elastic spring element.

Thus, given a clamping pressure acting on the peripheral wall of the conduit, in response to the back pressure of the fluid flowing through the conduit, the clamped surfaces of the conduit may be forced apart against the bias of the resilient spring element, thus causing an increase in flow. This results in higher pressure set point stability and reduced control sensitivity to noise (noise).

The process according to the present invention is preferably used in a cross-flow filtration system but is not limited to a cross-flow filtration system.

Drawings

Other features and advantages of the present invention will become apparent from the following description and the accompanying drawings referred to. In the drawings:

figure 1 shows a proportional pinch valve according to the invention, loaded with a pipe but without a front cover plate;

figure 2 shows a proportional pinch valve loaded with a pipe and a front cover plate;

figure 3 shows in longitudinal section a proportional pinch valve with tubing in a first state;

figure 4 shows in longitudinal section a proportional pinch valve with tubing in a second state;

figure 5 shows in longitudinal section a proportional pinch valve with tubing in a third state; and

figure 6 shows, in longitudinal section, a variant of the proportional pinch valve loaded with tubing in a second state, in which the anvil has ridges.

Detailed Description

Referring to fig. 1 and 2, a proportional pinch valve 10 is shown for controlling the pressure of a medium flowing through a flexible tubing 12, the flexible tubing 12 being made of, for example, a soft elastomeric material. In a preferred application, conduit 12 is a single-use component or system, such as a disposable conduit of a UF/DF cross-flow filtration system.

The conduit 12 is received in an opposed sump 14, the sump 14 being formed on a front side of an annular support member 16. After loading the tubes 12, a front cover plate 18 is secured to the front side of the support member 16 by screws 20 or other suitable attachment means, as shown in fig. 2. The sump 14 is covered by a front cover plate 18, and thus the pipe 12 is fixed in the axial direction and the radial direction.

The section of the conduit 12 between the opposing sumps 14 is exposed to the anvil 22. In particular, the anvil 22 faces the following sides of the duct 12: opposite the side of the duct 12 that abuts the front cover plate 18. In fig. 3 to 5, the anvil 22 can be seen, and fig. 3 to 5 show the proportional pinch valve 10 in longitudinal section.

The anvil 22 is radially supported in the housing member 24 so as to be axially movable toward and away from the exposed section of the pipe 12. The front surface of the anvil 22 facing the pipe 12 has such dimensions that: this dimension is such that the length of the tube 12 that can be contacted by the anvil 22 is application specific, but is preferably in the range of 5mm to 10 mm. For low pressure applications (less than 1bar), longer contact lengths may be required.

A disc-shaped rubber diaphragm 26 is provided to seal a free space 28 of the support member 16, in which free space 28 the tube 12 emerges from an inner sliding surface of the proportional pinch valve 10, in particular a peripheral surface portion of the anvil 22 engaging with an inner peripheral surface of the housing member 24. The outer periphery of the partition 26 is sandwiched between the front end portion of the housing member 24 and the opposite surface of the support member 16. The inner periphery of the spacer 26 is received in a circumferential groove 30 of the anvil 22.

The anvil 22 is indirectly coupled to the displacement element. In the preferred embodiment shown in the figures, the displacement member is a lead screw nut 32, the lead screw nut 32 being arranged on a lead screw 34. More specifically, the anvil 22 is indirectly coupled to the lead screw nut 32 by means of an interposed resilient spring element 36.

The spring element 36 here is a helical spring. One end of the coil spring rests on a ledge 38 and is supported by an adjacent shoulder, the ledge 38 being located at the end of the lead screw nut 32 facing the rear side of the anvil 22. The other end of the coil spring is supported by a flange of the anvil 22.

However, instead of a coil spring, for example, a cylinder or an elastomer member may also be employed as the spring element 36.

The lead screw 34 is driven by a stepper motor 40 coupled to an electronic controller (not shown). In principle, the lead screw 34 may also be driven manually by a hand wheel or the like.

A lead screw 34 and a lead screw nut 32 are housed in the housing member 24 of the proportional pinch valve 10. A thrust bearing 42 rests on the stepper motor housing and surrounds the lead screw 34, the thrust bearing 42 being capable of supporting the axial load of the lead screw nut 32.

A radially extending pin 44 is secured to the lead screw nut 32. The pin 44 engages a slot 46 formed in the housing member 24 and extending in the axial direction. The pin 44 extends through the slot 46 and prevents inadvertent rotation of the lead screw nut 32.

In addition, the pin 44 has other functions. A position sensor 48 disposed on the housing member 24 is capable of detecting the home position of the pin 44.

The original position of pin 44 corresponds to the first condition of proportional pinch valve 10 shown in figure 3, in which anvil 22 is in a position that does not interfere with tubing 12. In the home position, the spring element 36 is substantially relaxed, which means that the anvil 22 does not exert much pressure or pressure at all on the pipe 12. Thus, the pipe 12 is not pinched, and the flow of the medium through the pipe 12 is not restricted.

Figure 4 shows the proportional pinch valve 10 in a second state in which the tubing 12 is pinched. The stepper motor 40 has driven the lead screw 34 such that the lead screw nut 32 has moved a distance axially toward the tube 12. The anvil 22 is thus pressed into the pipe 12 to such an extent that the effective flow cross section of the pipe 12 is reduced. However, the flow is not completely blocked.

It should be recalled here that the anvil 22 is not directly coupled to the lead screw nut 32, but is directly coupled to the spring element 36. Thus, the pinching of the tubing 12 is not simply proportional to the displacement of the lead screw nut 32, but is controlled by the force indirectly transmitted from the lead screw nut 32 to the anvil 22 via the spring element 36. Since the spring element 36 is resilient, the reaction force of the tube 12 acting on the anvil 22 may cause compression of the spring element 36 to a certain extent. As a result, the force applied to the anvil 22 by the spring element 36 is balanced by the average pressure inside the tube 12 (plus the force deforming the tube 12).

The spring member 36 is selected such that significant movement of the lead screw 34 is required to produce the change in force necessary to crimp the tubing 12. For example, the spring element 36 may be selected such that the lead screw movement to pressure change ratio is at least 10 times higher than a pinch valve design without a spring element (e.g., if the lead screw nut would directly displace the anvil). Thus, the use of the spring element 36 allows fine tuning of the resultant force acting on the pipe 12, so that the pinch pressure of the pipe 12 can be accurately adjusted.

The use of spring element 36 in a proportional pinch valve design may also make the pressure set point more stable. For example, if the upstream pressure is controlled (as in the case of UF/DF), an increase in the upstream pressure may cause an increase in the reaction force on the anvil 22. This in turn further compresses the spring element 36, which allows the anvil 22 to slightly decompress the tube 12. This depressurization of the conduit 12 returns the pressure to the target set point.

Furthermore, as the length of tubing 12 that is pinched by anvil 22 is increased (compared to conventional pinch valves), proportional pinch valve 10 is made more sensitive to the pressure inside tubing 12, which increases sensitivity and resolution of pressure control.

In fig. 5, the proportional pinch valve 10 is shown in a third state in which the anvil 22 is displaced to a maximum extent. The pipe 12 is completely clamped and the flow of the medium is interrupted.

According to a first design principle, as shown in fig. 5, the third state of the proportional pinch valve 10 is characterized in that the projection 38 of the lead screw nut 32 contacts the rear side of the anvil 22, so that the spring element 36 no longer has any influence on the displacement of the anvil 22. This design provides a high safety of flow interrupted by the pinch pressure regardless of the pressure in the pipe 12 or the stiffness of the pipe 12.

According to a second design principle, not shown in the figures, the third state of the proportional pinch valve 10, in which the tubing 12 is completely clamped, i.e. without the projection 38 of the lead screw nut 32 in contact with the rear side of the anvil 22, is achieved solely by the force of the spring element 36. Since according to this design the spring element 36 still allows a defined "play" (i.e. elasticity) of the anvil 22 in a direction away from the pipe 12, the proportional pinch valve 10 may be used as a pressure relief valve. For example, if the maximum operating pressure of the filtration system using the conduit 12 is 3bar, then, depending on the design, when the lead screw nut 32 is fully displaced (but not in contact with the anvil 22), the force exerted by the anvil 22 on the conduit 12 via the spring element 36 is such that the media will be allowed to pass with a pressure in the conduit 12 higher than 6 bar. This provides greater safety without the need to add a separate pressure relief valve.

According to a third design principle, which is not shown in the figures, the proportional pinch valve 10 can utilize both the first and the second design principle. A conversion mechanism is provided for converting between a pure displacement control mode, in which the anvil 22 is directly coupled to the lead screw nut 32, and a force control mode, in which the anvil 22 is indirectly coupled to the lead screw nut 32 via a spring element 36. The conversion mechanism may employ, for example, a power actuated latch/coupler configured to directly couple the lead screw nut 32 and anvil 22 together, or alternatively, may employ a passive "click" type mechanism configured to directly transfer force between the lead screw nut 32 and anvil 22.

Figure 6 shows a variation of the proportional pinch valve 10 in which the front surface of the anvil 22 has a different shape. In particular, a ridge 50 is provided that extends perpendicular to the loaded pipe 12, the ridge 50 having a smaller height. The purpose of the ridge 50 is to more effectively utilize the pressure in the conduit 12 to act on the anvil 22 and thus on the spring element 36.

The ridge 50 is useful in situations where a high pressure differential is required across the proportional pinch valve 10. The problem in these cases is that in the pinched state of the pipe 12, most of the inner surfaces of the pipe 12 contact each other. Thus, there may be a flow of medium only at either edge of the pipe 12 being pinched. In these cases, the sensitivity to the pressure in the pipe 12 is significantly reduced. This problem is overcome by the ridge 50, as the ridge 50 further increases the already extended length of the pinched conduit 12. Due to the ridge 50, most of the pressure drop is over a short length of the ridge 50. Thus, it is allowed that the surfaces of the inner conduits elsewhere in the nip section do not contact each other. In this way, the non-contacting pipe surface is subjected to the pressure within the pipe 12 and is thus able to act on the anvil 22.

The ridge 50 may be located upstream, downstream, mid-way or any other location along the length of the pipe section to be pinched. The location of the land 50 may be selected depending on whether the upstream or downstream control pressure is important. For example, if the upstream pressure is to be controlled, a ridge on the downstream side of the pinched conduit will be used. The universal valve will have a ridge located in the middle of the pipe being pinched.

In the event of a leak in the pipe 12, the diaphragm 26 prevents the process fluid from contaminating the valve components inside the housing member 24, as the diaphragm 26 isolates the area where the pipe 12 is pinched from the internal sliding surfaces of the proportional pinch valve 10.

List of reference numerals

10 proportion pinch valve

12 pipeline

14 storage tank

16 support member

18 front cover plate

20 screw

22 anvil

24 housing member

26 baffle plate

28 free space

30 groove

32 lead screw nut

34 lead screw

36 spring element

38 projection

40 stepping motor

42 thrust bearing

44 pin

46 slot

48 position sensor

50 ridge