阅读说明：本技术 用于机床的c轴单元和包括c轴单元的机床
(C-axis unit for machine tool and machine tool including the same
) 是由 克劳迪奥·乌戈·普罗塔索·雷波西尼
朱塞佩·莫尔菲诺 于 2019-09-12 设计创作，主要内容包括：本发明提供了用于机床的C轴单元和包括C轴单元的机床。一种用于机床的C轴单元,包括：衬套(134),适于固定到机床的单元支撑件(121)；头部安装平台(130),适于接收操作头部(40),所述头部安装平台由衬套(134)支撑并且能够绕竖直轴线相对于衬套(134)旋转；平台旋转马达(150),由衬套(134)支撑,并被配置为控制头部安装平台(130)的旋转；以及主轴马达(160),被配置为通过在穿过头部安装平台(130)获得的通孔(133)中布置的驱动延伸件(163)来控制在操作头部(40)上的工具承载主轴(45)的旋转。主轴马达(160)固定到头部安装平台(130)并与头部安装平台旋转地成一体。(The invention provides a C-axis unit for a machine tool and a machine tool including the C-axis unit. A C-axis unit for a machine tool, comprising: a bushing (134) adapted to be fixed to a unit support (121) of a machine tool; a head mounting platform (130) adapted to receive the operating head (40), the head mounting platform being supported by the bushing (134) and being rotatable relative to the bushing (134) about a vertical axis; a platform rotation motor (150) supported by the bushing (134) and configured to control rotation of the head mounting platform (130); and a spindle motor (160) configured to control rotation of the tool carrying spindle (45) on the operating head (40) by means of a drive extension (163) arranged in a through hole (133) obtained through the head mounting platform (130). A spindle motor (160) is fixed to and rotationally integral with the head mounting platform (130).)
1. A C-axis unit for a machine tool, comprising:
a bushing (134) adapted to be fixed to a unit support (121) of a machine tool at a lower end of said unit support (121), said bushing extending along a vertical axis (Z) when said bushing is fixed to said unit support (121) of said machine tool,
a head mounting platform (130) adapted to receive an operating head (40), the head mounting platform being supported by the bushing (134) and rotatable relative to the bushing (134) about the vertical axis, and
a platform rotation motor (150) supported by the bushing (134) and configured to control rotation of the head mounting platform (130),
characterized in that the C-axis unit further comprises:
a spindle motor (160) configured to control rotation of a tool carrying spindle (45) on the operating head (40) by means of a drive extension (163) arranged in a through hole (133) obtained through the head mounting platform (130), wherein the spindle motor (160) is fixed to the head mounting platform (130) and is rotationally integral with the head mounting platform (130).
2. A machine tool, comprising:
a unit support (121) movable in translation along at least one axis, at the lower end of which is mounted a C-axis unit according to claim 1, and
a fluid rotary joint (173, 174) provided for supplying at least one fluid to the operating head (40), the fluid rotary joint being arranged at an upper end of the unit support (121) and comprising a stationary part (173) fixed to the unit support (121) and a rotary part (174) rotatable about the vertical axis relative to the bushing (134).
3. The machine tool of claim 2, wherein the rotary part (174) of the fluid rotary joint is controllably rotated by a joint motor (191) arranged on the unit support (121) and separate from the platform rotary motor (150), the joint motor (191) and the platform rotary motor (150) being controllable to synchronize the angular position and rotational speed of the rotary part (174) of the fluid rotary joint with the angular position and rotational speed of the head mounted platform (130).
4. Machine tool according to claim 2 or 3, comprising a plurality of power and signal cables (181) for powering and controlling at least one of the spindle motor (160) and the operating head (40), said power and signal cables being conveyed from the outside of the unit support (121) through cable-carrying members (182) located above the spindle motor (160) and arranged radially on the vertical axis (Z), the upper ends of which are fixed to the unit support (121) and the lower ends of which are rotationally integral with the rotating portion (174) of the fluid swivel.
5. A machine tool according to claim 2 or 3, comprising a plurality of power and signal cables (181) for powering and controlling at least one of the spindle motor (160) and the operating head (40), and further comprising a slip ring arranged at the upper end of the unit support (121) and comprising a stationary part (201) fixed to the unit support (121) and a rotating part (202) rotationally integral with the rotating part (174) of the fluid rotary joint, the rotating part (202) of the slip ring being electrically connected to at least one of the spindle motor (160) and the operating head (40).
Technical Field
The present invention relates generally to the field of machine tools for machining by chip removal, and in particular to high speed cutting machines (HSCs).
Background
The strong and continuous development of HSC technology requires machine tools with high dynamic performance of the feed shaft and tool carrying spindle.
In the field of 5-axis engraving, i.e. in moulding, aeronautics, energy fields, moulding centre models, etc., the demand for 5-axis machines with high dynamic performance of linear and polar axes is becoming more and more intense and severe.
Other strong demands from the field are to reduce the tooling costs and to use multitasking machines that can be modular and reconfigurable, i.e. to meet the complex and definite problems of the tooling process.
Given the requirements deriving from the machining process, which laterally influence the specifications of the machine, key problems have been defined that characterize the current state of the art of 5-axis machines.
Some of these involve the need to configure 5-axis machines (3 linear and 2 polar) to be able to perform coarse and fine operations with operating heads that are consistent with the current state of the art in HSC technology.
The configurability and modularity of the machining system are also strongly restricted by the conformation of the polar axis C, which must be able to allow automatic coupling of a series of powerful, fast and reliable operating heads.
With reference to fig. 1 to 3b, a known machine tool is described for this purpose, wherein only the parts relating to the movement according to the polar axis C are shown in fig. 1 to 3 b. In a 5-axis machine, the three linear axes are generally denoted by X, Y and Z, while the two polar axes of rotation about the horizontal axis X and about the vertical axis Z are denoted by A and C, respectively. In the figure, the axis Y, not shown, is perpendicular to the drawing plane (the axes X and Y may be reversed).
The machine tool comprises a bearing structure 10 and a unit support 21, the bearing structure 10 being shown simply in fig. 1, the unit support 21 being supported by the bearing structure 10 and being movable in translation along at least one axis, and in particular along two horizontal orthogonal axes X and Y and along a vertical axis Z, with respect to the bearing structure 10 in a manner known per se.
In the example shown, the unit support 21 is made as a ram (ram) extending along a vertical axis Z and will be indicated as such hereinafter for the sake of simplicity. The ram 21 is connected to the bearing structure 10 of the machine tool in a manner known per se.
The C-axis unit 20 is disposed on the ram 21 at a lower end of the ram.
The C-axis unit comprises a head mounting platform 30 adapted to receive an operating head 40. The head mounted platform 30 is rotatable relative to the ram 21 about a vertical axis Z and thus in the direction of the polar axis C. The head mounting platform 30 comprises a body 31 and a shaft 32, the body 31 being intended to fix the operating head 40, the shaft 32 extending coaxially with the axis Z. The shaft 32 is made in one piece with the body 31 and, as will be explained below, constitutes the rotating part of the rotary joint. A central through hole 33 is obtained through the head mounting platform 30, the purpose of which will be clarified below. A series of washers 33a are arranged along the central through hole 33.
The head mounting platform 30 is supported by a bushing (bushing)34 fixed to the bottom of the ram 21. Specifically, the head mounting platform 30 is supported by the bushing 34 through a radial axial bearing 35 and a roller bearing 36. Further interposed between the head mounting platform 30 and the bushing 34 is a multi-plate clutch 34a, which can be activated 34a when it is desired to lock the head mounting platform 30 relative to the bushing 34/ram 21.
On the lower surface 31a of the main body 31 of the head mounting platform 30 there are arranged electrical connectors 37 and hydraulic connectors 38 adapted to supply electrical power, signals and fluid users on the operating head 40. Also arranged in the lower part of the main body 31 of the head mounting platform 30 is a head coupling system 39, which head coupling system 39 may be manual or automatic (visible in enlarged detail in fig. 3 b). These head coupling systems 39 also comprise a lock with a geared front connector 39a of the Hirth type, which front connector 39a can be activated to provide greater rigidity and mechanical stability to the connection between the head mounting platform 30 and the operating head 40.
The operating head 40 is fixed (manually, semi-automatically or automatically) to the head mounting platform 30 in such a way as to be also rotatable about the vertical axis Z. In the example shown, the operating head 40 is configured in such a way that the portion 41 can rotate about a horizontal axis X with respect to the operating head 40, thus rotating according to the direction of the polar axis a. On the portion 41 of the operating head 40, a tool carrying spindle 45 is arranged for attaching a tool (not shown). The head 40 may be removed and replaced with a head having a different architecture.
A workpiece carrying unit is disposed below the operation head 40 to support the workpiece.
The C-axis unit further includes a platform rotation motor 50, the platform rotation motor 50 being configured to control rotation of the head mount platform 30. The platform rotation motor 50 may consist of, for example, a torque motor, a worm/helical gear motor, or a preloaded electric double motor. The platform rotation motor 50 includes a radially outer stator portion 51 fixed to the bushing 34, and a radially inner rotor portion 52 fixed to the shaft 32 of the head mounting platform 30.
The spindle motor 60 is arranged on the ram 21 at its upper part together with a gear box 61 associated with the spindle motor 60. The spindle motor 60 is configured to control the rotation of the tool carrying spindle 45 on the operating head 40. For this purpose, a drive shaft 62 and drive extension 63 are provided to transmit power to the head mounting platform 30. The upper end of the drive shaft 62 is connected to the output shaft of the gear box 61 by an upper drive coupling 64, while the lower end of the drive shaft 62 is rotationally integral with the drive extension 63 by a lower drive coupling 65. The drive extension 63 is connected to the head mounting platform 30 by a bearing 66.
The drive extension 63 may be connected to a kinematic chain inside the operating head 40 or to the main shaft 45 by a splined or grooved shaft 67-68. The coupling is constructed in two parts to ensure that the operating head 40 is separated from the head mounting platform 30. The female part of the coupling 67 is integral with the drive extension 63, while the male part of the coupling 68 is mounted on the input shaft of the operating head 40.
The fluid user on the operating head 40 is supplied through a conduit 71, the conduit 71 connecting a dedicated hydraulic control unit of the machine tool (not shown) to a hydraulic distributor 72 fixed to the diaphragm (horizontal rib) of the ram 21. The body of the hydraulic distributor 72 also serves as a support for the motor/ gearbox units 60, 61.
A fluid rotary joint is interposed between the hydraulic distributor 72 and the user on the operating head 40, which comprises a stationary part 73 (stationary with respect to the ram 21) and a rotating part. The rotating portion is comprised of the shaft 32 of the head mounting platform 30. The stationary portion 73 of the swivel is inserted into the central through hole 33 of the head mounting platform 30. The anti-rotation constraint of the stationary part 73 of the rotary joint is obtained by means of a support 74 (connected to the stationary part 73 of the rotary joint), which support 74 is connected by means of a tube 75 to the body of the hydraulic distributor 72, which body of the hydraulic distributor 72 is fixed to the diaphragm (horizontal rib) of the ram 21. The drive shaft 62 is received within the tube 75.
The stationary part 73 of the rotary joint is supplied with fluid via a conduit 76, the conduit 76 connecting the hydraulic distributor 72 to the support 74 and then to the stationary part 73 of the rotary joint.
Fluid is supplied to the head mounting platform 30 and the hydraulic connector 38 through a fluid supply hole 73a and a washer 33a made in the stationary portion 73 of the rotary joint.
The power and signal users on the operating head 40 are powered by power and signal cables that connect the electrical and digital control cabinet of the machine tool (not shown) to power and signal connectors 81, these power and signal connectors 81 being fixed in a stationary part to the body of the distributor 72.
The supply of electric power to the head mounting platform 30 and therefore to the electric connectors 37 is provided by means of cables 82, these cables 82 being wound according to a helical trajectory that joins the electric connector 81 of the distributor 72 to an electric connector 83 arranged integrally with the shaft 32 of the head mounting platform 30. These electrical connectors 83 are in turn electrically connected to electrical connectors 37 disposed on surface 31a of head mounting platform 30.
To avoid collision and breakage between the cable 82 moving along a helical path and the fixed, non-rotating conduit 76, a tube 84 having a smooth and lubricated outer surface is employed which rotates with the head mounting platform 30 and allows separation between the cable and the hydraulic conduit.
The above-described machine has several key problems.
First, the spindle motor 60 mounted on the ram 21 makes it difficult to arrange electric and signal cables for operating the head, the architecture of the hydraulic swivel, and the layout of the hydraulic pipes at its upper end.
Further, in operation, power and signal cables82 are twisted and bent in a helical fashion, limiting the angular travel of the head to +/-180 deg. on the one hand, and causing significant cable wear on the other hand, which requires frequent maintenance. The complex management of the cable wires 82 further limits the dynamic performance of the C-axis, compromising HSC processing. Typically, a processing speed of 5rpm and 0.1rad/sec can be achieved2The angular acceleration of (a).
Furthermore, the morphology of the system does not allow the use of slip rings that allow infinite machining (continuous rotation of the polar axis), a particular feature that is strongly required, for example, in the field of aeronautics.
The position of the upper part of the gearbox/ spindle motor unit 61, 60 is mandatory and depending on the length of the drive shaft 62, the drive shaft 62 must be high to allow a sufficient length of cable 82 to reduce bending and twisting of the same cable to ensure an acceptable lifetime thereof. The long propeller shaft 62 has a severe negative effect on its torsional stiffness, limiting heavy rough operations requiring high torque. Moreover, due to the length of the drive shaft 62, the high speed finishing of the machine spindle 45 is severely limited, which limits the critical rotational speed.
The lower hydraulic swivel formed by portions 73 and 32 is integrated into the head mounting platform 30. Supplying the multiple washers 33a required by the user operating the head generates a high friction torque that creates a torque disturbance to the rotary platform motor 50.
These critical issues described above severely limit the dynamic performance of the C-axis and the motor drive that operates the spindle of the head. Furthermore, the assembly of the various units is complex and the construction of the components does not comply with the most modern guidelines for modular and reconfigurable systems.
Disclosure of Invention
The object of the present invention is to provide a machine tool which allows to overcome at least partially the drawbacks of the above-mentioned machines according to the prior art.
According to the invention, this and other objects are achieved by a C-axis unit for a machine tool, comprising:
a bushing adapted to be fixed to a unit support of a machine tool at a lower end thereof, said bushing extending along a vertical axis when fixed to the unit support of the machine tool,
a head mounting platform adapted to receive an operating head, the head mounting platform being supported by the bushing and rotatable relative to the bushing about the vertical axis, an
A platform rotation motor supported by the bushing and configured to control rotation of the head mount platform, the C-axis unit characterized by further comprising:
a spindle motor configured to control rotation of a tool-carrying spindle operating the head by means of a drive extension arranged in a through hole obtained through the head mounting platform, wherein the spindle motor is fixed to and rotationally integral with the head mounting platform.
The spindle motors are no longer integrally fixed to the structure of the ram and do not interfere with the passage of the power and signal cables, thereby making assembly easier and extending the service life of the cable wires, as they no longer need to be arranged in such a way as to undergo bending and twisting during operation.
The electric cables rotating integrally with the head mounting platform are no longer wound in a spiral manner as is done in the known practice, but can be conveyed in a commercial cable-carrying chain (cable-carrying chain) suitable for being reliably implemented without twisting and bending the cables, the angular travel of rotation of the head mounting platform increases considerably to +/-360 °, and the dynamic performance of the C-axis increases significantly, such as an angular speed of 30rpm and 30rad/sec2The angular acceleration of (a).
The application of the spindle motor on the head mounting platform is also an important simplification of the location of the hydraulic head piping and makes the upper part of the ram available, making it suitable for fluid swivel joints driven by a dedicated kinematic chain. The swivel is decoupled from the head mounting platform, eliminating the friction of the washer, with a significant positive impact on the C-axis positioning and machining accuracy and the power available to operate the head.
The position of the top of the rotary joint allows to replace the cable carrying chain with a possible slip ring (slip ring) which allows an infinite rotation of the C-axis.
The application of a spindle motor directly fixed on the head mounting platform allows a significant simplification of the assembly of the kinematic chain and an extraordinary increase of the dynamic performance of the kinematic chain of the spindle rotation.
In fact, since long transmission rods are eliminated, which are the source of significant torsional faults, a significant increase in torsional stiffness and kinematic chain frequency is obtained, allowing machining with high chip removal, eliminating the onset of chatter, and achieving an increase in the operating head rotational speed.
The advantages of the invention make it possible to achieve a significant increase in the dynamic performance of the head mounted platform, for example a shaft rotation speed of 30rpm and 30rad/sec2The angular acceleration and the dynamic performance of the spindle rotational kinematics chain are significantly increased by 20%.
Drawings
Other features and advantages of the present invention will become apparent from the following detailed description, which is provided by way of non-limiting example only, with reference to the accompanying drawings, in which:
fig. 1 shows a C-axis unit of a machine tool according to the prior art, shown in cross-section;
FIGS. 2 and 3a are enlarged views of a portion of the C-axis unit of FIG. 1, indicated at II and III, respectively, of FIG. 1;
FIG. 3b is a view of the C-axis unit of FIG. 1 on a partially enlarged scale;
FIG. 4 shows a C-axis unit for a machine tool, in cross-section, according to an embodiment of the invention;
fig. 5 to 7 are views on an enlarged scale of a portion of the C-axis unit of fig. 4, as indicated at V, VI and VII respectively;
FIG. 8 shows a C-axis unit for a machine tool according to another embodiment of the invention, shown in cross-section; and
fig. 9 to 11 are partially enlarged scale views of the C-axis unit in fig. 8, as shown in IX, X and XI, respectively.
Detailed Description
Referring to fig. 4 to 7, a machine tool including a C-axis unit according to the present invention will now be described. Only the parts related to the movement according to the polar axis C are shown in fig. 4 to 6. Traditionally, the two linear axes are denoted X and Y, while the two polar axes rotate about a horizontal axis X and about a vertical axis Z, designated a and C, respectively. In these figures, the axis Y, not shown, is perpendicular to the plane of the drawing (the axes X and Y may be reversed). However, for the purposes of the present invention, it is not necessary that the machine tool have 5 axes of motion.
The machine tool comprises a bearing structure 10 and a unit support 121, the bearing structure 10 being shown simply in fig. 4, the unit support 121 being supported by the bearing structure 10 and being movable in a manner known per se along at least one axis, and in particular along two horizontal orthogonal axes X and Y and along a vertical axis Z, with respect to the bearing structure 10.
In the example shown, the unit support 121 is formed as a ram extending along the vertical axis Z, and will be denoted as a ram hereinafter for simplicity. The ram 121 is connected to the bearing structure 10 of the machine tool in a manner known per se.
The C-axis unit 120 is disposed on the ram 121 at a lower end thereof.
The C-axis unit includes a head mounting platform 130 adapted to receive the operating head 40. The head mounted platform 130 is rotatable relative to the ram 121 about a vertical axis Z and thus in the direction of the pole axis C. The head mounting platform 130 comprises a body 131 and a shaft 132, the body 131 being used for fixing the operating head 40, the shaft 132 extending coaxially with the axis Z. The shaft 132 is integrally formed with the body 131. A central through hole 133 is obtained through the head mounting platform 130, the purpose of which will be clarified below.
The head mounted platform 130 is supported by a bushing 134 secured to the bottom of the ram 121. Specifically, the head mounting platform 130 is supported by the bushing 134 via a radial-axial bearing 135 and a roller bearing 136. Between the head mounted platform 130 and the bushing 134, there is also inserted a multi-plate clutch 134a, which can be activated when it is desired to lock the head mounted platform 130 relative to the bushing 134/ram 121.
Disposed on the lower surface 131a of the body 131 of the head mounting platform 130 are a plurality of electrical connectors 137 and a plurality of hydraulic connectors 138 adapted to supply electrical power, signals and fluid users on the operating head 40. Also arranged in the lower part of the body 131 of the head mounting platform 130 are head coupling systems, which may be manual or automatic, for example similar to those shown in fig. 3 b.
The operating head 40 is fixed (manually, semi-automatically or automatically) to the head mounting platform 130 so as to be also rotatable about the vertical axis Z. In the example shown, the operating head 40 is configured in such a way as to have a portion 41 rotatable with respect to the operating head 40 about a horizontal axis X and therefore according to the direction of the polar axis a. On the part 41 of the operating head 40, a tool carrying spindle 45 is arranged for attaching a tool (not shown). The head 40 may be removed and replaced with a head having a different architecture. The configuration of the operating head 40 is not essential for the purposes of the present invention.
A workpiece carrying unit is disposed below the operation head 40 to support the workpiece.
The C-axis unit further includes a platform rotation motor 150, the platform rotation motor 150 configured to control rotation of the head mount platform 130. Platform rotation motor 150 may be comprised of, for example, a torque motor, a worm/helical gear motor, or a pre-loaded electric dual motor. The platform rotation motor 150 includes a radially outer stator portion 151 secured to the bushing 134, and a radially inner rotor portion 152 secured to the shaft 132 of the head mounting platform 130.
The C-axis unit also includes a spindle motor 160, the spindle motor 160 being secured to the head mounting platform 130 by a motor support, which is made up of two parts secured to each other and shown in the figures at 161 and 160 a. Thus, spindle motor 160 is connected to shaft 132 of head mount platform 130 and is thus rotationally integral with head mount platform 130.
A gearbox, such as a planetary gearbox, may be associated with spindle motor 160.
The spindle motor 160 is configured to control the rotation of the tool carrying spindle 45 on the operating head 40. To this end, a drive extension 163 is provided to transmit power to the head mounting platform 130. The upper end of the driving extension 163 is connected to the output shaft of the spindle motor 160 through the upper transmission coupling 164, and the lower end of the driving extension 163 is inserted into the central through-hole 133 of the head mounting platform 130 and is connected to the head mounting platform 130 through the bearing 166.
The drive extension 163 may be connected to the kinematic chain and spindle 45 inside the operating head 40 by a keyway connection or slotted shaft 167 and 168. The coupling is constructed in two parts to ensure that the operating head 40 is separated from the head mounting platform 130. The female portion of the coupler 167 is attached to the drive extension 163, while the male portion of the coupler 168 is mounted on the input shaft of the operating head 40.
The fluid user on the operating head 40 is supplied through a conduit 171, the conduit 171 connecting a dedicated hydraulic control unit of the machine tool (not shown) to a hydraulic distributor 172. The hydraulic distributor 172 is mounted on the stationary part 173 of the hydraulic swivel, the stationary part 173 in turn being fixed to the diaphragm (horizontal rib) of the ram 121.
The fluid rotary joint includes a rotary portion 174 inserted into a bore in a stationary portion 173. A series of washers 174a are inserted between the stationary part 173 and the rotating part 174 of the rotary joint, and these washers 174a are placed along the holes that receive the rotating part 174.
The rotary portion 174 of the rotary joint is supplied with fluid through a fluid supply hole 173a and a washer 174a formed in the stationary portion 173 of the rotary joint. The fluid is supplied to the motor supporter 160a through a fluid supply hole 174b formed in the rotary portion 174 of the rotary joint and connected to a pipe 175, the pipe 175 being connected to the rotary portion 174 of the rotary joint at one side and the motor supporter 160a at the other side. The head mounting platform 130 and the hydraulic connector 138 are supplied through fluid supply holes 160b made in the motor support 160a, which connect to corresponding supply holes 130b made in the head mounting platform 130.
The power and signal users on the operating head 40 are supplied by power and signal cables 181, the power and signal cables 181 connecting the electrical and digital control cabinet of the machine tool (not shown) to the C-axis unit. The cable 181 is anchored to a plate 181a, which plate 181a is in turn secured to an input support 181 b. The input support 181b is attached to the distributor 172 and to the stationary part 173 of the rotary joint. The top end of cable carrier chain 182 is fixed to plate 181a and is disposed within a central through hole in swivel portion 174 of the swivel. Thus, cables 181 from plate 181a are routed within cable carrier chain 182. The lower end of the cable carrying chain 182 is fixed to a support 183, the support 183 is fixed to the motor support 160a by a number of posts 184, and the motor support 160a rotates with the head mounting platform 130. Thus, the cable 181 is electrically connected in part to the spindle motor 160 and in part to some of the electrical connectors 137 disposed on the bottom surface 131a of the head mounting platform 130. Of course, there are also power and signal cables connected to stationary users, for example to the stator of a rotary platform motor, but these cables are not shown as they are not connection parts that are rotatable relative to each other, which are not of interest for the purposes of the present invention.
To eliminate torque disturbances to the platform rotation motor 150 due to friction of the washer 174a, the hydraulic rotation joint 173 and 174 is rotationally controlled by a dedicated kinematic chain 190 and motor 191. The synchronization of the rotation of the hydraulic swivel 173 and 174 with the rotation of the platform rotation motor 150 is achieved by two measurement systems integrated in the motors 150 and 191 and a numerical control (CNC) control algorithm.
The C-axis unit in the above configuration is capable of +/-360 deg. rotation from the C-axis with limited twist of the cable 181 disposed at the axis of rotation of the head mounting platform 30 in the cable carrier chain 182.
Referring to fig. 8 to 11, a machine tool including a C-axis unit according to a second embodiment of the present invention will now be described. Elements corresponding to the previous embodiments are denoted by the same reference numerals and will not be described further. The embodiment of figures 8 to 11 differs from the previous embodiment mainly in that it provides a slip ring instead of a cable carrier chain. This arrangement allows for infinite rotation of the C-axis unit.
The slip ring, shown as 200 in fig. 8-11, includes a stationary portion 201 mounted on the input support 181b and a rotating portion 202 made integral with the rotating portion 174 of the fluid rotary joint. The power and signal cables 181 connecting the electrical and digital control cabinet of the machine tool to the C-axis unit 120 are electrically connected to the stationary part 201 of the slip ring. The current and the signal are transmitted from the stationary part 201 of the slip ring to the rotating part 202 in a manner known per se. Additional electrical cables 181c are connected to the rotating part 202 of the slip ring and are distributed between the various users. Accordingly, these cables 181c are electrically connected partially to the spindle motor 160 and partially to the electrical connector 137 disposed on the bottom surface 131a of the head mounting platform 130. In the portion directly below the slip ring, these cables 181c pass through a central through hole obtained through the rotating portion 174 of the hydraulic rotary joint.
Naturally, without altering the principle of the invention, the details of these embodiments and constructions may be varied widely with respect to those described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the invention as defined by the appended claims.
