Counter bearing for a machining spindle of a machining machine and method for clamping a counter bearing

Description

[0001] The invention relates to a counter bearing for the rotatable mounting of a machining spindle of a machine tool according to the preamble of claim 1 and a method for clamping a counter bearing on a machining spindle of a machine tool according to the preamble of claim 12.

[0002] Clamping devices equipped with expansion bushings are known for clamping counter bearings onto spindles. Each device has an elastically deformable wall that defines an annular pressure chamber. A pressure medium, preferably grease, is introduced into the pressure chambers under pressure. To clamp the counter bearing onto the spindle, a high-pressure grease gun is connected to a corresponding port, pumping the grease into the pressure chamber at high pressure. To release the clamping force, a valve is opened, allowing some of the grease to drain away. Clean operation is not possible with such a clamping device. Grease escapes not only during the clamping process but also during the release, leading to contamination. Furthermore, using a high-pressure grease gun to clamp the counter bearing onto the spindle is very labor-intensive.

[0003] The invention is based on the objective of designing the generic counter bearing and the generic method in such a way that a simple, reliable and clean clamping and releasing process is possible.

[0004] This problem is solved according to the invention in the generic counter-bearing with the characterizing features of claim 1 and in the generic method with the characterizing features of claim 12.

[0005] The counter bearing according to the invention is characterized by a closed clamping system. To pressurize the pressure medium for the clamping process, the pressure element is mechanically actuated by means of a tool, which moves a piston towards the pressure chamber and pressurizes the pressure medium contained therein. This enables simple and quick clamping without the use of a grease gun, using a simple tool such as an Allen wrench.

[0006] The pressure element is advantageously located in a threaded bore. This allows the pressure element to be continuously rotated with the tool to achieve the required clamping pressure. To release the clamping force, the pressure element is rotated back, which also retracts the piston and reduces the pressure acting on the pressure medium.

[0007] In a structurally very simple embodiment, the pressure element is formed by a threaded pin that is screwed into the threaded hole.

[0008] To ensure that the pressure medium in the pressure chamber can be reliably pressurized, the piston is sealed and movable within a piston chamber.

[0009] The pressure chamber is advantageously connected to a pressure gauge. This allows the user to easily determine whether the required clamping pressure is being reached when adjusting the clamping pressure.

[0010] The pressure gauge advantageously features a plunger that sits in a bore opening into the pressure chamber and is slidably sealed within the bore. When the pressure medium in the pressure chamber is pressurized by the pressure element, the medium presses against the end face of the plunger, which acts as a piston and is displaced according to the applied pressure. This allows for a very simple determination, based on the plunger's position, of whether the required clamping pressure has been reached.

[0011] The plunger is advantageously spring-loaded in the direction of the pressure chamber. Due to the spring load, the plunger assumes a neutral position when the pressure medium is not pressurized. During the clamping process, the plunger is moved against the spring load until a balance of forces is reached between the piston force and the spring force.

[0012] Advantageously, the plunger is surrounded by a disc spring assembly. One end of this assembly rests against a stop on the plunger, while the other end rests against a retaining element. Since very high pressures are required for clamping, for example around 300 bar, the disc spring assembly enables correspondingly high spring forces acting on the plunger in the direction of the pressure chamber.

[0013] In a simple design, the retaining element for supporting the disc spring assembly is a threaded sleeve screwed into a threaded bore. The threaded sleeve has a through-hole into which the plunger protrudes. This makes it very easy for the user to determine the plunger's position within the threaded sleeve. The spring force, particularly that of a disc spring, and the piston force exerted by the pressure medium are advantageously selected so that, upon reaching the clamping force, the end face of the plunger is level with the end face of the threaded sleeve. This position of the plunger, which in its initial position is still within the threaded sleeve, can be reliably identified by the user.

[0014] According to the invention, the expansion bushing is arranged in a bearing hub of the counter bearing.

[0015] The closed system enables clean and reliable clamping of the bearing hub of the counter bearing on the spindle.

[0016] For the initial filling of the pressure chamber, the clamping device is equipped with a connection through which the pressure medium can be introduced into the pressure chamber.

[0017] It is advantageous for the pressure chamber to be connected to a pressure relief valve via a pipeline.

[0018] In the inventive method, the system is first filled with the pressure medium. This creates a closed clamping system, which then allows a counter bearing to be easily clamped by mechanically pressurizing the pressure medium using the piston. The piston is moved by a pressure element to pressurize the pressure medium to the appropriate pressure. The pressure gauge displays the clamping pressure setting, allowing the user to control and monitor it. To release the tension, the pressure element is simply moved mechanically in the opposite direction, pushing the piston back under the pressure of the pressure medium.

[0019] Advantageously, a screw-type component, such as a threaded stud, is used as the pressure element. This allows the piston to be moved continuously, enabling precise adjustment of the clamping pressure. Only a simple tool, such as an Allen key, is required to operate the screw-type component.

[0020] A plunger is advantageously used as a pressure indicator; this plunger acts as a piston loaded by the pressure medium and is moved against spring force by the pressure medium during the clamping process. The spring force also ensures that the plunger is pushed back when the clamping force is released.

[0021] The invention is explained in more detail below with reference to an embodiment illustrated in the drawings. The drawings show... Fig. 1 is an end view of a counter bearing according to the invention with a clamping device, Fig. 2 is a section along the line A - A in Fig.1 , Fig. 3 a section along the line B - B in Fig. 1 , Fig. 4 detail C in Fig. 2 in enlarged view.

[0022] In the illustrated embodiment, the clamping device is part of a counter bearing that enables a backlash-free and concentric connection with the spindle. It has a hydraulic expansion bushing 1 ( Fig. 2 ), which surrounds a spindle journal 2. The hydraulic expansion bushing 1 is provided with a pressure chamber 3 that extends over part of its length and around its circumference. Radially inwards, the pressure chamber 3 is bounded by a thin-walled section 4 of the hydraulic expansion bushing 1, which can be elastically deformed radially inwards under the pressure of a pressure medium located in the pressure chamber in order to clamp the spindle journal.

[0023] The hydraulic expansion bushing 1 is housed in a through-opening 5 of a bearing hub 6. The through-opening 5 is bounded by a wall 7, which is provided with an annular shoulder 8 against which the hydraulic expansion bushing 1 is supported axially. For this purpose, the hydraulic expansion bushing 1 is provided at one end with a projecting radial flange 9, with which the hydraulic expansion bushing 1 is axially supported against the annular shoulder 8. On both sides of the annular pressure chamber 3 are sealing rings 10, 11, preferably O-rings, which are inserted into annular grooves 12, 13 on the outer circumference of the hydraulic expansion bushing 1 and ensure the seal between the hydraulic expansion bushing and the bearing hub 6.

[0024] The pressure chamber 3 is sufficiently long to securely clamp the spindle pin 2. Its two ends protrude beyond the bearing hub 6 and point at its Fig. 2 At the lower end, there is a thread 57 for the spindle nut and a section 58 for a retaining ring. Part of a tool holder 59 is also visible.

[0025] The hydraulic expansion bushing 1 is flush with one end against an outer surface 14 of the bearing hub 6, while the other end, which has the radial flange 9, lies inside the through-opening 5.

[0026] The bearing hub 6 is equipped with a pressure gauge 15 and a pressure generator 16, with which the pressure medium located in the pressure chamber 3 can be pressurized.

[0027] The bearing hub 6 is also provided with a valve 17 for venting during initial filling with pressure medium and for pressure release in the pressure chamber 3 and with a connection 18 ( Fig. 3 ), through which the pressure medium is filled into pressure chamber 3.

[0028] As from Fig. 1 As can be seen, the pressure gauge 15, the pressure generator 16, the pressure relief valve 17 and the connection 18 are advantageously located offset from each other by 90° on one end face of the bearing hub 6. Depending on the design of the bearing hub 6, these parts 15 to 18 can also be provided at a different location and in a different distribution on the bearing hub 6.

[0029] The bearing hub 6 is advantageously widened in the area of ​​parts 15 to 18, so that sufficient installation space is available for these parts. The widening is formed by an annular flange 19, which is provided near one end of the bearing hub 6 and projects radially from a bushing-shaped base body 20 of the bearing hub. The base body 20 has the through-opening 5 for receiving the hydraulic expansion bushing 1.

[0030] The bearing hub 6 is surrounded by a sliding bushing 22, which encircles the bearing hub 6 almost along its entire length. The sliding bushing 22 is provided on its inner side with a radially projecting ring 23, with which the sliding bushing 22 engages behind the annular flange 19 of the bearing hub 6. In the exemplary embodiment, the sliding bushing 22 is held axially displaceable on a mounting plate 24 and is moved axially with the spindle during any axial adjustment. The mounting plate 24 is advantageously attached to a counter-bearing plate, which in turn is arranged on the machine frame.

[0031] On the side of the ring 23 facing away from parts 15 to 18, there is at least one rotary bearing 25, which in the exemplary embodiment is designed as a rolling bearing. The bearing hub 6 is rotatably mounted in the sliding bushing 22 by means of the rotary bearing 25.

[0032] The rotary bearing 25 is axially clamped against an annular shoulder 27 on the outside of the base body 20 by means of a clamping ring 26. The clamping ring 26 is placed onto the bearing in the Fig. 2 and 3 The lower end of the base body 20 of the bearing hub 6 is pushed onto it and secured with a threaded pin 60.

[0033] A sealing ring 28 is located between the clamping ring 26 and the rotary bearing 25. Its outer edge is fastened to the end face of the sliding bushing 22 by screws 29. The sealing ring 28 and the clamping ring 26 are designed to form a labyrinth seal in front of the rotary bearing 25. The sealing ring 28 has a radially outwardly projecting annular shoulder 61, which, together with an annular shoulder 62 arranged opposite it on the sliding bushing 22, defines an axial displacement range of the sliding bushing 22 in the mounting plate 24. This also prevents the counter bearing from falling out of the mounting plate 24.

[0034] The pressure gauge 15 ( Fig. 4 The device has a plunger 30, one end of which projects into a through-opening 31 of a threaded sleeve 32, which is screwed into a threaded bore 33 opening into the end face 21 of the ring flange 19. Advantageously, the end face of the threaded sleeve 33 is flush with the end face 21 of the ring flange 19.

[0035] The plunger 30 protrudes into a bore 34, which is provided in the base body 20 of the bearing hub 6 and opens into the pressure chamber 3 ( Fig. 2 ). The part of the plunger 30 lying in the bore 34 is sealed against the wall of the bore 34 by means of a sealing ring 35, preferably an O-ring ( Fig. 2 ).

[0036] The plunger 30 is surrounded in the area outside the bore 34 by at least one compression spring 36, which in the exemplary embodiment is formed by a disc spring assembly, wherein the individual disc springs are stacked on top of each other and the stacks are oriented in opposite directions to each other. The end of the compression spring 36 facing the threaded sleeve 32 is supported on the threaded sleeve 32 with a spacer 37 interposed. The other end of the compression spring 36 rests against a shoulder 38 ( Fig. 4 ), which is formed at the transition from a smaller diameter tappet part 39 to a larger diameter tappet part 40.

[0037] The compression spring 36 lies in a receiving chamber 41, which is provided in the area of ​​the ring flange 19 of the bearing hub 6 and has a larger diameter than the bore 34 opening into it and which continues outwards in the threaded bore 33.

[0038] The spacer 37 serves to compensate for spring tolerances, so that the function of the plunger 30, which will be described later, is guaranteed at all times.

[0039] The plunger part 40, which protrudes into the bore 34, forms a piston which is subjected to pressure by the pressurized medium located in the pressure chamber 3.

[0040] When the pressure chamber 3 is filled with the medium, usually hydraulic grease, and pressurized, the plunger 30 is subjected to outward force. The force exerted on the piston 40 by the pressure medium displaces the plunger 30 until a balance of forces is reached between the force acting on the piston 40 and the opposing force of the compression spring 36. The spring force is advantageously selected such that, in the compressed state, the end face 42 of the plunger 30 is flush with the end face 43 of the threaded sleeve 32. The pressure in the pressure chamber 3 is then sufficiently high to securely clamp the spindle pin 2. Since the end section of the plunger 40 is sealed within the bore 34, a reliable pressure reading is ensured by the plunger 30.

[0041] The pressure indicator can also be provided by a marking on the plunger 30, such as a ring groove, a mark, and the like.

[0042] The pressure generator 16 has a threaded pin 55 screwed into a threaded bore 44 ( Fig. 2 ), which interacts with a piston 46, which is sealed by means of a sealing ring 47 and is displaceable in a piston chamber 48.

[0043] The threaded bore 44 opens into the end face 21 of the ring flange 19 of the bearing hub 6. The piston 46 can be adjusted in the piston chamber 48 by means of the threaded pin 45. The piston 46 can also be detachably connected to the threaded pin 45 or be formed integrally with it.

[0044] A bore 50 opens into the base 49 of the piston chamber 48, connecting the piston chamber 48 to the pressure chamber 3. The bore 50, which is provided in the base body 20 of the bearing hub 6, has a smaller diameter than the piston chamber 48, which is located essentially in the area of ​​the ring flange 19.

[0045] The threaded pin 45 advantageously projects beyond the end face 21 of the ring flange 19, so that the threaded pin 45 can be conveniently adjusted with a suitable tool.

[0046] Advantageously, the sliding bushing 22 projects axially beyond the ring flange 19 to such an extent that it also projects axially beyond the threaded pin 45. The medium in the pressure chamber 3 is pressurized by the threaded pin 45, which moves the piston 47 inwards by turning the threaded pin 45. The pressurized medium is located not only in the pressure chamber 3, but also in the bores 34, 50 and in the piston chamber 48, so that small adjustment movements of the piston 46 are sufficient to pressurize the medium. During the clamping process, turning the threaded pin 45 moves the plunger 30 of the pressure gauge 15 out of its position. Fig. 4 The starting position shown is shifted against the force of the compression spring 36 so that the end face 42 of the plunger 30 is flush with the end face 43 of the threaded sleeve 33. Since the threaded pin 45 and the pressure indicator 15 are provided on the same end face of the ring flange 19, the user can very easily set, check and monitor the required clamping pressure.

[0047] Connection 18 is used to fill pressure chamber 3 with the pressure medium ( Fig. 3 ), which is designed as a high-pressure nipple. It is inserted into a bore 51, which opens into a base 52 of a recess 53 provided in the end face 21 of the ring flange 19 of the bearing hub 6. A feed bore 54 opens into the bore 51, connecting the bore 51 to the pressure chamber 3.

[0048] For example, a high-pressure grease gun is connected to port 18, through which the grease to be pressurized is filled into pressure chamber 3 as a pressure medium.

[0049] The pressure relief valve 17 is also provided in the end face 21 of the ring flange 19. It primarily serves for venting during filling with pressurized medium. If necessary, the pressure can also be reduced by opening the valve 17, allowing a small amount of pressurized medium to escape.

[0050] During initial filling, the threaded pin 45 is screwed in until the piston 46 rests against the bottom 49 of the piston chamber 48. Using the high-pressure grease gun, the grease medium is initially introduced via the connection 18 with the pressure relief valve 17 open until the system is vented, i.e., completely filled with grease. The pressure relief valve 17 is then closed, and the grease medium is injected until the end face 42 of the plunger 30 is flush with the end face 43 of the threaded sleeve 32. If the high-pressure grease gun has a pressure gauge, the pressure can be read from it. To release the pressure, the threaded pin 45 can be turned back until the pressure is relieved. Subsequent clamping operations are always performed by screwing the threaded pin 45 in fully, which automatically establishes the correct clamping pressure. This pressure is indicated by the pressure gauge and monitored by the operator.

[0051] The filling process can also be carried out by screwing the threaded pin 45 back into its other end position. In this case, the filling with the pressure medium takes place without pressure build-up. Once the filling process is complete, the threaded pin 45 is screwed into the threaded bore 44 so that the piston 46 pressurizes the pressure medium. The threaded pin 45 is screwed in until the correct clamping pressure is indicated on the pressure gauge 15.

[0052] The spindle pin 2 is provided with an axial drive groove 55 into which a torque drive 56 is inserted ( Fig. 1 ) engages. It is attached to the front face of the bearing hub 6.

[0053] The described counter bearing allows for simple and quick assembly. To generate pressure, the threaded pin 45 simply needs to be turned with a suitable tool to create the clamping pressure in the pressure chamber 3. The threaded pin 45 is advantageously designed as an Allen screw, which can be turned around its axis with a suitable wrench. A simple clamping check can be performed using the pressure indicator 15. To release the clamping force, the threaded pin 46 is simply turned back with the tool. The user can carry the tool for turning the threaded pin 45 with them. No pressure medium escapes during the clamping and releasing process, thus ensuring clean operation.

[0054] Any potential leakage of the printing medium can be compensated for at any time by refilling the medium via connection 18, should it be necessary.

[0055] Minor leaks can be compensated for by the plunger 30. Since it is pre-tensioned by the compression spring 36, the plunger 30 is readjusted by the compression spring 36 in the event of minor leaks, so that sufficient pressure for reliable clamping is maintained.

[0056] The described clamping system is a closed system. The pressure medium is introduced during initial filling using a high-pressure grease gun via connection 18. Since the bearing hub 6 has the pressure indicator 15, the grease gun does not need to have a pressure gauge, as the correct pressure is indicated by the pressure indicator 15. However, a pressure gauge is advantageous for the initial filling of the system and for checking the accuracy of the pressure indicator 15.

[0057] To tighten and loosen the spindle journal 2, only the tool required to actuate the threaded pin 45 is necessary, for example, an Allen key. This key can also be used for other operations during machine setup. Therefore, only a few tools are needed to set up the machine.

[0058] The pressure gauge 15 allows you to check at any time whether the tension is still at the desired level. This is advisable daily and after every time the machine is switched on. This eliminates the need for the cumbersome handling of a grease gun, which was previously required to check the correct tension. With a grease gun, you would have had to connect it to port 18 and pressurize it to the required pressure, which had to be read on the pressure gauge.

[0059] It is not within the scope of the invention to use the described closed system for clamping tools on a spindle in the same way. In this case, the elements 15 to 18 are located in the base body of the tool, to which the blades and the like required for machining workpieces are attached.

[0060] Since tools are mounted on the machining spindles in different orientations depending on the direction of rotation, they advantageously have the pressure gauge 15 and the pressure generator 16 on both end faces, each connected to the pressure chamber 3. Long tools can also be designed with an expansion sleeve on each opposite side. Here, the pressure chambers 3 of the two expansion sleeves 1, as well as the pressure gauges 15 and pressure generator 16 on both end faces, are connected to each other via bores in the tool body, so that here too only a closed system is present. It is not necessary to provide the filling port 18 and the pressure relief valve 17 on both end faces.It is sufficient to arrange this on an end face or advantageously on the circumference of the tool body, since these are not needed for normal tool clamping, but only for initial filling and, if necessary, for subsequent refilling or follow-up inspection.

Claims

1. Counterbearing for rotatable mounting of a machining spindle of a machine tool, in particular a woodworking machine, preferably a moulding machine the counterbearing comprising at least one expansion bushing (1) provided for receiving a spindle pin (2) of the machining spindle, which is arranged in a bearing hub (6) of the counterbearing and whose elastically deformable wall (4) delimits at least one pressure chamber (3) which accommodates a pressure medium and into which a supply line (54) for the pressure medium opens, characterized in that the counterbearing has a closed system for clamping in which a pressure line (50) opens into the pressure chamber (3), in which pressure line is located a pressure element (45) which can be actuated mechanically by means of a tool (45) by means of which a piston (46) on which the pressure medium acts is displaceable.

2. Counterbearing according to Claim 1, characterized in that the pressure element (45) is seated in a threaded bore (44).

3. Counterbearing according to Claim 1 or 2, characterized in that the pressure element (45) is a threaded pin.

4. Counterbearing according to one of Claims 1 to 3, characterized in that the piston (47) is displaceable in a sealed manner in a piston chamber (48).

5. Counterbearing according to one of Claims 1 to 4, characterized in that the pressure chamber (3) is connected by a conduit to a pressure display (15).

6. Counterbearing according to Claim 5, characterized in that the pressure display (15) comprises a plunger (30) seated in a bore (34), which opens into the pressure chamber (3) and is displaceable in a sealed manner in the bore (34).

7. Counterbearing according to Claim 6, characterized in that the plunger (30) is spring-loaded in the direction of the pressure chamber (3).

8. Counterbearing according to Claim 6 or 7, characterized in that the plunger (30) is surrounded by a plate spring stack (36) having one end supported against a stop (38) on the plunger side and the other end supported against a securing part (32).

9. Counterbearing according to Claim 8, characterized in that the securing part (32) is a threaded sleeve that is screwed into a threaded bore (33) and has a through opening (31), into which the plunger (30) projects.

10. Counterbearing according to one of Claims 1 to 9, characterized in that the pressure chamber (3) is connected by a conduit to a connector (18) for filling the pressure chamber with the pressure medium.

11. Counterbearing according to one of Claims 1 to 10, characterized in that the pressure chamber (3) is connected by a conduit to a pressure relief valve (17) .

12. Method for clamping a counterbearing on a machining spindle of machine tool, in particular a woodworking machines, preferably a moulding machine, characterized in that a pressure chamber (3) of the counterbearing delimited by an elastically deformable wall (4) is initially filled with a pressure medium, so that a closed clamping system is obtained and the pressure medium is pressurized during clamping of the counterbearing on the machining spindle with a plunger (46) which is mechanically displaced by a pressure element (45) wherein the setting of the clamping pressure is displayed by means of a pressure display (15).

13. Method according to Claim 12, characterized in that the pressure element (45) is a screw part.

14. Method according to Claim 12 or 13, characterized in that the pressure display (15) comprises a plunger (30) pressurized by the pressure medium acting as a piston which is displaced against a spring force by the pressure medium.