Device for clamping a workpiece to a machine tool

Abstract

A device (1) for clamping a workpiece to a machine tool comprises: a base body (2); holding means (7) associated with the base body (2) and movable between a clamping configuration and a release configuration; and at least one moving unit (8) associated with the base body (2) and adapted to move the holding means (7) between the clamping configuration and the release configuration, the moving unit (8) comprising: a first sliding part (9a); a first clamping piston (11a) associated with the first sliding part (9a); a first release piston (12a) associated with the first sliding part (9a); a second sliding part (9b); a second clamping piston (11b) associated with the second sliding part (9b); a second release piston (12b) associated with the second sliding part (9b); and friction compensation assemblies (30, 31) associated with the clamping pistons (11a, 11b).

Description

Technical Field

[0001] The present invention relates to a device for clamping a workpiece to a machine tool.

Background Art

[0002] As is well known, in the mass production of mechanical workpieces that require machining on a machine tool, there is a widespread use of highly automated systems, where one or more machine tools are electronically controlled by a processing and control unit, and one or more anthropomorphic robots guide the workpiece to be machined to the machine tool, where a special clamping device, which is hydraulic or pneumatic, takes over the workpiece and clamps it in place to enable machining of the workpiece.

[0003] When the machining is completed, the above-mentioned clamping device releases the machined workpiece, which is then removed again by the robot.

[0004] A special type of clamping device achieves its purpose by means of a pair of jaws. This pair of jaws is moved between a clamping configuration, in which they move towards each other to clamp the workpiece, and a release configuration, in which the jaws move away from each other to release the workpiece, by a hydraulic drive unit.

[0005] Specifically, the aforementioned hydraulic drive unit comprises two moving assemblies, each of which is associated with a respective jaw and comprises: - a sliding part mounted on the jaw and sliding and locking along with the jaw in the working direction; and - two hydraulic pistons mounted inside respective cylinders, between which the sliding part is positioned, and which slides along the working direction as a result of the operation of the hydraulic pistons. comprises.

[0006] In this case, due to the driving force applied by the pressurized hydraulic fluid, the piston enables the sliding parts to slide along both directions of the working direction related to them, thereby moving the attached jaws between the clamping configuration and the release configuration.

[0007] In fact, two of the total four pistons are operable to push the jaws towards each other to close them, arranging the jaws in the clamping configuration. On the other hand, the other two are operable to push the jaws away from each other to open them, arranging the jaws in the release configuration.

[0008] Since the aforementioned pistons are of the hydraulic type, special sealing parts (such as O-ring type) are also provided in known clamping devices, and they are fitted onto the pistons themselves at predetermined positions to prevent unwanted leakage of hydraulic fluid under pressure.

[0009] Specifically, these sealing parts are designed to flatten during the assembly of the pistons in their respective cylinders and expand in a radial pattern. Due to this feature, the sealing parts adhere to the cylinder walls, actually achieving a watertight seal within the cylinder.

[0010] Therefore, it is important to note the fact that the jaws must be able to apply a uniform and very large clamping force to the workpiece.

[0011] This necessity is particularly felt in industries where the continuous need to optimize the production cycle leads to the use of tools that operate at very high speeds, exerting very strong forces and vibrations on the workpiece, which must be counteracted by the clamping system.

[0012] In many industries, the use of particularly lightweight materials such as aluminum is becoming increasingly common, but they cannot guarantee the same strength as materials such as cast iron and steel during machining on machine tools.

[0013] Therefore, with respect to the jaws, each time a new workpiece is attached to the machine tool, it is necessary to touch the workpiece with a very high force, in addition to high precision, accuracy, and in a reproducible manner. Otherwise, the large force actually applied by the jaws may deform the workpiece and compromise the quality of the machining, resulting in the risk of obtaining unacceptable workpieces.

[0014] However, this important advantage is not at all satisfied by known clamping devices.

[0015] In this regard, it should be well considered that the seals fitted in the hydraulic pistons always exert a certain resistance to the sliding of the hydraulic pistons, and it is not uncommon for this resistance to be of different intensities between one piston and another.

[0016] The resistance to sliding caused by the seals actually depends highly on the degree of pressing-in of the seals. This pressing-in has been found to vary somewhat in actual seals, even when the seals are clearly identical to each other and are compressed to substantially the same extent.

[0017] The various frictional forces clearly result in various pressurization timings of the hydraulic pistons, whereby one of the two jaws, specifically the one associated with the piston with less frictional action, will touch the workpiece earlier than the other.

[0018] The inaccuracy of this operation has been found to be very inconvenient. Because the jaw that first contacts the workpiece will apply a particularly strong force to the workpiece, which poses a significant risk to the structural integrity of the workpiece.

[0019] In light of this, it is easy to understand that there is room for improvement in the clamping device of the jaws. Summary of the Invention Problems to be Solved by the Invention

[0020] The main object of the present invention is to devise a device for clamping a workpiece to a machine tool with accurate and reliable operation, the device enabling the jaws to deploy substantially simultaneously to the workpiece and clamping the workpiece stably to the machine tool without deforming it.

[0021] Another object of the present invention is to devise a device for clamping a workpiece to a machine tool that enables the above-mentioned drawbacks of the prior art to be overcome within a framework of a solution that is easy to use, reasonable, simple, efficient and, likewise, affordable.

Means for Solving the Problems

[0022] The above object is achieved by the present device for clamping a workpiece to a machine tool having the features of claim 1.

[0023] Other features and advantages of the present invention will become clearer from the description of the preferred but non-exclusive embodiments of the device for clamping a workpiece to a machine tool, shown by way of non-limiting illustration in the accompanying drawings.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0025] Referring to these figures in detail, reference numeral 1 generally indicates a device for clamping a workpiece to a machine tool.

[0026] The device 1 for clamping a workpiece to a machine tool first comprises at least one base body 2 which can be fixed to the machine tool.

[0027] The base body 2 comprises at least one central block 3 and at least one first side wall 4 and a second side wall 5, and the first side wall 4 and the second side wall 5 are connected to the central block 3 in a removable manner.

[0028] Specifically, in the assembly configuration of the device 1 in which the components are assembled to each other, the central block 3 is connected to the side walls 4, 5 by means of a plurality of connecting elements 6 (such as screws, etc.).

[0029] Specifically, the first side wall 4 and the second side wall 5 each comprise a first connection hole 4a and a second connection hole 5a, into which a connecting element 6 for connecting the side walls 4, 5 to the central block 3 can be fitted.

[0030] Therefore, if it is necessary to repair / replace one or more components in the device 1, one or both of the side walls 4, 5 can be removed from the central block 3 simply by removing the connecting element 6.

[0031] The said device 1 is - gripping means 7 for the workpiece to be machined, associated with the base body 2, comprising at least one first gripping jaw 7a and at least one second gripping jaw 7b, the gripping means 7 being movable between at least one clamping configuration of the workpiece in which the gripping jaws 7a, 7b approach each other and at least one release configuration of the workpiece in which the gripping jaws 7a, 7b are moved away from each other with respect to the clamping configuration; - At least one moving unit 8 associated with the base body 2 and adapted to move the gripping means 7 between a clamping configuration and a release configuration, - At least one first sliding part 9a that slides along at least one first working direction D1 and is associated with the first gripping jaw 7a, and - At least one second sliding part 9b that slides along at least one second working direction D2 parallel to the first working direction D1 and is associated with the second gripping jaw 7b, At least one movement unit 8 having; Comprises.

[0032] Specifically, the gripping jaws 7a, 7b are mounted on their respective sliding parts 9a, 9b and are slidably locked together with the sliding parts 9a, 9b along the working directions D1, D2 of the respective sliding parts 9a, 9b.

[0033] Additionally, the sliding parts 9a, 9b are associated with the central block 3 and are thereby positioned between the two side walls 4, 5.

[0034] In this regard, at least one guiding element 10 is provided on the central block 3, and together with it, the sliding parts 9a, 9b are associated along their respective working directions D1, D2 in a sliding manner.

[0035] Specifically, as can be seen in FIG. 2, the guiding element 10 is substantially hollow and is cut on the central block 3 in a direction parallel to the working directions D1, D2, in which the sliding parts 9a, 9b slide and are received.

[0036] In detail, the guiding element 10 has a configuration that is substantially complementary to the configuration of the sliding parts 9a, 9b, thereby enabling the sliding parts 9a, 9b to slide smoothly and accurately along the working directions D1, D2 of the respective sliding parts 9a, 9b.

[0037] In order to enable the first sliding part 9a to move along the first working direction D1, the moving unit 8 is: - At least one clamping piston 11a, which is operably associated with the first sliding part 9a and is movable so as to enable the first sliding part 9a and the gripping jaws 7a associated therewith to slide along at least one first clamping direction B1 in which they move closer to the second gripping jaws 7b by the propulsive force of at least one type of pressurized fluid; - At least one first release piston 12a, which is operably associated with the first sliding part 9a and is movable so as to enable the first sliding part 9a and the first gripping jaws 7a to slide along at least one first release direction R1 opposite to the first clamping direction B1 and away from the second gripping jaws 7b by the propulsive force of pressurized fluid, at least one first release piston 12a, Comprising.

[0038] In fact, by pressurizing the first clamping piston 11a and the first release piston 12a using pressurized fluid, they will be moved along both directions of the first working direction D1 (i.e., the first clamping direction B1 and the first release direction R1), pulling the first sliding part 9a, and as a result, pulling the first gripping jaws 7a by sliding.

[0039] In this regard, in the context of the present disclosure, "pressurized fluid" means any fluid in a liquid (and thus ideally incompressible) or gas (and thus compressible) state and is used as a carrier medium for conveying energy in a hydraulic or pneumatic circuit. It is important to clarify that preferably the pressurized fluid consists of conventional mineral oil, but alternative embodiments such as synthetic lubricants, vegetable oils, water, air, etc. cannot be excluded.

[0040] This preferably means that the first clamping piston 11a and the first release piston 12a are of the hydraulic piston type, but it cannot be excluded that the first clamping piston 11a and the first release piston 12a can be of, for example, the pneumatic piston type (when the pressurized fluid is air) or the hydraulic piston type (when the pressurized fluid is water).

[0041] Additionally, in consideration of the presence of the device 1 at various parts in contact with the pressurized fluid, in order to simplify the display, it is also made clear that special sealing parts, which are commonly identified by the reference number 14 and arranged at various points of the device 1, are provided.

[0042] Thus, by describing in detail the components just mentioned, it is explained that the first clamping piston 11a is at least partially received within the first side wall 4.

[0043] Similarly, the first release piston 12a is at least partially received within the second side wall 5.

[0044] In this regard, at least one first internal housing 13a, in which the first clamping piston 11a is at least partially fitted, and at least one second internal housing 13b of the first release piston 12a, in which the second clamping piston 11b is at least partially fitted, are respectively provided on the first side wall 4 and the second side wall 5.

[0045] The first housing 13a and the second housing 13b are substantially cylinders in which the first clamping piston 11a and the first release piston 12a respectively slide.

[0046] The moving unit 8 is: - at least one second clamping piston 11b, which is operably associated with the second sliding part 9b and is movable so as to be able to slide along at least one second clamping direction B2 in which the second sliding part 9b and the second gripping jaw part 7b move closer to the first gripping jaw part 7a by the propulsive force of the pressurized fluid. - At least one second release piston 12b, which is operably associated with the second sliding part 9b and, by the propulsive force of the pressurized fluid, enables the second sliding part 9b and the second gripping jaw part 7b to move along at least one second release direction R2, which is opposite to the second tightening direction B2 and away from the first gripping jaw part 7a, and is movable so as to be slidable. At least one second release piston 12b, is also provided.

[0047] In fact, by pressurizing the second tightening piston 11b and the second release piston 12b using pressurized fluid, they will be moved along both directions of the second working direction D2 (that is, the second tightening direction B2 and the second release direction R2), pulling the second sliding part 9b by sliding, and as a result, pulling the second gripping jaw part 7b.

[0048] Similar to what has been described above, the second tightening piston 11b and the second release piston 12b are preferably of the hydraulic piston type, but it cannot be excluded that they can be of the pneumatic piston type (when the pressurized fluid is air) or the hydraulic piston type (when the pressurized fluid is water).

[0049] Regarding the location of the newly introduced components, the second tightening piston 11b is at least partially accommodated within the first side wall 4, while the second release piston 12b is at least partially accommodated within the second side wall 5.

[0050] In this regard, at least one first internal seat part 15a of the first release piston 12a and at least one second internal seat part 15b of the second release piston 12b are respectively provided on the first side wall 4 and the second side wall 5.

[0051] The first seat part 15a and the second seat part 15b are substantially cylinders, inside of which the first release piston 12a and the second release piston 12b slide respectively.

[0052] By introducing the main components for the movement of the gripping means 7, for arranging the gripping means 7 in the clamping configuration, the first clamping piston 11a is moved along the first clamping direction B1 in the first working direction D1, thereby enabling the first sliding part 9a and the associated first gripping jaw 7a to slide in that direction, it is useful to clarify this.

[0053] At the same time, the second clamping piston 11b is simultaneously moved along the second clamping direction B2 in the second working direction D2, and the second sliding part 9b and the associated second gripping jaw 7b slide in that direction.

[0054] From this, it can be inferred that the first clamping direction B1 and the second clamping direction B2 are opposite to each other.

[0055] Similarly, for arranging the gripping means 7 in the release configuration, the first release piston 12a is moved along the first release direction R1 in the first working direction D1, thereby enabling the first sliding part 9a and the associated first gripping jaw 7a to slide in that direction.

[0056] At the same time, the second release piston 12b is simultaneously moved along the second release direction R2 in the second working direction D2, sliding the second sliding part 9b and the associated second gripping jaw 7b in that direction.

[0057] From this, it can be inferred that the first release direction R1 and the second release direction R2 are opposite to each other.

[0058] This follows from the fact that the first clamping direction B1 and the second release direction R2 are in the same direction, and the second clamping direction B2 and the first release direction R1 are also in the same direction.

[0059] In order to reduce the friction acting on the sliding parts 9a, 9b during sliding, which was described immediately before, the moving unit 8 preferably comprises at least one lubricating line G connected to the first sliding part 9a and the second sliding part 9b. The lubricating line G is adapted to lubricate the first sliding part 9a and the second sliding part 9b with at least one type of lubricating compound (a high-viscosity lubricating oil, such as a type of grease).

[0060] Specifically, the lubricating line G is provided with at least one external access port 16 that cuts into the side surface of the central block 3, through which the lubricating compound can be inserted.

[0061] In this way, the lubricating line enables the sliding parts 9a, 9b to slide efficiently along their respective working directions D1, D2, and significantly reduces the friction acting on the sliding parts 9a, 9b.

[0062] Continuing with the detailed description of the moving unit 8, it is important to add that the moving unit 8 comprises: - at least one first inlet chamber 17a of pressurized fluid, bounded by a first clamping piston 11a and at least one first bottom wall 18a; and - at least one second inlet chamber 17b of pressurized fluid, bounded by a second clamping piston 11b and at least one second bottom wall 18b. It is important to add that it comprises these.

[0063] Specifically, the moving unit 8 also comprises at least one first circulation line L1 of pressurized fluid, which is connected to the first inlet chamber 17a and the second inlet chamber 17b and is adapted to at least partially fill the first inlet chamber 17a and the second inlet chamber 17b with pressurized fluid.

[0064] Specifically, at least one associated first outer supply inlet 19 is provided in the first circulation line L1. The first outer supply inlet 19 is formed on the side surface of the central block 3 and can be used to fill at least part of the first circulation line L1 with pressurized fluid.

[0065] In this way, in order to arrange the gripping means 7 in the clamping configuration, pressurized fluid is introduced into the first circulation line L1 through the first supply inlet 19.

[0066] In this way, the pressurized fluid is conveyed into the first inlet chamber 17a and the second inlet chamber 17b, applying a propulsive force to the first clamping piston 11a and the second clamping piston 11b, which enables the first sliding part 9a to slide in the first clamping direction B1 and the second sliding part 9b to slide in the second clamping direction B2.

[0067] Furthermore, the moving unit 8 includes: - at least one first introduction chamber 20a of pressurized fluid bounded by the first release piston 12a and at least one first bottom surface 21a; and - at least one second introduction chamber 20b of pressurized fluid bounded by the second release piston 12b and at least one second bottom surface 21b. It is provided with.

[0068] Very similar to the above-described, the moving unit 8 also includes at least one second circulation line L2 of pressurized fluid, which is connected to the first introduction chamber 20a and the second introduction chamber 20b and is adapted to fill at least part of the first introduction chamber 20a and the second introduction chamber 20b with pressurized fluid.

[0069] Specifically, at least one associated second outer supply inlet 22 is provided in the second circulation line L2. The second outer supply inlet 22 is formed on the side surface of the central block 3 and can be used to fill at least part of the second circulation line L2 with pressurized fluid.

[0070] Thus, in order to dispose the gripping means 7 in the release configuration, pressurized fluid is introduced into the second circulation line L2 through the second supply inlet 22.

[0071] In this way, the pressurized fluid is conveyed into the first introduction chamber 20a and the second introduction chamber 20b, applying a propulsive force to the first release piston 12a and the second release piston 12b, which enables the first sliding part 9a to slide in the first release direction R1 and the second sliding part 9b to slide in the second release direction R2.

[0072] In the switching from the release configuration to the clamping configuration, the pressurized fluid is discharged from the introduction chambers 20a, 20b, conveyed from the second circulation line L2 to the first circulation line L1 (for example, by a special hydraulic connection), and finally fed into the inlet chambers 17a, 17b.

[0073] In this way, by invalidating the propulsive force acting on the release pistons 12a, 12b and reversing the sliding directions of the sliding parts 9a, 9b, it is possible to transmit the propulsive force to the clamping pistons 11a, 11b (that is, by stopping the sliding of the sliding parts 12a, 12b along the release directions R1, R2 and forcing the sliding along the clamping directions B1, B2).

[0074] In the opposite case, in the switching from the clamping configuration to the release configuration, the pressurized fluid is discharged from the inlet chambers 17a, 17b, conveyed from the first circulation line L1 to the second circulation line L2 (for example, by a special hydraulic connection), and finally fed into the introduction chambers 20a, 20b.

[0075] In this way, by invalidating the propulsive force acting on the clamping pistons 11a, 11b and reversing the sliding directions of the sliding parts 9a, 9b, it is possible to transmit the propulsive force to the release pistons 12a, 12b (that is, by stopping the sliding of the sliding parts 12a, 12b along the clamping directions B1, B2 and forcing the sliding along the release directions R1, R2).

[0076] When the gripping means 7 is in the clamping configuration, to ensure that the workpiece is firmly fixed, the device 1 comprises stop means 23, 24 associated with the base body 2.

[0077] In this regard, the central block 3 is provided with at least one recess 25 in which the stop means 23, 24 are arranged.

[0078] Specifically, the stop means 23, 24 comprise at least one stop piston 23 which is movable along at least one stop direction A which is substantially orthogonal to the working directions D1, D2 and which is adapted to clamp the sliding parts 9a, 9b by friction in the clamping configuration.

[0079] Specifically, the stop direction A is orthogonal to the first working direction D1 and the second working direction D2.

[0080] According to a preferred embodiment, the first sliding part 9a and the second sliding part 9b each comprise at least one first recessed part 26a and at least one second recessed part 26b. The recessed parts 26a, 26b are juxtaposed with each other and define at least one internal space S between the sliding parts 9a, 9b.

[0081] As is apparent in Figure 2, the space S extends in a direction parallel to the working directions D1, D2.

[0082] Furthermore, the stop piston 23 is provided with at least one enlarged part 27 which can be inserted into the space S to clamp the sliding parts 9a, 9b (see Figure 5 in this regard).

[0083] Specifically, the enlarged part 27 has a so-called "dovetail" configuration.

[0084] In order to insert the enlarged portion 27 into the space S and thereby clamp the sliding parts 9a, 9b, the locking means 23, 24 comprise at least one elastically compressible propulsion element 24 which is positioned between one end of the locking piston 23 and the base body 2 and is adapted to apply at least one direct propulsion force to the locking piston 23 along the locking direction A.

[0085] More precisely, as is apparent in FIG. 5, the propulsion element 24 is positioned between one end of the locking piston 23 and at least one bottom 28 of the base body 2 arranged to close the recess 25, separating the propulsion element 24 from the outside.

[0086] Advantageously, the propulsion element 24 is of the spring type, for example a disc spring.

[0087] In order to move the enlarged portion 27 away from the space S and thereby release the sliding parts 9a, 9b, the locking means 23, 24 comprise a third circulation line L3 for the associated pressurized fluid.

[0088] Specifically, the third circulation line L3 is provided with at least one associated third external supply inlet 29. The third outer supply inlet 29 is made on the side surface of the central block 3 and can be used to fill the third circulation line L3 at least partially with pressurized fluid.

[0089] The third circulation line L3 terminates at the end of the locking piston 23 on the opposite side of the propulsion element 24. In this way, when the force generated by the pressurized fluid causes the propulsion element 24 to move closer to the bottom 28, the propulsion element 24 is pushed in, reducing its length, thereby enabling the enlarged portion 27 to be disengaged from the space S.

[0090] After the pressurized fluid is discharged from the third circulation line L3, the compressive force applied to the propulsion element 24 by the pressurized fluid is lost, whereby the propulsion element 24 pushes the locking piston 23 along the locking direction A and inserts its enlarged portion 27 into the space S.

[0091] From what has been described immediately above, it is easy to understand that, in the release configuration, the pressurized fluid is introduced both along the second circulation line L2 (so as to be able to fill the introduction chambers 20a, 20b) and along the third circulation line L3 (so as to be able to disengage the enlarged portion 27 from the space S).

[0092] On the other hand, the pressurized fluid is introduced only along the first circulation line L1 in the clamping configuration (so as to be able to fill the inlet chambers 17a, 17b and the enlarged portion 27 can be fitted into the space S).

[0093] The fact is emphasized that, in the clamping configuration, providing the stop means 23, 24 for the sliding parts 9a, 9b is a somewhat advantageous technical means for ensuring that the workpiece is continuously and firmly captured by the gripping jaws 7a, 7b.

[0094] It is easy to understand how this fact ensures an effective, accurate and precise operation of the device 1 by avoiding the possibility of unwanted movement of the gripping jaws 7a, 7b in the clamping configuration.

[0095] According to the invention, the moving unit 8 comprises at least one friction compensation assembly 30, 31 associated with the clamping pistons 11a, 11b.

[0096] Specifically, the friction compensation assemblies 30, 31 are adapted to compensate for the friction acting on the clamping pistons 11a, 11b which slide along the clamping directions B1, B2 of the associated working directions D1, D2.

[0097] In fact, by way of example, the presence of the seal 14 gives rise to a significant possibility of generating frictional forces of different intensities between the clamping pistons 11a, 11b, whereby one of the gripping jaws 7a, 7b will affect the workpiece earlier than the other.

[0098] In the remainder of the present disclosure, as will be described in more detail, by providing the friction compensation assemblies 30, 31, the gripping jaws 7a, 7b are simultaneously stationary with respect to the workpiece, and the device 1 can be completely and stably clamped to the machine tool without deforming the workpiece, thereby completely eliminating this inconvenient possibility.

[0099] In beginning a more detailed description of the friction compensation assemblies 30, 31, it is first mentioned that it comprises a first loading means 30a associated with the first clamping piston 11a and a second loading means 30b associated with the second clamping piston 11b. The loading means 30 is adapted to apply at least one preloading force that is substantially parallel to the working directions D1, D2 and that coincides with the clamping directions B1, B2, to the clamping pistons 11a, 11b.

[0100] This means that the first loading means 30a applies a preloading force to the first clamping piston 11a in a direction parallel to the first working direction D1 and that coincides with the first clamping direction B1, while the second loading means 30b applies a preloading force to the second clamping piston 11b in a direction parallel to the second working direction D2 and that coincides with the second clamping direction B2.

[0101] Specifically: - The first loading means 30a comprises at least one elastically compressible first loading element 32a, which is arranged to abut against the first bottom wall 18a and the first clamping piston 11a; while - The second loading means 30b comprises at least one elastically compressible second loading element 32b, which is arranged to abut against the second bottom wall 18b and the second clamping piston 11b.

[0102] More specifically, the first clamping piston 11a defines at least one first tubular cavity 33a, in which the first loading element 32a is at least partially received.

[0103] Similarly, the second clamping piston 11b defines at least one second tubular cavity 33b, in which the second loading element 32b is at least partially received.

[0104] In fact, the first loading element 32a is arranged to abut against the bottom of the first tubular cavity 33a and the first bottom wall 18a, while the second loading element 32b is arranged to abut against the bottom of the second tubular cavity 33b and the second bottom wall 18b.

[0105] That is, it is made clear that the first loading element 32a and the second loading element 32b are of a spring type, such as a coil spring.

[0106] Therefore, the preloading forces generated on the first clamping piston 11a by the first preloading means 30a and on the second clamping piston 11b by the second preloading means 30b correspond to the spring forces stored by the compression of the first loading element 32a and the second loading element 32b, respectively.

[0107] It is important to note that the preloading forces acting on the first clamping piston 11a and the second clamping piston 11b reduce the pressurization time (i.e., the speed at which the gripping means 7 is moved from the clamping configuration / release configuration to the release configuration / clamping configuration) of the first clamping piston 11a and the second clamping piston 11b to a range proportional to the intensity.

[0108] This means that when the preloading forces acting on the first clamping piston 11a and the second clamping piston 11b increase, the time required for the first clamping piston 11a and the second clamping piston 11b to complete their strokes inside the first housing 13a and the second housing 13b, respectively, decreases, and vice versa.

[0109] In fact, there is an inverse proportional relationship between the preloading forces acting on the clamping pistons 11a, 11b and the pressurization time of the clamping pistons 11a, 11b.

[0110] It is easy to understand that the frictional forces acting on the various clamping pistons 11a, 11b naturally have different intensities among them, yet they share the fact that they are in opposite directions with respect to their respective preloading forces.

[0111] In other words, the specific frictional force by the sealing portion 14 and the preloading force by each loading means 30 act on each clamping piston 11a, 11b, and these two forces are in the same working directions D1, D2 and in opposite directions.

[0112] By adjusting the value of the preloading force acting on each clamping piston 11a, 11b, it is possible to correct any difference in the frictional forces acting on the clamping pistons themselves. Thereby, the clamping pistons 11a, 11b use substantially the same amount of time to apply pressure, and their respective gripping jaws 7a, 7b can touch the workpiece substantially simultaneously.

[0113] For this specific purpose, the friction compensation assemblies 30, 31 are provided with adjustment means 31 for adjusting the preloading force, which is associated with the bottom walls 18a, 18b and / or the clamping pistons 11a, 11b and is adapted to adjust the distance between the bottom walls 18a, 18b and the associated clamping pistons 11a, 11b in the release configuration.

[0114] Preferably, the adjustment means 31 is associated with the bottom walls 18a, 18b.

[0115] Accordingly, the adjustment means 31 enables the first bottom wall 18a to move closer to / away from the first clamping piston 11a, and the second bottom wall 18b to move closer to / away from the second clamping piston 11b, proportionally increasing / decreasing the compression of each of the first loading element 32a and the second loading element 32b.

[0116] It is easy to understand how to increase / decrease the preloading force applied to the respective clamping pistons 11a, 11b by the greater compression / smaller compression of the load elements 32a, 32b.

[0117] Therefore, once it is determined that either one of the two gripping jaws 7a, 7b has finished its stroke first, it is sufficient to adjust the adjusting means 31 accordingly, that is, by increasing the preloading force acting on the slower gripping jaws 7a, 7b or decreasing the preloading force acting on the faster gripping jaws 7a, 7b.

[0118] Finally, the adjusting means 31 makes it possible to vary the resultant force acting on the clamping pistons 11a, 11b and thus the gripping jaws 7a, 7b. This embodiment makes it possible to effectively compensate for different frictions acting on the clamping pistons 11a, 11b, regardless of strength and / or difference, with several simple adjustments described below, and to realize the device 1 with accurate, reliable and effective operation.

[0119] Specifically, the adjusting means 31 advantageously comprises: - at least one first adjusting pin 34a which is at least partially arranged in the first inlet chamber 17a and is provided with at least one first abutting portion 35a which coincides with the first bottom wall 18a; and - at least one second adjusting pin 34b which is at least partially arranged in the second inlet chamber 17b and is provided with at least one second abutting portion 35b which coincides with the second bottom wall 18b, and In the release configuration, the adjusting pins 34a, 34b are adjustable in position along the working directions D1, D2, reducing and increasing the distance between the bottom walls 18a, 18b and the clamping pistons 11a, 11b respectively.

[0120] Specifically, the first adjusting pin 34a is aligned with the first working direction D1 and the second adjusting pin 34b is aligned with the second working direction D2.

[0121] As mentioned, each adjustment pin 34a, 34b is adjustable at a position along its respective working direction D1, D2. For this purpose, the adjusting means 31 comprises at least one first adjusting body 36a in which the first adjusting pin 34a is at least partially fitted, and the adjusting means 31 comprises at least one second adjusting body 36b in which the second adjusting pin 34b is at least partially fitted (for this, see FIG. 6).

[0122] Specifically, the adjustment pins 34a, 34b slide along their respective working directions D1, D2 with respect to the corresponding adjustment bodies 36a, 36b.

[0123] To enable such sliding, the adjustment pins 34a, 34b and the adjustment bodies 36a, 36b are connected to each other in a screwed manner.

[0124] This means that the adjustment pins 34a, 34b and the adjustment bodies 36a, 36b are provided with threaded portions related to each other, creating a spiral coupling portion between the first adjustment pin 34a and the first adjustment body 36a, and between the second adjustment pin 34b and the second adjustment body 36b.

[0125] To enable the adjustment pins 34a, 34b to slide with respect to the adjustment bodies 36a, 36b, the first adjustment pin 34a is provided with at least one first adjustable dowel hole 37a, and the second adjustment pin 34b is provided with at least one second adjustable dowel hole 37b.

[0126] Specifically, by acting on the adjustable dowel holes 37a, 37b (e.g., by a special type of adjusting wrench such as an Allen wrench), by compressing / releasing the load elements 32a, 32b, and thus by increasing / decreasing the preloading force acting on the clamping pistons 11a, 11b, it is possible to adjust the positions of the adjustment pins 34a, 34b along their respective working directions D1, D2.

[0127] On the other hand, with respect to the stroke adjustment of the release pistons 12a, 12b, the moving unit 8: - a first return means 38a associated with the first release piston 12a; and - a second return means 38b associated with the second release piston 12b, is provided, The release pistons 12a, 12b are movable from the retracted position to the extended position by filling the respective introduction chambers 20a, 20b with pressurized fluid. The return means 38a, 38b are adapted to move the release pistons 12a, 12b from the extended position to the retracted position by discharging the pressurized fluid from the respective introduction chambers 20a, 20b.

[0128] Specifically: - The first return means 38a comprises at least one elastically compressible first return element 39a, which is arranged to abut against the first release piston 12a and at least one abutting portion 40a in the base body 2; - The second return means 38b comprises at least one elastically compressible second return element 39b, which is arranged to abut against the second release piston 12b and at least one second abutting portion 40b in the base body 2.

[0129] In fact, the return elements 39a, 39b are of the spring type, such as a coil spring for example.

[0130] From the foregoing description, it is easy to understand that the return elements 39a, 39b are more strongly compressed (i.e., while simultaneously filling the introduction chambers 20a, 20b and emptying the inlet chambers 17a, 17b) when the release pistons 12a, 12b move forward from the retracted position to the extended position, and apply an increased force to the release pistons 12a, 12b.

[0131] However, these forces are less than the propulsive forces applied to the release pistons 12a, 12b by the pressurized fluid, so that the release pistons 12a, 12b can move forward from the retracted position to the extended position.

[0132] In this cycle, the driving force applied to the first release piston 12a by the pressurized fluid causes the first release piston 12a to push the first clamping piston 11a along the first release direction R1. That is, the first clamping piston 11a is moved away from the first sliding portion 9a and moved closer to the first bottom wall 18a.

[0133] Similarly, the driving force applied to the second release piston 12b by the pressurized fluid causes the second release piston 12b to push the second clamping piston 11b along the second release direction R2. That is, the clamping piston 11b is moved away from the second sliding portion 9b and the first sliding portion 9b is moved closer to the second bottom wall 18b.

[0134] After the pressurized fluid is discharged from the introduction chambers 20a, 20b and after the driving force of the release pistons 12a, 12b stops, the elastic energy stored by the return elements 39a, 39b is no longer balanced by any force. Therefore, by sliding them along their respective clamping directions B1, B2, the elastic energy is released by the release pistons 12a, 12b, returning the release pistons 12a, 12b to their storage positions.

[0135] From the previous explanation, it is clear that the release pistons 12a, 12b and the clamping pistons 11a, 11b are of the single-acting piston type.

[0136] Regarding the above-mentioned contact portions 40a, 40b, it should be made clear that the moving unit 8 includes at least one first support body 41a of the first release piston 12a, and the first contact portion 40a is accurately provided thereon.

[0137] Similarly, the moving unit 8 includes at least one second support body 41b of the second release piston 12b, and the second contact portion 40b is accurately provided thereon.

[0138] Specifically, the first support body 41a includes at least one first support hole 42a formed in the first abutting portion 40a, in which the first release piston 12a slides.

[0139] Similarly, the second support body 41b includes at least one second support hole 42b formed in the second abutting portion 40b, in which the second release piston 12b slides.

[0140] Specifically, the first support body 41a is made hollow and defines, within itself, at least one tubular portion 43a bounded at the bottom by the first abutting portion 40a, in which the first return element 39a is at least partially contained.

[0141] Furthermore, the second support body 41b is made hollow and defines, within itself, at least one tubular portion 43b bounded at the bottom by the second abutting portion 40b, in which the second return element 39b is at least partially contained.

[0142] Here, providing the return means 38a, 38b for the release pistons 12a, 12b is a somewhat advantageous technical means for enabling a delicate adjustment of the preloading force acting on the clamping pistons 11a, 11b and thereby realizing the device 1 with an accurate and orderly operation, which is worth explaining.

[0143] In fact, the spring force applied by the return elements 39a, 39b to the release pistons 12a, 12b enables the release pistons 12a, 12b to return from the extended position to the retracted position completely independently, that is, without any intervention of the clamping pistons 11a, 11b, after the pressurized fluid is released from the introduction chambers 20a, 20b.

[0144] In other words, the only components that play the role of applying the force necessary to return the release pistons 12a, 12b from the extended position to the retracted position are precisely the return elements 39a, 39b, and thus not the clamping pistons 11a, 11b.

[0145] If not, i.e., if there are no return means 38a, 38b, the preloading force applied to the clamping pistons 11a, 11b by the load elements 32a, 32b must be sufficient to also displace the release pistons 12a, 12b together with the sliding parts 9a, 9b and, furthermore, to return the release pistons 12a, 12b from the extended position (corresponding to the release configuration) to the retracted position (corresponding to the clamping configuration) along their respective clamping directions B1, B2.

[0146] In the case of the present invention, on the other hand, the preloading force generated by the load means 30 only needs to compensate for the friction acting on the release pistons 12a, 12b. As a result, there is little adjustment made to the load means 30 and it is of a generally limited magnitude, and thus the load means 30 can effect a delicate adjustment to the clamping pistons 11a, 11b.

[0147] By enabling the release pistons 12a, 12b to be returned independently from the extended position to the retracted position, the return means 38a, 38b clearly act in synergy with the friction compensation assemblies 30, 31, enabling smooth, accurate, and effective adjustment of the operation of the gripping means 7.

[0148] The technical device described as a whole is in line with the device 1 devised so far, which is completely versatile in its use, has an effective and precise operation, and thus it can be used to clamp a workpiece to a machine tool with high accuracy and reproducibility.

[0149] In fact, it has been confirmed that the present invention described achieves the intended purpose.

[0150] Specifically, it is emphasized that the special means for providing the friction compensation means makes it possible to substantially simultaneously hold the gripping jaws stationary against the workpiece, i.e., to ensure that the clamping pistons are pressurized at the same timing.

[0151] Thus, it is clearly possible to realize a device for clamping a workpiece to a machine tool, with an accurate and reliable operation that enables stable clamping to the machine tool without deforming the workpiece.

Claims

Claim 1 A device (1) for clamping a workpiece to a machine tool, comprising: at least one base body (2) that can be fixed to the machine tool; holding means (7) for the workpiece to be machined, associated with the base body (2), comprising at least one first holding jaw (7a) and at least one second holding jaw (7b), the holding jaws (7a, 7b) being movable between at least one clamping configuration in which the holding jaws (7a, 7b) approach each other and at least one release configuration in which the holding jaws (7a, 7b) are moved away from each other with respect to the clamping configuration; at least one moving unit (8) associated with the base body (2) and adapted to move the holding means (7) between the clamping configuration and the release configuration, at least one first sliding part (9a) that slides along at least one first working direction (D1) and is associated with the first holding jaw (7a); at least one first clamping piston (11a) operatively associated with the first sliding part (9a) and movable along at least one first clamping direction (B1) such that the first sliding part (9a) and the first holding jaw (7a) move closer to the second holding jaw (7b) by the driving force of at least one pressurized fluid; at least one first release piston (12a) operatively associated with the first sliding part (9a) and movable along at least one first release direction (R1) opposite to the first clamping direction (B1) such that the first sliding part (9a) and the first holding jaw (7a) move away from the second holding jaw (7b) by the driving force of the pressurized fluid; at least one second sliding part (9b) that slides along at least one second working direction (D2) parallel to the first working direction (D1) and is associated with the second holding jaw (7b); At least one second clamping piston (11b) that is operably associated with the second sliding part (9b) and, by the propulsive force of the pressurized fluid, enables the second sliding part (9b) and the second gripping jaw part (7b) to move along at least one second clamping direction (B2) in which they move closer to the first gripping jaw part (7a). At least one second clamping piston (11b) that is movable to enable sliding. At least one second release piston (12b) that is operably associated with the second sliding part (9b) and, by the propulsive force of the pressurized fluid, enables the second sliding part (9b) and the second gripping jaw part (7b) to move along at least one second release direction (R2) that is opposite to the second clamping direction (B2) and away from the first gripping jaw part (7a). At least one second release piston (12b) that is movable to enable sliding. At least one moving unit (8) that also includes. Comprises. Here, the device (1) is. The device (1) is characterized in that the moving unit (8) comprises at least one friction compensation assembly (30, 31) associated with the clamping pistons (11a, 11b).

2. The friction compensation assembly (30, 31) comprises a first loading means (30a) associated with the first clamping piston (11a) and a second loading means (30b) associated with the second clamping piston (11b), and the loading means (30) is adapted to apply at least one preloading force to the clamping pistons (11a, 11b) in a direction that is substantially parallel to the working directions (D1, D2) and coincides with the clamping directions (B1, B2). The device (1) according to claim 1.

3. The moving unit (8) is. At least one first inlet chamber (17a) of the pressurized fluid bounded by the first clamping piston (11a) and at least one first bottom wall (18a), and At least one second inlet chamber (17b) of the pressurized fluid bounded by the second clamping piston (11b) and at least one second bottom wall (18b), Comprises and. The first loading means (30a) comprises at least one elastically compressible first loading element (32a) arranged to abut against the first bottom wall (18a) and the first clamping piston (11a). The second loading means (30b) comprises at least one elastically compressible second loading element (32b) arranged to abut against the second bottom wall (18b) and the second clamping piston (11b). Device (1) according to claim 2, characterized in that it is as defined above.

4. The friction compensation assembly (30, 31) comprises adjustment means (31) for adjusting the preloading force associated with the bottom wall (18a, 18b) and / or the clamping piston (11a, 11b), and is adapted to adjust the distance between the bottom wall (18a, 18b) and the associated clamping piston (11a, 11b) in the release configuration. Device (1) according to claim 3, characterized in that it is as defined above.

5. The adjustment means (31) comprises at least one first adjustment pin (34a) at least partially arranged within the first inlet chamber (17a) and provided with at least one first abutment (35a) that coincides with the first bottom wall (18a), and at least one second adjustment pin (34b) at least partially arranged within the second inlet chamber (17b) and provided with at least one second abutment (35b) that coincides with the second bottom wall (18b). Comprising The adjustment pins (34a, 34b) are adjustable to a predetermined position along the working directions (D1, D2). Device (1) according to claim 4, characterized in that it is as defined above.

6. The moving unit (8) comprises at least one first introduction chamber (20a) of the pressurized fluid delimited by the first release piston (12a) and at least one first bottom surface (21a), at least one second introduction chamber (20b) of the pressurized fluid delimited by the second release piston (12b) and at least one second bottom surface (21b), first return means (38a) associated with the first release piston (12a), and second return means (38b) associated with the second release piston (12b). Comprising The release pistons (12a, 12b) are movable from the retracted position to the extended position by filling the respective introduction chambers (20a, 20b) with the pressurized fluid, and the return means (38a, 38b) is adapted to move the release pistons (12a, 12b) from the extended position to the retracted position by discharging the pressurized fluid from the respective introduction chambers (20a, 20b). The device (1) according to any one of claims 1 to 5, characterized in that.

7. The first return means (38a) comprises at least one elastically compressible first return element (39a), which is arranged to abut against the first release piston (12a) and at least one abutment portion (40a) on the base body (2), and The second return means (38b) comprises at least one elastically compressible second return element (39b), which is arranged to abut against the second release piston (12b) and a second abutment portion (40b) on the base body (2), The device (1) according to claim 6, characterized in that.

8. Blocking means (23, 24) associated with the base body (2) and comprising at least one blocking piston (23), the blocking piston (23) being movable along at least one blocking direction (A) substantially orthogonal to the working directions (D1, D2) and adapted to clamp the sliding parts (9a, 9b) by friction in the clamping configuration. The device (1) according to any one of claims 1 to 7, characterized in that.

9. The first sliding part (9a) and the second sliding part (9b) each comprise at least one first recessed part (26a) and at least one second recessed part (26b), the recessed parts (26a, 26b) being juxtaposed with each other and defining at least one internal space (S) between the sliding parts (9a, 9b); The blocking piston (23) is provided with at least one enlarged part (27) which can be inserted into the space (S) to clamp the sliding parts (9a, 9b); The device (1) according to claim 8, characterized in that.

10. The blocking means (23, 24) comprises at least one elastically compressible propulsion element (24) positioned between the blocking piston (23) and the base body (2) and adapted to impart at least one direct propulsion force along the blocking direction (A) to the blocking piston (23), characterized in that it is a device (1) according to claim 9.

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