Device for clamping workpiece on machine tool

Abstract

The invention relates to a device (1) for clamping a workpiece on a machine tool, comprising: a base body (2); clamping means (7) associated with the base body (2) and movable between a clamping configuration and a release configuration; -a movement unit (8) associated with the base body (2) and adapted to move the gripping device (7) between a clamping configuration and a release configuration, comprising:-a first slide (9a); -a first clamping piston (11a) associated with the first slide (9a); -a first release piston (12a) associated with the first slide (9a); a second slide (9b); -a second clamping piston (11b) associated with the second slide (9b); -a second release piston (12b) associated with the second slide (9b); and-a friction compensation assembly (30, 31) associated with the clamping piston (11a, 11b).

Description

Technical Field

[0001] The invention relates to a device for clamping a workpiece on a machine tool. Background Art

[0002] As is known, in the series production of mechanical workpieces to be machined at machine tools, highly automated systems are widely used, in which one or more machine tools are electronically controlled by a processing and control unit and one or more anthropomorphic robots bring the workpiece to be machined to the machine tool, where special clamping devices (hydraulic or pneumatic) take over the workpiece and clamp it in the appropriate position to allow it to be machined.

[0003] When machining is completed, the clamping device releases the machined workpiece and the workpiece is removed by the robot again.

[0004] One specialized type of clamping device achieves its purpose with the aid of a pair of jaws that are moved by a hydraulic actuator between a clamping configuration, in which the jaws move toward each other and clamp the workpiece, and a releasing configuration, in which the jaws move away from each other and release the workpiece.

[0005] Specifically, the hydraulic drive comprises two moving assemblies, each of which is associated with a corresponding claw and comprises: a slide which is attached to the claw and is slidably locked with the claw in the working direction; and - Two hydraulic pistons mounted in corresponding cylinders, between which a slide is positioned, the slide sliding in a working direction due to the operation of the hydraulic pistons.

[0006] In the present case, due to the thrust exerted by the pressurized hydraulic fluid, the piston allows the slide to slide along a path opposite to their relative working direction in order to move the jaws attached to the slide between the clamping configuration and the releasing configuration.

[0007] In practice, two pistons out of a total of four pistons are operable to push the claws towards each other, thereby arranging them in a clamping configuration, while the other two pistons are operable to push the claws away from each other, thereby arranging them in a releasing configuration.

[0008] Since the above-mentioned piston is of the hydraulic type, the known clamping device is also provided with a dedicated seal (for example of the O-ring type) which is fitted on the piston itself at a predetermined position in order to prevent undesired leakage of the hydraulic fluid under pressure.

[0009] In detail, these seals are designed to flatten during assembly of the pistons in their respective cylinders, thereby expanding in a radial mode; thanks to this characteristic, the seals adhere to the cylinder wall and achieve a practically watertight seal inside the cylinder.

[0010] In this context, it is important to note the fact that the jaws must be able to exert even very large clamping forces on the workpiece.

[0011] This need is particularly evident, for example, in industry where the continuous need to optimize production cycles has led to the use of tools operating at very high speeds, thereby unloading very large forces and vibrations on the workpiece, which must be counteracted by the clamping device.

[0012] In many industries, the use of particularly lightweight materials such as aluminum is also becoming more and more common, however, these materials do not ensure the same strength during processing on machine tools as materials such as cast iron and steel.

[0013] Therefore, each time a new workpiece is mounted on the machine, the jaws must, in addition to applying very high forces, rest on the workpiece with great accuracy, precision and in a repeatable manner; otherwise, in fact, the enormous forces exerted by the jaws may cause the workpiece to deform, which impairs the machining quality and risks obtaining a workpiece out of tolerance.

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

[0015] In this regard, it should be particularly taken into account that the seals mounted on the hydraulic pistons always exert a certain resistance to the sliding of the hydraulic pistons, and that this resistance often has different strengths from piston to piston.

[0016] In fact, the resistance offered by a seal to sliding is highly dependent on the degree of crushing of the seal, and indeed, even where seals are apparently identical to one another and are compressed to approximately the same degree, crushing can demonstrate a degree of variability from seal to seal.

[0017] The different friction forces obviously lead to different pressurization times for the hydraulic pistons, with the result that one of the two jaws, in particular the one associated with the piston on which the less friction acts, eventually rests on the workpiece before the other.

[0018] This inaccuracy in operation proves to be very inconvenient, since it causes the jaw that first contacts the workpiece to apply particularly strong forces to the workpiece, which puts its structural integrity at serious risk.

[0019] In view of this, it will be readily appreciated that the jaw clamping apparatus is susceptible to improvement. Summary of the invention

[0020] The main purpose of the present invention is to devise a device for clamping a workpiece on a machine tool with a precise and reliable operation, which allows the jaws to be placed on the workpiece substantially simultaneously, thus clamping the workpiece stably on the machine tool without deforming it.

[0021] Another object of the present invention is to devise a device for clamping a workpiece on a machine tool that allows overcoming the aforementioned drawbacks of the prior art within the framework of a simple, rational, easy to use and efficient as well as inexpensive solution.

[0022] This object is achieved by a device for clamping a workpiece on a machine tool having the features of claim 1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Other characteristics and advantages of the invention will become more apparent from the description of a preferred but not exclusive embodiment of a device for clamping a workpiece on a machine tool, illustrated by way of indicative but not limiting example in the table of the accompanying drawings, in which: Figure 1 is an axonometric view of the apparatus according to the invention; Figure 2 is an exploded view of an apparatus according to the present invention; Figure 3 is a top view of an apparatus according to the present invention; Figure 4 is a front view of the device according to the present invention; Figure 5 is the device according to the invention along Figure 3 A cross-sectional view of the VV plane; and Figure 6 is the device according to the invention along Figure 4 Cross-sectional view of the VI-VI plane. DETAILED DESCRIPTION

[0024] With particular reference to the drawings, reference numeral 1 generally designates an apparatus for clamping a workpiece on a machine tool.

[0025] The device 1 for clamping a workpiece on a machine tool firstly comprises at least one basic body 2 which can be fastened to the machine tool.

[0026] The basic body 2 in turn comprises at least a central block 3 , at least a first side wall 4 and a second side wall 5 , the latter being coupled to the central block 3 in a removable manner.

[0027] Specifically, in the assembled configuration of the device 1 whose constituent parts are assembled to each other, the central block 3 is coupled to the side walls 4 , 5 by inserting a plurality of connecting elements 6 (eg, screws, etc.).

[0028] Specifically, the first side wall 4 and the second side wall 5 include first and second connection holes 4 a , 5 a , respectively, into which the connection element 6 can be fitted to connect the side walls 4 , 5 to the center block 3 .

[0029] Thus, in the event of the need for maintenance / replacement of one or more constituent parts of the device 1 , the connecting element 6 is simply removed and, by doing so, one or both of the side walls 4 , 5 are separated from the central block 3 .

[0030] The device 1 also includes: - a clamping device 7 for the workpiece to be machined, associated with the base body 2, comprising at least a first clamping jaw 7a and at least a second clamping jaw 7b and movable between at least one clamping configuration of the workpiece, in which the jaws 7a, 7b are brought closer to each other, and at least one release configuration of the workpiece, in which the jaws 7a, 7b are moved away from each other relative to the clamping configuration; - at least one movement unit 8 associated with the base body 2 and suitable for moving the clamping device 7 between a clamping configuration and a release configuration, comprising: at least one first slide 9a which slides along at least one first working direction D1 and is associated with the first jaw 7a; and - at least one second slide 9b which slides along at least a second working direction D2 parallel to the first working direction D1 and which is associated with the second jaw 7b.

[0031] In particular, the clamping jaws 7a, 7b are attached to respective slides 9a, 9b and are slidingly locked together with the latter along their respective working directions D1, D2.

[0032] Furthermore, slides 9 a , 9 b are associated with the central block 3 and are therefore positioned between the two side walls 4 , 5 .

[0033] In this regard, the central block 3 is provided with at least one guide element 10 with which the slides 9a, 9b are associated in a sliding manner along their respective working directions D1, D2.

[0034] Specifically, Figure 2 As can be seen in the figure, the guide element 10 is roughly a cavity cut out in the center block 3 along a direction parallel to the working directions D1, D2, and the slides 9a, 9b are accommodated in the cavity in a sliding manner.

[0035] In particular, the guide element 10 has a configuration that is substantially complementary to that of the slides 9a, 9b and thereby allows the latter to slide smoothly and precisely along their respective working directions D1, D2.

[0036] In order to enable the first sliding member 9a to move along the first working direction D1, the moving unit 8 includes: at least one first clamping piston 11a operatively associated with the first slide 9a and movable due to the thrust of at least one pressurized fluid so as to allow the first slide 9a and the first jaw 7a associated therewith to slide along at least one first clamping path B1 so as to move closer to the second jaw 7b; - at least one first release piston 12a operatively associated with the first slide 9a and movable due to the thrust of the pressurized fluid to allow the first slide 9a and the first jaw 7a to slide away from the second jaw 7b along at least one first release path R1 opposite to the first clamping path B1.

[0037] In practice, pressurizing the first clamping piston 11a and the first release piston 12a with pressurized fluid causes them to move along opposite paths in the first working direction D1 , ie the first clamping path B1 and the first release path R1 , thereby dragging the first slide 9a and thus the first jaw 7a by sliding.

[0038] At this point it is important to specify that, in the context of the present disclosure, "pressurized fluid" means any fluid, liquid (and therefore ideally incompressible) or gaseous (and therefore compressible), used as a carrier medium for energy transmission in a hydraulic or pneumatic circuit; preferably, the pressurized fluid consists of conventional mineral oil, but alternative embodiments cannot be excluded in which the pressurized fluid may be synthetic oil, vegetable oil, water, air, etc.

[0039] This means that, preferably, the first clamping piston 11a and the first release piston 12a are of the hydraulic piston type, however, it cannot be excluded that the latter may be of, for example, the pneumatic piston type (in case the pressurized fluid is air) or the hydraulic piston type (in case the pressurized fluid is water).

[0040] Furthermore, it is also specified that, considering the presence of different parts in contact with the pressurized fluid in the device 1 , dedicated seals are provided, arranged at different points of the device 1 , and generally indicated by reference numeral 14 for simplicity of representation.

[0041] In the context of the foregoing, the components just mentioned in more detail are described in detail and it can be well explained that the first clamping piston 11 a is at least partially accommodated in the first side wall 4 .

[0042] Similarly, the first release piston 12 a is at least partially housed within the second side wall 5 .

[0043] In this regard, the first side wall 4 and the second side wall 5 are respectively provided with at least a first inner housing 13a in which the first clamping piston 11a is at least partially assembled and at least a second inner housing 13b of the first release piston 12a. The second clamping piston 11b is at least partially assembled in the second inner housing.

[0044] The first housing 13 a and the second housing 13 b roughly represent cylinders, in which the first clamping piston 11 a and the first releasing piston 12 a slide, respectively.

[0045] The mobile unit 8 also includes: at least one second clamping piston 11 b operatively associated with the second slide 9 b and movable due to the thrust of the pressurized fluid to allow the second slide 9 b and the second jaw 7 b to slide along at least one second clamping path B2 and thus move closer to the first jaw 7 a ; - at least one second release piston 12b, which is operatively associated with the second slide 9b and can be moved due to the thrust of the pressurized fluid to allow the second slide 9b and the second clamping jaw 7b to slide along at least one second release path R2 opposite to the second clamping path B2, thereby moving away from the first clamping jaw 7a.

[0046] Indeed, pressurizing the second clamping piston 11b and the second release piston 12b with pressurized fluid causes them to move along opposite paths in the second working direction D2, ie the second clamping path B2 and the second release path R2, thereby dragging the second slide 9b and thus the second jaw 7b by sliding.

[0047] In substantially the same manner as previously described, the second clamping piston 11 b and the second release piston 12 b are preferably of the hydraulic piston type, but it cannot be excluded that they may be of the pneumatic piston (in the case where the pressurized fluid is air) or hydraulic piston (in the case where the pressurized fluid is water) type.

[0048] With regard to the position of the newly introduced components, the second clamping piston 11 b is at least partially accommodated in the first side wall 4 , while the second release piston 12 b is at least partially accommodated in the second side wall 5 .

[0049] In this regard, the first side wall 4 and the second side wall 5 are provided with at least one first inner seat 15a of the first release piston 12a and at least one second inner seat 15b of the second release piston 12b, respectively.

[0050] The first seat 15a and the second seat 15b generally represent cylinders, in which the first release piston 12a and the second release piston 12b slide, respectively.

[0051] Having introduced the main components for the movement of the clamping device 7, it is useful to clarify that in order to arrange the clamping device in a clamping configuration, the first clamping piston 11a moves along a first clamping path B1 in a first working direction D1, thereby allowing the first slide 9a and the first clamping jaw 7a associated therewith to slide in this path.

[0052] At the same time, the second clamping piston 11 b is simultaneously moved along the second clamping path B2 in the second working direction D2 so that the second slide 9 b and the second clamping jaw 7 b associated therewith slide in this path.

[0053] It can be inferred from this that the first clamping path B1 and the second clamping path B2 are opposite to each other.

[0054] Similarly, to arrange the clamping device 7 into the released configuration, the first release piston 12a is moved along a first release path R1 in the first working direction D1 , thereby allowing the first slide 9a and the first clamping jaw 7a associated therewith to slide in this path.

[0055] At the same time, the second release piston 12b also moves along the second release path R2 in the second working direction D2, so that the second slide 9b and the second clamping jaw 7b associated therewith slide in the path.

[0056] It can be inferred from this that the first release path R1 and the second release path R2 are opposite to each other.

[0057] It can be seen that the first clamping path B1 and the second releasing path R2 have the same path, and the second clamping path B2 and the first releasing path R1 also have the same path.

[0058] In order to reduce the friction acting on the slides 9a, 9b during the sliding just described, the mobile unit 8 advantageously comprises at least one lubrication circuit G connected to the first slide 9a and the second slide 9b, suitable for lubricating the latter with at least one lubricating compound (for example a high-viscosity lubricant of grease type, etc.).

[0059] In particular, the lubrication circuit G is provided with at least one external access opening 16 cut into the side of the central block 3, through which the lubrication compound can be inserted.

[0060] The lubrication circuit thus enables the slides 9a, 9b to slide efficiently along their respective working directions D1, D2, significantly reducing the friction acting on the latter.

[0061] Continuing with the detailed description of the mobile unit 8, it is important to add that it comprises: at least one first inlet chamber 17a for pressurized fluid, delimited by a first clamping piston 11a and at least one first bottom wall 18a; and - at least one second inlet chamber 17b for pressurized fluid, delimited by a second clamping piston 11b and by at least one second bottom wall 18b.

[0062] In particular, the mobile unit 8 also comprises at least a first circulation line L1 of pressurized fluid, connected to the first and second inlet chambers 17a, 17b and suitable for at least partially filling the latter with pressurized fluid.

[0063] In particular, the first circulation line L1 is provided with at least one associated first external supply inlet 19 formed on a side of the central block 3 and usable for at least partially filling the first circulation line L1 with pressurized fluid.

[0064] Therefore, in order to arrange the clamping device 7 in the clamping configuration, pressurized fluid is introduced into the first circulation line L1 through the first supply inlet 19 .

[0065] In this way, pressurized fluid is delivered to the first and second inlet chambers 17a and 17b, thereby exerting thrust on the first and second clamping pistons 11a and 11b, which allows the first slider 9a to slide in the first clamping path B1 and the second slider 9b to slide in the second clamping path B2.

[0066] Again, the mobile unit 8 comprises: - at least one first introduction chamber 20a of the pressurized fluid, delimited by the first release piston 12a and by at least one first bottom surface 21a; - at least one second introduction chamber 20b for pressurized fluid, delimited by the second release piston 12b and by at least one second bottom surface 21b.

[0067] Very similar to what has been described above, the mobile unit 8 also comprises at least one second circulation circuit L2 of pressurized fluid, connected to the first and second introduction chambers 20a, 20b and suitable for at least partially filling the latter with pressurized fluid.

[0068] In particular, the second circulation line L2 is provided with at least one associated second external supply inlet 22 formed on the side of the central block 3 and usable for at least partially filling the second circulation line L2 with pressurized fluid.

[0069] Therefore, in order to arrange the clamping device 7 into the released configuration, pressurized fluid is introduced into the second circulation line L2 through the second supply inlet 22 .

[0070] In this case, pressurized fluid is delivered to the first and second introduction chambers 20a and 20b, thereby applying thrust to the first and second release pistons 12a and 12b, which allows the first slider 9a to slide in the first release path R1 and the second slider 9b to slide in the second release path R2.

[0071] In switching from the release configuration to the clamping configuration, the pressurized fluid is exhausted from the intake chambers 20a, 20b, conveyed from the second circulation line L2 to the first circulation line L1 (eg by means of a dedicated hydraulic connection) and finally supplied to the inlet chambers 17a, 17b.

[0072] In this way, by reversing the sliding path of the slides 9a, 9b (i.e., by stopping their sliding along the release paths R1, R2 and applying sliding along the clamping paths B1, B2), the thrust acting on the release pistons 12a, 12b can be eliminated and transmitted to the clamping pistons 11a, 11b.

[0073] In the opposite case, ie in switching from the clamping configuration to the releasing 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 (eg by means of a dedicated hydraulic connection) and finally supplied to the inlet chambers 20a, 20b.

[0074] In this way, by reversing the sliding path of the slides 9a, 9b (i.e., stopping their sliding along the clamping paths B1, B2 and applying sliding along the release paths R1, R2), the thrust acting on the clamping pistons 11a, 11b can be eliminated and transmitted to the release pistons 12a, 12b.

[0075] In order to ensure that the workpiece remains securely fixed when the clamping device 7 is in the clamping configuration, the device 1 comprises stop means 23 , 24 associated with the basic body 2 .

[0076] In this regard, the central block 3 is provided with at least one recess 25 in which the stop means 23 , 24 are arranged.

[0077] In particular, the stop means 23, 24 comprise at least one stop piston 23 movable along at least one stop direction A substantially orthogonal to the working directions D1, D2 and adapted to clamp the slides 9a, 9b by friction in a clamping configuration.

[0078] Specifically, the stopping direction A is orthogonal to the first working direction D1 and the second working direction D2.

[0079] According to a preferred embodiment, the first slide 9a and the second slide 9b comprise at least one first recess 26a and at least one second recess 26b, respectively, wherein the recesses 26a, 26b are juxtaposed to each other to define at least one inner space S between the slides 9a, 9b.

[0080] like Figure 2 As can be seen in the figure, the space S expands in a direction parallel to the working directions D1 and D2.

[0081] Furthermore, the stop piston 23 is provided with at least one enlarged portion 27 which can be inserted into the space S to clamp the slides 9a, 9b (see in this regard Figure 5 ).

[0082] Specifically, the enlarged portion 27 has a so-called “dovetail” configuration.

[0083] In order to insert the enlarged portion 27 into the space S and clamp it, in this case, the sliding members 9a, 9b, the stopping devices 23, 24 include at least one elastically compressible thrust element 24, which is positioned between one end of the stopping piston 23 and the base 2 and is suitable for exerting at least one direct thrust on the stopping piston 23 along the stopping direction A.

[0084] Exactly, if Figure 5 As can be seen in FIG. 2 , the thrust element 24 is positioned between one end of the stop piston 23 and at least one bottom 28 of the base body 2 , which is arranged to close the recess 25 , thereby isolating it from the outside.

[0085] Conveniently, the thrust element 24 is of the spring type, for example a coil spring.

[0086] In order to move the enlargement 27 away from the space S and by doing so release the slides 9a, 9b, the stop means 23, 24 comprise a relative third circulation line L3 of pressurized fluid.

[0087] In particular, the third circulation line L3 is provided with at least an associated third external supply inlet 29 which is formed on a side of the central block 3 and which can be used to at least partially fill the third circulation line L3 with pressurized fluid.

[0088] The third circulation line L3 terminates at the end of the stop piston 23 opposite to the thrust element 24; thus, when the pressurized fluid moves closer to the bottom 28, the force generated by the pressurized fluid compresses the thrust element 24, thereby reducing its length and thereby allowing the expansion portion 27 to disengage from the space S.

[0089] After the pressurized fluid has been discharged from the third circulation line L3 , the compressive force exerted by the pressurized fluid on the thrust element 24 disappears, so that the latter pushes the stop piston 23 in the stop direction A, thereby inserting its enlarged portion 27 into the space S.

[0090] From what has just been described, it is easy to understand that in the release configuration, pressurized fluid is introduced along the second circulation line L2 (so that it can fill the introduction chambers 20a, 20b) and along the third circulation line L3 (so that it can disengage the expansion part 27 from the space S).

[0091] On the other hand, in the clamped configuration, pressurized fluid is introduced only along the first circulation line L1 (so that it can fill into the chambers 17 a , 17 b , and the expansion 27 can fit into the space S).

[0092] It is emphasized that providing the slides 9a, 9b with stop means 23, 24 in the clamping arrangement proves to be a very advantageous technical measure in order to ensure that the clamping jaws 7a, 7b remain firmly gripped on the workpiece.

[0093] It is easy to understand how this fact ensures efficient, precise and accurate operation of the device 1 by avoiding the possibility of undesired movement of the jaws 7a, 7b in the clamping configuration.

[0094] According to the invention, the movement unit 8 comprises at least one friction compensation assembly 30 , 31 associated with the clamping piston 11 a , 11 b .

[0095] In particular, the friction compensation assembly 30 , 31 is adapted to compensate for the friction acting on the clamping piston 11 a , 11 b when it slides along a clamping path B1 , B2 in the associated working direction D1 , D2 .

[0096] In fact, as explained, the presence of the seal 14 results in the presence of friction forces of different strengths between the clamping pistons 11 a , 11 b and therefore in a serious possibility of one of the jaws 7 a , 7 b striking the workpiece before the other.

[0097] As will be explained further in the remainder of this disclosure, the provision of friction compensation assemblies 30 , 31 completely eliminates this inconvenient possibility by allowing thus to obtain a device 1 capable of perfectly and simultaneously placing its jaws 7 a , 7 b on the workpiece, clamping it stably on the machine tool without deforming it.

[0098] Starting with a detailed description of the friction compensation assembly 30, 31, it is first preferred that it includes a first loading device 30a associated with the first clamping piston 11a and a second loading device 30b associated with the second clamping piston 11b, wherein the loading device 30 is suitable for applying at least one preloading force on the clamping pistons 11a, 11b, and the preloading force has a direction substantially parallel to the working directions D1, D2 and a path consistent with the clamping paths B1, B2.

[0099] This means that the first loading device 30a applies a preload force on the first clamping piston 11a parallel to the first working direction D1 and having a path consistent with the first clamping path B1, while the second loading device 30b applies a preload force on the second clamping piston 11b parallel to the second working direction D2 and having a path consistent with the second clamping path B2.

[0100] Specifically: - the first loading device 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; and The second loading means 30b comprise at least one elastically compressible second loading element 32b arranged to abut against the second bottom wall 18b and the second clamping piston 11b.

[0101] Even more specifically, the first clamping piston 11 a defines at least a first barrel cavity 33 a in which the first loading element 32 a is at least partially accommodated.

[0102] Similarly, the second clamping piston 11 b defines at least a second cylinder cavity 33 b in which the second loading element 32 b is at least partially accommodated.

[0103] In practice, the first loading element 32a is arranged to stop on the bottom of the first barrel cavity 33a and on the first bottom wall 18a, while the second loading element 32b is arranged to stop on the bottom of the second barrel cavity 33b and on the second bottom wall 18b.

[0104] That is, it is specified that the first and second loading members 32a and 32b are of a spring type, such as a coil spring.

[0105] Thus, the preload force generated by the first loading device 30a on the first clamping piston 11a and by the second loading device 30b on the second clamping piston 11b corresponds to the spring force stored by the first loading element 32a and the second loading element 32b respectively due to their compression.

[0106] It is important to note that the preload force acting on the first clamping piston 11a and the second clamping piston 11b reduces the pressing time of the first clamping piston and the second clamping piston (i.e. the speed at which they bring the clamping device 7 from the clamping / release configuration to the release / clamping configuration) to an extent proportional to their strength.

[0107] This means that as the preload force acting on the first and second clamping pistons 11a and 11b increases, the time required for the first and second clamping pistons to complete their stroke within the first and second housings 13a and 13b, respectively, decreases, and vice versa.

[0108] In fact, there is an inversely proportional relationship between the preload force acting on the clamping pistons 11 a , 11 b and the pressurization time of the clamping pistons.

[0109] It is easy to understand that the friction forces acting on the various clamping pistons 11 a , 11 b certainly have different strengths between them, but still have in common the fact that they have directions opposite to their respective preload forces.

[0110] In other words, a certain friction force due to the seal 14 and a preload force due to the corresponding loading device 30 act on each clamping piston 11a, 11b, these two forces being located in the same working direction D1, D2 and having opposite paths.

[0111] It can be seen that adjusting the value of the preload force acting on each clamping piston 11a, 11b allows any differences between the friction forces acting on the clamping pistons themselves to be corrected; thereby, the clamping pistons 11a, 11b can spend approximately the same amount of time to be pressurized, so that their respective clamping jaws 7a, 7b are located on the workpiece at approximately the same time.

[0112] For this particular purpose, the friction compensation assembly 30, 31 comprises an adjustment device 31 for adjusting the preload force, which is associated with the bottom wall 18a, 18b and / or the clamping piston 11a, 11b and is suitable for adjusting the distance between the bottom wall 18a, 18b and the associated clamping piston 11a, 11b in the released configuration.

[0113] Preferably, adjustment means 31 are associated with the bottom walls 18a, 18b.

[0114] Thus, the adjustment device 31 allows 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, thereby proportionally increasing / decreasing the compression of the first loading element 32a and the second loading element 32b, respectively.

[0115] It is easy to understand how a greater / lesser compression of the loading elements 32a, 32b results in a greater / lesser preload force exerted by them on the respective clamping piston 11a, 11b.

[0116] Therefore, once it has been determined which of the two clamping jaws 7a, 7b ends its stroke first, it is sufficient to adjust the adjustment device 31 accordingly, i.e. to increase the preload force on the slower clamping jaw 7a, 7b or to reduce the preload force on the faster clamping jaw 7a, 7b.

[0117] Finally, the adjustment device 31 makes it possible to vary the resultant force acting on the clamping pistons 11a, 11b and therefore on the clamping jaws 7a, 7b; this embodiment conveniently makes it possible to effectively compensate for the different frictions acting on the clamping pistons 11a, 11b, regardless of their strengths and / or differences, using a few simple adjustments described below, thereby making it possible to obtain a device 1 with precise, reliable and efficient operation.

[0118] Specifically, the adjustment device 31 advantageously comprises: at least one first regulating pin 34a arranged at least partially inside the first inlet chamber 17a and provided with at least one first abutment portion 35a coinciding with the first bottom wall 18a; and at least one second regulating pin 34b arranged at least partially inside the second inlet chamber 17b and provided with at least one second abutment portion 35b coinciding with the second bottom wall 18b; The position of the adjustment pins 34a, 34b is adjustable along the working direction D1, D2 in order to respectively reduce and increase the distance between the bottom wall 18a, 18b and the clamping piston 11a, 11b in the released configuration.

[0119] Specifically, the first adjustment pin 34 a is aligned with the first working direction D1 , and the second adjustment pin 34 b is aligned with the second working direction D2 .

[0120] As described above, the positions of the respective adjustment pins 34a, 34b can be adjusted along their respective working directions D1, D2; for this purpose, the adjustment device 31 includes at least a first adjustment body 36a and at least a second adjustment body 36b, the first adjustment pin 34a is at least partially assembled in the first adjustment body, and the second adjustment pin 34b is at least partially assembled in the second adjustment body (see in this regard Figure 6 ).

[0121] Specifically, the adjustment pins 34a, 34b slide relative to the corresponding adjustment bodies 36a, 36b along their respective working directions D1, D2.

[0122] In order to realize such sliding movement, the adjustment pins 34a, 34b and the adjustment bodies 36a, 36b are coupled to each other in a threaded manner.

[0123] This means that the adjusting pins 34a, 34b and the adjusting bodies 36a, 36b are provided with mutually associated threaded portions to form a screw coupling between the first adjusting pin 34a and the first adjusting body 36a and between the second adjusting pin 34b and the second adjusting body 36b.

[0124] In order to allow the adjustment pins 34a, 34b to slide relative to the adjustment bodies 36a, 36b, the first adjustment pin 34a is provided with at least a first adjustable pin 37a, and the second adjustment pin 34b is provided with at least a second adjustable pin 37b.

[0125] Specifically, by operating the adjustable pins 37a, 37b (with the aid of a special adjustment wrench of, for example, the hexagonal wrench type), the position of the adjustment pins 34a, 34b along the respective working directions D1, D2 can be adjusted by compressing / decompressing the loading elements 32a, 32b and thereby increasing / decreasing the preload force acting on the clamping pistons 11a, 11b.

[0126] On the other hand, regarding the stroke adjustment of the release pistons 12a, 12b, the moving unit 8 comprises: - a first return device 38a associated with the first release piston 12a; - a second return means 38b associated with the second release piston 12b; Wherein, the release pistons 12a, 12b are movable from a retracted position to an extended position due to filling of the respective introduction chambers 20a, 20b with pressurized fluid, and wherein, the return devices 38a, 38b are adapted to move the release pistons 12a, 12b from an extended position to a retracted position due to discharge of pressurized fluid from the respective introduction chambers 20a, 20b.

[0127] Specifically: - the first return means 38a comprises at least one elastically compressible first return element 39a, which is arranged to abut on the first release piston 12a and on at least one first abutment portion 40a of the base body 2; The second return means 38 b comprise at least one elastically compressible second return element 39 b arranged to abut on the second release piston 12 b and on at least one second abutment 40 b of the basic body 2 .

[0128] In practice, the return elements 39a, 39b are of the spring type, for example helical springs.

[0129] From the description just given, it is easy to understand that when the release piston 12a, 12b moves forward from the retracted position to the extended position (i.e., while filling the introduction chamber 20a, 20b and emptying the entry chamber 17a, 17b), the return element 39a, 39b is compressed more and more strongly, thereby applying an increasing force to the release piston.

[0130] However, these forces are smaller than the thrust imparted by the pressurized fluid on the release pistons 12a, 12b, which is why the release pistons are able to move forwards from the retracted position to the extended position.

[0131] In this case, the thrust exerted by the pressurized fluid on the first release piston 12a causes it to push the first clamping piston 11a along the first release path R1 , ie to move it away from the first slide 9a and closer to the first bottom wall 18a.

[0132] Similarly, the thrust exerted by the pressurized fluid on the second release piston 12b causes it to push the second clamping piston 11b along the second release path R2, ie away from the second slide 9b and closer to the second bottom wall 18b.

[0133] After the pressurized fluid has been discharged from the inlet chambers 20a, 20b and its thrust on the release pistons 12a, 12b has ceased, the elastic energy stored by the return elements 39a, 39b is no longer balanced by any force and is therefore released on the release pistons 12a, 12b by sliding the release pistons along their respective clamping paths B1, B2 and returning them to their retracted positions.

[0134] Thus, from the description just given, it is apparent that the release pistons 12a, 12b and the clamping pistons 11a, 11b are of the single-acting piston type.

[0135] With regard to the above-mentioned abutments 40 a , 40 b , it should be specified that the movement unit 8 comprises at least a first support 41 a of the first release piston 12 a , which is provided precisely with the first abutment 40 a .

[0136] Similarly, the mobile unit 8 comprises at least a second support 41 b of the second release piston 12 b , which is precisely provided with a second abutment 40 b .

[0137] Specifically, the first support body 41 a includes at least a first support hole 42 a formed on the first abutment portion 40 a , and the first release piston 12 a slides in the first support hole.

[0138] Similarly, the second support body 41 b includes at least a second support hole 42 b formed on the second abutment portion 40 b , and the second release piston 12 b slides in the second support hole.

[0139] In particular, the first support body 41 a is made hollow and defines within itself at least a first cylindrical portion 43 a , delimited at the bottom by the first abutment 40 a , in which the first return element 39 a is at least partially housed.

[0140] Moreover, the second support body 41 b is made hollow and defines within itself at least a second cylindrical portion 43 b , delimited at the bottom by the second abutment 40 b , in which the second return element 39 b is at least partially housed.

[0141] At this point, it is worth stating that the provision of return means 38a, 38b for the release pistons 12a, 12b proves to be a rather advantageous technical measure to allow fine adjustment of the preload force acting on the clamping pistons 11a, 11b and thus to obtain a device 1 with precise and systematic operation.

[0142] In fact, the spring force exerted by the return elements 39a, 39b on the release pistons 12a, 12b allows the release pistons 12a, 12b to return completely independently from the extended position to the retracted position after the pressurized fluid is released from the inlet chambers 20a, 20b, without having to intervene in any way on the clamping pistons 11a, 11b.

[0143] In other words, the only component responsible for applying the force required to return the release piston 12a, 12b from the extended position to the retracted position is the return element 39a, 39b, and not the clamping piston 11a, 11b.

[0144] Otherwise, i.e. in the absence of return means 38a, 38b, the preload force exerted by the loading elements 32a, 32b on the clamping pistons 11a, 11b must be sufficient to ensure that the latter, together with the slides 9a, 9b, also displace the release pistons 12a, 12b and along their respective clamping paths B1, B2, thereby returning them from the extended position (corresponding to the release configuration) to the retracted position (corresponding to the clamping configuration).

[0145] In the case of the present invention, on the other hand, the preload force generated by the loading device 30 only has to compensate for the friction acting on the release pistons 12a, 12b; therefore, the adjustments made to the loading device 30 are small and have a limited size overall, so that the loading device can fine-tune the clamping pistons 11a, 11b.

[0146] By enabling the release pistons 12a, 12b to be independently returned from the extended position to the retracted position, the return means 38a, 38b obviously cooperate with the friction compensation assemblies 30, 31 to enable smooth, precise and efficient regulation of the operation of the clamping device 7.

[0147] In summary, the technical arrangements described thus far are consistent in designing a device 1 that is absolutely versatile in its use and has an efficient and accurate operation, and can therefore be used to clamp workpieces on machine tools with extreme precision and repeatability.

[0148] It has in fact been established that the described invention achieves the intended objects.

[0149] It is particularly important to emphasize that the specific means of arranging the friction compensation device makes it possible to place the clamping jaws on the workpiece approximately simultaneously, ie ensure that the clamping pistons are pressurized at the same time.

[0150] In this way, it is evident that it is possible to obtain a device for clamping a workpiece on a machine tool with precise and reliable operation, which allows the workpiece to be clamped stably on the machine tool without deforming it.

Claims

1. Equipment (1) for clamping a workpiece on a machine tool, comprising: - at least one base body (2) which can be fastened to a machine tool; - a clamping device (7) for a workpiece to be machined, associated with the base body (2), comprising at least one first clamping jaw (7a) and at least one second clamping jaw (7b) and being movable between at least one clamping configuration of the workpiece, in which the clamping jaws (7a, 7b) are brought closer to each other, and at least one release configuration of the workpiece, in which the clamping jaws (7a, 7b) are moved away from each other relative to the clamping configuration; - at least one movement unit (8) associated with the base body (2) and suitable for moving the clamping device (7) between the clamping configuration and the release configuration, comprising: - at least one first slide (9a) which slides along at least one first working direction (D1) and is associated with said first jaw (7a); - at least one first clamping piston (11a) operatively associated with said first slide (9a) and movable due to the thrust of at least one pressurized fluid to allow said first slide (9a) and said first jaw (7a) to slide along at least one first clamping path (B1) and thus to move closer to said second jaw (7b); - at least one first release piston (12a) operatively associated with said first slide (9a) and movable due to said thrust of said pressurized fluid to allow said first slide (9a) and said first jaw (7a) to slide away from said second jaw (7b) along at least one first release path (R1) opposite to said first clamping path (B1); - at least one second slide (9b) which slides along at least one second working direction (D2) parallel to said first working direction (D1) and is associated with said second jaw (7b); at least one second clamping piston (11b) operatively associated with said second slide (9b) and movable due to said thrust of said pressurized fluid to allow said second slide (9b) and said second clamping jaw (7b) to slide along at least one second clamping path (B2) and thus move closer to said first clamping jaw (7a); and - at least one second release piston (12b) operatively associated with said second slide (9b) and movable due to said thrust of said pressurized fluid to allow said second slide (9b) and said second jaw (7b) to slide along at least one second release path (R2) opposite to said second clamping path (B2) and thus move away from said first jaw (7a); It is characterized in that the displacement unit (8) comprises at least one friction compensation assembly (30, 31) associated with the clamping piston (11a, 11b).

2. The device (1) according to claim 1, characterized in that The friction compensation assembly (30, 31) comprises a first loading device (30a) associated with the first clamping piston (11a) and a second loading device (30b) associated with the second clamping piston (11b), wherein the loading device (30) is suitable for applying at least one preloading force on the clamping piston (11a, 11b), the preloading force having a direction substantially parallel to the working direction (D1, D2) and a path consistent with the clamping path (B1, B2).

3. The device (1) according to claim 2, characterized in that: - The mobile unit (8) comprises: - at least one first inlet chamber (17a) for said pressurized fluid, delimited by said first clamping piston (11a) and by at least one first bottom wall (18a); and - at least one second inlet chamber (17b) for said pressurized fluid, delimited by said second clamping piston (11b) and by at least one second bottom wall (18b); - the first loading device (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 device (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).

4. The device (1) according to claim 3, characterized in that The friction compensation assembly (30, 31) comprises an adjustment device (31) for adjusting the preload force, which is associated with the bottom wall (18a, 18b) and / or the clamping piston (11a, 11b) and is suitable for adjusting the distance between the bottom wall (18a, 18b) and the associated clamping piston (11a, 11b) in the release configuration.

5. The device (1) according to claim 4, characterized in that The regulating device (31) comprises: at least one first adjustment pin (34a) arranged at least partially in said first inlet chamber (17a) and provided with at least one first abutment portion (35a) coinciding with said first bottom wall (18a); and - at least one second adjustment pin (34b) arranged at least partially in the second inlet chamber (17b) and provided with at least one second abutment portion (35b) coinciding with the second bottom wall (18b); The position of the adjusting pins (34a, 34b) can be adjusted along the working direction (D1, D2).

6. Device (1) according to one or more of the preceding claims, characterized in that The mobile unit (8) comprises: - at least one first introduction chamber (20a) of said pressurized fluid, delimited by said first release piston (12a) and by at least one first bottom surface (21a); - at least one second introduction chamber (20b) of the pressurized fluid, which is delimited by the second release piston (12b) and at least one second bottom surface (21b); - first return means (38a) associated with said first release piston (12a); and - second return means (38b) associated with said second release piston (12b); wherein the release piston (12a, 12b) is movable from a retracted position to an extended position as a result of filling the respective introduction chamber (20a, 20b) with the pressurized fluid, and wherein the return device (38a, 38b) is adapted to move the release piston (12a, 12b) from the extended position to the retracted position as a result of discharging the pressurized fluid from the respective introduction chamber (20a, 20b).

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

8. Device (1) according to one or more of the preceding claims, characterized in that It comprises a stop device (23, 24) associated with the base body (2) and comprising at least one stop piston (23) movable along at least one stop direction (A) substantially orthogonal to the working direction (D1, D2) and suitable for clamping the slide (9a, 9b) by friction in the clamping configuration.

9. The device (1) according to claim 8, characterized in that: - the first slide (9a) and the second slide (9b) respectively comprise at least one first recess (26a) and at least one second recess (26b), the recesses (26a, 26b) being juxtaposed to each other to define at least one internal space (S) between the slides (9a, 9b), and The stop piston (23) is provided with at least one enlarged portion (27) which can be inserted into the space (S) in order to clamp the slide (9a, 9b).

10. The device (1) according to claim 9, characterized in that The stop device (23, 24) comprises at least one elastically compressible thrust element (24), which is positioned between the stop piston (23) and the base body (2) and is suitable for exerting at least one direct thrust on the stop piston (23) along the stop direction (A).

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