Device for clamping workpieces on machine tools

Abstract

A device (1) for clamping a workpiece on a machine tool, comprising: a substrate (2), a clamping pin (3) movable along the working direction (L) between an extended position and a retracted position; - a blocking bushing (12) that fits around the clamping pin (3); at least one support assembly (15, 16) adapted to physically support the clamp pin (3) in the extended position, and the support assembly (15, 16) - a support element (15) defining a respective first rest surface (15a); - shifting means (16) adapted to move the support elements (15) along the working direction (L) and to place the support elements (15) in a support configuration in which the first rest surfaces (15a) are arranged in contact with the second rest surfaces (3a) of each of the clamping pins (3) when the clamping pins (3) are in the extended position; Equipped with.

Description

[Technical Field]

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

[0002] As is well known, the mass production of machined parts that require machining on machine tools has become increasingly dependent on the use of highly automated systems, for example, one or more machine tools electronically controlled by a processing control unit, one or more articulated robots that transport the workpieces to be machined to the machine tools, and specialized clamping devices, either hydraulically or pneumatically, that transport the workpieces and clamp them in place to allow them to be machined.

[0003] When machining is completed, the aforementioned clamping device releases the machined workpiece, which is again released by the robot.

[0004] One particular type of clamping device comprises a base that can be secured to a machine tool and pins that are at least partially housed within the base itself, the base being moved by a hydraulic drive between an extended position that allows the workpiece to be clamped onto the machine tool and a retracted position that allows the workpiece to be released from the machine tool.

[0005] More particularly, to ensure safe clamping of the workpiece when the pin is in the extended position, these devices are provided with a dedicated elastic bushing that fits the measurement on the pin and is adapted to prevent the bushing from returning to the retracted position.

[0006] Specifically, while the pin is moving from the retracted position to the extended position, the elastomeric bushing is pressurized by pumping pressurized oil through it and radially compresses against the pin, creating a restraining force against the pin that frictionally counteracts movement and clamps it in the extended position.

[0007] Once machining of the workpiece is complete, the resilient bushing can be decompressed, thereby removing the resulting binding force created by the pin, allowing the pin to return to its retracted position, thereby allowing release of the workpiece.

[0008] As can be appreciated, the design of the clamping device described thus far is expressly intended to ensure that movement of the pin is effected solely through the aforementioned modes, and in particular is not at all affected by forces exerted on the pin itself by the workpiece.

[0009] In other words, the subject device is specially designed so that stresses exerted by the workpiece on the pin do not cause even slight displacement of the pin from its extended position, resulting in a strong and stable fixation of the workpiece on the machine tool.

[0010] However, this requirement, which is clearly essential to ensure proper machining of the workpiece, is not met by known devices in some specific operating conditions, in particular when the force exerted on the pin by the workpiece exceeds a certain upper limit.

[0011] In this case, the peak load generated on the pin by the workpiece actually causes the elastic bushing to structurally deform, so that it is no longer able to hold the pin firmly in place by being compressed axially, with the inevitable result that the pin is induced to "elastically" sink slightly into the base body.

[0012] This fact, while undesirable in itself for any type of machining, proves to be highly unacceptable in industrial situations such as precision mechanics, where, as is well known, even the smallest of errors (e.g., a few hundredths of a millimeter) can result in the production of workpieces that are significantly outside the tolerance range and are therefore discarded.

[0013] Thus, if the realization of such stresses causes the serious consequences described above, a further increase in the force acting on the pin will not cause the pin to be slightly displaced from its extended position, but to sink completely into the substrate, thus completely losing the clamping function of the device.

[0014] In fact, it must be stated that the deformation undergone by the bushing in this situation is such that it loses its grip on the pin, causing the pin to return to its retracted position, thereby releasing its grip on the workpiece, with obvious and unacceptable consequences for the machining quality of the workpiece. Summary of the Invention

[0015] The main object of the present invention is to devise a device for clamping a workpiece onto a machine tool with an accurate and reliable operation that makes it possible to clamp the workpiece firmly onto the machine tool, regardless of the magnitude of the force applied.

[0016] One of the objects of the present invention is to devise a device for clamping a workpiece on a machine tool that, for equal size, has better performance than known devices and, in addition, can be made smaller than known devices for the same performance.

[0017] Another object of the present invention is to devise a device for clamping a workpiece onto a machine tool that will keep the machine tool firmly clamped on the workpiece even when predictable and unexpected pressure drops occur within the device itself.

[0018] Another object of the present invention is to devise a device for clamping a workpiece on a machine tool that is simple, rational, easy and effective to use, as well as being able to overcome the drawbacks of the prior art mentioned above within the scope of an inexpensive solution.

[0019] The aforementioned object is achieved by the device for clamping a workpiece on a machine tool having the features of claim 1.

[0020] Other features and advantages of the present invention will become more apparent from the description of preferred, but not exclusive, embodiments of devices for clamping workpieces, which are illustrated as suggestive, but non-limiting examples, in the accompanying drawings, in which: [Brief explanation of the drawings]

[0021] [Figure 1] 1 is an axonometric view of a device according to the invention; FIG. [Figure 2] 1 is an exploded view of a device according to the present invention. [Figure 3] 1 is a front view of a device according to the invention; FIG. [Figure 4] 4 is a cross-sectional view along the plane IV-IV of FIG. 3, of a device according to the invention in a first operating configuration; [Figure 5] 4 is a cross-sectional view along the VV plane of FIG. 3, of a device according to the invention in a first operating configuration; [Figure 6] 5 shows the same cross-sectional view as FIG. 4, but with the device according to the invention in a second operating configuration. [Figure 7] 6 shows the same cross-sectional view as FIG. 5, but with the device according to the invention in a second operating configuration. DETAILED DESCRIPTION OF THE INVENTION

[0022] With particular reference to these figures, the number 1 indicates generally a device for clamping a workpiece on a machine tool.

[0023] The device 1 for clamping a workpiece on a machine tool first comprises: at least one base body 2 that can be fastened to a machine tool; - at least one clamping pin 3 of at least one machined workpiece, conveniently associated with the base body 2 in a manner movable along the working direction L between an extended position allowing the workpiece to be clamped and a retracted position allowing the workpiece to be released; - moving means 4 adapted to move the clamping pin 3 along a working direction L, the moving means 4 comprising at least one moving piston 5 associated with the clamping pin 3 and movable along at least one first line V1 in the working direction L from a retracted position towards an extended position under the thrust of a pressurized fluid.

[0024] In this regard, it is important to note that in the context of the present disclosure, the phrase "pressurized fluid" refers to any fluid in a liquid state (and thus, ideally, incompressible) or in a gaseous state (and thus, compressible) that is used as a carrier medium for transporting energy in hydraulic or pneumatic circuits. Preferably, the pressurized fluid consists of conventional mineral oil, although alternative embodiments such as synthetic oils, vegetable oils, water, air, etc. cannot be excluded.

[0025] This means that preferably the moving piston 5 is hydraulic, however it cannot be excluded that the piston can be, for example, pneumatic (if the pressurized fluid is air) or hydraulic (if the pressurized fluid is water).

[0026] Furthermore, taking into account the presence of different parts of the device 1 in contact with the pressurized fluid, it is noted that dedicated gaskets are provided located at different points of the device 1, which for ease of illustration are commonly identified by the reference letter G.

[0027] As a further explanation, the possibility of manufacturing a device 1 without locomotion means 4 cannot be ruled out.

[0028] To clarify this, the displacement means 4 preferably comprise at least one respective first inlet chamber 6 for pressurized fluid, the inlet chamber 6 being bounded by a first bottom wall 7 of the base 2 and a displacement piston 5.

[0029] In this regard, the device 1 comprises at least one first circulation line C1 of pressurized fluid, the first circulation line C1 being connected to at least the first inlet chamber 6 and adapted to at least partially fill the first inlet chamber 6 with pressurized fluid.

[0030] Specifically, the first circulation line C1 is connected to an associated first supply inlet I1 (visible in FIG. 3) formed in the side of the base 2, which can be used to at least partially fill the first circulation line C1 with pressurized fluid.

[0031] In particular, the first supply inlet I1 can be connected to a dedicated pump system for pressurized fluid, which allows the first circulation line C1 to be gradually filled, and thus the first inlet chamber 6 to be filled with the pressurized fluid itself.

[0032] Said filling generates a thrust force on the moving piston 5, thereby displacing it along a first line V1 in its working direction L, thereby allowing the clamping pin 3 to slide from the retracted position to the extended position.

[0033] In order to enable the movement of the moving piston 5 and thus the movement of the clamping pin 3 in the opposite line, the moving means 4 advantageously comprises at least one elastic compression element 8 positioned between the moving piston 5 and the base body 2.

[0034] In this regard, the displacement means 4 comprises a housing chamber 9 adapted to accommodate the elastic compression element 8 and bounded by a second bottom wall 10 of the base body 2 and by the displacement piston 5 (Figures 4 and 6).

[0035] In the present case, the elastic compression element 8 is adapted to move the clamping pin 3 along a second line V2 in the working direction L opposite to the first line V1 upon release of the elastic compression force.

[0036] This means that the elastic compression element 8 is gradually compressed during the movement of the moving piston 5 along a first line V1 in the working direction L, and acquires an amount of elastic energy proportional to its own shortening rate.

[0037] The elastic energy thus stored can therefore be released to the moving piston 5 upon expulsion of the fluid contained in the first inlet chamber 6. The moving piston 5 is thus displaced along a second line V2 in the working direction L and the clamping pin 3 can return to its retracted position.

[0038] Indeed, from what has been described so far, it can be inferred that the moving piston 5 is preferably single-acting, i.e. its displacement along the working direction L is adjusted by pressurized fluid on only one of its lines (namely the first line V1).

[0039] However, an alternative embodiment of the displacement means 4 cannot be excluded in which there is no elastic compression element 8 and the displacement of the displacement piston 5 is adjusted by pressurized fluid in both lines V1, V2 of the working direction L.

[0040] In other words, it cannot be excluded that the housing chamber 9 can also be connected to a respective circulation line of the pressurized fluid, making it in fact a double-acting moving piston 5 .

[0041] Furthermore, the displacement means 4 comprises at least one spring element 11 positioned between the clamping pin 3 and the displacement piston 5 .

[0042] In particular, the spring element 11 is adapted to exert a resisting force on the moving piston 5 directed along a second line V2 of the working direction L as a result of the extended position being reached by the clamping pin 3.

[0043] In fact, the spring element 11 counteracts any further displacement of the moving piston 5 along the first line V1 in the working direction L and makes it possible to stop the stroke of the moving piston 5 when a state of equilibrium is achieved between the elastic force generated thereby and the thrust exerted on the clamping pin 3 by the pressurized fluid.

[0044] As will be explained later in this disclosure, reaching this equilibrium plays an important role in coordinating the operation of some of the major components of device 1, and thus in controlling the overall operation of the device itself.

[0045] The device 1 then comprises at least one blocking bushing 12 which fits at least partially around the clamp pin 3 and is deformable under the thrust of a pressurized fluid between a clamping configuration of the clamp pin 3 and a release configuration of the clamp pin 3.

[0046] In this regard, as can be seen in FIGS. 4 and 6, the device 1 comprises a second inlet chamber 13 for pressurized fluid bounded by the peripheral wall 14 of the base 2 and the blocking bushing 12 .

[0047] Specifically, the second inlet chamber 13 is connected to the first circulation line C1 and is thus filled with pressurized fluid substantially simultaneously with the first inlet chamber 6.

[0048] This allows the blocking bushing 12 to be deformed into the clamping configuration and to exert a frictional force on the clamping pin 3 to counteract its movement along the second line V2 of the working direction L when the clamping pin 3 moves into the extended position.

[0049] Also, due to this fact, as a result of the evacuation of the first inlet chamber 6 and the second inlet chamber 13, the blocking bushing 12 is deformed in a released configuration, thus releasing the aforementioned frictional force on the clamping pin 3 and allowing the clamping pin 3 to return to its retracted position.

[0050] According to the invention, the device 1 comprises at least one support assembly 15, 16 adapted to physically support the clamp pin 3 in the extended position, and the support assembly 15, 16 comprises: at least one support element 15 defining a respective first rest surface 15a; - shifting means 16 on which the support elements 15 are arranged in a supported state, which means are associated with the base body 2 and are adapted to move the support elements 15 along the working direction L and to arrange the support elements 15 in a supporting configuration in which the first rest surfaces 15a are arranged in contact with the second rest surfaces 3a of each of the clamping pins 3 when the clamping pins 3 are in the extended position (Figure 6).

[0051] Indeed, when the clamp pin 3 is in the extended position, the shifting means 16 contacts the clamp pin 3 and positions the support element 15, so that in the support configuration the support element 15 is physically positioned between the shifting means 16 and the clamp pin 3, thereby preventing any displacement of the clamp pin 3 from the extended position.

[0052] It is important to explain from the outset how crucial this measure is in improving the shortcomings of the prior art previously pointed out.

[0053] In this regard, the support provided to the clamping pin 3 by the support assemblies 15, 16 enables the clamping pin 3 to hold itself firmly in the extended position regardless of the strength of the force exerted by the workpiece, which provides advantages to the quality of machining achievable on the workpiece clamped thereby.

[0054] In other words, the presence of the support assemblies 15, 16 makes it possible to counteract any stresses exerted by the workpiece on the clamp pin 3 and thus on the blocking bushing 12, thus preventing these loads from causing even the slightest movement of the clamp pin 3 from its extended position.

[0055] Not only this, but by this means the device 1 can operate at a lower operating pressure than known devices of equal size and is therefore more efficient in its use than known devices.

[0056] Likewise, this fact also makes it possible to reduce the size of device 1 while at the same time maintaining the same performance offered by known devices. It is easy to see that the reduction in size of device 1 not only reduces the cost of producing the device itself, but also makes it slightly easier to manage and use.

[0057] Finally, the presence of the support assemblies 15, 16 makes it possible to obtain a device 1 that is distinguished by its timely operation, its great versatility of use, and its great convenience and reliability of use.

[0058] With regard to the support element 15, the latter comprises at least one base 17 provided with a first resting surface 15a and arranged in contact with the shifting means 16 (FIGS. 4 and 6).

[0059] Furthermore, the support element 15 preferably comprises at least one central portion 18 associated with the base portion 17 and at least partially inserted into the clamping pin 3 .

[0060] The central portion 18 conforms to an elongated shape along the working direction L.

[0061] More precisely, the center portion 18 has a substantially cylindrical structure.

[0062] In the present case, the longitudinal axes of the central portion 18 and the clamping pin 3 overlap each other and coincide with the working direction L.

[0063] By virtue of its partial insertion into the clamping pin 3, the presence of the centre portion 18 makes the operation of the support assemblies 15, 16 particularly accurate and reproducible, in particular enabling the shifting means 16 to position the support element 15 accurately and effectively in the support arrangement whenever the clamping pin 3 is moved into the extended position.

[0064] However, it cannot be excluded that the support element 15 may be constructed without the central portion 18 and only provided with the base portion 17 .

[0065] With regard to the details of the shifting means 16, the shifting means 16 comprises at least one wedge-shaped body movable along a sliding direction S between an operating position (FIG. 6) in which the support element 15 is placed in the support arrangement and a home position (FIG. 4) in which the support element 15 is moved away from the support arrangement.

[0066] Specifically, the wedge-shaped body 16 moves along the sliding direction S, and the support element 15 moves along the working direction L.

[0067] In this regard, the sliding direction S is transverse to the working direction L.

[0068] More specifically, the sliding direction S is substantially perpendicular to the working direction L.

[0069] Furthermore, the wedge bodies 16 are provided with respective first inclined surfaces 16a arranged in contact with respective second inclined surfaces 15b of the support elements 15 (FIGS. 4 and 6).

[0070] Specifically, the second inclined surface 15 b is configured on the base 17 of the support element 15 .

[0071] Specifically, the second inclined surface 15b and the first placing surface 15a are located at opposite positions of the base 17.

[0072] With respect to the inclined surfaces 15b and 16a, the inclined surfaces 15b and 16a are inclined with respect to the sliding direction S by a characteristic angle α that is less than 20°.

[0073] It should be noted that this characteristic angle α makes it possible to realize the device 1 in a so-called "irreversible" operation, i.e., to keep the clamping pin 3 in the extended position even in the event of a sudden pressure drop inside the device itself, for example due to a failure of the external pump system.

[0074] This means in practice that, due to this angle, the force exerted by the workpiece on the clamping pin 3 will not, under any circumstances, displace the wedge body 16 along the sliding direction S. This therefore ensures that the support element 15 is held firmly in the support arrangement and thus firmly clamps the workpiece on the machine tool.

[0075] In this regard, it is specified that the characteristic angle α is preferably 5° to 20°, and more preferably 10° to 20°.

[0076] In this way, it is possible not only to realize the advantages outlined so far for irreversibility, but also to realize a wedge-shaped body 16 which limits its overall dimensions along the sliding direction S and therefore has very compact dimensions.

[0077] More preferably, the characteristic angle α is substantially equal to 15°.

[0078] In fact, such values ​​prove to be quite adequate to minimize the overall dimensions of the wedge 16 along the sliding direction S, and at the same time to realize the device 1 with a completely irreversible operation.

[0079] However, having said the above, it cannot be excluded to provide a characteristic angle α of a different value than that shown, for example an angle greater than 20°.

[0080] To explain the wedge-shaped body 16 in more detail, as can be seen in FIG. 2, the wedge-shaped body 16 has at least one slot 19 formed through at least a portion of the first inclined surface 16a, and the moving piston 5 is inserted into the slot 19.

[0081] Specifically, the slot 19 is formed entirely along the first inclined surface 16a.

[0082] The presence of the slot 19 therefore allows the moving piston 5 to pass through the wedge body 16 and thus connect to the clamping pin 3. Along the working direction L, movement of the clamping pin 3 is possible.

[0083] Conveniently, the device 1 comprises sliding means 20 associated with the wedge-shaped body 16, the sliding means 20 further comprising at least one sliding piston 21 movable along a sliding direction S under the thrust of a pressurized fluid and adapted to enable sliding of the wedge-shaped body 16 along at least one first direction W1 of the sliding direction S.

[0084] In this regard, the sliding means 20 comprise at least one sliding bushing 22 into which a sliding piston 21 is inserted along a sliding direction S to slide.

[0085] Furthermore, the sliding means 20 is a respective third inlet chamber 23 for pressurized fluid bounded by the outer wall 22a of the sliding bushing 22 and by the sliding piston 21; a respective fourth inlet chamber 24 for pressurized fluid bounded by a closed bottom 25 and a sliding piston 21 attached to the base 2; It comprises at least one of the following:

[0086] Preferably, the sliding means 20 comprises both a third inlet chamber 23 and a fourth inlet chamber 24 .

[0087] In this sense, the movement of the sliding piston 21 along the sliding direction S is entirely controlled by the pressurized fluid, and for this reason it can therefore be stated that the sliding piston 21 is of the double-acting type.

[0088] To be precise, sending pressurized fluid into the third inlet chamber 23 makes it possible to slide the sliding piston 21 along a first direction W1 of the sliding direction S, while sending pressurized fluid into the fourth inlet chamber 24 makes it possible to slide the sliding piston 21 along a second direction W2 opposite to the first direction W1 of the sliding direction S.

[0089] However, it cannot be excluded that the sliding piston 21 may be single-acting.

[0090] In this case, the movement of the sliding piston 21 along a first direction W1 of the sliding direction S is determined by the pressurized fluid, while the movement of the sliding piston 21 along a second direction W2 can be adjusted, for example, by one or more elastic members adapted to allow reversal of the movement.

[0091] Turning to the preferred embodiment in which the sliding piston 21 is double-acting, it is conveniently noted that the third inlet chamber 23 is connected to a first circulation line C1, while the fourth inlet chamber 24 is connected to a second circulation line C2 of pressurized fluid different from the one mentioned above.

[0092] In this regard, the second circulation line C2 is further connected to an associated second supply inlet I2 (FIG. 3) formed in the side of the base 2, and the second circulation line C2 can be used to at least partially fill the first circulation line C1 with pressurized fluid.

[0093] As mentioned for the first supply inlet I1, the second supply inlet I2 can also be connected to a pressurized fluid pump system so that the second circulation line C2, and thus the fourth inlet chamber 24, can be gradually filled with pressurized fluid.

[0094] It can be inferred that the connections described so far make it possible to supply the first inlet chamber 6, the second inlet chamber 13 and the third inlet chamber 23 by sending pressurized fluid along the first circulation line C1, while it makes it possible to supply the fourth inlet chamber 24 by sending pressurized fluid along the second circulation line C2.

[0095] In this sense, as will soon become apparent, it is expected that the displacement of the clamping pin 3 to the extended position is associated with a movement of the sliding piston 21 along a first direction W1 of the sliding direction S, and that the return of the clamping pin 3 to the retracted position is associated with a movement of the sliding piston 21 along a second direction W2 of the sliding direction S.

[0096] To ensure proper movement of the shifting means 16, the sliding means 20 comprises at least one deformable body 26 adapted to move the wedge-shaped body 16 along a second direction W2 of the sliding direction S upon release of the elastic compressive force.

[0097] With particular reference to Figures 2, 4 and 6, the deformation body 26 essentially consists of one or more springs, preferably of the helical type.

[0098] Conveniently, the wedge-shaped bodies 16 are provided with respective storage cavities 27 within which the deformable bodies 26 are at least partially inserted.

[0099] Specifically, one end of the deformable body 26 is arranged in contact with the bottom wall of the storage cavity 27 , while the other end of the deformable body 26 is arranged in contact with a closure plate 28 attached to the base body 2 .

[0100] This means that one end of the deformable body 26, which is placed in contact with the bottom wall of the storage cavity 27, is movable along the sliding direction S, while the other end, which is placed in contact with the closure plate 28, is fixed relative to the base body 2.

[0101] However, it is possible that the wedge body 16 does not have a storage cavity 27 and thus it cannot be excluded that the deformation body 26 is arranged between the wedge body itself and the closure plate 28 .

[0102] In all cases, displacement of the sliding piston 21, and thus the wedge-shaped body 16, along a first direction W1 of the sliding direction S gradually compresses the deformable body 26, thereby releasing the elastic force accumulated in the wedge-shaped body 16 and thereby enabling displacement of the wedge-shaped body 16 along a second direction W2 of the sliding direction S.

[0103] This means that along the second direction W2 of the sliding direction S, the sliding piston 21 and the wedge-shaped body 16 move simultaneously, one subjected to the thrust exerted by the pressurized fluid in the third inlet chamber 23 and the other subjected to the release of the elastic force accumulated by the deformable body 26.

[0104] Conveniently, it should be noted that the inclined surfaces 15b, 16a extend along a second direction W2 of the sliding direction S, close to the sliding piston 21 (FIGS. 4 and 6).

[0105] In other words, the tangents of the inclined surfaces 15b, 16a may have a negative inclination extending along the second angle W2 of the sliding direction S, which inclination corresponds to the characteristic angle α.

[0106] Conveniently, the device 1 comprises at least one shut-off valve 29 (visible in Figures 2, 5 and 7), which is fluid-operated and associated with the sliding means 20 and adapted to maintain the wedge-shaped body 16 in a fixed position.

[0107] Specifically, the shutoff valve 29 is at least one plunger 29a movable along one direction of the block B; - at least one blocking body 29b operably associated with the plunger 29a, the blocking body 29b being compressible along the blocking direction B between a compressed position (Figure 7) through which the blocking body 29b can be passed by pressurized fluid in both angles of the blocking direction B, and an extended position (Figure 5) through which the blocking body 29b can be passed by pressurized fluid in only one angle of the blocking direction B.

[0108] In this regard, it is important to add that the substrate 2 is at least one first introduction chamber 30 for pressurized fluid connected to a first circulation line C1 and bounded by a first bottom surface 31 and a plunger 29a; at least one second introduction chamber 32 (FIGS. 5 and 7) for pressurized fluid, connected to a second circulation line C2 and bounded by a plunger 29a and a second bottom surface 33; Equipped with.

[0109] Furthermore, the base body 2 comprises at least one containment chamber 34 of the barrier body 29 b which communicates with the fourth inlet chamber 24 .

[0110] As expected, when the shut-off body 29b is in the compressed position, pressurized fluid can flow in either direction in the shut-off direction B between the second admission chamber 32 and the storage chamber 34.

[0111] In other words, when the isolator 29b is in the compressed position, the second introduction chamber 32, the storage chamber 34, and the fourth inlet chamber 24 are in fluid operative communication with one another.

[0112] Conversely, when the shutoff body 29b is in the extended position, pressurized fluid can flow from the second introduction chamber 32 to the storage chamber 34 in exactly one direction only, along the shutoff direction B.

[0113] In other words, the shutoff body 29b prevents pressurized fluid from flowing from the storage chamber 34 to the second introduction chamber 32 when in the extended position.

[0114] By means of the possibility of fluidically isolating these chambers, the shut-off valve 29 ensures that in the event of an unexpected drop in pressure, the chambers remain pressurized, so that such an anomaly does not result in a potential displacement of the wedge-shaped body 16 from its home position.

[0115] In this sense, it is easy to see that the shut-off valve 29 works in conjunction with the technical measures outlined so far in making the device 1 particularly reliable in its operation.

[0116] Optionally, the device 1 comprises at least one sequence valve 35 connected to the shut-off valve 29 and adapted to selectively allow and block access of pressurized fluid to the shut-off valve 29 (Figures 2, 5, and 7).

[0117] Specifically, the sequence valve 35 is connected to the first circulation line C1, and thus by sending pressurized fluid into the first inlet chamber 6, into the second inlet chamber 13, and into the third inlet chamber 23, the pressurized fluid is simultaneously conveyed towards the sequence valve itself.

[0118] Furthermore, the sequence valve 35 is arranged upstream of the first introduction chamber 30 with respect to the flow direction of the pressurized fluid along the first circulation line C1.

[0119] In this manner, the sequence valve 35 allows for selective regulation of access of pressurized fluid to the first introduction chamber 30 .

[0120] In this regard, the sequence valve 35 includes a spool 35a that is movable between an open position that allows the flow of pressurized fluid toward the shut-off valve 29 and a closed position that obstructs the flow of pressurized fluid toward the shut-off valve 29.

[0121] Furthermore, the sequence valve 35 comprises at least one elastic compressible preload element 35b, which is associated with the spool 35a and adapted to apply a reaction force to the spool 35a when moving from a closed position to an open position.

[0122] Therefore, in order to bring the spool 35a to the open position, the fluid must have sufficient pressure to overcome not only the resistance offered by the spool itself, but also the aforementioned reaction force exerted by the preload element 35b.

[0123] Preferably, the preload element 35b is of the type of a single spring or set of springs.

[0124] More preferably, the preload element 35b is of the type of a single disc spring or set of disc springs.

[0125] Conveniently, the sequence valve 35 comprises at least one adjustment member 35c operatively associated with the preload element 35b and adapted to allow adjustment of the reaction force exerted by the preload element 35b on the spool 35a.

[0126] Specifically, adjustment of adjustment member 35c varies the compression of preload element 35b, and thus varies the reaction force exerted thereby.

[0127] In particular, the adjustment member 35 c is at least partially threaded onto the base body 2 .

[0128] In this sense, the adjustment member 35c can be screwed in to increase the compression of the preload element 35b and thus increase the reaction force on the spool 35a, and can be unscrewed to decrease the compression of the preload element 35b and thus decrease the reaction force on the spool 35a.

[0129] The provision of sequence valve 35 allows for fine tuning of the operation of device 1, in particular the pressure required for pressurized fluid to access first introduction chamber 30 and operate plunger 29a, thereby considerably increasing the versatility of use of device 1.

[0130] The operation of the present invention is as follows.

[0131] First, the supply inlets I1, I2 of the device 1 are connected to a pump system, which allows (for example, by means of a dedicated withdrawal valve or by a similar vendor) to send pressurized fluid to either the first circulation line C1 or the second circulation line C2, and also allows simultaneous discharge of the pressurized fluid contained in either the first circulation line C1 or the second circulation line C2, or the other.

[0132] Specifically, to clamp a workpiece on a machine tool, pressurized fluid is sent along a first circulation line C1 while being exhausted to a second circulation line C2.

[0133] In doing so, the first inlet chamber 6 gradually fills, thus generating a thrust force on the moving piston 5, thereby displacing the moving piston 5 along a first line V1 in the working direction L.

[0134] Thus, the clamp pin 3 gradually moves from the retracted position to the extended position and thus contacts the workpiece.

[0135] On the other hand, the introduction of pressurized fluid into the second inlet chamber 13 causes a pressurization of the blocking bushing 12, which in turn causes a deformation of the clamping arrangement, which in turn exerts a friction force on the clamping pin 3 towards the first line V1 of the working direction L, thus counteracting its displacement from the extended position.

[0136] At the same time, pressurized fluid is conveyed towards the third inlet chamber 23, gradually filling it and also feeding the sequence valve 35. At this stage, however, the pressurized fluid still has insufficient pressure to force the spool 35a in the open position, thus blocking access towards the first inlet chamber 30.

[0137] When the workpiece comes into contact, the resulting increase in pressure causes the spring element 11 to begin to compress while the displacement of the moving piston 5 continues along the first line V1 in the working direction L, thus increasing the elastic energy stored thereby.

[0138] Thus, when the elastic force and the pressure exerted by the pressurized fluid in the first inlet chamber 6 reach a state of equilibrium, the spring element 11 stops the stroke of the moving piston 5 .

[0139] On the other hand, the increase in pressure experienced by the fluid may be sufficient to place the spool 35 a in the open position, thus allowing the fluid to flow itself into the first inlet chamber 30 .

[0140] Thus, the pressurized fluid exerts a thrust on the plunger 29a, displacing the plunger 29a along the blocking direction B, resulting in compression of the blocking body 29b in the compressed position.

[0141] In this way, the fluid contained in the fourth inlet chamber 24, the storage chamber 34 and the second introduction chamber 32 flows towards the second communication line C2 and is therefore discharged.

[0142] By doing so, the pressurized fluid conveyed into the third inlet chamber 23 can push the sliding piston 21 in the second direction W2 of the sliding direction S, and the deformable body 26 can release its elastic energy by moving the wedge-shaped body 16 along the second direction W2 of the sliding direction S and by placing the support element 15 in a supporting configuration.

[0143] As a result of this, the clamp pin 3 is supported by the support assemblies 15, 16 whilst in the extended position, thus enabling the advantages of stability, precision and efficient operation outlined above to be realised.

[0144] After machining of the workpiece is complete, the workpiece can be released from the device 1 by returning the clamping pins 3 to their retracted position.

[0145] To do this, the flow direction of the pressurized fluid is reversed from that in the previous case, i.e. the pressurized fluid is sent along the second circulation line C2, and the first circulation line C1 is connected to discharge.

[0146] Thus, pressurized fluid enters the second inlet chamber 32 and displaces the plunger 29a in the opposite direction to the blocking direction B (ie, away from the blocking body 29b), causing the blocking body 29b to move to the extended position.

[0147] The pressurized fluid introduced into the second inlet chamber 32 can still flow through the blocking body 29b and into the fourth inlet chamber 24 until it is completely filled.

[0148] Due to the fact that the isolating body 29b is in the extended position, the fourth inlet chamber 24 is now fluidically isolated from the second introduction chamber 32. As will be explained, this achieves the aforementioned advantages regarding the safety of operation ensured by the device 1 in the event of a failure or breakdown of the pump system.

[0149] At the same time, the discharge of the first circulation line C1 leads to a deformation of the blocking bushing 12 in the release configuration, thus allowing the frictional forces generated by the clamping pin 3 to be counteracted.

[0150] Moreover, this fact also causes the gradual emptying of the first inlet chamber 6 and the release of the elastic energy stored by the elastic compression element 8 of the moving piston 5 .

[0151] The moving piston 5 therefore moves along a second line V2 in the working direction L, returning the clamping pin 3 to the retracted configuration.

[0152] Furthermore, the discharge of the first circulation line C1 gradually empties the third inlet chamber 23, which results in the sliding piston 21 being displaced along the first direction W1 of the sliding direction S by the fluid in the fourth inlet chamber 24 exerting a thrust thereon.

[0153] This action moves the wedge 16 from the operating position into the working position, and at the same time the support element 15 moves along a second line V2 in the working direction L.

[0154] The clamping pin 3 is therefore displaced together with the support element 15 along the second line V2 in the working direction L and returns to the retracted position, which consequently completes the release of the workpiece from the machine tool.

[0155] In fact, it has been found that the invention as described accomplishes its intended objectives.

[0156] Specifically, it is emphasized that the special means providing the support assembly allows the pin to be physically supported in an extended position, reacting to any displacement of the pin from that position, and thus enabling the clamping of the workpiece by machining the workpiece quite effectively and smoothly.

[0157] Furthermore, this same measure makes it possible to reduce the size of the device compared to known devices while keeping its performance comparable, thus reducing the associated costs and making it less difficult to handle.

[0158] Likewise, the presence of the support assembly makes it possible to achieve a device that stands out by its superior performance to known devices, even when of equal size, and which is therefore more versatile in use than known devices.

[0159] Finally, it should be noted that the particular characteristic angle of the wedge makes it possible to realize an irreversible clamping device, and thus to keep the workpiece firmly clamped on the machine tool, even in the event of some unexpected pressure drop within the device itself.

Claims

1. A device (1) for clamping a workpiece on a machine tool, comprising: at least one base body (2) that can be fixed to a machine tool; an extended position that allows the workpiece to be clamped; at least one clamping pin (3) of at least one workpiece associated with the base (2) in a manner movable along the working direction (L) between a retracted position allowing the workpiece to be released; at least one blocking bushing (12) that fits at least partially around said clamping pin (3) and is deformable under the thrust of a pressurized fluid between a clamping configuration of said clamping pin (3) and a release configuration of said clamping pin (3); The device (1) comprises at least one support assembly (15, 16) adapted to physically support the clamp pin (3) in the extended position; and at least one support element (15) defining a respective first rest surface (15a); - shifting means (16) on which said support elements (15) are arranged, The device (1) is characterized by the fact that the shifting means (16) are associated with the base (2) and are adapted to move the support elements (15) along the working direction (L) and to arrange the support elements (15) in a supporting configuration in which the first rest surfaces (15a) are arranged in contact with the second rest surfaces (3a) of each of the clamping pins (3) when the clamping pins (3) are in the extended position.

2. 2. The device (1) according to claim 1, characterized by the fact that it comprises moving means (4) adapted to move the clamping pin (3) along the working direction (L), said moving means (4) comprising at least one moving piston (5) associated with the clamping pin (3) and movable along at least one first line (V1) in the working direction (L) from the retracted position towards the extended position under the thrust of a pressurized fluid.

3. 3. The device (1) according to claim 2, characterized by the fact that the moving means (4) comprise at least one elastic compression element (8) positioned between the moving piston (5) and the base body (2) and adapted to move the clamping pin (3) along a second line (V2) in one of the working directions (L) opposite to the first line (V1) upon release of an elastic compression force.

4. 4. The device (1) according to claim 1, wherein the shifting means (16) comprises at least one wedge-shaped body (16) provided with a respective first inclined surface (15b) and arranged in contact with a respective second inclined surface (16a) of the support elements (15), and which is movable along a sliding direction (S) transverse to the working direction (L) between an operating position in which the support elements (15) are arranged on the support arrangement and a home position in which the support elements (15) are moved away from the support arrangement, wherein a movement of the wedge-shaped body (16) along the sliding direction (S) causes a movement of the support elements (15) along the working direction (L).

5. 5. The device (1) according to claim 4, characterized by the fact that said device (1) comprises sliding means (20) associated with said wedge-shaped body (16), said sliding means (20) further comprising at least one sliding piston (21), said sliding piston (21) being movable along said sliding direction (S) under the thrust of a pressurized fluid and adapted to enable sliding of said wedge-shaped body (16) along at least one first direction (W1) of said sliding direction (S).

6. 6. The device (1) according to claim 5, characterized by the fact that the sliding means (20) comprises at least one deformation body (26) adapted to move the wedge-shaped body (16) along a second direction (W2) of the sliding direction (S) opposite to the first direction (W1) upon release of an elastic compression force.

7. The device (1) according to one or more of claims 1 to 6, characterized by the fact that the inclined surfaces (15b, 16a) extend near the sliding piston (21) along the second direction (W2) of the sliding direction (S).

8. 8. The device (1) according to claim 7, characterized by the fact that the inclined surfaces (15b, 16a) are inclined by a characteristic angle (α) of less than 20° relative to the sliding direction (S).

9. The device (1) according to one or more of claims 1 to 8, characterized by the fact that said device (1) comprises at least one shut-off valve (29), said shut-off valve (29) being fluid-operated and associated with said sliding means (20) and adapted to maintain said wedge-shaped body (16) in said fixed position.

10. The device (1) according to one or more of claims 1 to 9, characterized by the fact that the device (1) comprises at least one sequence valve (35), which is connected to the shut-off valve (29) and adapted to selectively allow and block access of the pressurized fluid to the shut-off valve (29).

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