Holding device for mechanical parts

Description

TECHNICAL FIELD

[0001] The present invention relates to a device for holding mechanical parts according to the preamble of claim 1. Such a device is shown in US 3,422,709 A, and is notably used in the field of precision mechanics. It relates in particular to a device capable of holding parts having a particular shape or configuration, for the purpose of machining or other treatment. It also relates to a device for holding bars used, in particular, for the manufacture of precision mechanical parts by turning.In more detail, it relates to a mechanical part retaining device, comprising a slide holder formed of a body and a head having a central bore in which is placed a part of the part to be retained, this part to be retained protruding from said head, the head comprising a conical area, the retaining device further comprising at least two slides and an actuation element for said slides. PREVIOUS TECHNIQUE

[0002] Devices for holding mechanical parts are well-known and widely used, particularly for bar turning, turning, milling, or more generally, machining these parts. One commonly used type of device is a flexible clamping collet, also known as a slotted collet. This type of collet has a rigid body and a head with slots and a central bore. A clamping ring is placed around the head. The workpiece is positioned in the central bore so that the work area extends beyond the head. Once the workpiece is in place, the clamping ring is positioned around the head and actuated, usually by rotation, to tighten the slots in the head. The material of the head then clamps and holds the workpiece. These collets utilize the elastic properties of the material forming the collet head.A clamp similar to conventional split clamps is described in particular in utility model DE 88 07 447.1. The clamp described in this document has a rubber element in the slots made between the jaws.

[0003] Conventional split collets, as well as the collet described in this document, have several limitations. By design, the elastic displacement of the jaw elements is small. The range of workpiece diameters that such a collet can accommodate is therefore very limited. Furthermore, if the workpiece diameter is slightly larger or smaller than the nominal diameter of the split collet, the workpiece will be clamped only at the rear or only at the front, and not along a significant length of the collet. This results in less than optimal clamping and potential marking of the workpieces. Improper clamping leads to machining defects, particularly concentricity issues.

[0004] Another problem arises from the raw material from which the parts are machined. In practice, for example, when parts are machined by turning, they are often made from cylindrical bars obtained by rolling. When these bars come out of the rolling mill, they have dimensional defects, meaning their diameter is not constant along their entire length. Typically, a bar can have diameter fluctuations of several tenths of a millimeter, as well as morphological defects. Such fluctuations mean that the bars cannot be used as is in a slotted collet. Indeed, the range of diameters that a given slotted collet can accommodate is often smaller than the diameter fluctuations of the bars. In practice, the bars are first ground to bring their diameter within an acceptable tolerance range before they can be machined.This grinding operation generates significant costs, both in terms of handling and the grinding itself.

[0005] Other types of clamping elements are described in publications such as US 4 775 160, FR 2 511 289, and DE 20 2009 007227. These documents all concern chucks designed to hold objects such as drill bits. Such chucks can hold objects of a wide range of diameters. However, due to their design, they cannot provide sufficiently concentric clamping to allow machining that meets the common requirements of precision mechanics. This lack of precision stems primarily from the fact that the jaws move freely within a groove without being fitted into it and are controlled by a threaded jaw track. The grooves serve only to guide the jaws during their longitudinal movement but cannot ensure precise positioning.Furthermore, in order for the system to operate without jamming, the jaws and thread must have a certain amount of play which is incompatible with the precision required for machining.

[0006] In a common use of collets, the bar on which the workpieces are machined passes through the collet along a longitudinal axis. The design of the chucks mentioned above prevents the passage of a bar. Therefore, these chucks cannot be used in the field in which the present invention finds significant application.

[0007] Document GB 735 703 describes a clamping device consisting of a cylindrical cage with longitudinal slots. These slots accommodate clamping elements. The clamping elements have a conical area that bears against a chuck body. The surface of the chuck body opposite the conical area has a thread that meshes with a thread on a cap. Rotation of the cap causes the chuck body to move, which in turn causes the clamping elements to move.

[0008] As with chucks, the clamping elements are free-floating in the slots. Furthermore, the ring, during its rotation to position the clamping elements, applies a tangential stress and consequently causes deformation. These characteristics result in a lack of precision in the workpiece holding and therefore in their machining. It should also be noted that the device described in this document does not allow the passage of a bar of material.

[0009] US patent 2,430,761 describes a clamping device with a body containing four slots in which transversely movable jaws are positioned. The jaws have inserts designed to adapt to the shape of the workpiece. The jaws have an inclined surface that cooperates with an inclined surface of a ring. Longitudinal movement of the ring results in transverse movement of the jaws.

[0010] This collet has several drawbacks. Its design is relatively complex, making it impossible to produce a small collet. Therefore, it is only suitable for workpieces with a diameter of several millimeters. The collet itself is mounted on a chuck. Since chucks generally do not have precise positioning, the collet cannot be positioned accurately. The collet has a clamping cap that surrounds the collet body. This cap is centered relative to the body. If the body is misaligned, the cap will not be properly positioned, and the workpiece will have defects. The cap is relatively thick. As a result, the distance between the front end of the jaws and the area where the workpiece is machined is significant. This creates an overhang that introduces inaccuracies into the finished part.The center of the clamp is not empty, but contains elements that allow the clamp to be operated. Therefore, it is not possible to pass a bar through it.

[0011] Patent CH 535 624 relates to a clamping device comprising a body with recesses. Jaws are inserted into the recesses. The body has a front conical zone and a rear conical zone. When the clamp is used on a machine, a nut presses against the conical zones and moves the jaws to clamp the workpiece.

[0012] From a design standpoint, the collet according to this invention has a major drawback. Indeed, creating the recesses in a rigid body, for example, made of steel, necessarily implies that this body will open, or in other words, that the recesses will spread apart. This opening cannot be controlled, and the precision of the collet cannot be guaranteed. Furthermore, the jaws are very long relative to the collet body. Consequently, the jaws are not optimally guided within the body, and the accuracy of the positioning, and therefore the machining, suffers. It is thus impossible to guarantee precise machining with such a collet.

[0013] Another type of holding device is known as a guide bushing. Such a bushing is usually screwed onto the frame or shaft of a machine. It holds the bar being worked in such a way that it can rotate inside the bushing while the bushing itself can either remain stationary or rotate, depending on the application.

[0014] Modern guide bushings require the use of bars with minimal concentricity. In practice, as-rolled bars must be ground before they can be machined when guided in a guide bushing. Indeed, concentricity defects or diameter fluctuations cause significant friction, which can damage the workpiece and / or the guide bushing and prevent precise machining.

[0015] Existing collets and collets are functional when the part of the workpiece held in the collet is a cylinder of constant diameter. For workpieces with unusual shapes, this type of collet may not be suitable. For example, if the workpiece has a large diameter section followed by a small diameter section, and finally the workpiece itself, passing the large diameter section through the collet's bore can be problematic. This is because the collet head needs to have high elasticity to allow the large diameter section to pass through while still clamping the small diameter section. The elasticity of the collet head is due to the deformation of the material from which it is made. Clearly, this elasticity is limited, which poses problems when the workpiece has areas with significant diameter variations.

[0016] For workpieces that cannot be held by this type of clamp, other holding devices exist. A well-known example is a chuck with jaws incorporating a rack and pinion mechanism. This chuck has a thread that acts on the rack of the jaws, moving them simultaneously and ensuring the centering of the workpiece.

[0017] These chucks, which allow for this type of clamping, are relatively difficult to machine and therefore expensive. Furthermore, positioning and clamping the workpiece is relatively time-consuming and difficult to automate. Such a chuck is therefore not ideal and is reserved for situations where elastic clamping collets cannot be used.

[0018] Furthermore, the design of these chucks prevents achieving the required precision, particularly because the rack and the thread must have some play.

[0019] A number of prior art clamps or clamping tools have jaws designed to hold the workpiece, these jaws being held against the workpiece by means of a threaded ring. Rotation of the ring causes it to move, which in turn acts on the jaws. One problem with these systems is that the ring applies a tangential force to the jaws. This tangential force causes deformation of the jaws, resulting in a misalignment of the workpiece. Machining accuracy is thus affected.

[0020] A number of anterior art support devices have their central area used for actuating jaws or clamping elements. These devices therefore do not allow the passage of a bar and are thus unsuitable for machining. BRIEF SUMMARY OF THE INVENTION

[0021] The present invention aims to overcome the drawbacks of prior art devices by providing a workpiece holding device with a wide range of possible uses. This holding device is, however, simpler to manufacture than a chuck with jaws and is more flexible to use.

[0022] This goal is achieved by a mechanical part retention device as defined in claim 1.

[0023] In the device of the invention, the workpiece is not held by the elasticity of the material forming the clamping tool, but by means of sliding blocks. This allows the clamping elements to have very large strokes without risking deformation of the device. As a result, it is possible to hold workpieces that have, for example, areas of significantly different diameters.

[0024] Using the principle of the invention, it is also possible to hold unconventionally shaped parts very effectively. For example, it is possible to hold parts with one or more flats, parts with square, hexagonal or other cross-sections, threaded areas, conical parts, etc.

[0025] The design of the holding device of the invention, and in particular of the slides, allows optimal positioning of the part, even if it has concentricity defects and areas in which the diameter has significant fluctuations.

[0026] The device can be used both as a clamp to firmly hold the workpiece and as a guide bushing to hold the bar used in manufacturing the parts in position without preventing its rotation. Furthermore, the holding device allows for the passage of bars because it is hollow in the center. This makes it suitable for use in bar turning.

[0027] Regardless of how the workpiece is held, whether by guiding or clamping, the device of the invention ensures significantly better positioning accuracy than prior art devices. This positioning accuracy allows the use of bars with diameter fluctuations of several tenths of a millimeter, while also permitting the machining of parts with a manufacturing tolerance of a few hundredths of a millimeter, a relatively common tolerance in the field of precision mechanics. Consequently, the grinding of bars before machining can be avoided in most cases, without compromising the quality of the finished parts.

[0028] Due to the design of the device of the invention, there is no tangential force on the slides. Consequently, there is no deformation of the slides or displacement of the workpiece, which would lead to inaccuracies during machining. Furthermore, the workpieces can be positioned automatically, and the holding device can be locked very simply, also automatically.

[0029] Another advantage of the device of the invention is that the slides have a relatively large clamping area, and therefore a large contact surface with the workpiece. Furthermore, one end of this clamping area is very close to the area in which the workpiece is machined. Consequently, there is virtually no overhang, which ensures that the workpiece is held rigidly within the device. This further improves machining accuracy.

[0030] It is also possible to design the device with a zone that prevents any chips or unwanted materials from entering the clamping device. These chips can cause various problems such as marking of the parts, friction, machining defects, etc. This zone preventing unwanted materials from entering the clamp can be combined with a pressurized fluid flow that expels the chips and presents a machining area free of any debris.

[0031] According to a particular embodiment of the invention, the holding device may include a compression spring whose function is to adjust the clamping force to the workpiece being machined, so as to ensure optimal holding during machining. This makes it possible to use bars of material having diameter fluctuations, concentricity defects, or other defects that render them unusable with prior art holding devices. SUMMARY DESCRIPTION OF THE DRAWINGS

[0032] The present invention and its advantages will be better understood with reference to the accompanying figures and the detailed description of a particular embodiment, in which: there figure 1 is an exploded view of a part of the device of the invention according to a first embodiment of the invention; the figure 2 is a perspective view of a part of the device of the invention according to a second embodiment; the figure 3 is a perspective view of a part of the device of the invention according to a third embodiment; the figure 4 is a partially cross-sectional view of the device for holding the invention, in a first position known as the open position; the figure 5 is a view similar to the figure 4 , in a second position called closed; the figure 6is a schematic cross-sectional view of a detail of the device of the invention according to a particular embodiment in an open position; the figure 7 is a view similar to the figure 6 , in a closed position; the figure 8 is a schematic cross-sectional view of a variant of the retention device of the invention; the figure 9 is a schematic view of the device of the invention when used on a machine, in the position illustrated by the figure 4 ; there Figure 10 is a view similar to the figure 9 , in the position illustrated by the figure 5 ; there figure 11 is a schematic view of the embodiment of the device of the invention as represented by the figure 8 , used on a machine; the figure 12 is a partially cross-sectional view of a holding device of the invention mounted on a machine, according to a first embodiment; and the figure 13 is a view similar to the figure 12, according to a second embodiment. METHOD OF CARRYING OUT THE INVENTION

[0033] With reference to the figures, the holding device 10 of the invention can take different forms, three of which are illustrated here. One of the forms, called a "wide-opening clamp," is illustrated by the figure 1 Another form, known as a "clamping clamp," is illustrated in particular by the figure 2 The third form, called a "guide barrel," is illustrated by the figure 3 In the present invention, the concept of holding a part encompasses both the concept of clamping and that of guiding.

[0034] The holding device 10 essentially consists of a slide carrier 11, slides 12, and a slide actuating element 13. The slide carrier 11 comprises a body 14 and a head 15. The body 14 is generally cylindrical in shape. Both the body 14 and the head 15 have a central bore 16 with an inner diameter larger than the diameter of the mechanical parts 17 to be held. In other words, the ratio between the dimensions of the central bore and those of the parts to be held is such that the part to be held can be inserted into the central bore. Depending on the application of the holding device, the slide carrier 11 may be designed to be driven in rotation by a machine tool, for example. This rotational drive is achieved conventionally and is not described in further detail here.

[0035] The slide holder 11 can also be designed to hold and guide the mechanical part 17 without rotating. In this case, the part can rotate within the holding device.

[0036] The body 14 of the slide carrier 11 is integral with the head 15, these two elements generally being machined from the same block of material. In the illustrated examples, this head has four lateral bores 19. It is also possible to have fewer lateral bores, for example two or three, or more bores, for example six or eight. The number of bores may depend on the size of the parts to be held, their specific shape, the desired clamping force, etc.

[0037] The head 15 of the slide holder has a conical area 20. The lateral bores 19 open, on the one hand, into the conical area 20 of the head and, on the other hand, into the central bore 16 of this head. The slides 12 are designed to be received, each in a lateral bore 19. The respective dimensions and shapes of the lateral bores 19 and the slides are such that the slides 12 can move longitudinally within the lateral bores 19 with little or no play. This longitudinal movement occurs along an axis substantially perpendicular to a longitudinal axis 20' of the central bore 16. These slides are also designed to protrude slightly from the conical area 20 of the head when they are bearing against the part 17 to be held. It should be noted that, depending on the mechanical part to be held, the slides can be changed.The area of ​​the slide bearing against the workpiece, or clamping area, can thus be adapted to the specific shape of that workpiece. According to a particular embodiment of the invention, the clamping area of ​​the slides has the shape of a circular arc in cross-section. According to an advantageous variant, a cross-section of the slide can present several substantially aligned circular arcs with different radii of curvature. An area with a small radius of curvature can be formed in the center, an area with a slightly larger radius of curvature can border the first area, and a third area with an even larger radius of curvature can surround the first two. This allows for optimal clamping for three different diameters of workpieces or bars to be machined. Clearly, other shapes or a different number of sectors can be considered. Similarly, the length of the slide can be adjusted to the diameter of the workpiece.Depending on the specific application, the retaining device 10 may have more lateral bores 19 than slides 12. For example, it is possible to have a head 15 with six lateral bores and use only three slides. This allows for great flexibility in use.

[0038] In an advantageous embodiment, the slides have a slightly curved front face 21 and rear face 22. This ensures optimal movement and retention of the slides within the corresponding lateral bore. In practice, the dimensions of the slides and the lateral bores are adjusted so that the slides can move with virtually no play or very little play within the bores. This type of adjustment is known as a sliding fit.

[0039] The actuating element 13 of the slides can take different forms. In the embodiments illustrated by the Figures 1 , 4-7, 9 and 10 , this actuation element is a 23 cap.

[0040] This cap has a central passage 24 and a conical inner area 25. It is arranged around the head 15 of the retaining device in such a way that the part 17 held in the central bore of the head and body also passes through the central passage 24 of the cap.

[0041] In the position of use, the conical inner zone 25 of the cap is positioned close to the conical zone 20 of the head.

[0042] When the cap 23 is moved rearward relative to the body, that is, in a direction opposite to the area in which the mechanical part is machined, the conical inner area 25 of the cap bears against the areas of the slides 12 that protrude from the conical area of ​​the head. The contact between these inclined planes has the effect of pressing the slides toward the central bore of the head. These slides 12 move and bear against the mechanical part 17 so as to hold it in place. This movement occurs along an axis substantially perpendicular to the longitudinal axis 20' of the central bore.

[0043] The movement of the slides is achieved through the relative movement of the slide carrier 11 with respect to the cap 23. This relative movement is in principle achieved by moving the slide carrier while keeping the cap immobile.

[0044] According to a preferred embodiment, the movement of the slide carrier 11 forward or backward is achieved by means of hydraulic, electrical or pneumatic means linked to the machine on which the retaining device 10 is installed.

[0045] As can be readily understood, the ratio between the longitudinal displacement of the slide carrier 11 and the transverse displacement of the slides 12 depends on the slope of the conical inner area 25 of the cap. The slope can be defined as the angle formed by a generatrix of the cone with the longitudinal axis 20' of the central bore. The greater this angle, the greater the transverse displacement of the slides will be for the same relative displacement of the cap and the slide carrier. Similarly, the ratio between the longitudinal force applied to the cap and the clamping force of the part 17 also depends on the slope of the conical inner area 25 of the cap 23. The greater this angle, the greater the force that must be applied to the cap for a constant clamping force.

[0046] According to an advantageous variant illustrated by the figures 6 and 7The conical inner zone 25 of the cap can be formed from several conical parts with different angles. For example, a first part 26 may have a high angle allowing for significant movement of the sliders with minimal cap movement. A second part 27 may have a shallower angle to ensure greater clamping force.

[0047] By properly determining the angles of the different parts of the cap, it is possible to optimize the movement of the sliders as well as the clamping forces.

[0048] As can be seen in the figure 1The head 15 has, for each slide 12, a groove 28 arranged to receive a bar 29. The slides 12 each have a transverse slot 30. When the slides are installed, the bar 29 is inserted into the corresponding groove 28 and into the slot 30. The slides also have at least a partially threaded hole 31 having an axis substantially perpendicular to a longitudinal axis of the bar. This hole 31 contains, on one side, a return spring 32 and, on the other side, a preload screw 33. One end of the return spring 32 bears against the bar 29 and the other end against the preload screw 33.

[0049] The function of the return spring 32, which cooperates with the bar 29, is to move the slides 12 outwards from the head when the cap, or more generally the actuating element, is not pressing them towards the central bore. This allows the slides to pass freely for the insertion and removal of the workpiece. The bar 29 can be held in the groove 28 by means of a retaining screw 34.

[0050] The slides as illustrated by the figure 1 include a lower face 35 bearing against the part to be held. This face may have a curved profile designed to fit most parts to be held or, conversely, have a profile specific to the part to be held.

[0051] THE figures 9 to 13 illustrate the holding device 10 of the invention as used on a machine, for example for machining the mechanical part 17 to be held. More specifically, the Figures 9 and 10 illustrate the use of a holding device made in the form of a "wide opening" clamp as illustrated by the figure 1 in particular. The figure 11 concerns a holding device made in the form of a "clamping clamp" illustrated by the figure 2 The embodiment represented by the figure 11 uses a support device represented by the figures 2 And 8 . THE Figures 12 And 13 represent a holding device made in the form of a guide barrel illustrated by the figure 3 .

[0052] In the figure 9 The device is open, allowing the part to be inserted and removed. In the Figure 10 , the slides are pressed towards the center of the central bore so as to hold part 17.

[0053] In the embodiment illustrated by these Figures 9 and 10The cap 23 is integral with a shaft 36 surrounding the body 14 of the retaining device. The slide carrier 11 is mounted on a bushing 37 so as to be integral with it. The bushing receives a conical element 38 that can slide along the shaft 36. The conical element 38 is integral with a cylinder 39 arranged to move this conical element forward and backward.

[0054] The shaft 36 includes two dogs 40 that can pivot about an axis 41 fixed to the shaft 36. The dogs have a rear leg 42 arranged to bear against the socket and a lateral leg 43 arranged to bear against an inclined area of ​​the conical element 38.

[0055] When the cylinder 39 is activated to retract the conical element 38, the lateral tabs 43 of the dogs, bearing against the inclined areas, move away from the central bore 16. The dogs 40 pivot around the axis 41 fixed to the shaft. The ends of the rear tabs 42, bearing against the bushing 37, press the bushing forward. Since the cap 23 is fixed, the forward movement of the slide carrier 11 has the effect of pressing the slides 12 towards the center and thus holding the part 17 between the slides.

[0056] When the cylinder 39 is actuated to bring the conical element 38 forward, the dogs 40 pivot into their position illustrated by the figure 9The rear tabs 42 no longer press the socket forward. The socket can return to its rear position, which has the effect of moving the slide carrier 11 relative to the cap 23. The combined action of the bars 29 and the return springs 32 press the slides 12 outwards and thus release the mechanical part 17.

[0057] In the embodiment illustrated by the figures 8 And 11 The actuating element 13 of the slides is an actuating cylinder 44 disposed around the head 15 and at least part of the body 14 of the slide carrier 11. This actuating cylinder 44 has a cylindrical area 45 in which the body can move longitudinally. It also has a conical area 46 disposed near the head 15 and the slides 12 when the retaining device 10 is mounted.

[0058] In this embodiment, the slide carrier 11 is associated with the actuating cylinder 44 not rigidly as in the embodiment of the Figures 9 and 10 Indeed, the slide carrier 11 can move longitudinally in this actuating cylinder 44. The retaining device 10 may include a cap 47 disposed around the head 15 of the slide carrier 11 and integral with the latter.

[0059] This cap 47 may have the same external appearance as the bonnet 23, but it does not act as an actuating element for the slides. This actuating element is formed by the actuating cylinder.

[0060] The conical area 46 of the actuating cylinder comes into contact with the slides 12 when this actuating cylinder is moved forward. The slide holder 11 is generally held in a fixed longitudinal position by the cap 47 being held in a fixed position.

[0061] This forward movement of the actuating cylinder has the effect of pressing the slides 12 towards the central bore and thus holding the part.

[0062] The movement of the actuating cylinder can be carried out in the same way as the movement of the slide carrier as illustrated by the Figures 9 and 10 .

[0063] Using a bonnet 23 or a cap 47 around the head offers several advantages. For example, it is possible to inject pressurized air or a fluid into the bonnet or cap. This allows for the evacuation of any chips or prevents them from entering the head during machining. This also helps to cool the holding device and the workpiece during machining. Alternatively, a fluid channel can be provided on or within the body 14 of the device for pressurized fluid injection, in order to expel chips and other debris.

[0064] In the embodiment illustrated by the figure 12The holding device 10 of the invention is rigidly fixed to the machine used for machining. This holding device 10 comprises a nut 48 having a ring 49. This ring is provided with holes 50 allowing the nut 48 to be positioned on locking screws 51 attached to the frame 52 of the machining center. The nut is rigidly held against the frame by means of the locking screws 51. The machine frame further includes a guide key 53 cooperating with a groove 54 formed in the body 14 of the holding device 10. This guide key 53 is intended to allow longitudinal guidance of the holding device 10, while preventing its rotation. During the installation of the retaining device, the guide key 53 and the groove 54 are positioned to cooperate, then the device is placed against the frame 52 of the machine and it is fixed by means of the locking screws 51.In this way, the support device is rigid relative to the machine frame.

[0065] In the embodiment illustrated by the figure 13 The retaining device 10 includes a nut 48 similar or identical to the nut illustrated by the figure 12This nut 48 is not, however, rigidly fixed to the machine frame 52. The frame has a recess 53 in which part of the nut 48, and in particular the ring 49 of this nut, can be placed. This recess terminates in a wall 54 facing the front of the machine, that is, towards the area in which the workpiece is machined. Pins 55 attached to the machine frame are positioned so as to pass through the holes 50 in the ring 49 of the nut 48, to prevent rotation of the nut and the retaining device as a whole, while allowing its translation. A compression spring 56 is placed around the nut 48, so as to bear on one side against the ring 49 of the nut and on the other against the wall 54 of the housing 53. This spring 56 has the effect of applying a rearward force on the nut 48 and consequently on the retaining device 10.

[0066] The shape of the holding device is such that this rearward force generates a clamping force on the slides 12. In this way, regardless of the diameter of the workpiece, provided that the diameter remains within a range that the holding device can accommodate, the slides 12 will always apply a constant force to the workpiece. This makes it possible to achieve particularly precise machining, even when concentricity errors and diameter fluctuations are significant. In practice, it is possible to machine parts with tolerances of less than 0.5 mm from bars with diameter fluctuations exceeding 0.7 mm.

[0067] It should be noted that the spring 56 can take several forms. It can be formed, as in the illustrated embodiment, of a single spring, placed around the nut 48. It could be replaced by several springs arranged, for example, around the pins 55 attached to the frame 52. These springs can be formed of elastic leaves or solid elements made of an elastic material, for example.

[0068] As can be seen from the figures 9 to 13, The conical zone 20, which acts on the slides 12 of the holding device, or more generally on the actuating element 13, is integral with the frame 52, unlike prior art holding devices in which the actuating elements are always guided by the holding element itself. The fact that this actuating element is integral with the frame ensures optimal centering and positioning, thus further increasing the machining accuracy of the parts.

[0069] The device according to the invention can be modified without altering its operating principle. The conical areas of the slides can be positioned towards the rear of the head, i.e., towards the body, or conversely, towards the front.

[0070] Thanks to the fact that the slides are independent of each other, the movement of the actuating elements has the effect of centering the part to be held without the use of a specific and complex centering device.

[0071] Thanks to the fact that the actuation elements are centered relative to the machine frame, the positioning of the holding device is particularly precise and allows for particularly precise machining.

Claims

1. A holding device for holding mechanical parts, comprising a slide holder (11) formed of a body (14) and a head (15) provided with a central bore (16, 18) in which a portion of the mechanical part (17) to be held is located, this mechanical part to be held protruding from said head (15), the head comprising a conical area (20), the holding device (10) further comprising at least two sliders (12) and an actuating element (13) for said sliders, the head (15) comprising at least two lateral bores (19) opening on one side into said central bore (16), said sliders (12) being each disposed in one of said lateral bores (19), these sliders (12) being fitted within the lateral bores (19) so as to be able to slide therein, said sliders (12) protruding from the conical area (20) of said head, the actuating element (13) for said sliders being movable longitudinally along the conical area (20) of the head, the movement of said actuating element (13) having the effect of moving said sliders (12) within the respective lateral bores (19) along an axis perpendicular to a longitudinal axis (20') of the central bore (16), characterized in that the at least two lateral bores (19) open on the other side into said conical area (20), in that the head (15) of the slide holder (11) comprises at least one groove (28) passing through the lateral bores (19), in that the sliders (12) comprise a slot (30), in that the holding device (10) comprises a bar (29) passing through the groove (28) and the slot (30) of the slider, and in that the slider (12) comprises a threaded hole (31) arranged for receiving a preload screw (33) and a return spring (32) bearing on one side on the preload screw (33) and on the other side on said bar (29).

2. A holding device according to claim 1, characterized in that the actuating element (13) is a cover (23) covering the head (15) of the slide holder (11), this cover comprising a central passage (24) disposed opposite said central bore (16) and a conical inner area (25) disposed near said conical area (20) of the head of the slide holder.

3. A holding device according to claim 2, characterized in that the conical inner area (25) of the cover (23) comprises at least two parts (26, 27) with different taper angles.

4. A holding device according to claim 1, characterized in that the actuating element (13) is an actuating cylinder (44) disposed at least partially around the slide holder (11) so as to be able to move longitudinally relative to this slide holder, this actuating cylinder (44) comprising a conical area (46) disposed near the sliders (12).

5. A holding device according to claim 4, characterized in that the conical area (46) of the actuating cylinder (44) comprises at least two parts with different taper angles.

6. A holding device according to claim 4, characterized in that the head (15) of the slide holder (11) is at least partially surrounded by a cap (47).

7. A holding device according to claim 1, characterized in that the actuating element (13) and the body (14) are movable relative to each other along the longitudinal axis (20') of the central bore (16) of this body.

8. A holding device according to claim 7, characterized in that the actuating element (13) is rotationally fixed relative to the head (15) of the holding device (10).

9. A holding device according to claim 1, characterized in that it comprises a nut (48) arranged to hold said holding device (10) on a machine tool for machining mechanical parts (17).

10. A holding device according to claim 9, characterized in that the nut (48) comprises a ring (49) provided with holes (50) arranged to cooperate with pins (55) integral with said machine tool.

11. A holding device according to claim 9, characterized in that it comprises a spring (56) disposed between said nut (48) and the machine tool, this spring (56) being arranged to apply a stress on the holding device (10) in a direction opposite to the machining area of the mechanical part.

12. A holding device according to claim 9, characterized in that the actuating element (13) of the sliders (12) is positioned relative to said machine tool.