Clamping ring and sleeve with radial expansion

Description

[0001] The present invention relates to a ring and a sleeve implementing the latter which are intended to ensure clamping with a view to holding a part, in particular a part to be machined, on a supporting device, such as in particular a chuck, and to apply the base of this part against a supporting plane of this device, and this from a cylindrical housing hollowed out in the base face of said part, in which said ring is placed.

[0002] Devices have been proposed for holding a part relative to a reference plane, or carrier plane, which for this purpose comprise a cylindrical gripping element which fits into a housing of the same shape and dimensions hollowed out in the base face of the part.

[0003] Such gripping elements comprise, on their periphery, a part made of an elastomer which deforms radially under the action of an actuating member, in particular axially movable, so that its cylindrical part comes to be applied with force against the cylindrical part of the housing of the part, thus ensuring the blocking of the latter.

[0004] These gripping elements, in addition to the fact that they do not exert any axial force on the part to be held, allowing the base of the latter to be applied to a reference plane, are not able to ensure a hold achieving precise and repetitive positioning.

[0005] Clamping devices have also been proposed which ensure both holding of the part and application of the base of the part against a reference plane. These clamping devices also have a cylindrical gripping element whose external surface is formed of a multiplicity of independent segments, or jaws, which are capable of moving on the one hand radially and on the other hand axially under the action of an axially movable control member.

[0006] Although such devices do indeed ensure both radial support of the part and application of the base of the part to a reference plane, and are therefore usable for ensuring support and positioning of the part which is repetitive, they are however not of sufficient precision when the manufacturing tolerances of the part must be ultra-precise, for example of the order of a few µm, insofar as the deployment of the various clamping segments has proven to be particularly sensitive to the various disturbances to which these devices are usually exposed in machining centers, such as in particular filings, dust, etc.

[0007] Also known from patents CH 587094, US 2612376 and CH 454570 are clamping rings which are formed from a succession of clamping elements linked together. However, these clamping elements, due to their massive constitution, are not capable of undergoing significant radial dimensional variations without exceeding their elastic limit, which implies either non-reversibility of the ring or pure and simple rupture of the latter.

[0008] FR 1 047 719 A and US 3 438 660 A disclose clamping rings having apexes.

[0009] The present invention aims to propose a clamping ring and sleeve capable of undergoing dimensional variations of the order of 1 to 2% of their diameter and making it possible to clamp a workpiece which ensures both precise and repetitive holding of the latter as well as the application of its base to a reference plane.

[0010] The present invention thus relates to a clamping and holding ring according to claim 1 intended to be placed in a cylindrical housing made in the base of a part that it is desired to immobilize relative to a body, this ring being formed from a series of successive adjacent cylindrical and / or pseudo-cylindrical elements which are linked together and whose base surface is omega-shaped and thus comprises a top and two branches, the tops of these elements being alternately arranged on the outside and on the inside of the ring and respectively forming an external element and an internal element, characterized in that the branches connecting two adjacent elements are common and the external elements and the internal elements form "shells" whose thickness is between 10% and 25% of the width of the tops of the external elements.

[0011] The external elements or the internal elements may be cylindrical in shape. Furthermore, the external elements or the internal elements may be pseudo-cylindrical in shape.

[0012] In one implementation mode, the branches that connect two adjacent elements may be “S” shaped. In another implementation mode, these branches may be straight.

[0013] Finally, the inner face of the walls of internal or external elements having a summit as a base has an excess thickness.

[0014] The present invention also relates to a clamping sleeve implementing a clamping ring as defined above, this ring being able to extend axially on one side thereof by a leg ending in feet. These feet may be oriented radially towards the outside or towards the inside of the sleeve.

[0015] The present invention also relates to a clamping device intended for holding a part and applying it to a supporting plane, the base of the part being hollowed out with a cylindrical housing receiving a clamping ring as defined above, this device being able to comprise a cylindrical mandrel body hollowed out with an axial bore in which will be slidably mounted a piston whose frustoconical head can be in abutment against a frustoconical internal surface of the clamping ring, control means being able to move this piston axially so as to exert on the internal surface of the clamping ring a radial force capable of deforming it radially and applying its external surface against the cylindrical wall of the housing and the base of the part against the supporting plane.

[0016] The present invention also relates to a clamping device intended for holding a part whose base is hollowed out with a cylindrical housing receiving the clamping ring of a clamping sleeve as determined previously, this device being able to comprise a cylindrical chuck body one of the ends of which will be provided with a boss around which the legs of the clamping sleeve will be placed, which end in feet which will be applied against the chuck body, the base of the part to be held coming to bear on one face of a collar the other face of which will itself bear on the chuck body, the latter being hollowed out with an axial bore in which will be slidably mounted a piston whose frustoconical head will bear against the frustoconical internal surface of the ring,control means being capable of moving this piston axially so as to exert on the internal surface of the ring a radial force capable of deforming it radially and applying its external surface against the cylindrical wall of the housing. Furthermore, the feet may be kept applied against the mandrel body by the collar.,

[0017] Embodiments of the present invention will be described below, by way of non-limiting example, with reference to the appended drawing in which: there figure 1 is a top view of a clamping ring according to the invention, the figure 2 is a perspective view of the clamping ring shown in the figure 1 , there figure 3 is an enlarged partial view of the clamping ring shown in the figures 1 et 2 , there figure 4 is a front view of an alternative embodiment of a clamping ring according to the invention, the figure 5 is an enlarged partial view of the ring shown in the figure 4 , there figure 6 is an axial and longitudinal sectional view of a chuck for clamping a workpiece using the clamping ring according to the invention, the chuck being shown in a pre-clamping position, the figures 7 et 8 are perspective views of two variants of implementation of a clamping sleeve according to the invention, the figure 9 is an axial and longitudinal sectional view of a chuck for clamping a workpiece by means of a clamping sleeve according to the invention, the chuck being shown in a pre-clamping position, the figure 10 is a partial axial and longitudinal sectional view of the clamping chuck of the figure 9 , which is shown in the clamping position.

[0018] There figure 1 represents an exemplary embodiment of a clamping ring 1 according to the invention. This ring is intended to take place in a cylindrical housing 3 which is hollowed out in the base 5a of a workpiece 5 which it is desired to hold, as shown in the figures 6 .

[0019] Ring 1, which is shown in front view on the figure 1 and in perspective on the figure 2 , forms a ring whose external surface, in the present embodiment, is cylindrical in shape and has an external diameter equal to the diameter of the cylindrical housing 3 and the internal surface is truncated in shape as explained below.

[0020] More precisely, the clamping ring 1 is formed from a series of successive elements which are joined together. The base surface of each of these elements, which is shown on the figure 3 , is Ω-shaped so that it comprises a vertex and two branches. These different elements are arranged in such a way that the vertex is alternately arranged on the outside and on the inside of the ring 1 so that the internal surface of each Ω is alternately open towards the inside and towards the outside of the ring.

[0021] We thus have an external vertex 7a whose ends are connected to two branches 7b and 7c and an internal vertex 9a provided with the same two branches 7b and 7c, since the latter are common to two adjacent elements.

[0022] This base surface thus defines with the generator represented by the height hof the ring 1 of the cylindrical elements, namely a cylindrical element 7 called the external element which is associated with the external vertex 7a and a cylindrical element 9 called the internal element which is associated with the internal vertex 9a of the base. The thickness of the vertices 7a and 9a as well as the thickness of the branches 7b and 7c are substantially equal and of low value and are between 10% and 25% of the width a of the external vertex 7a.

[0023] Under these conditions, it is understood that the structure of the external 7 and internal 9 cylindrical elements is of the type referred to hereinafter as "shell", that is to say of a small thickness. Such a structure is particularly interesting in that it makes it possible to give the ring good elasticity allowing it significant radial deformation while remaining within the range of its elastic deformation, which in particular allows it to ensure effective clamping of the parts to be held as explained below.

[0024] It will be noted that the internal elements 9, due to the conicity of the internal surface of the ring, are not strictly cylindrical and will be referred to in the present text as “pseudo-cylindrical”, that is to say that these elements are of cylindrical shape with the exception of the internal surface associated with their apex 9a. This frustoconical surface serves, in the present embodiment of the invention, to ensure the radial deformation of the ring as explained below.

[0025] As depicted on the figures 1 à 3 and in particular on the latter, the branches 7b and 7c are of a general radial type direction but may have an “S” structure, the part of the branches close to the top being, seen from the outside, convex in shape and the opposite part close to the end being concave in shape.

[0026] Such an arrangement makes it possible to further improve the deformation capacity of the ring. It is understood that in this arrangement and unlike the rings of the prior art, the branches work partly in flexion, which has the consequence of further improving their flexibility and therefore their radial deformation capacity.

[0027] By playing on the importance of the S-curvature, as well as on the thickness of the wall of the shell forming the external elements 7 and the internal elements 9, the user will thus have the possibility of controlling the deformability of the ring, and this according to the type of tightening that he wishes to carry out.

[0028] It was found that in such a shell-type structure the maximum stress zones experienced by the ring during its radial deformation were located at the midpoint of the respective vertices 7a and 9a of the external cylindrical elements 7 and the internal pseudo-cylindrical elements 9. In order to improve the strength of these elements, an excess thickness 11 was made in the center of the internal surface of the vertices 7a and 9a.

[0029] According to the invention, when the user wishes to increase the rigidity of the clamping ring, he has the possibility of reducing the curvature of the S-shaped branches and arriving, as shown in the figures 4 et 5 to branches 7b, 7c which are straight.

[0030] It has been represented on the figure 6 , by way of example, an embodiment of the clamping ring 1 according to the invention applied to the production of a mandrel 15 intended to ensure the holding of a part to be machined 5. For this purpose, as previously specified, the base 5a of the latter is hollowed out with a housing 3 intended to receive the clamping ring 1.

[0031] The chuck 15 comprises a cylindrical chuck body 17 which is arranged in an orifice 18 of a tool holder 20 in which it is fixed by screws 23.

[0032] The upper part of the chuck body 17 ends with a cylindrical boss 19 around which is arranged a support ring 21 on which the clamping ring 1 is arranged.

[0033] The mandrel body 17 is hollowed out with an axial bore 25 in which a cylindrical control piston 27 is slidably mounted and the upper end of which, in the drawing, is provided with a head 29 of larger diameter and of truncated external shape, the angle of inclination of this truncated cone relative to the longitudinal axis yy' of the mandrel being identical to that of the internal bore of the clamping ring 1.

[0034] A plate 31 forming a cover and comprising two circular bosses, namely an upper boss 31a and a lower boss 31b, is secured to the mandrel body 17 by a screw 33 with the interposition of a spacer 35.

[0035] The axial bore 25 of the mandrel body 17 opens at its lower part into an axial bore 37 of larger diameter which opens to the outside. A piston base 39 whose periphery is provided with a seal 40 with the axial bore 37 is arranged in the latter and is fixed to the base of the piston 27 by a screw 41. A pressurized hydraulic fluid supply channel 43 opens into the bore 37.

[0036] The latter is closed by a cover 45 which is fixed on the chuck body by screws 46. This cover 45 has a boss 47 which penetrates into the bore 37 and which is provided with an O-ring 49 ensuring the sealing of this bore with the outside. Furthermore, the cover 45 is crossed by a hydraulic fluid supply channel 51.

[0037] It is understood under these conditions that, when the hydraulic fluid is admitted into the bore 37 by the supply channel 43, it moves the control piston 27 downwards, so that the frustoconical periphery of the head 29 thereof exerts on the clamping ring 1 a force normal to its contact surface, decomposing into a radial force which deforms the clamping ring 1 and applies it against the cylindrical internal wall of the housing 3 and an axial force which applies the base of the clamping ring 1 against the support ring 21, ensuring that the part to be machined 5 is held in this position.

[0038] When, in particular after machining, it is desired to release the workpiece 5, the arrival of the pressurized fluid is reversed by admitting it through the supply channel 51, which has the effect of lifting the piston 27. However, if the conicity of the contacting surfaces of the clamping ring 1 and the piston head 29 is small, these two elements risk adhering to each other and the clamping ring 1 then lifts at the same time as the piston 27, and this until the upper surface of the clamping ring 1 comes into contact with the lower circular boss 31b of the cover, which has the effect of separating them.

[0039] The plate 31 thus performs two functions, namely a cover function ensuring protection of the device against dirt and polluting elements and a function of separating the clamping ring 1 and the piston head 29 during the disassembly phase of the part 5.

[0040] Of course, it would also be possible to use actuating means in which the conicities of the clamping ring 1 and the piston head 29 would be reversed.

[0041] It has been represented on the figure 7 a clamping sleeve 1a which consists of a clamping ring 1, as described previously, which is extended on one of its sides, namely downwards in the figure, by a retaining part 54 which consists of legs 55 which end in feet 57 facing outwards, the role of which will be specified below.

[0042] It has been represented on the figure 9 an example of application of this clamping sleeve in a chuck of the same type as described previously and the same references will be kept for this example.

[0043] In this application, the legs 55 of the retaining part 54 of the clamping sleeve 1a fit onto the boss 19 of the chuck body 17 and the feet 57 of the latter come to bear on the upper face of the chuck body.

[0044] A retaining collar 59 rests on the chuck body 17, to which it is fixed by screws 61. A bore 63 is made at the base of the collar 59 so that it can rest on the feet 57 of the retaining part 54, so as to ensure its fixing relative to the chuck body 17.

[0045] The upper face 59a of the holding collar 59 further forms a receiving plane intended to receive the base 5a of the workpiece 5 to be machined. Thus, in this embodiment of the invention, the collar 59 performs two functions, namely a function of retaining the feet 57 of the clamping sleeve 1a and a function of receiving plane of the workpiece 5 to be machined, thus ensuring precise positioning of the latter along the axis yy' of the chuck.

[0046] It will be noted that the respective diameters of the piston head 29 and of the truncated internal bore of the clamping sleeve 1a are such that, in the pre-tightening position, as shown in the figure 9 , there is a clearance between the base of the piston head 29 and the upper face of the boss 19, clearance allowing subsequent vertical movement of the piston 27, as explained below.

[0047] To apply the workpiece 5 against the upper face 59a of the retaining collar 59 and hold it there in this position, and as explained previously, the piston 27 is lowered by admitting the hydraulic fluid into the bore 37 via the supply channel 43, so that the frustoconical periphery 29a of the piston head 29 exerts on the clamping ring 1 of the sleeve 1a a force normal to its contact surface, decomposed into a radial component and an axial component. These radial and axial forces are retransmitted to the workpiece 5 by sleeve 1a, which has the effect, as shown in the figure 10 , on the one hand to apply the base of the latter against the upper face 59a of the retaining collar 59, ensuring the function of receiving plane and on the other hand to ensure the maintenance of the part to be machined 5 in this position.

[0048] As in the previous example, when it is desired to release the part 5, the hydraulic fluid supply is switched from channel 43 to channel 51 and the hydraulic fluid then lifts the piston 27 which thus releases the clamping ring 1 of the sleeve 1a from any radial force, so that the latter is at the same time separated from the part to be machined 5.

[0049] It is also possible, of course, to use a clamping sleeve in which the feet 57 arranged at the end of the legs are oriented not towards the outside but towards the inside of the sleeve, as shown in the figure 8 .

[0050] The present invention thus makes it possible, due to the “shell” type structure, to produce cylindrical and / or pseudo-cylindrical elements which have an excellent radial deformation capacity, thus making it possible to form clamping rings and sleeves which can have an axial expansion or contraction capacity of the order of 1% to 2% of their diameter.

[0051] It is thus possible for the designer to adjust the rigidity of the ring and the clamping sleeve according to the radial clamping force that he wishes to transmit and according to the desired expansion of these.

[0052] For a given material of the ring and / or the clamping sleeve and for a given diameter of the latter, it will thus be possible to play on the number of elements used as well as on their shape and of course on the thickness of the shells constituting the cylindrical and / or pseudo-cylindrical elements.

[0053] Preferably, the clamping sleeve may be made of spring steel, in particular a steel with a high silicon content, such as, for example, a steel of the so-called 45SCD7 type or any other steel with a high elastic limit.

[0054] Of course, the device for actuating the clamping sleeve may use means other than a piston with a truncated conical head acting on a complementary truncated conical part of the clamping sleeve. It would thus be possible, according to the invention, to use cylindrical type actuating means whose increase in diameter would exert a radial force on the internal surface of the clamping sleeve.

[0055] Alternatively, actuation means using an inverted truncated cone surface could be used.

[0056] Furthermore, the clamping ring could be made up of internal and external elements, each of which would be entirely cylindrical.

[0057] Finally, the ring and the clamping sleeve according to the invention could also be used by subjecting them to a radial force exerted from the outside towards the inside of them, so as to cause them to undergo a radial contraction.

Claims

1. A clamping and holding ring (1) for being placed in a cylindrical housing (3) made in the base (5a) of a part (5) desired to be immobilised with respect to a body, this clamping ring (1) being formed of a series of successive adjacent cylindrical and / or pseudo-cylindrical elements (7, 9) which are connected to each other and whose base surface is omega-shaped and thus includes a vertex (7a, 9a) and two branches (7b), 7c), the vertices (7a, 9a) of these elements (7, 9) being alternately disposed on the exterior and on the interior of the clamping ring (1) and forming respectively an outer element (7) and an inner element (9), the branches (7b, 7c) connecting two adjacent elements (7, 9) being common, wherein the outer elements (7) and the inner elements (9) form "shells" whose thickness is between 10% and 25% of the width (a) of the vertices (7a) of the outer elements (7), the interior face of the walls of the inner (9) or outer (7) elements having a vertex (11) as a base having an extra thickness (11).

2. The clamping and holding ring (1) according to claim 1, characterised in that at least the outer elements (7) or the inner elements (9) are cylindrical in shape.

3. The clamping and holding ring (1) according to claim 1, characterised in that the outer elements (7) or the inner elements (9) are pseudo-cylindrical in shape.

4. The clamping and holding ring (1) according to any of the preceding claims, characterised in that the branches (7b, 7c) that connect two adjacent elements (7, 9) are "S" shaped.

5. The clamping and holding ring (1) according to any of claims 1 to 3, characterised in that the branches (7b, 7c) that connect two adjacent elements (7, 9) are rectilinear.

6. A clamping sleeve comprising a clamping ring (1) according to any of the preceding claims, characterised in that the clamping ring (1) axially extends on one side thereof to a leg (55) terminating in feet (57).

7. The clamping sleeve according to claim 6, characterised in that the feet (57) are radially outwardly or inwardly oriented.

8. A clamping device for holding a part (5) and for applying it to a bearing plane (59), the base (5a) of the part (5) being hollowed out as a cylindrical housing (3), comprising the clamping ring (1) according to one of claims 1 to 5, characterised in that it comprises a cylindrical mandrel body (17) hollowed out as an axial bore (31) in which a piston (27) with a frustoconical head (29) is slidingly mounted bears against a frustoconical inner surface of the clamping ring (1), control means being able to move this piston (27) axially so as to exert on the inner surface of the clamping ring (1) a radial force capable of deforming it radially and applying its outer surface against the cylindrical wall of the housing (3) and the base of the part (5) against the bearing plane (59).

9. A clamping device for holding a part (5) whose base (5a) is hollowed out as a cylindrical housing (3) comprising the clamping ring (1) of the clamping sleeve (1a) according to one of claims 6 or 7, characterised in that it comprises a cylindrical mandrel body (17) one of the ends of which is provided with a boss (19) around which are placed the legs (55) of the clamping sleeve (1a), which terminate in the feet (57) which are applied against the mandrel body (17), the base (5a) of the part (5) to be held bearing against a face of a collar (59) the other face of which is itself bearing against the mandrel body (17), the latter being hollowed out as an axial bore (25) in which a piston (27) is slidingly mounted, the frustoconical head (29) of which is bearing against the frustoconical inner surface of the clamping ring (1), control means being able to move this piston (27) axially so as to exert on the inner surface of the clamping ring (1) a radial force capable of deforming it radially and applying its outer surface against the cylindrical wall of the housing (3), the clamping ring (1) having an axial expansion or contraction capacity in the order of 1% to 2% of its diameter, and being radially deformed while remaining in the region of its elastic deformation.

10. The clamping device according to claim 9, characterised in that the feet (57) are held applied against the mandrel body (17) by the collar (59).