Radially expanding fastening rings and bushes

Abstract

To provide fastening ring and bush which can withstand dimensional variation of approximately 1 to 2% in a diameter, and can assure simultaneously accurate and repetitive maintenance of a processed component and pressing of the component against a reference plane.SOLUTION: A fastening and retaining ring 1, occupies an interior of a cylindrical storage part which is provided in a base of a component to be immobilized in relation to a main body, is formed from a series of cylindrical and / or pseudo-cylindrical adjacent continuous elements 7, 9 which are combined with each other, these elements have an omega-shaped basic surface, and therefore, include an apex and two branches, the apices of the elements 7, 9 are outside and inside the ring alternately, and form an outer element 7 and an inner element 9 respectively. In the fastening ring, branches connecting two adjacent elements are common, the outer element 7 and the inner element 9 form a [shell], and a thickness of the shell is 10% to 25% of a width of the apex of the outer element 7.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The invention relates to a ring, as well as to a bushing using this ring, intended to effect fastening from a cylindrical recess drilled in the basic face of the part which it occupies, in order to hold the part, in particular the workpiece, on a carrying device, in particular a mandrel, and to press the base of this part against the carrying plane of this device. [Background technology]

[0002] Devices have been proposed which maintain the part relative to a reference or carrying plane and which include cylindrical gripping elements housed in recesses of the same shape and size drilled in the basic surface of the part.

[0003] Such a gripping element includes a peripheral portion made of an elastomer which deforms radially under the action of an actuating mechanism, in particular axially movable, in such a way that its cylindrical portion is pressed with force against the cylindrical portion of the part housing and fixes the part.

[0004] In addition to not exerting any axial force that would allow the base of the part to be held to be pressed onto a reference plane, this gripping element cannot guarantee a hold that provides precise and repeatable positioning.

[0005] Likewise, fastening devices have been proposed which hold a part and at the same time press the base of this part against a reference plane. These fastening devices also have a cylindrical gripping element having an outer surface formed by a number of independent segments or jaws which can move axially on the one hand and radially on the other hand under the action of an axially movable control mechanism.

[0006] Even if such devices are available to ensure that the radial maintenance of the parts and at the same time the pressing of their base against a reference plane are sufficient and therefore repeatable to ensure the maintenance and positioning of the parts, they are not sufficiently accurate, since the manufacturing tolerances of the parts must be very precise, for example of the order of a few μm, since the deployment of the various fastening segments has proven to be particularly sensitive to the various disturbances to which these devices are usually exposed in the centre holes, in particular to files, dust and the like.

[0007] Likewise, fastening rings are known from CH 587094, US 2612376 and CH 454570 which are formed from a series of fastening elements connected to one another, but due to their constructional scale these fastening elements are unable to withstand large radial dimensional variations, which would otherwise exceed the elastic limits of the elements and the ring would lose its resilience or simply break. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Swiss Patent No. 587094 [Patent Document 2] U.S. Patent No. 2,612,376 [Patent Document 3] Swiss Patent No. 454570 Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the invention is to propose fastening rings and bushes which allow to realize fastening of the workpiece parts, capable of withstanding dimensional variations of approximately 1-2% of the diameter, while simultaneously guaranteeing an accurate and repeatable holding of said parts and pressing of said parts against a reference plane.

[0010] The object of the present invention is therefore a fastening and retention ring intended to occupy a cylindrical recess provided in the base of the part to be immobilised in relation to the body, formed by a series of adjacent continuous cylindrical and / or pseudo-cylindrical elements connected to one another, the basic surface of which is omega-shaped and therefore comprises an apex and two branches, the apexes of which are arranged alternately on the exterior and interior of the ring forming respectively an outer element and an inner element, characterized in that the branch connecting two adjacent elements is common, the outer element and the inner element forming a "shell", the thickness of which is between 10% and 25% of the width of the apex of the outer element. [Means for solving the problem]

[0011] According to the invention, at least the outer element or the inner element has a cylindrical shape. Moreover, the outer element or the inner element may have a pseudo-cylindrical shape.

[0012] In one embodiment, the branches connecting two adjacent elements may be "S-shaped." In another embodiment, these branches may be straight.

[0013] Finally, the interior surface of the bulkhead of the inner or outer element having the apex for the base may include a thickened portion.

[0014] The invention also concerns a fastening bushing using a fastening ring as defined above, in which the ring can be extended axially on one side thereof by struts terminating in legs, which can be oriented radially towards the exterior or towards the interior of the bushing.

[0015] The invention also aims at a fastening device for holding a part and pressing it against a bearing plane, the base of which has a cylindrical recess for receiving a fastening ring as defined above, the fastening device may include a cylindrical mandrel body bored with an axial bore in which is mounted in sliding fashion a piston having a frustoconical head bearing against the frustoconical inner surface of the fastening ring, the control means being able to move the piston axially to exert on the inner surface of the fastening ring a radial force capable of radially deforming said ring and pressing its outer surface against the cylindrical partition of the recess and the base of the part against the bearing plane (59).

[0016] The invention also has as its object a fastening device for holding a part having a base bored with a cylindrical recess for receiving a fastening ring of a fastening bush as defined above, comprising a cylindrical mandrel body, which is provided at one end with a boss around which is occupied a post of the fastening bush terminating in a leg which is to be pressed against the mandrel body, the base of the part to be held rests on one side of a collar, the other side of which rests on the mandrel body, which bores an axial bore in which a piston having a frustoconical head which rests on the frustoconical inner surface of the ring is assembled in sliding manner, the control means being capable of displacing said piston axially to exert on the inner surface of the ring a radial force capable of radially deforming it and pressing its outer surface against the cylindrical bulkhead of the recess, the leg being capable of being maintained pressed against the mandrel body by the collar.

[0017] Embodiments of the invention will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which: FIG. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a top view of a fastening ring according to the present invention. [Diagram 2] FIG. 2 is a perspective view of the fastening ring shown in FIG. [Diagram 3] FIG. 3 is a partial enlarged view of the fastening ring shown in FIGS. [Figure 4] FIG. 13 is a front view of a modified embodiment of the fastening ring according to the present invention. [Diagram 5] FIG. 5 is a partial enlarged view of the ring shown in FIG. 4. [Figure 6] 1 is an axial, longitudinal cross-sectional view of a fastening mandrel for a workpiece using a fastening ring according to the present invention, the mandrel being shown in a pre-fastening position. [Figure 7] FIG. 13 is a perspective view of a modified embodiment of a fastening bush according to the present invention. [Figure 8] FIG. 13 is a perspective view of a modified embodiment of a fastening bush according to the present invention. [Figure 9] 1 is an axial and longitudinal section of a fastening mandrel for fastening workpieces using a fastening bush according to the invention, the mandrel being represented in a pre-fastening position. [Figure 10] FIG. 10 is an axial, longitudinal cross-sectional view of the fastening mandrel of FIG. 9 shown in the fastening position. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Figure 1 represents an embodiment of a fastening ring 1 according to the invention, which is intended to occupy a cylindrical recess 3 drilled in the base 5a of the workpiece 5 which it is desired to maintain, as represented in Figure 6.

[0020] The ring 1, shown in a front view in FIG. 1 and in a perspective view in FIG. 2, forms an annulus having, in this embodiment, a cylindrical shape and an outer surface with an outer diameter equal to the diameter of the cylindrical receiving portion 3, and an inner surface with a frusto-conical shape, as will be explained below.

[0021] More precisely, the fastening ring 1 is formed by a series of consecutive elements brought together. The basic surface of each of these elements, represented in figure 3, is in the shape of an Ω, thus comprising an apex and two branches. The different elements are arranged in such a way that their apexes are alternately arranged on the exterior and interior of the ring, so that the inner surface of each Ω opens alternately towards the interior and exterior of the ring.

[0022] Thus, the outer apex 7a has an end connected to two branches 7b and 7c which are common to the two adjacent elements, and so the inner apex 9a is provided with two identical branches 7b and 7c.

[0023] This basic surface thus defines, together with a generatrice line represented by the height h of the ring 1, cylindrical elements, namely a cylindrical element 7 called outer element, which is connected to the outer apex 7a, and a cylindrical element 9 called inner element, which is connected to the inner apex 9a of the base. The thicknesses of the apexes 7a and 9a as well as of the branches 7b and 7c are approximately equal and of small value, between 10% and 25% of the width a of the outer apex 7a.

[0024] Under these conditions, it is understood that the structure of the cylindrical outer element 7 and the inner element 9 is of the type hereinafter called "shell", i.e. of small thickness. Such a structure is extremely advantageous in that it makes it possible to endow the ring with a good elasticity that allows it to undergo large radial deformations while remaining within its elastic deformation zone, thus ensuring an effective fastening of the parts to be maintained as will be explained below.

[0025] It should be noted that the inner elements 9 are not strictly cylindrical due to the taper of the inner surface of the ring, and will be described herein as "quasi-cylindrical", i.e. they have a cylindrical shape except for the inner surface that is connected to their apex 9a. This frusto-conical surface serves to ensure radial deformation of the ring in this embodiment of the invention, as will be explained below.

[0026] As shown in Figures 1 to 3, and in particular in Figure 3, the branches 7b and 7c have an overall orientation of radial type, but can have an "S-shaped" structure, in which the part of the branch closer to the apex is convex when viewed from the outside and the opposite part closer to the end is concave.

[0027] Such an arrangement makes it possible to further improve the deformation capacity of the ring: it is understood that in this arrangement, and unlike prior art rings, the branches work in partial flexure, as a result of which the flexibility of these branches and therefore their radial deformation capacity is further improved.

[0028] By adjusting the thickness of the bulkheads of the shells forming the outer element 7 and the inner element 9, as well as the magnitude of the S-shaped curvature, the user can thus control the deformability of the ring depending on the type of fastening he wishes to perform.

[0029] It has been determined that in such a shell-type structure, the maximum stress zone, which the ring experiences during its radial deformation, is located at the central level of the apices 7a and 9a of the cylindrical outer element 7 and the quasi-cylindrical inner element 9, respectively. In order to improve the strength of these elements, a thickened portion 11 has been provided in the center of the inner surface of the apices 7a and 9a.

[0030] According to the present invention, if it is desired to increase the rigidity of the fastening ring, the user can decrease the curvature of the S-shaped branches and arrive at straight branches 7b, 7c, as represented in Figures 4 and 5.

[0031] 6 shows, by way of example, an embodiment of a fastening ring 1 according to the invention applied to the realization of a mandrel 15 for ensuring the retention of a workpiece 5. For this purpose, as specified above, the base 5a of this part is drilled with a recess 3 for receiving the fastening ring 1.

[0032] The mandrel 15 includes a cylindrical mandrel body 17 which is disposed in an orifice 18 of a tool support 20 and is secured therein by screws 23 .

[0033] The upper portion of the mandrel body 17 terminates in a cylindrical boss 19 around which is disposed a support ring 21 and on which the fastener ring 1 is disposed.

[0034] The mandrel body 17 is drilled with an axial bore 25 in which a cylindrical control piston 27 is slidingly assembled, the upper end of which is provided with a head 29 of frusto-conical outer shape and of larger diameter in the figure, the inclination angle of this frusto-conical shape in relation to the longitudinal axis yy' of the mandrel being identical to that of the inner bore of the fastening ring 1.

[0035] A plate 31 forming a lid and including two circular bosses, an upper boss 31a and a lower boss 31b, is integral with the mandrel body 17 by screws 33 with spacers 35 interposed therebetween.

[0036] The axial bore 25 of the mandrel body 17 opens in its lower part into an externally opening larger diameter axial bore 37. The bottom of a piston 39, around which a packing 40 for the axial bore 37 is provided, is placed in this axial bore and is fixed to the base of the piston 27 by means of screws 41. A make-up passage for pressurized hydraulic oil opens into the bore 37.

[0037] This supply channel is closed by a lid 45 which is fixed on the mandrel body by means of screws 46. This lid 45 includes a boss 47 which penetrates into the bore 37 and is provided with an annular gasket 49 which ensures the tightness of this bore between the outside and itself. Furthermore, a hydraulic oil supply channel 51 passes through the lid 45.

[0038] Under these conditions, if hydraulic fluid is taken into the bore 37 by the supply passage 43, it moves the control piston 27 downwards and thus the frustoconical periphery of the head 29 of this piston exerts on the fastening ring 1 at its contact surface a normal force which can be resolved into a radial force which deforms the fastening ring 1 and presses it against the cylindrical inner bulkhead of the container 3, and an axial force which presses its base against the support ring 21, thus maintaining the workpiece 5 in this position.

[0039] When it is desired to release the workpiece 5, especially after machining, the inflow of this fluid is reversed by taking in pressurized fluid through the supply channel 51, thus lifting the piston 27. However, if the taper of the contact surfaces of the fastening ring 1 and the piston head 29 is small, these two elements may adhere to each other, and the fastening ring 1 will then rise simultaneously with the piston 27, until its upper surface comes into contact with the lower circular boss of the lid, causing them to separate.

[0040] The plate 31 therefore performs two functions: that of a lid protecting the device against dirt and contaminating elements, and that of separating the fastening ring 1 and the piston head 29 during the disassembly phase of the part 5 .

[0041] Of course, it is also conceivable that it would be possible to utilize the force of the actuating means to reverse the taper of the fastening ring 1 and the piston head 29 .

[0042] FIG. 7 shows a fastening bush 1a consisting of a fastening ring 1 as described above, extended on one side, i.e. downwards in the figure, by a retaining part 54 consisting of a post 55 terminating in an outwardly directed leg 57, the function of which will be specified below.

[0043] FIG. 9 represents an example of the application of this fastening bush in a mandrel of the same type as previously described, for which the same reference numbers will be retained.

[0044] In this application, the posts 55 of the retaining portion 54 of the fastening bushing 1a fit over the bosses 19 of the mandrel body 17, and the legs 57 of this bushing bear against the upper surface of the mandrel body.

[0045] The retaining collar 59 rests against the mandrel body 17 and is fixed to it by means of screws 61. A bore 63 is made in the base of this collar 59 so that the collar 59 can rest against the leg 57 of the retaining part 54 in such a way as to ensure its fixation in relation to the mandrel body 17.

[0046] The upper surface 59a of the retaining collar 59 further forms a receiving plane for receiving the base 5a of the workpiece 5. Thus, in this embodiment of the invention, the collar 59 performs two functions, namely that of retaining the leg 57 of the fastening bush 1a and that of a receiving plane for the workpiece 5, thus ensuring precise positioning of this part along the axis yy' of the mandrel.

[0047] It should be noted that the respective diameters of the piston head 29 and the frusto-conical inner bore of the fastening bushing 1a are such that, in the pre-fastening position as shown in FIG. 9, there is play between the piston head 29 and the upper surface of the boss 19, which allows for subsequent vertical movement of the piston 27, as will be explained below.

[0048] In order to press the workpiece 5 against the upper surface 59a of the retaining collar 59 and to keep it in this position, the piston 27 is lowered by taking hydraulic fluid into the bore 37 by the supply channel 43, as explained above, so that the frustoconical periphery 29a of the piston head 29 exerts on the fastening ring 1 of the bush 1a a normal force which is resolved into radial and axial components with respect to its contact surface. These radial and axial forces are retransmitted by the bush 1a to the workpiece, so that, on the one hand, the base of the workpiece is pressed against the upper surface 59a of the retaining collar 59, which performs the function of a receiving plane, as represented in FIG. 10, and, on the other hand, the maintenance of the workpiece in this position is ensured.

[0049] As in the previous example, when it is desired to release the part 5, the hydraulic oil supply in the channel 43 is reversed towards the channel 51, which then raises the piston 27, which then releases the fastening ring 1 from the bush 1a, which is thereby simultaneously released from its integration with the workpiece 5.

[0050] Of course, it is also possible to use fastening bushes in which the legs 57 arranged at the ends of the posts are no longer oriented towards the outside of the bush but towards the inside, as shown in FIG. 8.

[0051] The invention thus makes it possible to realize cylindrical and / or pseudo-cylindrical elements that, due to their "shell" type construction, allow the construction of fastening rings and bushes that have an excellent radial deformation capacity and thus may have an axial expansion or contraction capacity of approximately 1% to 2% of their diameter.

[0052] The designer can thus adjust the stiffness of the fastening rings and bushings according to the radial fastening forces he wishes to transmit and according to the expansion desired for these fastening rings and bushings.

[0053] Thus, for a given material of the fastening ring and / or bush and for its specified diameter, the designer can adjust the number of elements used as well as their shape and, naturally, the thickness of the shells constituting the cylindrical and / or pseudo-cylindrical elements.

[0054] Preferably, the fastening bush may consist of spring steel, in particular a steel with a high silicon content, for example a type of steel called 45SCD7, or any other steel with a high elastic limit.

[0055] Of course, it is possible to use other means for the actuation of the fastening bush than a piston with a frustoconical head acting on a frustoconical portion complementary to the fastening bush, so that according to the invention it is possible to use the force of a cylindrical type actuation means, the diameter of which increases, exerting a radial force on the inner surface of the fastening bush.

[0056] Similarly, it is contemplated that an actuation means using an inverted frustoconical surface could be employed.

[0057] Moreover, it is contemplated that the fastening ring may be constructed with inner and outer elements that are both completely cylindrical.

[0058] Finally, it is considered that it is likewise possible to use the fastening rings and bushes according to the invention while subjecting them to a radial force exerted from their exterior towards their interior, causing them to undergo radial contraction.

Claims

1. A fastening device for holding a part (5) to be immobilized relative to a body and for pressing said part (5) onto a carrying plane (59), comprising: a base (5a) of said part (5), a fastening and retaining ring (1) adapted to occupy a cylindrical recess (3) provided in the base (5a) of said part (5), said fastening ring (1) being formed of a series of adjacent continuous cylindrical and / or quasi-cylindrical elements (7, 9) connected to one another, the basic surface of which is omega-shaped and therefore comprises a top (7a, 9a) and two branches (7b, 7c), the tops (7a, 9a) of said elements (7, 9) being arranged alternately on the exterior and interior of said fastening ring (1) forming respectively an outer element (7) and an inner element (9), said branches (7b, 7c) connecting two adjacent said elements (7, 9) being common, the thickness of said tops (7a, 9a) as well as the thickness of the branches (7b, 7c) being of approximately equal and small value and being between 10% and 25% of the width (a) of the top (7a) of said outer element (7), A fastening device having a perforated cylindrical recess (3) for receiving a retaining ring (1), characterized in that the inner surface of the partition of the inner element (9) or the outer element (7) having the top (7a, 9a) for the base comprises a thickened portion (11), a cylindrical mandrel body (17) drilled with an axial bore, in which a piston (27) having a frusto-conical head (29) bearing on the frusto-conical inner surface of the fastening ring (1) is assembled in sliding manner, said control means being capable of axially moving said piston (27) to exert on the inner surface of the fastening ring (1) a radial force capable of radially deforming said fastening ring (1) and of pressing its outer surface against the cylindrical partition of the receiving part (3) a base (5a) of said part (5) against said bearing plane (59).

2. Fastening device according to claim 1, characterized in that at least the outer element (7) or the inner element (9) has a cylindrical shape.

3. 2. Fastening device according to claim 1, characterized in that the outer element (7) or the inner element (9) has a quasi-cylindrical shape.

4. Fastening device according to any one of claims 1 to 3, characterised in that the branches (7b, 7c) connecting two adjacent elements (7, 9) are "S-shaped".

5. Fastening device according to any one of claims 1 to 3, characterized in that the branches (7b, 7c) connecting two adjacent elements (7, 9) are straight.

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