US3750251A

US3750251A - Method and apparatus for setting a diaphragm spring

Info

Publication number: US3750251A
Application number: US00264620A
Authority: US
Inventors: A Pugh; C Morewood
Original assignee: GKN Transmissions Ltd
Current assignee: LuK Lamellen und Kupplungsbau GmbH
Priority date: 1971-06-25
Filing date: 1972-06-20
Publication date: 1973-08-07
Anticipated expiration: 1990-08-07
Also published as: DE2230951A1; GB1384249A; ZA724198B; AU4371172A

Abstract

A method of bringing the inner ends of the fingers of a clutch diaphragm spring into coplanar relation comprising the steps of elastically straining the spring in an outer annular zone to convert it from domed or frusto-conical form into more flattened form, and while it is in this condition bending the inner ends of the fingers to an amount which exceeds the elastic limit of the spring material, the bending taking place about fulcrum elements, the spring pressed into contact with respective fingers and then locked. An apparatus for carrying out the method includes an angularly spaced series of clamping devices for clamping a diaphragm spring within a dished clutch cover member to deform this elastically between the cover member and a pressure plate in an outer zone of the spring, and an axially movable deforming element engaging the inner ends of the fingers while these are supported by spring loaded fulcrum elements locked by roller and wedge mechanisms in the positions in which they first contact the fingers.

Description

United States Patent 1 Pugh et al.

[111 3,750,251 Aug. 7, i973 METHOD AND APPARATUS FOR SETTING A DIAPHRAGM SPRING [75] inventors: Algernon Walter Pugh; Charles Alan Morewood, both of Sheffield, England [73] Assignee: GKN Transmissions Limited,

Warwick, England 221 Filed: June 20, 1912 [21] Appl.No.:264,620

[30] Foreign Application Priority Data Primary Examiner-Charles W. Lanham Assistant Examiner-D. C. Reilley, lll Attorney-Charles J. Merriam, Alvin D. Shulman et [57] ABSTRACT A method of bringing the inner ends of the fingers of a clutch diaphragm spring into coplanar relation comprising the steps of elastically straining the spring in an outer annular zone to convert it from domed or frustoconical form into more flattened form, and while it is in this condition bending the inner ends of the fingers to an amount which exceeds the elastic limit of the spring material, the bending taking place about fulcrum elements, the spring pressed into contact with respective fingers and then locked. An apparatus for carrying out the method includes an angularly spaced series of clamping devices for clamping a diaphragm spring within a dished clutch cover member to deform this elastically between the cover member and a pressure plate in an outer zone of the spring, and an axially movable deforming element engaging the inner ends of the fingers while these are supported by spring loaded fulcrum elements locked by roller and wedge mechanisms in the positions in which they first contact the fingers.

15 Claims, 6 Drawing Figures PATENTEDAUB 11915 a; 750,251

SHEET 1 [1F 4 PATENTEDAUB H915 3.750.251

sum 2 OF 4 METHOD AND APPARATUS FOR SETTING A DIAPHRAGM SPRING BACKGROUND OF THE INVENTION FIELD OF THE INVENTION This disclosure is concerned with a diaphragm spring of the kind comprising a plurality of fingers which are arranged radially with respect to a reference axis in angularly successive positions therearound, each of the 1 fingers being integrally connected at the outer end with an outer annular connecting portion of the spring.

When such a diaphragm spring is in use in an apparatus of which it forms part, the outer annular portion of the spring is strained elastically to vary its shape presented in a cross-sectional diametral plane containing the reference axis so that such portion exerts a force on some associated part of theapparatus in a direction generally parallel to the reference axis, the magnitude of this force being varied by moving the inner ends of the fingers in a direction longitudinally of the reference axis.

One form of apparatus in which such diaphragm springs are commonly employed, and in relation to which the present disclosure has been principally developed, is a friction clutch comprising an assembly 'of driving and driven plates having axially presented faces adapted to be maintained, when the clutch is engaged, in pressure contact with each other by a force exerted by the diaphragm spring which reacts against at least one of said plates and a body member of the clutch. A specific form of clutch of this kind commonly employed as part of the transmission means for transmitting drive from a prime mover such as an internal combustion engine to a driven member has a body member in the form of a dished housing or cover member as it is generally termed, the diaphragm spring being contained in the cover member adjacent to the end wall thereof and reacting between a main fulcrum provided on the cover member in an annular zone inset from the periphery of the diaphragm spring, and a driving plate, normally termed the pressure plate, which is urged towards the mouth of the cover member by the diaphragm spring and serves to clamp a driven plate between the pressure plate and a further driving plate which is constituted by, or provided on, the flywheel or other rotary driven member of the prime mover. When such clutch is installed in its operative position in relation to the prime mover, the outer annular portion of the diaphragm spring is strained elastically from a domed or dished configuration towards a more flattened configuration between the main fulcrum and the pressure plate in consequence of securement of the peripheral wall of the peripheral wall of the cover member to the flywheel or other rotary output member, disengagement of the clutch being effected by axial movement of the inner ends of the fingers towards the pressure plate by way of an annular thrust member.

In clutches forming part of the transmission means of vehicles such as motor road vehicles, it is important that disengagement and engagement of the clutch shall be capable of being controlled precisely by the user in order to ensure smooth take up of the drive, and for this purpose it is necessary that each finger shall, at its inner end, be moved through the same distance in consequence of a given axial movement ofa thrust member engaging all the fingers. Consequently the inner ends of the fingers, as defined by contact faces presented by the fingers, require to lie in coplanar relation in a plane at right angles to the reference axis.

Certain substantial problems exist at the present time in ensuring that this condition is met.

Firstly, the diaphragm springs themselves are ordinarily formed from sheet or plate metal stock which initially is in planar form and which is deformed to produce an outer annular portion for the diaphragm spring in the unstrained form of the spring, the latter being 0 subjected to heat treatment to provide the required spring characteristic for the outer annular portion and for the fingers and to provide a hardness in the surface layers adjacent the contact faces of the fingers to ensure a satisfactory service life for the latter when repeatedly engaged by the thrust member.

In practice, after these operations have been conducted, it is normally found that the inner ends of the fingers are not coplanar, due partly to the existence of differential internal stresses in the metal preparatory to heat treatment, and partly to the metallurgical structure of the metal which normally presents grains which are elongated in the direction of rolling of the stock from which the diaphragm spring has been produced, and which will be presentd lengthwise in some fingers and transversely in other fingers and at varying angles in the remainder of the fingers.

Further, in the production of the component parts of a clutch in which such spring may be incorporated, there are significant dimensional tolerances in the cover member and in the component parts of the main fulcrum provided therein, as-well as possibly in the thickness and hence axial position of the surfaces of the pressure plate engaged by the diaphragm spring.

These tolerances may in some cases be additive and accentuate the effect of non-planar relation of the inner ends of the fingers.

SUMMARY OF THE INVENTION The main object of the present disclosure is to provide a new or improved method of, and apparatus for, the manufacture of diaphragm springs of the kind specified which, whilst designed more especially for use in producing diaphragm springs intended for incorporation in clutches, it is also capable of use in relation to diaphragm springs in general where similar or analogous problems arise.

From one aspect the disclosure resides in a method of setting into coplanar relation in a plane at right angles to a reference axis of a diaphragm spring the inner ends of radially inwardly projecting fingers of said spring integrally connected at their outer ends with an outer annular portion of said spring, said method comprising the steps of elastically straining said spring in an outer zone thereof in a mode corresponding to that in which it is elastically strained under service conditions, subjecting said fingers while said spring is so strained to bending in a direction along said reference axis beyond the elastic limit of the spring material to bring inner ends of said fingers into coplanar relation in said plane.

From a further aspect the disclosure resides in the provision of an apparatus for use in the manufacture of diaphragm springs each having fingers projecting radially inwardly towards the reference axis of said spring, said fingers being integrally connected at their outer ends to an outer annular portion of said spring, said apparatus comprising a body, support means thereon for supporting said spring, means for elastically straining an outer zone of said spring in a mode corresponding to that in which it is strained when in service, finger bending means for bending said fingers in a direction lengthwise of said reference axis beyond the elastic limits of the spring material to a position in which the inner ends of said springs are in coplanar relation with each other in a plane at right angles to said reference axis.

DESCRIPTION OF THE PREFERRED EMBODIMENT The disclosure will now be described, by way of example, with reference to the accompanying drawings wherein:

FIG. I shows diagrammatically in a diametral crosssectional plane containing the axis of a diaphragm spring the stages of a preferred manner of carrying out the method of the invention;

FIG. 2 is a part-plan view showing a typical embodiment of diaphragm spring in which the method illustrated in FIG. I is subjected;

FIG. 3 is a view in a diametral cross-sectional plane containing the axis of the diaphragm spring through certain components ofa clutch in which the diaphragm spring is incorporated;

FIG. 4 is a part-plan view of one embodiment of apparatus in accordance with the invention for carrying out the method illustrated in FIG. 1;

FIG. 5 is a view in side elevation and partly in crosssection of the apparatus shown in FIG. 4; and

FIG. 6 is a view on an enlarged scale of the upper portion of the apparatus shown in FIG. 5 and partly in cross-section.

Referring firstly to FIG. 3, the components of the clutch shown comprise a cover member 10 of generally dished form having an end wall 11, a peripheral wall 12 and a radially projecting flange 13 at the mouth of the cover member which is shown downwardly presented.

Within the cover member is disposed one of the driving plates of the clutch, namely a pressure plate 14, which is urged in a downward direction by the diaphragm spring 15, the outer annular zone of the latter reacting between the main fulcrum structure 16 supported from the end wall 11 of the cover and a series of angularly spaced axial projections 17 on the pressure plate 14. The fulcrum structure comprises a plurality of rivets such as 18 secured in apertures in the end wall 11 extending through repective openings in the diaphragm spring and carrying an annular retainer plate 19. Between the diaphragm spring and the end wall 11 on the one hand and the retainer plate on the other hand wire rings 20 and 21 encircle the rivets l8 and are held by means of the retainer member 19 in contact with opposite sides of the diaphragm spring to twine the main fulcrum.

Further components of the clutch (not shown) comprise a driven plate which is normally of disc-like form and lies immediately beneath the pressure plate 14 within the cover member, and a further driving plate which is constituted by part of, or is secured to, a flywheel or other similar rotary driving member. Such flywheel may, for example, be the flywheel of an internal combustion engine or other prime mover. The cover member 10 is secured to the flywheel or rotary driving member by fastening elements such as bolts passing through holes 22. Further holes 23 are provided with radially projecting lugs 24 of the peripheral wall 12 of the cover member for attachment of the outer end of driving straps, the other ends of which are connected to the pressure plate 14 to transmit torque to the latter from the cover member.

The general form of the diaphragm spring 15 is seen in FIG. 2, from which it will be apparent that the spring includes a plurality of radially arranged angularly successive fingers 25 integrally connected at their outer ends to an outer annular portion 26.

The outer end of each slot 28 between successive fingers 25 is enlarged to form a circular opening for the passage of the rivets 18 already mentioned.

In its unstressed state the diaphragm spring is of generally domed or dished form and it is constrained to take up a more flattened form, as illustrated in FIG. 3, by the upwardly directed forces applied to its peripheral margin from the projections 17 and the downwardly directed forces applied by the main fulcrum 16 when the cover member is bolted to the rotary driving member, the pressure plate 14 is in pressure contact with the driven plate, and the latter clamped between the pressure plate 14 and the drivng plate or portion of the rotary driving member.

Under these conditions it is important that the inner ends 26 of the fingers 25 shall present contact faces, i.e. the upper faces as seen in FIG. 3, which are coplanar with each other and accurately at right angles to the reference axis 29 in order to ensure proper operation of the clutch as previously mentioned.

Also, as mentioned, one of the factors which contributes to departure from this condition is that, after stamping of the diaphragm spring from sheet metal or plate metal stock such as steel, it is subjected to heat treatment to achieve the requisite degree of hardness in the outer portion 27 as well as in the fingers. Ordi narily the greatest hardness is attained in the inner zone indicated at II containing the fingers, and a somewhat lesser degree of hardness in the outer annular zone I containing portion 27.

In consequence of stresses produced during severence of the diaphragm spring from the metal stock, and during permanent deformation to convert the stamped out blank into generally dished shape, the inner ends 26 of the fingers, as defined by their contact faces, move into non-coplanar relation. This effect is accentuated in some cases by virtue of the fact that the direction of elongation of the metallic grains will run longitudinally, i.e., radially, in certain fingers and transversely in others.

Yet another cause of departure from coplanar relation of the inner ends 26 is the existence of dimensional variations (within the tolerance of manufacture) in the cover member 10 and in the pressure plate 14. For example, the end wall 11 of the pressure plate may have a regular or irregular wave-like distortion proceeding circumferentially therearound and possibly the axial length of the projections 17 may vary somewhat. These dimensional tolerances may be additive in some cases.

It is a common requirement for clutches to be employed in motor cars or other motor road vehicles at the departure from coplanar relation of the inner ends 26 of the fingers shall be no more than 0.025 inches in a direction along the reference axis of the clutch, whereas variations due to the several causes already mentioned may, and often do, produce axial variations from coplanar relation of up to 0.050 inches, these being sufficient to adversely affect proper operation of the clutch.

The method now described avoids the necessity for individual bending of the fingers by hand applied tools, which operation is not onlyextremely time consuming but calls for a high degree of skill to achieve the necessary coplanar relation within the tolerance required.

The stages of the method are illustrated diagrammatically in FIG. 1. i

In stage A the diaphragm spring is illustrated in the unstressed condition with the inner ends of two fingers 26 which are diametrally opposed to each other offset axially of the reference axis 29 to a marked extent which is exaggerated in the interests of'clarity.

In stage B an outer annular zone of the clutch is subjected to elastic straining substantially in accordance with service conditions, i.e. to the extent which is typically illustrated in FIG. 3. The portions of the diaphragm spring containd in this outer annular z'one comprise the outer connecting portion 27 and those parts of the fingers which are bounded laterally by the portions of the circular slot openings which lie radially outwardly of the two wire rings and 21 which constitute the main fulcrum. The forces for establishing the elastically strained condition are illustrated diagrammatically by opposing arrows 20a, 21a simulating the main fulcrum established by the wire rings 20 and 21, and arrows 17a simulating the projections 17 of the pressure plate. In this condition the inner ends 26 of the two fingers are still in axially offset relation.

Whilst in the elastically strained condition, the fingers are subjected each to repeated deflections in a direction t0 and fro along the axis l9, as illustrated in stage C. The angular excursion of each finger is such that the elastic limit of the material is not exceeded. This operation (herein termed exercising and illustrated diagrammatically by the arrows 30) is useful as removing or reducing residual stresses in the inner zone ll of the diaphragm spring and thereby reduces the possibility that the relief of such stresses will occur over an extended period when the diaphragm spring is in service which, if it occurred, might adversely affect the coplanar relation of the inner ends 26 of the fingers achieved by the employment of the present method.

Upon completion of stage C the inner ends of the fingers are released from the means (hereinafter de scribed) which deflects them during the exercising stage, and each finger is then engaged at its underside, as seen in stage D, by a fulcrum element represented by arrows 3]. ln stagesB and C the fulcrum elements 31 are withdrawn clear of the undersides of their respectively associated fingers. Each fulcrum element 31 is moved axially under the influence of yieldable means 32 such as a spring with a force such that the fulcrum element engages'only lightly against the underside of the associated finger and does'not significantly deflect this from the position occupied by the finger with the inner zone ll of the diaphragm spring in an unstressed condition.

Due to the axial offset of the inner ends 26 of the fingers, the fulcrum elements 31 will be axially offset as will be evident from the spacing between the broken lines 310 drawn at right angles to the reference axis through the lower end of each fulcrum element (the fulcrum elements being of equal length).

in the next stage E the fulcrum elements 31 are locked in the axial positions which they occupy in stage D so that they are not displaced downwardly by counterpressure from their associated fingers during performanceof the subsequent operations performed in stage E. Such locking is represented diagrammatically by rectangular blocks 33 anchoring the lower ends of the fulcrum elements. With the fulcrum elements in the locked condition, forces indicated diagrammatically by arrows 34 are applied to the fingers to bend their inner ends downwardly to an extent such that the finger elements all lie in coplanar relation with each other. For this purpose, as hereinafter described, all the fingers are conveniently engaged over their upwardly presented surfaces at their inner ends by a deforming element having a downwardly presented surface lying in a plane at right angles to the reference axis, such deforming element being arrested at a predetermined position in its downward path. Diagrammatically the fingers are shown as resting on a reference surface 35 but 'in practice their position is determined by the stopping position of the deforming element. The extent of the downward movement of each finger is such that the material incorporated in the finger is stressed beyond the elastic limit in the region which the finger is engaged by the associated fulcrum element 31 and accordingly the fingers are permanently or plastically bent so that, upon release or discontinuance of the forces 34, the fingers remain substantially at the position indicated in stage E.

In practice there will be some slight spring back in an upward direction of each finger when so released but this will be substantially equal for each finger and certainly within the tolerance already mentioned of 0.025 inches.

In stage F wherein the forces 34 are discontinued or released from the fingers and the fulcrum elements 31 withdrawn downwardly, the degree of spring-back shown has been somewhat exaggerated for clarity. The inner ends 26 of the fingers are thus set in coplanar relation and thus each finger is engaged and moved to exactly the same extent in a direction along the axis 29 when engaged by a thrust or block or release bearing contacting the inner ends of the fingers at their upper sides.

An embodiment of apparatus for carrying out the method illustrated in FIG. 1 is shown in FIGS. 4, 5 and 6.

This apparatus comprises a body which includes a fixture plate 40 from which extend downwardly a plurality, for example three equally angularly spaced rod structures 41 connected at their lower ends by a fixed bottom plate 42 and at a position between their upper and lower ends by a fixed intermediate plate 43.

Outwardly of the fixture plate 40 there is secured thereto in any suitable manner an annular base plate 44 of a clamping device which includes a plurality of clamping untis 45, typically six in number, at positions spaced apart at equal angular intervals around the refer'ence axis for clamping components of the clutch as seen in FIG. 3 on the fixture plate 40.

Each clamping device comprises a clamping jaw 46 pivoted at 47't0 the base plate 44 and carrying an externally screw-threaded longitudinally adjustable clamping foot 48 for engaging the flange 13 of the cover member 10 and clamping same against an annular seatengages or is just clear of the top of the end wall ll of the cover member 10 for the purpose of stiffening or backing up the end wall to prevent deflection thereof during performance of the operations already described with reference to FIG. 1. The bolts 51 are adjustable axially in screw-threaded openings in the jaws 46 securable in adjusted positions by lock nuts as shown.

The jaws 46 are movable between clamping positions as shown and releasing positions by piston and cylinder units 52 energised by hydraulic fluid under pressure and connected with the jaws through slides 53 guided on the base plate 44 and connected by links 54 to the jaws 46.

In order to facilitate assembly of the components of the clutch on the fixture plate and the clamping of the cover plate thereagainst (bearing in mind that the diaphragm spring will take up its unstressed configuration shown in stage A of FIG. 1 when the pressure plate 14 is freely mounted in the interior of the cover member), a deforming element 55 is provided to enable the diaphragm spring to be strained elastically to its more flattened condition and subsequently to perform the exercising function indicated diagrammatically in stage C by the arrows 30, and thereafter the function illustrated in stage E by the arrows 34.

The deforming element, part of which is seen on an enlarged scale in FIG. 6, comprises a handle 56 below which is a boss 57 having a downwardly presented axially facing shoulder 58 and a hollow spigot or socket formation 59 projecting downwardly from the centre of the boss. The spigot formation 59 is adapted to enable the deforming element 55 to be releasably secured on the upper end of a rod 60 through the intermediary of cooperating formations such as interrupted screwthreads provided respectively internally of the spigot formation 59 and externally on the rod 60. The deforming element 55 is movable axially through the intermediary of the rod 60 by a piston and cylinder unit 61 supplied with hydraulic fluid under pressure (herein called the bending cylinder). The cylinder proper 62 contains a piston 63 having a downwardly projecting sleeve 64 which engages an adjusting nut 65 mounted on an externally threaded portion 66 of the rod 60 and secured in an adjusted position by means of a lock nut 67.

The bending cylinder 61 moves the rod 60 and deforming element 55 to perform the function illustrated diagrammatically by the arrows 34.

The deforming element 55 is reciprocated axially to perform the function indicated diagrammatically by the arrows 30 by a pneumatically energised double-acting piston and cylinder unit 68, herein called the exercising cylinder, secured to the lower plate 42 at its underside and having its piston rod connected to the lower end of the rod 60 by a coupling 69.

To perform the functions illustrated diagrammatically by the arrows 31 a plurality of fulcrum elements in the form of plungers 70 are provided, these being mounted for sliding movement parallel to the reference axis 29 through bores in a mounting block supported in a central aperture in the fixture plate 40. Each plunger terminates at its upper end in a conical portion 73 having a rounded apex and is urged upwardly by yieldable biasing means in the form of a coiled compression spring 74 acting between a collar 75 on the plunger, and a support collar 76 encircling the shank of the screw 77 screwing into a threaded bore in the lower end of the plunger. The support collars 76 are engageable by the upwardly presented shoulders of dogs 78 projecting radially from a sleeve 79. The sleeve 79 is movable by two piston and cylinder units, namely 80, herein called the preload cylinder, and 93, herein called the prepositioning cylinder, which are referred to in more detail in connection with the locking means, hereafter described, for holding plungers in the positions represented in stage D as shown in FIG. 1.

Associated with each plunger 70 is a locking means for holding the plunger against downward movement when a downward reactive force is applied thereto by engagement between the upper conical portion 73 of the plunger and an associated one of the fingers of the diaphragm spring. Such locking means comprises a wedge element having a frusto-conical radially outwardy presented surface 86 and a roller element 87 which is interposed between the surface 86 and a side face 88 of the plunger. The latter is of circular crosssection and is cut away to form a flat presenting the side face 88.

Each roller 87 is urged downwardly into the convergent space between the faces 86 and 88 by biasing means in the form ofa plunger 89, the head 90 of which is engaged by a coiled compression spring 91 acting between the head and a cap member 92 secured to the upper side of the bushing 72 and through which the plungers 70 protrude.

The wedge element 85 is movable between the inoperative lowered position and an operative raised position through the intermediary of the sleeve 79 through the intermediary of the prepositioning cylinder 93 already mentioned and which is slidable on the rod structures 41. This cylinder is energised pneumatically and comprises a cylinder proper 94 and a piston 95 having a sleeve extension 96 which is screw-threaded internally to engage with an external screw-thread on the sleeve 79.

The rollers 87 of the locking means are movable from operative locking positions by upward displacement of a releasing sleeve 97 which is slotted to provide clearance for the radially projecting dogs 78 and is coaxially arranged with respect to the rod 60 and sleeve 79 and slidable relatively to the latter by means of a roller release piston and cylinder unit 98. The latter unit is fixed on the rod structures 41 and comprises a cylinder proper 99 and a piston 100 having an extension sleeve 101 engaging a collar 102 on the sleeve 97. The roller release cylinder 08 is energised pneumatically.

Referring now more particularly to the manner in which the preload cylinder 80 and the prepositioning cylinder 98 operate in conjunction to position the sleeve 79 which controls the position of the wedge element 85, it will be understood that when the plungers 79 are urged upwardly by their associated springs 74 to engage respective fingers, it is firstly necessary that the wedge element be set at an appropriate height to allow the rollers to be effective in locking the plungers 70 against downward movement under downward counterpressure. This function is performed by the preposi tioning cylinder 93. This is energised pneumatically yieldably to urge the piston 95 upwardly and likewise the sleeve extension 96 and rod 79. During this operation the roller release cylinder is energised to raise the sleeve 97 so that the rollers 87 are also raised. When the wedge has been moved into its raised operative position the roller release cylinder is de-energised allowing the sleeve. 97 and rollers to descend so that these are then in their operative positions ready to lock the plungers 70.

In order, however, to preload the rollers and ensure that there will be no small degree of slippage of the plungers 70 in a downward direction when the plungers come under load, the sleeve 79 is moved uwpardly through a controlled distance by the preload cylinder 80. Y

The preload cylinder 80 comprises a cylinder proper 81 and a piston 82 having a sleeve extension 83 which bears against the underside of the cap 84 which has an externally threaded spigot screwing into an internal socket at the lower end of the sleeve 79 and forms a guide element which is slidable on the rod 60. The lower end portion of the sleeve is also screwthreaded externally and carries a collar 84a which, when the prepositioning cylinder 93 is energised, abuts the underside of this cylinder and in effect forms an adjustable stop determining the raised position of the wedge element 85.

When the preload cylinder 80 is pressurised with hydraulic fluid to raise the piston 82 against the action of spring 82a, the cap 84, collar 84a and prepositioning cylinder 93 move upwardly as a whole on the rod structure 41 by an amount determined between the initial clearance between this cylinder and stop nuts 103 on the rod structures 40 and which engage the prepositioning cylinder 93. The stop nuts 103 afford annular chambers containing coiledcompression springs 104 which load the prepositioning cylinder downwardly, and these nuts are secured in adjusted positions by lock nuts 105. Prior to energisation of the preload cylinder 80, the prepositioning cylinder 93 will rest on the upper ends of nuts 106.

The amount of upward movement of the sleeve 79 and hence the wedge element 85 produced by operation of the preload cylinder 80 is of the order of 0.1.

inches producing an upward movement of the associated roller element of 0.05 inches.

When it is desired to release the locking means the wedge element 85 is lowered by lowering of the sleeve 79 to a position below the preset level produced by initial operation of the prepositioning cylinder 93 as a safeguard against additional loading of the roller having taken place during operation of the apparatus which might otherwise cause the locking means to jam rather than release.

The typical apex angle (included) for the frustoconical surface 86 is 14.

The sequence of operations of the apparatus is determined by a control circuit including proximity switches S1 to S6 which are operated in response to the relative approach of targets T1 to T3.

The sequence of operations of the apparatus is as follows. At the start of a cycle of operations the deforming element 55 is removed and the jaws 45 are in open positions so that the fixture plate is unobstructed to receive the clutch components as shown in FIG. 3. These are placed on the fixture plate with location dowels 50 engaging in holes 22 in the flange of the cover member 10.

With the rod 60 in a fully raised position as determined by energisation of the lower cylinder space of the bending cylinder 61, the deforming element is installed and engaged in a retentive manner with the upper end of the rod 60.

. The bending cylinder 61 is then energised to produce downward movement of the piston 63 to bend the fingers downwardly to the positions illustrated in stage B of FIG. 1. This allows both the pressure plate 14 and the cover member to be seated on the upwardly presented surface of the seating plate 49 and secured in this position by closure of the jaws 46 by energisation of cylindres 52. In this position the pins 51 may be just clear of the upper wall 11 of the cover member or lightly engaging same. The rod 60 and deforming element 55 are then returned to the raised position by appropriate energisation of the bending cylinder 61. The force exerted by the diaphragm spring in its then elastically strained condition is exerted between the pressure plate 14 and the cover member 10 in the same manner as will be the case when the clutch ultimately produced is in service. The components of the main fulcrum structure 16 are omitted from FIG. 5 for clarity but would be present.

The rod 60, carrying the deforming element 55 with it, is then reciprocated vertically by operation of the exercising cylinder 68, the shoulder 58 of the deforming element being in contact with the inner ends of the fingers to cause these to move to and fro in a vertical direction as represented in the exercisingstage C of FIG. 1.

During this operation the piston of the prepositioning cylinder 93 is in its lowered position, as is thus also the sleeve 79 and the wedge element 85, so that the locking means associated with the plunger is out of operation. On completion of the exercising operation each of the plungers 70 has its upper conical end portion 73 in contact with an associated one of the fingers, typically 18 in number, under light pressure exerted by the spring 78. It is to be noted also that during the exercising stage the piston 82 of the preload cylinder will be in its lowered position under the influence of its spring 82a.

On completion of exercising the wedge element 85 is raised to its prepositioning level by energisation of the prepositioning cylinder 93 to move the piston 95 upwardly under pneumatic pressure to an extent determined by engagement of the collar 84a with the underside of the prepositioning cylinder. In this position the wedge element 85 is below its final locking position. Also during this stage the roller release sleeve 97 is maintained raised by appropriate energisation of the roller release cylinder 98 to raise the piston 99 so that the rollers 87 are free with a downwardly convergent spaces between surfaces 86 and 88.

The roller release cylinder 98 is then energised to lower the piston 100 and hence the sleeve 97 so that the rollers are maintained under pressure of spring 91 in contact with the surfaces 86 and 88. The sleeve 79 is then further raised by the predetermined amount already mentioned by energisation of the preload cylinder 80 to raise the piston thereof. As mentioned, the extent of the upward movement is determined by abutment between the upper side of the prepositioning cyl inder 93 and the lower ends of the stop nuts 195.

The plungers 70 are now securely locked each at a level determined by the position of its associated finger. The bending cylinder 61 is then energised to move the piston 63 downwardly to an extent determined by the positions of the collar 64 and associated sleeve 64a,

the lower end of the latter contacting the lower wall of guide socket 64b. Both 64! and 64a are adjustable on the rod 60 through the intermediary of the external screw-thread thereon and the internal screw-thread on the

parts

64, 64a.

In consequence of this movement the portions of the fingers situated radially inwardly of the plungers 70 are bent to an extent which causes the elastic limit of the material of the diaphragm spring to be exceeded in the region in which the plungers 70 engage the fingers, this region being of lower hardness than the inner ends of the fingers.

Completion of downward movement of the rod 60 corresponds to the condition illustrated in stage E of FIG. 1 wherein the inner ends of the fingers are brought into coplanar relation.

Upward movement of the rod 60 and opening of the jaws 46 of the clamping units allows the clutch components to be removed. The degree of spring back of each finger, if it occurs, will be substantially identical for each finger, and consequently these are still maintained in coplanar relation.

We claim:

1. A method of setting into coplanar relation in a plane at right angles to a reference axis of a diaphragm spring the inner ends of radially inwardly projecting fingers of said spring integrally connected at their outer ends with an outer annular portion of said spring, said method comprising the steps of:

a. elastically straining said spring in an outer zone thereof in a mode corresponding to that in which it is elastically strained under service conditions,

b. subjecting said fingers while said spring is so strained to bending in a direction along said reference axis beyond the elastic limit of the spring material to bring inner ends of said fingers into coplanar relation in said plane.

2. A method according to claim 1 wherein in its unstressed condition said outer annular portion of said spring is of generally domed or frusto-conical form and said step of elastically straining said spring in said outer zone elastically deforms said outer annular portion towards a more flattened form.

3. A method according to claim 1 wherein:

a. said outer zone in which said elastic straining is effected includes said outer annular portion of said spring and also an outer portion of each finger,

b. said fingers are bent by supporting each finger by a fulcrum element at a position intermediate the inner and outer ends of said finger and exerting a bending force on that portion of said finger lying radially inwardly of said fulcrum element.

4. A method according to claim 1 wherein preparatory to bending said fingers beyond the elastic limit of said material, said fingers are bent within their elastic limits to and fro along the direction of said reference axis.

5. A method according to claim 1 wherein the step of elastically straining said spring in its outer zone is effected through the intermediary of at least part of a structure of a clutch in which said diaphragm spring is to be incorporated.

6. A method according to claim 5 wherein said elastic straining is effected by opposing forces exerted in a generally axial direction on said spring at a fulcrum provided on or by a cover member of said clutch at a position inset radially from the periphery of said spring and by a pressure plate of said clutch at a position spaced radially outwardly of said fulcrum.

7. Apparatus for use in the manufacture of diaphragm springs each having fingers projecting radially inwardly'towards the reference axis of said spring, said fingers being integrally connected at their outer ends to an outer annular portion of said spring, said apparatus comprising:

a. a body,

b. support means thereon for supporting said spring;

c. means for elastically straining an outer zone of said spring in a mode corresponding to that in which it is strained when in service,

d. finger bending means for bending said fingers in a direction lengthwise of said reference axis beyond the elastic limits of the spring material to a position in which the inner ends of said springs are in coplanar relation with each other in a plane at right angles to said reference axis.

8. Apparatus according to claim 7 wherein said finger bending means comprises:

a. a fulcrum element for each finger, each such fulcrum element being movably mounted on said body to engage its respective finger,

b. a deforming element for applying axially directed force to each finger in opposition to support provided therefor by each fulcrum element.

9. Apparatus according to claim 8 wherein said finger bending means further includes:

a. biasing means for urging each fulcrum element into contact with its associated finger element with a force less than that producing substantial bending of said finger element,

b. locking means for holding said fulcrum element against displacement from the position which it occupies after contacting its associated finger element under counterthrust therefrom during operation of said deforming element.

10. Apparatus according to claim 9 further comprising preloading means for setting said locking means in an operative position securely to hold each fulcrum element agianst movement from said position prior to operation of said deforming element.

11. Apparatus according to claim 9 wherein said locking means comprises a wedge element and a roller element operating in combination with an associated fulcrum element to cause said fulcrum element, which is movable axially in one direction towards an associated finger, to become clamped upon a tendency to move axially in the opposite direction under counterthrust from said finger.

12. Apparatus according to claim 11 further comprising preloading means operatively connected to one of said elements of said locking means to move same in a direction to preclamp the associated fulcrum element prior to application thereto of counterthrust from the associated finger element during operation of said deforming element.

13. Apparatus according to claim 7 for use in the manufacture of a diaphragm spring for a clutch which comprises a cover member including main fulcrum means for said diaphragm spring to engage same at a position inset radially from its periphery, and a pressure plate for engaging said diaphragm spring radially outwardly of said main fulcrum means, and wherein said means for elastically straining said outer zone of said diaphragm spring comprises:

a. means for supporting said pressure plate on said body of said apparatus,

under stresses transmitted thereto by said main fulcrum means and said clamping means when said diaphragm spring is strained elastically and said fingers bent beyond the elastic limit of said spring material by said finger bending means.

15. Apparatus according to claim 7 further including exercising means for moving said fingers elastically to and fro lengthwise of said reference axis.

' UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 9,251 Dated August 7, 1973 Inventor) I Algernon Walter Pugh, ,et a1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

(9n the Abstract Page, under the heading "Foreign Application Priority Data" v change "May 21, 1971 to --June 25, 1971--.

Signed and sealed this 6th day of August 1971,.

(SEAL) Attest: MCCOY M. GIBSON, JR; 0. MARSHALL DANN Attesting Officer Commissioner of Patents

Claims

1. A method of setting into coplanar relation in a plane at right angles to a reference axis of a diaphragm spring the inner ends of radially inwardly projecting fingers of said spring integrally connected at their outer ends with an outer annular portion of said spring, said method comprising the steps of: a. elastically straining said spring in an outer zone thereof in a mode corresponding to that in which it is elastically strained under service conditions, b. subjecting said fingers while said spring is so strained to bending in a direction along said reference axis beyond the elastic limit of the spring material to bring inner ends of said fingers into coplanar relation in said plane.

3. A method according to claim 1 wherein: a. said outer zone in which said elastic straining is effected includes said outer annular portion of said spring and also an outer portion of each finger, b. said fingers are bent by supporting each finger by a fulcrum element at a position intermediate the inner and outer ends of said finger and exerting a bending force on that portion of said finger lying radially inwardly of said fulcrum element.

7. Apparatus for use in the manufacture of diaphragm springs each having fingers projecting radially inwardly towards the reference axis of said spring, said fingers being integrally connected at their outer ends to an outer annular portion of said spring, said apparatus comprising: a. a body, b. support means thereon for supporting said spring; c. means for elastically straining an outer zone of said spring in a mode corresponding to that in which it is strained when in service, d. finger bending means for bending said fingers in a direction lengthwise of said reference axis beyond the elastic limits of the spring material to a position in which the inner ends of said springs are in coplanar relation with each other in a plane at right angles to said rEference axis.

8. Apparatus according to claim 7 wherein said finger bending means comprises: a. a fulcrum element for each finger, each such fulcrum element being movably mounted on said body to engage its respective finger, b. a deforming element for applying axially directed force to each finger in opposition to support provided therefor by each fulcrum element.

9. Apparatus according to claim 8 wherein said finger bending means further includes: a. biasing means for urging each fulcrum element into contact with its associated finger element with a force less than that producing substantial bending of said finger element, b. locking means for holding said fulcrum element against displacement from the position which it occupies after contacting its associated finger element under counterthrust therefrom during operation of said deforming element.

13. Apparatus according to claim 7 for use in the manufacture of a diaphragm spring for a clutch which comprises a cover member including main fulcrum means for said diaphragm spring to engage same at a position inset radially from its periphery, and a pressure plate for engaging said diaphragm spring radially outwardly of said main fulcrum means, and wherein said means for elastically straining said outer zone of said diaphragm spring comprises: a. means for supporting said pressure plate on said body of said apparatus, b. clamping means cooperative with said cover member for holding same in an axial position relative to said pressure plate such that said diaphragm spring is elastically strained between said main fulcrum means and said pressure plate.

14. Apparatus according to claim 13 wherein said clamping means includes back-up means for engaging an end wall of said cover member at distributed positions in a circumferentially extending zone of said end wall to avoid wave-like distortion of said cover member under stresses transmitted thereto by said main fulcrum means and said clamping means when said diaphragm spring is strained elastically and said fingers bent beyond the elastic limit of said spring material by said finger bending means.