US2169787A

US2169787A - Spring device

Info

Publication number: US2169787A
Application number: US210286A
Authority: US
Inventors: Sylvan J Becker
Original assignee: Associated Spring Corp
Current assignee: Associated Spring Corp
Priority date: 1938-05-26
Filing date: 1938-05-26
Publication date: 1939-08-15
Anticipated expiration: 1956-08-15

Description

@8.15, 1939 J. BECKER 2,169,181

' SPRING' DEVICE Filed Mayl26, 1958 v Patented Aug. 15., 1939 UNITED STATES PATENT omer;

SPRING nevica Application May 2s, 1938, serial No. 210,286`

s o1aims. (ci. 267-1) This invention relates generally to springs and,v

more particularly, is intended to provide an proved Belleville spring construction.

It has heretofore been known to provide coned 5 Belleville springs and to attachl to or form integrally with the inner periphery of the spring elongated fingers which converge toward the geometrical center of the spring and which are employed to operate the spring from its coned, or inoperative, position to its flat or working position. These elongated fingers have, in prior constructions, been separated by elongated apertures terminating adjacent the inner periphery of they spring in openings -of substantially circular shape. It has been found that such spring devices are generally lacking in usefulness be- .cause of their tendency to fracture along a line extending radially of the spring and lying between theouter periphery thereof and the nearest adjacent point of the circular openings relferred to.

It'is the principal object of this invention to provide a Belleville spring structure which will be generally similar to that hereinbefore describedbut which will be so constructed that the aforesaid tendency of these springs to fracture will be -greatly diminished or entirely removed. lOther objects and features of novelty of the invention will be apparent from the following description and the annexed drawing, it being clearly understood that such ldescription and drawing are only illustrative of my invention, and that the same is not limited thereby," or otherwise than by4 the appended claims.

Referring to the drawing, inY which similar reference numerals refer to like parts,

Fig. 1 is a plan View, partially broken away, of a spring formed according to this invention;

Fig. 2 is a partial, sectional view taken on the v Fig. 6l is a partial view showing the prior art construction andr thedisposition of stresses therein, and

Fig. 'l is a partial view, similar to Fi/g. 6, and showing the disposition ofstresses in a construction according to this invention.

In Fig. 1 of the drawing there is'illustrated a Belleville spring comprising the annular spring element I having the preferably circular outer periphery 2 and an inner periphery which may be indicated by the dotted line 3. Formed integrally with the spring and extending radiallythereof toward the geometrical center of the spring are operating fingers d which are separated by elongated, radial slots or apertures 5. This entire spring device is coned as illustrated in Fig. 2 and it will be seen that pressure apl0. plied to the inner ends of the operating fingers 4 in the direction of the plane of the outer pev rlphery 2 of the spring will cause the -spring to be flexed toward a flattened condition which may be reached if suicient pressure is applied l5 to theoperating fingers.

In prior spring devices formed in the manner described, it has been the practice to terminate the elongated apertures 5in circular openings, the outermost edges of which were tangential to 20 the inner periphery 3 of the spring. Such prior spring devices have been found to be unsatisfactory in practice because of the fact that they were found to fracture, after only limited use, along a line extending radially'of the spring and 25` -lying between the outer periphery 2 thereof and the nearest adjacent point of the circular apertures to which reference has been made. Until the present invention n0 means has been known for remedying this defect, and spring devices of 30 this type have therefore not been widely used, although many advantages are inherent in such devices. 1

According to the present invention I propose to terminate the elongated apertures 5, adja- 35 cent the inner periphery 3 of the. spring, in openings or apertures 6, as taught by the prior art. My invention, however, contemplates the extension of the bases of these apertures toward each other on the line of the inner periphery of the 40 spring. `Thus, instead ofv providing circular apertures at the ends of the slots 5, I provideapertures which are broadlyfextended along the Ainner peripheral line 3 of the spring. These apertures may be shaped as disclosed in Figs. 1, 3 45 and 4 or maybe shaped in any suitable manner which will extend the bases of .the apertures in the line 2.

The broadening of the bases ofthe openings 6 in the manner taught by my invention will 50 have the effect of increasing the resistance of the spring to fracturing in the manner described.

This effect may be better understood by reference.

to Figs. 6 and 7 ofthe drawing. In Fig. 6 there is illustrated, in full lines, a portionv of a spring 55 I having circular openings 6 therein in accordance with prior art practice. Fractures in such prior lines B-B indicated in this figure, i. e. the radial lines joining the outer periphery of the spring and the nearest adjacent point of the opening 6. Obviously, because of the circular shape ofthe opening 6, the line B-B is much shorter thanA any other radial dimension of material through which force exerted on the spring is transmitted and the stress along line B-B is accordingly greater than at any other portion of the spring device. It will also be seen that along the radial lines A-A which extend through the centers of the operating ngers 4 the strength of the spring will be greatest. In studying the action of springs formed in the manner illustrated in Fig. 6 I have found that as the spring is deformed from coned position to o'r through flat position, the portion of the spring along line B-B will deform to a greater extent than the portion along line A-A, indicating that the portion along line BMB is being worked more than other parts of the spring. This effect is indicated by the shape which the inner periphery of the spring assumes as thc spring is deformed. Instead of remaining in a single plane as the spring is deformed the inner periphery of the spring assumes an undulating' shape, the portions thereof adjacent the section B-B showing greater deformation than other sections. I have determined that the spring is worked unevenly in this manner and that the greatest working occurs at the section of least strength, i. e. along line B-B.

Il, now, in the manner taught by the lpresent invention the bases of the openings 6 are broad cned or extended along the inner .periphery of the spring, as illustrated in Fig. '7, the line's or sections of minimum strength of the spring will e be broadened to an extent determined by the width of the bases of the openings 6. Instead of a lineor section B-B of minimum strength there is now an area, shown as a shaded area in Fig. 7. where maximum stress occurs. It will be seen that the greatest stress will occur over an i area, .which is defined by the ends of the elongated side of the opening 6, instead of along a line or section and that the distribution of stresses over the spring will be more uniform. I have found that by reason of the described change in construction springs formed according to this invention have over 100% higher endurance limit than those formed in the manner taught by the prior art. This I have found to be due entirely to the equalization of the stresses over the entire spring.

The openings 6 may, in accordance with the invention, be shaped in any suitable manner in accordance with the principles heretofore stated. For example, they may be formed in the shape illustrated in Figs 1 and 3 or, alternatively, in the shape illustrated in Fig. 4. In Fig. 3 there is illustrated in dot and dash lines a basic circle with center a. The aperture shaped according tothe invention is illustrated in full lines at 6. This opening may be described as being formed by four arcs b, c, d and e, having centers b', c', d. and e',4 respectively, which are symmetrically disposed with respect to center a, as V the outer periphery thereof and the nearest adjacent point of the aperture is minimized by reasonof the fact that the stresses operate through the linear portion f instead of being concentrated along a single section vas is the case when the circular aperture is employed.

In the form of aperture illustrated in Fig. 4, the slot 5 opens directly into the arcuate portions 7 and k of the aperture 6. In this form there are two linear portions l and m, curved portions n and o and a rectilinear portion p which corresponds to, but is of much greater length than, the line f of Fig. 3. In both forms there is provided an aperture bounded by a` rectilinear wall in that portion of the aperture nearest the periphery of the spring. This rectilinear portion is arranged transversely of the radius extending through the slot 5 and preferably at right angles thereto.

In Fig. 5 ofthe drawing there is illustrated one possible application of my invention, this being the use of the spring in a clutch assembly such as is used in automotive vehicles. In this assembly there is illustrated a flywheel 20 which is associated with the engine shaft, not shown, and a -transmission shaft 2l which carries a hub 22 to which is secured a driven plate 23 having friction facings 24 on the opposite faces thereof. One of these facings engages the flywheel, while the other engages a pressure plate 25 which rotates with the flywheel and its cover 26, but is slidable axially relative thereto. Included in this assernbly is a spring 21 which is 'formed in the manner taught by this invention and which is so mounted that the .outer periphery thereof engages the pressureplate 25, while the 'inner or centrally located ends of the operating fingers are engaged by a throwout collar 1 3 which urges the operating fingers toward the pressure plate, thereby urging the spring toward a flat condition. The spring is mounted in the position described by a series of fulcrum pins 29 which are carried by the flywheel cover plate 26 and which extend through the annular series of apertures 6 in the spring, Each of these pins carries rings 30 and 3l which are disposed, respectively, on opposite faces of the spring 2l.

In assembling the clutch described, the height of the cone of the Belleville spring is reduced, the pressure of the flattened cone being transmitted from the outer periphery thereof to the pressure plate and the reaction being taken by the Aengagement .of the spring plate with the ring 30. In releasing the clutch the reaction is taken from ring 30 by the throwout mechanism. The spring plate then fulcrums on ring 3| and becomes further flattened, thereby relieving pressure on the pressure plate and causing release of the clutch.

It will be apparent that in the normal use of auch a clutch assembly, as in an automobile vehicle, the spring plate will be operated from its flattened position to its coned position a great number of times and that, in this repeated process, stresses in the spring will tend to develop fractures in the manner hereinbefore described.

As stated, the application of the principles of this invention has resulted in the increase of more than 100% in the life of the clutch spring.

While I have illustrated and described certain embodiments of my invention, additional embodiments or improvements may occur` to those skilled in the art, all of which may be practised without departing in any Way from the spirit or scope of plate having a circular series of radial slots the invention, for the limits of which reference must be had to the appended claims.

What I claim is: 41. A spring device comprising 4a coned spring plate having a circularseries of radial slots therein, each terminating at its outermost end in an enlarged aperture, the boundary wall of each of such apertures including at least one rectilinear portion, said' rectilinear portion being at the radially outermost part of'said aperture.

2. A spring device comprising a coned spring therein, each terminating at its outer end in an enlarged aperture, the boundary wall of each aperture including arcuate portions and at least one rectilinear portion, said rectilinear portion being at the radially outermost part of the aperture and extending transversely of the radial axis of the coned spring plate which extends through the center of the aperture.

3. A spring device comprising anconed spring plate having a plurality of radial slots therein terminating respectively at their outer ends in enlarged apertures which are arranged in a circular series, the boundary wall of each aperture including arcuate portions and at least one rectilinear portion, each of said rectilinear portions being at the radially outermost part of the ap erture and extending at right angles to the radial axis .of the coned spring plate which extends through the center of the aperture.

4. A spring device comprising an annular spring plate, a plurality of operating fingers extending radially inwardly i'rom the inner periphery of said plate, the plate and the operating lingers being of frusto-conicalshape, adjacent iingers being separated by elongated slots extending radially of the operating ilngers and by apertures formed in the plate adjacent the inner periphery of the plate, each of said aperturesv being formed with abroad base which is disposed.

approximately in the said inner periphery. o1' the plate.

5. A spring device comprising an annular spring plate, a plurality of operating fingers extending radially inwardly from the inner periphery of said plate, the plate and the operating ngersbeing of frusto-conical shape, adjacent iingers being sep` arated by elongated slots extending radially of the operating lingers and by apertures `formed in the plate adjacent the inner. periphery of the plate, each of said apertures being formed with a broad rectilinear base which is disposed apy proximately in the inner periphery of the plate and which extends at approximately right angles to the radial axis of the plate which extends through the center of the aperture.

6. In a clutch, a flywheel, a cover therefor,

l'frictionally engaging members, a coned'spring having slots extendingfrom said apertures to' ward the. center of said spring plate, each of said apertures having its radially outermost wall portion rectilinear in outline, said rectilinear wall portion extending transversely of a radius of the plate extending through the adjacent slot.A

7. In a clutch, a flywheel, a cover therefor. frictionally engaging members, a coned spring to effect frictional engagement, said spring having a plurality of apertures arranged in a circular series, fulcrum pins carried by said cover and extending through said apertures, said plate having slots extending from said apertures to ward the center of said spring plate,A the radially outermost wall portion of each of said apertures being rectilinear in outline, said rectilinear wall said plate through the adjacent slot.

` 8.` A spring device comprising an annulan spring plate, a plurality of operating lingers extending-radially inwardly from the inner periphery of said plate, the plate and the operating iingers being of frusto-conical shape, adjacent ngers being separated by elongated slots extending radially of the plate and which are enlarged adjacent the inner.A periphery of the plate to provide apertures, each of said apertures being' formed with a broadened base which is disposed approximately in the line of the inner periphery of the plate and which extends transversely for a substantial distance on either side of the radialjaxisof Ithe plate which extends through the elongated slotV connecting with the aperture which is bounded by the said base.

` SYLVAN J. BECKER.