US3482832A - Vacuum spring construction - Google Patents

Description

Dec. 9, 1969 B. J. FINN ET AL VACUUM SPRING CONSTRUCTION Filed March 12. 1968 3 Y mm m m N M .m E I 4 m" f A a] d. a 5

BY H/an United States Patent 3,482,832 VACUUM SPRING CONSTRUCTION Bernard J. Finn, Huntington Woods, and Alan I. Manmngs, Southfield, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Mar. 12, 1968, Ser. No. 712,441 Int. Cl. B60g 11/56 U.S. Cl. 269-34 8 Claims ABSTRACT OF THE DISCLOSURE This invention relates to springs and more particularly to spring constructions especially adapted for vacuum energization.

The present invention is concerned primarily with improvements in vacuum springs of the type shown in US. Patent No. 3,106,387, Francis, entitled Vacuum Spring Construction, assigned to General Motors Corporation. In the indicated patent, there is disclosed a vacuum spring of the piston, cylinder and diaphragm type wherein the side wall depth of the piston is significantly less than the extended length of the diaphragm. In order to prevent radial inward collapse of a portion of the diaphragm when the piston is in an extended position, a helical spring of approximately the same diameter as the inner diameter of the piston is disposed bteween the opposed end walls of the piston and cylinder under light compression so that as the piston moves to the extended position, successive individual coils of the spring arrest radial inward deflection of the otherwise unsupported portion of the diaphragm. While this arrangement is, within limits, effective for the intended purpose, as the degree of the extension of the piston increases, the vertical gap between each coil of the spring necessarily increases with the result that localized support of the diaphragm progressively diminishes.

An object of the present invention is to provide a vacuum spring of the piston, cylinder and diaphragm type in which radial support of the diaphragm throughout the total range of movement piston is complete and uniform.

A further object is to provide an arrangement of the stated character in which the piston element is provided with a normally nested telescoping sleeve having resilient means associated therewith operative to yieldably displace the sleeve to a predetermined extended position relative to said piston.

Another object is to provide a contsruction of the stated character in which the sleeve and resilient means associated therewith form an integral homogeneous unit.

The foregoing and other objects, advantages and features of the invention will become more readily apparent as reference is had to the accompanying specification and drawings wherein:

FIGURE 1 is a sectional elevational view, illustrating the relationship of parts in a collapsed position;

FIGURE 2 is a fragmentary view similar to FIGURE 1, illustrating the relationship of parts in extended position; and

3,482,832 Patented Dec. 9, 1969 FIGURE 3 is a view looking in the direction of arrows 3-3 of FIGURE 1.

Referring now to the drawings, there is shown a vehicle spring construction in which a conventional coil spring 2 is arranged in compression between a sprung portion 4 and an unsprung portion 6, with a vacuum spring unit 8 disposed in parallel relation to the coil spring 2 and arranged so that energization thereof (introduction of subatmospheric pressure) acts in opposition to the coil spring. It will be understood, however, that the arrangement shown is for illustrative purposes only and that the spring unit 8 may equally well be arranged in opposite relation, i.e., to augment the elastic support provided by spring 2, or may be utilized independently.

Spring unit 8 includes an inverted cup-shaped cylinder 10 having a flange 12 secured at its lower open end to sprung portion 4 by bolts 14. Reciprocably disposed in cylinder 10 is a shallow cup-shaped piston 16 having an annular side wall 18, the diameter of which is substantially less than the internal diameter of the side wall 20 of the cylinder. A relatively thin walled flexible diaphragm 22 overlies the bottom wall 24 of piston 16, spans the annular gap 26 between the piston and cylinder side walls, and has its outer perimeter secured between cylinder flange 12 and the adjacent sprung portion 4. The cavity 28 between the piston and cylinder is subjected to subatmospheric pressure from a convenient source, not shown, via passage 30. When so energized, as the vacuum level in the cavity 28 increases, atmospheric pressure acting on the bottom wall of the piston 16 exerts an upward force on a rod 32 connected at its upper end to piston 16 by clevis structure 34. Since the lower end 36 of rod 32 is pivotally connected at 38 to the unsprung portion 6, the sprung and unsprung portions 4 and 6 are caused to move toward each other until the force of spring 2 balances the opposing force of spring unit 8.

Since utilization of a vacuum spring, either alone or in conjunction with other springs, frequently involves application requiring piston excursion significantly greater than the side wall depth thereof, according to the principal feature of the invention, means are provided to assure radial support of that portion of the diaphragm not in contact with either the cylinder wall or the piston wall. To this end, a relatively thin walled sleeve member 40 is disposed within piston 16. Sleeve member 40 is dimensioned to provide free telescoping movement relative to the piston side wall and includes integral spring portions 42 in the form of preformed accordion pleats 44 terminating in attachment legs 46 secured to the bottom wall of piston 16 by clips 48. As seen in the drawing, when the piston 16 is in a totally collapsed position within cylinder 10, the upper flanged end 50 of the sleeve abuts the cylinder top wall and displaces the sleeve to a fully nested position within the piston against the resilient force of spring portions 42. As the piston moves downwardly, spring portions 42 progressively telescopingly displace sleeve 40 to a position axially juxtaposed with the upper end of the piston and thereby form a secondary piston side wall capable of providing radial support for the diaphragm.

To prevent excessive axial displacement of the sleeve 40, the accordion pleated spring portions 42 thereof are preformed so that their relaxed state is just sufficient to totally displace the sleeve from the piston. With continued downward movement of the piston and sleeve, the diaphragm 22 progressively peels off the cylinder wall unto not only the entire vertical wall of the piston wall but also the entire vertical wall of the sleeve. Thus, in spite of the fact that the piston is relatively shallow, vertical excursion thereof is accommodated without ultimate loss of radial support of the diaphragm.

According to another feature of the invention, the sleeve 40 is preferably formed of polypropylene or other polymer material which not only exhibits corrosion free characteristics but also displays flexible hinge properties enabling formation of both the sleeve portion and the resilient portion in a homogeneous structure. It will, of course, be apparent that the portion of sleeve 40 engaged by diaphragm 22 is subjected to uniform radial pressure around its entire circumference, and therefore relies on hoop compression properties rather than heavy physical structure thereby enabling utilization of relatively light thin wall material.

While but one embodiment of the invention has been shown and described, it will be apparent that other changes and modifications may be made therein.

We claim:

1. In a vacuum energized spring, a cup-shaped piston connected to an opposed cup-shaped cylinder by a rolling lobe diaphragm, said piston having a side wall depth less than the extended length of said diaphragm, a sleeve telescopeably movable from a nesting position within said piston to an axially juxtaposed extended position, and resilient means urging said sleeve out of said nested position, whereby upon movement of said piston to an extended position relative to the end wall of said cylinder said sleeve moves out of said nested position to establish a secondary side wall axially adjacent said piston side wall preventing radial inward collapse of said diaphragm.

2. The invention of claim 1 including means for limiting the extended position of said sleeve.

3. The invention of claim 1 wherein said piston and said resilient means form an integral unit.

4. The invention of claim 3 wherein said unit is formed of thin wall plastic material with the resilient means portion thereof preformed to yieldably collapse in accordion fashion,

5. The invention of claim 4 wherein said resilient means in its extended relaxed form occupies substantially the same vertical space as the side Wall depth of said piston.

6. The invention of claim 5 including means for anchoring the end of said resilient means on the base of said piston.

7. The invention of claim 6 wherein said resilient means portion comprises circumferentially spaced segments including accordion pleated vertical portions and horizontal attachment portions.

8. The invention of claim 7 including a circumferential lip on the end of said sleeve opposite said resilient portion extending radially beyond the side wall of said piston.

References Cited UNITED STATES PATENTS 3,003,758 10/1961 Francis 26734 3,106,387 10/1963 Francis 26734 JAMES B. MARBERT, Primary Examiner

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