Articles known as pneumatic or gas springs, which for convenience can be referred to as counterbalance links have become common in commercial articles, particularly in the automotive industry, but they are being used in many other fields whereverthe need is present to provide a counterbalance force for closure units, such as lids, doors and cabinet fronts, and gas spring replacement for mechanical spring fittings has become prevalent. In some fields of use, particularly in the automotive fieldwhere pneumatic springs are used on each side of trunk lids and hatch backs, the springs counterbalance the weight of the lid or hatch back. The gas springs are retracted, i.e., the spring piston rod is moved into the spring cylinder, when the lids areclosed. Then the gas spring units can extend, under gas pressure force acting on the effective piston shaft cross-section area, to move the lid to an open position. As is true of many gas springs, a control orifice by-pass in the gas spring,effectively slows the opening speed of the lid.
In the automotive field, particularly where pneumatic springs are used on hoods, trunk lids and hatch backs, two springs are used, primarily to provide balanced spaced apart forces to counterbalance the weight of the closure and prevent twistingor warping of the closure unit relative to its hinge axis. This invention while developed relative to automotive uses is not restricted to such field. It results in a compact installation using a single pneumatic spring connected through bell cranksand idler links to a hinged closure member. The elongate spring is mounted on and between bellcranks with the spring floating, between positions, in a direction transverse to the hinge axis of the closure. In conjunction with the counterbalanceapparatus the pneumatic spring construction has been improved to provide a desired multi-output force feature as well as incorporating a unique method and structure to effectively decrease loss of operative gas pressure within the pneumatic springresulting primarily from leakage of the gas directly through the shaft seal due to permeability of the material from which the seal is made. The latter aspect can be referred to as permeability compensation or pressure decay compensation.
Examples of transverse springs with bellcrank linkage are seen in the following U.S. Patents: U.S. Pat. No. 3,724,797 to H Freitaz et al for Resilient Seat; U.S. Pat. No. 4,416,094 to F. Bugener et al for Attic Window Assembly; and U.S. Pat. No. Re. 26,162 to A. K. Simons et al for Vehicle Seat Rebound Control. An example of a different dual output force concept in a pneumatic spring can be seen in applicant's U.S. Pat. No. 4,451,964 (also U.S. Pat. No. 4,451,978) where afloating piston is utilized to provide the dual output force. While not teaching the pressure decay compensation invention of this application, U.S. Pat. No. 4,408,751 to Daniel P. Dodson and George C. Ludwig for Multi-chamber Temperature CompensatedPneumatic Counterbalance shows a fixed partition or wall module providing a separate gas chamber in a pneumatic counterbalance cylinder.
A transversely mounted single pneumatic spring, bell crank and idler link assembly or apparatus will provide a compact installation for hinged closures such as automobile trunk lids or doors and other similar closures. The spring will float,being attached only to spaced-apart bellcranks. In an automobile trunk installation, where the trunk lid is mounted by hinges or "goosenecks" between each side of the lid and automobile frame, the forward space required for this counterbalance assemblyis minimized being installed laterally just behind the rear seat and in the forward upper portion of the trunk. Only one spring unit is required, thus minimizing cost. The spring unit is effectively hidden or concealed at the front upper part of thetrunk minimizing damage by items placed in the trunk. Other pneumatic spring enhancements, such as the multi-output force feature of the present invention and the pressure decay compensation feature of the present invention can be incorporated in thespring unit to provide convenient operation of opening the lid and to improve the life expectancy of the pneumatic spring by minimizing and effectively negating pressure loss due to leakage of gas past the shaft seal. If desired, other features such astemperature compensation as taught in U.S. Pat. No. 4,408,751 can be easily added to the pneumatic spring inasmuch as the spring cylinder length can be made substantially longer than the piston shaft, the stroke of which is relatively short. Excesscylinder length provides the space or volume zones used for the various, above mentioned, enhancement features.
The present invention has for a primary object the provision of a compact counterbalance apparatus for use with closure units where a single elongate pneumatic spring having shaft and cylinder end connector links are connected to arms of twospaced apart bellcranks, the other arms of which connect with idler links to a closure unit, secured for hinged movement to the frame structure of the closure, e.g., an autombile trunk lid with associated vehicle frame structure, the spring beingsupported laterally on the bellcranks so it floats in a plane parallel with the hinge axis of the closure lid.
Additional novel objects reside in the provision of improvements in the pneumatic springs which can be used with the aforementioned transverse spring and bell-crank apparatus to (1) provide a dual or multiple output force for the spring shaftseal to vary the volume and, of prime importance, changing the effective cross-section area of the piston shaft of the spring cylinder near the end of the compression stroke, and (2) to provide a special extra volume chamber in the spring cylinder with asealed partition wall between the extra chamber and the operative volume part of the spring cylinder and having an auxiliary supply of gas under higher pressure than that of the spring operative gas pressures and with the spring shaft seal and thepartition wall seal made from specific material so that gas permeability characteristics of both seals are as desired to compensate for various conditions which cause leakage from the cylinder. As desired, the gas spring used in the counterbalanceapparatus can be used with or without any or all of the above noted enhancements to this spring operation.
In conjunction with the foregoing improvement in the dual or multiple force output provisions of the pneumatic spring unit, further objects reside in providing such a spring for substantially vertical disposition filled with a predeterminedquantity of oil or the like to enable operation as a liquid pneumatic shock absorber with plural output forces enabled by controlled movement of the shaft to cylinder sealing assembly near the retraction limit position of the shaft. Another object inconnection herewith resides in the incorporation of a supplemental disc valve unit which is located near the closed end of the spring cylinder and is provided with an orifice bleed to enable controlled movement, at least in the rebound direction ofmovement of the counterbalance unit when the shaft is retracted to the higher output force position. The disc valve can be fixed with a small axial floating movement to shift from an effective sealed relationship of its periphery with the cylinder wallto a free flow relationship so that orifice controlled flow is only in the direction of shaft extension under the high output force. The disc can be fixed in the cylinder wall to provide orifice controlled flow in both directions if so desired.
Using the spring link construction previously described, a multiple load path for the multiple output capability of the spring link can be accomplished by providing independent mechanical linkage connecting or abutting the bushing abutment, apartfrom the shaft abutment parts which are used in FIGS. 8 and 17. It is further noted that the multiple part telescoped bushing embodiment offers numerous capabilities, e.g., a universal construction can be mass-produced for economic efficiency and thenduring specific uses, all bushing parts can be pushed in simultaneously, providing a dual stage spring; only the inner bushing part can be pushed in and provides a dual stage spring with a reduced output force of the second stage; or the shaft abutmentcan be eliminated completely to provide a conventional normal output spring. Thus, one can appreciate the universal capabilities of the multiple bushing part concept.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scopeof the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and rage of equivalency of the claims are therefore intended to be embraced therein.
No comments:
Post a Comment