GAS CYLINDER PLUNGER LOCK

Abstract: A pneumatic spring having a cylinder (12) piston and piston rod (16) biased toward extended condition by compressed gas in the cylinder (12), an elongated cover tube (20) severed at one of its end (20′) to the outer end (16′) of the rod (16), extending over the length of the rod (16) to define an annular space (29) therebetween, and always in axial alignment with and extending over positons of the cylinder (12). A transversely shiftable plunger lock assembly on the cover tube (20) near its open end includes a fixed body (26) and a lock plunger (28) movable transversely of the piston axis into the annular space (29) when the rod (16) and cylinder (12) are extended, to abut the annular end (12′) of the cylinder (12) to securely retain the assembly in one position, preferably a substantially extended condition.

Description: This invention relates to pneumatic spring assemblies, sometimes called gas cylinders or gas springs. Such gas cylinders are commonly employed to assist in movement of doors or lids on vehicles or machines and the like e.g., for trunk lids or hatchback lids on automobiles, and for retaining such in one position, usually the open position. In several of the usages of such gas cylinders, the weight of the lid or door might overcome the bias of the gas cylinder and allow the lid or door to drop prematurely. Consequently, manufacturers of such cylinders have heretofore developed various types of latches to retain the gas cylinders in an extended or partly extended condition. DE-C-3 442 262 discloses a cocking sleeve arrangement wherein the sleeve can be cocked or tilted from one position aligned with the cylinder to a second position axially at an angle to the cylinder so that an offset end ledge or surface of the sleeve will engage the end of the cylinder to prevent its retraction. Unfortunately, such an arrangement can be accidentally released as by being bumped, allowing the lid to fall. Two other known arrangements herein volve the use of a laterally extending V-shaped spring arm or lever mounted on the piston rod and having an end biased to be cocked laterally to engage the end of the fluid cylinder, and a leaf spring-biased plate which is slid between the end of a fully extended cylinder and the end of an elongated sleeve spaced from the cylinder. US-A-4 078 779 employs a leaf spring along side the cylinder to enable a pin to retain the cylinder in a partially extended portion against further extension of the cylinder. US-A-3 789 742 employs a spring arm to retain the cylinder in a retracted position. US-A-3 851 867 has a pivotal element with an arcuate cam slot interfitted with a follower pin to control the position of the pneumatic actuator. JA-A-57-186 647 provides a rotatable interfit between a cylinder and a cover. EP-A-0 083 384 discloses a fluid spring assembly according to preamble of claim 1. The cover tube is formed by an elastic cover along the cylinder, which cover is fixed to the piston rod. The cover acts as a lock means, as it is deformed and blocked by a stopper provided on the cylinder at the time of full extension of the damper. The locking is released at the time of contraction. US-A-1 333 939 discloses an assembly comprising a cylinder, a rod, a piston and lock means, which comprise a lock plate supported by a body and movable on an axis transverse to the axis of said rod and cylinder between an inner position extending into a recess in the piston or in the piston rod and a radially outer position outside said recess. There are means biasing said lock plate to said radially inner position to abut said rod or piston in an extended position of said rod for locking the cylinder and the rod in said position. Furtheron there are means for allowing shifting of said lock plate to said radially outer position against the bias of said biasing means to release said assembly from said extended position. The engagement between said lock plate and said piston or piston rod can be released just by shifting of said lock plate. It is an object of the invention to develop a fluid spring assembly which is very simple in design and which cannot be accidentally released. The present invention pertains to the combination fluid spring having the usual cylinder and outwardly biased extended piston rod, and having a cover tube with one end secured to the outer end of the piston rod and the other end open and always extending over portions of the cylinder of the pneumatic spring. The cover tube is always axially aligned with the cylinder. It has a diameter larger than that of the cylinder and extends over the full length of the extended portion of the cylinder rod outside of the cylinder housing, even when the rod is fully extended. The tube mounts a transversely shiftable plunger lock assembly formed of a body and a lock plunger movable therein on an axis transverse to the cylinder axis when the piston rod is extended and, biased inwardly into the cover tube to abut the annular end of the cylinder for retaining the assembly in a substantially extended position. Said means for enabling shifting of said lock plunger to said radially outer position is inactuable due to side loading engagement between said cylinder end and plunger end until said lock plunger is disengaged from said cylinder annular end by further extension of said rod from said cylinder. Further advantages and features of the invention will become apparent from the ensuing description of an exemplary embodiment, taken in conjunction with the drawings. Fig. 1 is a side elevational view of the combination with the cylinder in its fully retracted position; Fig. 2 is a side elevational view of the combination with the cylinder in its fully extended position; Fig. 3 is a fragmentary side elevational view of the combination with the cylinder locked in substantially extended position; and Fig. 4 is an enlarged fragmentary sectional elevational view of the combination. Referring now specifically to the drawings, the combination 10 includes an elongated hollow cylinder 12 of conventional type defining an elongated cavity therein and having a conventional connector 14 on one end thereof for attachment to a vehicle, a machine, or the like. Within cylinder 12 is a conventional seal and piston subassembly 17. Connected to this piston (not shown) and extending out the end of cylinder 12 opposite connector 14 is an elongated piston rod 16 movable between one extreme retracted position wherein said piston rod is substantially within cylinder 12 (Fig. 1) to the extreme extended position wherein said position rod 16 is substantially outside of cylinder 12 (Fig. 2). The elongated piston rod 16 has a much smaller diameter than the cylinder diameter and is axially aligned therewith. The piston rod 16 thus has an inner end in the cylinder 12 and an outer end outside of the cylinder 12. The end 12′ of cylinder 12 through which rod 16 extends is annular, having a seal around the rod in conventional fashion. The cylinder chamber between the seal and piston subassembly 17 and connector end 14 contains a fluid, typically a compressed gas to bias the piston rod 16 outwardly of the cavity i.e., to bias the cylinder 12 and rod 16 to the most extended condition depicted in Fig. 2. The outer end of rod 16 has a connector shown as a ball socket 18. The particular connector employed at the outer end of the rod and the opposite end of the cylinder can be varied to suit the particular installation e.g., being ball sockets, being orificed flange connectors or otherwise as desired. Encompassing extended rod 16 and a portion of cylinder 12 is cylindrically shaped cover tube 20. The outer end 20′ of tube 20 has an end wall attached to the outer end of the rod. This may be achieved, for example, by socket connector 18 being threaded on the extended threaded stud 16′ of rod 16 (Fig. 4) after the orificed end 20′ of cover tube 20 is placed over the threaded stud. The inner end of tube 20 is open. Cover tube 20 is of sufficient length to always encompass the entire extended portion of rod 16 and a portion of cylinder 12. This is always axially aligned with cylinder 12. When the rod is fully extended, cover tube 20 extends over only a small portion of cylinder 12 (Fig. 2). When the cylinder is fully retracted, cover tube 20 extends over most of cylinder 12 (Fig. 1). Mounted to be integral with cover tube 20 near its open end i.e., opposite the end attached to the extended rod end, but spaced from the open end of cover tube 20, is a plunger lock assembly including a tubular body 26 secured as by welding and extending outwardly of cover 20. This tubular body 26 has an open inner end, the opening also extending through tube 20. The outer end of body 26 has an annular end around a central opening through which a plunger 28 extends. Secured to the outer end of plunger 28 outside of body 26 is a grippable element shown as a knurled knob 30. Inside body 26 and around plunger 28 is a compression coil spring 32. One end of this coil spring 32 abuts against the inner face of the annular outer end of body 26 while the opposite end of the spring abuts against the annular seat on plunger 28, to bias the inner end 28′ of plunger 28 toward the annular cavity 29 between rod 16 and surrounding cover tube 20. Plunger 28 is therefore biased toward the path of cylinder 12. The knurled knob 30 enables plunger 28 to be manually retracted transversely out of the path of cylinder 12 to allow cover tube 20 to move telescopically over more of the cylinder 12 when the unit is to be shifted to a retracted condition. The plunger 28 is shiftable reciprocally on its axis within tubular body 26 transverse and basically normal to the axis of cylinder 12, rod 16, and cover tube 20. Plunger 28 is spaced from end 20′ of cover tube 20 a distance less than the fully extended length of piston rod 16 beyond annular end 12′ of cylinder 12. Thus, when piston 16 is fully extended from cylinder 12, an axial space 29′ will exist between the inner plunger end 28′ and annular cylinder end 12′ (Fig. 4), enabling the plunger 28 to be automatically inserted under the bias of spring 32. Removal of the lifting force on the lid or door or the like may then enable the weight of the lid to retract the cylinder assembly slightly until annular end 12′ abuts plunger inner end 28′ as shown by phantom lines in Fig. 4. The plunger lock mechanism of the device as depicted will therefore securely retain the cylinder 12 in one position which is a substantially fully extended position. Withdrawal of the plunger lock must be purposely performed by retracting the plunger 28 using knurled knob 30. Accidental release is thus prevented. The frictional and side loading engagement between cylinder end 12′ and plunger end 28′ is usually sufficient to prevent this retraction until the cylinder 22 and rod assembly are again fully extended to create the space 29′ between the plunger 28 and cylinder 12. The novel combination is simple, reliable and easy to use. The cover fully protects the rod from damage or dirt which could interfere with the seal between the rod and cylinder end. The plunger assembly can be employed to accommodate the smallest to the largest diameter gas cylinders available. The plunger forms a positive stop for high degree of safety. It cannot be accidentally dislodged to allow a hatchback lid or the like to drop on someone. Opening of the lid or the like with extension of the gas cylinder causes the device to automatically snap into locked position. Release of the mechanism must be purposely done, preventing premature release.

Claims: A fluid spring assembly comprising: a cylinder (12) defining a cavity therein; a rod (16) movable axially inwardly and outwardly of said cavity between retracted and extended positions, said rod (16) having an inner end in said cylinder (12) and an outer end outside of said cylinder (12); a piston in said cavity on the inner end of said rod (16), slidingly engageable with said cylinder (12); fluid in said cavity for shifting said rod (16) outwardly of said cavity; said cylinder (12) having an annular end (12') around the extending rod (16); plunger lock means for holding said rod (16) in one position, comprising a cover tube (20) having one end (20') secured to said rod (16) outer end and having the other end open and around said cylinder (12), said cover tube (20) having a diameter larger than that of said cylinder (12), and extending over the length of the rod (16) outside said cylinder (12), defining an annular space (29) around said rod (16); characterized by a lock plunger body (26) on said cover tube (20), extending transversely therefrom; a lock plunger (28) supported by said body (26), movable on an axis transverse to the axis of said rod (16) and cylinder (12), between a radially inner position extending into said annular space in said cover tube (16) to abut said cylinder (12) annular end (12'), and a radially outer position outside said annular space (29); means biasing said plunger (28) to said radially inner position to abut said cylinder (12) annular end (12') in an extended position of said rod (16) for locking the rod (16) and cylinder (12) in said one position; and means for allowing shifting of said lock plunger (28) to said radially outer position against the bias of said biasing means to release said assembly from said extended position, wherein said means for enabling shifting of said lock plunger (28) to said radially outer position is inactuable due to side loading engagement between said cylinder end (12') and plunger end (28') until said lock plunger (28) is disengaged from said cylinder (12) annular end (12') by further extension of said rod (16) from said cylinder (12). The assembly of claim 1, characterized in that said lock plunger (28) is automatically shifted into said inner lock position by said biasing means upon extension of said rod (16). The assembly of claim 1, characterized in that said lock plunger (28) axis is normal to said axis of said rod (16) and cylinder (12). The assembly of claim 1, characterized in that said means for enabling shifting of said lock plunger (28) is a grippable element. The assembly of claim 1, characterized in that said lock plunger (28) and said body (26) are close to said cover tube (20) open end to allow said lock plunger (28) to move into said annular space (29) and into abutment with said cylinder (12) annular end (12') only after said rod (16) is in substantially fully extended position. The assembly of claim 1, characterized in that said cover tube (20) always is axially aligned with said cylinder (12) and said rod (16) and always extends over portions of said cylinder (12). The assembly of claim 1, characterized in that said cover tube (20) includes an opening for allowing entry of said lock plunger (28) into said annular space (29). The assembly of claim 1, characterized in that said biasing means is a spring (32).

Inventors: SCHUITEMA, FRANK M.
Applicants: SUSPA COMPART AKTIENGESELLSCHAFT
Application year: 1988
Main classification: F16F9
IPC codes: F16F9