NZ213495A - Airstay which can be recharged after assembly - Google Patents

Description

I • 213495 : Patform.*5 N1M ZKAIV\ND PATENTS ACT 1953 ODMPlJSre SPECIFICATION AFTER PROVISIONAL MO: 213495 f 16> OCT 1986 f DATED: S'jBSTf'-ri.v. •; ^ «-:t I 1*1 I •.** c-'09rr) 16 September 1985 AIR STAY We^ &£li KNTiSRBRISUS CO-LTDr a New Zealand company, of 14/1) Sutinyhill Crescent, Auckland, New Zealand do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to bf» p.irti cul arly described in nnd by tho followinq statement: ) -- ■f-v,'; """***"" * ' '*V • .-•*\V,A - 213495 This Invention relates to air stays and/or parts thereof, where the term air stay refers to springs or struts which, use a gas as a compressible medium for providing resilience. Commonly this gas is held in a sealed chamber, into which a piston or other member can move so as to reduce the volume of the said chamber, without any exit being provided for the gas. The gas is consequently compressed when the piston or other member is forced into the chamber, and expands, pushing the piston bac)c out, when force bearing on the said piston is removed. By having the gas in the chamber pressurized, ie. compressed bo some extent even when the piston is out of the chamber, a more powerful spring is produced. It will be appreciated that, particularly when the gas is pressurized, the chamber should be sealed at all times. If pressure is lost over time or through accident the chamber must be opened such that more air may be pumped in, and then reseated. This operation has, with air stays hitherto available, most commonly involved releasing and losing all retained pressure in the process of opening the chamber, such that repressurizing an old air stay is as complex and difficult an operation as pressurizing a new one.

It can be seen therefore, that there is a need for means by which an air stay can be repressurized without disassembly involving gas in the sealed gas chamber being lost.

It is an object of this invention to provide an improved air stay or parts thereof, to go at least partway towards meeting this need, or to at least provide the public with a useful choice.

In one aspect the invention provides an airstay including a piston and piston rod, and a pressure chamber, said piston rod passing into said pressure chamber from the exterior through a piston rod passage, wherein said pressure chamber is provided with means by which said pressure chamber can be recharged subsequent to assembly and initial charging of said pressure chamber, by means including a seal, wherein said seal comprises an annular flexible portion in or adjacent said piston rod passage, capable of sealing around the entire circumference of said piston rod, being deforraable away from said pistion rod by pressure from the exterior, and deformable into sealing contact around the circumference of said piston rod by pressure from inside said pressure chamber.

Preferably the piston rod passage has channels in the surface thereof, said channels providing passage for gas in normal use and portions 213493 between the channels providing a bearing surface by which the piston rod is retained in the piston rod passage.

Preferably the 3eal comprises a frusto-conical lip in or adjacent the piston rod passage.

In mother aspect the invention provides valve means for an airstay through which gas may be added to the pressure chamber of the airstay, said valve means being capable of remaining in an operable state subsequent to assembly and initial charging of the pressure chamber, said valve means including a frusto-conical lip disposed about the piston rod of the airstay.

In a further aspect the invention provides a method of manufacturing air stays, wherein pressurizing of a gas or air chamber of the air stay may be performed after assembly and/or sealing of the chamber.

Preferably pressure in the gas or air chamber of the air stay is increased by introducing the stay or parts thereof to higher external pressure than internal.

Preferably also, the method of manufacture includes sealing the gas or air chamber, or parts thereof, in a substantially permanent manner.

Preferably the gas or air chamber is formed with metal tubing and plugs, such that the tubing is stopped up at either end with the plugs, and then bent or crimped to substantially permanently fix the said plugs in place.

In another aspect the invention provides a ball and socket joint, wherein the socket is formed in two parts, each part having at least two opposed socket walls.

These and other aspects of this invention, which should be considered in all its noirel aspects, will be made apparent in the following description, given by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a preferred embodiment of the invented air stay in Figure 2 shows the invented air seal from the same embodimerj side elevation, truncated and in section 2 1 - :• 9 5 Figure 3 shows the preferred end fitting and wedge lock, in side elevation and in section, in combination with a ball coupling (dotted) as might commonly be used.

Figure 4 shows an air stay of the embodiment shown in figure 1 in combination with a repressurizing chamber.

In its preferred embodiment the invented air stay consists broadly of a cylindrical chamber 10, stopped at both ends, and a plunger 20. The chamber 10 is preferably formed from metal pipe, crimped over a seal or stepper at either end so as to be air tight. Hie thickness of the metal in proportion to the diameter of the pipe will be dependent on the end use intended for the stay, and the intended internal pressure.

The plunger 20 is in the preferred embodiment made as a solid rod, round in cross section, with n pintnn of brass or plastic 21 on one end, inside the chamber 10. The piston 21 is not intended to form an air tight seal with the walls of the chamber 10, although in other embodiments it is possible that it might, rather in this preferred embodiment it is intended only to act as a guide to keep the plunger on the right line, and to prevent the plunger being removed or evicted from the chamber 10 entirely. Thus it includes an O-ring seal 23 to maintain contact with the walls of the chamber 10, and an air vent 24 through which the air can pass. The vent 24 may be small, such that passage of air from one side of the plunger to the other is slowed, and the speed at which the stay can be compressed is limited.

Further to this, oil 25 or some other fluid may be held in the bottom of chamber 10 to further slow the last stages of compression. Being thicker and more viscous than air, the oil takes longer to pass through the vent 24, and compression is as a consequence slower.

At the other end of the plunger there may be some form of coupling or fastener 22, such as one of the type described below, to connect it to an article intended to Ixs resiliently braced.

The stoppers at either end of the chamber 10 are different, and perform different functions. The stopper at the top, 30 as shown in figure 1 acts as a seal and a valve? the stopper at the bottom 40 as shown in figure 1 acts as a coupling.

The stopper 30 has a central bore 31 through it, through which the rod of 2id49o the plunger 20 passes. It is indented 32 near the top, Eor the pipe of the chamber 10 to be crimped into, and might be made of a slightly soft plastic, preferably Acetyl, or possibly nylon, so as to form an airtight seal. It is preferable that it is able to withstand a standard temperature range without deforming or denaturing. -10°c to 40°c should be sufficient in most circumstances, although the end use will naturally determine a preferred temperature range which differs from this in some cases. The bore 31 is of a diameter substantially equal to that of the rod of the plunger 20, so as to form a bearing surface for the rod, but is equipped with one or more 'grooves' 33 running along its length along which air or gas can pass.

At the base of the stopper 30, a sealing lip 34 is provided. As shown in figure 2, this is preferably formed as a separate valve element 35 fitted into the stopper 30, but alternatively it could be formed as an integral part. The lip 34 when in position extends frusto-conically into the bore 31, and towards the Interior of the chamber 10. The grooves 33 in the surface of the bore 31 are not continued through the lip 34, so that in normal use the lip 34 contacts the plunger 20 around its entire circumference, and can form an airtight seal. An annular recess 36 is provided behind the lip 34, which allows difference between pressure in the chamber 10 and external pressure to open or close the lip relative to the plunger 20. When pressure in the chamber 10 is greater than external air pressure, as will be the case in normal use, the internal pressure in the recess 36 will press the lip upwardly and inwardly into sealing contact around the circumference of the plunger 20. If external air pressure is increased to a level greater than pressure in the chamber 10, the lip will be pressed downwardly and outwardly into the recess 36, and out of sealing contact with the plunger 20, allowing air to enter the chamber 10. In this way the plunger seal acts as a one-way valve, to allow air to enter chamber 10, but not to exit.

Preferably the valve element 35 is formed of a relatively soft and flexible material, such that it may better seal against the plunger 20, while the stopper 30 is made of a relatively rigid material so as to better bear and support the plunder 20. An O ring 37 of soft and flexible material may be provided around the stopper 30 to seal against the pipe of the chamber 10.

The valve element may be provided vith chamfered corners 38, and the stopper 30 be shaped to suit, for easier fitting of the one into the other. ^ -20CTV)87 2 1 3-: 9 The other stopper, 40, has in the preferred embodiment a coupling means by which the stay may be attached to an article such that it may be resiliently braced against an article at the opposite end of the plunger 20. This coupling means, and possibly also that at the other end, is in the form of a ball and socket joint. The socket is formed as a clip 41 which is open at the front and sides, and a housing 42 which is open at the front and rear, moulded as a part of the stopper 40, or alternately as a cap for the rod of the plunger 20. The ball 43 is slid into the clip 41 from one side, arid then the combination is clipped into the housing 42. The housing forms the sides of the socket, while the clip forms the top, bottom, back and frontal flanges, such that the ball is held in place. The clip 41 locks into th.e housing 42 with two lugs 44 which fit into corresponding detents in th.e housing, such that it is substantially permanently fixed in place.

The means by which an air stay is pressurized or repressurized after assembly can be a simple chamber adapted to withstand high internal pressure, with two apertures with 0-ring seals 51, 52 to fit around th« stay, and a one way valve through which air can be pumped. By this means the air pressure surrounding the stay can be increased to a level highei than that inside the chamber 10, such that air is pushed between the lip 33 and the plunger 20, thereby effecting an entrance.

It will be appreciated that a number of changes or alterations might be made to the above within the spirit or scope of this invention.

The preferred embodiment given above operates by compression of the air or other gas in chamber 10 hy increasing the amount of plunger 20 in the chamber, rather than by reducing the size of the cihamber in which the air is held.

Similarly, the relative sizes and volumes of the various parts may be altered according to need or desire, although the example cjiven above appears preferable at present.

Finally, it will be appreciated that a variety of other changes might be made to the above example within the spirit and scope of this invention, as characterised by the following claims:

Claims (1)

1. m -7- What We Claim Is: 215495 1. An airstay including a piston and piston rod, and a pressure chamber, said piston rod passing into said pressure chamier from the exterior through a piston rod passage, wherein said pressure chamber can be recharged subsequent to assembly and Lnitial charging of said pressure chamber, by means including a. seal, wherein said seal comprises an annular flexible portion in or adjacent said piston rod passage, capable of sealing around the entire circumference of said piston rod, being deformabLe away from said piston rod by pressure from the exterior, and deformabLe into sealing contact around the circumference of said piston rod by pressure from inside said pressure chamber. An airstay as claimed in claim 1, wherein said piston rod passage has channels in the surface thereof, said channels providing in normal use passage for gas, and portions between said channels ^7^*^;Q_ _;providing^ in normal use; a bearing surface by which said piston rod is retained in said piston rod passage. ^;* ^MO'f; An airstay as claimed in claim 1 or claim 2, wherein said annular flexible portion comprises a lip at: an end of said piston rod passage associated with the interior of said pressure chamber. ~ A fror 4/fO'O An airstay as claimed in any one of claims 1 to 3^ wherein^ said annular flexible portion comprises an extension from the piston rod passage surface extending frusto-conically from said surface and toward the interior of said pressure chamber, there being provided an annular space behind said extension continuous with the interior of said pressure chamber, whereby pressure in said pressure chamber and in said annular space acts to press said extension inwardLy into sealing contact around the circumference of said piston rod, and whereby excess pressure from the exterior of the pressure chamber acts to press said extension outwardly out of contact with the circumference of said piston rod, into said annular space. An airstay as claimed in any one of claims 1 to 4f wherein said piston rod passage is formed in a stopper, said stopper acting^ in use,to seal one -end of a tubular length of pipe, and said tubular & _ _ length of pipe forming the side wall of said pressure chamber < o s. V • f?2oamr -8- 213495 6- An airstay as claimed in any one of claims 1 to 5, wherein said seal is formed as an element separate from the surface of said piston rod passage and is fixed therein, said seal being formed from a relatively soft and flexible material, and said surface of said piston rod passage being formed from a relatively hard and inflexible material. 7. An airstay as claimed in claim 5 further( including a resilient sealing ring about said stopper, acting, in use to seal between „ ' f jQ said tubulair length of pipe and said stopper. Ji-tof) 8. An airstay as claimed in any one of claims 1 to 7, further including a connector associated with an external end of said piston rod and/or with said pressure chamber, including a socket for a ball-and-socket joint wherein said socket is fomed in two co-operating parts, each part including at least two opposed socket walls. 9. An airstay as claimed in claim 8, wherein one said co-operating part is spring-fitted into association with the other said cooperating part to form a complete socket. 10. An airstay substantially as herein described, with reference^ to any one of the accompanying figures. JANES W PIPER & CO Attorneys for the Applicant ZEE ENTERPRISES CO LTD