WO1989001578A1

WO1989001578A1 - Gas cylinder lifting device

Info

Publication number: WO1989001578A1
Application number: PCT/US1987/002047
Authority: WO
Inventors: Richard S. Pauliukonis
Original assignee: Pauliukonis Richard S
Priority date: 1987-08-20
Filing date: 1987-08-20
Publication date: 1989-02-23

Abstract

A gas cylinder lifting device is disclosed for height adjustment including all plastic housing (92), a plunger assembly (90, 91) incorporating a plunger (91) with a head or piston (103) which assembly (90, 91) is slidably movable inside a cylinder bore, the piston (103) disposed between opposite fluid chambers (100, 101), metering valve (99) within the piston (103), cylinder charging and discharging valve (97), and extendable and retractable actuating rod (98) for selection of various positions for the plunger assembly (90, 91).

Description

GAS CYLINDER LIFTING DEVICE

BACKGROUND OF THE INVENTION

1. Field of Invention .

This invention relates to lifting devices such as adjustable length columns generally, and to servo gas cylinders used for height adjustment in structures such as chairs, stools, tops and the like with improved controls specifically.

2. Description of Prior Art.

The use of gas-operated lifting devices is well known in the art.

Also known is the use of a gas cylinder in connection with a column of a chair, between a chair base and a seat or similar platform subject to height adjustment wherein the cylinder of prior art design pressurized to about 200 atu ( circa 3000 psig gas pressure ) is fixed to an underside of a chair seat securely while a piston rod end is secured to a base through a stand tube also called a guide tube which generally includes a thrust bearing for seat rotation.

In operation the movement of the piston inside cylinder while piston rod protrudes cylinder housing end a certain variable length determines the height of seat surface from the floor holding the base. This movement may be impeded by a manually operated valve connecting fluid chambers at piston sides exposed to the working fluid such as pressurized nitrogen, compressed air or liquid-gas mixture under pressure, or the like, totally independent of external pressure after the cylinder becomes energized. All prior art cylinders are fluid charged at the factory. As long as the working fluid flow between piston sides forming said fluid chambers is prevented, the height of seat surface is fixed. When the valve controlling fluid chamber flow becomes opened manually or by way of a external lever arm means incorporated therein, the height of the seat may be changed either downwards or upwards, within stroke limitations built-in into the cylinder. Upwards direction requires removing body weight from the seat so as to permit pressure force acting over the piston rod diameter lift the seat empty, while downwards direction requires adding external weight such as the weight of a person using chair to be placed over the seat so as to overcome constantly prevailing internal pressure force normally acting upwards. All prior art devices of this general type have no means for speed control during piston and seat position change.

The following list of relevant patents in this regard have been studied in detail: Pat. No Issue Date Inventor

3,656,593 April 18,1972 Fritz Bauer

3,711,054 Jan. 16, 1973 Fritz Bauer

3,762,514 Oct. 2,1973 Herbert Freitag

3,920,253 Nov.18,1975 Fritz Bauer

4,113,220 Sept.12, 1978 R.H.Godwin et al

4,257,582 March 2 4,1981 Winfried Wirges

A number of similar prior art devices including those listed above indicated the need for improvements on the following grounds. First, most of the designs are too complicated and too costly. Several involve more than one cylinder while others di vide a single cylinder bore into more than two separate chambers using intricate and complex arrangements. In turn,the manufacture of lifting devices of prior art complicated design entails unnecessary time and production expenditures. For example, operating a device of prior art design pressurized at 200 atu (ca.3000 psig) is not only unsafe but also difficult to control in contrast with low pressure operation of a simplified design of the present invention which includes simple flow and speed control means to 500 psig only when used with many times larger diameter piston. Second, prior art lifting devices generally require additional structure such as the stand tube spaced and secured inside a chair base in order to adequately support the outwardly protruding cylinder housing secured inside stand tube bottom in a coraplicated fashion by way of a tiny piston rod end passing a thrust bearing spaced therein. Furthermore, due to requirements to factory precharge units from high pressure source of gas be it Nitrogen or Carbon Dioxide or other gas mixture, for each application a totally new and different unit evolves in order to meet force reqviiretnents of structures such as chair,stool, table or the like. In turn a plurality of factory precharged units nust be maintained, inventorized and shipped under pressure, all complicating the issue and raising the costs, let alone safety high pressure dictates.

The present invention alleviates the above disadvantages and improves the state of the art of gas cylinders many ways. First, it permits cylinder charging-recharging in the field from standard compressors generally limited to 150 psig air pressure. Secondly, it includes metering valve flow control means for operational speed control of the unit.Thirdly,it eliminates the need for costly guide tube since the cylinder housing of the present invention is adaptable of mounting directly into the chair base without the need for stand tubes discussed. In fact, operating cylinders below 500 psig rather than 3000 psig in prior art cylinders eliminates the need for extra thrust bearings due to drastically reduced pressure-induced-friction, in particular in metal cylinders which generally exhibit internal rusting and corrosion with time due to trapped moisture even with Nitrogen charge. In turn, it revolu tionizes the art of lifting devices beyond and above the presently known and existing designs, in particular in the preferred embodiment of the present invention by providing a structurally different form adaptable to low pressure unit operation when constructed from low cost materials including injection molded parts from modern Engineering Plastics.

SUMMARY OF THE INVENTION

Obviously, the general objects of the present invention is to overcome the deficiencies of the prior art cited, and to provide an improved lifting device through design simplification for reduced cost in manufacture and use.

These objects are achieved according to the invention by providing an adjustable servo gas cylinder constructed for low pressure operation with improved safety and cylinder charge-recharge capability in the field via an integral springless check valve means incorporated inside a fluid port thereof. To serve applications requiring height adjustment means such as those found in modern stools, chairs, table tops and the like, present invention permits unit operation without external energy source except for gas filled cylinder housing provided with an axially displaceable piston of an outwardly movable rod adaptable of being stopped at a desired position between stroke limitations by an outside operable blocking device which includes metering valve for flow control between fluid chambers separated by the piston resulting in a considerably simpler construction of the unit with individual parts produced by inexpensive injection molding process wherever suitable. More specifically, an object of the present invention is to provide a servo lifting device that permits standardization of units by field pyessurization, de-pressurization and re-use eliminating countless numbers of models with different force magnitudes let alone different strokes, a feature not even anticipated by prior art devices but presently offered by way of integral check valve means incorporated therein. Further object of the present invention is to provide servo lifting device which structurally differs from prior art designs to insure unit construction from low cost materials including injection molding parts from plastics capable of sustaining pressure and service abuse, in particular that injection molding process permits reduction of parts facilitating savings in cylinder production. lifting devices from plastics would also eliminate rust and corrosion problems plaguing prior art metal counterparts. lifting devices of this general type which require fewer components and are light are obviously desirable because they provide long lasting, simple, inexpensive and reliable means for serving many applications beyond those common to the prior art. Specifically, airline, automotive and bicycle industries, among many others wherein reduction of weight and properties such as anticorrosion, non-conductive electrically are at premium would benefit from this novel development considerably.

Other objects reside in novel details of construction and combination including arrangement of parts, all of which will be apparent from the description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of the invention, it is believed the invention will be better understood from the following description taken in conjunction with the drawings. It will nevertheless be understood that no limitation of the scope of the invention is therby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. IN THE DRAWINGS :

FIG.1 is a cross-sectional view of a servo gas cylinder for adjustable height according to the invention without piston, using simple plunger with seal instead; FIG.2 is a fragmentary view of gas cylinder of FIG.1 modified to include small piston at the plunger end with plunger body serving as a piston rod;

FIG.3 is a fragmentary view of another end of gas cylinder shown in FIG.1 modified to include external actuating means for operational control of the unit;

FIG.4 is a section of piston rod end provided with alternate operational control means of the unit, offered as a selective option;

FIG.5 is a cross-sectional view of a simple all plastic servo gas cylinder including ribbed bearing surface inside bore end for piston rod support in bending.

FIG.1 servo gas cylinder for adjustable height is a unit of truly simplified construction that may be produced by injection molding fron plastics but it is not limited thereto,depending on applications. Specifically,in FIG.1 a rodlike pistonless hollow plunger 16 with seal 13 is slidably movable inside a dual cylinder smaller bore of plunger diameter between a first piston rod retracted position adjacent cylinder end stown and a second piston rod extended position to be defined by external stop (not shown). As such, this truly simplified cylinder can serve very well defined special applications only. The discovery of this structurally novel design is significant in that it illustrates potentials for simplification. In FIG.1 an elongated tubular housing 1-a with an integral end wall 2 at a protruding plunger end 3 and an opposite end wall 5 with an integral elongated internal cylinder 5-a is adaptable of being assembled into a housing bore 20 against a shoulder of a counterbore 2-a to form an annulus 19 therebetween after a plunger assembly 12 is sealably inserted inside cylinder bore 6. End wall 5 may be secured inside housing first open end 1-b by threads or otherwise fixed by either ultrasonic or friction welding or equally strong glueing techniques considered standard in plastics industry. The same pertains to the end wall 2 inside second opposite end 1-c of housing 1-a if desired, but if ultrasonic or fric tion welding is chosen for attaching end walls 2 and 5 to integral cylinders 1-a and 5-c respectively, no parting lines between parts so assembled will be visible as can be seen in FIG.1.

A fluid port 5-b central to the end wall 5 is provided for supply of working fluid under pressure, be it compressed air,nitrogen or carbon dioxide gas alone or mixed with lubricants for delivery into cylinder inside 8 via a springless floating check valve 7 incorporated therein.For plastic cylinder, compressed air under 150 psig pressure may be used with success as proven by experiments with prototypes, machined from plastic rod to ascertain design and operational validity.Check valve 7 may include a tee-shaped floating pin 7-a with a round head 7-b at a first pin end protruding into cylinder inside 8 via an orifice 10 of port 5-b so as to receive a seal 9 inside a peripheral groove adjacent a seat surface 11, while a second opposite larger diameter pin end 7-c may be flat of tee-configuration shown or it may be winged to provide a stop for axial pin motion inside port 5-b while permitting unobstructed passage for fluid flow during cylinder charging-recharging steps. Note that during cylinder charging, fluid pressure forces pin 7-a along with seal 9 floatingly forward away from seat surface 11 to permit fluid supply to cylinder in side 8. However, when the supply of the fluid from outside is disconnected, the position of pin 7-a automatically reverses due to internal fluid force action over pin head 7-b forcing seal 9 against seat surface 11 rendering check valve bubble tight shut.An end plug 5-c inside port 5-b must be used to secure unit free of tampering and safe,unless cylinder is depressurized or re-charged again for either augmentation or lowering of internal force by first removing plug 5-c, applying external force to tee 7-c for unseating seal 9 to render check valve 7 open to exhaust,and vice-versa.Working fluid under pressure inside cylinder exerts a pressure end force over plunger assembly 12 equal to plunger area defined by diameter of plunger seal 13, spaced peripherally inside a groove thereof times the pressure ur ging a position change of the plunger assembly 12 from that shown in FIG.1 to another (not shown) with plunger assembly 12 extended beyond the end wall 2 as far as the plunger stroke permits. The stroke is measured by the distance traveled by the seal 13 of a first plunger end Ik inside the cylinder bore 6 normally provided with appropriate abutments. Theoretically, the plunger assembly 12 of FIG.1 has unlimited stroke, since the seal 13 can travel from the position shown passed a stationaiy housing seal 15 inside appropriate groove of end wall 2 when subjected to an end pressusure at cylinder inside 8 forcing the cylinder assembly 12 to disengage from cylinder bore 6 unless resticted externally within stroke selected between that shown in FIG.1 with plunger retracted to another (not shown) with plunger extended but not more than up to the counterbore 2-a shown. In practice, therefore, the stroke of gas cylinder of FIG.1 is controlled by the application wherein external means to restrict plunger travel are present, unless plunger is provided with a head at the end Hi to act as a stop defining the stroke inside the gas cylinder boundaries in stead, as per plunger modifications shown in FIG.2.

Plunger assembly 12 of FIG.1 consists of hollow plunger 16, sized to fit bore 6, with central passage 17 between the plunger ends adaptable of receiving an elongated actuating rod 18 spaced inside thereof so as to terminate with a metering valve 18-a in the end 14 for regulation of fluid flow between fluid chambers at each side of the seal 13 formed inside cylinder proper when plunger assembly is urged to move axially therein. Conversally, actuating rod 18 is an outside operable blocking device. Assuming that the internal stroke of FIG.1 gas cylinder is restricted by external abutment means defining stroke limitations without plunger disengagement from bore 6 of a first internal cylinder 5-a of the dual cylinder housing 1 in service, the unit operation can be defined as follows.

When the actuating rod 18 becomes moved from the position of FIG.1 externally by pressing physically over a protruding first rod end 18-b, an opposite second end 21 thereof inside plunger end 14 unseats a seal 22 of metering valve 18-a from a face 23 covering an orifice 24 for fluid communication between fluid chambers at each seal 13 side formed inside cylinder proper urging plunger position change from that of FIG.1 with plunger retracted to a second plunger extended position (not shown). FIG.1 identifies a first fluid chamber formed at cylinder inside 8 facing both the check valve 7 and the plunger face 23 however limited in size due to adjacent location of seal 13 which separates it from a second fluid chamber on the right thereof. The second chamber of FIG.1 is formed by the annulus 19 jointly with a small annular space 19-a between the outside diameter of plunger 16 and the inner diameter of bore 6 interconnected by a radial hole 21a at the end of cylinder 5-a adjacent counterbore 2-a. Conversally, no motion of plunger assembly 12 will materialize until flow between chambers is established to proceed from a first fluid chaster via orifice 24 passed a metering taper 26 of the second rod end 21 into the passage 17 protected by a seal 27 30 as to direct the flow via radial hole 25 into the second fluid chamber or vice- versa, depending on the position plunger assembly 12 has assumed inside bore 6.

Theoretically, infinite number of positions can be selected within given stroke at speeds controllable by metering valve 18-a inside orifice 24. Depressing end 18-b of actuating rod 18 more increases the speed of plunger motion due to increased orifice flow taper 26 permits between chambers. Releasing rod end 18-b automatically stops the motion, rendering plunger fixed at any position selected due to the fluids trapped in each respective chamber and protected by seals 22 and 27 respectively. Seal 27 at a shoulder 18-c of actuating rod 18 is always slightly larger than the seal 22 resulting in a larger pressure-end force over seal 27 so that the whole actuating rod 18 automatically returns to a first rod seal 22 bubbletight shut position with rod end 18-b protruding plunger end 3 for actuation externally. Also is to note the fact that the rod end 18-b entering a reduced diame ter oppening 17-a is provided with s shoulder 18-d to contain actuating rod 18 inside passage 17 safely in case O-ring 22 fails.

Note further that the rodlike plunger 16 in contact with inside diameter of bore 6 may also be beneficial due to an extra long bearing surface therebetween to take side loads in service reducing bending stresses developed, and for rigidity. Tapers shown on the housing end by 28 as well as on plunger end 3 of FIG.1 identify most simple accepted means for unit attachement to a structure such as a chair allowing taper 28 enter a mating receiver bore of a base(not shown) while the tapered plunger end 3 may be received by a tapered receiver under the seat thereof, but they do not represent the limits. Other means of unit attachement to a structure such as a chair, stool , table or the like may be selected from threaded to shouldered end configurations without departing from the scope and spirit of the invention with equal success. Conversaly, the cylinder mounting along with attaching the plunger end into a structure in the field is selectable from tapers of FIG.1 shown alone or in combination with many other options. In some applications it may be preferable to use a servo gas cylinder with housing end tapered while the plunger end is hexagonal, or even square, while in other applications the cylinder end may be flush and provided with a threaded boss even when plunger end is tapered. Conversally, the unit of FIG.1 does not have to be made from plastics.

Practically, pistonless plunger is limited to applications with light loads only, unless used for two position operation. Experiments indicated that plunger must be provided with a small head to maintain infinite positions between stroke limitations discussed. This will become more apparent by reference to FIG.2 which is identical to FIG.1 except for small piston at the plunger end 14. Operationally, FIG.1 description is applicable to that of FIG.2 in every detail. FIG.2 shows an end section of FIG.1 modified structurally in small detail since operationally the gas cylinder of FIG.2 performs exactly the same function as that of FIG.1. Specifically, FIG.2 gas cylinder is aimed to serve applications that require internal restrictions with appropriate abutments for plunger stroke limitations. Ergo, FIG.2 plunger assembly 32 will incorporate a plunger 30 with a small head or piston 31 with shoulder 31-a serving as a stop and a seal 33 otherwise totally identical to the plunger assembly 12 of FIG.1 in all detail. For example,the actuating rod 34 of FIG.2 is the same as the actuating rod 18 of FIG.1. And so is the metering valve 35 with a tapered section 36 inside orifice 37 closed by a seal 38 adjacent second rod end 39 protruding into a first fluid chamber 40 across a check valve 41 with a springless floating stem 42 provided with a seal 43 inside a groove thereof so as to render valve bubble-tight shut automatically by internal pressure of working fluid housed therein after charging the cylinder via port 44 of FIG.2,functionally identical to that of FIG.1 already described in detail. The only difference,therefore,is in details which outside of plunger 30 with head 31 include modifications such as an increased length of annulus 45 by elimination of taper shoulder 29 of FIG.1 so that FIG.2 annulus 45 can be increased to the maximum by extending tapered wall 46 of external housing tube 47 up to the threads 48 of an end wall 49 provided with an end seal 50 including a peripheral seal 50-a at the end of internal cylinder 47-a which in FIG.2 is not an integral part of the end wall 5 of FIG.1. This is so for a specific purpose namely to accomodate higher pressures and closer bore tolerances, let alone economics in case of difficulty to produce molded cylinders without draft in bore 47-b of internal, cylinder 47-a serving longer strokes. Finally, the use of plunger with head 31 providing shoulder 31-a to limit stroke against an appropriate abutment inside opposite housing end(not shown in FIG.2 but in FIG.3) when plunger 30 is fully extended increases also the volume of a second chamber formed by annulus 45 jointly with annular space 45-a formed by shoulder 31-a. In turn,this compensates for difference in volumes of the opposing chambers and improves unit operation in that pressures on both sides of plunger head become equallized. For example, assuming the plunger head is 1-1/8" diameter having , 994 inch² surface would create a volume in a first chamber with stroke 5" long V₁=5x.994=4.97 cu in. Assuming plunger is only l"dia with .785 in² surface by 5" long, the annular volume thereof will be(.994 in²- .785 in²)x5"=1.04 cu in.

Adding volume of annulus 45 to the above,using the same assumption that 5" is the lenght thereof but the inner diameter of the external tubular housing is say 1½" while to outer diameter of the inner cylinder is say 1¼",both being very realistic will provide a volume in a second chamber as follows:

1.04 cu in +(1.76 in²-1.23 in²) x5"=1.04+2.65=3.69 cu in=V₂

Comparing volumes, we see that V₁=4.97 cu in is larger than V₂=3.69 cu in and the ratio of volumes V₁/V₂=4.97/3.69=1.35 is considered good in practical terms. Obviously,increasing length of annulus 45 to enter housing taper 46 described before is beneficial for ratio improvement so that when plunger 30 is fully retracted the pressure in chamber two does not increase above safe limits but is close to that of chamber one satisfying the objectives of this invention. It is important to note here that such beneficial volume ratio would be difficult to obtain using conventional piston and rod assembly unless annual space includes ample volume compensator by increased cylinder length,or pressure is raised reducing piston rod diameter, contrary to the present design principle using plastics and low operating pressures acting over large diameter rods or plungers for equivalent end forces. In turn, the present invention is related to low pressure unit operation rather than the high pressure units of the prior art. Ergo, any structural relationship of the present invention to that of the prior art is purely incidental because of cited differences in not only design but in the operational principles as well. FIG.3 shows an end section of an opposite end of FIG.1 modified to include dual plunger seals 60 one of which may be a rod wiper spaced inside an integral end wall 61 of a housing 62, identical to that of FIG.1, plus a counterbore 61-a with an end 63 of an internal cylinder 64 abutting a shoulder 65 thereof with ample radial shoulder space to accomodate head of piston 31 with shoulder 31-a of FIG.2 therein as a stop,limiting the stroke of a hollow plunger 66 inside cylinder bore 67 of FIG.3. like in FIG.2, FIG.3 shows an annulus 68 of external housing 62 in communication with an internal annual space 69 via a radial hole 70. Unlike in FIG.1, plunger 66 of FIG.3 terminating with a tapered plunger end 66-a incorporates threads 71 adaptable of receiving external controls 74 wiih mating threads inside a cap 73 provided with a flat bottom 75 which is in contact with an end 76 of an actuating rod 77 to permit gradual depression of the actuating rod downwards when external controls 14 are turned sideways by protruding handle 72 facilitating novel means of unit operation with resultant plunger position change already described.

FIG.4 identifies another version of external controls at the end of a tapered plunger 80 provided with threads 81 to receive a mating cap assembly 82 which includes a cap 82-a with appropriate elangated slot 83 passing therethrough and adaptable of receiving therein a substantially flat actuating handle 84 in final assembly. Handle 84 is provided with a cam like surface 85 adjacent a protruding end 86 of an actuating rod 87 so as to gradually depress end 86 when handle 84 is pushed to the left forcing cam surface 85 over actuating rod end 86 externally thereby opening internal fluid passages for fluid communication between respective fluid chambers to result in plunger travel for position change in accordanwith the preceding description. Pulling handle 84 to the right permits an automatic rod return to the original normally extended position rendering metering valve of FIG.1 or FIG.2 bubble-tight closed, and vice-versa. Experiments with plastic lifting devices have further indicated that cylinders with long strokes dictate longer bearings inside housing end containing protruding piston rod for improved rigidity is service when piston rod is extended fully beyond the cylinder end. Additional bearing length inside cylinder bore end require length increase in cylinder housing. In turn, it was possible to further simplify servo cylinders of the present invention for use with chairs, stools or the like structures. By providing radially spaced elongated ribs along the added bearing length to the bore inside, not only rigidity of piston rod extended was attained but also extra volume provision between ribs materialized, satisfying needs for volume compensator discussed. Ergo, changing dual cylinder designs of FIG.1, FIG.2 and FIG.3 through removal of internal cylinders resulted in a simple single cylinder design with compensator of volume integrated therein so as to provide novel servo gas cylinder FIG.5 shows. It should be noted further that the long stroke plastic cylinders when tested indicated the need for strengthening piston rods from plastics as well. In many cases such piston rods may be injection molded from high strength glass or carbon fiber filled plastic resins. However, in applications with heavy side loads, long stroke cylinders may require piston rods constructed from either metal-plastic composites or simply made from metal resulting in a novel plastic-metal cylinder, combination within the scope and the spirit of the present invention.

FIG.5 shows such cylinder in cross section. Basically it employs the same plunger assembly of FIG.2 and FIG.3 with elongated piston rod assembly 90 of which piston rod 91 protrudes a closed housing end 92 provided with identical seals 93 at a first end of an elongated tubular housing 94 while an opposite second closed housing end 95 is provided with identical fluid port 96 including a check valve 97 with seal 97-a detailed before. An identical actuating rod 98 to that shown and described in FIG.1 by reference to actuating rod 18 including a metering valve 99 for control of flow between fluid chambers 100 and 101 interconnected by a side opening 102 in piston rod wall adjacent piston 103 to continue via central piston orifice 104 is spaced inside a hollow piston rod 91 to serve as an outside operable blocking device described. Volume compensator 105 along bearing 106 adjacent housing end 92 includes a set of radially spaced elongated ribs 107 for support of piston rod 91 in service. Although gas cylinder of F1G.5 is shown as an all plastic injection molded unit assembled from plastic molded parts, it is not limited to plastics in actual application due to reasons discussed in the preceding page.

In operation, upon a slight depression of actuating rod of either FIG.1, FIG.3 or FIG.5 the plunger can be set into motion. Depressing the actuating rod of servo cylinder of the present invention more increases the speed of such motion due to increased orifice flow between chambers the tapered rod portion of the metering valve permits. Releasing the actuating rod automatically stops the motion rendering plunger fixed in a position desired within stroke limitation incorporated therein due to the fluids trapped in each respective fluid chamber. The design of servo gas cylinder in accordance with figures 1-5 plus external controls of FIG.3 and FIG.4 therefore provides novel means of producing economical lifting devices of this specific type which when made from plastics are less costly to purchase and more safe to operate within standard precautions in great many applications such as bicycle seats, boating seats, airline stools including executive chairs and specialty equipment among many others requiring light weight and corrosion resistant characteristics no prior art devices entail.

The designs above identifying a preferred embodiment are not limited to unit construction from plastics in case of uncovery of other novel materials and/or manufacturing techniques adaptable to servo gas cylinders, including metal.

It will be obvious to those skilled in the art that various changes may be made in the above designs without departing from the scope of the invention, and the invention is not to be considered limited to what is shown in the drawings and described in the specification.

Claims

WHAT IS CLAIMED IS:

1. A self-contained lifting device for control of load with variable positions under force comprising: a totally enclosed elongated tubular housing having a cylindrical body with a bore extending lengthwise between the ends thereof from a first end which is closed by an end cap provided with an integral directional check valve means in a central fluid supply port thereof for cylinder charging with working fluid supplied thereto under pressure, to a second end which is open and adaptable of being closed by a slidably received elongated hollow plunger entering an end closure, said plunger including a head with a seal at a first plunger end closely fitting and axially movable along said bore,a plunger body of rod configuration extending from said head into a second plunger end through said end closure provided with rod seals to prevent fluid leakage therebetween when plunger is moved axially therein, means for cylinder discharging and recharging via said check valve means, an integral flow control means in said plunger including a metering valve central to a face of said head interconnected with a control rod means spaced therein between said first and second plunger ends to extend outwardly for actuation of said flow control means, two fluid chambers separated by said head seal inside said bore,first of which has smaller volume because of presence of said plunger body housed therein,a fluid communicationmeans ina closed-loop system between said fluid chambers via passages incorporated into said flow control means including means for cylinder operation by said control rod means after energizing said fluid chambers with working fluid supplied there - to via said directional check valve means initially and for operating said lifting device subsequently so as to either maintain said plunger in a fixed axial position by working fluid blocking plunger motion from each respective fluid chamber or to permit axial plunger motion without external power aid within stroke limitation provided therein when said control rod becomes actuated externally to open said metering valve for fluid communication between said fluid chambers, a bearing surface in said bore adjacent said end closure for supporting said second plunger end extending said end closure rigidly when subjected to side loading, said flow control means including a first elastomer seal to close an orifice of said metering valve in said plunger face spaced inside a groove of a first innermost end of said control rod provided with a short reduced diameter rod section extending inwardly with a taper for flow metering when said control rod becomes actuated, a second elastomer seal at a shoulder terminating said short rod section,a radial hole in a plunger wall supplying chamber fluid between said seals, said second seal of slightly larger size than the size of said first seal to insure a larger end force when subjected to the working fluid pressure than the end force exerted over said first seal thereby facilitating an automatic closing means of said orifice to maintain plunger position locked until said control rod becomes externally moved inwardly by a second plunger protruding small end thereof forcing said first end of said control rod with said first seal to move from a first bubble-tight orifice closed position to a second orifice open position facilitating fluid communication between said fluid chambers via said plunεer orifice and said radial hole of said plunger wall with associated plunger motion within stroke limitations provided therein, and when said control rod is released, said larger end force of said second seal forces said first seal to return to a first orifice bubble-tight closed position automatically, and vice-versa, said check valve means including a floating stem provided with a seal so as to comprise a springless valve adaptable of cylinder charging and re-charging in the field.

2. A device as in claim 1 wherein said tubular housing includes a coaxial externally spaced second cylinder sealably interconnected with said first cylinder so as to form a volume compensating annulus therebetween in communication with said first fluid chamber which contains said plunger body to reduce the difference between chamber volumes for better control of chamber pressures during plunger position change in operation.

3. A device as in claim 1 wherein said plunger head is of larger diameter than said plunger body of rod configuration extending from said head into said second plunger end through said end closure.

4. A device as in claim 1 wherein said bearing surface in said bore adjacent said end closure for supporting said second plunger end rigidly includes a set of elonted ribs radially spaced therein so as to provide ample volume space therebetween for augmentation of chamber volume of said first smaller chamber when said plunger head is of larger diameter than the diameter of said plunger body of rod configuration extending from said head into said second plunger end.

5. A device as in claim 1 wherein said first end which is closed by said end cap is all plastic one piece construction integral to said cylindrical body with said bore thereof the second open end of which is threaded and adaptable of being closed by said end closure provided with said slidably received elongated holiow plunger with a head of a diameter larger than the diameter of said plunger body of rod configuration, said larger diameter head and said smaller diameter plunger body comprising piston and rod assembly produced by fabrication from stronger materials for rigidity, said end closure including a peripheral seal incorporated therein to insure leak tight joint between said threaded second bore end, said end closure further including a set of elongated radially disposed bearing ribs with volume space therebetween comprising a volume compensator for said first smaller chamber and adding rigidity to the extending piston rod end beyond said end closure during cylinder position change with long stroke in contact with said bearing surface.

6. A lifting device for height control comprising: a pressurized tubular column inoluding an internal cylinder for receiving a plunger with a haad seel slidably movable therein forming fluid chambers at head sides with fluid passage means for communication therebetween in response to external control means with fine adjustment means incorporated therein to facilitate a position change of said plunger head including means of locking head therein while a plunger rod extends past cylinder end fo anchoring to a platform of a structure such as a stool, a chair, a table top and the like, subject to height adjustment, including cylinder charging and discharging means with pressurized fluid via a floating check valve means inside a fluid port of an end wall of a coaxial externally spaced cylindrical housing,said plunger including a valving means with tapered flow control means for alleging metered fluid flo between saidfluid chambers thereby adjusting speedcf plunger position change when actuated by said external control means which include an operating lever attached to a cap abutting a protruding end of an actuating rod incorporated therein so as to gradually engage protruding rod end for pushing downward against a biasing force of the working fluid housed therein far enough to intiate flow between said fluid chambers facilitating motion of the plunger therein until the operating lever is disengaged at a position defining height desired for an automatic piston locking, and viceversa, turning said operating lever with said cap against said protruding end of said actuating rod by way of threads permits unit operation with height adjustment independent of external power supply except for external weight of a magnitude larger than the internal fluid force that must be added to insure downward motion of said platform.

7. A gas cylinder lifting device comprising: a rechargeable pressurized tubular column with dual cylinders of which a first external cylinder represents a housing thereof while a second internal cylinder of slightly shorter length performs a pressure lifting function by a hollow slidable plunger assembly adaptable of being mounted into a structure such as a chair, a stool or similar equipment, said first cylinder including a bore passing therethrough between the open ends thereof of which a first end is provided with an end closure adaptable of receiving a rod of said plunger assembly sealably including peripheral grooves for seals and a counterbore spaced inside thereof for accomodating a first fully open end of said second internal cylinder against a shoulder that also serves as a stop for a head of said plunger during plunger position change in service, while a second open end of said first cylinder is closed by an end cap adaptable of receiving sealably a second end of said internal cylinder, said second internal cylinder including a bore.passing therethrough with a first open end spaced against said shoulder of said counterbore adaptable of receiving said plunger head with a seal slidably movable therein between a first plunger retracted position abutting said end cap and a second plunger rod fully extended position limited by said counterbore shoulder defining cylinder stroke and forming fluid chambers at both head sides, an annulus formed between said first external and second internal cylinders and also between saidplunger rod and second cylinder bore interconnected therebetween by a radial hole in a wall of said second cylinder open end adjacent said counterbore together comprising a first fluid chamber, a fluid port in said end cap of said second cylinder ends provided with a springless check valve for charging and discharging fluid under pressure to and from cylinder proper respectively in communication with a second fluid chamber totally separated from a first fluid chamber by a metering valve incorporated into a face of said plunger head, an actuating rod means inside said hollow plunger interconnected with said metering valve for control of metered fluid flow between said fluid chambers facilitating plunger position change at variable speeds controllable by depression of an actuating rod end protruding said plunger rod end a small distance externally, means of mounting said tubular column by the ends thereof into said equipment, and means for operating said tubular column by external control means, and when said actuating rod becomes depressed, flow between said fluid chambers permits plunger position change until said actuating rod becomes released at desired position fixed by internal pressure forces automatically closing said metering valve.

8. A device as in claim 7 wherein said tubular column with dual cylinders including said plunger, and said actuating rod means are produced by injection molding from plastics, along with said check valve stem, and said external cylinder with said first end wall comprising a one piece construction while said second cylinder with said end wall is also one piece construction produced by injection molding from engineering plastics, including said plunger with head incorporated therein integrally molded from plastics in one piece along with one piece construction of said actuating rod assembled with said plunger in final steps of cylinder assembly thereby facilitating great cost reduction in manufacture of such tubular columns.

9. A device as in claim 7 wherein said first external cylinder with said end closure is injection molded in one piece, including said second end cap thereof produced from plastics, while said second internal cylinder is metal assembled thereto to result in a double walled tubular column requiring long stroke,difficult to wake by injection molding in tubular sections without draft, thereby facilitating mixed unit fabrication by combining plastic with metal components assembled sealably together for best results, including said plunger with said head from metal for heavy side loading in cylinder service.

10.A device as in claim 7 wherein said external control means include a cap secured to external threads of the protruding plunger end, said cap provided with a lever for fine adjustment of said actuating rod end when said lever is moved horizontally back and forth so as to facilitate cam action provided therein capable of gradual depression of said actuating rod end when the horizontal direction is changed,and vice-versa, moving said lever to the opposite direction unloads said actuating rod automatically.

11. A self-contained gas lifting device comprising:

an all plastic cylinder housing with an elongated tubular bore passing therethrough including end walls in said bore of which a first end wall is provided with a fluid port including a check valve means incorporated therein for supply of working fluid into a cylinder inside with capability of cylinder charging under pressure for cylinder operation without further supply of external power thereto, a piston and rod assembly movable inside said bore axially between a first piston rod extended position and a second piston rod retracted position including fluid chambers between piston sides and respective end walls in said bore, a second end wall in said bore provided with piston rod seals inside a central opening thereof, an actuating rod with metering valve means incorporated therein for control of cylinder operation at variable speeds within said first and said second piston rod positions when said actuating rod becomes depressed, and means for holding said piston and rod in a fixed position selected between said first and second positions by the working fluid trapped in each respective chamber when said actuating rod becomes released automatically closing said metering valve means therein until said actuating rod becomes depressed again, a bearing surface entering said bore inwardly from said second end wall towards said first end wall partway so as to form a set of elongated ribs therein for piston rod support when extended and for chamber volume increase space between said ribs provides.