US3868097A

US3868097A - Liquid spring

Info

Publication number: US3868097A
Application number: US763495A
Authority: US
Inventors: Paul Hollis Taylor
Original assignee: Individual
Current assignee: Tayco Developments Inc
Priority date: 1968-09-25
Filing date: 1968-09-25
Publication date: 1975-02-25
Anticipated expiration: 1992-02-25

Abstract

An improved structure and method of assembly for all pressure fluid systems and adapted particularly to the manufacture of low cost high pressure liquid springs, spring shocks and apparatus.

Description

United States Patent [1 1 [111 3,868,097

Taylor *Feb. 25, 1975 LIQUID SPRING 378,976 3/1888 Ritchie 220/66 934,174 9/l909 Hooker 220/66 [76] memo Paul Taylm 38 5 3.256.005 6/l966 Taylor 267/64 A Grand Island. NY. 14072 1 Notice: The portion of the termof this FOREIGN PATENTS OR APPLICATIONS Pawnt subsequent 10 p 1990- 928,388 6/1963 Great Britain 267/64 has been disclaimed.

[22] Filed: Sept. 25, 1968 Prinmry Examiner-James B. Murbert [2|] Appl. N0.: 763,495

[52] US. Cl. 267/124, 267/64 R [57] T C [5 l] Int. Cl. Fl6f 9/36 2 Field of Search 267/64- 64 1 13, An improved structure and method of assembly for all 267/129; 220/66 pressure fluid systems and adapted particularly to the manufacture of low cost high pressure liquid springs,

[ References Ciled spring shocks and apparatus.

UNITED STATES PATENTS 339,812 4/1886 Ritchie 226/66 9 Claims, 17 Drawing Figures .PATENLED FEB 2 5 I975 SHEET 1 0F 5 INVENTOR.

fazlfl? zyzor PAIEMEBF 3.868.097

sum 3 (I 5 A v QQ W T \1 am W I INVENTOR.

PATENTEU FEBP. 5 19.13

SHEET 8 INVENTOR.

mmum 1915 $868,097

SHEEI 5 BF 5 INVENTOR.

PauZfi QZyZor 1 LIQUID SPRING BACKGROUND OF THE INVENTION Rolled or keyed pressure vessels are in common useage in low pressure fluid systems but have never been successful in high pressure vessels. Use of crimped, levered end closures overcomes these existing deficiencies.

SUMMARY OF THE INVENTION A crimped structural end attachment for a pressure vessel particularly suited for making low cost liquid springs, spring shocks and apparatus.

1 DESCRIPTION A crimp comprising a series of radial gatherings at the end of a cylinder in which the metal is formed without substantial prestressing or stretching, holding an end cap by lever action against the edge of a relief in the cap, or using the short contact to said cap created by metal spring back to effect a levered, reinforced high pressure cylinder assembly.

This invention is related generally to low cost Liquid Springs which use molecular compression for energy storage and more particularly to a method of manufacture of all mechanical end attachments for tubular structure whereby any force up to the rupture force of the tubular structure can be obtained without employing threads, rivets or weldments.

Containing a body of liquid or gas under pressure at low cost has been nearly as difficult a problem as sealing sliding piston rods which pass through cylinders. Numerous methods of accomplishing end closures for all tubular structure are used in present day production. For higher pressures the most common method is to make cylinders with a solid end with the utilization of an enlarged threaded section at the rod end which has less stress first due to rod area and which enlargement secondly reduces the stress level at the root of the thread to stress limits which are 60% to 70% of the cylinder wall. The enlarged end is generally l% of the area of the cylinder in which the piston reciprocates. Sometimes both ends are threaded with a loss of efficiency spacewise. This provides long life with repeated flexure as is detailed in most stress data on materials. Because of the difficulties of manufacture, more often than not, this enlargement for threads is accomplished by increasing the external dimension at the threaded end. This however reduces the efficiency of the device when compared with the volume it occupies, due to the enlarged ends, since in most instances, the cavity or clearance for the tubular structure or Liquid Spring or other hydraulic device must be sufficient to accommodate the large ends. Where said enlarged ends are formed inwardly, to provide a smooth exterior, and more efficiency spacewise the threaded section is reduced below the bore of the tube which makes it difficult with respect to flow or with cylinders to machine and finish. In the most common application of a headed piston it makes it impossible to get the cylinder head in the cylinder bore. This has restricted this construction to Liquid Springs with a small piston or spring shocks which employ an inner shock tube similar to my US. Pat. No. 3,256,005 FIG. 4 and FIG. 15. However, this construction is totally unsuited for hydraulic and/or pneumatic cylinders where an enlarged piston head is used which is slidable in the bore. (Such as FIG. I of the subject Patent.) In addition, either the inwardly formed enlargement or the outwardly formed enlargement for said threads increases material costs since the per pound cost of tubing has a cost base 300% of bar stock, and labor direct costs increase to the point where such devices were unacceptable for the lower pressure, high volume, high production type of work. In these latter products straight thin wall tubing, end caps and threaded tie rods restraining said end caps are generally used. Liquid springs and high pressure hydraulic and pneumatic cylinders generally cost 60% more than conventional tie rod cylinders for this reason. In the case of pneumatic and hydraulic cylinders, snap rings are also sometimes employed with uniform heavier wall tubing which while less costly than threads, provide substantial holding power. Neverthe- I less, snap rings develop the same difficulty as the thread in that the root of the snap ring groove fails first, either by fatigue or load. In many instances using this construction, this inventor had distorted the entire end of the cylinder beyond the snap ring groove and the end had blown out. In the subject invention the effect of the snap ring without reduced wall weakness is accomplished.

Another method sometimes employed in fabricating hydraulic cylinders is that of using fusion or are welded end caps on uniform tube structure such as automobile shock absorbers, but this is only suitable for such extremely thin walled low pressure, small cyinders and is unsuitable for high pressure devices or large diameter low pressure cylinders with heavy walls. In thin tubes or small cylinders, the weld penetration provides a structure strong enough to withstand the pressure. The exception in thick wall tubes to this process is flash butt, electron beam or friction welding where a local enlarged weld section can be joined. The wall must be I 15% of the thickness of the wall joined since the weld carries an rating. This process, relatively new, eliminates some of the solid cylinder drawbacks men tioned heretofore but isnt any more efficient than the threaded wall spacewise and it is costly and time consuming.

By far, the bulk of the hydraulic and pneumatic cylinder manufacture comprises a low weight, low cost tube of uniform cross section fabricated, finished, honed and polished as one large tube. In this efficient method of fabrication, the tube is then cut to individual cylinder lengths. One tube end is'provided with an entrance radius to enter the seals and the entire assembly is clamped between two end caps which are held under sealing pressure against the cylinder by four or more tie bolts whose purpose is to hold the assembly together. While this latter construction is among the most prevelant in the low pressure high volume production cylinders, it is the most inefficient spacewise and also one of the most unreliable. The tie rods often stretch. The. tie rods are often asymmetrically loaded. In addition, they generally employ static face seals which require even tensioning. This structure cannot be used for moderate to high pressures and is totally unsuited for Liquid Springs.

The assembly time to run down a plurality of nuts on tie rods to uniform tension is tedious, time consuming, costly and requires reasonably close torque accuracy. Servicing said cylinders requires knowledge beyond most maintenance departments.

'When the above cylinders are repaired; it. is-normally done-either at the-manufacturers plant Ora-ta central I 4 l 4, US. PatNo. ;3',256,006)into which the cylinder is rolled, hydrostatically formed or otherwise displaced to replace threads or snap ring in restraining such end cap movement. These previous methods have all been dismal failures as while the liquid could be restrained by such methods, fatigue failures occured due tothe overstressed condition where said material, was rolled over an end cap or rolled into a groove. None ofthese 7 devices ever exceeded 50,000 cycles in life, whereas Since the annual change occurs at the same time for 7 most manufacturers, obviously, this overloads the repair facilities increasing cost further. Since the other elements of hydraulic apparatus-seals, rods, etc-now last relatively long, the fatigue limits of cylinders, tie

' rodsand threads are often exceeded before the second refurbishing is required. Thus the reliability of said devices afterthe first repair is doubtful; This results in costly breakdowns.

Even in the instances of Aerospace uses where the most costly enlarged threaded section is a must for space, weight and strength, the cost and time in repairing cylinders, especially in the event of a war on a far off shore, is exceedingly high and the logistics of shipping parts back and forth to repair bases is costly.

in addition to this, often the repairs are unsatisfactory and in most instances the military abandon the cylinder and install a new one. Consequently, in market surveys l have found a great interest even in military: uses for a throw-away cylinder which could be disposed of and a new one put in place. in the mass production processes, demand is very great. The economics of the situation indicate that a throwaway cylinder of 60% the subject of this invention has resulted in life in the.

millions of cycles exceeding allother construction including threads and, in fact,'havc yet to fail. in most in stances the cylinder wall fails elsewhere without failure at the end cap closure. 1

"The methods of cap retention noted above has resulted in tests in the holding of pressures to 40,000

p.s.i. with walls that'were only ca'pable of holding 20,000yp.s.i.twithout bulging. This was-accomplished by holding the cylindrical member in a closed cavity and just permitting the cap and crimped end to be exposed so that allpressure was imposed on the end cap at 40,000 p.s.i. The end cap had still not failed at l marilyj for low cost Liquid Springs, the method has the cost of the other types and, lasting thesame amount of time as a repairable unit, will effect a direct overall 'net saving of 40% with an initial cash savings of 40% because the first installationis only 60% of the total cost. This, in turn, will reduce the initial purchase price p of all types of apparatus thaternploy tubular structure try and consumer goods are increasingly throw-away items. provided costs are 60% of serviceable items; My

' process adds hydrauliecyllnd'ers and Liquid Springs to this class of merchandise. Additionally, in case ofA'erospace and products of-high stress, it has always been considered that any method of fabrication other than been found adaptable to Liquid Springs and hydraulic apparatus for high performance aircraft. It provides a tremendous cost saving in that all hydraulic apparatus is now cheapenough to be thrown away and not ser-- tubular attachment requirements and is not limited to hydraulic apparatus although it is particularly well suited where pressure is unidirectional as it is llTCOll" taining pressure in a cylinder. It will function with square or other cross sections. I Since this process is primarily designed for my specialty, molecular compressibility devices, (Liquid Springs), it is intended to lower the cost of such devices so that they will replace low cost coil springsin all 1 stamping dies. Heretofore my liquid die springs have threads or welding, could not be fabricated in the high V V I lhave'determined that pistons employing the porosity strength materialss'fherefore,the ability' to accomplish technologyand the'state of' the art. With my method disclosed herein, any material can beutilized as tubular structure and pressures retained therein. I have actually a low cost fabrication method in highstrength materials I has heretofore been deemed beyondthe capability of' been limited to special situations. For instance: refer-. ring to one actual application, the force requiredto 5 strip demanded a five station progressive die but Liquid l Springs (forces generally 20, times coil; springforces) Y permitted a one die'application, providing savingsin 'die'costs'. t r f Toincrease the market further; higher operating ve locities are desiredQSeaI frictiontis the limiting factor.

of cast iron or stainless stee'l cut frictionto half that for stainless steel pistons of bar stock thus doubling allowable cycle speeds.

Theoretical 2100F. on' the leading edgeof my seal at .l00 cycles Formerlydtwas essential, to have anenlargement or a thickened section of a cylinder for threads to restrict pressures up to 40.000 p.s.i, For a period exceeding 10-, 1

years this inventor has attempted to meclmnically hold to date have centered around a grooved end cap (FIG per minute 1 inch stroke with a: stainless pistonlmade from, bar stock. This; is'3 times" the temperature at which silicones and teilon vaporize. Actual tests with a high strength hollow stainless piston, boiled water in lOO cycles and melted nylonpowder (550F.) under continuous cycling at cycles per minute. Since cast 'materials:donot'condu ct heat aswell as barlstock. part of thcgain with-50% of the friction is lostias heat dissi pation isredu'ced. l seek in this application to increase 7 this dissipation.

calculations show temperatures of] It was further determined that heavy wall cylinders tended to contain heat. Design studies proved that dropping pressures from 20,000 p.s.i. to 10,000 p.s.i. and reducing wall thicknesses provided a spring having 85% of the energy capabilities since the large liquid volume replacing the steel gained energy and the heat dissipation out the wall'was enhanced. Crimping then became easier and a low cost commercial high speed liquid spring was provided.

The primary object of this invention is to provide a joining method for tubular structure which equals or exceeds the strength of the parent uniform wall tube, at the joint so formed.

The second primary object of this invention is to provide a low cost throw-away Liquid Spring, hydraulic or pneumatic cylinder.

A third primary object of this invention is to provide an efficient cylinder without end enlargements or highly stressed section.

Another primary object of this invention is to provide a method of forming which is capable of converting tubular sections of uniform cross sections to reinforced end wall closures.

The related object to this invention is to provide a Yet another object is to provide a low cost method of assembly for throw away hydraulic apparatus wherein the fatigue life of the cylinder exceeds the seal life so thatno downtime is created before the cylinder is worn out.

A related object is to force the replacement of structural elements of hydraulic apparatus prior to fatigue failure.

A Liquid Spring object is the reduction of friction in a high speed Liquid Spring.

A companion object is the dissipation of heat in a high speed Liquid Spring.

A further object is the lowering of Liquid Spring pressures and cylinder wall thickness wherein crimping can be accomplished.

A related object is the'reduction in wall thickness wherein high internal liquid temperatures can be more readily dissipated.

A companion object is topump liquids adjacent to the high temperature seal lip area to reduce and dissipate high temperatures therein.

Another primary object of this invention is to make closed cylinders for pressure use without threads. weldments, or tie rods.

A companion object is the reinforcing of end walls of tubular devices without heat wherein they contain an end closure.

A related object is the reinforcing of end walls of tubular devices without stress risers.

Another object is the reinforcing of end walls of tubular devices without stretching orprestressing the material.

The further related object of this invention is to provide a method of fabrication which can employ the highest strength materials in its low cost method of fab: rication.

A companion object is to provide a method of fabrication which avoids over stressing the retention means.

Another related object of this invention is to provide a method for the fabrication for precision hydraulic thrown away when repairs are necessary.

Still another object of this invention is to provide a method of fabricating a cylinderfrom uniform wall cylinders for ultra high pressuredevices such as Liquid Springs and Liquid Spring Shocks.

A secondary object of this invention is to provide a method whereby Liquid Springs can be fabricated in mass production using unskilled help.

Yet another related object of this invention is to provide a liquid spring assembly wherein the preload and end load can be automatically determined in the assembly processes.

Yet another object of this invention is to reduce costs and provide a throw-away cylinder whereby freight costs one way are saved.

Yet a further object of this invention is to eliminate all downtime except exchange time for hydraulic apparatus.

Another liquid spring shock object of this invention is to provide an energy responsive metering means.

A related object of this invention is to provide dampening response proportional to mass and/or velocity in a liquid spring shock.

Still another object of this invention is to eliminate all downtime due to repairs.

Yet another object of this invention is to provide a method of assembling all hydraulic or pneumatic apparatus by crimping.

A related object is to provide simple percussion or squeeze assembly procedure for pressure apparatus.

A further object is to provide hydraulic apparatus fabricated and assembled by press working.

Yet another object of this invention is to provide a FIG. 1 is a side elevation in section of a low cost Liquid Spring employing the method of fabrication by crimping the cylinder for holding the high pressure, end closure and seal therein.

FIG. 2 is a similar view of a vehicle spring shock, using an inner tapered shock tube and a uniform tube for the cylinder and employing solid end caps with an eye attachment for an atuomotive rubber isolation bushing and a seal and end cap in which cap retention is accomplished using metal spring back and the flare out forv seal entrance.

FIG. 3 is an enlarged fragmentary sectional view of the end closure of FIG. 1 in enlarged detail which illustrates the restraining forces for holding the end closures.

FIG. 4 is a typical end view after crimping of FIG. 1 or FIG. 2, showing how the cylinder metal was reformed, not stretched, to restrain the cap.

FIG. 5 is a view of an alternate stiffened wall before forming which is a means of lowering the wall yield or notch effect, for highest loads and life particularly in soft material.

FIG. 6 is a view after forming the end closure of FIG. 5 showing that the cylinder is still efficient spacewise.

FIG. 7 details a low costseal for use with the Liquid Spring of FIG. 1 with preload end stop shock absorber included in the seal and a heat dissipating hollow pis- I011.

a manner and using cast heads.

FIG. 8 .is an alternate method of constructionin' which the end flare and spring back of metal accomplishes the desired seal entrance-and end closure purposes and a'separate preload or end stop andshock absorbet is employed withmy older seal and a hollow piston for heat dissipation.

' I against axialr noveme'ntthus effectively restraining i the high pressure fluid 24, through seal 25, cap 26,]and

' surface 23b and shoulder 26b of cap 26. It should be FIG. 9 is a method of fabrication employing acom bined plastic seal-end closurefand preload shock'abnoted that if this end wall formed'iconfiguration isagain made circumferential after havingtlius been formed, it would have identical circumferential dimensions to that whichit had been before forming. This is a key ingredient of the success 'of this method of-retaining high sorbet with a plastic cylinder and using a metal ring for I with the crimping. V 1 FIG. 11 is a longitudinal sectio cost die for low volumeproduction.

, FIG. 12 is a section of thisdie, takenas noted on FIG. 11, and is typical of longitudinalcrirnping dies nofan alternate low FIG. 13 is an alternate method of fabrication using a four slide press, crimping by side action against the cylindcr.,

pneumatic cylinder employing the crimpcd end faces FIG. I4'isa VICWDfia double acting hydraulic or:

and standard tubing which is fabricated in the same plastic end faces and cylinder FIG. 15 is a hydraulic "or pneumatic cylinder with stamped end caps and stamped piston heads and using crimping as the end retention means.

FIG. I6 is'a pressure vessel constructed of uniform v tube sections and with the stamped end caps of FIG.'15

held. by crimping.

. FIG. '17 is a sectional view of a typical crimped end Y fitting assembly of uniform pressure tubing used to carry fluids. r

In FlG...l, I show a longitudinal sectionof'a Liquid Spring 20, or other high pressure piston type device which utilizes the-novelhigh production crimping method I have developed for the. retention of high pressure in an efficient cylinderwithcut weldment threads, tie. rods, smaprings' or other highcost assembliesrlnf 'FIG. I is shown a liquid spring 20,. having a cylinder 21,

with an integral end closure 22, and an upstanding wall pressures without wall failure at the stress pointwhcrc V forming begins and shoulder 26b engages wall 23h;

.Referringto FIG. I and 3t to'avoid critical variations 'in spring back in metals, I'preferthat cap 26, has a recess 26a, sodesigned to providca shoulder26b,pwhich' i is the fulcrum point of the'bending of the wall 23.This

controlieliminating the effect of spring back'is an important ingredient of thlSflI'll/(ifltlOIl filld amain reason for the capabilities of thisdesig'n tohold extreme pressures without fatiguefailure. This is rather obscure un- I Iessthe interrelations of the shoulder 26b; and dis closed. forming .mcthods are carefully considered; A seal entrance lead angle 23d, is'machined from the lip of cylinder 23 thisperrnits 23a to be tapered in propertion to thickness if it isdesired. In thick walled cylinders, suchasthose Liquidspringsunder very high pres sure this taper can be enhanced to provide a much thins ner wall atthe opening or tightercrim'p so that the die formed bend radius can get progressively smaller in accordance withfthe' minimum pl 2 /2 thickness/We thus can form the highestpressuife liquid springs in acco'rdance with'theseprinciples. This is an important feature of this invention. Fromeitperiments Ihave found 7 that about to inclination of the wall is best. As

noted at 261) intersection of wall 2311 approximately a 60 keying of wall 23b is accomplished. This is essen-... tially the incline of a holding thread and seems to work I best just as the same angle works best in a thread. The.

forces seem to be resolvedHwitho ut failure. over milof uniform cross section 23, which isessentially straight and uniform in every respect This is essentially a ing process in which withcrimping reduces costs of liquid springs, energy-wise below coil springs'Aliquid 24,.

is enclosed witha seal membcrZS, and a cap 26. Said seal 25, being restrained against cold. extrusion by the guide ring 27. Guide ring 27, acting as a wiper and antiextrusion member for piston'30. Piston 30 has the head 31, as shown hereinafter in FIG. 7 bearing against seal 7 closed cylinder made by cold extrusion or deep draw- I lions of cycles, when this'is accomplished this way. Ac*

7 b tually', it 'hasalways been considered in design that only one thread'holds in a threaded joint. so the success of this crimping method with'its thread-likeholding can be readily understood The obscurejreasons why this rm s ds such highpressure" is further madeapparentinFIG. 3.. r r

Ifoneobserves the longitudinal line'of'force from the 60 face formed by the edge 26b in inclined wall 23b, it will be seenthat itgoes through the center of mass 10f the crimped, stiffening bead formedbyradius 23a. This 30 incline with its resultingfldirec'tion offorce from the 60engagement. through the stiffening, plays a part in thelong fatigue life of this formed end closure.

, The angle can vary, but best rcsultsappear dictated by 25 for purposes of restraining it therewith. With the exception oftcrimpingit is similar to my low cost Spring U.S. Pat. No. 3,256,005. Referring now to FIG. 4, an end view of the configuration is shown which. illustrates how the cylindrical wall 23, is displaced by forming rather than stretching or em bossing. Said wall 23, being displaced at 2312 has essentially four small semi circles having a bent radius equal to a minimum of I /2 times the thickness ofthe upstanding wall 23. This gathering,

or radial displacementof the metal reduces the diameter of cylinder 23 at the end closure and causes an inwardly formedtapercd shoulder 23b.'torestraincap this force direction noted.

In FIG. 3 surface 23b, is bent about its centroid28,

placing fibers 28b; in compression and increasing the thickness locally. Fibers 28a, are placed in tension. It.

" should be noted thatthe stress gradient across the wall ofa cylindrical pressure vessel is high on the inner surface and low on the outer surface so that this bend makes the wall resistance greaterbecauseit prestresses the wall 23b, against the force 33, working tofail wall 7 23b. This end closure 23a-23b is fabricated by bending rather than/stretching. asin roll forming, so its stress is.

low. This aloneis not enough to hold cap 26, as it is necessary to provide the effect of a thickened end section similar tothreads. In effect this thickened gathered section provides a lever action to hold the cap 26. To

accomplish this, a small lever couple 29-29, is formed between centroid 28, and shoulder 26b, acting to cause the opening of formed wall 23a-23b from force 33. The entire mass 'of the formed stiffening

end

23a, 23b, forms a large resisting couple 30-30, resisting end opening. This is the equivalent of many threads in the old high stress cylinder construction. In effect then the thickened-stiffened section 23b, and rigidized webs 23a, act as the old thickened ends which were threaded but they are formed from uniform tubing. Further, it is well known that as you approach the central axis of a cylinder, the stress on a given wall thickness is lowered. Thus forming the cylinder inward automatically lowers its stress if the wall thickness is not reduced. Please note that roll stretch forming prestresses the wall causing it to fail in fatigue, as I have demonstrated many times. Forming without creating local stress patterns and without stretching as done here, eliminates the stress pattern that cold works and prestresses the material to early failure.

Summary:

I. The inner fibers are in compression and prestressed against movement.

2. The couple attempting to open the end closure is extremely small magnitude and the couple restraining has large magnitude.

3. This couple is of a predetermined magnitude,

when the fulcrum point about which the cap is restrained is predetermined by a relief on the cap.

4. Walls of uniform thickness moved to a lesser diameter automatically lower stress levels.

5. The line of force from the end closure engagement goes through the center of mass of the stiffening ribs.

In FIGS. 5 and 6, I show a detail enlargement of this construction, but here when using some soft alloys I have increased the metal wall at 23p. 23p is enlarged very slightly on its exterior so that the depth of the impression of the cap in this soft metal would not exceed the depth equal to the normal thickness of the wall 23. This would prevent fatigue failures in soft material such as aluminum and brass and provide for a long life. Note that the cylinder after forming has no interior enlargement permitting a piston head entry, but it has no exterior enlargement after forming so it will still fit in an efficient space envelope even though section 23p is enlarged.

In FIG. 2, I illustrate the manufacture of a Liquid Spring shock 40, which has a thin tubing wall 43, an end cap 42, and a seal retainer cap 46, construction suitable for existing vehicle shock absorbers. The advantage of this device is that of using tubing with two end caps to provide a cylinder assembly and is the procedure most widely used in all hydraulic apparatus with the exception that said thin wall tube 43, is generally restrained between two end caps held by external tie rods or at times welded. The configuration of the crimped end cap 43a-43b, is identical to that formerly employed except the spring back of the metal of tube 43, is utilized to provide a similar leverage principle of retention to that of FIG. I. The differences between the two methods of construction, will be detailed hereinafter. since the purpose of this view is to illustrate that tubing can be used and that crimping can be accomplished on either end and that only metal spring back may be utilized instead of an external recess 26a FIG. 1, 3, on the cap. This construction has an inner tapered ton head 40a, ofpiston 4], slides in the shock tube 47,

shocks are seam welded at each end, but that construction uses mild steel for costs. Here tube 43, is alloy steel but the end caps can be mild steel. These dissimilar parts could not be easily welded but can be made as shown at low automotive costs. Piston head 400, has a slight uniform clearance 470, to the inner bore 47a, of tube 47, and a liquid clearancehole 47e. Taper 47!, provides for progressively greater deflection of tube 47, as pressure increases in liquid 44, on impact, closing off clearance 47c, and thus increasing shock force. Hole 47f as it is closed off increases liquid restriction in accordance with the declining velocity of piston 41 after impact.

Now I have determined that spring back can be utilized to provide the same couple while it is not as predetermined as the cap with the relief, it is effective particularly where pressures are ofa lower nature. In FIG. 8, I" illustrate the principles used in FIG. 2 wherein the spring back of the metal provides a short couple for retention of the cap X which is restrained by the large couple T. This will only work where the metal being deformed is sufficiently elastic at high stress to provide spring back or yield. With extremely soft nonelastic material without spring back, the cap will blow out of the cylinder with ease as we have determined in our tests. In this instance or with very high liquid spring pressures the relief 26a of FIG. 7 is a must.

Referring now to FIG. 7, an enlarged fragmentary section of the construction is illustrated. The novel seal 25, differs from my US. Pat. No. 3,256,005 in that a fluid energizing groove 25a, is made with a thin trepanning tool in one operation. In addition, Lip 25b, is shorter to avoid head 31 of piston 30. Seal lip 25c, is relatively very thick and extends further into the liquid 24, and has an angle 25d, which is engaged by a similar 45 face 31b of piston head 31, producing a force component 35, when the piston 30 bottoms in shock, or to hold a preload condition. With teflon seals which tend to cold flow this carries the force to the external wall 23, and directs it generally to fulcrum point 26b, without changing the length of the assembly.

With teflon seal 25, piston 30 is preferably of a semiporous cast iron or stainless steel material to retain teflon in its porosity and cast structure, .to provide better sealing and lower friction. Bore 30s, acts to carry liquid 24, to the exposed end of piston 30, conducting heat and promoting leak free life.

Piston Head 31, has a plurality of Borda Mouthpiece bores 32, having a 50% flow coefficient at 320, and a 98% coefficient at 320. This serves to reduce shock on seal 25 and acts as a pump to cool the Liquid Spring, along with flow through holes 30f.

The guide, anti-extrusion and wiper member 27, has an enlarged section 27b, and wiper lip 27a, extending beyond cap 26.

FIG. 8 also illustrates how cylinder end 23a, of cylinder 23, was first flared out at 23f to provide a seal entrance and then crimped in after the seal 55, is inserted. It should be noted that this provides a land 23c, after spring back that functions the same as the relief 26a, in the cap 26, of FIG. 1. Flare 23f can be extended back to point 23c if desired to provide the entire relief. Seal 55, is similar to that in my US. Pat. No. 3,256,005, but

' ashock member 56, of plastic fits. betweenjlips 55b 55c, and keeps them in engagement under high speed of the'restraining..fixture 90, will hold said cylinder operations. A bore 560, adds liquid dampening on shock impact of piston 70. :A guide and anti-extrusion.

element 57,'is also used. Piston head 70 impinges on shock isolationrnember S6 and prevents seal lip surges from sudden stops as occurred with the metal retainer of US. Pat. No. 3,256,005. The thickened lip 25c of seal 25 FIG. 7, functions similarly but is one-piece.- Both seal 25 of FIG. 7 and seal 55 of FIG. 8 haveheavy interference totheir respective cylinder walls. This interference provides a tight elastic fit in thelcylinder holding fixture of FIGS. 10, l1, l2, 13, which will be discussed hereinafter, assuring a smooth crimp. In gent eral, all crimp operations need end wall stiffening at the crimp as it takes place, and the end wall closure and seal should provide this rigidity. I

In' FIG. 8 piston 70 is hollowed 704st the other end to that of FIG. 7, similar to my experiments noted hereinbefore. Actually air flowing in or out on cycling acts to cool the seal. The hollow 70a in, piston 70 can be filled with temperature conducting liquids and sealed and it is so contemplated here. a

' FIG. 9 illustrates a fragment of cylinder 60 and .seal assembly, end cap 65, including a part66, on an'extension thereof. Both cylinder wall63 and cap'seal 6 5, are

plasticand crimp 63a, and 63b, is done hot. A metal ring 70, locks at 63b, to hold plastic seal end cap 65, q V in cylinder 63. This inventor hasfiled Patents under copending patent applications Ser, No. 61 9,531 filedFeb.

27; 1967 in which'liquid springsuse a nylon cylinder such as cylinder 60, having a nylon wall53, which is even though there is no internal'pressure in the cylinder. Itshould be noted also that seal 25, generally of teflon, has a substantial interference to cylinder wall "21." Subsequently, this/diminishes; the teflon coldflows but at the time of the crimping operation this interfer'en'ce or response resistance makes possible the v crimping of the seal in place without axial movement or wall corrugation. -A simpler die 100, shown on FIG. l1 andjFlG. 12 can also be usedwithout member 85 of F162. bycooling the'Liquid Spring 20, shrinking the 7 liquid to reduce its resistance, and then crimping the 1 cylinderwith die I00; Plastic sleeve 10!, protects the utilized because of the elasticityof the wall providing."

' up to 62% of the spring energy as has been discussed in my copending applications. In this instance, a seal cap end 65, is employed to, restrain the seal, being of a similar plastic, such as Dclrin-AF which employs Tefw Ion fibers as rcinforccmc ntfor seal lubrication purposes with the high strengthof Dclrin. .Hbwevenexcept for low pressures, it is believed that the corner method.

of retention noted in FIG. 3 would not function with plastics. In this instance, I thus insertthe metal like ring '70, which acts to provide the necessary bite or engage ment with the wall 63, while simultaneously providing the simplicity of molded plastic parts.

FIG. 10 isa view of a die assemblage 80, having a female die 81, which has a pluralities of cavities 83 for forming'the upstanding cylinder portion 23, of the Li'q uid Spring 20, as the punch 81, is actuatedaxially toward the Liquid Spring cylinder portion23, In each of the four cavities 83, shown in the punch 81, in FIG. 10,

and in a related die section (FIG. 12), I gather and fold the. metal to provide the upstanding columns 23a, of

cylinderwall 23. In essence, piston 30,.seal 25; and cap 26, is held against liquid pressure 24 in the Liquid Spring by the internal holding fixture 85. It is intended that fixture 85 read pressure andlength of spring 20 so that the proper preload and overall length of the spring can be determined prior toc'rimpingnWhilethe liquid volume is measured carefully variations exceeding the plishthe permanent yieldof resilient plastic of the piston 30.

In the production'of some products, say where a piston has a large .head,,or atube fitting, itmay be re-i quired'to cause saidcrimping by a lateral motion instead ofalongitudinal motion. This then would permit the use of beaded devicesand to accomplish the re-' straint shown withoutthe necessity for axial movement.

This would alsoeliminate the necessity for a restraining .jfixture' 90,;since the application of the metal distorting forces is at right angles tothe cylinder or tube. We

therefore show: a Liquid Springassembly 20, and a four-sidedrpunch machine .110, in which a pluralityof ingproviding the crimps 23a 23b. ofa cylinder 20, is

' acceptablefor this purpose. g

' It should be further pointedout that in the use of plastic'cylinders saidpunching tools or rollers would be. heated so thatthe thermoplastic could be causedto'distort the otherwise elastic plastic and formally accom- V shapedesired. It is further contemplated that, in, the event alloys having critical cold workingproperties are failure 'lhe Liquid'Spring was cycledso thatits inter- I utilized that induction heating or heating of just the punchesior crimped endiover' atime interval might eliminate the cold working stresses for those brittle al-. loys having cold working fatigue problems. I havesuc cessfully crimped 350,000 yield maraging steel and .ob--

tained l,000,000 pulsations or reversals without fatigue nal pressure varied be tween;2,000 and 20,000 psi.

allowable tolerances can be read by force on the holding fixture 85 and crimping stopped ifthe spring is too low or high. Automatic procedures and rejection can also be incorporated. The cylinder assembly 20, is held in the cavity 91, of a restraining fixture 90, so that the crimping forces do notrcausethe corrugation or failure of the wall 23, as crimping takes place. The cavity 91,

each of'its 1 ,000,000 cycles.

I have described my inventionin connection with the product for which it was designed, that is ultra high pressure hydraulics or Liquid Springs,l will now de scribe in detail how said materialscanbe also utilized in low pressure applications such as pneumatics and hydraulics. While primarily developed for highpressure applications and fOI'MWhlChJHOJ method of mechanical crimping'has ever been found satisfactory, it is obvious that theseprinciples when applied to low pressure hy- 1 draulicand pneumatic cylinders accomplishes a corresponding reduction in cost. Thus. cost reduction lowers the cost ofhydraulie and pneumatic cylinders to of its former cost which is the cost for repairing an existing hydraulic cylinder. It isthus apparent that throwaway hydraulic cylinders are now possiblewith a reductionof 40% in the cost of said equipment.

In FIG. 14, I show a low cost hydraulic cylinder assembly 120, having a tubing cylindrical-member 121,

which is a piece of homogeneous tubing extruded or rolled and honed to the standard lengths for that tubing, that is.20 feetor more and cut to length, say 1 foot in length, as it is used in this FIG. 14. FIG. 14 illustrates in general, a low pressure pneumatic or hydraulic cylinder having an end cap 126, from which a piston rod 130, extends through a seal 125, said piston rod 130, having an enlarged head 131, thereon and a seal 132, thereon for actuating as in a customary pneumatic or hydraulic cylinder.

It should be noted that seal 125 is of teflon having a gaseous transition at 700F. so that a probable cast material such as urethane. bakelite, et cetera, could be cast around seal 125 since its pour temperature is less than teflon gaseous transition. This thus provides a east end cap with a precision seal.

Actually, since the total energy capcity of plastics is used in the process of ablation used in space re-entry vehicles to prevent destructive heat from damaging the occupants, a reverse process can be used here. Cast metal can actually be cast around a cold teflon seal, since metals having lower temperature melting would solidify and cool prior to the vaporizing of much teflon. The teflon could actually employ sacrificial upstanding ribs which, while partially or completely vaporizing would lock in. After said attachment cold flow of the teflon could be made to refill the voids where vaporizing of the sacrificial sections had taken place. Piston rod 130, has an enlargement 131, forged thereon about which the plastic piston head 1310, is cast. Ring 132 is also fixtured and cast and isa homogeneous teflon ring acting as the piston ring for said cylinder. Cap 126, which is also of cast plastic or metal construction, has a-metallic ring 126a, cast integral and a seal groove 126b, which is cast and subsequently fitted with an elastomeric seal 1260. Threads 126d, are likewise cast as is passage 126e. Ring 126a, is fixtured and cast therein also. We thus have a cylinder end closure, completely cast in a die and subsequently not machined to provide a pneumatic cylinder end 126, of the type illustrated. End cap 140, at the other extremity, has ametallic ring 126a, cast therein, a seal groove 126b, cast therein and an elastomeric seal 126e, inserted therein. A threaded porthole 141. is cast integral as is the air port 142. We thus have an air or hydraulic cylinder comprising simple homogeneous tubing and employing two die cast or plastic cast cylinder ends and a piston including a die cast or precision cast piston head. These are all low cost components. It should be obvious that the ends of this cylinder can be crimped as shown by a double ended crimping operation which is done simultaneously in a press or can be crimped one end at a time by either a punch and die or a four-sided punch. It should be noted also that on large diameters such as shown here, any number of vertical stiffeners can be formed by a punch having the appropriate number of cavities to provide the stiffening the structure indicated in accordance with my teaching that the metal is bent not stretched.

FIG. 15 shows an alternate low cost air or hydraulic cylinder 150, with tube 151, which employs metal stamped

end fittings

152, and 156, and stamped piston heads 161. Cylinder 150 is crimped in the fashion shown to provide a low cost cylinder assembly. End cap 156, has an outer stamping 156b, which retains piston seal 155, and an inner stamping 156e, nested therein spot welded at 152g and providing therebetween a cavity 156d, for elastomeric seal 156f. The nested members of 156, are threaded at 1562, to hold pipe 170. End cap 152, has similar nested stampings l52b and 152C. Stamped boss 152g, has a thread 152e, which receives a pipe 180. Seal groove 152d, has a seal 152f therein. This is asimple low cost device. Prior to crimping, cylinder 150, is rolled at 158 and 159 to hold

end caps

156 and 152 in place. We have thus illustrated in some detail our method of cylinder fabrication for all precision hydraulics and pncumatics, even though said machines and processes were first developed for high pressure Liquid Springs.

FIG. 16 illustrates a simple pressure reservoir 160, with tube 151, and two end caps 152, using these principles. A simple spacer tube 161 holds the end caps 152 in spaced relation while crimping takes place. Tube 161 can be high wear resistant in a soft tube 151.

FIG. 17 shows a tube assembly 170, using tube 171, and an end fitting 180, having a threaded attachment 181, a bore 190, and a reduced neck 182, an enlarged head 185, having a seal 183 in a groove 184. Crimp 193 holds the asembly together.

Having thus described by invention, I claim:

1. In a shock absorber having a housing, a piston means slidably disposed within said housing, seal means for said housing and piston means and end closure means associated with said piston, housing and seal means, the improvement comprising means for restraining longitudinal movement between said housing and said end closure means including a formed crimped section actingas a reinforced structure for said housing and a reduced section on said end closure means wherein the reinforced structure acts as a lever against the reduced section to prevent relative longitudinal movement of said housing and closure means.

2. The shock absorber of claim 1 wherein said reduced section on said end closure means is conical and wherein the reinforced structure acts as a lever against the reduced section to prevent relative longitudinal movement between said housing and closure means.

3. The shock absorber of claim 1 wherein said reduced section on said end closure is a stepped reduced section wherein the reinforced structure acts as a lever against the step in said reduced section to prevent relative longitudinal movement between said housing and closure means.

4. The shock absorber of claim 1 wherein said conical section has a sharp engagement edge formed thereon wherein the reinforced structure acts as a lever against the sharp engagement edge formed in said reduced section to prevent relative longitudinal movement.

5. The shock absorber of claim 1 wherein said formed crimped section for said housing is inclined between about 35 and 45 relative to the longitudinal walls of said housing and wherein said reduced section on said end closure means has a recess formed therein producing a sharp edge wherein the reinforced structure acts as a lever against the edge of the recess formed in said reduced section to prevent relative longitudinal movement.

6. The shock absorber of claim 1 wherein said formed crimped section has a bent radius about l V:

radial thread profile having a resulting line of force dir rected to the reinforced structure wherein the reinforced structure actscas a lever against radial thread profile formed in the reduced section to prevent rela: tive longitudinal movement.

8. The shock absorber of claim 1 wherein said re-;

duced section is provided with a sharp edge thereon shaped so as to substantially direct a line of force through said reinforced structure wherein therein? forced structure acts as a lever against the sharp edge of the reduced section to prevent relative longitudinal movement, a a

9. The shock absorber of claim 1 wherein said reduced section on said end closure provides a profile substantially like a screw thread and is arranged to provide'a line of force through said reinforced structure wherein the reinforced structure acts asa lever against thescrew threadlike profile of said reduced section to prevent relative longitudinal movement.

Claims

1. In a shock absorber having a housing, a piston means slidably disposed within said housing, seal means for said housing and pisTon means and end closure means associated with said piston, housing and seal means, the improvement comprising means for restraining longitudinal movement between said housing and said end closure means including a formed crimped section acting as a reinforced structure for said housing and a reduced section on said end closure means wherein the reinforced structure acts as a lever against the reduced section to prevent relative longitudinal movement of said housing and closure means.

5. The shock absorber of claim 1 wherein said formed crimped section for said housing is inclined between about 35* and 45* relative to the longitudinal walls of said housing and wherein said reduced section on said end closure means has a recess formed therein producing a sharp edge wherein the reinforced structure acts as a lever against the edge of the recess formed in said reduced section to prevent relative longitudinal movement.

6. The shock absorber of claim 1 wherein said formed crimped section has a bent radius about 1 1/2 times the thickness of the longitudinal walls for said housing and wherein said reduced section on said end closure means has a recess formed therein producing a radial thread profile wherein the reinforced structure acts as a lever against the radial thread profile formed in the reduced section to prevent longitudinal movement.

7. The shock absorber of claim 1 wherein said reduced section has a recess formed therein producing a radial thread profile having a resulting line of force directed to the reinforced structure wherein the reinforced structure acts as a lever against radial thread profile formed in the reduced section to prevent relative longitudinal movement.

8. The shock absorber of claim 1 wherein said reduced section is provided with a sharp edge thereon shaped so as to substantially direct a line of force through said reinforced structure wherein the reinforced structure acts as a lever against the sharp edge of the reduced section to prevent relative longitudinal movement.

9. The shock absorber of claim 1 wherein said reduced section on said end closure provides a profile substantially like a screw thread and is arranged to provide a line of force through said reinforced structure wherein the reinforced structure acts as a lever against the screw threadlike profile of said reduced section to prevent relative longitudinal movement.