US1085818A

US1085818A - Expansible chamber.

Info

Publication number: US1085818A
Application number: US48254209A
Authority: US
Inventors: Henry E Oxnard
Original assignee: Individual
Current assignee: Individual
Priority date: 1909-03-10
Filing date: 1909-03-10
Publication date: 1914-02-03
Anticipated expiration: 1931-02-03

Description

H. E. OX NARD. EXPANSIBLE (HI AMBER. APPLICATION FILED AUG. 29, 1 906. RENEWED MAR. 10, 1909.

Patented Feb. 3; 1914.

l V/T/VESSES 5r HAS A Tron/vs Patented Feb. 3, 1914.

2 SHEETS-SHEET 2.

H. E. OXNARD.

EXPANSIBLE OHAMBBR.

APPLIOATION FILED AUG. 29, 190B. RENEWED MAR. 10, 1909.

To'all 'whom it viayiconee;

QBe" itknown that ZIQH Y EfiOijN-ABD, of Newton, in thercount ;of. fMiddles ex and State. of Massachusetts,. ihave invented, cer tain new 1 and useful Improvements .in .Ex-

pa'nsible Chambers; {of-which the following istat: specification.

- --='-I-his invention 5 relates eto improvements iiitexpansible chambers. ';Mor-e particularly, it; is'here describedas it may be applied to 5,; pneumatic springs or cushions intended to vention seeks which is to be used, is

sustain a weight elastically, or to "act as a huflerll'for receiving any;for.ce; but; it is applicable to a wide variety of other uses" -It is among the purposes contained at highpspreslsures, having a plunger reciprocating inward and outward without leakage and almost without fricti I. "As applied to a pneumatic spring the into provide wide limits for the range of travel between the expanded and the compressed positions of the spring; an easy and freely responsive action of the spring, with a minimum of wear, resulting from the elimination of friction; and great strength, resulting from vthe capability of containing air at exceedingly high pressures without leakage or rupture.

It is also the purpose of the invention to provide apparatus having the other advantages which pertain to the structure hereinafter described, too manifold and diverse to be specifically enumerated here.

According to this invention, a highly .flexible septum, iinperyious to the fluid arranged as a sleeve closely incasing a cylindrical plunger. At' one end it is attached to the plunger. The

other end is everted or rolled back upon itself-and attached to the interior of a cylinder which closely incases both plunger and sleeve. Measured radially, the space between the plunger and cylinder is about the double thickness of the septum. In opera tion, as the plunger travels to and fro in the cylinder, the fold at which the sleeve is doubled back upon itself rolls to and fro to different parts of the sleeve, corresponding to the motion of the plunger. The air or other fluid enters between thep'lunger and cylinder, forces one part of the sleeve smoothly against the plunger and the remainder smoothly against the cylinder, and

thus separates the adjacent surfaces of thespec ification of Letters Patent.

of the .invention to provide a chamber 'in .which fluid maybe of an elastic bag.

PATENT orrion.

imam-t; ogre-nan, or nnw'ron, mnssacmssnr'rss Patented Feb. a, 1914..

double'd' sleeve slightly f'nom' each other and fills the intervening space with a thin film of the fluid; This eliminates all friction except that incidental to guiding the plunger in its travel, and the internal friction of bending-- the septum at its fold, both which are Slight as to be negligible.

The fluid pressure upon the septum is sustained; ultimately, by'the cylindrical Walls of the plunger, ward; and the walls of the cylinder, upon which it actsradially outward; and by the septum at the fold, which is the only place Where there' is any pressure tending to stretch or rend the septum. The stress at that point depends upon the annular or radial thickness of the film of fluid. As the latter may be, very slight, and may under some circumstances be almost infinitesimal, the septum is' well ableto sustainit and is not liable to rupture, even under great intensity of pressure. Hitherto, several for "confining a fluid under" pressure in an expansible' chamber, among which are; (1) sliding contact of a piston within a cylinder (either'the piston or its packing sliding in such close contact with the cylinder that no fluid can pass) (2) the use of a transverse diaphragm; (3) forming the chamber The present invention Works upon a different principle and com prises an arrangement which is novel in several respects. It differs from the first in that neitherpiston nor packing makes slid ing contact with the cylinder. It difiers from the second andthird in that its flexible septum is highly flexible; and is arranged in a form redoubled upon itself and is, speaking generally, not subjected to a serious tensile stress by pressure of the fluid; and in that its travel or limit of expansion is not limited by the strength of material, but may be as long as the travel of a simple piston sliding within a cylinder. It also differs in that the pressure is not applied to any considerable area of the septum in the direction of travel, producing no stretching effect in that direction, no great stress upon its' fastenings and requiring no relatively great strength in the septum.

The invention also comprises improvements in septa, in the method of fastening the same, in the arrangement of an auxiliary upon which it acts radially in-.

methods have been used "ger through a given distance In the .aeeompang drawings, which illustrate one emboent of the invention, Figure 1 represents a longitudinal section through an air spring. Fig. 2 represents the same diagrammatically on a smaller scale, showin the extreme positions of the plunger. Figs. 3, 4 and 5 show successive stages in forming or molding the sleeve and assembling the same into position. Fig. 6 shows an alternative method of fastening the sleeve. Fig. 7 is an enlargement of the fastening shown in Fig. 1. Fig. 8 shows a form of the septum arranged for separate transportation. Fig. 9 shows an alternative method of guiding the plunger.

Referring to the drawings, 1 is a plunger, preferably of brass or steel, working in a cylinder 2 closed at one end by a head 3 and preferably closed-at the other end by a head 4 through which the plunger rod 5 passes; The plunger is guided and maintained in a position approximately central within the cylinder 2 by thebearing of the plunger rod 5 where it passes through head 4, and by the bearing of a flange 6 on the plunger against the interior of the cylinder. The plunger may be guided in any other suitable way, one form being indicatedin Fig. 9, in which a flange 6' attached to the inner end 'ofthe plunger spreads outward to the cylinder walls. Thefiange 6 makes a loose sliding contact with the cylinder walls without attempt to be'tight against the passage of fluid. A highly flexible sleeve septum 7 is attac ed to the inner end of the plunger 1; lies loose along the surface of the plunger for a variable distance; and is turned back u on itself and lies loose along the inner su ace of the cylinder to which it is fastened at 8. This sleeve and its con struction and fastening are important features of the invention. The lower portion 9 oi the cylinder which is to contain the fluid under high pressure is thus bounded by the head 3 and the septum 7. An opening 10, having an automatic check'valve 11, permits the introduction and impounding of.

air or other fluid under pressure at pleasure. Depression of the plunger, fore it farther into the cylinder, decreases thevo ume within, thus increasing the intensity of pressure and resisting the force which is depressing the plunger. While the diameter of the upper portion of the cylinder bearsa close relation to that of the plunger, the lower portion may be of larger diameter, and. when so constructed movement of the ploduces less proportionate 'efiect, and by &is means I contrive a safety device to prevent theapplication of too great pressure to the sep-- tum; and at thesame time I shorten or condense-the apparatus. To accomplish this I arrange the sleeve 7 of such length that the plunger may travel between. the heads eaters 3 and l, each serving as the final limit of its movement, and the proportion of contents when the plunger is raised to that when depressed is so designed that the ratio of the space surrounding the plunger when depressed to the total contents when raised shall be inversely in proportion of the desired maximum ressure to the desired minimum pressure oi contents. -When.the plunger is depressed, thus reaching the desired maximum of pressure it rests u on the head or bottom 3 of the cylinder, an no application of pressure to the plunger can increase the pressure upon the fluidvor sleeve. By thus enlarging the cylinder around the depressed position of the plunger I also shorten t e apparatus, it my well understood that a residuum of space must be left to contain the fluid in its compressed condition, and that the ordinary method of accomplishing. this is to make .the cylinder longer than the intended travel of the plunger,

In constructing the sleeve septum any suitable material may be used capable of y producing imperviousness to the Hand under high pressure; and flem'bility in a very high degree with'some elasticity, so that it can be turned partly inside out, without injury, and repeatedly rolled back and forth in. thls position .as herein described, with little wear. There must also be a strength or ii a 1| of texture, which while allowing the slight amount of stretching necessary to turn the sleeve inside out, at the same time prevents any considerable stretching of the fabric. No fabric or membrane hitherto hown td me is entirely suitable for this purpose, so far as my experiments have gone; but I have found that a suitable fabric can be m manufactured by a combination of leather Y and rubber, in which the exte surface of the fabric on each side is a piece of flem ble leather, and there is a film or layer of flexi-, ble rubber intervening, the. whole be:| cemented firmly together so that it has the properties of one'integral mass, acting as a; unit, without looseness or hiction t the layers. Two thicknesses of fiem ble leather cementedtofiether can be de te 115 work, but not as we Rubber alone is unsuitable. In an cting the sleeve Iuse a form or mold, as shown in the Fig. 3, having the same external diameter as the plunger upon which the sheve is to fit. The r mold is preferably, but not necessaril somewhat ring at one end 18, and slight y tape' at the; other end 17. A layer of flexible leather is first wound thereon in single thiclmess, with its edgesbeveled, overa 1.1m lapping and cemented ther, so that the entire layer is ofuniform thieess. The layer lies a little upon the flaring portion 18, and a little upon the tapered portion 17.. A layer of rubber is next applied, eompley 1 cemented to the leather, and its edges-joined in like manner. Another layer of leather is then applied outside the rubber and firmly cemented thereto. When the 'whole has been dried and removed from the form, the part which was opposite 18 contracts into substantially the same cylindrical shape as the rest of the sleeve; but owing to the flaring character of the surface on which it Was formed it can be more readily stretched outward for fastetning to the cylinder. The sleeve may then be mounted on the plunger or a form like the plunger, as in Fig. 4, where it will be observed that in its normal form the sleeve is an open ended cylinder of uniform diameter throughout its length,

. fitting snugly the surface of the plunger.

The next stage is to evert or turn back upon itself the end-18 ready for fastening to the cylinder. The fastening of the inner end of the sleeve .to the plunger may be accomplished in any suitable way. The preferred method is to affix to the plunger a tapering; cap 21 of wood having a'series of steps or corrugations 19, as clearly shown in Fig. 1, to the conical exterior of which the sleeve is fastened by shellac. The pressure of the fluid seats this firmly upon the cap, automatically sealing the joint; but if desired a rubber cap 20 may be applied and cemented over the cylindrical end, as in'Fig. 1. The plunger may then be inserted in the cylinderand the other end of the sleeve attached thereto. Any suitable method of attachment may he used; but I have devised a method having peculiar advantages, which is illustrated "in the drawings. The end of the sleeve is turned or stretched outward and clamped betweenthe two portions of the cylinder. The face of the lower clamping portion has a broad groove 22, having a series of minor grooves 23 cut in its bottom.

A soft rubber ring or washer 24 is pressed into groove 22, and the minor grooves may be'partly filled with red lead, if desired. When the parts are compressed the rubber 24 is bent sharply around the corners of the minor grooves, thus constituting a series of tight inclosing rings, and the pressure of the inclosed fluid tends further to force the rubber into the corrugations, compressing the air contained therein, if any,land tightening the joint. A metal washer 25'occupies a corresponding place on the other part of the cylinder, the portions being screwed together at 29, and the sleeve is inserted between-the rubber 24 and metal 25, as clearly shown in Fig. 7, being separated from each by

leather Washers

27, 28. The sleeve may be prepared for this on a suitable form, in which the washer 27 is firmly cemented to the outer leather of the septum, thewasher 28 to the inner leather layer of the septum, and a rubber connector 30 is cemented to the inner side of the rubber layer of the septum, as shownin Fig. 7, whence it is bent around and embraces elastically the inner leather layer of the septum and the leather washer 28. In this form the sleeve end will retain permanently its expanded shape ready for use at any time, upon which occasion it is, expected that the under side of the rubber connector 30 will be firmly cementedto the rubber washer 24. The other end of the sleeve being attached only to the wood cap 21, which is detachable from the plunger upon removing screws-31, the entire sleeve may-readily he put in place or re moved. This permits a number of sleeves to be carried in. duplicate, and one readily substituted for another in case of rupture, the joint between the rubber connector 30 andtherubber washer 24 being readily separable and renewable, as is the custom with rubber cement.

Another feature of the invention relates to the upper portion of the cylinder, which as represented in Fig. 1 contains a passage having a check valve 12 and a small passage 13, which is permanently open. Packing 14 is inserted to lubricate-the stem of the plunger and prevent undue leakage of air. The weight which the spring is to carry is applied to the top 15 of the plunger rod. The shape of this top and the method of connecting it to the plunger stem, Whether integrally or by a universal joint or otherwise, depends upon the use to which the apparatus is put. Hence, it is deemed suflicient to show a simple head 15 in the draw-. ing. Depression of a spring by a momentary shock, to which vehicle-springs are peculiarly liable, ordinarily results in a succession of vibrations of diminishing intensity. By the present invention these may be eliminated or modified as follows: When the plunger 6 is depressed air is drawn into the :closed portion 16 through automatic valve 12. When the lunger rises on the rebound that valve closes, imprisoning the air and 'thusfretarding'the rise of the plunger. The

small hole 13 allows the air thus imprisoned to escape gradually, the plunger resuming its normal position slowly.

In operation, let 'it be assumed that the lower portion -9 of the cylinder contains air at a pressure of 200 pounds per square inch, which pressure a sleeve septum, built as described, will readily sustain. Ifthe diameter of the plunger and its incasing sleeve be 3 inches the upward pressure thereon will be approximately 1400 pounds, which is the externalweight sustainable at the head 15. When an excess force is applied the plunger will sink, compressing the air beneath it until the excess pressure is balanced. The plunger moves in a free, resilient'inanner,

falling and risingeasily with the changes of weight.

the sleeve while inthe process of construe Although the everted portion of cumferen'ce around'the plunger, and this be ,tion hugs tightly the portion it is turned back upon, yet when put'in place in the apparatus and subjected. to high pressure air enters between the plunger ortion of the sleeveand itsadjacent everte cylinder. or-.

tion, separating these two portions and orcing each of them firmly upon the adjacentsupporting surface of the plunger or cylinder, asthe case may be. This prevents all friction between the adjacent surfaces of the everbed septum. It also revents all stretching of those portions 0 the septum which lie against either the plunger or the cylinder, because the pressure thereagainst holds them firmly together, and the stretching, which might be expected from the pressure of the fluid upon the fold in the axial direction, is not sufiicient to overcome the friction. The result is that the septum is not under tension anywhere except at the fold,

and there the part which is exposed is-so' closely supported on either hand that it can. withstand a very high pressure. Assuming 1 that the pressure. is 200 pounds per square inch, and the thickness of the air film at the fold is j inch, the pressure tending to expand or burst the septum at the fold would 'e about 12% pounds per linear inch of ciring divided equally between the outer and the inner limbs of the septum would make a tension on the septum of 6;} pounds per inch. This is manifestly very small compared with the 11400p0unds weight supported thereby. It can be made smaller still by providing a smaller distance between the folded portions of the' septum, thus narrowing the unsupported portion of the septum;

or by increasing the diameter of the plunger, thus-taking advantage of the fact that the area increases numerically faster than the circumference. When thus constructed there is no leakage of the air contained,'despite the high pressure, and the high friction manifest when a sliding tight fitting piston is used to contain so reat pressure isnot evident. There. is, in act, no friction except that of the plunger against its guides,

-which may be lubricated as much as desired, and theinternal friction of the septum as its fold rolls backward or forward, which is so slight as to be negligible. No means is known to me by which so great pressure could 'be sustained in an operative manner by a jflexiblediaphragm set transversely to the direction of travel, after the manner hitherto practised, nor by a rubber bag, aslin both cases the material is exposed to a large bursting stress and the material must either be so strong and thick as'to lose its flm'-' bility, or must be so reduced in size as to have an exceedingly limited'travel. "In the present invention thedistance between the safe limits of travel of the plunger is wholly independent of the strength of material aoaaaia composing the septum. llt'will be readily understood that it is important to rovide mechanical stops at predetermined limits to prevent any strain except the pressure of the fluid from actin upon the septum; but with this exception t e sleeve may be made as many inches or feetin length as desired. Each additional inch of length adds two inches to the travel: one inch in the outward direction and one inch in the inward direction, assuming that the stops for limiting the motion of the plunger are adjusted accordingly? In some cases it is not necessary to employ a septum which is absolutely tight,

provided it leaks air but slowly, as con-,

venient means are sometimes at hand for replenishing the leakage. Thus, a supply reservoir may be carried on an automobile, railway car or other vehicle to which the spring is attached; or apump may be attached. In Fig. 1 a tube 32 is represented which may lead to such reservoir, not shown .in the drawings, which supplies air whenever the pressurem the cylinder 9 is-less than in such reservoir, thus permitting the .valve 11 to open automatically.

An alternative method of fastening .the sleeve to the cylinder is indicated in Fig. 6, in which each portion of the cylinder has a flange 26, there being a rubber washer 24,

corrugations 23 and a groove 22, as before.

pressure of the sides of the septum against their adjacent walls, this strain does not have-to be borne by the fastenings of the ends of the septum, thus reducing the likeseptuni at its fold be held entirely by the lihoodof wear and breakage at those points.

As showing one methodof mounting the spring, the head 15 is represented as rovided with a'hole 33 through which a olt or'pivot may pass, and another eye 34 at the bottom or holding a bolt 35 at rightangles to the top pivot is represented, thus obtaining by this method of mounting the effect of auniversal joint'jvithout actually adding 'a-separate element to the mechanism for that purpose.

Many other variations may be made fromthe particular form and arrangement'here shown, without departing from the scope of the invention.

I claim:

1. The combination of a round casing and a plunger therein with a highly flexible everted sleeve joining them, the adjacent parts of the everted septum being close to each other radially, the said plunger having a flange 6 bearing against the casing, forming a guide protecting the adjacent septum parts from mutual contact.

2. The combination of a round casing and a plunger therein with a highly flexible everted sleeve septum joining them, the adjacent parts of the everted septum being close to'each other radially, the said plunger having a flange 6 bearing against the casing, the adjacent end of the-casing being closed, and there being a stem of the plunger passing through said closed end and having a bearing therein, cotiperating with said flange in guiding said plunger within the casing.

3. The combination of a round casing and a plunger therein with a highly flexible everted sleeve septum rolling between the plunger and the casing surfaces, the sleevesupporting partof the casing bearing a close relation to the diameter of the plunger,

and the non-sleeve-supporting part of the casing occupied by the plunger when the sleeve is on the plunger. bearing a relation not close thereto. l

4. The combination of a round casing and a plunger therein with a highly flexible everted sleeve septum joining them and supported thereby, the junction of the septum with its support being on a surface inclined conically to the axis there being at said junction a series of corrugations transverse to the direction of tension of the septum on the junction.

5. The combination of a round casing and a plunger therein with a highly flexibleeverted sleeve septum joining them, and fastening means for the end ofthe septum wherein a part of the support is formed at an inclination to the adjacent surface supporting the septum, vsaid inclined surface having a series of corrugations transverse to the direction oftension of the septum on such fastening.

6. The combination of a round casing and a. plunger therein with a, highly flexible everted sleeve septum joining them, and fastening means for the end of the septum wherein a surface, formed on the body to which the septum is to be attached, has a series of corrugations transverse to the direction of tension, there being means to press the. ridges of said corrugations into the septum end.

7. The combination of a round casing and a plunger therein with a highly flexible everted sleeve septum j oining them, and fas tening means for the end of the septum, wherein is a surface adapted by friction or the like to oppose movement of the septum in the direction of the axis; the septum thereon being exposed to the fluid pressure of the contents of the casing, whereby the septum is frictio-nally held at said surface.

SQA highly flexible septum arranged in everted sleeve form and attached at one end to a cap attachable to a plunger and attached at the other end to a ring attachable v to a round casing, the whole adapted to be used in apparatus of the class described.

9. A highly flexible septum arranged in everted sleeve form and attached at one end to a disk attachable to a plunger and at the other end to a disk attachable to'a round casing, the whole adapted to be used in apparatus of the class described.

10. The combination ofa flexible everted sleeve comprising two layers of supporting material and one of rubber intervening with a contiguous continuation of the rubber 12. The combination with an expans'ible chamber of a flexible everted sleeve septum having a layer of rubber and a layer of supporting material; and fastening means for the end of the septum, wherein a rubber pad is provided, adapted to make an impervious joint with the chamber .wall, there being a connection ofcontiguous rubber be-- tween said rubber of the septum and rubber of the pad. v

13. The combination of a round casing and a metallic plunger within it with an everted flexible sleeve septum joining the two, the'plunger having a cap of different material for adhesion of the septum thereto.

14. The combination of a round casing and a metallic plunger within it with an everted flexible sleeve septum joining them, the plunger having a cap of diflerent'material to the sides of which cap the septum adheres.

15. A composite septum. comprising the combinat-ion'of a sheet of highly flexible strain-resisting material, combined with a sheet of highly flexible impervious material lining it, the two being arranged together in the form of an evertedcylindrical sleeve, with the impervious lining on the interior.

16. A composite septum, having a sheet of highly flexible elastic material combined with a sheet of highly flexible supporting material and adapted to be everted surrounding a plunger and surrounded by a cast by there 'is no superficial slip of one upon lit ing and to roll from one to the other, all contiguous parts of the two sheets of material which are subject to the eversion and rolling being adheslve to each other, Where;

the other.

17. A composite septum, having a sheet of highly flexible elastic material combined with a sheet of highly flexible and somewhat expansible sup orting material and. adapted to be everte surrounding a plunger, and surrounded by a casing, and to roll rom one to'the other; all contiguous parts of the two sheets of material which are subject to the aversion and rolling being adhesive to each other, whereby the supporting material is expanded and contracted by the elastic material; the said supporting material being a fabric continuous in all directions and having its ex ansibility limited in all directions 3 where y expansion of the elastic material by penetration through interstices of the supporting material is prevented.

18. A'highly flexible septum, composed of two layers of leather and one of rubber intervenlng, all closely united together in the form of a sleeveysald sleeve bem impervious, adapted to roll evertibl etween a plunger and a casing surrounding the plunger, and to fit both anger and easing when so rolled.

19. In an cxpansible chamber, the combifor joining the septum to the'adjacent chamber wall.

20. In an expansi'ble chamber, the combination of a casing, a. plunger and an impervious, everted sleeve septum within the easing, and a mass of soft surfaced impervious material contiguous to the se tum; and means to hold said mass in p ace on the chamber wall.

21. The combination with a round casing and a plunger therein, capable of holding very high internal pressure, of a non-elastic highly flexible fabric arranged in the form a s e plunger, and having a texture of interlaced fibers rigidly resistant to separati n from .each other in any direction; and a i 'hly flexible film, impervious to air, supporte on eve between them, evertible, expansi- I 'ble and cont-ra'ctible tofit either casing or comprising a septum whose adjacent sur-' faces when everted are close together ra: dially whereby walls composed ofsaid casing plunger; and segtum may carry very high pressures excee ing the normal leaka e or bursting stress of both components o the septum.

In testimony whereof I have afiixed my signature, in presenceof two witnesses.

HENRY E. OXNARD.

Witnesses:

Evnna'rr E; KENT, @mvaa 1P. Sonoonmaxaa'.