US2008291A - Method of controlling oscillations of springs - Google Patents

Description

July 16, 1935. J NALLE 2,008,291

METHOD OF CONTROLLING OSCILLATIONS OF SPRINGS Original Filed April 5, 1929 3 Sheets-Sheet l ji gj a /Z a 29 & Z4 74 AP 59 23 5/ INVENTOR.

TTORNEY July 16 1935. J. M. NALLE 2,008,291 l METHOD QF CONTROLLING OSCILLATIONS 0F SPRINGS Original Filed April 5, 1929 s Sheets-Sheet 2 A 4 45 yd! T lliw 1111111)) -t'- U 56 40 JNVENTOR.

56 J6 D Jo w/i A4445 BY n ATTORNEY July 11%, 11935, J, NALLE 2,008,291

METHOD OF CONTROLLING OSCILLATIONS OF SPRINGS Original Filed April 5, 1929 3 Sheets-Sheet 5 IN V EN TOR.

A TTORNEY.

Patented July 16, 1935 METHOD or CONTROLLING osonm'rlons or SPRINGS,

John M. Nalle, Hollywood, Calif;, assignor to American Chain Company, Inc., a corporation of New York Original application April 5, 1929, Serial No.

Divided and this application February 6, 1932, Serial No. 591,263

12 Claims. (01. 188-88) This. application is a division of my copending application on Shock absorbers, Serial N 0. 352,634, filed April 5,.1929.

My invention, relates to improvements in methods of controlling oscillations of springs, such as the body-supporting springs of vehicles, and is particularly, although not exclusively, adapted for use on motor vehicles.

Heretofore, efforts have. been directed to overcoming the discomforts of travel over humps and hollowsof considerable magnitude, but little attention has'been paid to the effect of lesser unevennesses'of the road. A car driven over an average city street at average speed is constantly "see-sawed, by the slight elevations and depressions that aretraversed. As the front of the vehicle rides over an obstruction or drops into a depression, thevehicle bodyoscillates about its instantaneous center of oscillation and, by the time the rear wheels reach the uneveness in the road, the rearsprings are already partly compressed or expanded, as the case may be, so that thereis'an increased throw of the rear end of the vehicle. This see-sawing action is. particularly marked when traveling at moderate speeds and reaches'its maximum when the speed of a car of given wheel base bears a certain relation to the natural period of oscillation of the car springs. The see-sawing movements of a car may be small but because of their frequency probably contrib ute, in the aggregate, as much discomfort as the more marked but comparatively less frequent big bumps encountered.

This see-sawing action may be reduced by snubbing the small movements of the springs, or,'in other" words, by resisting spring movements at the so-called free center. I have found that this is best done by damping the spring both on the up stroke and the down stroke. The degree of snubbing, however, should be but a fractional part of that required for'large bumps. Snubbing required to reduce see-sawing, when applied on" both the compression and the expansion strokes of the springs, does not stiffen the sprlngs to an extent noticeable to the occupants of the vehicle. In order to reduce the see-sawing action of the vehicle to the same extent, by snubbing in one direction only, it would be necessary to employ substantially double the magnitude of snubbing' required if applied in both directions. If this double amount of snubbing is applied on the compression stroke of the spring it will have a perceptible spring stiffening efiect. If, on the other hand, it is applied on the expansion stroke of the spring," it will tend to pumpftthe body down with the spring. By pumping I mean the pulling down of the vehicle body by a series of bumps when the expansion stroke is so protracted that the spring cannot fully recover from one compression before it is recompressed by the next bump.

When larger bumps are encountered, proportionately more snubbing is needed to keep the verticalacceleration of the vehicle body or frame from exceeding certain limits, I find it desirable, therefore, to employ a certain amount of resistance to compression of the spring on its initial movement away from normal, increasing. the snubbing after the spring has moved through a small range, andfinally sharply increasing the snubbing as the spring movement nears the limit of its range, so as to-prevent the axle from sharplyjstriking the frame of the vehicle. The same is true of the expansion stroke, except that instead of preventing theframe from striking the axle at the extreme movements of the spring, a sharp increase of snubbing serves to prevent such distortion ofthe spring as may cause it to break.

I .It is, therefore, an object of my invention to provide for thejcontrol of small and large oscillations of a spring. on movements away from normal as well as toward normal.

Another object of my invention is to reduce the see-sawing of a vehicle body when the vehicle passes at moderate speed over comparatively small unevennesses in the road.

Another object of my invention is to provide for snubbing a spring at the end of its compres-' sion stroke, to prevent the axle of the vehicle from sharply striking the vehicle frame.

Another object of my invention is to prevent excessive. flexureof a spring in either direction away from normal. 7 7

Other objects of' my invention will, in some cases, bereadily apparent and in others will be pointed out specifically in the following description of a shockabsorber embodying my invention, while the novelty'and scope of the invention will thereafter be pointed out in the claims. In tlie'accompanying drawings; Figure 1 is a side view showingthe hydraulic shock absorber applied to a portion of a vehicle; .Fig..2.is a view'of the shock absorber in longitudinal section, the section being taken on the line'2'- 2 ofFig.,4;

2a isia fragmental view in longitudinal sectionfshowing a "modification of the shock absorber; f I

Fig. 3 is aview in longitudinal section taken on som 7 lif s-T Fig. 4 is a view in transverse section taken on the 1ine'44 of Fig. 2;

Fig. is an end view of a piston used in my shock absorber, looking in the direction of the arrows 55 of Fig.2;

Fig. 6 is a similar view looking in the direction of the arrows 6-6 of Fig. 2;

Fig.7 is a view'of the piston in longitudinal section, the section being taken on the line 1- 1 10} 1 v.

thereon. Above this cylinder the body is formed with a chamber I3 which communicates with the is fiattened'at the top, intermediate its ends,

to form a recess 2| communicating with the chamber I3, and a similar recess 22 is formed in the under side of the piston. Extending vertically through the piston from the recess 2 I ,tolthe recess 22, is a slot 23 of rectangular form. This slot is adapted to'receive a shoe 24' formed with 'an arcuate socket 26 running transversely therethrough and of somewhat. more than 180 in extent. This socket is adapted toreceive a cylindrical knob 21, formed on the end of a crank arm 28. The crank arm is'keyed to a shaft 29 which is iournaled in bearings 30 and 3| in the body I0 andextends through thechamber' I3, in a plane transverse to the cylinder I I. 7

As shown in Fig. 4, the shaft 29 projects from the side of the casing II], and a stuffing box 32 of suitable form is providedtoprevent leakage of oil through the bearing 3i and out of the body III. The projecting end of the shaft 29 has keyed thereon a crank arm 35 (Fig. 1), the, outer end of which is connected by a rod 36 to'a stud 31, or other suitable device secured to the axle 38fof the vehicle. The axle, of course, is connected to one of the main springs 39 of the vehicle. The body iii of the shock absorber is providedwith pads,

tions above described. In other words, movement of the spring will cause the" shaftifl to rotate, oscillating the crank 28 andthus causing movement of the piston 20. V g I As the crank arm 28' oscillates, 131165110624 will move up and-down within" the slot 23. It

will be noted that, because the socket 25 has an angular extent of more than 180, it will cling to the knob 21 and will rise andfall with the oscillation of said knob. In order "tq prevent trapping orpumping of oil by, the riseandi fall of the shoe the piston is iormedwith ducts Ma and 2H) connecting the recesses 2|" and 22. The

shock absorber comprises a main body IO formed with a hollow cylinder portion II which}- is closed at each end by means of caps I2 screwed lower end of the knob 21 is flattened, as'indicated at'43, leaving a slight space for oil, which serves to lubricate the bearing of the knob in the socket 26. In assembling the parts, the shoe 24 is applied to the knob by, slidingit transversely thereon, after which the crank 28 with the shoe connected thereto may be inserted in the slot 23. As shown in Figs. 1 and 4 the shaft '29 has an indicator arm 35a secured thereon which, .by its 'positionwith respect to a pin [Ila on the casing I0, indicates whether the plunger 201s centered in thecylinder. The rod 36 has socket ,members 36d and 36b at opposite ends thereof to which it is connected by right and left hand threads so that by turning the rod in said socket 1 members the arm 35 may be adjusted with respect to the axle until, with the vehicle under normal load, the piston cylinder II.

-As shown inFigs 3 and 4, the cylinder I I ,is formed with a seat "44 at one side to receive a throttle bar 45." The latter extends practically the full length of the cylinder and is secured 26 will be centered in the to the'seat 44 by means of screws, as shown.-

The outer face of the throttle bar is formed with a pair of shallow V-shaped notches 46 and 41 respectively. The piston 20 is formed with a slot 48 to receive the throttle bar. The slot 48 is deepened at twopointsto form recesses 49 and 50 which are separated by a central wall 5|. The recess 49,, as best shown' 'in Fig. 7, communicatesfwith a. duct 52 running to theleft hand.

end of the piston, while the recess 50 connected by a similarduct 53 running to the right hand end of the" piston. The outer ends of these ducts springs and are centered thereby. The outer ends of the springs are anchored to the piston by means of pins 55a and 51a respectively. The recesses 49 and 5D aresep'arated'from the ends of the piston by walls 58 and 59 respectively,

which are preferably reduced in thickness by notches 60 and 6I respective1y,-.cut in the ends of the piston. r r g On. the side opposite the slot 48, the piston is formed with a duct 62 extending from end to end of the piston. This duct iscentrally contracted to form an annular valve seat 63in which a valve 64 is fitted to-slide. A valve 64is normally held in central position by opposed compression springs 65a and 651). These springs fit upon stems 64a and 64b projecting from opposite. endsof the valve 64; The springs bear at one end against the body of the valve and are secured to the piston at their'opposite ends by means of pins 86a and 661 respectively. The body of the valve 64 is conically tapered to a, smaller diameter at each side ofits central transverse plane, so as to graduate the size'of the opening, formed as the valve moves off its seat in either direction. The duct 62 provides communication between chambers Ila and III) and the valve 64 will open. to permit exchangeof fluid between these chambers when the, pressure Ialso employ a cushion device at one end or the piston which comprises a spring pressed cushion plunger 61. This plunger and an op posed plunger 68 are fitted to slide in a bore 69 formed in the piston; The bore extends from the right 'hand face of the piston, as shown in Figs. '2 and 3, to'the slot 23 in which slides the shoe 24'. The plungersBl and 68 are preferably cup-shaped, with their concave faces directed inwardly' to receive "acompression spring III.- This spring presses'the" cushion plunger 61 against a strap It so that it lics flush with the end of the piston? At the same time the plunger 68 is pressed against the shoe and serves to take up any slack betwee'nsaid shoe and the slot 23, thus overcoming any tendency for the shoe to knock as itreciprocates inthe piston. It will be observed from Fig. 2 that the bore 69 is travowed by the duct 2la so that the oil in" the supply chamber may enter said bore and lubricate the plungers 61 and 68, and at the same time there will be no danger of trappingoil in the bore, The purpose of the cushion plunger will be explained hereinafter.

The oil in the chamber l3-is maintained at atmospheric pressure, but considerable pressure is developed in the working chambers Ila and llb, hence there is a tendency for oil to leak .from said chambers past the piston into the supply chamber l3. In order to keep the working chambers Ila and I lb filledwith oil at all times, ports 12 and l3 are provided which lead from the recess 22 into said chambers respectively. Theseports are furnished with check-valves Hand 15 respectively, opening toward ing chambers lla and llb.

The operation of the shock'absorber'will now be explained and in this connection it should be noted'that the term fcompression stroke as used herein, when applied to the spring or axle, denotes the. whole upward movement of the spring oraxle, whether above; below or through normal, while the term expansion stroke denotes the corresponding downward movement. These terms should not be confused with the compression and expansion produced by thepistonwhich the worktakes placein one working chamber or the other,

on movement of the piston in either direction.

In Figs. 1, 2, and 3,'theshock absorber is shown in normal position, the piston beingcentrally located in the" cylinder.' 'When the vehicle strikes an obstruct-ion the axle 38 is raised with respect to the vehicle body, compressing the vehicle spring 33, lifting the crank arm 35, and causing the piston 20 to move toward the right, as'shown in Figs; 2 and 3. As aresult of this movement the working chamber lla iscontracted and the working chamber '1 lb correspondingly expanded, so that the oil which fills the chamber lla is forcedout of said chamber into the chamber l lb. Thereare two; avenues for the escape of oil from the 'chamberllainto the chamber llb. In one case the oil passes through the notch 46 under the wall 58 into the recess 49 and thence through the du'ct52 past'the valve '54 to the chamber llb. The other avenueoi escape is the -duct62 which is restricted by the-fvalv'e 64,and the springs 65a, and 652) which control the valve 64 are suflicient- 1y powerful to prevent oil from passing through the duct 52 until considerable pressure hasbeen developed in the chamber! la. a I r In addition to the actual'escape of oil through the two avenues above defined, there is an opportunity for part of the oil tobe temporarily resiliently displaced by comp'r'ession of the plunger 61 against the spring 10, but'it will be understood that this oil isnot lost to the working chamber l I a but is restored thereto as soon as the pressure in the chamber drops sufiicientl'y for the spring 10 to expand and force the plunger 67 outward against the strap H. The spring 19 is very light and offers comparativelyiittie" resistance to compression, so that the resilient displacement of oil may 'take place even on small piston movements producing very little compression in the chamber l la,

We may now follow the course of the oil from chamber ll a to chamber 'l lb, upon movement of the piston into chamber I la. It will be observed that the effective orifice formed between the wall 58 and the notch 4%? will at firstslightly expand until'the wall is centered over the notch and then will gradually close as the outer edge of the wall 53 approaches the outer inclined face of the notch 46. Eventually, the by-pass through the notch 46 will be closed elf completely and thereafter further displacement of oil will have to take place through the duct 82. However, the passage: of oil by way of' notch 46 is throttled notonly by the movement of the wall 53 with respect to the notch 45, but alsoby thevalve 54 which is pressed against its seat by the spring 56. The strength of the spring 55 is carefully chosen to yield to predetermined dilierential pressures developed between chambers Ho and l lb, and 'the tapered body 54aprovides a predetermined control which extends through a, considerable travel of the valve 54. This form of valve not only prevents chattering which would be likely to occur if an ordinary ball check valve were used, but it also aiIords another means of controlling the resistance offered to the movement of the main spring 39, for the taper of the valve body may be varied to provide a predetermined pressure curve in the chamber I lot. It will be'observedjtherefore, that I have provided in my improved shock absorber a control depending upon the position of the piston in the cylinder, and another control dependent upon the pressure, developed by the piston in the working chamber, and these two controls operate in series. V

Before the piston 20 is movedsufiiciently to entirely close off the passage through the notch 46 sufiicient oil pressure will have been developed in the chamber I la to overpower'the spring 65b, moving the valve 64 toward the left off its seat 63 and permitting oil to pass through the duct 62 into the chamber-l lb. The extent to which the' valve is moved off itsseat is determined by the pressure inthe chamber I la, and the strength of the spring'65b, and because of the tapered body of the valve 64 the effective opening through the duct 62 wi1l' be graduated in predetermined proportion to the pressure developed in the chamber'lla.

Assuming that the pistonhas moved to the end of its stroke in the right hand direction, the-vehicle spring 39' now being completely compressed, will begin to expand and move the piston toward the left. This will cause oil to be displaced from the chamber llb back'into chamber Ila, but at first the oilcannot pass by way of the notch 41 in the throttle bar 45 and its only escape will be by way of the duct 62, until the piston has moved farenoughjto the leftfor the right hand edge of the wall 59'to begin to open the passage by way of the notch-4i. 1 'Inother words, the piston will have moved back practically to its normal position before any relief can take place through the notch 41; Thereafter, -oil will pass by way of the outer edge of the wall 58 approaches the outer inclined face of the notch 41 suflicientlyto materiallythrottle the passage of oil therethrough. When this throttling reaches a certain amount, pressure-will be developed suflicient again to op-. crate the valve 64 against the pressure of spring 64a, so that the oil which cannot escape by way of the throttle passage now makes its way through the duct 52 into the chamber Il w.

1 On small movements of the piston, the valve 54 does not-come into play because there is sufficient leakage to take care of the escape of oil caused by the comparatively small compressions developed by such small spring movements. It will be observed, however, that the notch 46 is nearer the center line of the shock absorber than is the notch 41, and consequently when the piston is reciprocated greater pressure will be developed on movements in one direction than on movements in the other. The relative positions of the notches as well as the inclination of their walls maybe varied to any desired extent, thus providing further means of controlling the snubbing characteristics of my improved shock absorber.

' I have described the action of the piston when the vehicle passes over an obstruction, butit will be'understood that the same action takes place, although in the opposite direction, when a vehicle wheel drops into, a hole or depression in the road and causes an initial expansion of the spring from normal position. In such case the piston initially moves toward the left, as shown in Figs. 2 and 3,

and then moves toward the right on the rebound of, the spring.

A better understanding of the operation of the cal-resistancatravel curves which may be obtained with my shock absorber. In this diagram measurements parallel to the axis Y-Y' represent movements of the vehicle axis with respect to' the body, or vice versa. The normal position of the piston is indicated at O] Movements of the piston toward the right are read upward on the diagram and movements toward the left downward. Variations of the pressure in the chamber i in are indicated by the lines to the right of the axis YY and pressures in the chamber HZ) to the left of said axis. Thus, on an initial compression stroke of the vehicle spring, the line O--b-c indicates the variation of pressure in the chamber Ilawith corresponding displace ment of the piston. Avery smooth curve is provided, because the spring control overlaps the throttle control to such an extent as to smooth out the curve. Were. it not for the cushion plunger 61, the pressure curve would build up very rapidly at the start and would follow substantially the line O-bG-cl In the diagram I have shown a number of curves in full lines indicated by the reference letters, A,.B, C, D, E, and F. Each of these is a typical resistance-travel curve obtained by sustained oscillation of the spring through a predetermined range; the curve A represents a cyclev of pressuresv obtained by oscillating the spring through a maximum range. 'After the pressure has risen to a maximum in the chamber 1 i a, the. piston starts to move in the opposite direction and the pressure in chamber llw drops v ter of the cylinder than is notch 41.

rapidly to-zero, while pressure will be rapidly builtup in the chamber l'lb reaching a maximum at a pointd'. This pressure will be maintained ata fairly constant value even past'the point at which thenotch 41 begins to open, because the velocity of the piston is a factor that must be considered. At the pointe, the escape through the notch 41 will be sufiicient to cause a rapid d Qp ofpressure in the chamber llb, which will continue even afterthe piston has moved well past the normal position indicated by the axis X-'- X'-. {At the point I the throttling of the notch 41 bythe-wall 59 willbe sufficient tobuild up pressure: again in the chamber Ilb. Eventually the pressurein thechamber will rise sufilciently to openthe valve 64 against the spring 65a, and the pressure will continue to rise until it reaches a maximum atthe pointy. Thereafter the piston will start on its return stroke, toward the right, and the pressure will drop to zero, at h.

On this return stroke of the piston the pressure curve developed in the fourth quadrant Y' -OX would'be substantially identical with that developed in the second quadrant Y-O X', were it not for the cushion plunger 61. The full line hr-i represents the pressure travel curve that would be formed if no. cushion were present, and the broken line hi'--7' represents the modification of thiscurve caused by the cushion plunquadrant will be substantially identical to that of the third quadrant XO-Y.

The shape of the resistance-travel curves will 7 depend upon the amplitude of movement of the spring; but even the smallest curve illustrated will show considerable compression in each quadrant. of the cycle. As illustrated, the curve F is, substantially a rectangle with somewhat lower pressure developed on the compression stroke than on; the expansion stroke of the spring, because the notch 46 is slightly nearer the cen However, the curve F is modified in the fourth quadrant bythe cushion plunger, this modification being illustrated by thebroken line k- --Zm.

The curve E is very similar to the curveF, but a marked change in the form of the pressuretravel curve is to be noted as the amplitude of piston, movement is increased to form the curves D, C, B, and A. In the case of curves D, and C,

thenotch 46 is not entirely cut oil? by movement consequently the only escape for the oil is by way of theduct 62. Thus, much greater pressures are developed on-movements of the piston toward normal, than on movement of the piston away from normal, except in a case of small ton movement is increased to such. anse'xtent as to almost orentirely close off thexnotch, 4.6; The oil must then force'itsaway through .the duct 62, and consequently a-considera ble. pres-. sure is built up forming the bulges c and'g .respectively, in the first and third quadrants of the diagram. It will be observed that with the throttles as illustrated, a straight line pressure is provided by movementsjofthe spring toward normal in the case of curvesA and .B andalso in the case of curves E andFQIt mustbe borne in mind that the diagram showsresistance-travel curves-produced by sustained; oscillationsof the spring. and that in actualpractice the curves will spiral down to zero as the oscillationzof the spring dies down. 1 z, 1

The cushion plungerfi'l plays an important part in taking care of sudden jolts produced when the vehicle wheels strike an abrupt obstruction at high speed. It is particularly. valuable. in taking care ofjolts produced when the wheel drops into a hole, and then is thrown suds denly upward as it strikes the far wall of. the hole. I Thus assuming thatthe piston has dropped to the position 71, in the diagram and then encounters thefar wall of the hole, if no cushion were provided the pressure would mount suddenly in the chamber 1 iaimparting a severe jolt to the'vehicle frame. 'With the cushion plunger present, however, the shockis eased oil and in the curve A the pressure follows the curve 7"i-y'. Similarly, the other curves aremodified as shown by broken lines in the diagram. The cushion plunger 5? may be placed ateach end of the piston. Thus in Fig. 2 Ishowin broken lines a cushion, plunger at the left hand side of the piston. However, thecushionplunger is preferably provided only at that end which is under pressure during the compression stroke of the spring. It is on movements in this direction that highest pressure may develop. The vehicle body moves up-and down only at itsnatural periodicity and the, axle moves downward under limited spring pressure with a harmonic motion due to the natural period. of oscillation of the spring in conjunction with the weight of the wheel and axle, but the upward movement of the spring may take place at a; much higher rate depending upon the shape of'the'obstacle encountered and the speedol travel: of the vehicle. In other words, there are knownin'axie mum fluid pressures to contend with insofar as body movements are concerned;but-unknown and indefinite ones resulting from thenpward axle movement, and hence by placing the cushion plunger in the right hand end of the piston, as shown in the drawings, abrupt variations of pressure on the compression stroke of the spring are taken care of. I

Obviously, the cushion plunger may be placed in the cylinder wall instead of the piston, if so desired. Such a construction is shown in Fig. 2a wherein parts corresponding in function to those in Fig. 2 are given like reference numerals with a prime sufiix. Thus a thimble 69 is threaded into the end cap 12 of the cylinder II. In this thimble is fitted a cushion plunger 61' which is backed by a compression spring 10. A strap H serves as a stop for the cushion plunger 61 and a pipe 80 connects the'thimble from a point back of the cushion plunger, to the interior of the cylinder ll.

It will be clear from the foregoing description that I have devised a shock absorber in which retarding resistance is provided in each quadrant ofsaa pressure. cycle, and in which the pressure curve in each quadrant may be separately con.-

trolledli-The oil is displaced directly from one working chamber into another, and its escape 'is',.constricted byposition-controlled throttle means :and pressure-controlled throttle means operating 'inseries, together with an auxiliary pressure-controlled throttle means which operates on piston movements of considerable amplitude. The position-controlled throttling means may be varied by varying the location, size andinclination of the. notches in the throttle bar, the pressure-controlled throttling means may be varied .by changing the'shape of the valve bodies 54a and 55a" respectively, and of the springs 56 and. 51 respectively,:while the high pressure throttle 0011- trol may-becorrespondingly adjusted by varying the taperor shape of the valve 64 and the strength of the springs aand65b. The resistance-travel curve may be further modified by varying the diameter of the cushion plunger 61 and the strength of the spring 10.

In my copending application, Serial No. 333,758, filed January 21, 1929, I show a number of resistance-travel curves produced by varying the shape of the. throttle bar, but all of said variations relate to the larger spring movements and show litt1e, if,-any, resistance to the lesser spring movements., With the shock absorber disclosed in the present application all of the resistance-travel curvesshown in said copending application may bereproduc'ed and at thesame time a substantial amount of resistance to smaller spring movementsgmay be provided by varying the relative position of the notches 46 and ll. A few of such resistance travel variations on small spring movements are shown in Figs. 10 to 12 inclusive.- In these figures a greater pressure is developed than inthe corresponding curve F of Fig. 8. In Fig. 10 the'pressure is substantially as great on one side of the axis Y-Y' ason the other; in Fig. 11 there is a greater-pressure on the left hand side than on the right hand sideof the axis, while in Fig. 12 a greater pressure is developed on the right hand side of the axis. 7 Itwill be understood, of course, that these curves do not show the eifect of a cushion plunger which, if present, would modify each curvein the same manner as described above in connection with Fig-8.3,

While I have described a specific structure embodying my improved method of spring control Iwish it to be understood that this is to be taken asillustrative and not limitative, and that my improved method is not restricted to the particular. structure-disclosed but 'isj'of such'broad 3.137 plication as falls within the scope of the following claims.

I claim:

1. In the method of retarding oscillations of a spring, the steps which consist in employing the energy of thespring to exert pressure upon a body of liquid, permitting escape of the liquid in a confined stream, constricting the stream in predetermined relation to successive instantaneous positions of the spring, and also constricting the stream in predetermined relation to the pressure 7 instantaneof said orifices in predetermined. relation to successive instantaneous positions of the spring, and increasing the area of the'other of said orifices in predetermined relation to the pressure exerted by the spring on the liquid. I

l 4. In arnethod of retarding oscillations of a spring, the steps which consist in employing the energy or the spring to exert pressure on. a body of liquid, permitting resilient displacement, without loss, of a part of the liquid when said pressure exceeds a predetermined'value, permitting escape of another part :of the liquid through two orifices successively, varying the area of one of said oriflees in predetermined relation to the pressure of the liquid, andva'rying the other-of said orifices in predetermined relation to successive instantaneous positions of the spring. a

5. In the methodof retarding oscillations of a spring, the steps which consist in employing the energy of the spring to exert pressure on a body of liquid, permitting escape of the liquid in'a confined stream, constricting the stream in predetermined'relation to successive instantaneous positions of the spring, also constricting the stream in predetermined relation tothe pressure exerted by the spring on said body, and permitting auxiliary pressure-controlled escape of the liquid when the pressure on said body exceeds apredetermined value. Y a i i 6. In the method of retarding oscillations of a spring, the steps which consist in employing the energy of the spring to exert pressure on a body pressure of the liquid, varying the area of theother of said orifices in predetermined relation to successive instantaneous positions of the spring, permitting additional escape for the liquid through a third orifice, and varying the area of the latter orifice in predetermined relation to J the pressure developed in said body;

' 7. 'In the method of resisting-reciprocation of a piston in a hydraulic shock absorber, thesteps which consist in unyieldinglyconstricting the discharge of fluid displaced by the piston in pro-1- determined proportion tosuccessive instantaneous positions of the piston and concurrently yield ingly constricting said discharge.

Y 8. In the method of resisting reciprocation of.

a piston in a hydraulic shock absorber, the steps I which consist in unyieldingly constricting the discharge of fluid displaced by the piston 'in predetermined proportion to successive instantaneous positions of the piston and concurrently'yieldingly constricting said'discharge, the constriction ,being' so adjusted as to afiord greater resistance to movement of the piston in either direction to- Ward normal position than in either direction instantaneous positions of the piston and also in predetermined relation to the pressure of the 10. In a hydraulic shock absorber, a'method of' resisting reciprocation of the pistonin a cylinder divided by the pistoninto two working chambers, which method comprises the steps of discharging 'fiuid from one of said chambers directly into the other, constricting said discharge in 'predetermined relation to successive instantaneous positions .of the piston and also in predetermined relationto the pressure of the fluid, and supplying each chamber with fluid to make up for leakage pastthe piston. a

11. The method of retarding oscillations of 'a spring which includes the steps of, employing the energy of the spring to exert a cycle of pressures on a body of liquid, providing separate control of the pressures developed on small movements of the spring as against larger movements thereof and providing individual control of the pressures developed in each quadrant of the cycle on larger movements of the spring.

12. The method of retarding oscillations of a springwhich includes the steps of employing the energy of the spring to exert a cycle of pressures on a body of liquid and thereby cause displacement of the liquid, applying resistance to such displacement, separately varying the amount of such' a resistance on small movements of the spring as against larger movements thereof, and, on larger movements of the spring varying the amount of such resistance in each quadrant of the cycle individually.

' JOHN M. NALLE.

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