US2018051A - Shock absorber - Google Patents

Description

R S. CARTER SHOCK ABSORBER Oct. 22, 1935.

Filed Feb. 5, 1930 Patented Oct. 22, 1935 UNiTED STATS OFFICE 24 Claims.

The invention relates to liquid-type shock absorbers and consists in improvements in design and mode of operation as hereinafter more fully set forth.

The accompanying drawing exemplifies the principles of the invention in the form at present preferred, Fig. 1 being an axial section. Fig. 2, an end elevation before the yielding wall and casing cover has been applied. Figs. 3, e, and 5 are sections respectively on the correspondingly numbered section lines of Fig. 1, Fig. 6 is a detail illustrating a position of the yielding wall on the impact stroke of the device, and Figs. 7 and 8 are modifications later described.

The device as shown comprises a casing i having an interior circular or cylindrical chamber divided by two internal radial partitions 2, and containing a rotary spindle 3 co-axially journalled therein and carrying two sector-shaped 20 or wing pistons l, fitting the interior space and oscillating between the parti ions, and the casing also contains a body of oil or other liquid constituting the retarding medium, not indicated in the drawing. The casing is provided with 25 attachment ears 5 or other equivalent means for connection to one of the two parts between which relative movement is to be controlled and the piston spindle is provided with a crank arm 6 for attachment to the other of said parts, so 3 that relative movement between such parts, for example, between the spring-supported frame and the axle of an automobile, produces rotation of the pistons in the sector shaped spaces between partitions. As a convenience of manu- 35 facture, the partitions 2 are separately made and key-seated in grooves cut in the cylindrical wall and also dowelled to the casin wall I, as indicated by the dotted lines in Fig. 1, so that in effect they constitute integral parts of the easing. The piston spindle has a long bearing in wall i of the casing and its part within the casing is enlarged as a hub B on which the pistons G are carried, being rigid and preferably integral parts th reof. The ends of the pistons are wide and closely fitted to the adjacent surfaces of the casing so as to minimize leakage at this point and the hub 8 is closely fitted to the ends of partitions for the same purpose and the shoulder of the hub bears against the surface 5 of the casing wall l for the purpose of forming therewith a seal or joint to prevent or minimize escape of the liquid into or through the spindle bearing. This joint is kept tight in part by the hydraulic pressure of such liquid itself, which has access to act on the end surface of the piston structure, and in part by the mechanical pressure of the spring yielding wall presently referred to. Such small amount of oil as succeeds in passing this shoulder seal may pass into the bearing boss of the spindle, or into the oil grooves H and 92 thereof, and may drain therefrom into the replenishing reservoir It through the drainage duct ita and the replenishing duct Ila presently referred to. A packing gland l3 closes the extreme end of the spindle bearing 10 against leakage to the outside.

The opposite end of the space or spaces in which the pistons work is bounded by an elastic or yielding wall i l, extending transversely across the axis of the piston spindle, and adapted to move away from the end of the hub and from the. edges of the pistons as well as from the edges of the partitions under the liquid pressure created by the pistons movement. This wall is desirably and preferably formed as a circular disc of elastic metal, although it might be otherwise and it is firmly held by its margin in a rebate groove, formed in the casing wall and clamped to such seat by the rigid external cover plate l5, its central portion being the part which is adapted to flex back and forth. The attachment of the rigid cover plate it to the wall of the casing is preferably made by welding the one to the other and when the cylinder is made of cast iron, that operation is facilitated by the use of a ring of steel Iw v previously imbedded or cast in the edge of the cylinder, the edge of which ring is exposed to be welded upon and to the margin of the cover l5, making a specially secure and leak-proof connection. The interior face of the wall 1 5 is concaved or recessed to allow for the movement of the elastic wall, and form an abutment therefor, determining its extreme movement.

On the rotation of the pistons in direction corresponding to compression of the vehicle springs,

and which is referred to as the impact stroke, the liquid in the piston spa es on the advancing sides of the pistons, marked, impact in the drawing is put under pressure and such pressure acting on the movable wall M moves or bends it outwardly away from the edges of the wing pistons, thereby opening or enlarging the normal crevice between such wall and the piston structure and permitting the oil to flow around and to the opposite sides of the pistons. A certain desirable but moderate resistance to piston movement is thus produced and will be seen to be determined by the elastic characteristics of the yielding wall, and, as will be apparent, the quicker the'movement of the piston, the greater will be the liquid pressure and 5'5 the wider the by-pass crevice or passage. The

I normal position of the yielding or flexible wall,

to which it returns after the impact stroke, is determinedby an abutment block l6, axially adjustable in and splined to a central cavity in the end of the piston hub and arranged to be pro truded' or retracted by a screw-threaded adjustment stem I! which extends the length of the pistonspindle and through a small packing gland l8 beyond the crank hub where it is accessible for manipulation. This screw stem has a collar l9 fitting the hub cavity and backed up by a soft lead washer toprevent or restrain leakage of oil past the abutment block and along the screw stem;

The block [6 is formed with a tip of reduced diameter fitting or projecting into or through a central hole in the elastic wall I4 and forming a shoulder which the margin of the hole in the wall bears against, being thus limited in the extent to which it may approach the piston structure. It is normally set to hold the Wall at a slight clearance from the piston structure and this puts the wall under a corresponding tension so that it exerts a normal endwise thrust on the piston thereby maintaining the hub seal above referred to under an appropriate but moderate pressure at such times as the much stronger hydraulic effect is not active to maintain it. Such hub seal is always under pressure, greater during piston movement than at other times.

The projecting tip of the abutment block l6, whichtelescopes through the hole in the yielding wall, is formed with small axial duct 2| and cross duct Zia which. latter in any position of 'clearance adjustment registers with a wider cross duct 22 in the piston structure and thereby provides a constantly open communication between the liquid space back of the elastic wall and the spaces on the recoil sides of the pistons, that is to say; on the sides of the latter which compress the liquid on the recoil movement of the vehicle springs. See Fig. 5. The liquid displaced by the outward movement of the wall during the impact stroke escapes through this communication to the piston spaces on the recoil sides of the pistons which are then under lower pressure. The location of this communicating passage in the piston structure as shown is its best, but not its only possible location as will be apparent.

During the recoil stroke when the pistons move in the opposite direction, and put the liquid on the recoil sides of the pistons under pressure, such pressure is communicated through this same communicating passage to the back side of the movable wall and thereby the pressures on the opposite faces of such wall are substantially balanced so that it is not then subject to outward movement. The liquid under pressure may then escape only through the crevices represented by the normal clearance of the wall from the pistons and partitions and which is determined as above stated, by the adjustment of the screw stem and its abutment block is. Resistance to recoil is therefore positive in the sense that it is independent of the movement or flexure, except 10- 'the pistons to press the elastic wall outwardly thereby opening up further the crevices between such wall and the pistons and partitions, thus permitting relatively free passage of liquid from one side of the pistons to the other, and that on the reverse stroke, the liquid then in the recoil spaces is put under pressure, which pressure is. 5 communicated through duct 2| to the back side of the elastic wall, so that such wall is now restrained from crevice-opening movement, and the liquid, in order to pass from one side of the pistons to the other, must be squeezed through the 10 normal width of the crevices. This width is adjustable by the use of the set screw. Screwing it one way widens the crevice and reduces the resistance, and vice versa.

It is important that the spaces of the device 15 which confine the liquid while under pressure. shall be completely and solidly filled with such liquid, because air, gas or oil vapor entrapped therein produces an objectionable irregularity of action, and accordingly provisions are made to $0 vent such gas. This is accomplished by drilling an extremely fine hole 23 through the wall ll at the top of the piston space on the impact side of the upper partition 2. This hole leads into the top of the replenishing chamber Hi, and is so 26 small that while it suffices to pass gas through I' it, under the eflect of heavy pressure, it does not pass any considerable portion of liquid, but that liquid which does escape therethrough is caught in the chamber Ill, to be subsequently returned as presently described. Any air or gas trapped in the space behind the movable wall I4 is vented to the piston space and, thence through hole 23. This is done by making. a groove 24, which may be merely a scratch, on the ledge of the rebate groove in the casing body against which the wall is seated and clamped, prior to its assembly. The wing pistons 4 are either made solid or they are hollowed on their upper side as indicated, thus avoiding gas pockets in them. It will be seen therefore that any air or gas in the compression spaces will work its way to the top of the casing there to be expelled.

Return of the oil which escapes into the replenishing reservoir through the vent 23, or through the spindle bearing, or past the set screw, is accomplished automatically and continuously by the action of the pistons and through the duct 1 la. in the casing which duct communicates through a radial duct to duct 25 in the spindle wi h an axial passage or chamber 26 inside of the spindle around the adjustment screw il. This chamber connects through four ducts 2?, with the piston space on each side of the pistons, each of which ducts is provided with a'ball check valve closing inwardly or toward the chamber 25, so that no escape of liquid from the piston spaces is permitted. At such times as the pressure on either side of any piston is less than the pressure in the chamber, liquid flows through the corresponding replenishing duct and into that space, keeping it solidly filled. The replenishing duct Ila extends to the lower part of the reservoir l0 so that it can take oil from 66 it, even though it is partly empty.

'Fig. '7, being an end view similar to Fig. 2, illustrates the invention as applied to a single-piston shock absorber. In such case there is but a single partition, 28, of sector form screwed and dowelled to the casing end wall 1 and closely fitting the cylindrical hub 8 of the piston spindle, like the partitions 2. The single sectorshaped piston 29, rigid on the hub, oscillates through an arc approximately and like the 1 5 pistons 4 is fitted close to the peripheral casing wall andto the end wall I so that the main escape for the liquid moved by it is through the crevice formed between it and the yielding wall and between the partition and such wall, which crevice is controlled by the adjustment block It as before. Pressure equalization on opposite sides of the yielding wall, on the recoil stroke, is established as before through the communication marked 2|-22 and replenishment through the check valved ducts 21 and the structure and action are otherwise the same as the form first described.

Fig. 8 represents a desirable addition to either of the forms above described, consisting of a ball check valve 30 in the duct 2! which leads from the piston space to the space back of the yielding wall. This valve is purposely leaky, made so by grooving its seat and its function is to permit a relatively free flow from behind the wall to the recoil side of the piston on the impact stroke, but a relatively restricted flow in the opposite direction, on the recoil stroke, according to the leakage permitted, the result being that the yielding wall is not so quickly restored to its normal seat on the end of the adjustment block it. This means that the flow crevice, around the piston, opened wide upon an impact stroke, lags in that dimension during the initial part of the following recoil stroke, the extent of the lag being determined by the rate of leakage flow through the valve 30 or through the telescopic connection which the block it has with the yielding wall, one or both. The condition is thus one of a liquid retarding crevice or passage which is automatically established of a certain proper capacity for one stroke and for a part of the succeeding reverse stroke and of another and less capacity for the balance of the latter stroke, producing an action which accommodates in a superior manner the short quick vibrations incident to the travel of an automobile over a so-called corduroy pavement. It will be observed that all of these efiects come about from the presence of the yielding wall coasting with both the partition and piston to form the escape crevice for the liquid, and further, from the hydraulic control of the position of such wall and thereby of the capacity of such crevice. Moreover the use of a yielding Wall as one of the end walls of the cylinder of a rotary piston shock absorber affords the very practical advantage, from the manufacturers point of view, that no particular accuracy has to be maintained as respects the widths of the piston and of the partition in relation to the axial dimension of the cylindrical wall. Heretofore wing-type pistons and their partitions have required to be closely fitted between the two end walls of the cylinder with but a very small tolerance in order that the finished articles would possess uniform characteristics and within the limits of their adjustment, give an equal action at all four corners of an automobile. In the present case it will be seen that the yielding wall accommodates a very considerable varia-- a movable chamber end wall extending transversely of said spindle and normally out of contact therewith and adapted to yield under liquid pressure to enlarge the liquid flow passage between itself and the edge of the piston.

2. A liquid type shock absorber comprising a liquid-containing, substantially cylindrical chamber, a rotary spindle journalled therein, a wing piston forming a rigid part of such spindle and fitting the peripheral chamber wall, a movable chamber end wall extending transversely of said spindle and forming a liquid flow passage between itself and the edge of the piston and a liquid passage for balancing the liquid pressures acting on opposite sides of said wall.

3. A liquid type shock absorber comprising a liquid-containing, substantially cylindrical chamber, a rotary spindle journalled therein, a wing piston forming a rigid part of such spindle and fitting the chamber wall, a chamber end Wall extending transversely of said spindle and adapted to yield under pressure of the liquid to form a passage between itself and the edge of the piston in one direction of piston movement and means for substantially balancing the pressures on opposite sides of said movable wall during the other direction of piston movement.

4. A liquid type shock absorber comprising a liquid-containing, substantially cylindrical chamber, a rotary spindle journalled therein, a wing piston forming a rigid part of such spindle and fitting such chamber, a chamber end wall extending transversely of said spindle and adapted to move relatively thereto, and means for substantially balancing the pressure on opposite sides of said movable wall, comprising a duct extending between the back side of said movable wall and the liquid space on one side of the piston.

55. A liquid type shock absorber comprising a substantially cylindrical chamber, a rotary spindle therein carrying a rigid wing piston having its free end fitted to the peripheral wall of said chamber, a rigid end wall to such chamber, an interior yielding chamber wall forming a closure to the piston space and adapted to yield away from the piston edge on the impact stroke of said piston and means for preventing similar yielding on the recoil stroke.

6. A liquid type shock absorber comprising a substantially cylindrical chamber, a rotary spindle carrying a rigid wing piston, a rigid cylinder end wall, an interior yielding cylinder end wall forming a closure to the piston space and adapted to yield away from the piston edge on the impact stroke of said piston and means for preventing similar yielding on the recoil stroke comprising a pressure balancing liquid passage extending through the spindle from the recoil side of the piston to the space between the two cylinder end walls.

'7. In a liquid type shock absorber the combination of a piston and piston space having an elastic wall adapted to control liquid flow around the piston, and an abutment limiting the movement of said wall and also providing a liquid passage from one side to the other of said wall.

8. In a liquid type shock absorber the combination of a piston and a piston space having a yielding wall adapted to provide a liquid escape and provided with a perforation, a shouldered abutment engaged in said perforation, and a duct extending through said abutment to the opposite side of said wall.

9. A liquid type shock absorber comprising a chamber containing a rotary spindle with a wing piston thereon, a yielding wall and a part on the spindle having telescopic engagement with a hole in said wall and controlling liquid flow to the space in rear of said wall.

10. A liquid type shock absorber comprising a chamber having a partition, a rotary spindle carrying a wing piston coacting with said partition, and a yielding wall extending in a plane transverse to the piston axis and adjacent'the edges of said piston and partition, and forming liquid escape passages therewith, and means for locking said wall against movement on the recoil stroke.

11. A liquid type shock absorber comprising a partitioned cylindrical chamber having rotary wing pistons between partitions, and a movable wall common to all the piston spaces in said chamber adapted to move away from the edges of said pistons and partitions to form liquid flow passages, and a duct through which recoil pressure is imparted to the back side of said wall.

'12. A liquid type shock absorber comprising a liquid-filled chamber, a rotary spindle having a wing piston bearing by its edge upon one wall of said chamber, the wall adjacent the opposite edge of the piston being elastic and arranged to press said piston toward said first mentioned wall, both sides of said elastic wall being exposed to the liqum.

13. A liquid type shock absorber comprising a partitioned chamber, a rotary spindle therein having a hub with its shoulder seated against one 7 end wall of the chamber, a wing piston on the hub, a yielding wall at the opposite end of said hub organized to press said'shoulder against its seat on said wall and means providing for liquid flow into and from the space in rear of said elastic wall.

14. A liquid-filled shock absorber comprising a chamber, a rotary piston therein having a hub and a shoulder forming a seal with one end wall of the chamber, the other end of said hub being subject to hydraulic pressure thrusting the shoulder toward said Wall, an elastic wall in said chamber also. thrusting against said hub and means permitting liquid flow to the space in rear of said wall.

15. A liquid type shock absorber comprising a partitioned cylinder, a rotary spindle having rigid wing pistons between the partitions thereof, an interior elastic end wall for the cylinder adapted to flex away from said pistons on the impact stroke and a normally open communication between the back side of said wall and the recoil sides of the pistons.

16. In a liquid type shock absorber, the combination of a chamber, a piston adapted to put the liquid under pressure, a yielding wall coacting with said piston to provide a liquid escape crevice and subject on both its sides to the liquid pressure and means for controlling the liquid flow from one side to the other.

17. In a liquid type shock absorber, the combination of a chamber, a piston adapted to put the liquid under pressure, a yielding wall controlling escape of liquid and subject on both its sides to the liquid pressure and means for controlling the liquid fiow from one side to the other of said wall, said means permitting an easier flow in one direction than the other. 7

'18. A liquid type shock absorber comprising a cylinder, a rotary spindle having an annular shoulder forming a seal with one end wall of the cylinder, a wing piston on the spindle, elastic means urging said shoulder against said wall, the end of said spindle being exposed to the pressure of the liquid which also urges said shoulder against said wall, a packing gland beyond said 5 shoulder seal, a liquid chamber associated with said spindle and receiving liquid escaping said seal, and a check-valved replenishing duct be-' tween said chamber and a piston space.

19. A liquid type shock absorber comprising a 10 liquid-filled, substantially cylindrical chamber, a rotary spindle coaxially journalled therein, a wing piston forming a rigid part of such spindle and fitting the peripheral chamber wall, a yielding end wall extending transversely of the spindle and adapted to be moved to different positions to form a passage for liquid, a replenishing reservoir and means for venting gas from the space on both sides of said yielding wall into said reservoir. V

20. A liquid type shock absorber comprising a chamber, a rotary spindle therein carrying a wing piston, an outer rigid cover for said chamber, and an interior yielding wall, the piston space and the space back of said wall being solidly filled with liquid and a replenishing chamber connected with said spaces for maintaining thatcondition.

21. In a shock absorber, the combination of a casing with a plurality of fixed vanes therein, a rotatable shaft having a plurality of movable vanes rotatably mounted in said casing, said casing having an open end and an annular shoulder adjacent said. end, a resilient :metal member seated on said annular shoulder and forming a wall of said chamber, said resilient member having supporting means adapting it to flex only on the impact stroke to by-pass fluid about said vanes, and a recessed cover for closing said casing and clamping the outer edge of said resilient member against said shoulder;

22. In a shock absorber, the combination of a casing, with a movable member having a rotatable shaft and a movable vane carried by said shaft, and a resilient diaphragm carried by said casing transversely to said shaft and adapted to by-pass fluid from one side of said .vane to the other, and means for preventing flexing of said diaphragm.

23. In a shock absorber, the combination of 5 r a casing, with a movable member having a rotatable shaft and a movable vane carried by said shaft, a resilient diaphragm carried by said casing transversely to said shaft and adapted to by-pass fluid from one side of said vane to the other, a liquid-conducting port through said diaphragm, and a cover for clamping said diaphragm in said casing and effecting a liquid tight closure of said casing, the space between said cover and diaphragm having means for venting air therefrom.

24. A liquid-filled shock absorber comprising a liquid-containing partitioned chamber, a rotary spindle having a rigid wing piston thereon within the chamber, and a yielding wall coacting with the edges of the partition and said piston V and normally forming restricted flow paths therewith, and means whereby said wall is held against yielding to enlarge said flow paths on one stroke of said piston, said means permitting said wall to yield on the reverse stroke thereof to enlarge said flow paths.

RUSSELL S. CARTER.

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