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Title:
A HYDRO-MECHANICAL STOP HAVING A RESTRICTIVE PASSAGE
Document Type and Number:
WIPO Patent Application WO/1984/001197
Kind Code:
A1
Abstract:
A shock absorber (10) has a rebound stop assembly (22). The rebound stop assembly (22) rests upon a shoulder (30) fixed to a piston rod (16). The rebound stop assembly (22) includes an elastomeric ring (24) interposed between two collars (26 and 28) forming an annular chamber (74) therebetween. At the end of the rebound stroke of piston rod (16), the rebound stop assembly (22) is axially compressed between the shoulder (30) of the piston rod (16) and the rod guide (18) until the elastomeric ring (24) deforms to abut the inner wall (64) of the working cylinder. As the elastomeric ring deforms, the annular chamber decreases in volume. A restrictive passage (71) allows a restrictive flow of fluid therefrom. An additional chamber (70) is formed which is in restrictive fluid communication through the passage (71) with section (68) of rebound chamber (20). Further compression of the stop assembly (22) decreases the volume of both chambers (70 and 74), and causes restrictive fluid flow out therefrom through the passage (71) into the section (68) of rebound chamber (20). The compression of the elastomeric ring and the restrictive fluid flow provides additional damping at the end of the rebound stroke.

Inventors:
Mourray
Jack
Wayne, Nagy
James
Peter
Application Number:
PCT/US1982/001304
Publication Date:
March 29, 1984
Filing Date:
September 20, 1982
Export Citation:
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Assignee:
FORD-WERKE AKTIENGESELLSCHAFT FORD FRANCE S
A FORD MOTOR COMPANY LIMITED FORD MOTOR COMPANY MOURRAY, Jack, Wayne NAGY, James, Peter.
International Classes:
F16F7/08; F16F9/32; F16F9/49; F16F9/58; (IPC1-7): F16F9/49
Foreign References:
US2352351A1944-06-27
US2369008A1945-02-06
US2599477A1952-06-03
US3057441A1962-10-09
US3625321A1971-12-07
US3967707A1976-07-06
US3969989A1976-07-20
US4113071A1978-09-12
US4328960A1982-05-11
AU117866A
CA467010A1950-08-01
FR1584110A1969-12-12
Other References:
See also references of EP 0119197A4
Download PDF:
Claims:
CLAIMS
1. The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: In a telescopic shock absorber including a working cylinder, a piston slideably received within said working cylinder and defining a boundary for a rebound chamber within said cylinder, a piston rod connected to said piston and extending through one end of said working cylinder, closure means for closing said one end. of said cylinder and slideably mounting said piston rod, the improvement characterized by: a esiliently flexible ring mounted about said piston rod; said ring having an annular outer wall with a diameter smaller than the diameter of an inner wall of said working cylinder; first and second collars pressed fit into opposite axial open ends of said flexible ring; each collar having an axial extending portion; said axial extending portion having an inner wall with a diameter sized to receive said piston rod with a clearance therebetween and an outer diameter sized to be pressed fit within said flexible ring; each collar having a radially outwardly extending shoulder, said shoulder having a surface facing axially inwardly for abutting an axial end of said flexible ring and a surface facing axially outwardly; said surface facing axially outwardly having a plurality of axially extending protrusions circumferen tially spaced thereabout; said flexible ring and pressed fit collars inter¬ posed between said closure means and a shoulder fixed to said piston rod such that, at the end of a rebound stroke of said piston rod, said shoulder and said closure means axially compress said ring by pressing against said protrusions of said respective second and. first collars; said flexible ring being sufficiently flexible such that, when it is axially compressed a predetermined amount, the diameter of an annular portion of said annular wall enlarges to abut said inner wall of said working cylinder and forming with said cylinder and said closure means a hydraulic chamber; the inner wall of said flexible ring spaced from said piston rod defining an annular chamber therebetween; said second collar, when in abutment with said shoulder, forming a restrictive passage section between said annular chamber and said rebound chamber; said first collar and said closure means, when in abutment with each other, form a restrictive passage section from said hydraulic chamber to said annular chamber; and said restrictive passage sections restricting hydraulic fluid flow in a controlled manner from said hydraulic chamber and said annular chamber into said ' rebound chamber upon further compression of said flexible ring beyond said predetermined amount.
2. In a telescopic shock absorber including a working cylinder, a piston slidably received within said working cylinder and defining a boundary for a rebound and jounce chamber within said cylinder, a piston rod connected to said piston and extending through one end of said working cylinder, the improvement characterized by: a resiliently flexible ring mounted about said piston rod; said ring having an outer annular wall with a diameter smaller than the diameter of an inner wall of said working cylinder; said ring having an internal diameter larger tha the diameter of said piston rod such that an annula chamber is formed therebetween; said ring interposed between an abutment fixed t said working cylinder and a shoulder fixed to said pisto rod such that, at the end of a rebound stroke of sai piston rod, said shoulder and said abutment axiall compress said ring; metering passage means interposed between sai ring and said end of said working cylinder, said ring an said piston rod, and said ring and said shoulder affixed t said piston rod; said ring being sufficiently flexible such that when it is axially compressed a predetermined amount, th diameter of an annular portion of said annular wal enlarges to abut said inner wall of said working cylinde and to form with said cylinder and said end of sai cylinder a hydraulic chamber; said annular chamber constructed to decrease i volume as said ring compresses; and a passage means communicating said hydrauli chamber and said annular chamber with one of said reboun and working chamber such that upon axial' compression of said flexible ring to said predetermined amount, a restric tive fluid flow occurs from said annular chamber to said one chamber, and upon further axial compression of said ring beyond said predetermined amount, a restrictive fluid flow occurs from said hydraulic chamber and said annular chamber to said one chamber.
3. A hydromechanical stop for a telescopic shock absorber comprising: a tubular resiliently flexible ring; a first and second collar mounted at opposite axial ends of said ring; each collar having an axial extending portion; each axial extending portion having an inne diameter sized to fit about a piston rod with a clearanc therebetween; each axial extending portion having an outer wal sized to be pressed fit within an opening at each axial en of said flexible ring; each collar having a radially extending shoulde with an axially inner facing surface for abutting respective axial end of said flexible ring; each collar having an axially outer facing en surface; each outer .facing end surface having axiall extending protrusions circumferentially spaced thereabout.
Description:
A HYDRO-MECHA ICAL STOP

HAVING A RESTRICTIVE PASSAGE-

Technical Field

This invention relates to a stop for a shoc absorber and, more particularly, to a hydraulic assiste rebound stop.

Background Disclosure Information

Often shock absorbers are designed such that th damping rate of the shock absorber becomes higher at th extreme ends of the rebound and compression strokes. Th additional damping is desired to prevent an abrupt halt to the piston stroke and to prevent jarring metal- o-metal contact between the various parts in the shock absorber. A variety of mechanisms have . been devised to render a higher damping rate at the two extremes. Springs and elastomeric jounce bumpers have been incorporated internally as well as externally of the working cylinder. In addition, secondary pistons have been used which become operative only at the extreme ends of the piston stroke. All previous mechanisms added to the cost of the shock absorber.

It is desired to have a hydro-mechanical stop which effectively dampens the end of a piston stroke while being economical to manufacture and assemble.

One hydro-mechanical stop has been disclosed and claimed in a co-pending patent application filed on the same day as the present application by one of the present joint inventors, Mr. Jack Wayne Mourray, and entitled SHOCK ABSORBER WITH A HYDRO -MECHANICAL STOP. The present invention is an improvement over the invention claimed in the mentioned co-pending application.

Summary of the Invention •

In accordance with the invention, a shock absorber has a working cylinder with a piston slideably received therein attached to a piston rod which extends through a rod guide at one end of the cylinder. A hydro-mechanical stop is coaxially mounted about the piston rod between the piston and the rod guide. The hydro-mechanical stop includes a tubular resiliently flexible ring mounted about the piston rod. The flexible ring has an outer annular wall having a diameter smaller than the diameter of the inner wall of the working cylinder . The ring rests on a shoulder fixed to the piston rod. The ring is sized relative to the diameter of said piston rod to form an annular chamber therebetween. At the end of a rebound stroke of the piston rod, the ring is axially compressed between the shoulder and the rod guide. Hydraulic fluid is forced from the annular chamber through a restrictive passage section. The ring is sufficiently flexible such that upon axial compression of a predetermined amount, the outer annular wall enlarges until it abuts the inner wall of the working cylinder to form with said cylinder and said rod guide a substantially closed hydraulic chamber. Upon further compression of the flexible ring, hydraulic fluid is forced from the annular chamber and the hydraulic chamber through a restrictive passage section to provide additional damping.

Preferably, collars are mounted at opposite axial ends of the flexible ring. It is desirable that each collar has an axial extending cylinder section with a central aperture therethrough large enough to receive the piston rod and to provide an annular space therebetween. The cylindrical section has an outer wall with a diameter sized such that the cylindrical section is pressed fit within an axial end of the flexible ring. In addition.

each collar has a radially extending flange. - Each * flang has an axially inner facing surface which abuts an axial end of the flexible ring. The outer surface of one of th radially extending flanges has a plurality of circumfer- entially spaced protrusions which are abuttable with the rod guide. The outer surface of the other radially extending flange has a plurality, of protrusions which abut the shoulder fixed to the piston rod. Sections of the restrictive passage are formed by spaces between the protrusions and the annular space about the piston rod. One end of the passage communicates with the hydraulic chamber. The other end communicates with the lower portion of the rebound chamber in the working cylinder. The annular chamber is interposed between the two ends of the passage.

Brief Description of the Drawings

Reference now will be made to the accompanying drawing s in which :

Figure 1 is a fragmentary side elevational and par tially segmented view of a shock absorber di sclosing a rebound stop in accordance wi th the invention ;

Figure 2 is a view similar to Figure 1 showing the rebound stop in par tial compression ;

Fig ure 3 is a view similar to Fig ure 2 showing the rebound stop in full compression ;

Fig ure 4 is a plan view of a -collar shown in Figures 1 through 3 ;

Figure 5 is a cross-sectional view taken along the lines V-V in Figure 4 ; Fig ure 6 is a cross-sectional view of the elasto¬ mer ic r ing shown in F ig ures 1 through 3 ;

Figure 7 i s a plan view of the elastomer ic ring ; Fig ure 8 is a cross-sectional view of the rebound stop assembly shown in Figures 1 through 3.

Detailed Description of the Preferred Embodiment

Referring to Figure 1, a shock absorber 10 has a working cylinder 12 with a piston 14 slideably mounted therein. The piston 14 is conventional in construction with valved restrictive passageways 15. A piston rod 16 is connected to the piston 14. A. rod guide 18 is fixedly mounted at the end of the working cylinder 12. A jounce chamber 19 is defined below the piston 14. A rebound chamber 20 is defined within the cylinder 12 about the piston rod 16 and bounded by the piston 14 and rod guide 18. In addition, a rebound stop assembly 22 is mounted within the working cylinder 12 about the piston rod 16.

The rebound stop assembly 22, as shown in Figure 8, includes a tubular elastomeric ring 24 and two collars 26 and 28 which are pressed fit within the elastomeric ring 24. The rebound stop assembly 22 is mounted on top of a shoulder 30 shown in Figure 1. The shoulder 30 is fixed, at least in the axial direction, to the piston rod 16.

The elastomeric ring 24, as shown in more detail in Figures 6 and 7, has an annular outer wall 32 of varying diameter with the midsection 34 having the largest diameter and the ends 36 having the smallest diameter. The inner wall 40 defines a central opening 38. The inner wall 40 also has a varying diameter with its largest diameter at midsection 42.

The collars 26 and 28 are identical in structure; therefore, reference now will only be made to collar 26 shown in Figures 4 and 5. The -collar 26 has an axially extending portion 44 and a radially extending shoulder 46. The axially extending portion 44 has an inner wall 48 forming a central opening 49 sized to receive a piston rod 16 and to provide an annular gap 50 as shown in Figure 1. The axial extending portion 44 has an outer wall 52 which is sized to be pressed fit within the opening 38 at end 36

WL-

of the elastomeric ring 24. The inner wall 48 and oute wall 52 define the inner and outer diameter of an annula axial end 54. The radially extending shoulder 46 define the second end 56 of collar 26. The end 56 has a pluralit of circular protrusions 58 circumferentially spaced abou the collar. Each protrusion 58 has a flat end surface 60. Each shoulder 46 also has an axial inner facing surface 6 which extends radially outwardly from annular wall 52.

As shown in Figure 8, collars 26 and 28 have their axial portions pressed fitted within the opening 38 at the opposite ends 36 of ring 24. The inner facing surface 62 of shoulder 46 of each collar abuts a respective end 36 of the ring 24.

Referring back to Figure 1, the assembly 22 is mounted about the piston rod 16 seated on shoulder 30 within the rebound chamber 20. More specifically, the protrusions 58 of collar * 28 rest on shoulder 30. The assembly 22 slides through the rebound chamber 20 as the piston 14 correspondingly slides within the cylinder 12. The midsection 34 has a diameter substantially smaller than the inner wall 64 of cylinder 12, thereby forming a substan¬ tially large annular gap 66 between lower section 68 and upper section 70 of the rebound chamber 20. The restric¬ tion between the sections 68 and 70 through gap 66 is significantly lower than the restriction through valved passages 15 in piston 14. The gap 66 consequently does not add any significant damping to the relative motion of the piston rod 16 and the cylinder 12 during no ' rmal vibrations. In other words, the assembly 22 does not interfere with the normal damping characteristics of the shock absorber 10 during the normal stroke range.

However, when the piston rod 16 approaches the end of its rebound stroke, the assembly 22 provides additional damping. The assembly 22 is moved upward through cylinder 12 until the protrusions 58 on collar 26 abut the rod guide

18. Further upward motion of the piston rod 16 causes shoulder 30 and rod guide 18 to axially compress the flexible ring 24. The deformation of the elastomeric ring 24 provides a certain amount of additional damping. The axial compression of ring 24 causes the outer diameter section 34 to enlarge and abut the inner wall 64 of the cylinder as shown in Figure 2. Free fluid communication between section 68 of the rebound chamber 20 and section 70 is interrupted by the closure of gap 66. Sections 68 and 70 become two separate chambers.

A restrictive passage 71 between chambers 68 and 70 is simultaneously formed. The upper portion 72 of the passage 71 is interposed between the upper surface 56 of collar 26 and the rod guide 18 between the circumferen- tially spaced protrusions 58. The annular gap 50 formed between the piston rod 16 and the inner wall 48 of collar 26 defines a second section of the passage 71. An annular chamber 74 formed between the collars 26 and 28 and between the piston rod 16 and the inner wall 40 of the flexible collar 24 defines a third section of the passage 71. The gap 50 between the inner wall 48 of collar 28 and the piston rod 16 defines a fourth section of the passage 72. A fifth section 75 of the passage is formed between the shoulder 30 and the outer surface 56 of the collar 28 between the spaced protrusions 58.

Further upward movement of the piston rod 16 is damped by a highly restrictive fluid flow out from chambers

70 and 74 and the additional compression " of elastomeric ring 24. The chamber 70 decreases in volume as the piston rod moves upwardly to compress the elastomeric ring 24. The fluid therein is forced through the restrictive passage

71 to chamber 68. In addition, the axial dimension of annular chamber 74 is shortened resulting in a decreased volume. The fluid within chamber 74 is also forced through the fourth and fifth sections of passage 71 to the chamber 68.

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The passage 71 allows a sufficient fluid flow fro chamber 74 to prevent the hydraulic fluid therein fro being excessively pressurized. Excessive pressure withi chamber 74 may separate the flexible elastomeric ring 2 from its collars 26 and 28. In other words, the passage 7 provides a mete ed flow from both chambers 70 and 74.

As the axial ends 54 of the collars come towar each other, a gap 75 therebetween narrows down. When th gap 75 becomes sufficiently narrow, it provides a restric tion to the remainder of passage 71 from chamber 74. Thi restriction decreases the flow from chamber 74 furthe increasing the damping of the shock absorber . Th decreased flow from - chamber 74 occurs only after th elastomeric ring 24 is deformed to be sufficiently thick t withstand the buildup of pressure within chamber 74.

If the rebound stroke is sufficiently strong to continue against the additional damping, the ends 54 of the collars 26 and 28 abut each other, as shown in Figure 3, and further axial compression of the elastomeric ring 24 is prevented. At this point, the piston rod 16 can no longer move upwardly. However, between the position as shown in Figure 1 and the position shown in Figure 3, the rebound stop assembly 22 provides high damping of the rebound stroke to soften any jarring impact which may otherwise occur when the piston rod is in the position shown in Figure 3. Alternatively, the rebound stop assembly 22 may altogether prevent any jarring impact by totally damping the stroke before the piston rod attains the position shown in Figure 3. Passage 71 may be alernatively arranged. Alterna¬ tives can include axially extending notches cut into the midsection 34 of the elastomeric ring 24 such that when midsection 34 abuts the inner wall 64 of the cylinder 12, the notches will form a restrictive passage and restrict flow from chamber 70 to section 68.

In this fashion, an easily manufactured rebound stop is possible which provides high damping capabilities as well as being economical to manufacture and easy to install on existing shock absorbers with minimal amount of modification. variations and modifications of the present invention are possible without departing from its scope and spirit as defined by the appended claims.

Industrial Applicability

This invention has industrial applicability to shock absorbers and provides a damping system for the shock absorber at the end of a stroke.

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