# US 5,706,920 A · Monotube damper > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,706,920 A - Document ID: US5706920A - Status: Granted - Kind: A - Application number: 08/698,412 - Filed: 1996-08-15 - Granted: 1998-01-13 - Earliest claimed: 1996-08-15 - Assignees: General Motors Corporation - Inventors: James Mitchell Pees; George Thomas Claude; Joel Ray Wells; Claude H. Cheatham - Web page: https://patentgrep.com/patent/US5706920A ## CPC - F16F 9/38: Covers for protection or appearance - F16F 9/3485: {characterised by features of supporting elements intended to guide or limit the movement of the annular discs (F16F9/3488 takes precedence)} - F16F 9/362: {Combination of sealing and guide arrangements for piston rods (F16F9/361, F16F9/365 take precedence)} - F16F 9/368: {Sealings in pistons} - F16F 9/49: Stops limiting fluid passage, e.g. hydraulic stops {or elastomeric elements inside the cylinder which contribute to changes in fluid damping (fluid-actuated displacement devices with means for accelerating or decelerating the stroke F15B15/22)} - F16F: SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION ## Abstract A suspension damper of the monotube gas charged shock type includes mating piston and rod guide assemblies and mating piston and gas cup assemblies wherein the extension and compression travel of the damper is maximized. The piston includes an annular skirt with a lower rebound cutoff element. The rod guide assembly includes twin spaced apart bushing assemblies providing lateral support to the piston rod, a lower annular leg and an upper rebound cutoff element. When the damper is in a fully extended position, the lower annular leg is received within the upper rebound cutoff element and the upper rebound cutoff element is received within the annular skirt of the piston assembly. ## Claims ### Claim 1 A monotube damper comprising: a cylindrical tube; a piston sealingly and slidably carried within the cylindrical tube, the piston separating the cylindrical tube into extension and compression chambers; a piston rod connected to the piston and extending therefrom; a rod guide assembly surrounding the piston rod and including a one piece rod guide body with a lower annular leg with a hub and an upper annular skirt; a lower bushing supporting the piston rod and carried by the hub; and an upper bushing spaced away from the lower bushing, supporting the piston rod and carried within the upper annular skirt. ### Claim 2 (depends on 1) A monotube damper according to claim 1 wherein the cylindrical tube includes an upper end formed closed with an annular leg and a radial groove together capturing the rod guide assembly in an aligned orientation wherein the radial groove is rolled simultaneously while the upper end is formed closed with the annular leg. ### Claim 3 A monotube damper comprising: cylindrical tube: a piston sealingly and slidably carried within the cylindrical tube, the piston separating the cylindrical tube into extension and compression chambers: a piston rod connected to the piston and extending therefrom: a rod guide assembly surrounding the piston rod and including a one piece rod guide body with a lower annular leg with a hub and an upper annular skirt: a lower bushing supporting the piston rod and carried by the hub; an upper bushing spaced away from the lower bushing, supporting the piston rod and carried within the upper annular skirt; and an outer seal assembly contacting the rod guide and positioned outside the upper bushing and an inner seal assembly contacting the rod and positioned inside the upper bushing; wherein the cylindrical tube includes an upper end formed closed with an annular leg and a radial groove together capturing the rod guide assembly in an aligned orientation and wherein the damper includes a maximized active travel length due to a mating overlap of the rod guide assembly with the piston. ### Claim 4 A monotube damper comprising: a cylindrical tube; a piston sealingly and slidably carried within the cylindrical tube including an annular skirt and a lower rebound cutoff element, the piston separating the cylindrical tube into extension and compression chambers; a piston rod connected to the piston and extending therefrom; and a rod guide assembly surrounding the piston rod and including a lower annular leg with a hub and an upper rebound cutoff element wherein when the damper is in a fully extended position the lower annular leg is received within the lower rebound cutoff element the lower rebound cutoff element is received within the upper rebound cutoff element and the upper rebound cutoff element is received within the annular skirt of the piston. ### Claim 5 (depends on 4) A monotube damper according to claim 4 wherein when the damper is approaching the fully extended position a gap exists between the upper rebound cutoff element and the lower rebound cutoff element through which fluid is allowed to flow, the gap reducing in size as the damper further approaches the fully extended position. ### Claim 6 (depends on 5) A monotube damper according to claim 5 wherein the upper rebound cutoff element includes an annular configuration with a cylindrical wall having a first diameter and having a flared out lower end, the lower end having a second diameter larger than the first diameter. ### Claim 7 (depends on 4) A monotube damper according to claim 4 wherein the rod guide assembly includes a first bushing and a second bushing spaced apart from the first bushing wherein each bushing engages the piston rod and supplies lateral support to the piston rod. ### Claim 8 (depends on 4) A monotube damper according to claim 4 wherein the piston has a body that includes a base and an annular skirt together forming an annular cavity that is open to the extension chamber wherein the base is secured to the piston rod with a valve assembly carried about the piston rod within the annular cavity. ### Claim 9 (depends on 8) A monotube damper according to claim 8 wherein the piston is secured to the piston rod such that a portion of the piston rod extends through a piston base and into the compression chamber and further comprising a gas cup slidably and sealingly carried in the cylindrical tube separating a compensation chamber off from the compression chamber. ### Claim 10 (depends on 9) A monotube damper according to claim 9 wherein the gas cup includes a rim and a cup element that spans across the cylindrical tube and includes an opening adjacent the compression chamber that is capable of receiving the portion of the piston rod that extends through the piston base and into the compression chamber such that the piston base is engageable with the rim. ### Claim 11 A monotube damper comprising: a cylindrical tube; a piston sealingly and slidably carried within the cylindrical tube including an annular skirt and a lower rebound cutoff element, the piston separating the cylindrical tube into extension and compression chambers; a piston rod connected to the piston and extending therefrom; a bearing washer positioned around the piston rod adjacent the lower rebound cutoff element; and a rod guide assembly surrounding the piston rod and including a lower annular leg with a hub and an upper rebound cutoff element wherein when the damper is in a fully extended position the lower annular leg is received within the lower rebound cutoff element, the lower rebound cutoff element is received within the upper rebound cutoff element, the upper rebound cutoff element is received within the annular skirt of the piston and the bearing washer is contactable with the lower annular leg providing a positive stop. ### Claim 12 A monotube damper comprising: a cylindrical tube; a piston sealingly and slidably carried within the cylindrical tube including an annular skirt and a lower rebound cutoff element, the piston separating the cylindrical tube into extension and compression chambers; a piston rod connected to the piston and extending therefrom; and a rod guide assembly surrounding the piston rod and including a one-piece rod guide body having a lower annular leg with a hub, and having an upper annular skirt offset outwardly and upwardly from the lower annular leg, and, the rod guide assembly including an upper rebound cutoff element, wherein when the damper is in a fully extended position the lower annular leg is received within the lower rebound cutoff element the lower rebound cutoff element is received within the upper rebound cutoff element and the upper rebound cutoff element is received within the annular skirt of the piston. ### Claim 13 (depends on 12) A monotube damper according to claim 12 wherein the upper rebound cutoff element includes an annular base wall fixed to the rod guide body and a downwardly extending cylindrical wall with a flared-out end. ### Claim 14 (depends on 12) A monotube damper according to claim 12 wherein the piston includes a bearing washer and a valve assembly, and wherein the lower rebound cutoff element includes an annular base wall captured between the bearing washer and the valve assembly, and wherein the lower rebound cutoff element includes an upward extending cylindrical wall. ### Claim 15 (depends on 12) A monotube damper according to claim 12 wherein the piston includes an annular cavity carrying a bi-directional monodisc valve assembly and a bearing washer wherein the lower rebound cutoff element is captured between the valve assembly and the bearing washer and wherein the bearing washer is contactable with the lower annular leg of the rod guide assembly to limit travel. ### Claim 16 (depends on 12) A monotube damper according to claim 12 further comprising a first seal assembly and a second seal assembly secured between an annular leg of the cylindrical tube and a ledge of the rod guide body, wherein the first and second seal assemblies carry resilient elements that are positioned on opposite sides of an upper bushing. ### Claim 17 (depends on 16) A monotube damper according to claim 16 further comprising a lower bushing carried by the lower annular leg and spaced away from the upper bushing. ### Claim 18 (depends on 17) A monotube damper according to claim 17 wherein the first seal assembly includes a first seal retainer, wherein the upper bushing is positioned concentrically inside the first seal retainer. ### Claim 19 (depends on 18) A monotube damper according to claim 18 wherein the second seal assembly includes a second seal retainer that extends further radially inward than the first seal retainer so that the upper annular bushing engages both the first and the second seal retainers.