Electrically conductive pneumatic spring with door actuated switch means

Abstract

The pneumatic spring which holds the rear gate of a station wagon in the open position transmits electric current to heating filaments in the window of the rear gate by way of terminals on the piston rod and the cylinder of the spring, the terminals being connected by a contact spring in the cylinder cavity in the closed position of the rear gate.

I claim: 
     
       1. A pneumatic spring comprising: (a) a cylinder member having an axis and formed with a cavity;   (b) a piston assembly axially movable relative to said cylinder member between two end .[.postions.]. .Iadd.positions, .Iaddend.said assembly including (1) a piston axially separating two compartments in said cavity, and   (2) a piston rod member fixedly fastened to said piston and axially projecting from said cavity in sealing engagement with said cylinder member;     (c) a body of gas in said cavity and impeding axial movement of said piston assembly;   (d) fastening means on respective, oppositely spaced, axially terminal portions of said cylinder member and of said piston rod member outside said cavity for fastening said members to respective objects and including insulating means for electrically insulating said members from the respective fastened objects;   (e) respective electrically conductive terminals mounted on said cylinder member and on said piston rod member outside said cavity; and   (f) electrically conductive means in said cavity conductively connecting said terminals in one of said end positions of said piston assembly.   
     
     
       2. A pneumatic spring as set forth in claim 1, wherein said fastening means include respective fastening eyes of electrically insulating material. 
     
     
       3. A pneumatic spring as set forth in claim 1, wherein said cylinder member and said piston rod member have respective metallic portions, said fastening means each include an element of insulating material, and said terminals are secured under clamping pressure between respective ones of said metallic portions and of said elements, at least one of said terminals projecting radially beyond the associated member. 
     
     
       4. A pneumatic spring as set forth in claim 1, further comprising a coating of electrically insulating material covering substantially the entire surface of said cylinder member exposed outside said cavity. 
     
     
       5. A pneumatic spring as set forth in claim 1, further comprising a tubular body of electrically insulating material covering the portion of said piston rod member projecting from said cavity in each of said end positions. 
     
     
       6. A pneumatic spring as set forth in claim 1, wherein said conductive means include a resilient contact element in said cavity. 
     
     
       7. A pneumatic spring as set forth in claim 6, wherein said contact element is a substantially helical spring fastened to one of said members in said cavity. 
     
     
       8. A pneumatic spring as set forth in claim 1, further comprising switch means in said cavity for interrupting the electrically conductive connection of said terminals by said electrically conductive means in response to movement of said piston assembly into the other one of said end positions thereof. 
     
     
       9. A pneumatic spring as set forth in claim 8, wherein said conductive means include a resilient contact element in said cavity conductively connected to the one of said terminals mounted on said cylinder member, electrically insulating mounting means securing said contact element and said one terminal to said cylinder member, said piston assembly having an electrically conductive face engaging said contact element in said one end position of the piston assembly while being separated from said contact element by said gas in said other end position of said piston assembly, said contact element and piston assembly jointly constituting said switch means. 
     
     
       10. A pneumatic spring as set forth in claim 1, further comprising a source of electric current having two poles, and circuit means respectively connecting said terminals to said poles. .Iadd. 11. A pneumatic spring comprising: (a) a cylinder member having an axis and formed with a cavity;   (b) a piston assembly axially movable relative to said cylinder member between two positions, said assembly including a rod member axially projecting from said cavity;   (c) a body of gas at a pressure higher than atmospheric in said cavity for impeding axial movement of said piston assembly;   (d) fastening means on said cylinder member and on said rod member for fastening said members to respective objects;   (e) two electrically conductive terminals respectively secured to said cylinder member and to said rod member outside said cavity;   (f) two electrically conductive means respectively comprised at least in part by said members for conductively connecting said terminals in one of said positions of said piston assembly;   (g) insulating means for insulating said two terminals and said two conductive means from said objects. .Iaddend..Iadd. 12. A spring as set forth in claim 11, wherein said insulating means comprises means for insulating said members from the objects fastened thereto by said fastening means. .Iaddend..Iadd. 13. A spring as set forth in claim 11, wherein said fastening means include a fastening eye comprised at least in part of electrically insulating material on each of said members. .Iaddend..Iadd. 14. A spring as set forth in claim 11, wherein said cylinder member and said piston rod member have respective metallic portions, said fastening means each include an element of insulating material, and each of said terminals is secured under clamping pressure between one of said metallic portions and one of said elements, at least one of said terminals projecting radially outward beyond the associated member. .Iaddend..Iadd. 15. A spring as set forth in claim 11, further comprising a coating of electrically insulating material covering substantially the entire surface of said cylinder member exposed outside said cavity. .Iaddend..Iadd. 16. A spring as set forth in claim 11, further comprising a tubular body of electrically insulating material covering the portion of said piston rod member projecting from said cavity. .Iaddend..Iadd. 17. A spring as set forth in claim 11, wherein at least one of said conductive means includes a resilient contact element in said cavity. .Iaddend..Iadd. 18. A spring as set forth in claim 17, wherein said contact element is a helical spring fastened to one of said members in said cavity. .Iaddend..Iadd. 19. A spring as set forth in claim 11, further comprising switch means in said cavity for interrupting the electrically conductive connection of said terminals by said electrically conductive means in response to movement of said piston assembly away from said one position. .Iaddend. .Iadd. 20. A spring as set forth in claim 11, further comprising a source of electric current having two poles, and circuit means respectively connecting said terminals to said poles. .Iaddend..Iadd. 21. A spring as set forth in claim 11, wherein a portion of said piston assembly is fastened to said rod member in said cavity and slidably engages said cylinder member during said axial movement. .Iaddend..Iadd. 22. A spring as set forth in claim 11, wherein said fastening means are mounted on respective, axially terminal portions of said cylinder member and of said rod member. .Iaddend..Iadd. 23. A spring as set forth in claim 11, wherein said rod member sealingly engages said cylinder member during axial movement of said piston assembly between said positions. .Iaddend..Iadd. 24. A spring as set forth in claim 11, wherein said two electrically conductive means include respective parts thereof located in said cavity for establishing said conductive connection between said terminals. .Iaddend..Iadd. 25. A pneumatic spring comprising:   (a) a cylinder member having an axis and formed with a cavity;   (b) a piston assembly axially movable relative to said cylinder member between two positions, said assembly including a rod member axially projecting from said cavity in engagement with said cylinder member;   (c) a body of gas at a pressure higher than atmospheric in said cavity for impeding axial movement of said piston assembly;   (d) fastening means on said cylinder member and on said rod member for fastening said members to respective objects;   (e) two electrically conductive terminals respectively secured to said cylinder member and to said rod member outside said cavity;   (f) electrically conductive means located at least in part in said cavity for conductively connecting said terminals; and   (g) insulating means for insulating said terminals and said conductive means from said objects. .Iaddend..Iadd. 26. A spring as set forth in claim 25, wherein said insulating means comprises means for insulating one of said terminals and one of said conductive means from one of said members, said one terminal and said one conductive means being secured to said one member. .Iaddend..Iadd. 27. A spring as set forth in claim 25, wherein said conductive means include a resilient contact element in said cavity conductively connected to the terminal secured to said cylinder member, electrically insulating mounting means securing said contact element and the connected terminal to said cylinder member, and an electrically conductive face on said piston assembly engaging said contact element in said one position of the piston assembly while being spaced from said contact element in said other position of said piston assembly. .Iaddend..Iadd. 28. A spring as set forth in claim 25, wherein said cylinder member and said piston assembly have respective electrically conductive portions conductively connected to said terminals, said electrically conductive means in said cavity include a contact member secured to one of said electrically conductive portions and engaging the other electrically conductive portion during at least a part of the movement of said piston assembly between said two positions. .Iaddend..Iadd. 29. A spring as set forth in claim 25, wherein said cylinder member and said rod member have respective end portions axially remote from each other, said fastening means and said terminals being mounted on said end portions. .Iaddend..Iadd. 30. A pneumatic spring comprising:   (a) a cylinder member having an axis and formed with a cavity;   (b) a piston assembly axially movable relative to said cylinder member between two positions, said assembly including a rod member axially projecting from said cavity;   (c) a body of gas under a pressure higher than atmospheric in said cavity for impeding axial movement of said piston assembly;   (d) fastening means on said cylinder member and on said rod member for fastening said members to respective objects;   (e) electrically conductive means respectively secured to said members for conductive connection with each other during at least a part of the relative movement of said members; and   (f) insulating means for insulating said conductive means from said objects. .Iaddend..Iadd. 31. A spring as set forth in claim 30, further comprising a coating of electrically insulating material covering substantially the entire surface of said cylinder member exposed outside said cavity. .Iaddend..Iadd. 32. A spring as set forth in claim 30, further comprising a tubular body of electrically insulating material covering the portion of said rod member projecting from said cavity. .Iaddend..Iadd. 33. A spring as set forth in claim 30, wherein said conductive means include a resilient contact element in said cavity. .Iaddend..Iadd. 34. A spring as set forth in claim 33, wherein said contact element is a helical spring fastened to one of said members. .Iaddend..Iadd. 35. A spring as set forth in claim 30, wherein said piston assembly further includes a sliding member fastened to said rod member in said cavity and slidably engaging said cylinder member during axial movement of said piston assembly. .Iaddend..Iadd. 36. A spring as set forth in claim 35, wherein said sliding member is a piston. .Iaddend..Iadd. 37. A spring as set forth in claim 30, wherein said fastening means are mounted on respective, axially terminal portions of said cylinder member and of said rod member. .Iaddend..Iadd. 38. A spring as set forth in claim 29, wherein said rod member movably engages said cylinder member in sealing engagement. .Iaddend..Iadd. 39. A spring as set forth in claim 29, wherein said electrically conductive means are secured to said members in said cavity. .Iaddend. .Iadd. 40. A spring as set forth in claim 30, wherein said circuit means include an electric heater. .Iaddend..Iadd. 41. A spring as set forth in claim 30, wherein said insulating means include means for electrically insulating at least one of said members from an object fastened to said one member by the fastening means on said one member..Iaddend.