The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 13, 1997
Filed:
Jun. 07, 1995
James Chamberlin, Charlotte, NC (US);
AVM, Inc., Marion, SC (US);
Abstract
A pneumatic counterbalance spring includes a hollow cylinder defining a first internal chamber divided into a compression compartment and an extension compartment by a piston movably mounted in the chamber. The compression compartment contains pressurized gas and a seal assembly mounted on the piston prevents the gas from escaping into the extension compartmint. A piston rod is slibably mounted in the open end of the cylinder and has its inner end connected to the piston. The piston rod includes a hollow portion defining a second internal chamber which is fluidly connected to the compression compartment by a flow passage. As a result, the compression compartment has an effective volume of A+B, where A represents the volume of the compression compartment and B represents the volume of the piston rod internal chamber. This design is advantageous in applications where a low spring rate is desired and where the length of the spring needs to be minimized. A gas permeable insert may be positioned in the flow passage to provide restricted rate flow of gas through the flow passage. Alternatively, a check valve may be provided for providing restricted rate flow of gas through the flow passage during the extension stroke and a tree, by-pass flow of gas through the flow passage during the compression stroke.