Cylinder tube strain measurement feedback for piston position control

• US 4,700,610 A
• Filed: 09/16/1985
• Issued: 10/20/1987
• Est. Priority Date: 09/17/1984
• Status: Expired due to Fees

• Current Assignee: Hoerbiger Ventilwerke Aktiengesellschaft
• Original Assignee: Hoerbiger Ventilwerke Aktiengesellschaft
• Inventors: Bauer, Friedrich, Kuhnelt, Herbert
• Primary Examiner(s): Garrett, Robert E.
• Assistant Examiner(s): Kapsalas, George
• Application Number:
  US06/776,587
• Time in Patent Office: 764 Days
• Field of Search: 91/1, 91/361, 91/363 R, 91/364, 91/275, 91/459, 91/370, 91/390, 91/471, 91/420, 91/433, 92/5 R, 73/9, 60/327, 318/645, 318/646, 318/433
• US Class Current: 91/390
• CPC Class Codes: F15B 9/03 with electrical control means F15B9/07, F15B9/09, F15B9/17 take precedence

Abstract

A fluid cylinder control method for monitoring the position or controlling the movements of a piston which is slidably guided in a cylinder tube and is acted upon on at least one side by a pressure medium, in particular, maintaining the piston in a predetermined position against the action of eventual disturbance forces. This is attained in that the force which is transmitted between the piston and the cylinder by way of the parts which are slidingly guided on each other, and in particular the friction force acting by way of the seal gaskets of the piston and/or of the rod, is measured and the loading of the piston by a pressure medium is varied in the sense of reducing the measured force.

Claims

1. In a fluid cylinder which includes a cylinder and a cooperating piston, said cylinder including cylinder tube and opposite first and second end covers, said second end cover including a bore therethrough and a rod gasket extending inwardly of said bore;

said piston including a piston head which is slidingly movable within said cylinder tube and a piston rod which is connected to said piston head and extends through said bore in said second end cover so as to contact said gasket therein, said piston head including at least one piston seal gasket which contacts said cylinder tube, said piston head defining a first pressure chamber in said cylinder between said piston head and said first end cover and a second pressure chamber between said piston head and said second end cover, a method for maintaining the piston head at a predetermined position along said cylinder tube, said method comprising the steps of

(1) sensing the axial force of said cylinder tube acting toward said first end cover due to the frictional force acting thereon by said piston seal gasket(s) and said rod gasket prior to movement of said piston within said cylinder tube,

(2) sensing the axial force of said cylinder tube acting toward said second end cover due to the frictional force acting thereon by said piston seal gasket(s) and said rod gasket prior to movement of said piston within said cylinder tube,

(3) comparing the sensed axial forces in steps (1) and (2) to determine which force is larger and thus determine in which axial direction within said cylinder said piston head is about to move, and

(4) supplying pressure medium to either said first pressure chamber or said second pressure chamber to normalize said sensed forces and thereby maintain said piston head in its predetermined position along said cylinder tube.

2. The method as defined in claim 1, wherein the sensing of the axial force of said cylinder tube in step (1) is accomplished at a point around said cylinder tube adjacent said first end cover and the sensing of the axial force of said cylinder tube in step (2) is accomplished at a point around said cylinder tube adjacent said second end cover.

3. The method as defined in claim 1, wherein the sensing of the axial force of said cylinder tube in step (1) is accomplished at a point between said cylinder tube and said first end cover and the sensing of the axial force of said cylinder tube in step (2) is accomplished at a point between said cylinder tube and said second end cover.