Shock absorber for an oil well pumping unit

Claim 1

A shock absorber for use with an oil well pumping unit having a horizontal hanger bar suspended by cables, and there being a vertical polished rod having its lower end connected to a string of sucker rods for actuation of a pump in the borehole, and the hanger bar having an opening through which the polish rod extends, comprising: (a) a tubular body having a closed top and an open bottom, and the top having a central opening through which the polished rod passes; (b) a rigid spool having a central opening which is significantly larger than the diameter of the polished rod, such that the polished rod may pass through said central opening without any risk of establishing rubbing contact with the inner surface of said spool, and the lower face of said spool being configured so as to rest on top of the hanger bar; (c) a circular plate having a diameter slightly less than the internal diameter of the tubular body, and the plate having a central opening which is sufficiently large as to preclude interference with the polished rod, and the plate having an upper surface which is substantially flat and a lower surface which is configured to rest on top of the spool; (d) a plurality of elastomeric discs positioned in a stack within said tubular body, and each disc having an external diameter slightly less than the internal diameter of the tubular body, and each disc having an axial opening for receiving the polished rod, and the height of the stack of elastomeric discs in their uncompressed condition being approximately the same as the height of the tubular body, and the combined height of the rigid spool and the stack of compressed discs being more than the height of the tubular body when the discs are fully compressed within said tubular body, whereby the bottom edge of the tubular body is prevented from making contact with the hanger bar when a downwardly directed load is placed on the top of the tubular body by the polished rod.