A shock absorber for the pumping unit of an oil well, adapted to be placed between the walking beam and a string of sucker rods in the borehole. The shock absorber has a tubular body of steel (or an equivalent structural material) having a closed top and an open bottom. A circular top on the tubular...http://www.google.com.au/patents/US4445674?utm_source=gb-gplus-sharePatent US4445674 - Shock absorber for an oil well pumping unit
