Patent ID: 7406887

Claim:
A pumping unit for actuating a down hole pump including a post extending upwardly from the earth's surface, a walking beam connected at a saddle bearing pivot point to the post, said pumping unit having a pumping cycle including successive upward work strokes and downward return strokes at a forward end of said walking beam forming a pump stroke length, comprising: a gear reducer mounted on said walking beam at a location displaced from said saddle bearing pivot point and having a drive shaft extending therefrom; a crank arm rotatably mounted at one end to said drive shaft; a pitman rod rotatably connected at a first end to said crank arm; a rearward end of said walking beam having fixedly mounted thereon a counterweight, said crank arm being mounted for unidirectional rotational movement about an axis intermediate said pivot point and said counterweight, said forward end of said walking beam being operably connected to said pump by sucker rods substantially counterbalanced by said counterweight and said gearbox, a second end of said pitman rod having a selectable pitman rod bearing support position relative to said post by which the relationship of said upward work stroke and said downward return strokes of said walking beam can be adjustably selected; and a prime mover connected to supply power to said gear reducer.