US1739675A - Pump dynamometer - Google Patents

Description

'73. MEASURING AND TESTING Dec. 17, 1929. HOWARD T AL 1,739,675

PW? DYNAMOMETER Filed Jan. 10. 1928 JOHN H. H0 WARD K j HALM/V /v. MARSH INVENTORS ATTUPNEY Patented Dec. 17, 1929 UNITED STATES PATENT OFFICE JOHN H. HOWARD, OF WALNUT PARK, AND HALLAN MARSH, 01? LOS ANGELES, CALIFORNIA PUMP DYNAMOMETER Application filed January 10, 1928. Serial No. 245,703.

Our invention relates to the art of testing with especial reference to the determination of the tension in pump rods used in pumping oil wells.

In general the object of our invention is to provide a device which furnishes a means of studying the peculiarities of the tenslon existing in rods subjected to a reciprocatory motion at all points in the cycle; for instance,

the sucker rods used in pumping oil wells. More specifically our object is to provide a device which automatically plots the tension existing in the sucker rods as a function of their cycle position. By proper design of the apparatus this curve Will be a closed figure Whose area is proportional to the work per cycle. Such a graph is useful in two ways (a) it furnishes a means of determining the power input to the sucker rods, know ng Which the efiiciency of the surface pumplng equipment can be determined and (b) the exact part of the cycle at which any pecullarities of force occur is shown directly, furnishing a means for studying such peculiarities and correcting them by experiment, in much the same manner as the valve setting in a steam engine is corrected by reference to indicator cards.

l/Ve attain this object by the mechanism illustrated in the accompanying drawing, in which Figure 1 is an elevation of our invention as applied to a pumping oil Well, and

Figure 2 is a view on the line A-A in Figure 1.

The manner of causing the sucker rods to reciprocate is no part of our present invention but to clearly illustrate its application to a pumping well the description of a very common practice of doing this is given.

Referring to Figure 1, a so-called pump adjuster consisting of two similar side bars designated by numeral 1 depend, one on each side, from a walking beam, not shown. The manner of attachment to the walking beam is common knowledge to those skilled in the art of pumping. Pivoted in the ends of side bars 1 is a saddle 2 containing a central aperture through which the polish rod 3 extends. 50 A polish rod clamp at of any suitable type rests on saddle 2 and transmits the forces from it to the polish rod. The polish rod is shown as entering any usual or preferred type of stufling box and casing head generally designated by numeral 5.

In the application of our invention the lever unit generally designated by numeral 6 is inserted between the polish rod clamp 4 and the pump adjuster saddle 2. Obviously the forces between the clamp and saddle are transmitted through the lever unit. The lever unit consists of a lower lever 7 resting on the saddle 2 and an upper lever 8 spaced directly above the lower lever and supporting the polish rod clamp on a knife edge '9. The levers can be made of any desired shape or material known to the art, the preferred construction shown in Figure 2 consisting of two channel sections 10 placed back to back and spaced far enough apart to allow the polish rod to pass between them. Transverse movement of the levers with respect to the polish rod is prevented by bolts 11 which pass through the levers, one on each side of the polish rod. The two levers 7 and 8 are substantially hinged together at one end by means of the pin 12 which is perpendicular to the polish rod and to the plane containing the two levers, and the lugs 13 and 14.. A diaphragm unit generally designated by numeral 15 is secured to the upper lever, positioned between the levers and at the opposite end from the pivot 12.

The diaphragm unit 15 is an old device consisting essentially of a rigid housing 16 made in two similar halves with a flexible diaphragm 17 clamped between them. A substantially rigid plate 18 is pressed against one side of the diaphragm by a central pin 19 projecting through the wall of the lower half of housing 16, this pin terminating in a knife edge bearing against a steel plate 20 which is secured to the lower lever 7 by means not shown. The space between the diaphragm and the top half of the housing 16 is filled with liquid, which is transmitted to and from the cylinder of any suitable indicator capable of producing a closed curve, generally designated at 21, by the flexible metallic hose 22.

The drum 23 of the indicator is rotated in synchronism with the strokes of the polish rod by any of several well known means. A suitable means for rotating the drum is a light cord 28 Wound around the lower portion of the drum and extending to any projection 29 from the sad dle 2, the cord passing over light frictionless idlers indicated at 30-30, which may be attached to any fixed portion of the apparatus, the vertical motion of the saddle and the rod to which it is attached being thus transmitted into an oscillating synchronous motion of the drum. A pump indicated at 24 and valve 25 are for the purpose of keeping the diaphragm unit, flexible hose and connections filled with fluid. The accuracy of results is dependent on this, as air leakage or too little or too much fluid will give erroneous results.

Valve 26 is used to isolate the indicator should such need arise.

In operation the tension in the rod divides in a definitely known ratio between the pin 12 and diaphragm unit 15, this division depending solely on the proportionate lengths of the lever arms. The fluid pressure on the diaphragm is directly proportional to the pressure exerted by the spring in the indicator, hence any change in the tension in the polish rod causes a slight movement of the diaphragm, the spring in the indicator establishing the correct pressure for equilibrium. The movement of the indicator pointer 27 is thus a measure of the tension in the polish rod. Obviously by taking a chart on the drum of the indicator a curve will be obtained whose ordinates are polish rod tensions and whose abscissa are the position in the stroke.

By sustaining the polish rod on top of the stufling box by use of another polish rod clamp and then lowering the pump adjuster until the lever unit is relieved of all rod Weight, the zero position of the indicator pointer can be determined. Due to the relatively large area of the diaphragm as compared to the area of the piston in the indicator a very small deflection of the diaphragm is all that is necessary to fully extend the piston in the indicator. This provides a large amount of leeway in filling the system with fluid; it also increases the accuracy of the apparatus because (1) the diaphragm can be operated at its central position and (2) friction and inertia of heavy parts is practically eliminated.

We claim as our invention:

1. A device for measuring the tension in a reciprocating rod, comprising: leverage means responsive to the tension in said rod; means for creating a fluid pressure proportionate to said tension; means for transmitting said tension to said fluid pressure means, and means for measuring said pressure.

2. A device for measuring the tension in a reciprocating rod, comprising: a pair of levers hinged together at one end so attached to said rod as to be responsive to the tension in said rod; means for creating a fluid pressure proportionate to the forces transmitted by said levers, and means for measuring said pressure.

3. A device for measuring the tension in a reciprocating rod, comprising: leverage means responsive to the tension in said rod; a fluid pressure creating means comprising a flexible diaphragm covered on one side by a rigid case filled with fluid, said case being secured to one lever of. the leverage means; a pin bearing'centrally on said diaphragm and bearing against the oppositelever of said leverage means, the pressure of said fluid acting through said diaphragm against said pin balancing the forces acting between the levers of said leverage means; and means for measuring the pressure created in said fluid pressure creating means.

4. A device for producing a graph, the ordinates of which are. proportinate to the tension in a reciprocating rod and the abscissa of which are proportionate to the cycle position of said rod; comprising: a reciprocating rod under variable tension; leverage means adapted to transmit said tension to a means for creating a fluid pressure proportionate to said tension, and means for measuring and for simultaneously recording said pressure on a chart moved in synchronism with said rod, and means for moving said chart in synchronism with said rod.

5. A device for producing a graph, the ordinates of which are proportionate to the tension in a reciprocating rod and the abscissa of which are proportionate to the cycle position of said rod, comprising: a reciprocating rod under variable tension; 2. pair of levers hinged together at one end, and adapted to transmit a definiteportion of the tension in the rod; a means forcreating a fluid pressure proportionate to the forces transmitted to said means by said levers; means for measuring and for simultaneously recording said pressure on a chart, and means for moving said chart in synchronism with said rod.

6. A device for producing a graph, the ordinates of which are proportionate to the tension in a reciprocating rod and the abscissa of which are proportionate to the cycle position of said rod, comprising: a reciprocating rod under variable tension; leverage means responsive to said tension, a flexible diaphragm covered on one side by a rigid case filled with fluid, said case being secured to one lever of the leverage means; a pin bearing centrally on saiddiaphragm and bearing against the opposite lever of the leverage means, the pressure of said fluid acting through said diaphragm against said pin balancing the forces acting between the levers 75. MEASURING AND TESTING of the leverage means; means for measuring and for simultaneously recording said pressure on a chart, and means for moving said chart in synchronism with said rod.

7 A device for producing a closed graph whose ordinates are proportionate to the tension in a well pumping rod and whose abscissa are proportionate to the cycle position of said rod, comprising: a pair of hinged levers interposed between the rod actuating means and the rod gripping means; a diaphragm means for creating a fluid pressure proportionate to the tension in said rod and means for transmitting said pressure to an indicator, the drum of said indicator being oscillated in synchronisin with the motion of said rod to produce a closed graph, and means for oscillating said drum in synchronism with said rod.

In witness that we claim the foregoing we have hereunto subscribed our names this 4th day of January, 1928.

JOHN H. HOWARD. HALLAN N. MARSH.

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