US2347302A - Power transmission - Google Patents

Description

April 25, 1944. L. R. TWYMAN ETAL 2,347,302

POWER TRANSMISSION Filed Aug. 26, 1940 2 Sheets-Sheet l .HI, 5' iii, a?

4 k INVENTORS 68 -L. RAYMGND TWYMAN 1 s Q2 JESSE R. MOSER & f-\ g OWARD E. OSE

66 BY 41 5O ATTORNEY April 25, 1944.

Filed Aug. 26 1940 2 Sheets-Sheet 2 I64 FIG.B

I T '/I mrl IJ I62 170 wal -gym,

ATTORNEY Ealented Apr. 25, 1944 POWER TRANSMISSION L. Raymond Twyman, Jesse R. Moser and Howard E. Bose, Detroit, Mich, assignors to Vlckers Incorporated, Detroit, Mich, a corporation of Michigan Application August 26, 1940, Serial No. 354,204

2 Claims.

This invention relates to power transmissions, particularly to those of the type comprising two or more fluid pressure energy translating devices one of which may function as a pump and another as a fluid motor.

The invention is more particularly concerned with a power transmission system for use in oil well pumping for operating the type of pump in which a sucker rod string is utilized in the well to operate the pumping plunger or barrel at the bottom of the well. Hydraulically operated well pumping units of this class have been known for many years and have recently come into more extensive use. Pumping units of this class provide many advantages over the conventional walking beam type of pump jack, among them being a greater length of stroke and consequent reduction in the pump losses due to stretching of the sucker rod as well as the advantage of more precisely controlled acceleration and deceleration at opposite ends of the stroke resulting in longer sucker rod life due to less violent shock imposed upon the sucker rod string at reversal.

Hydraulic pumping units of this class have heretofore been constructed with hydraulic counterbalancing means either of the air-loaded type or of the weight-loaded type. Where it is desired to operate the pump at relatively high speed, the air-loaded type presents some advantage permitting higher speed of reversal due to the lower inertia of the movin parts. One difficulty which the air-loaded type of counterbalance has heretofore presented is the high cost of providing air containers capable of holding the high pressures at which it is desirable to operate the hydraulic parts of the circuit. Present A. S. M. E. code regulations covering air pressure vessels require construction which is considerably more costly in the higher pressure ranges above 400 pounds per square inch so that considerable economy can be effected while complying with such code regulations if the apparatus can be designed for air pressures below this value. On the other hand, in the hydraulic parts of the mechanism an operating pressure of only 400 pounds necessitates more costly construction than is possible at higher pressures of the order of 1,000 pounds.

It is an object of the present invention to provide an improved well pumping system of the hydraulically counterbalanced type which permits the use of high pressure hydraulic power apparatus and medium pressure air containers thus permitting maximum economy of construction throughout the apparatus.

Another problem which has heretofore increased the cost of construction of hydraulic well" pumping apparatus has been the necessity of making up leakage losses in the hydraulic parts of the circuit as well as in the air chamber of the counterbalance mechanism.

It is an object of the present invention to provide an improved pumping system wherein replenishing of hydraulic fluid and of compressed air is readily accomplished by inexpensive mechanism and automatically throughout the continued operation of the device.

A further object is to provide a hydraulic well pumping apparatus with an improved means for adjusting the position 01 the sucker rod relative to that of the work piston in order to obtain maximum pumping efliciency in the pumping barrel at the bottom of the well.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the present invention is clearly shown.

In the drawings:

Figure 1 is a side view partly in section of an oil well pumping apparatus incorporating a preferred form of the present invention.

Figure 2 is a diagrammatic sectional view of the hydraulic power supplying means for the apparatus in Figure 1.

Figure 3 is a fragmentary sectional view showing the work piston on a larger scale.

Figure 4 is a cross section on line 4-4 of Figure 3.

Figure 5 is a cross section on line 5-5 of Figure 1.

Referring now to Figure 1, there ,is shown a well comprising a casing l0 having a pump l2 at the bottom thereof. The latter may be of any conventional type and, for example, may consist of a stationary barrel l4 having the usual check valve or standing valve It at the bottom and a reciprocable plunger l8 having the usual central passage 20 and check valve 22 at the bottom thereof. At the top of the well there is secured to the top of the casing a discharge head 24 having the usual outlet 28 for the discharge of the oil delivered by the well pump.

Positioned on top of the discharge head 24 is a cylinder head casting 34 having a connection 36 for hydraulic operating fluid extending into cylinder end chamber 38 at a point somewhat above the bottom thereof. A suitable spring-loaded relief valve 40 permits discharge of oil out of the chamber 38 to the connection 38 when the tral bore in the valve 44. whenever the velocity of flow from chamber 88 to connection 88 exceeds a predetermined value. This is merely a safety device and operates only in the event of a broken connection.

Rigidly mounted in the casting 84 is a long work cylinder 48 within which is slidably mounted a piston 48. The latter is slidably mounted for adjusting purposes on a sucker rod 88 which ex- .tends into the well and carries plunger I8 at its lower end. On top of the work cylinder 48 there is mounted a member 52 provided with two pairs of access doors, one pair above the other, and carrying at its upper end along cylindrical closure member 54 for protection of the upper end of the sucker rod 88. Suitable leakage drains are provided at 55, 88 and 58 and are connected by conduits 88 with the oil reservoir to be later described.

The construction of the piston 48 and its associated clamping mechanism is illustrated in Figures 3 and 4 from which it will be seen that the piston has a central bore 82 packed at 84 through which the sucker rod 58 extends. The piston is formed with one or more passages 88 at its lower end which communicate through a central chamber 88 with valved passages I8 normally closed by poppet valves I2. The latter have their operating stems connected to a ring-I4 above the piston and which is adapted to contact a shoulder at the bottom 01 the member 52 whenever the piston 48 is in its uppermost position as shown in the drawings. There is thus provided a passage between the upper and lower sides of piston 48 when valves 12 are open. As soon as the piston 48 is lowered slightly, the valves I2 will close by the action of their associated springs, thus effectively sealing this passage through the piston.

'I'he'piston 48 is provided with an upwardly extending sleeve I8, immediately above which is mounted a split clamp I8 on the sucker rod 58. Thus the sucker rod 58 is supported by means of the clamp I8 resting on the sleeve I8. Spaced above the clamp I8 is a second clamp 88 which during normal operation serves merely as a safety precaution to catch the sucker rod in the event of slippage of clamp I8. For the purpose of adjusting the sucker rod relative to the piston 48, the clamp 88 may be utilized as a temporary support for the sucker rod by inserting a U-shaped temporary support underneath the clamp 88 and resting on the bottom edges of the upper access doors in member 52. The clamp I8 may then be released and the piston" and clamp lowered to the desired extent after which the clamp I8 may be again tightened. Thereafter the piston 48 and sucker rod 58 may be raised together to release the weight of the rod from the temporary support, and clamp 88 may then again be adjusted to a position correspondingly spaced from the new position of clamp I8.

Mounted on a suitable base at one side of the well is a combined hydaulic power and air counterbalancing unit generally designated 82. The counterbalancing means comprises a vertical cylinder of considerably larger diameter but oi equal fluid displacement to that or the cylinder 48 and designated 84. Slidably mounted in the cylinder 84 is a piston having an upwardly extending rod 88 which extends through a packed opening in the upper cylinder head 88. The cylinder head 88 incorporates a connection 82 which communicates through a second velocity valve 84 with the space in cylinder 84 above piston 88. The connection 82 is connected to the work cylinder at connection 88 by a conduit 88. The space below piston 88 is adapted to contain air under pressure and connects by a conduit 88 with a larger air bottle I88. Suitable drain cocks are provided as shown for draining any condensate or oil leakage that may seep into the bottom of cylinder 84and air bottle I88.

It will be seen that th conduit 88 connecting work cylinder 48 and counterbalance cylinder 84 forms what is hereinafter. termed a secondary circuit" so that as piston 48 moves downwardly oil will be displaced from work cylinder 48 into the top of counterbalanced cylinder 84 thus providlng a single-acting liquid column connecting the pistons 48 and 88 for simultaneous movement. In this secondary circuit it will also be seen that the bottom face of piston 48 constitutes a work ram while the upper face of piston 88 constitutes a counterbalance ram.

The weight of the sucker rod 58 exerts a constant force tending to keep the work ram in contact with the liquid column beneath it while the air under pressure in bottle I 88 and the lower part of cylinder 84 exerts another constant force tending to keep the piston 88 moved upwardly into contact with the liquid column above it. Preferably the air pressure in cylinder 84 is maintained at a value where the upward force on piston 88 is greater than necessary to support the weight of sucker rod 58 but less than that necessary to lift that weight plus the Weight of the producing oil column standing above check valve 22 in the well. Under this condition it will be seen that the mechanism thus far described tends to hold piston 48 in any position which it should happen to rest since the weight of the sucker rod alone is unable to overcome the air pressure in cylinder 84, it being noted that standing valve I8 supports the weight of the producing oil column Likewise, there is no tendency to lift the work ram 48 because the pressure in cylinder 84 is insufficient to overcome the weight of both the sucker rod and the oil column in the well.

If the air pressure in cylinder 84 is maintained at an average value midway between that necesits pumping and return stroke, a separate power drive is provided for one of the two rams, in this case, the counterbalance ram. For this purpose the piston rod 88 carries a smaller piston I82 which is slidable in a smaller cylinder I84 carried on the end casting 88 of cylinder 84. The piston I82 and cylinder I84 thus constitute a double-acting hydraulic motor whereby the counterbalance ram 88 may be positively reciprocated by the admission to and exhaust of fluid from the opposite end of the cylinder I84.

Connections m and m in the head castings II and III, respectively, communicate by pipes H2 and H4 with the power supply connections H6 and H8 of a power fluid supply unit I28. The details of the unit I20 will be described hereafter in connection with Figure 2. For the present purposes it is sufllcient to state that the unit is adapted to deliver fluid alternately through connections H6 and H8 while at the same time withdrawing returning fluid through the opposite connections. The direction of fluid flow through the unit I20 is controlled by a lever I22 which is connected by a link I24 with a lever I26 pivoted in the end casting H0.

The piston rod 88 extends through the casting I I and is provided with a flange I28 at its upper end. The projecting upper end of piston 88 is enclosed in a housing I30 which also supports a sliding control rod I32 carrying flanges I34 and I36 at its upper and lower ends. At its extreme lower end the control rod I32 carries a flange I38 which coacts with the slotted end of lever I26 whereby the rod I32 may operate the latter. Thus when the piston rod 88 is at the upper limit of its stroke the flange I28 contacts flange I34 to lift the control rod I32 and depress the link I24. At the lower limit of the stroke the flange I28 contacts flange I36 to reverse the position of the control linkage members. Either or both of the flanges I34 and I36 may be adjustably mounted on the control rod I32 for changing the length of stroke of piston rod 88.

For the purpose of automatically and continuously replenishing the compressed air supply in bottle I00 the upper end of piston rod 88 car ries a plunger I48 adapted to enter an air compressor cylinder I42 secured to the top of casing I38. The length of cylinder I42 is somewhat shorter than the normal minimum stroke of piston rod 88 so that at the lower position of the latter the plunger I40 is completely out of the cylinder I42. A vent louver at I43 permits entry municates by a pipe I48 with the upper end of the air bottle I00. A suitable pressure gage I58 and blow-ofl cock I52 may be provided at the top of the bottle I08.

The plunger I48 is not rigidly secured to th piston rod 88 but is resiliently attached thereto by means of a compression spring I54 mounted between washers I56 which abut a nut and a shoulder, respectively, on the plunger I40. The upper end of rod is provided with a counterbore I58 closed by a cap I60, the arrangement being such that the plunger I40 may be moved downwardly relative to red 88 by any force sufflcient to overcome the force of the spring I54. The force of the spring is preferably so adjusted that the desired pressure of air in bottle I80 will overcome the force of the spring I 54. Thus there is provided a limit to the degree of compression of air in cylinder I42, and Whenever the pressure' in bottle I08 is at the desired value the plunger I48 will fail to compress the air in cylinder I42 to the value necessary to open check valve I46. Thus no air will be dis- 1 charged from cylinder I42, and the energy of compression of the air therein will be returned to the rod 88 on the expansion stroke. In this way it is automatically insured that the pressure i bottle I08 is maintained at the desired value regardless of leakage, but when no makeup of air is required, no energy is dissipated by the air recompression mechanism.

Referring now to Figure 2, the entire unit I28 is there illustrated and in the form disclosed comprises a fixed displacement unidirectional delivery pump I62 having a suction conduit I68 and a delivery conduit I10. Pump I62 may be drive by any suitable prime mover such as an electric motor I64 mounted on the outside of the casing I66 of the unit I20. The casing I66 forms a main oil reservoir as well as a support for the various .parts of the power unit.

The delivery conduit I10 leads to a three-way pilot control valve I12 which is manually controlled from outside the casing I66. In the position shown the valve I12 connects the delivery conduit with a bypass conduit I14 whereby the full delivery of pump I62 is returned to the reservoir. Whe the valve I12 is moved to the left the delivery conduit I18 is connected to a conduit I88 leading to the pressure port of a conventional four-way valve I82. The customary relief valve I84 may be provided in a branch extending from the conduit I88.

The tank ports of valve I82 connect by a conduit, I86 with the conduit I68 thus providing a closed return circuit to the suction side of pump I62. The conduit I68 at its bottom may be provided with a check valve I88 for replenishing purposes in the main power circuit. The cylinder ports of the four-Way valve I82 connect by conduits I98 and I92 with the supply connections H6 and H8. The spool of valve I82 is adapted to be shifted by pilot pressure admitted to the end chambers thereof through connections I94 and I86 which are controlled by a conventional four-way pilot valve I98. The latter is operated by the lever I22 previously described. The usual oriflcesand check valves 200 and 282 may be provided for controlling the speed of shifting of the spool of valve I82.

In order to provide replenishing oil for the secondary circuit a branch conduit 284 (Figure 1) extends from the conduit 96 into the tank I65 and is provided with a check valve 286 at its lower end. The latter serves merely to admit oil to the secondary circuit during the preliminary filling of the apparatus before it is started.

A bleed conduit 288 extends from the conduit I to the conduit 204 and incorporates a hydrostatic flow rate controlling valve 2I0 of conven tional construction and a check valve 2I2. The valve 2H. serves to control the rate of flow through conduit 288 to a predetermined constant volume depending upon the setting of the adjustable throttle 2I4 incorporated in the valve. The flow through bleed-off conduit 208 is also utilized as a source of pilot operating pressure for shifting the main reverse valve I82, and for this purpose a branch conduit 2I6 extends from conduit 204 to the pressure port of the pilot valve In operation, with the secondary and power circuits filled with oil and with the air bottle and counterbalance cylinder filled with air at the required pressure, the pump I62 may be started and the power control valve I12 shifted to its lefthand position.

Starting with the parts in the position illustrated, the oil delivered by pump I62 passes through conduits I18, I80 and I82 to connection 8 and continues through conduit 4 and connection I08 to the upper end of cylinder I04. Piston I82 is accordingly forced downwardly discharging oil from the lower end of cylinder I84 4- assasoa through connection I86, conduit 2, connection III, conduit I88, and conduits I88 and I 88 to the inlet side of pump I82. As piston I82 is driven downwardly, the force of the air pressure in the bottom of cylinder 84 is overcome permitting the weight'of the sucker rod to drive piston 48 downwardly thus transferring oil in the secondary circuit from work cylinder 48 to counterbalance cylinder 84.

As the piston I82 nears the bottom of its stroke, flange I28 contacts flange I" shifting the control rod I82, link I24 and lever I22 to shift pilot valve I28 to its opposite or righthand position. Pilot pressure is accordingly admitted to conduit 2I8, conduit I88, and through check valve 282 to the lefthand chamber of valve I82 shifting the spool of the latter to the right. Oil discharged from the righthand chamber returns to tank through conduit I84 and valve I88, being restricted inv its rate of flow, however, by the throttle 288. When the spool of valve I82 has 'shifted completely to the right the pressure oil from pump I82 is now directed in an opposite direction through the main power circuit beyond the valve I82.

Piston I82 is accordingly driven upwardly displacing oil from the counterbalance cylinder through conduit 88 into the work cylinder 46. Thus the sucker rod and the oil column supported on check valve 22 are lifted, and the oil is 80 discharged to pipe 26. As the piston I02 reaches the upper limit of its stroke flange I28 contacts flange I34 to shift the control linkage into the position illustrated and thus cause a reversal of piston I82 to repeat the cycle.

It will be noted that during a complete downward and upward cycle of movement of the piston circuit at a comparatively slow rate. Nevertheless, during this interval the quantity of oil in the secondary circuit was increased by a small amount so that the piston 48 will reach the top of its stroke before the piston 86 reaches the top of its stroke. As soon as piston 48 reaches the top the ring I4 will contact its shoulder and open valve I2 to bypass a small quantity of oil from the work cylinder into the drain connection 55. Thus it is insured that the secondary circuit is supplied with make-up fluid at a greater rate than necessary to make up for normal leakage, and any excess is automatically returned to the reservoir by the action of the replenishing relief valve I2.

Itwill be noted that the present apparatus utilizes but a single pump of inexpensive construction which may be of small size. In fact,

10 which admits of the most economical pump construction.

This feature of operating'the hydraulic power circuit at a higher pressure than the secondary circuit and air reservoir provides a further 16 economy in that it is unnecessary to provide a separate pump for replenishing the secondary circuit, or, alternatively. to provide mechanism for temporarily disrupting the pumping action periodically while permitting the main power 20 pump to replenish the secondary circuit.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the 25 claims which follow.

What is claimed is as follows:

1. A transmission system for a reciprocating oil well pump comprising hydraulic work ram means, an air-loaded hydraulic counterbalance ram, a closed coupling circuit connecting the counterbalance ram in free communication with the work ram means, a fluid pressure generating means, means forming a power circuit isolated from the coupling circuit and including said gen- 35 erating means, said power circuit including a double-acting fluid motor mechanically connected to said hydraulic counterbalance ram and driven by said generating means through said power circuit, and means controlled by the position of 40. the counterbalance ram for reversing the flow of fluid through said power circuit.

2. A transmission system for a reciprocating oil well pump comprising single-acting hydraulic work ram means, single-acting, air-biased, hydraulic counterbalance ram means, a closed couposition of the counterbalance ram.

L. RAYMOND 'I'WYMANL JESSE R. MOSER. HOWARD E. ROSE.

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