GB2090925A

GB2090925A - Pump jack drive apparatus

Info

Publication number: GB2090925A
Application number: GB8136696A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-12-15
Filing date: 1981-12-04
Publication date: 1982-07-21
Also published as: CA1164270A; AR231666A1; JPS57124081A; AU7821781A; BR8108061A; AU559964B2; DE3148563A1; GB2090925B

Abstract

A pump jack drive apparatus includes a pair of hydraulic cylinders 15, 16 connected to a walking beam of the pump jack for reciprocating the horsehead 10, and a pair of microswitches, or proximity switches which are closed by the walking beam at the limits of the stroke thereof for controlling such stroke. The cylinders are driven and controlled by a pump and control unit which includes a valve for feeding hydraulic fluid to one or the other of the hydraulic cylinders, a control cylinder for controlling the valve, and two solenoid operated control valves for controlling movement of the control cyclinder in response to closing of the switches by the walking beam. <IMAGE>

Description

SPECIFICATION Pump jack drive apparatus This invention relates to a pump jack drive apparatus, and in particular to an apparatus for driving and controlling the speed of operation of a pump jack.

The pumping of heavy oils presents certain problems. If such problems can be overcome, the production of heavy oils can be substantially increased. There are presently available a number of forms of pump, alternative to the pump jack, for pumping oil. Because of their unreliability and expense, such pumps have not replaced the conventional pump jack in oilfields.

However, the motion of the walking beam of a conventional pump jack is derived from a rotating eccentric. The stroke cycle is thus normally fixed to give a beam motion ("stroking profile") that is substantially simple harmonic in character. In consequence, if the speed of the eccentric is varied, so also are the accelerations of the beam motion, in a way that can be detrimental to pumping efficiency. In the production of heavy oils, it would be advantageous to be able to change both the rate of pumping and the stroking profile independently, so as, for example, to be able to maintain the rate of pumping constant at a predetermined level while adapting the stroking profile to changing circumstances.

Because of the relatively low production rates of heavy oil, the equipment used to control pumping with a pump jack should be inexpensive and reliable. The object of the present invention is to meet such demands by providing a relatively simple, inexpensive apparatus for driving and controlling operation of a pump jack.

In its broadest aspect, the invention provides a driving apparatus for a pump jack including a samson post, a walking beam pivotally mounted on the samson post for rotation around a horizontal axis, and a horsehead on one end of the walking beam for driving connection to a pump mechanism, the driving apparatus comprising driving piston and cylinder means articulated to said samson post and to the walking beam at a position displaced from said horizontal axis; and control means for operating said piston and cylinder means to cause motion of the walking beam to reciprocate said horsehead upwardly and downwardly, with independent control of the upward and downward movements, respectively.

The driving piston and cylinder means may be a double-acting piston and cylinder assembly or a pair of single-acting piston and cylinder assemblies, the latter arrangement being preferred with the respective assemblies acting on the walking beam at opposite sides of the said horizontal axis.

The invention also provides a driving apparatus for a pump jack of the type including a samson post, a walking beam pivotally mounted on the samson post for rotation around a horizontal axis, and a horsehead on one end of the walking beam for driving connection to a pump mechanism, the driving apparatus comprising first driving piston and cylinder means pivotally mounted on said samson post and pivotally connected to said walking beam on one side of said horizontal axis for moving said one end of said walking beam upwardly; second driving piston and cylinder means pivotally mounted on said samson post and pivotally connected to said walking beam on the other side of said horizontal axis for moving said one end of said walking beam downwardly; and control means for alternately operating said first and second piston and cylinder means independently of each other, whereby one end of the walking beam and said horsehead are reciprocated upwardly and downwardly, the upward and downward movements being at the same or different speeds.

Preferably said control means includes pump means; switch means operated by said walking beam at the top and bottom limits of the stroke thereof; valve means for directing hydraulic fluid from said pump means to said piston and cylinder means selectively to effect upward and downward movement of the horsehead respectively; and control piston and cylinder means for actuation by said switch means for controlling said valve means and consequently the flow of hydraulic fluid to said driving piston and cylinder means.

In one embodiment said valve means includes a variable displacement pump for feeding hydraulic fluid to said piston and cylinder means; a main pump for supplying hydraulic fluid to said variable displacement pump; means connecting said control piston and cylinder means to said variable displacement pump; and control valves operatively connected to said switch means for controlling operation of said control piston and cylinder means and consequently the feeding direction of said variable displacement pump.

However in an alternative embodiment a fixed displacement pump may be used to supply hydraulic fluid directly to said valve means; control valves operatively connected to said switch means for controlling operation of said control piston and cylinder means; and a main pump for supplying hydraulic fluid to said control means and said control piston and cylinder means.

The invention will now be described in greater detail with reference to the accompanying drawings, which illustrate a preferred embodiment of the invention, and wherein: FIGURE 1 is a side elevation view of a pump jack and drive apparatus in accordance with the present invention; FIGURE 2 is a cross-sectional view taken generally along line Il-Il of Figure 1; FIGURE 3 is a schematic block diagram of the basic elements of the pump jack and drive apparatus of Figures 1 and 2; FIGURE 4 is a schematic block diagram of a control system used in the drive apparatus of the present invention; FIGURE 5 is a schematic block diagram of an elecrical circuit used in the apparatus of Figures 1 to 4; and FIGURE 6 is a block diagram of a second form of control system for use in the apparatus of Figures 1 to 3.

With reference to Figures 1 and 2, the apparatus of the present invention is intended for use with an otherwise conventional pump jack of the type including a walking beam 1, pivotally mounted on the top of a samson post for rotation around a horizontal axis defined by a saddle bearing 3. The samson post 2 includes four inclined legs 4 extending upwardly from a base 5, a top plate 6 and crossbars 7 extending between the legs 4 at the front and rear ends of the post 2.

A counterweight 8 is mounted on rear end 9 of the walking beam 1, and a horsehead 10 is mounted on the front end 11 of the walking beam 1. A wire line assembly or wire rope bridal 12 is connected at one end to the horsehead 10, and at the other end to a pump mechanism, including a polished rod 13. The bridal 12 and rod 13 are connected by a connector 14. Usually, the polished rod 13 reciprocates a sucker pod or pump rod associated with a downhole pump (not shown).

In conventional pump jacks, the walking beam is caused to rotate around the horizontal axis of the samson post 2 by means of a pitman assembly connected to the rear end 9 of the beam. However in the present invention the walking beam 1 is driven by means of hydraulic piston and cylinder assemblies 1 5 and 1 6 connected to the rear and front parts 9 and 11, respectively, of the walking beam. The bottom ends of the cylinders of the assemblies 1 5 and 1 6 are pivotally connected to an I-beam 1 7 by devises 18. The I-beam 1 7 is supported by the crossbars 7. piston rods 1 9 extend upwardly from the top ends of the cylinders to the walking beam 1.The top ends of the piston rods 1 9 are pivotally connected to the walking beam 1 by devises 20.

The hydraulic piston and cylinder assemblies 1 5 and 16 are operated by a hydraulic pump 22, which is driven by a prime mover in the form of motor 21. Hydraulic fluid is stored in an hydraulic fluid reservoir 23. The pump 22, the motor 21, and the reservoir 23 are mounted on the rear end of the base 5. A V-belt passes around pulleys 25 on the motor 21 and the pump 22, respectively.

As shown in Figure 3, the hydraulic circuit for operating the assemblies 1 5 and 16 includes the reservoir 23, which is connected to a control and pump unit 26 by a line 27, and lines 28 and 29 for conveying hydraulic fluid between the unit 26 and the assemblies 1 5 and 16, respectively. The assemblies 1 5 and 1 6 are single-acting but have non-working chambers connected to sumps 30.

The upper and lower limits of travel of the front end 11 of the walking beam 1 are determined by microswitches or proximity switches 31 and 32, respectively. The switches 31 and 32 are mounted on an arm (not shown) extending upwardly from the samson post 2 in positions such that they are actuated by the walking beam 1 or by a lug or magnet (not shown) projecting outwardly therefrom. By adjusting the positions of the switches 31 and 32, the vertical travel of the ends of the walking beam 1 and of the horsehead 10 can be changed.

Figure 4 shows one form of control systems for the apparatus of Figures 1 to 3, in which the pump 22 is a variable displacement pump, which is used in conjunction with a fixed displacement pump 34.

The pressure of hydraulic fluid (oil) pumped from the reservoir 23 by the pump 34 is kept at constant pressure, normally approximately 250 psi (1,725 kPa), by a relief valve 35 which is connected to a line 36 between the pumps 22 and 34, and vents to a sump 37. Fluid from the pump 34 supplies the main pump 22 and the control system.

Control of the pump 22, and thus of movements of the piston rods 19 and the walking beam 1, is achieved by means of solenoid operated valves 38 and 39, which receive fluid from the pump 34 via lines 40 and 41, respectively, and needle valves 42 and 43, respectively. The valves 38 and 39 and lines 44 and 45 connect the top and bottom working chambers 46 and 47, respectively, of a doubleacting hydraulic control piston and cylinder assembly 48 to the pump 34 or to a sump 49. A piston rod 50 of the assembly 48 is connected to the pump 22 for controlling operation thereof. The limits of movement of the rod 50 are controlled by stops 51 and 52 movably mounted on an arm 53 connected to the cylinder of the assembly 48.

Screws 54 are used to fix the positions of the stops 51 and 52 on the arm 53. The stops 51 and 52 are contacted by a lug 55 on the outer end of the piston rod 50.

A two-way relief valve assembly 56 is connected across the lines 28 and 29 to prevent excessive pressures arising in these lines to cause damage to the apparatus.

The motor 21 drives both the pumps 22 and 34, being connected directly to the fixed displacement pump 34 by a drive shaft 57. With the motor 21 running, the pump 34 delivers fluid to the pump 22 and the remainder of the control system. Fluid is delivered to the solenoid valves 38 and 39 under charge pressure.

Figure 5 shows the electrical circuit that controls the solenoid valves and it will be seen a main switch 58 controls the energization of the solenoids of these valves by a 100-volt AC power source connected to lines 59, 60. The circuit further comprises relays 66, 68 and 70 controlled by the switches 31, 32 and powered by a 12-volt DC source 77, in the manner described below.

When the switch 58 is open, the solenoids are both de-energized so that fluid delivered to these valves is stopped thereat and both working chambers 46, 47 of the control assembly 48 are vented to the sump 49. However, on closure of the switch 58, current flows through lines 59 and 60 and terminals 61,62, either to terminals 63 and 64 to energize the solenoid 65 of the valve 38, or to terminals 72 and 90 to energize solenoid 73 of valve 39, depending on the condition of a relay 68. If the relay 68 is de-energized as shown, solenoid 65 is energized and fluid from the pump 34 flows through lines 40 and 44 to the top chamber 46 of the control piston and cylinder assembly 48.The rod 50 is thereby retracted and sets the pump 22 to cause hydraulic fluid to flow from the assembly 1 6 via line 29, and through the line 28 to the assembly 1 5. This causes the horsehead 10 to move upwardly.

At the top of the stroke of the horsehead 10 of the walking beam 1 , the switch 31 is closed to energize the relay 66, thereby opening a break contact 67 in the power supply circuit of the coil of the relay 70. If at this time the relay 70 were energized (as in a normal operating cycle) the relay 70 would be released by the operation of the relay to close a break contact 69 and open a make contact 74 in a latching circuit for the relay 70.Break contact 69 is in the coil circuit of the relay 68 which is thereby energized to shift control 71 from connecting terminals 63-64 to connecting terminals 63-72, and to shift contact 72 from connecting terminals 61-62 to connecting terminals 61-90. Thus, solenoid 73 of the valve 39 is energized and the solenoid 65 of the valve 38 is de-energized.

Hydraulic fluid then flows through the valve 39 and lines 41 and 45 to the bottom chamber 47 of the assembly 48, while fluid from the top chamber 46 of the cylinder passes through line 44 and the valve 38 to sump 49, the piston rod 50 extending to set the pump 22 to pump hydraulic fluid through the line 29 to the piston and cylinder assembly 1 6 while fluid is withdrawn from the piston and cylinder assembly 1 5 through the line 28. The horsehead 10 then travels downwardly.

During downward movement of the horsehead, the switch 31 reopens and relay 66 is deenergized. However, as switch 32 is also open at this time relay 70 remains de-energized. When the bottom limit of travel of the horsehead 10 is reached, the switch 32 is closed to energize the relay 70: this closes the make contact 74 in the latching circuit shunting switch 32 so that reopening of the latter during the subsequent upward stroke of the horsehead does not cause release of relay 70. The resultant opening of the break contact 69 releases the relay 68. The release of relay 68 releases the solenoid 73 and energizes the solenoid 65 to cause the operating cycle to repeat.

The speed of movement of the piston rods 1 9 in the cylinders of the assemblies 1 5 and 16 is controlled by the spacing of the stops 51 and 52 from a neutral position. If the stops 51 and 52 are placed farther from the neutral position, then fluid is pumped more rapidly to one assembly and withdrawn more rapidly from the other assembly.

Thus, the stop 52 controls the speed of the pump jack, i.e., of the horsehead 10 upwardly, and the stop 51 controls the speed downwardly.

Acceleration of the pump jack is affected by the rate at which the pump 22 is reset at the end of a stroke, i.e. by adjusting the rate of travel of the rod 50 in the assembly 48. The needle valves 42 and 43 control the rate of feed of hydraulic fluid to respective working chambers 46 and 47 of the assembly 48, and thus control the rate of movement of the rod 50, which in turn controls the rate of change of fluid displacement through the pump 22. The valve 42 controls acceleration from the bottom of the stroke and the valve 43 controls acceleration from the top of the stroke of the pump jack. Thus the system provides for independent adjustment of the speeds of the individual strokes of the pump jack and also independent adjustment of the acceleration in each direction of motion.

Referring now to Figure 6, a control system utilizing a fixed displacement pump will now be described. In situations where there is no need for easy adjustment of the speeds of operation of the pump jack, a fixed displacement pump 78 can be used, with a resulting saving in costs. The ratio of the speeds of movement of the piston rods 1 9 upwardly and downwardly, and thus the ratio of the speeds of the horsehead 10 in the two directions, can be determined by use of piston and cylinder assemblies having appropriately different cylinder diameters and such ratio adjusted, if required, by exchanging one or both assemblies for another or others of different cylinder diameter.

Thus, for instance, if the cylinder diameter of the assembly 1 5 is twice that of the assembly 16, the pump jack will move downwardly four times more quickly than upwardly, for any given constant fluid pumping rate by the pump 78, while the overall speed of the pump jack is determined by the fluid pumping rate, i.e. by the size and speed of operation of the pump 78.

The control system of Figure 6 is similar to that of Figure 4, and wherever possible the same reference numerals have been used to identify the same or similar elements.

The operation of the control system of Figure 6 is the same as that of Figure 4, except that the outer end of the piston rod 50 of control piston and cylinder assembly 48 is connected to a valve 79, which is connected directly to the outlet of the pump 78 by a line 80, and to the lines 28 and 29 for carrying hydraulic fluid to and from the piston and cylinder assemblies 1 5 and 16, and to sump 81. A relief valve 82 is connected to the line 80.

Movement of the piston rod 50 following opening of one of the valves 38 and 39 results in movement of the valve 79 to a position in which fluid flows to one of the assemblies 1 5, 1 6, and fluid is returned to sump 81 from the other assembly.

The advantages of the apparatus described hereinbefore are many. By eliminating the conventional drive assembly, which includes a gearbox, the horsehead can be driven upwardly and downwardly at different rates, i.e., the horsehead can ascend more quickly than it descends. The speed of operation of the pump jack is relatively easy to adjust with the apparatus of the present invention. Because the stroke pattern is not necessarily simple harmonic (sinusoidal), forces and peak velocities can be reduced to provide increased efficiency.

By locating the drive piston and cylinder assemblies close to the fulcrum of the walking beam, piston rod movement is decreased, and thus cylinder life is increased. Hydraulic pumps presently in use require a ratio of cylinder rod movement to polished rod movement of 1:1.

Further modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art, the manner of carrying out the invention. It is further understood that the form of the invention herewith shown and described is to be taken as the presently preferred embodiment. Various changes may be made in the shape, size and general arrangement of components, for example, equivalent elements may be substituted for those illustrated and described herein, parts may be used independently of the use of otherfeatures, all as will be apparent to one skilled in the art after having the benefits of the description of the invention.

Claims

1. A driving apparatus for a pump jack of the type including a samson post, a walking beam pivotally mounted on the samson post for rotation/ around a horizontal axis, and a horsehead on one end of the walking beam for driving connection to a pump mechanism, the driving apparatus comprising driving piston and cylinder means articulated to said samson post and to the walking beam at a position displaced from said horizontal axis; and control means for operating said piston and cylinder means to cause motion of the walking beam to reciprocate said horsehead upwardly and downwardly, with independent control of the upward and downward movements, respectively.

2. A driving apparatus for a pump jack of the type including a samson post, a walking beam pivotally mounted on the samson post for rotation around a horizontal axis, and a horsehead on one end of the walking beam for driving connection to a pump mechanism, the driving apparatus comprising first driving piston and cylinder means pivotally mounted on said samson post and pivotally connected to said walking beam on one side of said horizontal axis for moving said one end of said walking beam upwardly; second driving piston and cylinder means pivotally mounted on said samson post and pivotally connected to said walking beam to the other side of said horizontal axis for moving said one end of said walking beam downwardly; and control means for alternately operating said first and second piston and cylinder means independently of each other, whereby said one end of the walking beam and said horsehead are reciprocated upwardly and downwardly, the upward and downward movements being at the same or different speeds.

3. An apparatus according to claim 1 or 2, wherein said control means includes pump means; switch means operated by said walking beam at the top and bottom limits of the stroke thereof; valve means for directing hydraulic fluid from said pump means to said piston and cylinder means selectively to effect upward and downward movement of the horsehead respectively; and control cylinder means for actuation by said switch means for controlling said valve means and consequently the flow of hydraulic fluid to said driving piston and cylinder means.

4. An apparatus according to claim 3, wherein said valve means includes a variable displacement pump for feeding hydraulic fluid to said piston and cylinder means; a main pump for supplying hydraulic fluid to said variable displacement pump; means connecting said control piston and cylinder means to said variable displacement pump; and control valves operatively connected to said switch means for controlling operation of said control piston and cylinder means and consequently operation of said control piston and cylinder means and consequently the feeding direction of said variable pump.

5. An apparatus according to claim 3, including a fixed displacement pump for supplying hydraulic fluid directly to said valve means; control means operatively connected to said switch means for controlling operation of said control piston and cylinder means; and a main pump for supplying hydraulic fluid to said control valve means and said control piston and cylinder means.

6. Driving apparatus substantially as herein described with reference to, and as shown in, Figures 1 to 5 of the accompanying drawings.

7. Driving apparatus according to claim 6, modified substantially as herein described with reference to, and as shown in, Figure 6 of the accompanying drawings.

8. A pump jack having driving apparatus in accordance with any one of the preceding claims.

9. Every novel feature and every novel combination of features disclosed herein.