US2358058A - Hydraulic coupling - Google Patents

Description

Sept. 12, 1944. w. J CRITES 2,358,058-

HYDRAULIC COUPLING Filed March 6, 1942 2 sheets sheet 1 INVENTOR W. J. CRITES 2%, M ATTOR EYS Patented Sept. 12,1944

HYDRAULIC COUPLING Wilbur J. Critos, Bartlesville, kla., assignor to Phillips Petroleum Company, a corporation of Delaware Application March 6, 1942, Serial No. 433,676

gravitational effect at that point to the extent 3 Claims.

This invention relates to improvements in pumping machinery used in the production of oil from wells, and particularly to apparatus for hydraulically connecting a prime mover to a pumping device.

In the pumping of wells by sucker rods, it is now common practice to operate the rods with an oscillating beam to which at one end is attached the sucker rods and at the other end a pitman which is actuated by a crank. To offset the weight of the rods and to store the energy incident to the dropping thereof, a counter-balance is used. The counter-weight is in a definitely fixed position approximately in a relative cyclic position of 180 from the load. On account of the elasticity of the sucker rods and tubing, the compressibility of the fluid being produced and the ever changing stress throughout thepumping cycle, the counter-balancing effect should be ever changing both with reference to position and force applied to conform with both the stress requirements of the load and the regenerative effect of the falling sucker rods.

In the pumping of oil from wells by the means discussed herein, there are two types of stresses developed, namely; static stresses, or those that result from suspended loads, and dynamic stresses, or those that result from the application orinterruption of motion. The destructive efiect of static stresses is negligible, but dynamic stresses are extremely destructive and are the source of almost all mechanical failures. The greatest dynamic stress in the pumping of oil wells occur from the interruption of motion and is normally at that point that the fiuid is started in motion on the up-stroke after the elasticity of the rods has been expended. The greater the acceleration at this point the greater the stress, because the entire load must be set in motion from a static state. Therefore, at this point it is important to have a minimum rate of acceleration. Normally, although the stresses are of greater magnitude on the up-stroke of the rods, those on the down-stroke may be more destructive. On the down-stroke, the rods are either in tension from their own suspended weight or if the rate of imparted motion exceeds the actual rate of gravitational acceleration, the rods will be in compression. Compression stresses in a sucker rod system are not, per se, destructive, but on account of the high ratio of longitudinal to cross sectional area and absence of an immediate supporting medium,- the rods will enter a bending stress at such time as the resistance to downward travel at the plunger becomes greater than the that the rod column above will be distorted. Unlike the stresses of tension and compression, the bending stress from distortion is not distributed throughout the length of the rods, but will be.

concentrated in a. few places.- The points of bending stress concentration will be at those points that offer the least'resistance to bending and repeated bendin at such points will soon result in fatigue failures. Such stress concentration may result in shortening the life of the rods from the superimposed weight of the rods alone, but when the rate of applied motion is greater than the rate of motion due to gravity, the stress is increased, resulting in much earlier failure of the rods.

Many patents have been issued, including my Patent No. 2,204,725, which tend to reduce acceleration as the load increases. Most of these are known as shock absorbers, but in all of these in which there is a definite speed relationship between the prime-mover and the load, the reactive effects may often be as destructive as the direct effects would have been without the application of the device which do not control the acceleration. In order to obtain the maximum stress reduction, the speed of the load must be independent of the speed of the prime mover.

The solution of the problem lies in having a coupling device, which is responsive to torque changes and in which there is substantially no reactive effect, between the prime mover and the load. Although the normal hydraulic coupling would have distinct advantages in its application to a system of this kind, it is obvious that a coupling in which the slip characteristics are adjustable would have greater merit than one in which they are not. Further, a minimum slip on the down stroke of the sucker rods will result in storing maximum energy in the flywheel and that controlled slippage on the upstroke of the rods will effect a minimum stress occurrence.

My instant invention employs a type of coupling for hydraulically connecting a prime mover to a pumping unit in a manner whereby full mechanical advantage is obtained from the energy falling sucker rods and full control of the sucker rods is obtained during the pumping cycle. It is to be noted that my instant invention may be employed in an oil well umping system, such as that shown and described in my U. S. Patent N1 2,268,701.

The primary object of my instant invention is to provide an apparatus for hydraulically connecting a prime mover to a pumping device.

Another object of my invention is to provide a hydraulic coupling for use with well pumping equipment which stores the energy of the falling sucker rods in a flywheel and then utilizes said stored energy to assist the prime mover during periods of peak loads.

A further object of my invention is to provide a hydraulic coupling apparatus in conjunction with well pumping equipment which will reduce stresses in the pumping equipment, particularly in the sucker rods.

Another object is to provide a well pumping apparatus which will require less power for operation than present-day conventional equipment.

These and additional objects and advantages will be apparent to persons skilled in the art by reference to the following description and annexed drawings, wherein Figure 1 is a plan view of the pumping equipment which may be employed in the practice of my instant invention;

Figure 2 is an elevation view of the pumping equipment shown in Figure 1;

Figure 3 is an elevation view of my invention partly in cross-section, of the hydraulic coupling device employed in thesystem that is shown in Figures 1 and 2;

Figure 4 is a sectional view of my invention, partly in cross-section, taken along the line 4-4 of Figure 3; and

Figure ,5 is a fragmentary elevation view, partly in cross-section, of a portion of the hydraulic coupling device as employed in a second embodiment of my invention.

Referring to the drawings and more particularly to Figures 1 and 2, I have denoted therein a prime mover, such as a high slip type alternating current electric motor, by reference numeral ||l. Rotary motion developed by prime mover I is transmitted by shaft to a flywheel I2 and to one portion of a positive displacement rotary pump which is adapted to serve as a, coupling means |3 that is connected to the shaft. A pulley H, which is secured to another shaft l5 that is connected to another portion of coupling means I3, transmits power through V-belts l6 from the prime mover to a drive wheel I! which is connected to one end of a pitman l8. The other end of the pitman is connected to one end of a walking beam l9 which is supported by a Samson post 20. The other end of the walking beam is connected to a sucker rod string I 2| which is employed in lifting fluid from an underground formation. In the lifting of fluid, sucker rod string 2| reciprocates through conventional surface well equipment 22.

Turning next toFigures 3 and 4 for a. description of coupling means l3, it is to be noted that I employ a positive displacement rotary pump which is adapted to serve this purpose. 'I do not desire to limit my instant invention to any particular type of positive displacement rotary pump means, as other types may be employed successfully; but rather, I have shown and I will hereinafter describe this particular type for the purpose of disclosing my instant invention. Shaft I5 is integral with a housing 23 of the coupling means, and is adapted to accommodate a pump rotor 24 which is integral with shaft Housing 23 extends outwardly over shaft II and is provided with a packing gland 25 which is employed to hermetically seal the housing and to prevent the leakage of a working fluid which is placed interior of the housing and utilized to operate the coupling means. In adapting the pump to a hydraulic coupling, I have provided housing 23 with an interior liner partition 26 in which rotor 24 is rotatably positioned. Partition 26 is adapted to form an inlet chamber 21 and a discharge chamber 28 which connect with a passage 29 that is formed in housing 23 through head at which is adapted to be slidably positioned on one end of a valve stem 31. The valve head is provided with an interior bore 38 which permits a desired lateral movement of the valve head along stem 31. A compression spring 39 of any desired strength is carried on the valve stem which extends beyond housing 23 and which is connected at its outer end to a thrust plate 40 that is rotatably positioned on shaft l5. One or more stop assemblies 4|, each having a compression spring 42, which is identical to spring 39, are attached to housing 23 and to the thrust plate, which is maintained perpendicular to the central axis of shaft I5 at all time's.- Thrust plate 40 is urged to the right by springs 39 and 42, and to the left by an adjustment collar 43 which in turn is moved to the left by a yoke 44 that is attached to the adjustment collar in a pivotable manner, and which carries a rack 45 on its upper end. A pinion 46, which meshes with the rack to move the adjustment collar, is mounted in a well known manner on a support 41 which also assists in supporting yoke 44. A thrust-bearing 48 is preferably placed intermediate thrust plate 40 and adjustment collar 43 to facilitate relative movement therebetween.

' operation of the coupling l3, as shaft rotates rotor 24, the working fluid is discharged into chamber 28 from which it flows through port 3|, passage 29, port'30, and thence into chamber 21 from which it is pumped again into chamber 28. It is to be further noted that when valve 36 is seated that the coupling is hydraulically locked since no fluid can flow through passage 29, causing shafts II and |5 to rotate substantially at the same rate of speed. On the other hand, if valve head 36 is open, the rotation of shaft 5 will be a function of the pressure of the fluid pumped from port 30 to port 3|, whereby the fluid acts upon rotor 24. diate position for valve 36 will usually effect the most desired rate of rotation of shaft l5. With a varying load, such as that of sucker rods 2|, the rotational speed of the shaft will further vary withvariations in the torque of shaft I! which varies with the load of the sucker rods. Let us assume that the prime mover has been placed in operation, that valve 36 is placed in a desired spaced relationship with valve seat 35, and that the pumping equipment shown in Figure 1 is set'into operation with sucker rods 2| just beginning to move upwardly. At this point in the pumping cycle, the load on sucker rods 22 is at substantially a minimum. But as the Some intermel any appreciable movement of the plunger but with increasing rod load which increases the torque of shaft I and causes the shaft to slow down. Due to the amount of fluid passing valve 36, when shaft I5 is slowed down, the acceleration of the rods occurs gradually without sub jecting the equipment to severe stresses. As the rods begin to accelerate, the torque on shaft I5 decreases, less fluid passes valve 36, and shaft I5 rotates more rapidly. As the rods reach the end of the upward stroke and start downwardly, the weight of the falling rods accelerates shaft I5 until it rotates at a faster rate than shaft II,

, causing the working fluid in coupling I3 to be pumped in a reverse direction from chamber 21 to chamber 28 through passage 29 where the fluid acting-against the partially opened valve head 36 causes it to move over stem 31 and seat upon valve seat 35, closing passage 29 and hydraulically locking my. device. Thus, the energy of the falling rods is transmitted through shaft I5, coupling I3, and shaft II to flywheel I2 where the energy is stored in the rotating flywheel. Not only does the flywheel decrease the speed of the falling rods, but also at the end of the downward stroke and at the beginning of the upward stroke, the energy stored in the flywheel is utilized in assisting the prime mover to accelembodiment are designated by like reference numerals. The hydraulic coupling means, herein after referred to, is similar to that described in the first embodiment, differing therefrom in the means employed to control the flow of fluid through passage 29. In this modification, I have attached a cylinder 59 to the exterior of housing 23. Cylinder 50 contains a spring loaded piston 5| which is adapted to slide therein, and which is secured to one end of a slidable valve stem 52. The other end of the valve stem is secured to a valve 53 which is adapted to engage a. valve seat 54, closing off passage 29. A compression spring 55 of any desired strength is positioned around stem 52 between the exterior of housing 23 and piston 5| within cylinder 50 in order to move the piston to the right during the periods of operation of my device when the spring is strong enough to overcome the pressure of the working fluid which is conducted to the righthand end of cylinder 50 through a conduit 56 which also connects with passage 29. Normally, when my device is not operating, spring 55 is adjusted to hold valve 54 open.

The operation of the modified form of the invention is similar to the operation of my first embodiment. Let us assume that the apparatus is assembled as shown in the drawings. To start my device, prime mover III is set in operation. Since spring 55 normally holds valve 53 open, shaft II starts to rotate while shaft I5 remains stationary. Thus, fluid is pumped from chamber 21 to chamber 28 and thence through passage 29 back to chamber 21. The pumping of the fluid increases the pressure thereof and assists spring 55 in holding the valve open by acting upon the face of the valve against the pressure of the fluid acting upon the face of piston 5|. When the pressure acting upon the face of piston 5| becomes sufliciently great, stem 52 is moved to the left. With the continued rotation of shaft II,.the pressure of the fluid will continue to build up until valve stem 52 sufliciently closes valve 53 and the pressure of the fluid causes housing 23 and shaft I5' to rotate, setting rods 2| in motion. If the torque on shaft I5 required to set the rods in motion is large, the pressure in passage 29 will build up rapidly with a resultant rapid and more complete closing of the valve, but as the valve approaches a closed position, the pressure acting upon valve head 53, plus the force of spring 55 will tend to hold the valve in an open position. It will be apparent that by employing a proper sized valve and piston, and by properly adjusting spring 55, I can adapt my device to operate automatically under the numerous types of loading conditions to which well pumping equipment is normally subjected, and thereby obtain any desired rate of acceleration of rods 2|. During the downstroke of rods 2|, the energy of the falling rods is transmitted to flywheel l2 in an identical manner to that described in the first embodiment whereby the weight of the falling rods causes shaft I5 to rotate more rapidly than shaft II. This causes the working fluid to flow through passage 29 in reverse to its normal direction, whereby the pressure of the Working fluid acting upon the piston and upon the back face of thevalve head cause the valve to close and hydraulically lock the coupling means.

It is to be understood that although I have described the application of my deviceto pumping equipment, that I am aware that it may be adapted to operate many other types of machinery and employed therewith advantageously.

From the foregoing, it is believed that the apparatus for practicing my instant invention will be readily comprehended by persons skilled in the art. It is to be clearly understood, however, that various changes in the apparatus herewith shown and described and in the modes of operation outlined above may be resorted to without departing from the spirit of the invention, as defined by the appended claims.

I claim:

1. A fluid coupling for transmitting energy from a rotatable driving shaft to a rotatable driven shaft comprising a housing adapted to be connected to one of the above mentioned shafts; a positive displacement pump including a pump chamber formed within the housing, a pump rotor rotatably disposed in the chamber and adapted to be connected to the other above mentioned shaft, a fluid inlet and a fluid outlet communicating with the chamber; a conduit establishing communication between the inlet and the outlet; valve means for controlling the flow of fluid through the conduit, a cylinder secured to said housing,means for normally maintaining the valve means in a predetermined position, and a piston in the cylinder responsive to the pressure of fluid in the conduit for actuating the valve means against the action of the last mentioned means.

2. A fluid coupling for transmitting energy tioned shaft, a fluid inlet and a fluid outlet communicating with the chamber; a conduit establishing communication between the inlet and the outlet, a valve seat in the conduit, a valve stem and valve head movable to close the seat, the stem extending into a cylinder, a piston on the stem fitting the cylinder, and a fluid supply line from the conduit to the cylinder to supply fluid to move the piston in the cylinder to actuate the valve head.

3. A fluid coupling for transmitting energy from a rotatable driving shaft to a rotatable driven shaft comprising a housing adapted to be connected to one of the above mentioned shafts; a positive displacement pump including a pump adapted to be connected to the other above menchamber formed within the housing, a pump rotor rotatably disposed in the chamber and adapted to be connected to the other above mentioned shaft, a fluid inlet and a fluid outlet communicating with the chamber; a conduit establishing communication between the inlet and the outlet, 2. valve'seat in the conduit; a valve stem and valve head movable to close the seat, the stem extending into a cylinder, a piston on the stem fitting the cylinder, a fluid supply line from the conduit to the cylinder to supply fluid to move the piston in the cylinder to actuate the valve head to close the seat, and spring means constantly urging the piston to actuate the valve head to open the seat.

' WILBUR. J. CRITES.

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