US3018865A

US3018865A - Deep well pump jack counterbalance control means

Info

Publication number: US3018865A
Application number: US593152A
Authority: US
Inventors: Luther A Blackburn
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-06-22
Filing date: 1956-06-22
Publication date: 1962-01-30
Anticipated expiration: 1979-01-30

Description

Jan. 30, 1962 L. A. BLACKBURN 3,013,865

DEEP WELL. PUMP JACK COUNTERBALANCE CONTROL MEANS Filed June 22, 1956 2 Sheets-Sheet 1 Jan. 30, 1962 1 A. BLACKBURN DEEP WELL PUMP JACK COUNTERBALANCE CONTROL MEANS Filed June 22, 1956 2 Sheets-Sheet 2 6 9, 6 5 e@ auf gjm@ .2 C Z MLM-; WV m l.. 2K0@ 19 50N. f8 lwwjl W la United States Patent() y f' 3,018,865 DEEP WELL PUMP JACK COUNTERBALANCE CONTROL MEANS Luther A. Blackburn, Los Angeles, Calif. (4919 Highland View Ave., Eagle Rock, Calif.) Filed June 22, 1956, Ser. N0. 593,152 Il Claims. (Cl. 192--116.5)

This invention relates to pressurized foam counterbalanced pump jacks for oil well pumps and more particularly to safety and foam conservation features in such pumps.

This application is a continuation in part of my prior application, Serial No. 394,405, filed November 25, 1953, now Patent No. 2,756,602, issued July 31, 1956, and relates to means for automatically dissipating the counterbalancing pressure and for disabling the actuating prime mover in the event of breakage of the sucker rod string and to means for collecting and returning to use any of the foam forming fluid which may escape past the foam compressing piston and cylinder means which comprise the counterbalancing means. 'Ihese features, while first disclosed in my said prior application are equally valuable when applied to a pressurized foam counterbalanced walking beam type of pump jack such as disclosed in my prior Patent No. 2,664,764 as well as on any other pump jack in which the counterbalancing effect is achieved through compression of an elastic fluid composition. i

Accordingly, an object of the present invention is to provide safety means for pressurized foam counterbalanced pump jacks which responds to an effect deriving from breakage or disconnection of the sucker rod string from the jack and which is effective by such response to release the counterbalacing pressure and to disable the prime mover by which the jack is actuated.

Another object of the invention is to provide a safety means embodying the above objective and which includes means responsive to centrifugal force attached to a rotating part of the jack mechanism and which is effective in the event of increased speed of rotation of the shaft deriving from breaking of the sucker rod string or disconnection of the string from the jack to actuate other devices which in turn release the counterbalancing pressure and disable the actuating prime mover.

A further object of the invention is to provide devices for collecting escaped foam forming material in pressurized foam counterbalanced pump jacks and returning the escaped material to the counterbalancing cylinder.

A still further object of the invention is to provide a foam material collecting and returning means for the aforesaid type of pump jacks which includes a collecting sump in the piston element of the counterbalancing means and a pump carried by the piston and actuated as an incident of the reciprocating motion of the piston and cylinder of the counterbalancing means to return escaped foam forming uid collected in the sump to the interior of the cylinder.

With the foregoing objects in view together with such other objects and advantages as may subsequently appear, the invention resides in the parts, and in the construction, combination and arrangement of parts described in the 4following specification of certain presently preferred ernbodiments of the invention; reference being had to the accompanying drawings which form a part of said specification and in which drawings:

FIG. l is a side elevation of a pump jack of the type shown in my said prior application Ser. No. 394,405; the view generally corresponding with FIG. 2 of that application with certain portions deleted and certain other portions shown in greater detail through partial breaking away of portions of the structure for the purposes of disclosure of the present invention,

3,018,865 Patented Jan. 30, 1962 FIG. 2 is a fragmentary side elevational view of the portion of FIG. l indicated by the arrowed lines 2, 2 on FIG. l,

FIG. 3 is a longitudinal, medial sectional view, in enlarged scale of one of the pressure release valve devices shown in side elevation in FIG. 2, j

FIG. 4 is a vertical, medial sectional View in enlarged scale of the speed responsive devices which actuate the safety means,

FIG. S is a fragmentary, partially sectional view taken at right angles to FIG. 1 at the upper end of the frame structure and showing the connection of the counterbalancing cylinder to the crosshead supporting means at the upper end of the stroke and the engagement with the pump means for returning escaped fluid by the said crosshead connecting means,

FIG. 6 is a medial sectional view taken at right angles to FIG. 5,

FIG. 7 is an enlarged medial sectional view of the piston land fluid return pump means taken on the same line as FIG. 6, l

FIG. 8 is a perspective side elevation of a pump jack of the type described and claimed in my said-prior Patent 2,664,764`showing the application thereto of safety means embodying the principles of the safety means above de- 'scribed in connection with the form of the invention shown in the preceding figures,

FIG. 9 is an enlarged scale, vertical, median sectional view of the centrifugal force responsive actuating means for the safety means,

FIG. 10 is a fragmentary, longitudinal medial sectional View of the counterbalancing cylinder and piston showing the recovering means for the foam forming material,

FIG. ll is a greatly enlarged view of the valve assembly unit associated with the foam material recovery means shown in FIG. l0, and

FIG. 12 is a transverse sectional view taken on the line 12-12 of FIG. 11.

Referring first to FIGS. 1 through 7, the pump jack there shown comprises a vertical frame structure comprising a base 1 supporting a prime mover, here shown as an internal combustion engine 2, and a frame structure 3 including vertical cylindrical tank members 3 which are connected at their upper ends by a crown block structure 4 and adjacent their lower ends by structural members 5 and 5'; there being four of the said tank members arranged in spaced rectangular configuration as viewed in plan. Mechanism including a drive shaft 6 imparts reciprocation to a crosshead within the frame and the crosshead is connected to the polish rod of a sucker rod string disposed inan axial line coincident with the vertical axial line of the frame structure. Attached to the cross head is a foam pressure counterbalancing means comprising a cylinder 7 having a closed upper end and an open lower end slidingly engaging a stationary piston supported by `two

pipes

9 and 10. The tank members 3' are connected through the piston supporting pipes with the interior of the cylinder and as the cylinder descends with the crosshead on the downstroke of the pump the pressurized foam contained within the cylinder and tank members is further Compressed and the resistance deriving from the said compression provides the necessary counterbalancing effect for the weight of the sucker rod string.

All of the foregoing structure is fully described and claimed in my said prior application and the present application is directed to certain safety features described therein but not claimed; said features being also useful in pump jacks of other design which employ the pressurized foam method of counterbalancing the weight of the sucker rod string. Additionally, this application is directed to means for conserving the foam forming materials which are useful in other foam counterbalanced pump jacks.

The engine 2 is operatively connected to a speed reducer 11 and the driven pulley of the speed reducer is connected by a belt 12 to a pulley 13 mounted on one end of the shaft 6 which is journaled on suitable bearings 14 and 15 carried by the frame structure 1. The oppositeend of the shaft 6 extends laterally beyond the bearing 15 and has a reduced diameter distal end portion 16 (see FIG, 4) on which a sleeve 17 having a closed outer end is slidingly mounted. Inwardly of the open end of the sleeve 17, the shaft portion 16 carries a pair of oppositely radially extending lugs 18 each of which pivotally supports a bell crank member 19; each bell crank member including a radially extending arm 26 engaging the open end of the sleeve 17 and a second arm 21 spaced from and extending normally parallel to the axis of the shaft portion 16 with the free ends of said arms extending toward the distal end of the shaft. When the shaft is rotated, centrifugal force developed in the arm portions 21 will tend to swing them outwardly with resultant tendency to move the sleeve 1,7 outwardly. A housing 2,2 secured to a bracket member 23 covers the above described members. The frame structure 1 'carries a bracket member 24 extending laterally therefrom below the bracket 23 and a lever 25 is pivoted intermediate its end to the distal end of the bracket 24. One end of the lever 25 extends upwardly and thence toward the frame structure and terminates in a pad portion 26 disposed within the housing 22 adjacent the closed end of the sleeve 17. The other Aend 28 of the lever 25 extends downwardly and is connected to the handle 29 of a valve 30 interposed in a line 31 leading from one of the tank members 3' to a cylinder 32 disposed in a horizontal position adjacent the opposite side of the frame structure; said cylinder having a piston 33 therein including a piston rod 34 projecting out of the end of the cylinder adjacent the said opposite side of the frame structure and slightly below a horizontal plane containing the lower edge of the pulley 13. Pivotally mounted at 35 on the frame structure above the cylinder 32 is a brake operating member 36 depending from said pivotal mounting and extending across the path of travel of the piston rod 34. The brake operating member 36 carries a brake shoe 37 at a point opposite the side face of the pulley 13 which point is between the pivotal mounting 35 and the point of engagement of the piston rod 34 with the brake operating member. A spring 38 extending between the bracket 23 and the upper portion of the lever 25 tends constantly to urge that end of the lever toward the end of the sleeve 17 and an adjustable stop element 39 carried by the bracket 23 serves to limit the extent to which the spring can move the lever. A second spring 40 normally holds the brake operating member retracted and in contact with the piston rod 34.

At normal operating speeds the centrifugal force acting on the bell crank members 19, 19 is insufficient to overcome the bias of the spring 3S and hence the lever is not displaced. If, however, the sucker rod string should break or the polish rod clamp should pull free from the polish rod, the release of the load would cause the jack to increase in speed to an extent that might wreck the entire jack. In the present invention, the sudden increase in speed causes the sleeve 17 to be shifted outwardly by the bellcranks 19, 19 against the bias of the spring 38 with resultant movement of the lever 25 in a clockwise direction as viewed in FIG. 1. This movement causes the valve 30 to open allowing the pressure of the counter balancing foam to ow through the line 31 to the cylinder 32 with resultant projection of the piston rod 34 to the left (as viewed in FIG. 1) against the brake operating member 36 with movement of that member against the bias of the spring 40 and consequent engagement of the brake shoe 37 with the pulley 13. At the same time, a link 41 which also serves as the connecting means between the end 2 8 of the lever 2,5 and the valvehandle 29 engages an electric switch 42 in the ignition circuit of the engine 2 and disables the engine. The distal end of the brake operating member 36 is connected to one end each of two cables 43 and 44 which are trained, respectively, over pulleys 45 and 46 and at their other ends are connected to valve operating yokes 47 and 48. The valve operating yoke 48 is connected to a main valve 49 interposed in the pipe 10 adjacent the base of the machine and is also connected to a normally closed blow ott valve 50 in a pipe connected at one end to the pipe 10 between the cylinder 7 and the main valve 49 and which is open to atmosphere at its other end. The cable 43 connected to the yoke 47 similarly operates a main valve 51 interposed in the pipe 9 and a corresponding blow off valve. The release of the counterbalancing pressure is necessary since in the event of a break in the sucker rod string, upon stopping the engine, this pressure would hold the cylinder at its top stroke position were it not for release of that pressure.

The pressure induced movement of the brake operating member 36 in addition to the brake applying action operates to close the main valves 49 and 51 thus cutting oit the communication between the tank members 3 and the cylinder 7 and at the same time opens the blow off valves with resultant release of the pressure in the cylinder. With the stoppage of the engine and application of the brake, the centrifugal means which initiated the above sequence of actions allows the spring 38 to return the lever 25 back to normal position with resultant closing of the valve 30, but since the pressure is trapped in the line 31 and cylinder 32, the brake continues to be applied and the main valves 49 and 51 continue to be held closed. When, as an incident to restoring the mechanism to operative condition, it is desired to release the brake and reestablish communication betwcen the tank members and the cylinder, a normally closed, manually operated valve 52 in a line 53 leading from the line 31 and open to atmosphere is opened momentarily to release the trapped pressure and upon such release, the spring 40 will pull the brake operating member back to normal position moving the piston rod 34 back into the cylinder and allowing the main and blow off valves to resume their respective normal open and closed positions.

Referring next to FIGS. 8 and 9, the safety means above described are shown as applied to a pump jack of the type described and claimed in my prior Patent 2,664,764. In this form of the invention the pump jack comprises a base 54 on which is mounted a prime mover 55, here shown as an internal combustion engine, although an electric motor may be equally well employed if an energy source is available. The prime mover is provided with a driving pulley 56 which is connected by a belt 56 to another pulley (not shown) on the driving shaft 57 of a speed reducer 58 having a driven shaft 59 carrying crank arms 60 at opposite sides of the speed reducer case which are connected by connecting rods 61, 61 to an evener member 62 carried by one end of a walking beam 63 which is pivotally mounted intermediate its ends at the top of a Samson post structure 64. The opposite end of the walking beam 63 carries a horsehead member 65 which is connected by a cable 66 to a polish rod clamp 67 and the clamp is in turn connected to the polish rod R of the pump P. The Samson post is formed as a cylindrical tank rising from a tank base 68 and a cylinder 69 extends diagonally upwardly through the Samson post in a vertical plane containing the longitudinal dimension of the walking beam. Slidably mounted in the cylinder 69 is a piston 70 provided with rings 76' and which piston is connected to an arm 71 depending from the walking beam adjacent the horsehead 65 by a connecting rod 72. As disclosed in the said Patent 2,664,764, the Samson post, tank base and the lower end of the cylinder are in communication with each other and the resulting enclosed space is filled with a foam which is subjected to sufficient pressure to cause the force thereof exerted against the piston to serve as a counterbalance for the weight of the sucker rod string.

If the polish rod clamp should slip or be pulled off or if the sucker rod string should break or become uncoupled the reduction in the load would cause the prime mover to run away with probable extensive damage to the pump jack. To guard against this possibility, the speed reducer driving shaft 57 is extended beyond the side of the speed reducer case (see FIG. 9) and is provided with oppositely radially extending

lugs

73, 73 to which are pivoted bell crank

members

74, 74 having radially inwardly extending

arms

75, 75 engageable with a sleeve 76 slidably mounted on a reduced diameter distal end portion 77 of the shaft and free ended arms 75', 75 normally extending parallel to the sleeve 76; said sleeve having a closed end 78 extending over the end of the shaft. A housing comprising a bottom portion 79 secured to a bracket 80 extending outwardly from the side of the speed reducer 58 and an upper portion 31 secured to the bottom portion 79. Projecting outwardly from the side of the side wall of the speed reducer beneath the bracket St) is a boss 82 terminating in an ear portion 83 projecting beyond the edge of the bracket and having a hole extending therethrough in which a pivot pin 84 is disposed and on which pin a lever 85 is fucrumed; said lever being disposed in a vertical plane and having an upper end portion 86 extending above the top surface of the housing and at its mid length having a laterally extending arm lterminating in a pad portion 87 disposed in an opening 88 in the front face of the housing and in close proximity to the end 78 of the sleeve 76. A tension spring 89 extending between the upper end of the lever S5 and the side of the speed reducer case constantly urges the upper end of the lever toward the gear case and a stop screw 90 in the wall of the bottom portion 79 of the housing serves to adjustably limit the extent to which the spring can thus move the lever. The extreme upper end of the lever 85 is connected by a link 91 to the handle 92 of a normally closed valve 93 interposed in a line 94 extending from the lower end of the cylinder 69 thence beneath the speed reducer case, thence upwardly alongside of the engine 55, thence horizontally above the housing and thence connecting with one end of a cylinder 95 having a piston 95 carrying a piston rod 97 which projects out of the opposite end of the cylinder 95. The counterbalancing cylinder adjacent to the inner end thereof has a pipe 98 extending upwardly therefrom; said pipe being open to atmosphere at its opposite end and having a valve 99 interposed therein; said valve having an operating handle 100 disposed in the path of movement of the piston rod 97. For the reasons earlier pointed out, the release of pressure is necessary to bring the member carrying the polish rod clamp to its down stroke position Normally, the valve 99 is yclosed and the piston an piston rod are retracted within the cylinder 95. The spring 89 is suiciently strong to hold the lever 85 against ldisplacement by centrifugal force operating on arms 75',

75' of the bell crank members 749, 74 under the normal 'operating speed of the shaft 57. In the event of breakof the valve 93 and admission of pressure to the cylinder 95 which, in turn, will cause the piston rod 97 to be projected outwardly and open the valve 99 to release the counterbalancing pressure. At the same time, an arm 101 depending from the lever 85 operates a switch 102 to disable the engine in any suitable manner as, for example, by shorting out the magneto M or other appropriate disabling of the ignition circuit. On the dropping of the speed of the shaft 57, the spring 89 will return the lever to position against the stop 91 with resultant v closing of the valve 93 and return of the switch 102 to its normal position permitting operation of the engine.

Before the jaci; is restored to operative condition, the valve 99 is manually closed and since there is no pressure in the counterbalancing system, the said closing action can be accomplished without opposition by the piston rod 97. This form of the invention relates to pump jacks having relatively short strokes and for use in shallower wells and consequently there is less foam forming material to be blown off in case of accidents as above described, wherefore, in the interest of simplicity of construction, the interposition of valve means between the main foam storage chamber in the Samson post to conserve this portion of the foam is dispensgd with.

Referring next to FIGS. 5, 6 and 7, there is shown a means for conserving the foam forming materials that may escape past the counterbalancing piston and cylinder during the operation of the jack. The piston 8 is provided with upper, intermediate and lower sets of

piston rings

103, 104 and 10S with annular grooves 106 and 107 interposed between the respective sets of rings. Mounted in the axial centerline of the piston 8 is a pump cylinder 109` having its upper end threaded into the head of the piston and carrying a collar 109 intermediate its length which engages the side walls of the piston. Slidably mounted in the pump cylinder 108 is a plunger 110 having piston rings 111 engaging the wall of the pump cylinder. The lower end of the pump plunger is internally threaded to receive the threaded upper end of a stud 112 and mounted on the stud below the lower end of the plunger is a washer 113 of greater diameter than the plunger, a collar 114 and a nut 115 0n the stud locking the washer and collar against the end of the plunger and simultaneously locking the stud against being loosened in the plunger. The lower end of the stud 112 is threaded and receives a head 116 having a resilient cushion 117 at its lower face. The pump cylinder 108 below the collar 109 is provided with diametrically opposite pins 118, 11S and a compression spring 119 is interposed between these pins and the upper face ofthe washer 113 and constantly urges the plunger downwardly.

The groove 106 is provided with a series of ports 120 extending from the groove to the annular space 121 between the outer face of the pump cylinder 108 and the interior of the piston and bounded at its ends by the head of the piston 8 and the upper face of the collar 109. Adjacent the upper face of the collar 109 the pump cylinder 108 is provided with ports 122 extending between the space 121 and the interior of the cylinder 10S. The upper end of the cylinder 108 is closed by a plug element 123 having an axial bore 124 extending therethrough; said bore being enlarged at its upper end and carrying a ball valve element 125 loosely retained therein by across pin 126 and the bore 124 is aligned with an axially disposed bore 127 in the head of the piston 8. The lower end of the plug element 123 is further provided with a bore 125 extending parallel to the bore 124 in which a ball valve element 129 is retained by a cross pin 130, said bore continuing as a smaller diameter concentric bore 131 with resultant formation of a seat for the ball Valve element 129. The bore 131 extends upwardly to about the midlength of the plug and is intersected by a cross bore 132 which extends through the side of the plug and the adjacent wall of the cylinder 108 aiording communication between the upper end of the space 121 and the interior of the cylinder 108.

The exterior of the cylinder 7 at its lower end is provided With diametrically opposite pairs of spaced

anges

133, 133 and pins 134, 134 extending between each of said pairs of ilanges secure the

arms

135, 135 of a yoke member 136 which extends across the lower end of the cylinder in close proximity thereto at right angles to a plane containing the supporting

pipes

9 and 10 for the piston 8 and consequently between said pipes; said yoke having a hole 137 at the mid length thereof for connection to the crosshead and sucker rod supporting means by which the cylinder is reciprocated. As thus dis- 7 posed, the yoke is beneath the piston'and as the yoke and cylinder reach the upper limit of reciprocation, the yoke engages the pad 117 and moves the plunger upwardly against the bias of the spring 119.

Any foam materials escaping past the rings 103 will iirst collect in the groove 106 and since there is less resistance offered by the ports 120 than by the rings 104, the foam forming material will flow into the space 121. From this space the liuid will ilow through the ports 122 into the cylinder 108 and upon upward movement.' of the plunger, will ybe injected into the interior of the cylinder 7 through the aligned bores 124 and 127 the ball valve 129 serving to prevent flow from the cylinder 7 to the cylinder 108. Since the plunger is at the lower end of its movement at all times except for the momentary reciprocation imparted thereto by the yoke 136, there is ample time for uid contained in the space 121 to flow into the cylinder 108. The passage provided by the

bores

128, 131 and 132 prevents the uid in the space 121 from being air bound and allows it to ow freely into the cylinder 108. When the plunger is moved upwardly, the. ball 129 closes this passage causing the uid to be ejected through the discharge bores 124 and 127.

Referring finally to FIGS. 10, ll and l2, there is. shown a means for retaining the foam forming material involving the-principles above described, but applied to a pump jack in which the piston moves within a cylinder as, for instance, a pump jack such as disclosed in my said prior Patent No. 2,664,764. ln this form of the invention, the piston 70 at the lower side thereof is provided with a bore 139 extending through the Wall of the piston and parallel to the axis of the piston from the rear end thereof to a point adjacent the head of the piston. A smaller bore 140 extends preferably in the axial line of the bore 139 from the bottom of that bore through the head of the piston. Pressed into the bore 139 and seated at the bottom thereof is a plug 141 carrying an inlet check valve 142 and a discharge check valve 143. The plug 141 has a circumferential groove 144 at about its mid length and a bore 145 extends radially inwardly 4from this groove and meets a bore 146 spaced slightly inwardly from the side wall of the plug and terminating in a counterbore 147 in which the inlet valve member 142 is loosely retained by a cross pin 148. The forward end of the plug is provided with a coaxially disposed annular recess 149 and the discharge bore 150 extending parallel to the axis of the plug and spaced from the inlet bore 146 from the rear end of the plug and terminates in a counter bore 151 in the bottom of the recess 149 and a cross pin 152 and a spring 153 hold the valve member 143 seated on the shoulder formed by the juncture of the bore 150 and counterbore 151. An inlet port 153 extends through the wall of the piston from the groove 154 therein to the bore 139 at a point that will be opposite the groove 144 in the plug 141 when seated in the bore 139. Thus by reason of the groove 144 and the recess 149, the plug 141 and the valves carried thereby may be inserted in the bore in any rotative position without interruption of the inlet and discharge passages.

The outer end of the bore 139 is counterbored to provide clearance for a compression spring 155 surrounding a pump plunger 156 slidably mounted in the bore and having a packing ring 157 on its inner end; the outer end of said plunger having a head portion 158 against which the spring 155 reacts. Preferably, a collar 159 is pressed to the bottom of the counter bore to provide a seat for the spring 155. The cylinder 69 adjacent the outer end thereof is provided with a stop member 161 which the plunger head portion 158 engages as the piston is brought to the outer limit of its stroke; the final outward travel of the piston serving to move the plunger inwardly and compress the spring 155 expelling any lluid which has entered the pump chamber 160 through the inlet passage in the plug 141 through the outlet passage therein and vthrough the bore 140 into the Vfoam containing portion of the cylinder. The connecting rod 72 carries a collar 162 having a depending arm 163 which engages a lateral extension of the plunger head 158 to limit the extent to which the spring may move the plunger 156 outwardly on an intake stroke; said arm being of such length as to clear the end of the stop member and the head of the plunger having a face 164 (see FIG. l2) which lits the Wall of the cylinder sufficiently closely to prevent rotative movement of the plunger.

Thus any foam material escaping past the rings 70 on Vthe piston 70 will enter the groove 154- and then enter the pump chamber and thence be expelled into the foam containing end of the cylinder for re-use.

Oil well pumps and jacks are started and left unattended and are inspected at intervals such as replenishing the fuel tank of the engine or, if the engine be operating on gas or an electric motor is employed, at such times as lubrication or other attention is required. Accordingly, it is of the utmost importance that safety means be employed to shut down the jack in the event that the sucker rod string should break or the polish rod clamp should pull off and drop the string. Also, in pressurized foam counterbalanced jacks, it is important that the foam materials be kept from leaking out of the only place where such loss might occur, i.e., past the compressing piston. The foregoing description shows how these objectives may be achieved for such pump jacks and that the principles are equally applicable to pump jacks counterbalanced by a moving piston in a stationary cylinder and to a stationary piston in a reciprocating cylinder. Accordingly, the invention is not to be deemed to be limited to the specic forms thereof above disclosed by way of example and it will be understood that the invention includes all such changes and modications in the parts and in the construction, combination and arrangement of parts as shall come within the purview of the appended claims.

I claim:

1. In an oil well pump jack, a frame structure including guidance means for a vertically reciprocating crosshead mounted thereon, means carried by said crosshead adapted to be operatively connected to a sucker rod string with resultant suspension of the sucker rod string therefrom, a stationary piston supported above the path of reciprocation of said crosshead, a cylinder connected to .said crosshead for reciprocation therewith; said cylinder having a closed upper end and an open lower end slidingly engaging said piston, means for supplying said cylinder with a pressurized foam with sufficient pressure to form a counterbalance for the weight of the sucker rod string suspended from said crosshead, a prime mover and devices actuated thereby including a rotatable shaft and means actuated by said shaft for imparting reciprocation to said crosshead on said guidance means, and other devices including means on said shaft responsive to abnormal speed of rotation of said shaft deriving from disconnection of at least part of the sucker rod string from said crosshead during operation of said jack effective t0 dissipate the pressure in said cylinder and simultaneously disable said prime mover.

2. The combination as claimed in claim l in which said other devices comprise a fly ball device on said shaft, a lever having one end thereof engaging said flyball device, spring means restraining action of said fly ball device at normal rates of rotation of said shaft and permitting said fly ball device to move said lever when rotating at abnormal speed, a conduit communicating at one end with the pressure in the interior of said cylinder and with the interior of a second cylinder at its other end, a piston in said second cylinder, a normally closed valve in said conduit, a second normally closed valve interposed in a conduit communicating with the interior of said irst named cylinder at one end and open to atmosphere at its other end, means operatively connecting said piston in said second cylinder with said last named valve, and means connecting said lever with said first named valve effective to open said first named valve upon movement of said lever by said fly ball device with resultant admission of pressure to said second cylinder and consequent movement of said piston in said second cylinder and opening of said second valve and release of the pressure in said first cylinder to atmosphere.

3. The combination as claimed in claim 2 in which said lever is operatively connected to a normally closed switch in an electrical circuit controlling operation of the prime mover and in which actuation of said lever by said ily ball device opens said switch and disables said prime mover.

4. In an oil well pump jack, a frame structure including guidance means for a vertically reciprocating crosshead mounted thereon, means mounted on said crosshead adapted to be operatively connected to a sucker rod string with resultant suspension of the sucker rod string therefrom; said frame structure including at yleast one hollow enclosed frame member additionally serving as a supply tank for pressurized foam, a stationary piston supported above the path of reciprocation of said crosshead, a cylinder connected to said crosshead for reciprocation therewith; said cylinder having a closed upper end and an open lower end slidingly engaging said piston; the supporting means for said piston including a pipe having one end connected to said tank and the other end communicating with the interior of said cylinder through said piston and affording means for supplying said cylinder with a pressurized foam under sufficient pressure to form the counterbalance for the weight of a sucker rod string suspended from said crosshead, a prime mover and devices actuated thereby including a rotatable shaft and means operated by said shaft for imparting reciprocation to said crosshead on said guidance means, and other devices including means on said shaft responsive to abnormal speed of rotation of said shaft deriving from disconnection of at least part of the sucker rod string from said crosshead during operation of said jack operable to disconnect said cylinder from said tank, release the pressure in said cylinder to atmosphere and simultaneously disable said prime mover.

5. The combination as claimed in claim 4 in which said other devices include a fly ball device on said shaft, a lever disposed adjacent a portion of said ily ball device adapted to be moved by said flyball device when said ily ball device is subjected to an abnormally high rate of rotation, a normally open valve in `said piston supporting pipe, a branch conduit extending from said pipe at a point between said normally open valve and said piston and being open to atmosphere, a normally closed valve in said branch conduit, and means operated by said lever effective to close said normally open valve and simultaneously open said normally closed valve.

6. ln an oil well pump jack, a prime mover, a walking beam mounted for oscillation on a Samson post, means connected to one end of said walking beam and actuated by Said prime mover for imparting oscillations to said walking beam and including a rotating shaft and a Pitman actuated by a crank operated by said shaft, means carried by the other end of said walking beam affording operative connection with a pump operating sucker rod string to be suspended from and reciprocated by said other end of said walking beam, means 4for counterbalancing the weight of the sucker rod string comprising a cylinder having one end thereof connected to a supply of foam under sullicient pressure 'to serve as an elastic counterbalancing force, a piston slidable in the other end of said cylinder and connected to said walking beam for movement in said cylinder so that the movement of said walking beam incident to the down stroke of the sucker rod string moves said piston into said cylinder with resultant additional compression of pressurized foam therein, and devices including a ily ball device on said shaft and mechanism operated thereby in the event of abnormal speed of rotation of said shaft, as in the event of disconnection of at least a part of the sucker rod string from said walking beam, effective to release the counterbalancing pressure of the "foam in said cylinder to atmosphere.

7. The combination as claimed in claim 6 in which said mechanism comprises a lever pivotally mounted adjacent to said ily ball device and having a portion thereof disposed in close proximity to a portion of said lly ball device, spring means holding said lever to restrain said ily ball device from operating at normal speed of rotation of said shaft, a conduit extending from said cylinder to a second cylinder, a piston in said second cylinder, a normally closed valve opening said cylinder to atmosphere and having means engageable by said piston in said second cylinder to be moved to open position and a normally closed valve in said conduit `operatively connected to said lever.

8. The combination as claimed in claim 7 in which said lever is additionally connected to a normally closed switch in a circuit controlling operation of said prime mover and -operable in the event of actuation of said lever by said fly ball device to open said switch and disable said prime mover.

9. In a deep well reciprocating pump operating jack including a base carrying reciprocating devices supporting the'load of the sucker rod string extending therefrom to the pump, a prime mover operatively connected to said devices for actuating the pump through reciprocation of the sucker rod string by said devices, and means for counterbalancing the load of the sucker rod string and including a relatively moving piston and cylinder interposed between said base and said reciprocating devices and a quantity of pressurized foam in said cylinder and exerting an elastic force therein sulilcient to support at least a portion of the load of the weight of the sucker rod string, a normally closed valve interposed between the foam in said cylinder and the atmosphere, and means for opening said valve to release said pressurized foam, including devices responsive to an effect deriving from abnormal operation of said pump jack by reason of unintentional disconnection of at least a part of the sucker rod string from said reciprocating devices and consequent reduction of the load imposed thereon by the sucker rod string.

l0. A pump operating jack as claimed in claim 9 which further includes an electric circuit controlling operation of said prime mover, a normally closed switch in said circuit, and means `operatively connected with said valve opening means effective to open said switch and to stop operation of said prime mover simultaneously with the opening of said valve.

ll. A pump operating jack as claimed in claim 9 in which said reciprocating devices are actuated by a rotating shaft driven by said prime mover and in which said valve opening devices include centrifugal force responsive devices carried by said shaft and effective to open said valve in the event of an increase in the speed of rotation of said shaft deriving from a reduction in the load imposed thereon by the weight of the sucker rod string by reason of unintended disconnection of at least a part of the sucker rod string during operation of the jack.

References Cited in the file of this patent UNITED STATES PATENTS Blackburn I an. 5, 1954