US2694933A

US2694933A - Motion converting mechanism

Info

Publication number: US2694933A
Application number: US125769A
Authority: US
Inventors: Luther A Blackburn
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-11-05
Filing date: 1949-11-05
Publication date: 1954-11-23
Anticipated expiration: 1971-11-23

Description

Nov. 23, 1954 A. BLACKBURN 2,694,933

MOTION CONVERTING MECHANISM Filed Nov. 5, 1949 4 Sheets-Sheet l Z3 INVE/WUR 23 A; LUTHER A. BLACKBURN A TTORA/EVS Nov. 23, 1954 A. BLACKBURN 2,694,933

MOTION CONVERTING MECHANISM Filed Nov. 5, 1949 4 Sheets-Sheet 2 //Vl//VTOR /6 LUTHER A BLACKBURN A TTORNEVS Filed NOV. 5, 1949 1954' A. BLACKBURN 2,694,933

MOTION CONVERTING MECHANISM 4 Sheets-Sheet I5 2 Z; w LUTHER A. g ii fim -1 W: W

Nov. 23, 1954 2., A. BLACKBURN 2,694,933 MOTION CONVERTING MECHANISM Filed Nov. 5, 1949 4 Sheets-Sheet 4 fmz @111 //V [/5 N TOR LUTHER A. BLACKBURN ATTORNEYS United States Patent MOTION CONVERTINGMECHANISM Luther A. Blackburn, Eagle Rock, Calif. Application November's, 1949, SerialN-o; 125,769

11 Claims. 1 (Cl. 74-37) This invention relatesto deep -well. pumps and more specifically contemplates'long strokezpumping apparatus adapted particularly for oil wells.

in pumping deep wells, the resilience of'thepump rod string by which the pump isactuated, and ofthetubing string through which the fluid raised by thepump is conducted to well surface, resultsin very substantially dissipating the effective stroke of the pump plunger as-the weight of the fluid column is alternately transferre'd'from the rod string to the tubing string and vice versa at the end of each stroke. Accordingly, in order to obtain maximum eificiency, pumping equipment has been devised to provide for a stroke of a length sufficient to min-imize' the effect of elongation and contraction ofthe tubingand rod strings during operation. One form of such equipment which possesses numerous advantages, comprises a crosshead, to which the rod string'is connected, reciprocated vertically by means of endless chains. Ieretofore in order to obtain the essential'balance of the crosshead and avoid its lateral thrust against the frame and pump rod, four pump-actuating chainshave been required. 'While such equipment is very effective the initial cost of-such devices, is for many applications, exorbitant.

The present invention is concerned primarily with a chain-actuated pumping jack embodying only a-single pair of chains operable-to actuate the pump during its effective or pumping stroke and to idle'on the oppositestroke of the pump plungenthe weight of' the fluid-column and of the rod string being utilized to lower the pump rodin the well on alternate strokes.

More specifically, a principal object'of the presentinvention is to provide a long stroke deep well'pumping' jack comprising essentially an upright frame-for the' verticallyguided movement of a pump rod clamping assembly, reciprocated in response to movementofalternatereaches of a single pair of vertically disposed endless chains, and the weight of the fluid column'in the well, the movement of the chains being transmitted to the clamping assembly during the pumping stroke through a pivoted assembly adapted to follow the chains throughout their circuits.

Another and highly important-object hereof'is to provide a chain-actuated pumping jack wherein the upwardly moving reaches of the chain are disposed in diametric alignment but at opposite sides of the rod string to be actuated and are connected to the latter-by pivoted arms adapted to assume a parallel relationship with the direction of movement of the actuating elements-of the-chains and the rod string during the pumping stroke.

Another object is'to provide a method of, and apparatus for, pumping deep wells, in accordance withwhich the weight of the pumping rod string and fluid column in'the tubing string is partiallybut not wholly counterweighted during the effective or upper stroke of the rod string, and the diflerence between the weight of the rod'string,'and the counterweight is utilized to actuate theipump duringits opposite stroke.

Another highly and important objectis'the'provision of a chain actuated pumping jack'of'the character referred to embodying acounterweight vertically reciprocable in the frame and operable'tooppose theweight of thefiuicl column in the tubing string through a pair of chains passingover sprockets in the crown'blo'ck'and connected to the rod string, the sprockets being keyed together whereby the'counterweight opposes anylate'ral'thru'st'imposed upon the pump rodbythe'pump'actuating'mechanism.

Another object isthe provisionofmeans to resiliently absorb the weight of the fluid column in the well at the lower end of the stroke as the chains pick up the load, and to relieve in a similar manner the rod string of the weight of the fluid at the upper end of the stroke.

Another object is to provide means for elevating the jack upon the roller for-facile movement of the unit from an operative positionover the well to a position laterally of the well so as to provide servicing of the pumping equipment, cleaning of the casing string and replacement of the rod string, tubing and pump barrel.

Other objects and salient features of my invention, such as simplicity of construction, economy of manufacture, facility of servicing, adjustabilit'y to meet the requirements of specific installations, and maximum efiiciency per unit of power, will be apparent to those of skill in the art upon an examination of the following description read in the light of the accompanying drawings, in which:

Fig. l is a side elevation, partially broken away, of a pumping jack embodying my invention;

Fig. 2is an elevation of the apparatus taken at right angles to the view of Fig. 1;

Fig. 3 is a perspective view of the pump rod guide and supporting assembly illustrating the connection thereto of the actuating mechanism and counterweight chains, the parts being in their respective positions assumed during theup stroke of the pump rod string;

Fig. 4 is a side elevation of the pump rod supporting mechanism illustrating one of the pivoted arms in the position which it assumes on the down stroke of the rod string;

Fig. 5 is a horizontal sectional view of the frame showing the upper drive sprockets of the actuating mechanism and-the relationship of the counterweight guides, omitting the rod string, its supporting assembly and the counterweight;

Fig. 6 is an enlarged elevation, partially broken away, of one of the upper sprockets for the drive chain, depicting particularly the means by which the tension of the chain, associated therewith, is adjusted;

Fig. 7 is a broken horizontal sectional view through the vertical guides of one of the adjustable mountings for the upper sprockets; V

Fig. 8 is a sectional view similar to Fig. 7 taken through the adjusting screw of the upper sprocket supporting mechanism and showing the stationary block relative to which the upper sprockets are shifted;

Fig. 9 is an end elevation of one of the rails, also showing in elevation the means'by which the frame is elevated upon rollers to facilitate the shifting of the frame onto and ofi' the well;

Fig. 10 is a broken side elevation of the assembly shown in Fig. 9;

Fig. 11 is a frame;

Fig. 1-2 is an exploded elevation of one of the lower sprocket assemblies;

Fig. 13 is a side elevation of the pivoted arm assembly associated with the rod string clamp and guide mechanism depicting particularly the yoke elements for pivotally engaging the respective actuating chains;

Fig. 14 is a fragmentary view of the brake assembly showing the drive sprocket in broken section;

Fig. 15 is a vertical sectional view through the counterweight sprocket and pulley assembly illustrating the keying'of these parts upon a common shaft.

Referring to the drawings more in detail, the numerals of which indicate similar parts throughout the several views 15 designates each of a plurality of sills covering the pit of an oil well and 16 and 17 refer to the casing and tubing strings, respectively, of the well proper. 18 indicates a conventional tubing head through which the polish rod 19 to be actuated reciprocably projects. Mounted on the sills 15 in parallel relation and equispaced to opposite sides of the well are a pair of rails 20 upon which the'pumping jack, embodying 'myinvention is supported. The frame of the structure comprises two channel irons 21 and two angle from 22, vertically disposed and arranged at the corners, respectively, of a rectangle which is slightly narrower than the distance between the rails 20. The channel 21 and the vertical angle iron frame member 22 at each side of the structure perspective view of the counterweight parallel to the respective rails are mounted upon a common horizontal angle iron 23. The vertical disposition of the channels 21 is reinforced by a pair of inclined braces 24 having their lower ends mounted upon extensions of the angle irons 23, respectively. The frame is further reinforced by a plurality of channels 25 and angle irons 26 extending between the vertical channels 21 and complementary angle irons 22 which together define the corners of the frame.

The cross-sectionally rectangular form of the top of the frame is maintained by a crown block 27 comprising angle irons 28 bolted or otherwise rigidly secured between the upper ends of the vertical angle irons 22 and channels 21. At each of the four corners of the crown block 27 an upstanding perforated lug 29 is secured to facilitate the removal of the block when required, or the lifting of the entire unit for transportation.

Each of the lower horizontal angle irons 23, forming the foundation of the frame structure, is welded to the side of an elongated box frame 30, comprising a pair of channel irons 31 having their edges opposed and welded together. The box frames are normally supported upon the respective rails 20 but are adapted to be elevated from the latter in response to the manual lowering of rollers 32 housed within the box frames. Four rollers 32 are provided, each being flanged so as to engage opposite edges of the rail 20 with which it is associated so as to prevent lateral displacement of the structure with respect to the well. Each of the rollers 32 is journalled upon a shaft 33, having its ends mounted in the legs of an inverted U-shaped retainer 34. The rollers 32 and the retainers 34 in which the former are journalled, respectively, are disposed within the elongated box frames adjacent the four corners of the pump jack and are secured against longitudinal displacement within the respective box 00 frames by a series of stud bolts 35 which extend through vertical slots 36 formed in the sides of the opposing channels 31 of each box frame 30 and adjoining angle irons 23 and are threaded in the respective retainers 34. Thus each retainer and the roller 32, rotatably mounted therein, is vertically reciprocable relative to the box frame 30 and the superstructure of the pump jack. The lower periphery of each of the rollers 32 projects through a lower opening 37 in the channels 31 of which the box frames are composed and is normally held in contact with the rail therebelow by pressure applied to the upper surface of the retainer 34 by a bearing member 38. Interposed between the bearing member 38 and retainer 34 are a series of ball bearings 39 to facilitate relative rotation between the member 38 and retainer. The bearing member 33 is formed integrally with the lower end of a screw 40 threaded through a nut 41, non-rotatably fixed at the top of the box frame 31. A capstan 42, rigidly secured to the upper end of the screw 40, enables manual rotation of the latter and of the bearing member 38, in an obvious manner, so as to elevate the adjacent end of the box frame and the corresponding corner of the jack relative to the rail 20 and roller 32. With each corner of the pumping jack thus raised upon the rollers 32 the entire unit may be rolled upon the rails 20 to a position laterally of the well when occasion demands.

At one side of the well a concrete foundation 43 is provided for a power unit. Superposed upon the foundation 43 are a pair of I-bearns 44, held in parallel, spaced relationship by a spacer plate 45. Securely mounted upon the I-beams is an engine 46 for actuating the pumping mechanism hereinafter described. The engine 46 is normally held in adjusted position upon the foundation 43 but may be shifted laterally with respect to the well by four screws 47 which are threaded through lugs 48, mounted to the foundation and bearing against the ad jacent I-beam 44. The pulley 49 of the engine 46 is connected to a drive pulley 50 of the pumping jack by a belt 51, both

pulleys

49 and 50 and belt 51 being preferably enclosed in a housing 52 to prevent injury to workmen during operation of the unit. The drive pulley 50 of th: jack is keyed upon a shaft 53, journalled in bearings 54 carried by a mounting plate 55, projecting laterally from the frame of the jack and welded or otherwise secured to the vertical channel 21 and angle iron 22, defining the adjacent side of the jack frame.

At the level of the pulley shaft 53 and at each side of the frame forming a right angle with the shaft is a transverse vertical plate 56 welded or otherwise secured across the vertical channels 21 and angle irons 22, respectively.

Rotatably supported by each of the plates 56 is a drive sprocket and gear assembly adapted to be actuated from the pulley shaft 53 by a pairof spur gears 57, splined to the shaft in alignment with opposite sides of the jack frame. Each sprocket and gear assembly (illustrated in Fig. 12) comprises a stub shaft 58, secured rigidly in a suitable manner to the adjacent plate 56 so as to pro ect into the frame. A pair of roller bearings 59 carried by each shaft 58 rotatably mount a gear 60 which is held in mesh with one of the pulley-shaft pinions 57 at the corresponding side of the unit. The hub of the gear 60 projects laterally and is formed with a fiat surface against which a chain drive sprocket 61 is attached by a series of screws 62. The gear 60, sprocket 61 and the bearings 59 for the same are held on the stub shaft 53 by a disk 63 secured to the end of the shaft by a pair of screws 64.

Endless drive chains 65, engaged with the respective sprockets 61 are supported in the upper end of the jack by idler sprockets 66. Each of the sprockets 66 is journalled upon a stub shaft 67 projecting laterally from a slide 68, engaged between a pair of vertical channels 69, welded at their lower ends in spaced, opposed relation to the cross brace angle iron 26. A hub spacer 70, encircling the shaft 67 between the sprocket 66 and slide 68 maintains the sprocket in the vertical plane of the drive sprockets 61 therebelow for the corresponding chain 65. The sprocket 66 and slide 68 at each side of the frame are movable vertically to determine the proper tension of the chain 65, relative to a block 71, securely fitted between the guide channels 69 at the adjacent side of the frame. A screw 72, threaded upwardly through the block 71, is adapted to bear against the under side of the slide 68 and support the same in accordance with the adjustment of the screw 72. The adjusted position of the slide 68 is reinforced by a clamping plate 73 of a width sufiicient to overlie the outer edges of the opposed channels 69 and is attached to the slide 68 by screws 74. Thus each of the sprockets 66 may be elevated, upon relieving pressure of the clamping plate 73 on the channels 69, incident to the threaded adjustment of the screw 74.

It will be observed that the upper and lower sprocket assemblies for the chains 65 are supported in positions which locate complementary vertical reaches of the chains in diametric alignment with the vertical center of the pumping jack. Thus, with the box frames 30, defining the bottom of the pumping jack, equi-spaced at opposite sides of the well, the polish rod 19 of the pump, projecting upwardly through the tubing head 18 of the well, will extend directly between these reaches of the chains 65.

The chains are operatively connected to the polish rod 19 of the pump by a cross frame 75, reciprocably mounted within the vertical frame of the jack. This mechanism illustrated more clearly in Fig. 3 comprises a pair of bars 76, arranged in parallel, spaced relationship, and upright members 77, connected, respectively, to opposite ends of each of the bars 76. The upper end of the frame 75 is defined by a yoke 78, to opposite sides of which the uprights 77, at each side of the frame, are secured. The yoke 78 is provided with an intermediate arcuate offset portion 79 to permit upward projection of the polish rod 19, when required, as will appear. The bars 76 defining the bottom of the cross frame 75 are maintained in spaced relationship by a saddle plate 80, secured across the bars 76 intermediate their ends, and between opposite corresponding ends of the bars, a roller 81 is journalled. Similarly a roller 82 is journalled between the upper ends of each pair of opposed uprights 77. The

rollers

81 and 82 of the pair at each side of the cross frame 75 project laterally of the frame for operative engagement with guide channels 83, respectively, which are rigidly mounted in vertical position, in opposed relationship, to the cross braces 25 at the opposite sides of the frame which are parallel to and mounted upon the respective rails 20. Thus the cross frame 75 is vertically reciprocable between the channels 83 in the plane of the polish rod 19 which, upon operative assembly of the unit, projects upwardly between the bars 76 forming the lower part of the cross frame. The saddle plate 80 is formed with a central opening 84 to accommodate the polish rod 19 and forms a seat for a helical spring 85 encircling the rod. The upper end of the spring 85 is covered by a circular plate 86 through which the rod projects and 7 upon which a rod clamp 87 of conventional construction,

engaged with the polish rod, is adapted to bear. Thus the Weight of the rod string 19 is resiliently transmitted to the cross frame 75 by the spring 85.

Projecting laterally from .the outer surface of each lower bar 76 of the cross frame 75 is a stub shaft 88 which isengaged by a bearing 89rigidly secured to the lower end of a chain arm 90. The upper ends of the arms 90 are connected. by a transverse bearing mounting 91 (Fig. 13) below the yoke'78 of the frame 75. A self-aligning bearing 92 carried by the mounting 91 provides rotatable support fora rod 93 which extends laterally above the ends of the arms 90 into the line of movement of the respective chains 65. The ends of the rod 93 are formed with lateral cut outs 94 to provide chain yokes 95 which partially encompass and are secured to horizontally-aligned complementary links 96 of the respective chains by pins 97.

It will be observed that upon actuation of the chains 65 by the power unit the cross frame 75 will be elevated during upward movement of the links 96 of the chains 65 with which the double-yoked rod 93 is connected, this movement being transmitted through the arms 90 to the bars 76 of the cross frame 75. No lateral thrust is developed during this movement due to the parallel reiationship between the arms 90, upwardly moving reaches of the chains 65 and the pump rod string 19. As above indicated the upward movement of the cross frame 75 is transmitted to the polished rod 19 and the pump so as to elevate the fluid column in the well incident to actuation of the pump on its effective stroke. Upon reaching the upper sprockets 66 the double-yoked rod 93 is swung laterally so as to follow the links 96 to which it is connected over the sprockets, the arms 90 pivoting on the stub shafts '88 which project from the lower end of the cross frame 75. Due to the angular disposition of the arms 90 during downward movement of the links 96 to which the rod 93 is connected, any tension by the chains 65 upon the arms 90 during the lowering of the rod string would tend to exert a lateral thrust upon both the polished rod and cross frame 75 and accordingly, as is hereinafter more in detail described, the weight of the rod string and the fluid column in the tubing string is utilized to lower the cross frame.

In order to further obviate any objectionable results from the application of excessive power to the chains 65 during the downward stroke of the pump, I provide arcuate cut outs 93 in the inner edges of the uprights 77 at the cross frame 75 toward which the arms 90 are inclined during the downward movement of the cross frame in order to accommodate the double-yoked rod 93 of the frame assembly. The cross frame is so proportioned relative to-the disposition and diameters of the sprockets to compel the double-yoked rod 93 to bear against the lower arc of the cut outs 98 during the downward movement of the frame and thereby directly transmitthe tension of the chains 65 to the frame through the uprights 77 in which the cutouts are formed.

Upon reaching the lower arcs of the drive sprockets 61 the rod 93 of the frame assembly moves with the links 96 to which it is connected, into the upwardly moving reachesof the chains 65, returning the arms 90 to a vertical position. In order to stabilize the pivoted arms as the load, comprising the weight of the rod string 19 and fluid column is picked up by the chains and to minimize oscillation of the pivoted arms 90 at this stage of the cycle of operation, the lower bars 76 of the cross frame are provided with a pair of lugs 99 against which flanges of the bearings 89 at the lower ends of the arms 90 abut as the arms re-assume vertical position. It will be observed that the shock upon the rod string 19 and pump actuating mechanism of assuming the load is absorbed in part by the spring 85 interposed between the polished rod clamp 87 and cross frame saddle plate 80 It will be observed that the offset 79 in the yoke 78 permits projection of the rod string above the cross frame when the pivoted arm assembly is laterally displaced so as to facilitate adjustment in the effective length of the pump rod as well as initial operative assembly of the unit on the well.

In accordance with the preferred construction the pump rod string and fluid column in the well are partially counterweighted. The counterweight 100 is composed of a plurality of fiat weights 101, rectangular in plan, which are suspended in vertical series in a counterweight frame 102, vertically reciprocable between correspondingly-disposed guide rails at the side of the pumping jack. The vertical guides for the counterweight frame 102 are composed of the-two'an-gle irons i22- of the pump jack frame properand two additional vertical angle irons 103, arranged to define the corners of atrectangle only slightly larger than the dimensions of-the frame 102 to be accommodated. The counterweight frame comprises a pair of side plates 104'havingtheir vertical edges enclosed in angle iron wear'members105, and a transverse bottom 106 welded or otherwisesecured between the side plates 104, for the support of the weights 101. At the upper end of the counterweight frame 102 are a pair of transverse channels 107 arranged with their backs in opposition to one another and inspaced relation, their ends being rigidly connected to the respective side plates 104. The ends of a pair of counterweight chains 108 extend downwardly from the top of the unit between the channels 107 and are secured to metal straps 109 which are bound firmly to a cushioninghbar 110 at points offset but equi-spaced from the vertical center of the frame. The ends of the bar 110 project into vertical slots 111 in the respective side plates 104 of the counterweight frame whereby the bar 110 and chains 108 may be raised or lowered relative to the counterweight frame 102 and the weights 101 carried thereby. The bar 110 is normally maintained in the lower extremities of the slots 111 by a series of helical springs 112, interposed between the bar 110 and the channels 107 thereabove, the springs 112 being adapted-to compress slightly in response to sudden tension upon the chains, as will appear. It willbe appreciated that the springs of the counterweight frame supplement thefunction of the spring 85 in absorbing the shock of the reversalof the movement of the cross frame and pump rod.

The chains 108 extend upwardly to the top of the pumping jack where they pass over a pair of sprockets 11-3, keyed in exact alignment on a common shaft 114, as indicated at 140 (Fig. 15) which is journalled in bearings 115 supported on beams 116 carried by the angle irons 28 connected between the upper ends of the

verticals

21 and 22. The sprockets 113 for the counterweight chains 10% are offset with respect to the middle of thejack frame so as to locate the innermost arcs of the sprockets in alignment with the plane of the channels 83 between which the cross frame 75 reciprocates. The reaches of the chains 108 depending from the inner lateral .arcs .of the respective sprockets 113- are connected at their lower ends by suitable straps 117 to the yoke 78 of the cross frame '75 at opposite sides of the offset 79 therein. It will thus be seen that the total weight of the counterweight assembly being transmitted over the sprockets 113 at the top of the pump jack to the reciprocating cross frame 75 opposes the weight of the rod string 19 and of the fluid column in the well. In accordance with the preferred method of operation'and utility of apparatus of the type hereinabove described, weights 101 are added to the counterweight frame 102 until the total weight of this assembly balances the well load and then weights are removed until the engine idles on the downstroke. In order to avoid damage to the equipment or possible injury to workmen, safety means is incorporated in the unit to prevent a fall of the counterweight frame 102 in the event of fracture of the chains 108. 'For this purpose, cables 118 are suspended from pulleys 119 keyed to the sprocket shaft 114 adjacent the respectice sprockets 113. Corresponding outer ends of the cables 118 are secured by suitable means to the straps 109 by which the counterweight chains 108 are connected to the cushioning bar 110 of the counterweight frame 102. The inner opposite ends of the cables 118 are similarly attached to the yoke 73 of the cross frame 75 adjacent the respective chains 102 and in alignment with the pulleys 113 from which they depend. It will be understood that the cables 118 are lax and do not normally support the counterweights 100. Should either of the chains 108 break, however, thecables 118 are under sufficient tension to immediately assume the load and avoid both the binding of the counterweight frame 102 in the

guide angle irons

22 and 103 as well as inadvertent gravitation of both the counterweight frame and the cross frame 75.

The counterweight sprockets 113 and pulleys 119 are enclosed by a cover 120 supported on the crown block 27. 121 indicates the ladder secured to the side of the frame, and 122 a railing mounted upon the crown block 27 to facilitate access by workmen to the various working parts.

With the cross frame in which the polish rod 19 is clamped at the lower end of its stroke the counterweight frame 102 is disposed adjacent the top of its range of movement. As the weight of the counterweight assembly is less than that of the combined weight of the rod string and fluid column, power from the engine 46 is required to actuate the chains 65 and elevate the cross frame and polish rod on the effective stroke of the pump. As the pivoted arms 90 reach the top of the stroke and swing over the upper arcs of the idler sprockets 66 the counterweight frame will be at the bottom of its range of movement. At the beginning of the down stroke the weight of the fluid in the well is transferred to the tubing string, but as the remaining well load, including the weight of the rod string, is slightly in excess of that of the counterweights, the rod string will, during the down stroke, gravitate at a velocity substantially equal to that of the movement of the rod string in response to the power of the engine during the upstroke. With the unit balanced as above described, the engine merely idles during the down stroke of the pump rod. At the beginning of the upstroke the engine is reactivated by conventional control mechanism to assume the greater load which includes the weight of the fluid in the well as the momentum of the drive mechanism is dissipated.

In order to further control the velocity of operation of the device and to provide a safety factor in the event of the breaking of the counterweight chains and cables 118 or rod string, I provide a manually operable brake mechanism (Figs. 1 and 14) adapted to frictionally engage the internal surface of the rim of the drive pulley 50, comprising a brake shoe 123 pivoted at 124 to a suitable bracket mounted to the side of the frame. The opposite end of the brake shoe 123 is engaged by an eccentric 126 formed integrally with the end of a brake rod 127, journalled in bearings attached to the side of the frame. A lever 128, secured rigidly to the brake rod 127 is engaged by linkage 129 extending downwardly to adjacent the bottom of the jack, where a suitable manually operable brake lever assembly 130 of conventional construction is provided to exert tension upon the linkage 129. The swinging of the lever 128, incident to tension of the linkage 129, is effective to turn the brake rod 127 and actuate the eccentric 126, putting pressure upon the brake shoe 123 and through it, creating friction with the pulley rim. It will be appreciated that the brake mechanism may be controlled and actuated by well known mechanism in response to an excessive increase in the velocity of movement of the pump rod.

Effective operation of chain-actuated pumping units of the character contemplated depends upon continuous and effective lubrication of the drive chains 65 as well as of the counterweight chains 108. The present invention contemplates the incorporation of a force-feed lubricating system comprising a pump 131 mounted upon a bracket 132 secured to the side of the frame below the pulley shaft 53. The pump 131 is actuated by a belt drive 133 from a pulley 134 carried by the end of the main pulley shaft 53 so as to force a continuous flow of oil through four tubes 135 leading to the drive sprocket 61, idler sprockets 66 and counterweight chain sprockets 113, respectively. Each of the tubes 135 terminates above the upper arc of the sprocket with which it is associated so as to continually direct oil onto the sprocket as the same are turned in response to rotation of the pulley shaft 53. The drive chains 65 and

sprockets

61 and 66 are par tially protected from dust, sand and other debris by a pair of

shields

136 and 137, mounted vertically within the frame and partially encircling opposite sides of this mechanism.

Another feature of the invention resides in the provision of a short section 19a of polish rod within the cross frame 75. The section 19a may remain permanently in the cross frame even while moving the unit on and off the well. To this end, the section 19a is of a length sufficient to extend below the lower edges of the plates 56 when the cross frame is in its lowermost position. The lower end of the section 19a is connected to the polish rod 19 by a conventional coupling 138.

In preparing the unit for movement from the well over the rails 20 the cross frame 75 is lowered until the coupling 138 is below the plates 56 whereupon a rod clamp such as that shown at 87 in Fig. 3, is engaged with the rod 19 immediately above the tubing head 18 for the support of the rod string in the well. Thereafter, the polish rod 19 and section 19a are disconnected at the coupling 138, and the belt 51 is disconnected from the drive pulley, whereupon the unit is ready to be moved without the necessity of disturbing the tubing head 18.

While the embodiment illustrated and described represents a preferred construction of a pumping jack embodying my invention, it will be appreciated that numerous changes in size, design, shape, number and proportion of the various parts may be made, and that the arms 30 may be pivoted directly to a suitable clamp for the rod string and the latter guided in its vertical movement by structurally separate auxiliary means, thus dispensing with the cross frame, without departing from the spirit of my invention as defined by the appended claims.

What I claim and desire to secure by Letters Patent is:

1. In a pump unit of the character described, a crosshead, an upright frame to guide said crosshead for vertical reciprocation, a polish rod clamp carried by said crosshead, a pair of endless chains disposed at opposite sides of said crosshead, means to move upwardly reaches of said chains located at diametrically opposite sides of said polish rod clamp, and a pair of arms pivotally connected to said crosshead and to said reaches, respectively, of said chains, the upwardly moving reaches of said chains being disposed in a common vertical plane substantially coinciding with the axis of pivoting of said arms to said crosshead.

2. In a pump jack, a pair of chains, a pair of verticallyaligned sprockets supporting each of said chains, means to actuate said sprockets to move corresponding vertical reaches of said chains, upwardly, a crosshead vertically reciprocable between said upwardly moving reaches of said chains, a pair of arms pivoted to said crosshead at points located between the vertically moving reaches of said chains, and means to pivotally connect said arm to said upwardly moving reaches of said chains, respectively.

3. In a pump jack for reciprocating a sucker rod string for actuating a pump in a well, a vertically movable crosshead, a polish rod clamp carried by said crosshead for engagement of said rod string, means comprising an endless chain to reciprocate the crosshead, including an arm pivoted between said crosshead and said chain, the point of pivoting of said arm to said chain being disposed in a vertical plane coinciding with the axis of pivoting of said arm to said crosshead during the upstroke of said crosshead and movable out of said plane during the down stroke of the crosshead.

4. In a pump jack for reciprocating a sucker rod string for actuating a pump in a well, a vertically movable crosshead, a polish rod clamp carried by said crosshead for engagement of said rod string, means comprising an endless chain to reciprocate the crosshead, including an arm pivoted between said crosshead and said chain, the point of pivoting of said arm to said chain being disposed in a vertical plane coinciding with the axis of pivoting of said arm to said crosshead during the upstroke of said crosshead and movable out of said plane during the down stroke of the crosshead, and a counterweight to substantially counterbalance the weight of the rod string on the downstroke of the latter.

5. In a pump jack for reciprocating a rod string in a well, a crosshead, means to guide said crosshead in vertical movement, a rod clamp carried by said crosshead to engage said rod string, a pair of endless chains, each comprising an upwardly-moving reach and a downwardly moving reach, said chain being operatively disposed with the upwardly moving reaches thereof located at diametrically opposite sides of said rod clamp, a power unit to actuate said chains, and arms pivoted to said crosshead and connected to said chains to transmit movement of said upwardly moving reaches of said chains to said crosshead and rod clamp, the upwardly moving reaches of said chains being disposed in a vertical plane coinciding with the axis of pivoting of said arms to said crosshead.

6. In a pump jack for reciprocating a rod string in a well, a crosshead, means to guide said crosshead in vertical movement, a rod clamp carried by said crosshead to engage said rod string, a pair of endless chains, each comprising an upwardly-moving reach and a downwardly moving reach, said chains being operatively disposed with the upwardly moving reaches thereof located at diametrically opposite sides of said rod clamp, a power unit to actuate said chains, means to transmit the movement of said upwardly moving reaches of said chain to said crosshead and rod clamp, and means to substantially counter- 9 balance the weight of the rod string on the downward stroke of said crosshead.

7. In a pump jack, a crosshead comprising a frame, a shaft pivoted in said frame, a pair of arms carried by said shaft for pivotal movement relative to said crosshead, a bearing carried between said arms, a member extending through said bearing, a pair of chains to vertically reciprocate said crosshead, and means to pivotally connect said chains to the ends, respectively, of said member.

8. In a pump jack for reciprocating a rod string, a frame, a crosshead vertically reciprocable in said frame, means carried by the center of the crosshead engaging the rod string to be reciprocated, means comprising an endless chain to reciprocate the crosshead, including an arm pivoted between said crosshead and said chain, the point of pivoting of said arm to said chain being disposed in a vertical plane coinciding with the axis of pivoting of said arm to said crosshead during the upstroke of said crosshead and movable out of said plane during the downstroke of the crosshead, a counterweight vertically reciprocal in said frame, a shaft journaled in the upper portion of said frame, a pair of sprockets fastened to said shaft to rotate in unison with the shaft, a pair of chains passing over and engaged with the respective sprockets, and connected between said crosshead and said counterweight, said chains being connected to said crosshead at points equispaced from and at opposite sides of said first-named means, to balance the crosshead during operation.

9. A pump jack according to claim 8 in which the teeth of the sprockets are in the same time relationship with each other.

10. In a pump jack for reciprocating a sucker rod string for actuating a pump in a well, a vertically movable crosshead, a polish rod clamp carried by said crosshead for engagement of said rod string, means comprising an endless chain to reciprocate the crosshead, including an arm pivoted between said crosshead and said chain, the point of pivoting of said arm to said chain being disposed in a ver tical plane coinciding with the axis of pivoting of said arm to said crosshead during the upstroke of said crosshead and movable out of said plane during the down stroke of the crosshead, a power unit to actuate said chain mechanism, and a counterweight to counterbalance slightly less than the entire load of the rod string during the down stroke of the rod string so as to permit said power unit to idle during alternate strokes of the pump.

11. Apparatus according to claim 7 in which the frame has an indentation, and on the upstroke of the crosshead the arms are pulled into a vertical plane by the chains, and on the downstroke of the crosshead the arms pivot out of the vertical plane so that the member rests in the indentation, whereby the arms are provided with stability during the downstroke.

References Cited in the file of this patent UNITED STATES PATENTS 25 Number Name Date 269,775 Cannon Dec. 26, 1882 1,756,089 Hunter Apr. 29, 1930 1,774,321 Detfurth -2 Aug. 26, 1930 1,826,760 Foster Oct. 13, 1931 30 2,292,427 Blackburn Aug. 11, 1942 2,351,183 Blackburn June 13, 1944 2,465,613 Spaulding Mar. 29, 1949 2,475,103 Mannist July 5, 1949