US2894723A

US2894723A - Drilling apparatus

Info

Publication number: US2894723A
Application number: US677107A
Authority: US
Inventors: August W Gustafson
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-08-08
Filing date: 1957-08-08
Publication date: 1959-07-14
Anticipated expiration: 1976-07-14

Description

July 14, 1959 Filed Aug. 8, 1957 A. W; GUSTAFSON DRILLING APPARATUS 5 Sheets-Sheet 1 I IN VENT OR uausr' msasvrxsa/v,

QW -A M ATTORNEY July 14, 1959 A. w. GUSTAFSON 2,894,723

DRILLING APPARATUS 5 Sheets-Sheet 2 Filed Aug. 8, 1957 .12), i-lllllizlllrr I N VENTOR aws-7- 144 61/5 727Fso/v,

ATTORNEY July 14, 1959 A. w. GUSTAFSON 2,394,723

DRILLING APPARATUS Filed Aug. 8. 1957 5 Sheets-Sheet s INVENTOR mrmsasww ATTORNEY July 14, 1959 A. w. GUSTAFSON DRILLING APPARATUS 5 Sheets-Sheet 4 Filed Aug. 8, 1957 INVENTOR am?- m aasm/isa/v,

ATTORNEY July 14, 1959 Filed Aug. 8, 1957 A. w. GUSTAFSON v 2,894,723

DRILLING APPARATUS 5 Sheets-Sheet 5 INVENTOR flUQSTl KGUWFEOM B 9 (LL ATTORNEY United States Paten DRILLING APPARATUS August W. Gustafson, Corpus Christi, Tex.

Application August 8,1957, Serial No. 677,107

3 Claims. (Cl. 255-22) The present invention relates to drilling apparatus and more specifically pertains to a portable drilling rig adapted for geological exploration and the like.

An object of the invention is to provide a lightweight compact portable and readily transportable drilling rig which may be moved over rough terrain and adaptable for a one man operation through the use of a hydraulic system which controls operation during drilling and which may be employed for drill stem removal and for applying force to the bit during drilling operation.

A further object of the invention is to provide drilling apparatus wherein at Kelly bar forms a permanent part of the drilling rig and driven by power applied to the upper end of the drilling rig tower including a reverse drive for the kelly bar so as to provide power means for connecting the drill stem sections and to provide power for connecting drill stem sections in carrying out a drilling operation.

Other objects and features of the invention will be appreciated and become apparent as the present disclosure proceeds and upon consideration of the accompanying drawings and the following detailed description wherein an embodiment of the invention is disclosed.

In the drawings:

Fig. 1 is a side elevational view partly in section and taken on the line 11 of Fig. 2.

Fig. 2 is an elevational view of the rear end of the drilling rig with portions shown in section and other parts omitted for clarification.

Fig. 3 is a fragmentary sectional view taken on the line 33 of Fig. 2.

Fig. 4 is a fragmentary perspective view of a portion of the apparatus.

Fig. 5 is a fragmentary perspective view illustrating parts of the reversed drive mechanism.

Fig. 6 is a fragmentary plan view showing the drill stem clamping mechanism.

Fig. 7 is a diagrammatic view illustrating the hydraulic system for controlling operation of the drilling rig.

Fig. 8 is a diagrammatic view showing the multiple way valve in a position to raise the kelly bar.

Fig. 9 is a similar view of the valve in a neutral position.

Fig. 10 is a fragmentary view partly in section and taken on the line 1010 of Fig. 2.

Fig. 11 is a sectional view taken approximately on the line 1111 of Fig. l.

- A drilling rig exhibiting the invention includes a frame which is adapted to be supported for rolling movement by a pair of wheels one of which is shown at 15 in Fig. 1. One wheel is mounted at each side of the frame. The frame includes two tubular longitudinally extending members 16 and 17 which are connected at their rear ends to a larger transversely extending tubular member 18 which is also adapted to serve as a reservoir for liquidof a hydraulic system. The rear ends of the frame members 16 and 17 may be welded to the periphery of ice of the frame so that the drilling rig may be connected to a tractor or other types of automotive vehicle for transportation.

A vertically disposed sleeve 22 is rigidly mounted on the forward portion of the frame. A short section of pipe 23 is arranged for telescoping movement in the" sleeve 22. A relatively large foot 24 which may be'of disc-shape is attached to the lower end of the pipe 23. A plurality of holes 26 are provided in the pipe section and a pin 27 is adapted to extend through diametrically aligned openings in the sleeve 22 and through any one of the holes 26 so that the pipe section may be moved downwardly into engagement with the terrain and serve to support the frame. A similar sleeve 28 is carried by one end of the tubular member 18 (Fig. 2)

and a pipe section 29 is arranged for telescoping move ment therein. The sleeve 28 may be welded to the end of the tubular transverse frame member 18 and the end of the reservoir is closed adjacent the sleeve 28. A'

similar sleeve 31 is arranged in a vertically disposed manner at the other end of the tubular member 18. A pipe section 32 is arranged for telescoping movements in the' sleeve 31. The pipe sections 29 and 32 serve as legs at opposite sides of the rear end of the frame and may be adjusted in height to support the frame in a substantially horizontal plane. The pipe sections 29 land 32 are provided with holes for receiving pins 33 in various adjusted positions and a disc 34 is attached to the lower end of each pipe section.

A pair of stub shafts 36 (Fig. 4) are mounted on the tubular frame member 18 adjacent the rear ends of the side frame members 16 and 17. These stub shafts serve as trunnions and are for the purpose of connecting lower ends of two cylinders 37 and 38 to the frame so that they may occupy vertical positions as shown in Figs. 1 and 2 or may be hinged to the phantom line po-- sition shown in Fig. 1. ders 37 and 38 are connected by a plate 39. An arm 41 is secured to the mid-portion of the plate 39 and extends rearwardly therefrom as shown in Fig. 1. inder 42 is pivotally connected at its lower end to the frame by means of a pin 43. A piston (not shown) is" arranged for reciprocating movements in the cylinder 42 and the piston rod 44 therefor is connected at its upper end to the rear end of the arm 41.

When liquid under pressure is introduced into the lower end of the cylinder 42 the cylinders 37 and 38 are caused to swing about the axis of the trunnions 36 and to be moved to an erect position from that shown in phantom lines as shown in Fig. l. The liquid under pressure is retained in the cylinder 42 so that the cylinders 37 and 38 are main? tained in substantially vertical positions at right angles to the plane of the frame.

Any suitable power unit may be mounted on the frame and in the embodiment illustrated an internal combustion engine 46 is mounted on a forward portion of the is thus driven when the power unit is in operation.

A pulley 53 is mounted for free rotation on the shaft 48 and is adapted to be coupled thereto by means of-a' The upper ends of the cylinclutch mechanism 54 which is operated by a bell crank lever 56 and a handle 57. The pulley 53 may be provided with two grooves or the like for receiving two V- belts. A shaft 60 (Fig. l) is arranged parallel to and rearwardly of the shaft 48. A pulley 58 is secured to the end of the shaft 61 which extends through bea iwithin a sleeve 59. A pair of V-belts 61 are about the pulley 53 and the pulley 58. A bevelled g assembly 65 is arranged in a housing 62 as shovm Fig. 11 so that a vertically disposed shaft s3 is in one direction when the clutch 5 is in the Cl position. The gear housing 62 is supported on a b 95 carried by a plate 91 disposed transversely of t. 3 frame.

A gear wheel 64 is secured to the pulley 58 th shaft 68 so as to rotate therewith. Another gear wh 6.6 is in mesh with the gear 64 and the shaft 67 on wh the gear 66 is mounted is journalled for rotation in bean ings within a sleeve as shown in Fi s. 5 and it. This sleeve is supported by a housing 69 which is 2O ranged to rotate about the axis of the shaft 60. A pulley 71 (Fig. 5) is secured to the end of the shaft -67. A belt 72 is trained about the pulley 71 and a pulley 73 se cured on the shaft 48. The sleeve 68 and the housing 69 and the shaft 67 are so mounted and arranged that these parts may swing about the axis of the shaft while the pinion gear 66 remains in mesh with the gear wheel 64. Such swinging movements are accomplished by a handle 74 so as to relax tension on the belt 72 when the clutch 54 mechanism is engaged. When it desired to drive the vertical shaft 63 in a reversed di rection the clutch 54 is disengaged and then do.-*wnw-.:-; l movement of the handle 74 will swing the pulley 71 to a position to tighten the belt 72 whereby the gear wheel 64 is driven in a reversed direction to thereby drive the shaft 63 in a direction opposite to that which it is driven by the belt 61.

The upper end of the vertical shaft 63 is journalled for rotation in a bearing 76 carried by the arm 41. A sprocket wheel 77 is secured to the shaft 63 near the up per end thereof. A larger sprocket 78 is carried by a sleeve 79 (Fig. 3) which is mounted for rotation with respect to the plate 39 by means of a bearing assembly 81. A socket member 82 having a square opening therein is bolted to the sprocket wheel 78. A sprocket chain 83 is trained about

sprocket wheels

77 and 78 so as to drive the socket member 82. A hollow kelly bar having a square exterior perimeter extends through the socket member 82 and is free to move upwardly and downwardly therethrough. A drill stem 86 is adapted to be threadably connected to the lower end of the kelly bar.

A thrust bearing assembly 87 is provided at the upper end of the kelly bar 84 and this bearing assembly is attached to a cross header 88. The outer ends of the cross header 88 are connected to piston rods 11 and 92 which extend into the respective cylinders 37 and 38. When liquid under pressure is supplied into the upper ends of the cylinders 37 and 38 the pistons (one of which is shown at 93) are moved downwardly in the respective cylinders to apply force to the upper end of the kelly bar in carrying out a drilling operation.

The lower ends of the cylinders 37 and 38 are rigid-- 1y attached to the transversely disposed plate 91 which is hingedly connected to the frame by means of the trun nions 36. Such an assembly makes it possible for the drilling rig including the cylinders 37 and 38 to swing to the lowered position indicated in phantom lines in Fig. l. The plate 91 is provided with a depending flange 93. An aperture 94 (Fig. 6) is provided in the midportion of the plate 91 through the drill stern sections such as the one shown at 86 are adapted to extend. A clamp assembly is provided for gripping any one of the drill stems when it is desired to add sections thereto or during the removal of the drill stem from the bored hole. The clamp includes a pair of

flanges

96 and 97 which accommodate

end portions

98 and 99 of a rotary jaw when it is in the position shown in Fig. 6. A clamp actuating handle 101 has a threaded stern which extends through a boss 102 carried by the depending flange 93 of the plate structure. The threaded stem 183 is adapted to engage a slidable clamp element 104 whereby the periphery of the drill stem may be gripped between the element 104 and the other member of the clamp. The clamp parts may be removed from the plate 91 by retracting the handle 101 until the clamp element 1114 is removed from the slot in the member 106 of the clamp. Thereafter the member 106 may be rotated so that the ends 98 and 89 may be rotated from under the

flanges

96 and 97. The aperture and the plate are sutficiently large to avoid interference of the plate with the drill stem during rotation but serve to guide the stem during a drilling operation.

A pulley 111 (Fig. 4) is fixed to the transverse shaft 1-3 and drives a pump 112 by means of a belt 114 trained about the pulley 111 and a pulley 116 on the pump shaft. The suction side of the pump 112 (Fig. 7) is connected by a conduit 116 to the reservoir 18 which forms a part of the rear end of the frame. Conduit means 117 extends from the outlet side of the pump 112 through a manually operable valve 118 to the lower end of the hydraulic cylinder 42. The upper end of the cylinder 42 is connected by a suitable pipe or hose 1w to the reservoir 18. A conduit 120 extends from the conduit means 117 to the line 119 and a manually operable valve 121 is provided on the conduit 120.

A valve for controlling movement of the liquid from the pump 112 to the hydraulic cylinders 37 and 38 is shown diagrammatically in Fig. 7 and represented in general by the numeral 125. This valve is controlled by a lever 124. When the lever is in the position shown in Fig. 7 the liquid from the discharge side of the pump 112 passes through the conduit line 122 through the valve and into the conduit line 123 so as to be applied to the upper ends of the cylinders 37 and 38 to move the pistons downwardly therein. After the cross head 88 is in the lowermost position the handle 124 is moved to shift the pistons 126 to positions obstructing the openings in the valve 125 so that the pistons in the cylinders 37 and 38 are locked in their lowermost positions. Then the valve 121 is closed and the valve 118 may be opened to admit liquid under pressure to the lower end of the hydraulic cylinder 42 to shift the drilling rig to a vertical position. During this movement liquid in the cylinder 42 above the piston therein escapes through the conduit line 119 into the reservoir 18.

When it is desired to lower the drilling rig to the phantom line position shown in Fig. 1 the valve 118 is closed and the valve 121 opened. Manual force is applied against the cylinders 37 and 38 until the rig is moved from its vertical position. The action of the gravity will then cause the tower to swing downwardly towards the phantom line position of Fig. 1 and the hinging may be controlled by adjusting the position of the valve 121. As the piston in the cylinder 42 moves downwardly suction is created in this cylinder above the piston which draws oil from the reservoir 18 through the conduit line 119 to thereby keep the oil in the reservoir in balance and eliminating the need for an unduly large storage tank for the hydraulic system. The capacity of the reservoir 18 may be increased by means of one or more upstanding auxiliary reservoir 128.

The valve 125 is of a multiple way type and in association with the other parts of the assembly provides desirable operating characteristics. The valve 125 governs vertical movements of the kelly bar 84 by regulating the flow of hydraulic liquids to and from the cylinders 37 and 38. The flow of liquid is accomplished by varying the position of the handle 124 of the valve and by the use of a curved graduated metering plate 131 which is mounted in association with a rod 132 and nuts 133 and 134 thereon.

After the drilling rig has been erected to the vertical position downward movement of the handle 124 causes the pistons 126 to be moved to the position shown in Fig. 7 when the nut 133 is engaged under the arcuate plate 131. By moving the rod 132 and the nut 133 inwardly along the curved surface of the plate 131 a graduated downward movement of the handle 124 is obtained which governs the downward moving speed of the pistons within the cylinders 37 and 38 and accordingly the downward movement of the kelly bar. The more the handle 124 is moved downwardly the greater the downward speed of the pistons in the cylinders 37 and 38. The valve 125 is so constructed that the upper piston 126 opens the passage into the conduit 123 slightly ahead of the lower piston 126. The liquid under pressure then travels from the pump 122 through the conduit line 122 and through the conduit line 123 and enters the upper ends of the cylinders 37 and 38 and forces the pistons downwardly. The liquid under the pistons in the cylinders 37 and 38 tends to leave through the conduit line 136 and passes into the valve 125 where it is restricted by the smaller size passage between the lower piston 126 and the opening to the line 136 thereby causing a back pressure to build up on the bottom sides of the pistons in the cylinders 37 and 38. The back pressure is further increased as the

piston shafts

91 and 92 replace oil in the upper ends of the cylinders 37 and 38 thus causing a larger volume of oil to leave the lower ends of the cylinders 37 and 38 than the volume which is entering at the upper ends of the cylinders.

The pistons in the cylinders 37 and 38 are thus controlled by two opposite forces one resulting from the pressure under which the incoming liquid is supplied and the back pressure created by the restricted release of the outgoing liquid. The restriction of the return passage provides that a controlled volume of liquid flows through the conduit line 137 to the reservoir 18. The volume of liquid flowing through the return passage of the valve 125 controls the vertical speed of the pistons 93 which in turn controls the vertical speed of the drill bit through mechanical connections of the cross header 88 to the kelly bar and the drill stem. The volume of the incoming liquid moves the pistons 93 downward rapidly until the back pressure described is built up under the pistons. The piston 93 will then travel downwardly at a rate proportionate to the volume of the outgoing liquid. If the downward travel of the drill bit is slowed as a result of hard formation the outgoing liquid will not be forced from the cylinders 37 and 38 as before causing the pressure on the lower sides of the pistons 93 to drop. The pressure difference between the liquid above and below the pistons 93 then results in a downward force being applied to

piston rods

91 and 92 thus forcing the drill downwardly into the hard formation. The slower the bit travels downwardly the greater the pressure difference between the top and bottom sides of the pistons 93. If the drill bit tends to fully arrested position during a drilling operation the pressure on the bottom of the pistons 93 will approach zero causing substantially all of the incoming liquid supplied under pressure to be applied to the top of the pistons 93 to thereby force the drill bit through the hard formation.

After the drill bit passes through the hard formation it tends to travel downwardly faster. As a result of the increased rate of downward movement the pistons 93 also tend to travel downwardly faster. The pistons are then required to force the liquid from the lower ends of the cylinders 37 and 38 through the restricted outlet passage in the valve 125 to thereby again produce back pressure in the outgoing liquid. This back pressure serves to slow down the downward travel of the pistons 93 which in turn will slow down the travel of the drill stem and the drill bit. Thus the downward travel of the 6 drill stem will also tend to remain at a substantially constant speed.

The valve provides for the control of upward movement of the kelly bar and the drill stem. Such operation is initiated by raising the handle 124 to the position shown in Fig. 8 so that the nut 134 is engaged" on top of the metering plate 131. Since there is no need for adjustment of the upward travel of the kelly bar and the drill stem the nut 134 is positioned to give a maximum speed of travel when arranged over the metering plate 134. The liquid will then flow from pump 112 into the line 122 and through the conduit line 136 into the lower ends of the cylinders 37 and 38. The pistons 93 are thus moved upwardly lifting the cross header 88 and lifting the kelly bar. The handle 124 is returned to a neutral position (Fig. 9) when the pistons 93 arrive at the upper ends of the cylinders 37 and 38.

The valve 125 provides the further function of stopping upward or downward movement of the kelly bar,

when the handle 124 is in the neutral position shown in Fig. 9. This position of the handle 124 may be obtained by releasing the rod 132 and the nuts 133 and 134 from association with the arcuate plate 131. The valve 125 to a desirable location for drilling when the forward end I of the frame is disconnected from the towing vehicle. The stabilizing legs as represented by the

pipe sections

23, 29 and 32 are then lowered to engage the surrounding terrain. The prime mover or engine 46 is then started and the pump 112 is set in operation. The valve 118 is then opened while the handle 124 remains in the lowermost position such as shown in Fig. 7. Liquid under pressure enters the cylinder 42 and the piston rod 44 is extended to swing the tower assembly from the phantom line position of Fig. 1 to the full line position. The valve 118 is then closed and the handle 124 and the valve 125 is returned to a neutral position. The closure of the valve 118 retains liquid Within the cylinder 42 below the piston therein so that the tower is maintained in an erect position.

Thereafter the handle 124 is raised to operate the valve 125 to a position as shown in Fig. 8. Liquid discharged by the pump 112 then enters the lower ends of the cylinders 37 and 38 through the conduit line 136 to raise the cross header 88 and the Kelly bar to its uppermost position. The handle 124 is then returned to a neutral position.

A joint or drill stem such as shown at 86 is thenv threaded onto the lower end of the Kelly bar 84. The valve handle 124 is then pushed down until the drill stem 86 engages the ground or terrain. This lifts the rear portion of the drilling rig and the wheels 15 are raised otf the ground. The stabilizing legs as represented by the pipes 29 and 32 are then dropped so that the foot members 34 are in engagement with the ground and the pins 33 are introduced through holes in the sleeves 28 and 31 and through the holes in the pipe sections 29 and 32.

The frame may thus be supported on the legs in a sub-' stantially horizontal plane. The valve handle 124 is then lifted which causes the drill stem and Kelly bar to be moved upwardly transferring weight of the drilling rig onto the stabilizing legs.

A drilling bit is then threaded onto the end of the drill 1; 1/ to move downwardly. Water under pressure may be supplied onto the upper end of the Kelly bar 34 for passage downwardly therethrough and through the drill stem for flushing chips from the bottom of the drill hole. The drill bit continues to be urged downwardly by the liquid under pressure supplied into the upper ends of the cylinders 37 and 38 and such operation is continued until an end of the drill stem 36 is just above the clamp assembly carried by the plate 91.

The valve handle 124 is then returned to a neutral position. The clutch actuating lever 57 is then moved to disengage the clutch 54 so that rotation of the drill bit ceases. The clamp assembly shown in Fig. 8 is then utilized by turning the handle 191 to grip the periphery of the drill stem. The lever 74 is then actuated while the clutch 54 remains disengaged to tighten the belt 72 to cause the gear wheel 53 to be driven in a reverse direction and to drive the Kelly bar in a direction to unthread it from the upper end of the drill stem. Thereafter the lever 74 is returned to a position to release tension on the belt 72 and thereby interrupt reversed rotation of the Kelly bar. The valve handle 124 is then lifted so as to raise the Kelly bar to its uppermost position. Another section of the drill stem is then threaded into the Kelly bar. The valve handle 124 is then moved downwardly so as to move the Kelly bar downwardly until the newly added drill stem is in contact with the stern held by the clamp. The by-pass valve 143 is opened just before the newly added stem portion contacts the first drill stem. The valve handle .124 remains in the lower position until the clutch actuating lever 57 is moved to a position to engage the clutch 54. The Kelly bar is thus rotated threading the drill stems to each other. The clamp is then loosened by retracting the handle 101 and the drilling continues. The drill stem may be removed from the bore hole by lifting the drill stem with one section of the stem at a time.

A pressure gauge 141 is provided in a conduit line 142 extending from the conduit line 123 to the reservoir 18 as shown in Fig. 7. A manually operable by-pass valve 143 is provided in the conduit line 142. This valve is for the purpose of reducing the force applied downwardly on the Kelly bar. The valve 143 may be opened and liquid under pressure will circulate from the pump 112 through the conduit line 122 into the conduit line 123 when the valve handle 124 is in the lowered position. The liquid will then return to the reservoir 18 through the conduit line 142. A gradual closing of the manually operable valve 143 causes a gradual choking off of the free flow of the liquid and only a portion of the energy developed by the pump 1312 will be applied to the upper ends of the cylinders 37 and 38. Such an arrangement eliminates the possibility of stripping the threads of the drill stem while connecting and disconnecting the drill stern sections. it will be observed that the valve 143 is in such a position in the hydraulic system that it serves as a bypass only for the liquid being delivered to the upper ends of the cylinders 37 and 38.

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

1. In drilling apparatus, a frame including a transverse member, legs depending from said frame, means for adjusting the vertical positions of the legs with reference to the frame for Supporting the frame in a substantially horizontal plane, two cylinders spaced transversely of said frame, means pivotally connecting lower ends of said cylinders to said transverse member, power operated means for swinging said cylinders on said pivotal connections to vertical positions with reference to the plane of the frame, pistons movable in said cylinders with piston rods extending from upper ends thereof, a cross header connecting upper ends of said piston rods, a kelly bar depending from said cross header, a thrust bearing carried by said cross header supporting an upper end of the kelly bar for rotation, a plate connecting upper ends of said cylinders, a socket member mounted for rotation on said plate and having an opening therethrough through which the kelly bar extends and may move while maintaining a driving relationship between the socket member and the kelly bar, and means for driving said socket member.

2. In drilling apparatus, a frame including a transverse member, legs depending from said frame, means for adjusting the vertical positions of the legs with reference to the frame for supporting the frame in a substantially horizontal plane, two cylinders spaced transversely of said frame, means pivotally connecting lower ends of said cylinders to said transverse member, power operated means for swinging said cylinders on said pivotal connections to vertical positions with reference to the plane of the frame, pistons movable in said cylinders with piston rods extending from upper ends thereof, a cross header connecting upper ends of said piston rods, a kelly bar depending from said cross header, a thrust bearing carried by said cross header supporting an upper end of the kelly bar for rotation, a plate connecting upper ends of said cylinders, a socket member mounted for rotation on said plate and having an opening therethrough through which the kelly bar extends and may move while maintaining a driving relationship between the socket member and the kelly bar, means for driving said socket member, and a clamp assembly carried by said transverse member having an opening therethrough through which the kelly bar extends.

3. In drilling apparatus, a frame including a transverse member, legs depending from said frame, means for adjusting the vertical positions of the legs with reference to the frame for supporting the frame in a substantially horizontal plane, two cylinders spaced transversely of said frame, means pivotally connecting lower ends of said cylinders to said transverse member, power operated means for swinging said cylinders on said pivotal connections to vertical positions with reference to the plane of the frame, pistons movable in said cylinders with piston rods extending from upper ends thereof, a cross header connecting upper ends of said piston rods, a kelly bar depending from said cross header, a thrust bearing carried by said cross header supporting an upper end of the kelly bar for rotation, a plate connecting upper ends of said cylinders, a socket member mounted for rotation on said plate and having an opening thercthrough through which the kelly bar extends and may move while maintaining a driving relationship between the socket member and the kelly bar, a sprocket wheel carried by said socket member, a shaft disposed parallel to said kelly bar, a sprocket wheel carried by said shaft, a chain trained about said sprocket wheels, and power actuated means for driving said shaft.

References Cited in the file of this patent UNITED STATES PATENTS 2,200,075 Caldwell May 7, 1940 2,309,999 Vanderzee Feb. 2, 1943 2,516,182 Bury July 25, 1950 2,665,116 Brink et a1 Jan. 5, 1954 2,754,085 Sewell et al. luly 10, 1956 woman K r.