US1962228A

US1962228A - Pipe pusher

Info

Publication number: US1962228A
Application number: US583156A
Authority: US
Inventors: Abramson John Herbert; Edwin C Swanson
Original assignee: Greenlee Brothers and Co
Current assignee: Greenlee Brothers and Co
Priority date: 1931-12-25
Filing date: 1931-12-25
Publication date: 1934-06-12
Anticipated expiration: 1951-06-12

Description

June 12, 1934. ABRAMSQN 5- AL 1,962,228

PIPE PUSHER Filed Dec. 25, 1951 4 Sheets-Sheet l June 12, 1934- J. H. ABRAMSON El AL PIPE PUSHER 2 t MW 7 & F? W e m Z S 4 X m Maw N w y D m J m June 12, 1934. J. H. ABRAMSON ET AL PIPE PUSHER Filed Dec. 25. 1931 4 Sheets-Sheet 5 June 12, 1934.

J. H. ABRAMSON El AL 1,962,228

PIPE PUSHER Filed Dec. 25, 1931 4 Sheets-Sheet 4 l 1 if N NE? "In M \iw'w llitl: I. 1

Patented June 12, 1934 UNiTED STATES PATENT OFFICE PIPE PUSl-IEB Application December 25, 1931, Serial No. 583,156 19 Claims. (Cl. 254-29) This invention relates to fluid operated devices and has particular reference to means for pushing pipe and the Lke through the ground and to injection mechanism associated therewith. 6 It has been customary, until very recent times, to lay conduit pipe for water, gas, wires, and the like, by digging a trench and depositing the pipe directly therein. This, however, has been very expensive and, in many instances, involves the 10 interruption of vehicular trafllc. As aresult, so-

called. pipe pushers have come into use which serve to push the pipe through the ground, the use of which involves merely the digging of a single pit of sufficient size to receive the pusher and a single length of pipe.

Through this means the excessive labor involved in digging a continuous trench is, in a large part, eliminated, as well as the inconven-l ience often resulting from the making of such trenches across highways, railroads, and the like.

1 However, the pipe pushers now in use are not entirely satisfactory and are open to a number of serious objections. In a general way, these pushers have consisted of clamping means adapted to be applied to the pipe having a ratchet connection with a flrmly anchored base and provided with levers for advancing the clamping member along the base. With these constructions it is necessary to advance the clamping member one step of the ratchet at each swing of the lever. Furthermore, it is necessary to move the lever sufliciently to carry the clamping member cons derably beyond the position of engagement in order to have the pawl move into the next step on the rack of the ratchet. This means a considerable loss in motion at each movement of the lever. vAnother objection to these devices is the fact that the levers must be of excessive length in order to provide sufllcient power to operate the device whereby a number of men are required to swing the levers. Even under these circumstances it-is often impossible to develop sufficient power when the ground is such that the pushing is difll- Clllt.

Another objection to these devices lies in the fact that no means are provided for varying the rate at which the pipe may be pushed. In other words, regardless of the condition oi! the ground and the ease with which the p'pe passes through it, the pipe must be pushed at substantially the same rate.

A further objection to these pushers is the fact that pressure is not applied evenly on both sides of the pipe as a result of which considerable power is lost because it is not applied directly or a pipe pusher having an improved base.

parallel to the longitudinal center-line of the pipe.

These devices have been customarily provided with a base having spaced racks on their upper sides near the side edges. Because of this construction the racks rest adjacent to opposite sides of the pit and are in positions such that materials falling down the side of the pit tend to fall upon the rack and interfere with uniform operation of the rack and pawl mechanism.

We have aimed to provide a pipe pusher wherein the pipe is moved by means of one or more pistons which are projected from fluid cylinders.

Anotherobject of the invention is the provision A still further object of the invention is the provision of a pipe pusher having a base arranged to support a carriage having one or more fluid pistons shaped and positioned to exert a pushing stroke against the pipe and means for moving the carriage along the base at the close 01 each stroke.

Another object of the invention is the provision 01' a pipe pusher having a plurality of operating speeds. so

We have also aimed to provide a hydraulic unit having improved injection means. i g

Other objects and attendant advantages will become apparent to those skilled in the art from the following description and the accompanying 35 drawings in which- Figure 1 is a side elevation of the pipe pusher shown in operative position;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a section on the line 3-3 of Fig. 1;

Fig. 4 is a vertical section through one of the cylinders showing the pistons at the end of their stroke; 1

Fig. 5 is a section substantially similar to Fig. 4, showing the position of the parts when the carriage has been repositioned for a succeeding stroke;

Fig. 6 is a horizontal section through the ca riage;

Fig. 7 is a front view of the carriage showing the base and pipein section; i

Fig. 8 is a front view of a modified form of pipe attachment;

Fig. 9 is a side elevation of the part shown in i 8;

Fig. 10 is a fragmentary section through .the rear of the carriage showing one of the injectors in section; and

Fig. 11 is a section on the line 11-11 of Fig. 10.

Attention is first directed to Figure 1, wherein 1m a typical pipe pushing installation is portrayed. The unit is herein shown positioned in a pit formed in the ground 16 adjacent to a concrete pavement 1'7 under which a pipe is to be pushed. A base designated generally by 18 is supported on wooden timbers l9 and 21 on the floor of the pit. The rear end of the frame 18 bears against a backing timber 22 through an intermediate backing plate 23. A carriage 24 is positioned on the frame 18 and is adapted to be moved toward the right facing Fig. 1, through a succession of pushing positions. The carriage 24 is provided with a pair of spaced

pistons

25 and 26 best shown in Fig. 6, receivable in a yoke 27 which is also provided with a large opening to receive the pipe 28 to be pushed. A pipe attachment 29 is firmly secured to the pipe 28. A ring 30 may be provided in the top of the carriage to facilitate the lowering of the carriage into the pit and for removing it therefrom. A pair of

injectors

31 and 32, operated by

handles

33 and 34 serve to inject fluid to project the

pistons

25 and 26 which force the yoke 27 against the pipe attachment 29 pushing the pipe forward through the ground.

Springs

35 and 36 are tensioned by the projection of the pistons and serve to draw the carriage into its successive pushing positions at the close of each pushing stroke of the pistons.

Referring now to Figs. 1 and '7, the base 18 consists of a rail having the shape of the conven tional railroad rail provided with flat upper and lower portions 37 and 38, respectively, and a connecting web 39. The upper surface of the rail is provided with transverse slots 41 at regular intervals. The backing plate 23 is positioned on the end of the rail and is provided with a grooved portion 43 for receiving the lower portion 38 of the rail, to support the backing plate thereon. The backing plate is provided with a bearing portion 44 of greater thickness than the remainder of the plate, the portion 44 being positioned at a point such that its longitudinal center-line coincides substantially with the upper surface of the rail. Because of this construction the force exerted on the rail by the pipe pushing operation tends to force the front end of the base downward instead of upward as is commonly the case with pipe pushers.

The carriage 24 may advantageously consist of a main casting 45 provided on its lower side with downwardly projecting fingers 46, 4'7, 48, and 49, shaped to enclose the upper portion 37 of the rail and a substantial part of the web 39 of the rail as shown in Fig. 7. The casing is also provided with a chamber 51 constituting a fluid reservoir, with spaced

cylinder chambers

52 and 53 and with a longitudinal opening 54 between the

cylinder chambers

52 and 53 to receive the pipe 28. By-pass openings connect the

cylinder chambers

52 and 53 to the reservoir and serve to bypass the fluid pumped into the chambers, when the pistons are fully projected thereby preventing the latter from being forced completely out of the cylinders. A pawl 55 is secured to the rear of the main casting 45 on a pin 56 extending between spaced ears 57 and 58 in a position to slide along the top of the rail and engage in the slots 41 to prevent backward movement of the carriage. A pin 59 serves to permit convenient manual lifting of the pawl.

The

pistons

25 and 26 are positioned in the

cyfinder chambers

52 and 53 for longitudinal movement and are provided at their inner ends with cup packings designated generally by 61 secured in place by means of cap screws 62. A

casing head 63 is positioned across the forward end of the casting 45, closing the chamber 51, and is provided with openings through which the

pistons

25 and 26 pass.

Packing glands

64 and 65 prevent the escape of fluid from the

chambers

52 and 53 along the cylinder walls. The forward ends of the pistons are provided with portions 66 of reduced diameter to provide shoulders 67 and to receive the yoke 27. The yoke 2'7 is provided with a cylindrical opening 68 through which the pipe 28 passes and with openings 69 and '71 on opposite sides of the opening 68 to loosely receive the portion 66 of the

pistons

25 and 26, the latter openings being sufiiciently large to permit a certain amount of anguar movement between the pistons and the yoke. The ends of the yoke 27 are slotted as shown at '72 and '73 and are provided with pins 74 and '75 extending across the slots, one end of the spring 36 being secured to the pin 74 and one end of the spring 35 to the pin '75. The

springs

35 and 36 extend along the sides of the carriage substantially parallel to the

pistons

25 and 26, their rear ends being secured to

pins

76 and 77 which are supported on the casting 45 through

cars

78 and 79 formed integrally therewith. Thus, as the

pistons

25 and 26 are projected outward the tension on the springs 35 and 36' is increased. The lower side of the yoke 27 is provided with a pawl 81 positioned to move along the upper side of the rail as the yoke moves with respect thereto and shaped to drop into the grooves 41 to prevent movement of the yoke backward along the rail. A pin 82 projects from the side of the pawl 81 in a position to be engaged by a cam 83 on the bottom of the carriage, and when the carriage is repositioned, the cam 83 and pin 82 serve to lift the pawl 81 out of the groove as will presently be more fully described.

In order to transmit the movement of the pistons to the pipe 28 a clamp may be attached to the pipe. One such means is shown in Fig. 7 of the drawings and consists of opposed clamping

members

84 and 85 having opposed arcuate faces 86 and 87 adapted to be brought into contact with opposite sides of the pipe and be firmly secured thereto by means of

bolts

88 and 89 passing through the clamping members. Obviously other types of clamps may be used to provide flangelike means on the pipe against which the yoke 27 may bear.

In Figs. 8 and. 9, we have shown a type of pipe attachment for use when it is desired to push against the end of the pipe. This consists of a plate 91 having a forwardly projecting cradle portion 92 and a rearwardly projecting trunnion 93 receivable in the opening 68 of the yoke. An adjustable bracket member 94 is secured to the forward side of the plate 91 and is provided with a lower face 95 to bear against the pipe and hold the same in position. A slot 96 and supplementary bolt holes 97 and 98 permit vertical adjustments of the bracket member 94.

Oil or similar fluid is held in the reservoir 51 and is transferred therefrom to the

cylinder chambers

52 and 53 by means of the

injectors

31 and 32, for the purpose of projecting the pistons. The

injectors

31 and 32 are identical in design differing only in capacity and are positioned in sockets 99 and 101 in the casting 45 at the rear end of the

pistons

25 and 26 respectively, the 3 socket 99 opening directly into the cylinder chamber 52 and the socket 101 into the cylinder chamber 53. The lower ends of the sockets are connected together by means of

channels

102 and 103 so as to equalize the pressure in the two cyl- I 1,962,228 inder chambers and to permit both of the pistons downward iromthe lower end thereof. The pro to be projected through the operation 01' a single injector. A plug 103a serves to close the opening caused by drilling the

channels

102 and 103.

Channels

104 and 105 connect the reservoir 51 with the sockets 99 and 101 respectively and serve to conduct oil or other fluid from the chamber to the injectors. The injectors are reciprocated by means or the

handles

33 and 34 which may advantageously consist of pipes slipped over the ends of

actuating levers

106 and 107 respectively. The levers may advantageously be provided with

bends

108 and 109 intermediate their ends for the purpose of presenting the handles in a convenient position for operation. The plungers 110 and.111 of the

injectors

31 and 32 respectively, are pivotally connecteo to the

levers

106 and 107 at points near the bends. The

levers

106 and 107 are supported upon the casting 45 through

links

112 and 113, respectively, one end of each of the links being pivotally supported on the casting as shown at 113a and the other end being pivotally connected to the levers. The

levers

106 and 107 are each provided with a plurality of spaced openings as shown in 'Fig. 10 at 114 and 115 for the purpose of receiving the pins 116 which connect the links 112 and 113v to the levers, the diii'erent positions of the links providing difierent leverages and different lengths of stroke for the injectors.

Referring now more particularly to Fig. 10, each of the injectors consists of a valve member designated generally by 117, an injector cylinder designated by the numeral 118 and a plunger 119. The valve member is provided with a peripheral flange 121 arranged to closely fit the socket 99 or 101 and to provide a peripheral space 122 between the socket and the valve member for the circulation of oil or other fluid thereabout. Intermediate its ends the valve member is provided with a shoulder 123 arranged to bear against a shoulder 124 of the injector socket, a layer of packing 125 being interposed therebetween. The valve member is recessed below the shoulder 123 as show at 126' to provide a lower end 127 of smaller diameter than the remain er of the valve member. The valve member is rovided with a central cylindrical bore 128 having a flare as shown at 129 intermediate its ends to provides. seat for a valve ball 131. A collar 132 holds the ball against its seat and is-resiliently supported by aspring 133 supported upon a plug 134 threaded into the lower end of the bore 128.

the central bore 128.

Ball valves

142 and 143 are positioned in the

bores

137 and 138 respectively, and seat against the bottom thereof to close the

channels

139 and 141. The

ball valves

142 and 143 are slightly smaller than the bores, in which they rest, there being sufficient difference in size to permit the lateral displacement of the balls to open the

channels

139 and 141 as will presently be described. 7

The plunger 119 is provided at its lower end with a cylindrical projection 144 axially positioned thereon, and the projection 144 is provided with an axially positioned pin 145 projecting jeetion 144 is slightly smaller'in. diameterv than thecentral bore 128 and is arranged to move into the bore when the plunger 119 is moved downward vbeyond its normalstroke as will be presently described. This projection is of sufficient length and diameter. however, to come into contact'with the

ball valves

142 and 143, when 4. the projection 144 moves downward in the central bore, thereby displacing the ball valves and opening the

channels

139 and 141. The pin 145 is of such length as to come into contact with the ball valve 131 at substantially the same point in the movement of the plunger as that at which the projection 144 comes into contact with the

ball valves

142 and 143. As a result oi this con- 7 struction the

ball valves

131, 142, and 143, are simultaneously opened upon suitable movement of the plunger 119 to permit liquid to flow from the recess 126 into the space 122. The recess 126 is connected directly to one of the

cylinder chambers

52 or 53 through openings 146 or 147 as the case may be and to the opposite cylinder chamber through the

channels

102 and 103. The space 122 is connected to the reservoir through

channels

104 or 105. I

The injector cylinder 118 is provided with a cylinder chamber 148 closely receiving the plunger 119 for reciprocation. The upper end of the cylinder is provided with a packing 149 and a nut 151 threaded thereon to prevent the escape of liquid along the interface between the plunger and the cylinder. The lower end of the cylinder is threaded as shown at 152 for reception in complemental threads on the sockets 99 and 101, the cylinder being turned into the socket firmly against the valve member 117. The lower end of the cylinder is provided with an inwardly extending flange 153 providing an endwise opening 154 out of the cylinder chamber which is of substantially smaller cross-section than the cylinder chamber itself, thisopening being slightly larger than the cylindrical projection 144 on the plunger. The purpose of this flange is to limit the normal downward movement of the plunger 119 but to permit further slow movement in order to open the ball valves and release the fluid from the cylinder chambers of the machine. Thus the downward stroke of the plunger will progress at a normal rate until the projection 144 on the plunger passes into the opening 154. At this point the remaining fluid in the cylinder chamber is partially trapped but may slowly escape through the opening 154 around the projection 144 when more than normal pressure is applied to the handle. As this fluid escapes the plunger will move slowly downward until the projection 144 and the pin 145 displace the ball valves whereupon fiuid will be permitted to pass from the

cylinder chambers

52 and 53 back into the reservoir 51.

Means are provided for venting the air into and out oi. the reservoir 51 comprising a plug 155 threaded into the top of the reservoir as shown at 156. Openings 157 and 158 are enlarged as shown at 159 and 161-to form seats for ball valves 162; and 163'which are resiliently held in positions to close the openings by means of

springs

164 and 165 held in place by means of

tubular caps

166 and 167 threaded into the enlarged ends of the opening. It will be seen that as liquid is pumped out of the reservoir 51 the air pressure therein wi l be decreased and air will enterthrough the opening 157 by displacing the ball 162 against the pressure of the spring 164. On the other hand, when liquid is moved from the cylinder chambers back into the reservoir the air pressure within the reservoir will be increased and will move out through the opening 158 by displacing the ball 163. These vents on the other hand, serve to substantially prevent the escape of liquid from the reservoir regardless of the position the reservoir may occupy.

In operating the pusher the rail 18 is positioned in the pit as shown in Fig. l and the carriage 24 is then lowered at the front of the rail and slipped thereon. By lifting the pawl 55 the carriage may be moved toward the left facing Fig. 1 until the pawl 55 rests in the groove 41 closest to the left end of the rail. The pipe connection or clamp 29 is then placed on the pipe 28 with the pipe passing through the opening 54 in the carriage, or the pipe connection shown in Fig. 9 may be employed. In this position reciprocation of either of the

handles

33 or 34 will cause the

pistons

25 and 26 to be projected forcing the yoke 27 against the pipe connection or clamp 29, thus moving the pipe through the ground. As already set forth, the injectors operated by the

handles

33 and 34 are of different capacities so that different amounts of fluid will be injected into the cylinder chambers of the carriage depending upon which handle is reciprocated. In like manner both handles may be reciprocated to further increase the volume of fluid injected into the cylinder chambers. In all, seven pushing speeds may be had with the injectors as shown in the drawings through operation thereof, singly or together in the combinations possible with the construction shown. If the slowest speed injection is employed, the pistons will be projected at relatively low speed but the maximum pushing power of the unit will be developed. This position may be employed when the device is being used by a single operator or when the pushing is very difiicult. On the other hand, when the ground is such that the pipe moves therethrough' without difficulty, a single operator may operate both of the injectors at their highest capacity, thus materially increasing the pushing speed.

When the pistons have been projected to the end of the stroke further operation of the injectors will merely serve to by-pass fluid back into the reservoir through the by-pass openings 50, thus preventing the pistons from being projected completely out of the cylinders. As the pistons reach the forward end of their stroke the pawl 81 on the yoke 2'7 drops into one of the grooves 41 of the base, thus preparing the mechanism for the.

repositioning of the carriage. At the completion of the piston stroke the operator will depress the handle 34, thus moving the plunger 119 of the injector beyond its normal stroke, displacing the

ball valves

131 and 142 and 143. At this point the

springs

35 and 36, which have been tensioned by the projection of the pistons, draw the carriage along the rail, the pawl 81 preventing backward movement of the yoke 27. This movement of the carriage displaces the fluid in the

cylinder chambers

52 and 53 forcing it back into the reservoir through the injector. As the carriage completes its repositioning movement, the cam 83 on the bottom of the carriage engages the pin 82, lifting the pawl 81 out of the groove 41 of the rail. At about the same time the pawl 55 drops into the groove 41 next succeeding that defining its previous position, after which the mechanism is in a position to continue the pushing operations, and

the pistons will again be projected upon reciprocation of the

handles

33 and 34. The principal function of the cam 83 and the pin 82 is to hold the pawl 81 out of contact with the top. of the rail, when the pistons are in their retracted position, so that the carriage may be manually moved along the rail through manual lifting of the pawl 55 only. In other words, to move the carriage along the rail it is only necessary for the operator to lift the conveniently located pawl 55 by means of the pin 59.

It will be seen that we have provided a construction wherein the pipe may be pushed at a number of operating speeds depending upon the difficulty with which the pipe moves and wherein the maximum pushing power may be developed by a single operator by reducing the pushing speed. Only a single rack is provided on the base and the base is arranged to be positioned in the center of the pit thereby eliminating to a large extent the possibility of dirt falling onto the rack during pushing operations. Furthermore, the pushing steps are comparatively long, thereby elimihating much of the lost motion incidental to the use of the common form of rack and pawl. The base is provided with a backing plate so positioned as to urge the front end of the base down and overcome the common tendency in devices of this sort for the forward end of the base to tip upward. Means are provided for pushing either at the end of the pipe or intermediate its ends. The device is such that sufficient pushing power may be developed with relatively short handles instead of the old style long handles which were required to give suflicient leverage. This permits the device to be used under conditions in which it has heretofore been impossible to use a pipe pusher. The pusher is constructed in two units which may be handled separately thereby minimizing the effort required in handling.

While we have thus described and illustrated a specific embodiment of our invention. we are aware that numerous alterations and changes may be made therein without materially departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. A pipe pusher comprising in combination a fluid cylinder, a base having means thereon for supporting said cylinder in a succession of pushing positions, a piston positioned in said cylinder for exerting a pushing stroke on a pipe to be pushed, means to project said piston, and means for moving said cylinder with respect to said base and said piston to the next pushing position at the completion of a stroke.

2. A pipe pusher comprising, in combination, a fluid cylinder, a base having means thereon for supporting said cylinder in a. succession of pushing positions, a piston positioned in said cylinder for exerting a pushing stroke on a pipe to be pushed upon the application of fluid pressure to the piston, means for relieving the pressure in said cylinder, and means for moving said cylinder with respect to said base and said piston to the next pushing position upon the release of pressure.

3. A pipe pusher comprising in combination a fluid cylinder, 2. base having means thereon for supporting said cylinder in a succession of pushing positions, a piston positioned in said cylinder for exerting a pushing stroke on a pipe to be pushed, manually operable means for selectively injecting fluid into said cylinder at any of a plurality of rates to project said piston at different rates of speed to adapt the speed and power to the strength of the operator and the difficulty of the work, and means for moving said cylinder with respect to the base and the piston to the next 1 pushing position at the completion or a stroke.

, positions, a piston positioned in said cylinder for exerting a pushing stroke on' a pipe to be pushed, a manually operated injector of adjustable stroke for injecting fluid into said cylinder at a rate dependent upon the strength of the operator and the difliculty oi the work, and means for moving said cylinder with respect to said base and said piston to the next pushing position at the completion 01' a stroke.

5. A pipe pusher comprising in combination a fluid cylinder, a base having means thereon for supporting said cylinder in asuccession of pushing positions, a piston positioned in said cylinder for exerting a pushing stroke on a pipe to be pushed, a pair 01' manually reciprocated injectors of different capacities for selectively injecting fluid into said cylinder to project said piston at a rate dependent upon the strength of the operator and the difflculty oi the work, and means for moving said cylinder with respect to the base and the piston to the next pushing position at the completion of a stroke.

6. A pipe pusher comprising in combination a carriage having at least one cylinder and a fluid reservoir, a base having means thereon for supporting said carriage. in a succession of pushing positions, a piston positioned in said cylinder to ,be moved therein by transfer of fluid from the reservoirto the cylinder to exert a pushing stroke on'a pipe to be pushed, and means for simultane-' ously returning said fluid to said reservoir and moving said carriage with respect to the base and the piston to the next pushing position.

7. A pipe pusher as described in claim 6 having valvemeans for venting the air into and out of said reservoir.

8. A pipe pusher, comprising in combination a carriage, a base having means thereon for supporting said carriage in a succession of predetermined pushing positions, means on said carriage for exerting a pushing force on a pipe to be pushed, and means for periodically moving said carriage with respect to the base to the next succeeding pushing position.

9. A pipe pusher comprising in combination a carriage having a pair of fluid cylinders, a rail centrally positioned beneath said carriage to slidably support the same, means between said carriage and said rail to secure the former in a succession of pushing positions, pistons movable in said cylinders in a pushing stroke, means acting between said pistons and said pipe for transmitting motion of the former to the latter, and means for moving said carriage on the base to the next succeeding pushing position' 10. A pipe pusher comprising in combination a carriage having a pair of fluid cylinders, a base including a rail centrally positioned beneath said carriage to slidably support the same, means between said carriage and said rail to secure the forme'. in a succession of pushing positions, fluid operated pistons in said cylinders, means acting between said pistons and said pipe for transmitting motion of the former to the latter, manually operable means on said carriage for injecting fluid into said cylinders to project said pistons in a pushing stroke, and means controlled by said manually operable means for repositioning said pistons by moving said carriage on the base to the next succeeding pushing position. I

be pushed, means for manually operating said pushing member, and means for periodically moving said carriage on the base to the next succeeding pushing position. 4

12. A pipe pusher comprising in combination a base including a rail having a plurality of latch portions defining a succession of pushing positions,

a carriage having at least one fluid cylinder and means for partially enclosingsaid rail to slidably support the carriage thereon, a latch member on said carriage automatically engageable with the latch portions of said rail in response to movement of said carriage to secure said carriage in its pushing positions, a piston in said cylinder for exerting-a pushing force on a pipe to be pushed, manually operable means on said carriage for injecting fluid into said cylinder, and means for moving said carriage on the base to the next succeeding pushing position to reposition said piston.

13. A pipe pusher comprising in combination, a base including a rail having a plurality of latch portions defining a succession of pushing positions, a carriage having at least one fluid cylinder, a fluid driven piston in said cylinder, a latch member on said carriage automatically engageable with the latch portions of said rail in response to movement of said carriage to secure said carriage in its pushing positions, a pipe connector secured to a pipe to be pushed, a yoke on said piston shaped to bear against said pipe connector, latch means on. said yoke for engaging said rail at a latch portion when said piston is projected, and spring means between said yoke and said carriage positioned to be tensioned by the projection of said piston and serving to move said carriage to the next succeeding pushing position upon release of the fluid from said cylinder. L

14. In a pipe pusher a base comprising a rail 0 substantially the shape of a railroad rail, having spaced laterally extending grooves on its upper surface, and a backing plate at one end of said rail having anoflset bearing surface positioned to urge the opposite end of said rail downward when force is applied thereto in operation.

15. A pipe pusher comprising, in combination, a carriage, a base having means thereon for supporting said carriage in a succession of pushing positions, manually operable means on the carriage movable to exert a pushing force on a pipe to be pushed, and means for periodically moving the carriage on the base to the next succeeding pushing position. K

16. A pipe pusher comprising, in combination, a fluid cylinder, a base having means thereon for supporting said cylinder in a succession of pushing positions, a piston positioned in said cylinder for exerting a pushing stroke on a pipe to be pushed, means for preventing return movement of the piston, and spring means acting between the piston and the carriage and the cylinder for drawing the cylinder over the piston to the next succeeding pushing position.

1'7. A pipe pusher comprising, in combination, a carriage member having spaced cylinders and an opening therebetween for the passage of a pipe to be pushed, fluid operated pistons in said cylinders, a base having means to support the carriage in a succession of pushing positions, a yoke supported at opposite ends on the pistons adapted to bear against the pipe intermediate its ends to transmit the motion of the pistons to the pipe, latch means on the yoke for preventing return of the piston, and means acting between the pipe connector, latch means on the yoke for preventing return of the piston, and means acting between the yoke and the cylinder to slidably move the latter on the base when pressure is released from the cylinders to reposition the piston and cylinder.

19. A pipe pusher comprising, in combination, a movable carriage, a fluid piston in said carriage, means acting between the piston and a pipe to be pushed to transmit motion of the piston to the-pipe, and means for alternately causing the piston and the carriage to move forward in step by step movement.

JOHN HERBERT ABRAMSON.

EDWIN C. SWANSON.