US2824542A - Means for handling freshly galvanized pipe during internal swabbing - Google Patents

Description

Feb. 25, 1958 w. s. PEARSON 2,824,542

MEANS FoR HANDLING FRESHLY GALVANIZED PIPE DURING INTERNAL SWABBING Original Filed 001;. 5, 1950 2 Sheets-Sheet 1 W M W I MY/jazzz 5. Penman Feb. 25, 1958 w. s. PEARSON 2,824,542

MEANS FOR HANDLING FRESHLY GALVANIZED PIPE DURING INTERNAL SWABBING Original Filed Oct. 5, 1950 2 Sheets-Sheet 2 WL/ [jam 5. Pearson I United States Patent MEANS FOR HANDLING FRESIILY GALVANIZED PIPE DURING INTERNAL SWABBING William S. Pearson, Baltimore, Md., assignor to Clifton Conduit Company, Inc., Baltimore, Md., a corporation of Maryland Original application October 5, 1950, Serial No. 188,622,

now Patent No. 2,753,837, dated July 10, 1956. Divided and this application March 27, 1956, Serial No. 574,298

12 Claims. (Cl. 11860) The present invention relates to improvements in means for handling freshly galvanized pipe during internal swabbing to remove excess galvanizing metal from the internal walls of the pipe.

An important object of the present invention is to provide improved means for holding an end of a freshly galvanized pipe or conduit section firmly in the mouth of a blow tube while heated swabbing fluid is blown into and through the interior of the pipe to expel excess galvanizing fluid therefrom.

Another object of the invention is to provide improved intermittently operable pinch roll means adapted to operate momentarily in coordination with other freshly galvanized conduit handling mechanism as a supplementary supporting and driving expedient.

A further object of the invention is to provide an improved separable pipe-supporting and motivating pinch roll assembly adapted for use in apparatus for handling freshly galvanized pipe during removal of excess galvanizing material therefrom.

Other objects, features and advantages of the present invention ,will be readily apparent from the following detailed description of a preferred embodiment thereof taken in conjunction with the accompanying drawings in which:

Figure 1 is a more or less schematic elevational view of an apparatus for removing excess galvanizing material from freshly galvanized pipe or conduit, and utilizing the present invention; and

Figure 2 is a more or less schematic view on an enlarged scale taken substantially on the line II-II of Figure 1, showing certain parts in section and others in elevation in the separable conduit-supporting and motivating pinch roll assembly.

An apparatus for removing excess galvanizing material from freshly galvanized pipe or conduit, as shown in Figure 1, comprises a pair of magnetic overhead conveyor rolls 5 supported by a framework 7 adjacent to a zinc tank or pot 8 for the galvanizing bath in which successive conduit sections 9 are freshly galvanized and then delivered to the undersides of the conveyor rolls 5 which thereupon support the same and impel the freshly galvanized conduit longitudinally forwardly through respective aligned openings in the sides of a spatter chamber 10. Means for driving the conveyor rolls 5 comprise a motor 11 mounted on the spatter chamber and suitably drivingly connected with the conveyor rolls through means such as a chain drive 12. As the hot, freshly galvanized conduit sections emerge from the side of the spatter chamber beyond the conveyor rolls 5, the sections pass progressively through a ring swab 13 from which encircling jets of heated swabbing fluid such as super-heated steam are impinged upon the external surface of the pipe to swab excess galvanizing fluid from the outer surface of the conduit and drive the excess galvanizing fluid into the spatter chamber 10.

Immediately after traveling beyond the external swab 13, the pipe section 9 is engaged between a pair of pinch ward toward and successively into engagement with spaced overhead magnetic conveyor rolls 15 which, through the medium of a chain drive 17, are actuated by the motor 11. As will be observed, the path of movement of the conduit section 9 is a diagonally upward direction so as to facilitate the swabbing process.

After the pipe section 9 undergoing swabbing has been moved by the pinch rolls 14 and the conveyor rolls 15 to a position where only the trailing extremity portion of the pipe remains inside the spatter chamber 10, the conduit or pipe section is released from the conveyor rolls 15 by deenergization of the rolls, and the forward end portion of the conduit section is received in the mouth of a gooseneck blow tube 18 from which a charge or blast of internal swabbing fluid such as superheated steam is driven into and through the interior of the pipe 9 to swab and eject excess galvanizing material therefrom into the spatter chamber 10.

One of the functions of the pinch rolls 14 is to maintain endwise forward pressure on the pipe 9 while it is in the mouth of the blow tube 18 and for this purpose the pinch rolls 14 are motivated by suitable chain drive from the motor 11 through the medium of a slip clutch arrangement of suitable character which will maintain the pinch rolls in operation until predetermined resistance to forward movement of the engaged pipe 9 is encountered whereupon the slip clutch operates to permit the rolls to remain in stationary engagement with forward pressure on the pipe.

However, it has been found that if suflicient resistance to slippage is built into the slip clutch for the pinch rolls 14 to maintain adequate forward pressure on the pipe 9 to hold the forward end thereof in the mouth of the blow tube 18 with suflicient firmness to avoid displacement thereof from the blow tube mouth and consequent avoidance of leakage and loss of swabbing fluid force, there is undue likelihood of slippage and damage to the external surface of the freshly galvanized pipe where it is gripped by the pinch rolls 14.

Therefore, there is provided by the present invention additional means for engaging and impelling the freshly galvanized pipe 9, or at least urging the pipe 9 into the mouth of the blow tube 18 with suflicient force, supplemental to the force applied thereto by means of the pinch rolls 14 to assure freedom from reverse displacement of the tube from firm engagement within the blow tube mouth when the force of the internal swabbing fluid is released into the pipe. Herein such additional means comprises an assembly 20 supported by the framework 7 as near as practicable to the head of the blow tube 18 and including a pair of cooperable pinch rolls 21' and 22 disposedto engage the pipe section 9 therebetween after the same has been released from the overhead conveyor rolls 15 and for imparting to the pipe section forward thrust supplemental to the forward thrust of the first mentioned pinch rolls 14 which engage the trailing end portion of the pipe.

In a practical form, the auxiliary thrust imparting mechanism 20 comprises a roll-supporting framework in cluding an upright or standard 23 for supporting the pinch roll 21 and an upright or standard 24 for supporting thepinch roll 22 (Fig. 2). The standards 23 and 24 are secured together by braces 20 and further secure'dby rolls 14 which support and impel the conduit section on means of pivot bolts 23 and 24' respectively to angle. brackets 25 on the respective upper side portions of the frame 7 so as to support the pinch rolls 21 and 22' on respectively opposite sides of the path of movement ofthje pipe section 9 to be swabbed. By preference the standards 23 and 24 are insulated from the framework 7 by means of insulating material 27 interposed between the brackets 25 and the respective standards, the insulatingv material being either for vibration insulation or electrical insulation or both. 7 a

Each of the pinch rolls 21 and 22 is directly carried by a respective elongated shaft 28 to the lower end of which the pinch roll is appropriately secured while the upper end of the shaft is supported by a rocker bearing 29 mounted on a bracket 30 secured to the upper end portion of the respective standards 23 and 24. Through this arrangement, a small rocking movement in the hearing 29 affords relatively large swinging leverage movement of the lower end portion of the respective roll shaft 28.

The position of one of the pinch rolls 21 or 22, in the present instance of the pinch roll 22 is adjustably maintained in transverse relation to the path of movement of the pipe sections 9 by means of an arm or rod 31 having a bearing 32 thereon in engagement with the adjacent shaft 28 for the roll 22 adjacent the lower end portion of the roll shaft. The outer end portion of the rod 31 is attached to the standard 24 for longitudinal adjustment which is fixedly maintained by means such as lock nuts 33. Through this arrangement the pinch roll 22 can be accurately adjusted transversely of the path of movement of the pipe sections 9 by manipulation of the adjustment and retaining rod 31 for accommodating various sizes of pipe. In the adjustment the shaft 28 for the roll 22 rocks about the support provided by the bearing 29.

The whole pinch roll thrust imparting mechanism 20 is also adjustably supported for angular adjustment about the horizontal axis of pivot bolts 23 and 24' by an adjustable turnbuckle 20a connecting threaded rods 20b and 200 that are respectively connected to the upper brace 20' and the standard 7 in the region of the blow tube 18. Tightening of the turnbuckle 20a will cause relative counterclockwise movement of the whole thrust imparting assembly as viewed in Figure 1 while loosening thereof will cause clockwise movement of the assembly also as viewed in Figure 1. By preference the assembly is shown in a vertical or near vertical position as pivoted about the pivot bolts 23 and 24 on the angle brackets 25.

Rotation of the pinch rolls 21 and 22 in unison is effected by means such as meshing large tooth gears 34 carried by the respective shafts 28 adjacent to the upper ends of the shaft close to the supporting rocker bearings 29. Hence, substantial relative adjustment in the spacing between the pinch rolls 21 and 22 can be effected without interfering with the proper meshing of the gears 34 to drive the shafts 28 and thus the pinch rolls in unison in respectively opposite direction.

Means for driving the pinch rolls comprises a motor 35 which is drivingly connected through a gear train 37 with the drive shaft 28 of one of the pinch rolls, herein of the pinch roll 21. Here, again, the gear connection is effected adjacent to the upper end of the shaft assembly so that minimum interference with proper meshing of the transmission gears will occur throughout the range of relative spacing adjustment of the pinch rolls.

The arrangement and construction of the auxiliary pinch roll assembly is such that the pinch rolls 21 and 22 remain separated sufficiently to permit free movement of the pipe section 9 to be swabbed therebetween under the influence of the conveyor rolls until the conveyor rolls 15 are deenergized and release the conduit section. Thereupon, the pinch rolls 21 and 22 are coordinated in operation with the conveyor rolls 15 so that the pinch rolls 21 and 22 enter into engagement with the pipe 9 when the same has dropped slightly from the conveyor rolls 15 to the proper elevation for entering into swabbing registration within the mouth of the blow tube 18. Means for accomplishing this comprise electrically controlled pneumatic apparatus including a pneumatic operator 38 having a cylinder 39 with a piston 40 operative therein reciprocably and provided with a piston rod 41 appropriately connected to a bearing structure 42 on the shaft 28 of the pinch roll 21. Rcciprocations' of the piston 40 are effected by pressure fluid supplied from a suitable source through a supply duct 43 under the control of a valve 44 which is operable for alternately opening and closing appropriate passages leading from the supply duct 43 to opposite ends of the cylinder 39. A spring 47 normally biases the valve 44 in one direction while a solenoid operator 45 is operative when energized to move the valve 40 in the opposite direction in opposition to the bias of the spring 47. Herein the spring 47 normally acts to urge the valve 44 into the reverse position from that shown in Figure 2, namely into the position wherein pressure fluid is delivered to the forward end of the cylinder 39 so as to drive the piston 40 away from the attached shaft 28 whereby the piston rod 41 draws the shaft 23 and thereby the pinch roll 21 toward the left as seen in Figure 2, namely into the dot dash position shown which is the separated condition of the pinch rolls so that a pipe section 9 can be freely run into position therebetween. For reversing the piston, that is for driving the piston into the position shown in Figure 2, the solenoid 45 is actuated by closing of a switch 48 in an electrical circuit 49 for supplying the solenoid with electrical energy from a source of electrical energy from an electrical supply circuit 50 which is also connected to the motor for supplying the motor with electrical energy. It will be understood that the switch 48 while shown merely symbolically in the drawing, may be connected into or operated by any appropriate or desired means in coordination with and automatically as an incident to operation of the machine organization with which the pinch roll assembly 20 is utilized. In my Patent No. 2,606,846 issued August 12, 1952, which was copending with my application Serial No. 188,622, filed October 5, 1950, which is a parent application to the instant application, electrical circuits for synchronizing and integrating operation of the machine as a whole are disclosed in detail and the switch 48 may be readily incorporated into one of those circuits or operating means therefor. In any event, when the switch 48 is closed, the solenoid operator 45 is energized and actuates the control valve 44 to drive the piston into the position wherein the pinch roll 21 approaches the companion pinch roll 22 and thereby engages the pipe section 9 therebetween firmly but in cushioned relation by reason of the pneumatic fluid used for driving the piston. Pneumatic fluid is superior to hydraulic fluid for this use because of its cushioning quality whereby to compensate for any irregularities that may be present in the apparatus or in the engaged pipe section and thus avoid damaging the freshly coated external surface of the pipe section.

In the operation of the valve 44, exhaust from the cylinder 39 is controlled by an auxiliary valve section 51 on the valve 44 and which controls exhaust ducts leading from the opposite ends of the cylinder 39 to an exhaust outlet 52.

Swinging operations or oscillations of the pinch roll 21 as controlled by the pneumatic operator 38 are correlated with operations of the conveyor rolls 15 and of the blow tube 18 in the following fashion. When a freshly galvanized pipe section 19 has been advanced by the pinch rolls' 14 and the conveyor rolls 15 to a position wherein the leading end of the pipe section has just reached the point where it will engage within the mouth of the waiting blow tube 18, that is the position shown in full line in Figure 1, the rolls 15 are deenergized to released the conduit section which by this time, of course, has been ad vanced into a position between the separated pinch rolls 21 and 22. Closely coordinated with release of the conduit section from the overhead conveyor rolls 15 and thereby slight dropping down of the forward end portion thereof, the switch 48 is closed, thereby effecting energization of the solenoid and actuation of the control valve 44 and driving of the piston 40 to cause the shaft 28 to which connected to move laterally and drive the pinch roll 21 into pipe gripping relationship to the companion pinch roll 22. Throughout the operation of the machine, the motor 35 continues in operation to drive the pinch rolls 21 and 22 rotatably in the direction which upon engagement of the pinch rolls 21 and 22 with the pipe section therebetween will cause advancing movement or at least forward thrust of the pipe section.

Since at the moment the leading end of the pipe section 9 engages in thrusting relation within the mouth of the blow tube 18, it is desirable that the pinch rolls 21 and 22, similarly as the pinch rolls 14, cease rotating, or at least not move relative to the engaged pipe section 9, so as to avoid marring the engaged surface of the pipe. Slip clutch means could be used for this purpose similarly as in connection with the pinch rolls 14, but a practical expedient utilized for this purpose comprises having the motor 35 of the three phase type so that in the presence of predetermined resistance to turning of the motor, it

will be held immovable, but yet remain under torque, without overheating. As a result, when the leading end of the pipe section comes to rest within the mouth of the blow tube 18, the pinch rolls 21 and 22 cease rotating but maintain their grip on the pipe section and continue imparting forward thrust to the pipe section which supplements the thrust of the pinch rolls 14 and assures that the leading end of the pipe section remains firmly and undisplaceably in substantially sealing engagement within the blow tube mouth so that full efiiciency of the blast of internal swabbing fluid from the blow tube will result.

Promptly upon completion of the internal swabbing action, the blow tube 18 is retracted into the dash line position shown in Figure 1, by action of a fluid operated cylinder and piston actuator 53. Thereupon, the pinch rolls 14 and the pinch rolls 21 and 22 resume rotary activity and the blown pipe section 9 is advanced to clear the trailing end portion thereof from the pinch rolls 14. In correlation with this activity, the switch 48 is opened at the proper movement for breaking the energizing circuit to the solenoid 45, the valve 44 reverses, causing reversal of the piston 40 and retraction of the pinch roll 21 for releasing the blown pipe section. The released pipe section drops down onto a conveyor 54 as shown in Figure 1 and is carried on to a discharge point away from the machine. In the meantime, a succeeding pipe section 9 to be swabbed is advanced toward and into swabbing position and the cycle of operation resumed.

Inasmuch as chilling of the pipe sections 9 to be swabbed should be avoided, means are preferably provided for heating the pinch rolls 21 and 22. For this purpose electrical heating may be resorted to, the pinch rolls being provided with internal electrical heating units 55 supplied with electrical energy from a supply circuit 57' operatively associated with the electrical heating units 55 through the medium of appropriate commutator assemblies 58 carried by the drive shafts 28 for the pinch rolls.

The present application is a continuation-in-part of my copending application Serial No. 188,622 filed October 5, 1950, now Patent No. 2,753,837 dated July 10, 1956.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

' 1. In combination in apparatus for removing excess galvanizing material from successive sections of freshly galvanized pipe, means for externally swabbing the pipe sections as'they are advanced through a longitudinal path, means for advancing the pipe sections beyond said external swabbing means and including an overhead magnetic conveyor, and an internal swabbing blow tube having a mouth disposed for engagement by the leading end of each of the pipe sections after the same has been substantially advanced by said overhead conveyor, said overhead conveyor being controllable to release the pipe sections when the leading end of each of the sections is in proximity to the mouth of said blow tube, the improvement which comprises means operable at longitudinally spaced points on the successive pipe sections to thrust the same into the mouth of the blow tube after release from said overhead conveyor. 1

2. In combination in apparatus for removing excess galvanizing material from successive sections of freshly galvanized pipe, means for externally swabbing the pipe sections as they are advanced through a longitudinal path, means for advancing the pipe sections beyond said external swabbing means and including an overhead magnetic conveyor, and an internal swabbing blow tube having a mouth disposed for engagement by the leading end of each of the pipe sections after the same has been substantially advanced by said overhead conveyor, said overhead conveyor being controllable to release the pipe sections when the leading end of each of the sections is in proximity to the mouth of said blow tube, the improvement which comprises means operable at longitudinally spaced points on the successive pipe sections to thrust the same into the mouth of the blow tube after release from said overhead conveyor, said thrust means including a set of pinch rolls engageable with the trailing end portion of the successive sections and a set of pinch rolls disposed to engage the pipe sections at a more advanced point and operable to engage the pipe sections after release of the pipe sections from the overhead conveyor.

3. In combination in apparatus for removing excess galvanizing material from freshly galvanized pipe sections, a spatter chamber, said chamber having a passage therethrough, means for advancing a freshly galvanized pipe section through said passage, means at the exit side of said passage for externally swabbing the pipe section and driving the excess galvanizing material from the exterior of the pipe section into the spatter chamber, a set of pinch rolls immediately beyond said external swabbing means engageable with the pipe section for advancing the same past said external swabbing means, an overhead magnetic conveyor engageable with the pipe section beyond said pinch rolls, and an internalswabbing blow tube having a mouth disposed to be engaged by the leading end of the pipe section after the trailing end thereof has attained a position close to the exit of the spatter chamber but remains therein for delivering a blast of internal swabbing fluid into the pipe section, said overhead magnetic conveyor being controllable to release the pipe section therefrom when the leading end of the pipe section reaches a position proximate said blow tube mouth, the improvement which comprises means operative supplementary to said pinch rolls for imparting forward thrust to the pipe section after release thereof from said overhead conveyor in order to assure a firm and undisplaceable engagement of the leading end of the pipe section in said blow tube mouth when the internal swabbing blast is released thereinto.

4. In combination in apparatus for removing excess galvanizing material from freshly galvanized pipe sections, a spatter chamber, said chamber having a passage therethrough, means for advancing a freshly galvanized pipe section through said passage, means at the exit side of said passage for externally swabbing the pipe section and driving the excess galvanizing material from the exterior of the pipe section into the spatter chamber, a set of pinch rolls immediately beyond said external swabbing means engageable with the pipe section for advancing the same past said external swabbing means, an overhead magnetic conveyor engageable with the pipe section beyond said pinch rolls, and an internal swabhing blow tube having a mouth disposed to be engaged by the leading end of the pipe section after the'trailing end thereof has attained a position close to the exit of the spatter chamber but remains therein for delivering a blast of internal swabbing fluid into the pipe section, said overhead magnetic conveyor being controllable to release the pipe section therefrom when the leading end of the pipe section reaches a position proximate said blow tube mouth, the improvement which comprises means operative supplementary to said pinch rolls for imparting forward thrust to the pipe section after release thereof from said overhead conveyor in order to assure a firm and undisplaceable engagement of the leading end of the pipe section in said blow tube mouth when the internal swabbing blast is released thereinto, said supplemental means comprising a set of pinch rolls engageable with an advanced portion of the pipe section.

5. In combination in apparatus for removing excess galvanizing material from successive sections of freshly galvanized pipe, an internal swabbing blow tube, and means for advancing a freshly galvanized pipe section into operative relation to said blow tube, the improvement which comprises means for gripping the pipe section to be blown at longitudinally spaced points and thrusting the leading end of the pipe section into firm engagement with said blow tube.

6. In combination in apparatus for removing excess galvanizing material from successive sections of freshly galvanized pipe, an internal swabbing blow tube, and

means for advancing a freshly galvanized pipe section into operative relation to said blow tube, the improvement which comprises means for gripping the pipe section to be blown at longitudinally spaced points and thrusting the leading end of the pipe section into firm engagement with said blow tube, said last mentioned means including separate pairs of cooperating pinch rolls,

7. In combination in a machine for removing excess galvanizing material from freshly galvanized pipe sections and including an internal swabbing blow tube having a mouth into which the leading end of a pipe section is adapted to be inserted for receiving a blast of internal swabbing fluid from the blow tube, the improvement which comprises a pair of pinch rolls at substantial distance from the blow tube for engaging and advancing a pipe section endwise toward the blow tube, and a second pair of pinch rolls nearer the blow tube for engaging the pipe section, both of said pairs of pinch rolls having driving means operable to thrust the pipe section toward and into engagement with the blow tube and being responsive to predetermined thrust pressures to yield sufiiciently to avoid further rotation of the rolls while continuously maintaining forward thrust force on the engaged pipe section.

8. In combination in apparatus for removing fluent excess galvanizing .metal from successive sections of freshly galvanized pipe, and including a blow tube having a discharge end disposed for operation in a fixed position, an overhead magnetic conveyor comprising conveyor rolls spaced apart and mounted to direct a freshly galvanized pipe endwise toward engagement with said blow tube discharge end, and means for continuously actuating said magnetic conveyor rolls, said conveyor rolls being operable to drop the pipe therefrom at approximately reaching of the advance end of the pipe into engagement with said blow tube end, the improvement which comprises a vertical supporting structure mounted intermediate said conveyor rolls, a pair of cylindrical periphery pinch rolls mounted on vertical shafts on said supporting structure and with the peripheries of the pinch rolls spaced apart on respectively opposite sides of the path of movement of the pipe between said conveyor rolls, means for relatively actuating the pinch rolls to move into and out of gripping relation to a pipe therebetween coordinated to effect gripping of a pipe when the pipe is dropped by said conveyor rolls, and means for rotating said pinch rolls to drive the pipe forwardly endwise for engagement at its leading end with said blow tube end, said last mentioned means being responsive to thrust pressure of the end of the pipe against the end of the blow tube to yield for halting of rotation of the pinch rolls upon halting in the forward movement of the pipe so as to avoid marring the freshly galvanized external surface of the pipe.

9. In combination in a machine for removing excess galvanizing material from freshly galvanized pipe sections, an internal swabbing blow tube having a mouth into which the leading end of a pipe section is adapted to be inserted for receiving a blast of internal swabbing fluid from the blow tube, and a pair of pinch rolls at substantial distance from the blow tube for engaging and advancing a pipe section endwise toward the blow tube, the improvement which comprises a second pair of pinch rolls nearer the blow tube for engaging the pipe section, said pairs of pinch rolls having respective driving means operable to thrust the pipe section toward and into endwise engagement with the blow tube mouth to maintain the end of the pipe section firmly in said month while swabbing fluid is blown into the pipe, and respective pinch roll driving means including respective means responsive to predetermined thrust pressure of the pipe section into said mouth to yield sufliciently to avoid further rotation of the respective pairs of rolls while continuously maintaining forward thrust force on the engaged pipe section.

10. In combination in apparatus for removing excess galvanizing material from successive sections of freshly galvanized pipe including an internal swabbing blow tube, and means for advancing a freshly galvanized pipe section into operative relation with said blow tube, the improvement which includes part of said advancing means and additional means cooperative therewith for gripping the pipe section to be blown at longitudinally spaced points and thrusting the leading end of the pipe section into firm engagement with the blow tube.

11. In combination in apparatus for removing excess galvanizing material from successive sections of freshly galvanized pipe including an internal swabbing blowing tube, and means for advancing freshly galvanized pipe section into operative relation with said blown tube, the improvement which comprises separate pairs of pinch rolls for gripping the pipe section to be blown at longitudinally spaced points and thrusting the leading end of the pipe section into firm engagement with said blow tube, at least one of said pairs of pinch rolls being separable for releasing and gripping the pipe section.

12. In combination in apparatus for removing excess galvanizing material from successive sections of freshly galvanized pipe including an external swabbing ring arranged for passage of the pipe section therethrough, an internal swabbing blowing tube, and means for advancing freshly galvanized pipe section into operative relation with said blow tube, the improvement which comprises separate pairs of pinch rolls for gripping the pipe section to be blown at longitudinally spaced points and thrusting the leading end of the pipe section into firm engagement with said blow tube, at least one of said pairs of pinch rolls being separable for releasing and gripping the pipe section,

References Cited in the file of this patent UNITED STATES PATENTS 2,606,846 Pearson Aug. 12, 1952

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