Automatic pipe swaging device with hydraulic transmission

Abstract: The pipe swaging device (10) is provided with hydraulic transmission (44, 54, 52) for tightening the two jaws of a pipe squeezing gripper, and with valve means (90, 99, 102) for automatically opening shut-off means (104) for causing the pressure in the hydraulic transmission to fall in order to release the jaws when said pressure attains a value which corresponds to the required degree of squeezing of the pipe.

Description: This invention relates to a metal pipe swaging device, and in particular a pipe swaging device with hydraulic transmission. These devices are known to be provided with a conventional pipe squeezing gripper, the two opposing jaws of which are made to approach each other in order to swage a pipe. Devices of this type have been increasingly used in recent years in plant construction (for example in heating plants and in water or air distribution plants), in particular for connecting together two pieces of metal pipe by means of a metal sleeve, under cold conditions. The sleeve is inserted in known manner into the outer pipe piece, which is then squeezed usually in two different positions to form the connection. Sealing is achieved by two or more 0-rings. As is well known, the connection can also be made by a coupling to which the two pipe pieces to be connected together are fixed in the aforesaid manner, these being mounted over it or inserted into it. A swaging device with hydraulic transmission is described in EP-A-0908657, of the same proprietor as the present application, and comprises: a cylinder within which a coaxial rod is movable in both directions, one of its ends sealingly projecting from one end of the cylinder, to the other end of the rod there being coaxially fixed a sealed piston which divides the interior of the cylinder into a first and a second chamber both containing an incompressible liquid, the projecting end of the rod carrying means for operating the pipe squeezing gripper following volume increase in the first chamber; a reservoir also containing said incompressible liquid, the reservoir shell being in part deformable elastically, within determined limits, following variation in the quantity of liquid present in the reservoir; a plunger pump to withdraw the liquid contained in the reservoir and to feed it under pressure into said first chamber of the cylinder via a first conduit; a second conduit which connects the second chamber of the cylinder to the reservoir; a third conduit which connects the first chamber to the reservoir by by-passing the pump; manually operable shut-off means for interrupting the third conduit; elastic return means for moving the rod into the position corresponding to minimum volume of the first chamber of the cylinder when the shut-off means in the third conduit are open; and a safety valve which enables the incompressible liquid to be discharged from the first into the second chamber when the cylinder rod reaches its end of travel, this situation corresponding to maximum projection of the rod from the cylinder. In particular, in the embodiment illustrated in EP-A-0908657, the rod is hollow to connect the first chamber to the second chamber and hence to the reservoir via the second conduit. Communication between the first and second chamber is interrupted by said safety valve, disposed within the rod cavity and consisting of a ball valve maintained closed by the adjustable elastic reaction force of a relative precompressed spring. The safety valve opens when the cylinder rod attains its maximum allowable projection, so avoiding unnecessary and dangerous overpressures. Although this pipe swaging device has had much success because of its manageability (due to its small dimensions and low weight) and reliability, it has been found that the result of the swaging operation can depend on the ability and experience of the operator, because this latter has-no indication when the pressure of the. incompressible liquid in the first chamber has reached a value which ensures sufficient squeezing action on the relative pipe. In this respect, the only limit on the pressure in the first chamber is that set by the safety valve, which however acts only when the rod has reached its end of travel, a situation which, in order to save time, an experienced operator does not normally allow to be reached, by intervening beforehand on said shut-off means (which in the embodiment illustrated in EP-A-09808657 are controlled by a simple handwheel operable manually by the operator) in order to interrupt the squeezing operation on the pipe when he considers that sufficient swaging has been achieved. It has however been found that the operator, especially if insufficiently experienced, is not always able to judge when he has to operate the shut-off means in order to halt the squeezing operation. The object of the present invention is therefore to provide a swaging device with hydraulic transmission which enables proper swaging to be automatically achieved without operator intervention, so that the swaging operation becomes independent of operator ability or experience, and a new swaging cycle cannot be executed without the intervention of the operetor. This object is attained by the pipe swaging device according to claim 1. Hence a pipe swaging device is provided which enables a pipe to be automatically and correctly swaged without the operator having to do anything other than operate the pump of the device. In this respect, when a pressure corresponding to correct pipe swaging is attained in the first chamber, said valve means operate to open the shut-off means and hence cause the pressure in the first chamber to fall, so that the elastic piston return means return this latter into its initial position. Consequently the jaws of the pipe squeezing gripper are automatically released. It is apparent that the valve means of the swaging device according to the invention also operate as a safety valve, so that a specific safety valve as provided in EP-A-0908657 is no longer required. Conveniently said valve means are adjustable in order to be able to adjust within a determined range the maximum desired value of the pressure of the incompressible liquid in the first chamber, i.e. the pressure at which said valve means open to allow discharge into the reservoir. Summarizing, the swaging operation is no longer dependent on the operator, so that any operator, even the most inexpert, is able to effect the operation with excellent results. The invention will be more apparent from the ensuing description of one embodiment thereof. In this description reference is made to the accompanying drawing, in which: Figure 1 is a partial longitudinal section through part of a motorized pipe swaging device of the present invention; and Figure 2 is an enlarged longitudinal section therethrough, taken on the line 2-2 of Figure 1. The pipe swaging device 10 illustrated in the figures is shown without the relative pipe squeezing gripper, for simplicity. This latter is however of conventional type, for example of the type represented and described in EP-A-0908657. The device 10, as in the case of the pipe swaging device described in EP-A-0908657, comprises an operating means of electric motor type, shown only in part in Figure 1 for simplicity, and consisting basically of an electric drill 12 of gun type (i.e. provided with a handgrip, not shown, similar to that of a gun) from which the chuck has been removed and replaced with a train of gears 14, 16, 18 which transmit the rotary movement of the motor shaft pinion 20 of the drill 12 to a cam 22, the lateral surface of which engages a cam follower 24 provided with a helical return spring 26. The cam follower 24 is integral with the end of a plunger 28 of a pump 30, the plunger 28 being movable in both directions within a relative cylinder 32. When the operator operates the electric motor (not visible) of the drill 12, this rotates the pinion 20 so that, by virtue of the gear train 14, 16 and 18, the cam 22 and the cam follower 24, the plunger 28 of the pump 30 moves with reciprocating movement. In particular, when the plunger 28 rises upwards (with reference to Figure 1), incompressible liquid (preferably mineral oil for hydraulic transmissions) is drawn from a reservoir 34 via a suction conduit 36 and a first unidirectional ball valve 38. In contrast, when the plunger 28 descends, it causes the first valve 38 to open and a second unidirectional ball valve 40 to close, so that the liquid contained in the cylinder 32 of the pump 30 is fed through a first conduit 46, 48 to a first chamber 42 (shown in Figure 1 in its minimum volume condition) provided in a cylinder 44. Slidable in both directions within this latter, there is a piston 54 provided with an 0-ring 56 and integral with one end of a coaxial rod 52, the other end of which projects from the left end of the cylinder 44. The piston 54 divides the interior of the cylinder 44 into two chambers, one of which is the aforesaid first chamber 42, the second chamber being indicated by 58 (represented in Figure 1 in its maximum volume condition). The chambers 42 and 58, filled with the same incompressible liquid contained in the reservoir 34, have a variable volume which depends on the position of the piston 54, this position also determining the projection of the outer end of the rod 52 from the cylinder 44. As already stated, when the pump 30 is operated by the operator (who presses the relative pushbutton positioned on the gun-shaped grip, not shown), the pump draws liquid from the reservoir 34 and feeds it under pressure into the first chamber 42. On the right face (Figure 1) of the piston 42 there is thus a pressure greater than on its opposite face, hence causing the piston 54 to move towards the left against a helical return spring 55 mounted on the rod 52. Consequently the rod 52 increases its projection from the cylinder 44. As incompressible liquid is also present in the second chamber 58, when the piston 54 moves towards the left this liquid is made to flow out into the reservoir 34 through a second (return) channel 72, the mouth 73 of which is never reached by the piston 54 and hence is always open. As already stated, the reservoir 34 has a deformable wall portion, which in this specific case consists of a cup-shaped elastic membrane 74 (for example of rubber or a suitable plastic material). The edge of the membrane 74 is sealingly locked in position by a cover 76 having a number of through holes 78 so that atmospheric pressure acts on the outside of the membrane 74. The membrane 74 allows compensation of the incompressible liquid volumes involved. On the left end of the cylinder 44 there is coaxially mounted a usual fork 84 which can rotate, relative to the cylinder 44, about an axis coinciding with the axis of this latter. For greater details reference should be made to EP-A-0908657. It is sufficient to state here that on the projecting end of the rod 52 there are mounted two coplanar idle rollers 80 disposed between the two arms of the fork 84. When, following operation of the pump 30, the piston 54 moves towards the left, the rollers 80 also move towards the left, to diverge the close-together ends of the two jaws of a pipe squeezing gripper (not shown) mounted on the fork 84, the two jaws hence squeezing a relative pipe previously disposed between them. As can be seen from Figure 2, the first conduit 46, 48 communicates via auxiliary conduit portions 86 and 88 with a first auxiliary unidirectional ball valve 90, which enables the connection between the first conduit 46, 48 and the reservoir 34 to be interrupted, this connection being made via further conduit portions downstream of the first auxiliary valve 90 and which will be described hereinafter. Again from Figure 2, it can be seen that the first auxiliary valve is maintained closed by the action of a precompressed spring 92 which is chosen and set (by means of the screw 105 covered by the screw plug 103) such that this first auxiliary valve 90 opens when the pressure in the first chamber 42 (and hence in the first conduit 46, 48 and consequently in the auxiliary conduits 86, 88) reaches a value which ensures the required degree of squeezing of the pipe disposed between the jaws of the squeezing gripper. On opening the first auxiliary valve 90, the said pressure is transmitted downstream of the valve 90 via a conduit 94 and an aperture 96 which opens into a first auxiliary chamber 98 delimited by an auxiliary cylinder 99 and an auxiliary piston 100. This latter separates the first auxiliary chamber 98 from a second auxiliary chamber 101. From that face of the auxiliary piston 100 facing the second auxiliary chamber 101 there extends a coaxial pin 102 the purpose of which will be apparent hereinafter. Attainment of the required pressure in the first chamber 42 of the cylinder 44, corresponding to correct pipe squeezing, causes the first auxiliary valve 90 to open, so that the first auxiliary chamber 98 is also pressurized. Consequently the auxiliary piston 100 moves upwards (Figure 2) so that the pin 102 opens a shut-off ball valve 104 against the action of a relative helical spring 106. This causes the pressurized liquid contained in the first chamber 42 of the cylinder 44 to discharge into the reservoir 34 via the upper portion 48 of the first conduit, the shut-off valve 104 and a first discharge conduit 108 (of which only the commencement is seen in Figure 2) which opens into the reservoir 34. The reduction in pressure in the first chamber 42 of the cylinder 44 causes the piston 54 to return to its initial position (that shown in Figure 1) by the action of the helical spring 55. It also causes the first auxiliary valve 90 to close, so that pressurized liquid remains in the auxiliary conduit 94 and in the first auxiliary chamber 98, to maintain the auxiliary piston 100 in that position in which the shut-off valve 104 is open, this situation preventing the execution of a new swaging cycle but enabling the piston 54 to return. To completely restore the initial condition a lever 110 operable by the operator is provided which, when pressed, exerts a pressure on one end of a pin 112, to urge it inwards against the action of a helical return spring 118, so that the other end of the pin 112 opens a second auxiliary unidirectional ball valve 114 which interrupts communication between the first auxiliary chamber 98 and a second discharge conduit 116 (of which only the initial portion is seen in Figure 2) which opens into the reservoir 34. Opening the second auxiliary valve 114 causes the pressure of the liquid within the first auxiliary chamber 98 to fall, so that when the operator activates the pump 30, the shut-off valve 104 closes, to hence close communication between the first chamber 46, 48 and the first discharge conduit 108. In closing, the shut-off valve 104 hence urges the auxiliary piston 100 into its original position shown in Figure 2. Simultaneously the lever 110 also returns to its initial position by virtue of the return spring 118. The initial condition is hence completely restored, so that the device 10 is ready to effect a new pipe swaging operation. Although in the illustrated and described embodiment of the pipe swaging device of the present invention the pump is driven by an electric motor (in this specific case that of a gun-type electric drill), it should be noted that the pipe swaging device can also be non-motorized, in the sense that the pump drive means can be a conventional lever system which enables the operator to manually operate the pump by acting on a lever grippable by the operator. Such a manually operated variant is useful if a source of electrical energy is not available.

Claims: A pipe swaging device (10) in which the pipe squeezing gripper is operated by a hydraulic transmission, comprising: a cylinder (44) within which a coaxial rod (52) is movable in both directions, one of its ends sealingly projecting from one end of the. cylinder (44), to the other end of the rod (52) there being coaxially fixed a sealed piston (54) which divides the interior of the cylinder (44) into a first (42) and a second (58) chamber both containing an incompressible liquid, the projecting end of the rod (52) carrying means (80) for operating the pipe squeezing gripper following volume increase in the first chamber (42); a reservoir (34) also containing said incompressible liquid, the shell of the reservoir (34) being in part (74) deformable elastically, within determined limits, following variation in the quantity of liquid present in the reservoir (34); a plunger pump (30) to withdraw the liquid contained in the reservoir (34) and to feed it under pressure into said first chamber (42) of the cylinder (44) via a first conduit (46, 48); a second conduit (72) which connects the second chamber (58) of the cylinder (44) to the reservoir (34); a third conduit (48, 108) which connects the first chamber (42) to the reservoir (34) by by-passing the pump (30); shut-off means (104) for interrupting the third conduit (48, 108); elastic return means for moving the rod (52) into the position corresponding to minimum volume of the first chamber (42) of the cylinder (44) when the shut-off means (104) in the third conduit (48, 108) are open;. characterised by comprising valve means (90, 99, 100, 102) for automatically opening the shut-off means (104), in order to enable the incompressible liquid in the first chamber (42) to discharge into the reservoir (34), when a predetermined pressure corresponding to the required, degree of pipe squeezing is attained in the first chamber (42), the valve means comprising a first auxiliary valve (90) which opens when the pressure in the first chamber (42) of the cylinder (44) reaches the desired value, the opening of said first auxiliary valve (90) pressurizing a first auxiliary chamber (98) of an auxiliary cylinder (99) within which there can slide in the two directions an auxiliary piston (100) which separates the first auxiliary chamber (98) of the auxiliary cylinder (99) from a second auxiliary chamber (101) which communicates with the reservoir (34) and, via said shut-off means (104), with the first chamber (42) of the cylinder (44), the shut-off means (104) being closed when the first chamber (42) of the cylinder (44) is under pressure, the first auxiliary chamber (98) communicating with the reservoir (34) via a second auxiliary valve (114), the second auxiliary valve (114) being closed when the first auxiliary chamber (98) is under pressure, the auxiliary piston (100) presenting means (102) which enable the shut-off means (104) to be opened when the first auxiliary chamber (98) is under pressure; means (110, 112) operable by the operator being provided to open the second auxiliary valve (114) to hence restore the starting condition. A pipe swaging device (10) as claimed in claim 1, wherein the valve means (90, 99, 100, 102) are adjustable. A pipe swaging device (10) as claimed in claim 1, wherein the second auxiliary valve is a unidirectional ball valve (114), the means operable by the operator for opening the second auxiliary valve (114) comprising a pin (112) sealingly movable in the two directions within a relative seat, the pin (112) being able to be urged inwards by the operator against the action of elastic return means (118) in order to open the second auxiliary valve (114) and hence enable the pressurized liquid contained in the first auxiliary chamber (98) to discharge into the reservoir (34). A pipe swaging device (10) as claimed in claim 3, wherein the means operable by the operator for opening the second auxiliary valve (114) comprise a lever (110) enabling the operator to press the pin (112) inwards. A pipe swaging device (10) as claimed in claim 1, wherein the first (98) and the second (114) auxiliary valve, and the shut-off means (104), are unidirectional ball valves. A pipe swaging device (10) as claimed in claim 1, wherein the elastically deformable wall portion of the reservoir (34) is an elastic membrane (74). A pipe swaging device (10) as claimed in claim 1, wherein the pump operating means is manual. A pipe swaging device (10) as claimed in claim 1, wherein the pump (30) operating means is an electric motor. A pipe swaging device (10) as claimed in claim 8, wherein the electric motor forms part of an electric drill (12) of gun type, the chuck having been removed from the drill(12) and replaced by a train of gears (20, 14, 16, 18) which transmit the rotary movement of the motor shaft of the drill (12) to a cam (22), the periphery of which engages a cam follower (24) rigid with the outer end of the rod of the plunger (28) pump (30). A pipe swaging device (10) as claimed in claim 1, wherein the pipe squeezing gripper is operated by two coplanar idle rollers (80) mounted on the projecting end of the rod (52) and disposed between the two branches of a fork (84).

Inventors: VEZZANI GIORGIO, VEZZANI, GIORGIO
Applicants: CBC SPA, C.B.C. S.P.A.
Application year: 2001
Main classification: B21D39
IPC codes: B25B27, B21D39