US3112661A - Hydraulic system for reducing mills and the like - Google Patents

Description

e. B. coE 3,112,561 HYDRAULIC SYSTEM FOR REDUCING MILLS AND THE LIKE Dec. 3, 1963 2 Sheets-Sheet 1 Filed March 28, 1961 INVENTOR.

GEORGE B. COE

Ill/Ill!!! ZN, slimfiw iz Dec. 3, 1963 G. B. coE 3,112,661

HYDRAULIC SYSTEM FOR REDUCING MILLS AND THE LIKE Filed March 28, 1961 2 Sheets-Sheet 2 FIG. 2

IN V EN TOR.

' G EORGE B. CO E ATTORNEYS United States Patent 3,112,661 7 I HYDRAULIC SYSTEM FOR REDUCING MHLS AND THE LIKE George B. Coe, Westfield, N.J., assignor to Tube Reducing Corporation, a corporation of Delaware Filed Mar. 28, 1%1, Ser. No. 98,834 8 Claims. 01. 80-14) This invention relates to fluid driving systems for stock reducing machines and similar mills and, more particularly, to a closed hydraulic system adapted to operate the stock manipulating means of such mills.

Reducing machines of the type with which this invention is especially concerned are mills in which metal stock, in the form of either tubes or rods, is advanced intermittently into reciprocating dies which reduce its diameter in successive longitudinal increments. A full description of such a reducing machine is set forth in my United States Letters Patent No. 2,954,126. The reducing dies generally comprise a pair of opposed cylindrical rolls, each having a tapered circumferential groove formed therein, and are mounted one over the other in a reciprocable saddle such that the tapered grooves are in direct opposition. The stock is advanced into the opposed grooves and, as the dies reciprocate with the saddle, the stock is reduced within the converging walls of the tapered grooves. At the end of each forward working stroke of the dies, the stock is given an incremental turn about its axis, perhaps a quarter-turn, so that when the dies roll back over the stock any undesired fins or the like in the worked portion may be faired out. Upon returning to starting position, the stock is fed forward a longitudinal increment so that an additional portion thereof is brought into the working zone, and the finished reduced stock advances out of the dies at the outlet side thereof. If tubular stock is being reduced, a tapered mandrel is usually located within its bore at the working zone between the dies to support and size the inside surface of the tube. Ordinarily, the mandrel is mounted on a rearwardly extending rod and is turned along with the stock at the end of each working stroke of the dies.

(To carry out these feeding and turning steps at the proper time during the cycle of operation, two turning devices and one feeding device are usually included in a tube reducing machine. The two turning devices are (1) an assembly at the inlet end of the machine which engages both the stock and the mandrel rod (if any) and which can turn both elements about their common longitudinal axis, and (2) an assembly at the outlet end of the machine which grips the emerging reduced stock to turn it in unison with the first-mentioned assembly at the inlet end of the machine. By these means, the stock can always be turned even when its trailing end is entering the dies. The stock feeding mechanism comprises a longitudinally movable non-rotatable screw shaft which may be advanced intermittently by a rotatable non-translata-ble feed-nut assembly. The forward end of this screw shaft urges the stock gripping assembly (i.e., that part of the first-mentioned turning device which holds the stock) forwardly by increments as the feed-nut assembly is intermittently turned.

Heretofore, the most successful means for operating these feeding and turning devices was a hydraulic system which was actuated by a timer cam driven in synchroniza-. tion with the reciprocating saddle in which the dies are mounted. In general, this known hydraulic system is as follows: A fluid motor is provided to drive each of the inlet turning device, the outlet turning device, "and the feeding device. To send fluid under pressure through these motors at the proper moment to effect their desired intermittent operation, three respective cylinder and piston assemblies are provided and are operated by a common 3,112,661 Patented Dec. 3, 1963 rotating timer cam synchronized to make one revolution at each complete stroke of the saddle. Each cylinder and piston assembly intermittently displaces a certain volume of fluid to its associated fluid motor to operate the motor at the desired time. The fluid discharge from each motor is directed into a reservoir which supplies the pistons with additional fluid during each non-working return stroke thereof.

One of the greatest difiiculties in driving precisely timed machinery .by fluid motor systems of this sort is to insure that the motors stop their operation at exactly the right moment. In an attempt to achieve this in the system described above, it has been proposed to include a brake valve in the outlet or discharge conduit of each fluid motor to halt the flow of drving fluid and cease the motors operation at the precise time desired. Absent such-brake valves, the momentum of the motors and their driven parts causes over-travel which is in no way prevented by the fluid surging into the open reservoir. However, the fluid valves which prevent over-travel also act as accumulators and build up considerable backpressure in the system. The cylinder and pump assemblies must work against this back pressure, of course, and the actuation by the timer cam is made just that much more diflicult. As a result, considerably more power must be put into the hydraulic system than is actually used for effective work. This factor of inefliciency alone is a serious disadvantage, but the problem is worsened by the great amount of heat energy which develops in the hydraulic system. Furthermore, and this is perhap'sthe most serious defect of the conventional hydraulic system, the speed of the machine is definitely limited by the feed and turn driving system. Because of high back-pressure, the extra actuating force necessarily developed by the timer cam, and the increased temperature of the system,the conventional tube reducingmachines cannot be operated above a certain speed without adversely aifecting the timing of the stock fee'd and turn mechanisms. Obviously, this imposes a definite limit on the productive output of each mill.

The present invention constitutes an improvement over reducing machines of the type described in my aforementioned Letters Patent, namely those having reciproca-ble dies and at least one stock moving (e.g., feeding or turning or both) (device. Broadly stated, the invention provides a closed fluid driving system for such a device comprising a fluid motor having inlet and outlet ports. Variable capacity fluid pumping and receiving chambers are provided in communication respectively with these inlet and outlet ports. A conduit interconnects the chambers. Means are included for maintaining unidirectional flow from the pumping chamber through the motor to the receiving chamber and thence through the conduit back to the pumping chamber. Means are also'provided for maintaining this system completely filled with operating fluid. Actuating means are included for contracting the pumping chamber and expanding the receiving chamber an equal amount to operate the motor Without over-travel thereof and then contracting the receiving chamber and expanding the pumping chamber. an equal amount to return the system to starting position without operating the motor. 1

It is apparent that this new fluid driving system is closed as opposed to the conventional open system described hereinbefore. In the old system, fluid is pumped through the motors and into an open reservoir only after pumping pressure exceeds the maximum accumulated back-pressure established by the brake valves. The reservoir, which is never subjected to pump pressure, is. definitely part of the fluid circuit. In the new system,

however, fluid travels from each pump to the associated,

motor and back to the pump in a closed circuit, and the reservoir'is employed only to dispense added fluid into thesystem when needed to compensate for leakage. Overtravel of each fluid motor is prevented with maximum eliectiveness because the receiving chamber downstream of the. motor accepts discharge fluid only to the extent that operating fluid is pumped into the motor from the pumping chamber. Hence, as the pumping chamber contracts. to operate the motor, the receiving chamber expandsto accept the discharge fluid. Assoon as the pumping action stops, so too. does the acceptance of'the discharge fluid in the receiving chamber, and the operation of the motor is thereby cut off immediately. Under these conditions, over-travel of the motor is virtually impossible.

Another important feature of the new system is that the pumps which operate the motors do not act against any significant back-pressure. There are no accumulators or brake valves or the like at any point in the line. As the. pump piston moves forward, it displaces. fluid only against the force of fluid friction and the resistance of the motor itself, becausev back-pressure is eliminated by the expanding receiving chamber.

Since. there is no appreciable back-pressure created in the. system provided by this invention, there is practically no heat given. off by the fluid even after prolonged operation of the machine. More importantly, the absence of back-pressure permits the pistons to move back and forth at whatever speed is. desired, and still the fluid motors driven thereby start and stopat precisely the predetermined times. No longer is the output of the reducing mill limited bythe. operation of the feeding and turning devices. It isnow possible to run the machine at thehighest rate. at which thesaddle can be reciprocated.

A preferred embodiment of the. invention is described hereinbelow: with reference to the accompanying drawings, wherein.

FIG; 1 is a schematic illustration of one form of the new fluid system in conjunction with the basic elements of a. tube reducing machine; and.

BIG; 2.is' a si'milarillustration of. another form. of the new; system. Referring to bothFIGS. l and'2, a sufficient number ofthe basic elements of a tube reducing machine are shown for purposes of understanding the present invention. They-are describedat the same time with reference to the embodiments of both figures, though the reference nu merals, are primed in FIG. 2 for purposes of. distinction. For a full and complete discussion of'the overall structure and function of atube reducing machine, reference may be had tomy aforementioned Letters Patent. A pair of dies are mounted in a saddle 11 which is. adapted to bereciprocated back and-fortl so that the dies roll against one another. Both dies have taperedv groovesformed'in their-circumference, which grooves. together define a die orifice. A. length of tubular stock 12 isinserted between the dies within the groovesthereof and a tapered-'- mandrel 13: supported by a mandrel rod 14. extends within the stock to theworking zone between the dies 10; As the dies. rollback and forth, they; reduce both the inside and outside diameter of the stock 12 against the mandrel 13' to form asmooth finished tube12A which advances from; the exitend of the machine.

At' the end of each forward stroke of' the saddle and dies: (in the position thereof shown in both FIGS. 1 and- 2 the stock 12 is turnedat both the inlet and outlet endsof the machine; For this purpose, the stock 1 2- is held at itsv trailing end by a releasable chuck 16 and-at its forward end by. a gripper. 17; Thechuck 16 is rotatably mounted and can be turned by agear train 18 drivenfrom a; shaft 1 9 Which, in turn, can be intermittently rotated by a fluid motor 20; Likewise, the gripper 17' is. rotatably mounted and can be -turned by a gear- 21 driven Notonly is the stock 12 turned at the inlet end ofthe machine butthe mandrel 13is turned withit'. To achieve 4. this, the shaft 19 extends rearwardly to a gear train 23 which can rotate the rear end of the mandrel rod 14' rotatably mounted in a mandrel rod carriage 25. During operation of the machine, the carriage 25 is held locked by a suitable latch 26 to prevent any longitudinal displacement of the mandrel. 13. s

By these means, a partial turn is imparted to the stock and mandrel. (e.g.,. av quarter-turn) by a brief periodic actuation of the turning motors 20 and 22. With turning means on both sides of the saddle and dies, there is always assurance that a portion of the stock. will be gripped and turned even though its trailing end may be entering the dies. By imparting a slight turn to the stock at each stroke of the dies, successively different circumferential portions of the stock are presented to. the working surfaces of the dies, so that any ovality orthe like which: may be formed during the previous working stroke are flattened out.

At the end of each return stroke of the saddle and dies, the stock is advanced a predetermined longitudinal increment to move successive unworked portions thereof into the working zone between the dies. For this pur pose, the stock gripping chuck 16 is' not only rotatably mounted but is also longitudinally displaceable on a suitable carriage which can be moved by the forward end ofa feed screw 27. The feed screw 27 is non-rotatable, but can be. longitudinally displaced to move the chuck 16 either forwardly or rearwardly. The. means for displacing thefeed screw 27 comprises. a feed-nut 28in threaded; engagementtherewith which is rotatably mounted but is non-translatable. A fluid motor 29 is provided to rotate the feed-nut 28 in either direction to advance or retract the feed screw 27 and the stock 12. There is, of course, suitable structure.- to permit the feed screw 27 to. advance the chuck 16. and the stock 12 atthe same time the shaft 19 intermittently turns the chuck 16. Such structure forms no part; of the present invention and is described fully inmy aforementioned. patent.

By these means, it is possible to advance. the stock 12 over the. mandrel 13 each time the dies 10 and'saddle 11 complete. their return stroke. Ordinarily, the 1011: gitudinal distance covered by. the. stock 12. in each increment: of feed is rather slight but must be quite precise inorder to; achieve a uniform working action within the dies.

Further auxiliary means are shown in both FIGS. 1, and: 2L by which the tube reducingv machine may be; returned. to its starting position preparatory tothe reduc tion of a new tube. As soon as the trailing end? of the previouslength of stock 12 nears the dies 10, the saddle 11 is stopped for a brief period. The operator then. runs the feed motor 29 at relatively high speed in a reverse direction to withdraw the chuck 16 rapidly to the rear, i.e., to the left as seen in the figures. Also, the operator releases. the latch to free the carriage 25 and then withdraws the, mandrel 13 from the Working zone bymoving the mandrel rod carriage ZS reMWardIy. Thus, a. latch-actuator 31' is hydraulically operated to withdraw. the latch 26 and release the carriage 25. The carriageZS is mounted'on suitable longitudinal ways and is adapted. to. be displaced therealong by. an endless chain 32 mounted on sprockets 33. A mandrel pull-- back fluid motor 34v is provided: to drive this chain 32in either direction sothat the carriage 35 may be displaced reanwardly or forwardly asv desired; After the operator has withdrawn the mandrel 13 from the dies (by operatingthe latchfactuator 31 and the'pull-back motor 34), a. new. length of stock is. placed inthe machine and gripped by. the chuck 16. The mandrelipull-back mov tor 34' isthen actuated again to return the. mandrel into: the dies, and: the carriage 35 is. locked by the actuator:

31. The new stock is then advanced until it; abutsthe trailing end of the partly reduced stock within the dies,- and the tube reducing machine continues in its: operation.

Hence, there are five hydraulic driving meanswhich must be actuated to insure the desired operation of the tube reducing machine. The turning motors and 22 are to operate intermittently While the saddle and dies reciprocate back and forth. The feeding motor 29 must be capable of similar intermittent operation, but must also be reversible at high speed when it is desired to insert a new length of stock into the machine. Finally, the mandrel pull-back motor 34 and the latch-actuator 31 are selectively operated only when new stock is put into the machine.

It is the purpose of the invention to provide a new and improved fluid system for driving these various hydraulic means.

Referring first to the embodiment shown in FIG. 1, a timing mechmsm 35 is provided which is substantially the same as that described in my Letters Patent No. 2,594,126. Hence, it includes a cam 36 mounted on a countershaft 37 which is driven directly by the main driving means which reciprocates the saddle 11 of the tube reducing machine. The direct mechanical connection between the saddle drive and the countershaft 37 is such that the countershaft 37 makes one complete revolution upon each back and forth reciprocation of the saddle 11. The cam 37 is adapted to reciprocate a slide 38 back and forth so as to displace two primary drive rods 39 and 40. The drive rod 4% is adapted to actuate a double-acting piston 41 movable within a cylinder 42 and also to actuate a. double-acting piston 43 movable within a cylinder 44.

The cylinder 42 operates the stock and mandrel tuming motor 29 at the inlet end of the machine. On one side of the piston 41, a pumping chamber 45 is defined and on the other side thereof a fluid receiving chamber 46 is provided. The fluid motor Zfl includes an inlet portwhich is connected with the pumping chamber 45 by an inlet conduit 47 and an outlet port connected to the receiving chamber 46 by an outlet conduit 49. The pumping and receiving chamber 45 and 46 are connected by a conduit 50. To maintain this system completely filled with operating fluid, afeed conduit 51 leading to the conduit is in communication with a gravity feed reservoir 52. In order to provide proper unidirectional flowin the system (from the pumping chamber 45 to the motor 29, then to the receiving chamber 46, and finally back to the pumping chamber 45), a check valve 53 is provided in the outlet conduit 49, a check valve 54 is provided in the conduit 50 and a check valve 55 is provided in the supply conduit 51.

The piston 43 and cylinder 44, with which the primary rod 45 is also associated, are adapted :to operate the stock turning motor 22 at the outlet end of the machine. Again, the double-acting piston 43 defines a pumping chamber 57 and a receiving chamber 58. The former is connected by an inlet conduit 59 to an inlet port of the fluid motor 22, and the outlet port of the fluid motor 22 is connected by an outlet conduit 60 with the receiving chamber 58. interconnecting the pumping and receiving chambers is a conduit 61, and a feed conduit 62 leads from the reservoir 52 to the bypass conduit 61. Check valves 64 in the outlet conduit, 65 in the conduit Gland 66 in the supply conduit insure the proper unidirectional flow in the system, which is from the pumping chamber to the motor to the re ceiving chamber and back to the pumping chamber.

The turning motors 2t and 22 are operated as follows: The cam 36 is configured such that it drives the rod 40 to the right as seen in FIG. 1 each time the saddle 11 reaches the forward end of its stroke. Thus the piston 41 moves to the right, forcing fluid through the inlet conduit 47 and causing the motor 29 to turn and thus rotate the mandrel 13 and the stock 12 at the inlet end of the machine. There is little back-pressure because discharge fluid from the motor 20 is simultaneously forced through the outlet conduit 49 and into the expanding receiving chamber 46. Back-flow through the cham- V 6 ber 50 during this pumping stroke of the piston 41 is prevented by the check valve 54. As soon as the pump ing stroke of the piston 41 stops, the motor 20 also stops without any over-travel because the receiving chamber 46 no longer expands and there. is no space available for any further surge of fluid from the discharge port of the motor. Thus, the motor freezes and precise turning of the stock and mandrel is achieved. During'the return stroke of the saddle 11, the cam 3-6 causes the piston 41 to move to the left to return to its starting position. As this happens, back-flow through the outlet conduit 49 is preventedby the check valve 54 and the excess fluid in the receiving chamber -46 is forced into the pumping chamber 45 through the conduit 50. Any leakage of fluid from the system is compensated for upon demand rom the reservoir through the feed conduit 51 and the check valve 55. J

The motor 22 operates in exactly the same manner. The piston 43 moves in precise unison with the piston 41 to force fluid through the inlet conduit 59 and thereby rive the motor 22 without encountering appreciable back-pressure. Over-travel is likewise prevented since the receiving chamber 58 allows only a controlled discharge from the motor 22. Again, the return stroke of the piston 43 causes displacement of fluid from the receiving chamber 58 to the pumping chamber 57 through the conduit 61. 1 V

Returning now to the timing mechanism 35, its other primary rod 39 drives another double-acting piston 68 which operates Within a cylinder 69. The mechanical linkage therebetween includes a rocker arm 71 having an adjustable fulcrum 72 as described in my aforementioned patent. The piston 68 and cylinder 69 are adapted to operate the stock feeding motor 29, and thus apumping chamber 73 is connected by an inlet conduit 74 to the inlet port of the motor 29 and an outlet conduit 75 extends from the outlet port of the motor to a receiving chamber 76. An auxiliary system 77 for high speed reverse operation of the motor 24 described hereinbelow is not in operation when the motor29 is driven incremental ly in a forward direction. A conduit 80 interconnects the pumping andreceiving chambers 73 and 76 and a a supply conduit 81 leads from the reservoir 52. Unidirectional flow is maintained by check valves 82 in the outlet conduit, 83 in the conduit 80, and 84 in the sup; ply conduit. v I

The cam 36 is configured such that upon completion of each return stroke of the saddle 11, the piston 68 moves to the right to force fluid through the inlet conduit 74'to drive the motor 28 and thereby cause the stock to be fed forward a short distance. Back-pressure. and over-travel are both eliminated by-the controlled ex pansion of the receiving chamber 76 which receives the discharge fluid. Thereafter, the cam 36 causes the piston 68 to return to the left thus displacing fluid through the conduit 80 without aifecting the motor 29. A 2-way valve 78 is provided to divert fluid from the pumping chamber 73 to the reservoir 52 to interruptthestock feeding action when desired.

At those intervals when a new length of stock is placed in the machine, it is necessary to withdraw the chuck 16 and this is done by the auxiliary system 77 which is. i1 lustrated diagrammatically by a slide valve 85. In the solid line position of the valve 8 5, two bores 86 and 87 register with the inlet and outlet conduits 74 and 75 of the motor 29 so that the motor operates in a forward direction as described above when the saddle 11 is reciproeating. However, when the saddle is stopped and the valve 85 is moved to the right, the movable bores 86 87 register with a pump inlet conduit 89-89A and a pump outlet conduit 9090A. Fluid is forced through the inlet pump conduit 89-89A from a pump 92 by an auxi iliary motor 93. Hence, fluid is forced through the motor 29 in a direction reverse to that described previously and the dicharge flows back through the pump outlet conduit 90-90A and into the reservoir 52. From the reservoir, the fluid enters the pump 92 on demand through a feed conduit 95. This particular auxiliary system exemplifies means for driving the motor 29 in a reverse direction when desired.

Means are also included for operating the latch-actuator 31 and the mandrel pull-back motor 34. These include. a pump 97 supplied through a feed conduit 98 from the. reservoir 52 and driven by the motor 93 to pump. fluid. through a main inlet conduit 99 which branches into two secondary inlet conduits 100 and 161. The former passes through a 4-way valve 102 to. power the. latch-actuator 31 andthe discharge therefrom returns through the 4-way valve 102 to an inletconduit103 which leads, back to the reservoir 52. The other secondary inlet conduit 101 extends to another 4-Way valve 105 from which fluid can proceed to the mandrel pull-back motor 3.4 and. thence back through the 4-way valve 105 to the common. outlet conduit 103. Selective operation of the latchfactuator 31 and. themandrel pull-back motor 34 is made possible by changing the valves 102 and 105 from their. positionwhere they simply circulate the pumped fluidfrom they inlet conduit 99 immediately back through the return conduit 103 to by-pass the motor 34 and ac tuator 31..

Turning now to the embodiment of FIG. 2, a timing mechanism 107 is shown which is identical to that described. in the previous embodiment. It operates a main fluid driving. system: for the stock. and mandrel turning motor the stock turning motor 22., and the stock feeding motor 29. This is done here by means of singleacting pistons andv cylinders, whereas in the previous em? hodiment. double-acting pistons and cylinders were em{ ployed. Thus, the. stock and mandrel turning motor 20" at the inlet end of the machine is driven by a pumping chamber 1.08. in a. single-acting piston and cylinder assembly 109 and a receiving chamber 110 in another. single-acting pistonand cylinder assembly 111. As. is clear from.FIG-. 2, these pumping. and receiving chambers are inv association with suitable conduits and. check valves throughouh, such that the motor 20 can be driven. incrementally asin. the previous embodiment. However, it. is important. to note thatthe timing mechanism. 107 drives the assembly 109 from aprimary rod 115 and the assem-.- bly 110'. fromv a primary rod. 116. Both of these. rods have exactly the same stroke so that as one movesin the.

other moves outandthedisplacement within-the pumping and receiving. chambers 108 and 110. isv equal.

Likewise, thestock turning motor 22? at. theoutlet end of the. machine. is. incrementally turned by a single-acting pumpandcylinder assembly 118. having a pumping chamber 119 and. a single-acting pump cylinder assembly 120 having a receiving chamber 121. Suitableconduits are associated therewith as. above, along with the necessary check valves toprovide unidirectional flow. The assemhlies 1'18 and.120 are synchronized in the same manner The; stock feeding motor 29' is .alsodriven in the same a manner as in the previous embodiment except that here.

two; single-acting; piston and cylinder assemblies 124 and 125 are employed. rather than one double-acting assembly.. Thus, pumping and. receiving chambers 126 and 127 respectively workin unison to turn the motor 29intermittently. The necessary. conduits and. check valves are included asshown.

'An auxiliary system including a valve 130, auxiliary 7 pumps 131 and 132,1two 4-way valves. 133 and 134 and the required conduits therefor are provided for the selec tive periodic operation of the latch-actuator 31', the mandrel pull-back motor 34', and the high speed reverse All this is exactly receiving chamber and finally back to the pumping chamher. All this is done with no substantial back-pressure resisting the expansion and contraction of the pumping. and receiving chambers. More importantly, it. is impossible for the associated motors to over-travel because in the closed system all fluid motion ceases when the pistons in the pumping and receiving chambers stop their displacement. Hence, each motor travels to the extent desired While the pumping chamber contracts and the receiving chamber accepts the discharge fluid; but once the pumping chamber stops contracting and the receiving chamber likewise stops expanding, the incompressible fluid in the line prevents the associated motor from running any further. This prevention of over-travel allows the greatest precision in the degree in which the stock is fed and turned during the reducing process. Since there is no practical limit to the rate of oscillation of a closed system of the type provided herein, the production output of a machine embodying the invention is limited only by the speed at which the saddle can be reciprocated.

I claim:

1. In a mill for reducing stock including reciprocable dies and at least one stock moving device, a closed fluid driving system for said device comprising a fluid motor having inlet and outlet ports, variable capacity fluid pumping and receiving chambers in communication respectively with said inlet and outlet ports, a conduit interconnecting said chambers, means for maintaining unidirectional flow from said pumping chamber through said motor to said receiving chamber andthence through said conduit back to said pumping chamber, means for maintaining. said system completely filled with operating fluid, and actuating means for contracting said pumping. chamber and expanding. said receiving chamber an equalamount to operate said motor without over-travel thereof and. then contracting said receiving chamber and' expand-v ing said pumping chamber an equal amount to return the system to starting position without operating said motor. 2. Apparatus according to claim 1 wherein said means for maintaining said system completely filled with operating fluid comprises a reservoir, a feed'conduit extending from said reservoir to said closed system, and a check valve in said feed conduit for maintaining unidirectional flow'from said reservoir to said closed system.

3..Apparatus according to'claim. 1 wherein said fluid:

V pumping and receiving chambers are provided by two respective separate single-acting cylinder and piston assemblies;

4. Apparatus according to claim 1 which includes a double-acting cylinder and piston assembly wherein one side defines said pumping chamber and the other side defines said receiving chamber. 7 V

51 In amill for reducing tubular stock including; re

ciprocable" dies, a rotatable mandrel, a feeding device for intermittently advancing said stock, and a turning device for intermittently turning said mandrel and stock; a closed fluid driving system for operating each of said devices comprising a fluid motor. for each device having inlet and outlet ports, fluid pumping and receiving piston chambers in communication respectively With said inlet and outlet ports, a conduit interconnecting said chambers, check'valve means for maintaining unidirectional intermittent flow fromsaid pumping chamber through said motor to said receiving chamber and thence through said conduit back to said pumping chamber, means for maintaining said system completely filled with operating fluid, and

actuating means synchronized with said reciprocable dies for advancing and withdrawing the pistons of said pumping and receiving chambers respectively through an equal displacement to operate said motor without over-travel thereof and then Withdrawing and advancing said respective pistons through an equal displacement to return the system to starting position Without operating said motor.

6, In a mill for reducing tubular stock including reciprocable dies, a rotatable mandrel, a feeding device for intermittently advancing said stock, a first turning device on the inlet side of said dies for intermittently turning said mandrel and stock, and a second turning device on the outlet side or" said dies for intermittently turning the reduced stock; a closed fluid driving system for operating each of said devices comprising a fluid motor for each device having inlet and outlet ports, fluid pumping and receiving piston chambers in communication respectively With said inlet and outlet ports, a conduit interconnecting said pumping and receiving chambers, check valve means for maintaining unidirectional intermittent flow 20 from said pumping chamber through said motor to said receiving chamber and thence through said conduit back to said pumping chamber, a reservoir, a gravity feed conduit extending from said reservoir to said by-pass conduit, a check valve in said feed conduit for maintain- 25 ing unidirectional flow from said reservoir to said conduit, and actuating means synchronized with said reciprocable dies for advancing and withdrawing the pistons of said pumping and receiving chambers respectively through an equal displacement to operate said motor Without over-travel thereof and then withdrawing and advancing said respective pistons through an equal displacement to return the system to starting position without operating said motor.

7. Apparatus acording to claim 6 wherein said fluid pumping and receiving piston chambers are provided by two respective separate single-acting cylinder and piston assemblies.

8. Apparatus according to claim 6 wherein said fluid pumping and receiving piston chambers are provided by one double-acting cylinder and piston chamber wherein one side defines said pumping chamber and the other side defines said receiving chamber.

References Cited in the file of this patent UNITED STATES PATENTS 65,435 Richter June 4, 1867 2,594,126 Coe Apr. 22, 1952 2,932,223 Chartrand Apr. 12, 1960

Claims (1)

1. IN A MILL FOR REDUCING STOCK INCLUDING RECIPROCABLE DIES AND AT LEAST ONE STOCK MOVING DEVICE, A CLOSED FLUID DRIVING SYSTEM FOR SAID DEVICE COMPRISING A FLUID MOTOR HAVING INLET AND OUTLET PORTS, VARIABLE CAPACITY FLUID PUMPING AND RECEIVING CHAMBERS IN COMMUNICATION RESPECTIVELY WITH SAID INLET AND OUTLET PORTS, A CONDUIT INTERCONNECTING SAID CHAMBERS, MEANS FOR MAINTAINING UNIDIRECTIONAL FLOW FROM SAID PUMPING CHAMBER THROUGH SAID MOTOR TO SAID RECEIVING CHAMBER AND THENCE THROUGH SAID CONDUIT BACK TO SAID PUMPING CHAMBER, MEANS FOR MAINTAINING SAID SYSTEM COMPLETELY FILLED WITH OPERATING FLUID, AND ACTUATING MEANS FOR CONTRACTING SAID PUMPING CHAMBER AND EXPANDING SAID RECEIVING CHAMBER AN EQUAL AMOUNT TO OPERATE SAID MOTOR WITHOUT OVER-TRAVEL THEREOF AND THEN CONTRACTING SAID RECEIVING CHAMBER AND EXPAND-K ING SAID PUMPING CHAMBER AN EQUAL AMOUNT TO RETURN THE SYSTEM TO STARTING POSITION WITHOUT OPERATING SAID MOTOR.

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