US2365748A - Hydraulic circuit - Google Patents

Description

'm E@ Q44. F W, CURTIS 2936574@ HYDRAULIC CIRCUIT Filed Feb. 27, 1941 3 Sheets-Shee, l

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/ ATTOR N EYS F. vv. CUR-ns HYDRAULIC CIRCUIT Filed Feb. 27, 1941 5 Sheets-Sheet 2 Ffm f u @LM ATTORNEYS F. W. CURTIS 2,36,% j

HYDRAULIC CIRCUIT Filed Feb. 27, 1941 5 Sheets-Sheet 5 INVENTOR @fm/A MCa/s av J, a

ATTORNEYS Patented Dec. 236, 1944 HYDRAULIC cmcurr nunk w. curan, springfield, Mssg., minor to Van Norman Company, a corporation of Massachusetts Application February 27, 1941,'Serial No. 380,897

l Claims. (Cl. 60-52) This'invention relates to a hydraulic circuit anda control therefor, particularly adapted for machine tools such as mining machines.

Many forms of hydraulic controlling mech-- anisms have heretofore been proposed, and it is one object of the present invention to simplify these controlling mechanisms. It is a further object to construct a valve mechanism capable of giving feed and rapid traverse motion in one direction and rapid traverse motion in the reverse direction, and to regulate the speed by an adjustable throttle, preferablyA in the outlet, which is by-passed in order to secure rapid traverse. It is a further object to improve and simplify the hydraulic mechanism for shifting the control valve into reversing position. It is a further object to provide a simple and effective way of inverting the cycle of operation of the machine. Additional objects will appear from the following description and claims.

Referring to the drawings,

Fig. l is a diagrammatic view of the circuit;

Figs. 2 and 3 are diagrams showing two cycles obtained from the control mechanism by means of 'the cycle inverter;-

Fig. 4 is a diagrammatic view of the control valve mechanism vin position to impart rapid traverse in a forward direction, the cycle invert- Fig. 8 is a detail of a valve for controlling the spindle clutch.

Thevalve mechanism is intended in particular for operation with a hydraulic circuit such as is 4shown in Fig. l. A pipe leads from an oil sump' to a pump |2 which may be of any desired design but which is preferably of the constant delivery type. A relief valve I3 connected in the output pipe |4 of the pump has alconnection I5 leading back to the sump and functions in the usual manner to permit excess oil to pass out of the line I4 and to hold the pressure in that line substantially constant. The line |4 extends to a panel box lliY which is preferably constructed mechanically in accordance with my copending application Serial No. 396,857, led June 6, 1941, now Patent No. 2,308,647. The hydraulic 'features of the panel are shown in Figs. 4 to 7, and include a valve casing in which is a spool valve I8 of novel construction.

From the valve casing l1 extend several conduits arranged sequentially in the following order. At one end of the series is the fluid pressure pipe I4, leading into an annular chamber or port 26. An adjacent chamber I9 is separated from chamber 26 by an inwardly projecting rib 20. A conduit 2| leads from the chamber I9 to one end of the operating cylinder 22, preferably through a cycle-inverting four-way valve 23 and a conduit 24 as shown on Fig. l. A third chamber 25, separated from chamber I9 by a rib 21. is connected to the sump by a pipe 31. The chamber 25 is of about twice the length of chambers 26 and I9 to permit it to be connected either to chamber i9 or to the next chamber 28 from which it is separated by a rib 23. This latter chamber is connected by a pipe 30 to the casing of a throttle valve 3| which may be of any desired type but is preferably formed as a rotating cylinder having a helical groove as is fully set forth in my copending application Serial No. 381,780

4iiled Mar. 5, 1941. A conduit 32 leads from this throttle to the four-way valve 23 (Fig. 1) and a pipe .33 from that valve to the second end of the cylinder. As previously stated, the cycle inverter 23 has been omitted from Figs. 4 to 7 for clearness, the pipe 32 being shown coupled directly to the cylinder 22. A fth chamber 34, separated from chamber 28 by a rib 35, is coupled by a conduit 36 with the conduit 32 previously mentioned.

'I'he spool valve I8 has a head 38 at one end positioned adjacent the end 33 of casing Il so as to form a chamber 4|! into which pressure fluid may be introduced to shift the spool as will be described below. Next to this is an annular channel 4| positioned so as not to make connection with any of the chambers except in the reversing position 0f the spool. Separated from channel 4| by a rib 42 is a channel 43 of substantially greater length. A wide rib 44 then intervenes, being followed by channels 45 and 4B which in most positions of the valve act as a single channel of considerable length, but which for certain purposes are separated into two channels by a rib 41.

Cylinder 22 is preferably stationary in order to avoid the necessity of making hydraulic connections to a moving cylinder, the rod of its piston 5| being connected to the reciprocating table I8 is set to cause the pressure fluid to enter at the right of the piston and the liquid from the left of the piston is forced out directly tothe sum Tllijere is no provision made in the spool valve for motion at a feed rate during the return stroke of the table, as the elimination of this extra capability greatly reduces the complexity of the spool yalve mechanism. To allow the cycle to be inverted the four-way valve 23 is provided. It should be understood that this valve does not act as a reversing valve during normal operation of the machine, the spool valve I8 performing this function. The four-way valve is used only when it is desired to have the cycle of operation start from the other end. of the table (compare Figs. 2 and 3), and can be `built into the base of the machine in a relatively inaccessible position where it will not complicate the controls which are used during normal operation.

The several operative positions of the spool valve are shown in Figs. 4 to 7 inclusive. Fig. 4 shows the valve in position to cause rapid traverse movement in a forward direction. In this and succeeding figures the cycle inverting valve has been omitted, as it merely changes the direction of movement of the table without affecting in any way the operation of the remaining parts. To obtain rapid forward movement the spool valve I8 is located in its position nearest to the head 39 of the casing I1. In this position channel 43 joins the chambers 26 and I9, thus connecting the pipes I4 and 2| and admitting fluid under pressure to the left hand end of the cylinder 22. Channels 45 and 46 in this case act as a single long channel joining the chambers 25, 28, and 34, the rib 41 lying within the chamber 28 and being ineffective as a dividing Wall. It should be noted that the return line from cylinder 22 in theory branches from pipe 32 either through pipe 36 or through the throttle 3l, uniting again in the valve casing and extending to the sump through the line 31. The amount of ow through the throttle is in this case negligible and unimportant since the direct path through pipe 86 offers so much less resistance. The use of the two lines in parallel, however, is of advantage as it simplifies the valve construction.

In Fig. 5 the pressure uid line to. the cylinder is left unchanged, but the rib 41 is moved into line with the rib 35 so as to shut oi the chamber 34 and force all the liquid through the throttle 3l. The table will in this case be moved forwardly at a speed determined by the setting of the throttle;` which, if the throttle is constructed in accordance with my application Serial No. 381,780 can be regulated with great accuracy.

In Fig. 6 the spool has been moved one step further to the right, so that the conduits I4 and 31 are directly connected together. The pressure fluid is thus vented directly to the sump, and no movement of the table takes place.

The final position is shown in Fig. 'l and shows the spool moved to its right hand position. giving a reverse motion to the table at high speed. The rib 42 has here been brought adjacent the ri-b 20, shutting off chamber 26 from chamber I9 and retaining the pressure fluid within the chamber 4I, which for the first time comes into separate operation. This chamber is connected with. chamber 45 by a duct 55 extending within and centrally of the spool. Through this duct pressure fluid passes into the joint chambers 28 and 34 and thence to the right hand end of the cylinder through conduits 36 and 32. Here again the throttle is ineffective on account of the lower resistance of the other path, and the liquid passes freely to the cylinder. Liquid forced out from the other end of the cylinder is passed through `the chambers I9 and 25 to the discharge line 31.

For manual control of the spool valve the spool is provided with an integral rack 56 (Fig. 4) meshing with a wide gear 51. A second rack 58 also meshes with this gear, and at its upper end carries a, roll 59 engaged by suitable dogs 66 on the table. By suitably proportioning the dogs the spool may be shifted between its feed and rapid traverse advance positions, or from either of these positions tothe stop position. The spool is centralized and releasably held in any of its positions by a spring pressed detent 6I engaging notches 62 in the spool.

The mechanical shifting mechanism described is capable of changing the speed of and stopping the table, but it cannot cause reversal because in order to place the spool in its reversing position it is necessary to pass through its stopping position. Once the table is stopped there is of course no movement of the dogs to cause further shifting of the spool. To shift the spool into reversing position pressure fluid is introduced into chamber 40 through a pipe 63 under the control of a spool valve 64 in a, casing 65. The casing has three spaced chambers 66, 61, and 68 connected respectively to a line `95 leading to the pressure line I4, the pipe 63', and a line 69 leading to the sump. The spool has two recesses'10 and 1I which, when the spool is in its normal vposition of Fig. 4, straddle the chambers 61 and 68 and keep the chamber 40 connected to the sump. When the valve is depressed as in Fig. 7 the recesses 10 and 1I straddle the chambers 66 and 61 and admit pressure fluid from line I4 to chamber 40, causing the spool valve I8 to be shifted all the way to the right without pausing at the stop position. The spool 64 is returned to normal by a spring 12 as soon as the reversing dog 13 on the table has left the stem 14 of the valve. As shown in Fig. l, the operating stems 58 and 14 of the two spool valves are located near the center of travel of the table (preferably closer together than shown) and may -be actuated by dogs lying in different planes to avoid interference.

The normal cycle of the machine is rapid advance to the neighborhood of the work, then slow advance at a rate determined by the throttle setting. a rapid return, and stoppage. The starting is brought about by manual shifting of spool valve I8 by a handle 15 on gear 51. The spool is shifted from rapid traverse to feed position by a dog 60, and then is shifted to its rapid traverse reverse position hydraulically by the shifting of spool 64 by dog 13. Stoppage at the initial position of the table is brought about by a dog 16 having the usual ledge to underlie roll 59 and raise plunger 58 to move spool I8 from the position of Fig. '1 to that of Fig. 6. If it is desired to have the feed in the opposite direction the cycle inverting valve 23 is manually changed, whereupon the automatic cycling control proceeds as before but with the directions reversed.

If it is desired to use the circuit described for throwing out the spindle control clutch of the machine tool while the table is traveling at rapid traverse, this is preferably done by a servo-motor acting on the clutch 82 through any suitable linkage 83. The servo-motor is supplied with fluid by a sequence valve 84 inserted in the line 2l and shown in detail in Fig. 8. This valve may be of various forms, that shownbeing illustrative and diagrammatic only. Basically it consists of a casing B into which the line 2| opens on opposite sides. A piston valve 86 slides within the casing, and is normally held at one end thereof by a spring 81. A'central constriction 88 in the valve .permits fluid to flow freely at all times between the two branches of the line 2|. When the valve I8 is set to cause rapid traverse movement of the table in either direction, the throttle 3| is Icy-passed, and there is` but slight resistance to the passage of vfluid through line 2|. When the spool valve is shifted to its feed rate position, however, the fluid exhausted from the cylinder 22 has to pass through the throttle, and the pressure in the line 2| rises sharply. As this occurs the valve 86 will be shifted against the action of its spring by fluid passing through a duct 89, causing the piston to uncover a port 90 connected to the servo-motor by a line 9|'. As long as the main valve is set at feed rate the spindle clutch will remain in engagement, returning to inactive position as soon as the circuit is shifted to stop or to rapid traverse in either direction. A check valve 92 permits the fluid in the servo-motor to drain back to the line as soon as the pressure in the latter drops.

It is sometimes desirable to operate a workclamp hydraulically. Such a clamp is shown conventionally in Fig.,l, operated by a servomotor et having conduits 91, 93 leading through a four-way valve 99 to the line 95 and to the sump. By shifting the valve manually or automatically the clamp may be placed in either active or inactive position. To free the clamp servomotor from the sudden drop in pressure resulting when the circuit is in stop or rapid traverse condition, it is preferable to place a loading Valve |00 in the line i4, and to take oil the line S5 between it and the pump. This loading valve may be of any desired construction, and operates to keep a pressure of say 50 lbs. per square inch at all times in the line 95. On the feed stroke the pressure may rise to that for which the relief valve I3 is setl (say 200 lbs.), but can never fall below the pressure determined by the loading valve.

What I claim is:

l. A hydraulic circuit for causing reciprocatory motion of a machine element comprising a cylinder` and a piston one of which is stationary and the other connected to said element, a sump, a source of liquid under pressure, and means for controlling the flow of liquid to and fromV the cylinder comprising a spool valve and a cooperating valve casing, said casing having in sequential relation a pressure fluid inlet, a connection to one -end of the cylinder, a connection to the sump, a connection through a throttle to the second end of the cylinder, and a connection around the throttle valve to said second end of the cylinder, the valve casing and spool being relatively so formed that with the `valve at one extreme position the fluid inlet is coupled to the first end of the cylinder and shut off from the sump and the second end of the cylinder is connected directly to the sump, in a second position the uid inlet connection is unchanged and the i second end of the cylinder is connected to the sump through the throttle valve only, in a third position the fluid inlet is connected to the sump, and in a fourth position the uid inlet is connected directly to the second end of the cylinder and the rst end of the cylinder is connected to the sump.

2. A hydraulic circuit for causing reciprocatory motion of a machine element comprising a cylinder and a piston one of which is stationary and the other connected to said element, a sump, a source of liquid under pressure, and means for controlling the ow of liquid to andfrom the cylinder comprising aspool valve and a cooperating valve casing, said casing having in se-v quential relation a pressure uid inlet, a connection to one end of the cylinder, a connection to the sump, a connection through a throttle to the second end of the cylinder, and a connection around the throttle valve to said second end of the cylinder, the valve spool being providedwith a circumferential depression of sufficient length to straddle the rst three of said connections, a second circumferential depression of sufficient length and suitably positioned to straddle the last three of said connections when the spool is in either one of two positions in which the first depression straddles the first two connections only, a barrier in said second depression positioned to separate the last twoconnections when the spool is in one of said latter positions, and a third depression connected internally of the spool with the second depression and positioned to connect with the first connection when the spool is in position for the rst depression to couple the second and third connections only.

3. A hydraulic circuit for causing reciprocatory motion of a machine element comprising a cylinder and a piston one of which is stationary and the other connected to said element, a sump, a source of liquid under pressure, and means for controlling the flow of liquid to and from the cylinder comprising a spool valve and a cooperating valve casing, said casing having in sequential relation a pressure fluid inlet, a connection to one end of the cylinder, a connection to the sump, a connection through a throttle to the second end of the cylinder, and a connection around the throttle valve to said second end of the cylinder, the valve casing and spool-being relatively so formed that with the valve yat one extreme position the fluid inlet is coupled to the first end ofthe cylinder and shut off from the sump and the second end of the cylinder is connected directly to the sump, in a second position the fluid inlet connection is unchanged and the second end of the cylinder is connected to the sump through the throttle valve only, in a third position the fluid inlet is connected to the sump, and in a fourth position the fluid inlet is connected directly to the second end of the cylinder and the rst end of the cylinder' is connected to the sump, mechanical means for shifting the spool into any of said positions, and hydraulic meansfor shifting the spool into said fourth position.

d. A hydraulic circuit for causing reciprocatory motion of a machine element comprising a cylinder and a piston one of which is stationary and the other connected to said element, a sump, a source of liquid under pressure, and means for controlling the flow of liquid to and from the cylinder comprising a spool valve and a cooperating valve casing, said casing having in sequential relation a pressure fluid inlet, a connection to one end of the cylinder, a connection to the sump, a connection through a throttle to the second end of the cylinder, and a connection around the throttle valve to said second end of the cylinder, the valve spool being provided With a circumferential depression of sufcient length to straddle the first three of said connections, a, second circumferential depression of suillcient length and suitably positioned to straddle the last three of said connections when the spool is in either one of two positions in which the ilrst depression straddles the first two connections only, a barrier in said second depression positioned to separate the last two connections when the spool is in one of said latter positions, and a third depression connected internally ofthe spool with the second depression and positioned to connect with the rst connection when the spool is in position for the ilrst depression to couple the second and third connections only, mechanical means for shifting the spool into any of said positions, and hydraulic means for shifting the spool into said fourth position.

5. A hydraulic circuit for causing reciprocatory motion of a machine element comprising a cylinder and a piston one of which is stationary and the other of which is connected to said Aelement, a source lof liquid under pressure, a sump, a throttle, a valve casing having in the order named a first port connected to the source, a second port connected to one end of the cylinder, a third port connected to the sump, a fourth port connected to the second end of the cylinder through the throttle, and a fifth port connected to the second end of the cylinder exclusive of the throttle, and a spool valve within the casing having a groove connecting theA second port alternatively with the first and third ports or with both together, a second groove connecting the third port with the fourth and fifth ports, said second groove having an intermediate circumferential rib separating the fourth and fth ports in lone position of the spool, and a third groove connected by an internal bore with the second groove and alignable with the first port.

6. A hydraulic circuit for causing reciprocatory motion of a machine element comprising a cylinder and a piston one of which is stationary and the other of which is connected to said element, a source of liquid under pressure, a sump. a throttle, a valve casing having in the order named a first port connected to the source, a second port connected to one end of the cylinder, a third port connected to the sump, a fourth port connected to the second end of the cylinder through the throttle, and a flfth port connected to the second end of the cylinder exclusive of the throttle, and a spool valve within the casing having a groove connecting the second port alternatively with the ilrst and third ports or with both together, a second groove connecting the third port with the fourth and fifth ports, said second groove having an intermediate circumferential rib separating the fourth and fifth ports in one position of the spool, a third groove connected by an internal bore with the second groove and alignable with the first port, mechanical means engaging one end of the valve to shift it, and hydraulic means engaging the other end of the valve to shift it in one direction.

7. A hydraulic circuit for causing reciprocasing having first, second. third and fourth depressions separated by portions adapted to engage the separations between ports, the second and third depressions being each of a length to straddle a pair of adjacent ports and the separation between the second and third depressions being substantially wider than that between the first and second and third and fourth depressions, a connection through the body of the spool valve from the first to the third depression. and conduits leading from a fluid pressure source to the flrst port, from the second port to one end of the cylinder, from the third port to the sump, from the fourth port through the throttle to the other end of the cylinder, and from the fifth port directly to said other end of the cylinder.

8. A hydraulic circuit for causing reciprocatory motion of a machine element comprising a cylinder and piston one of which is stationary and the other connected to said element, a source of fluid under pressure, a sump, a throttle, and means for controllingthe flow of fluid to and from the cylinder comprising a spool valve casing having first, second, third, fourth and flfth ports sequentially arranged, the third port being substantially wider than the first, second and fourth ports, and the several ports being separated one from the next, a spool valve within the casing having first, second, third and fourth depressions separated by portions adapted to engage the separations between ports, the second and third depressions being each of a length to straddle a pair of adjacent ports and the separation between the second and third depressions being substantially wider than that between the first and second and third and fourth depressions, a connection through the body of the spool valve from the first to the third depression, and conduits leading from a fluid pressure source to the first port, from the second port to one end of the cylinderl from the third port to the sump, from the fourth port through the throttle to the other end of the cylinder, and from the fifth port directly to said other end of the cylinder, mechanical means for varying the position of the spool valve, a conduit leading to the end of the spool valve adjacent the first depression, and a valve connecting said end either to the pressure fluid source or to the sump.

9. A hydraulic circuit for causing reciprocatory motion of a machine element comprising a cylinder, and piston one of which is stationary and the other connected to said element, a source of fluid under pressure, a sump, a throttle, and means for controlling the flow of fluid to and from the cylinder comprising a spool valve casing having first, second, third, fourth and fifth ports sequentially arranged, the third port being substantially wider than the flrst, second and fourth ports, and the several ports being separated one from the next, a spool valve within the casing having first, second, third and fourth depressions separated by portions adapted to engage the separations between ports, the second and third depressions being each of a length to straddle a pair of adjacent ports and the separation between the second and third depressions being substantially wider than that between the first and second and third and fourth depressions, a connection through the body of the spool valve from the first to the third depression, and conduits leading from a fluid pressure source to the ilrst port, from the second port to one end of the cylinder, from the third port to the sump, from the fourth port through the throttle to the other end of the cylinder, and from the fifth port directly to said other end of the cylinder, mechanical means for varying the position of the spool valve, a conduit leading to the end' o1' the spool valve adjacent the first depression, a valve connecting said end either to the pressure uid source or to the sump, andvspring means normally holding said last-named valve in a posi-4 tion connecting the end of the spool valve to the sump.

10. A hydraulically operated machine tool comprising a reciprocable element, a cylinder and a piston one of which is stationary and the other of which is connected to said element, a source of liquid under pressure, a. sump, a throttle, a valve including a casingand a recip- .rocable spool therein projecting from the casing at one end only, the casing and spool being relatively formed so that in one position, in which the spool extends a maximum distance into the casing, the source is connected to one end of the cylinder and the other end of the cylinder is connected directly to the sump, in'a second position the source is connected to one end of the cylinder and the 'other end of the cyunder is connected to the sump through the throttle, in a third position the source and sump are connected together, and in a fourth position, in which the spool extends a minimum distance into the casing, the source is connected to said other end of the cylinder and the first end thereof is connected to the sump, mechanical means for shifting the valve between said positions, a pilot valve normally in a position venting to the sump the space between the casing and the 4end of the spool, movable temporarily to a position admitting pressure fluid to said space to shift the iirstnamed valve into its fourth position, an operating rod for said pilot valve located at approximately the center of travel of said element, an operating rod for mechanical shifting of the spool located at approximately the center of travel of said element, dogs for actuating said rods independently, and a cycle reversing valve located between said spool valve and the cylinder.

FRANK W. CURTIS.

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