US1931452A - Hydraulic machine tool feed - Google Patents

Description

Oct. 17, 1933. (3 WHEELER 1,931,452

HYDRAULIC MACHINE TOOL FEED Filed Sept. 23, 1931 4 SheetS -Sheet 1 DOWN START 90 a INVENTOR: ii Maw Lia dG. W/zeezez Oct. 17, 1933. L. G. WHEELER HYDRAULIC MACHINE TOOL FEED 4 Sheets-Sheet 2 Filed Sept. 23, 1931 INVENTOR: LZo d 6? Wheeler,

Oct. 17, 1933. Y L. G. WHEELER ,4

HYDRAULIC MACHINE TOOL FEED Filed Sept. 25, 1931 4 Sheets-Sheet 3 WITNESSES INVENTOR:

1H0 d 6'. Weeler,

Patented Oct. 17, 1933 PATENT OFFICE HYDRAULIC MACHINE TOOL FEED Lloyd G. Wheeler, York, Pa., assignor to B. M.

Root (30., York, Pin, a corporation of Pennsyl- Vania Application September 23, 1931 Serial No. 564,608

13 Claims.

My invention relates to hydraulic or fluid feed for machine tools and the like, my object being to provide a simple, convenient, flexible, and reliable feed for such purposes. My invention is especially concerned with the control of the motive fluid to operate the feed as desired. I also aim to provide a simple and reliable anticreepage arrangement for a hydraulic motor subject to unbalanced load when not in operation. Various advantages that can be realized through the invention will appear from my description hereinafter of one preferred form of embodiment as applied to an upright wood-drilling machine.

In the drawings, Fig. I is a general perspective view of anupright wood-drilling machine equipped with one form of fluid feed embodying my invention.

Fig. II is a diagram of the fluid feed, with the hydraulic feeding motor and the hydraulic valve 29 mechanism in vertical midsection.

Fig. III shows a vertical section through the valve mechanism as preferably constructed in actual practice.

Fig. IV shows a horizontal section through the valve mechanism, taken as indicated by the line and arrows IVIV in Fig. III.

Fig. V is a fragmentary view, partly in vertical section, illustrating an operating adjustment different from that shown in Fig. I.

Fig. VI is a fragmentary plan view illustrating the provisions for preventing creepage in the hydraulic motor, whose cylinder appears in horizontal section.

Fig. VII is a corresponding side view, with a 35 portion of the cylinder in vertical section, and

with parts of the mechanism omitted.

As shown in Fig. I, the drilling machine here illustrated comprises an upright standard or column l0 rising from a base 11 and carrying a head or frame 12, which in the present instance carries the drills 13. The colunm 10 is provided with upright guideways 14 for a vertically movable carrier 15 which in the present instance carries the worktable 16. The drills 13 may be driven 5 by any suitable means, such as an electric motor 17 mounted on the frame 12 and connected by means indicated at 18 to a transverse shaft 19, itself connected by suitable means (not shown) to the drill spindles 20. The carriage 15 is moved up and down by a hydraulic motor 25, of cylinder and piston type. As shown in Figs. I and VII, the motor cylinder 26 is mounted on the base 11 adjacent the column 10, and its piston or plunger rod 27 extends upward to the carriage 15. to which it is attached in any suitable manner (not shown). Fluid under pressure to operate the motor 25 may be supplied from any suitable source, such as a rotary pump 28 driven through reduction gearing 29 by an (electric) motor 30 mounted on the base 11. In the present instance, there is a fluid reservoir tank 31 in the lower portion of the (hollow) standard or column 10, whose top is normally closed by a removable lid 32, accessible through an opening 33 in the column wall. The pump' 2:; draws liquid (oil) from the reservoir 31 through a suction pipe connection 35, and delivers it under pressure through a supply pipe connection 36, under control of valve means in a casing 37 mounted on one side of the column 10.

Referring, now, also to Figs. II and III, it will be seen that the valve casing 37 has chambers or bores 38, 39 for two valves 40, 41, operated by upright valve rods 42, 43 extending downward beside the column 10, and also, in the present instance, a chamber or bore 44 for a third valve 45, operated by fluid under control of the valve 41 as a pilot valve. As shown, valves 40, 41, 45 are of piston type. The valve 41 is in a broad sense an operating or distributing valve, since it controls the shifting of the valve 45, which is the operating or distributing valve in a stricter sense,directly admitting and venting or exhausting motive fluid to and from the motor 25 according to the desired direction of movement of the carriage 15. The valve 40 is a control or supply valve, controlling the flow or supply of motive fluid to the operating valve means 41, 45 according to whether the carriage 15 is to be moved or to remain stationary. In other words, the valve 40 is in an operating sense the actual, controlling means of supply of motive fluid for the motor 25. As here shown, it is a by-pass valve rather than a stop valve, permitting the motive fluid from the supply connection 36 to return directly to the reservoir 31 through a vent or return pipe connection 46 when the motor 25 is not operating. This allows an inelastic motive fluid (oil) to be used with a continuously running pump 28 as source of pressure without complications. There is also shown a spring-loaded relief valve 47 permitting escape of motive fluid from the casing 37 through a vent or return pipe 48, if excessive pressure tends to build up there for any reason.

The control valve 40 has a reduced portion or wide groove 50, and is longitudinally grooved at 51 (Fig. 111). It also has a transverse port 52 therethrough, which with the valve in the (upper) active position shown directly connects a sup- 110 ply port 53 (to which the supply pipe 36 is' con nected) to a supply port 54 through which pressure fluid has access to the valves 41, 45. When, however, the valve 40 is depressed to its (lowermost) inactive or neutral position, the top of the valve is exposed to the fluid from the supply port 53, which passes down through the grooves 51 and along the reduced portion 50 to a relief port 55 (to which the return pipe 46 is connected). Thus the effective pressure of the fluid is reduced, so that although it may still have access to the port 54, it is ineffective to operate the motor 25, even if admitted thereto. The grooves 51 equalize the pressures above and below the valve 40, so that it is substantially balanced and freely movable.

The stem-actuated operating valve 41 is hollow, and has reduced portions or wide annular grooves 56, 56a which serve to reduce friction with the bore 39. It also has annular grooves 57, 58, which are connected to its hollow interior by radial ports 59. Similar ports 59 connect the interior of the valve to the reduced zone at 56. As this groove 56 overlaps the port 54 in all positions of the valve, it follows that the interior of the valve and its external grooves 57, 58 (as well as the groove 56) always contain fluid, which is at the full supply pressure whenever the control valve 40 is in its active position here shown. The ends of the valve bore 39 are constantly vented through return connections 60, 60, so that the valve is substantially balanced.

The fluid-actuated operating valve proper, 45, is hollow, and has wide annular grooves or reduced portions 61, 62, and also annular grooves 63, 64. The grooves 62, 63, 64 are connected to the hollow interior of the valve by radial ports 65. The ends of the valve 45 are reduced, so that even in its extreme positions, the valve never covers the fluid admission and exhaust ports 66, 6'7, 68, 69 connecting the ends of the bore 44 with the ends of the bore 39. In all positions of the valve 45, its groove 61 overlaps a supply port '71 leading to the bore 39 about on a level with the supply port 54, so that the groove 61 always contains fluid at the pressure obtaining in the port 54. In all positions of the valve 45, also, its groove 62 overlaps an exhaust port '72 to which is connected a vent or return pipe '73, so that the interior of the valve and its external grooves 63, 64 are always in communication with the exhaust. As shown in Figs. I and IV, the effective area of the port '71 and the rate of feed of the table by the fluid pressure can be delicately regulated by means of a screw-operated throttle, choke, or needle valve '75.

When the valve 45 is in its extreme (lower) position shown in Fig. II, its exhaust groove 64 registers with a port '76 connected to the lower end of the motor cylinder 26 by a pipe '77, so that the carriage 15 may descend or feed downward; while when the valve is in its extreme (upper) position shown in Fig. III, its pressure supply groove 61 registers with the cylinder port 76, so that the carriage 15 may rise or feed upward. In the present instance, the motor 25 is double acting, and there is a port '78 connected to the upper end of the cylinder 26 by a pipe '79: this port coacts with the pressure supply and exhaust grooves 61 and 63, admitting pressure fluid to the upper end of the cylinder to assist in lowering the carriage 15, and exhausting fluid therefrom to allow it to be raised by fluid beneath.

It will be seen that as the pilot valve 41 is moved upward and approaches its position shown in Fig. II, it closes the (upper) exhaust port 68 and the (lower) admission port 67, and opens the (upper) admission port 66 and the (lower) exhaust port 69, thus admitting pressure above the valve 45 and permitting exhaust from below it, and throwing the valve 45 to the position of Fig. II. As the pilot valve 41 is moved downward and approaches its position shown in Fig. III, it closes the (lower) exhaust port 69 and the (upper) admission port 66, and opens the (lower) admission port 67 and the (upper) exhaust port 68, thus admitting pressure below the valve 45 and permitting exhaust from above it, and throwing the valve 45 to the position of Fig. III. How the valves 40 and 41 may be operated will be described hereinafter.

As shown, the relief valve 4'7 is a hollow piston in the bore of a casing part mounted at the upper end of the bore 38, with a port-81 open at one end into the supply groove 56 of the operating valve 41 in all positions of the latter, and at the other end open directly beneath the piston valve 4'7. The valve 47 is normally held against a conical shoulder 82 around the port 81 by a helical compression spring 83, whose lower end engages in: the upper end of the valve, and whose upper end engages around a shouldered abutment 84, sustained by an adjusting screw 85. In the wall of the casing 80 is an annular relief port 86 to which the return pipe 48 is connected, and the valve 47 has drainage holes 87 normally open from its interior to this port. When the valve 4'7 is down, as in Figs. II and III, it overlaps beyond the port 86 a substantial distance, so as to seal it effectually. The tension of the spring 83 and the pressure under which the valve 4'7 will open can be adjusted by means of the screw 85.

As shown in Fig. I, the valve rods 42, 43 extend down through a guide 89 on the lower end of the standard or column 10. For voluntary actuation of the rods 42, 43, at the will of the operator, there are double foot- pedals 90 and 91 at the front of the machine (in convenient reach of a workman standing by the work-table 16), mounted and arranged one in front of the other on horizontal shafts 92, 93 that are journalled in bearing brackets 94 on the base 11. The rear ends of the shafts 92, 93 have arms 95, 96 that are suitably engaged or connected with the lower ends of the rods 42, 43.

As shown, the carriage 15 carries an arm 9'! that extends rearward beside the column 10 and is adapted to coact with the rods 42, 43 to operate said rods and the control and operating valves 40, 41 automatically. For this purpose, the carriage arm 9'7 may embrace the rods 42, 43, and the latter may be provided with adjustable stops 98, 99, 100 to engage the arm near the extremes of the desired carriage stroke. For each of the stops 98 and 100, there is a helical compression spring 101 operatively interposed between the arm 97 and the corresponding rod 42 or 43, and mounted around the rod between a collar or washer 102 loose on the rod and a split screw-clamp collar 103 that can be set in any desired position on the rod. The stop 99 consists merely of a split screw-clamp collar. By suitably setting the stops 99, 100, the limits and length of the stroke of the carriage 15 can be varied exactly as desired within the range afforded by the dimensions of the motor 25. As shown, the arm 9'7 has a vertically adjustable collar 105 threaded in its split end, which may 150 be clamped tight on the collar 105 by a screw 106: this aifords a fine micrometer, adjustment of the upward limit of .carriage feed for the purpose of regulating the depth of holes bored in the work (not shown) on the table 16.

It may sometimes be desired to maintain the carriage 15 at a definite height while work is being set up on the table 16, or for other reasons. However, an operating or distribution valve is rarely so fluid-tight as to-prevent very slow leakage from the lower end of the cylinder 26 to exhaust; hence the carriage 15 tends to gradually sag or creep downward under its own (unbalanced) weight. To prevent such sagging, I prefer to provide a seal against fluid leakage, preferably by means of a valve 110 interposed in the pipe connection 77 between the lower end of the cylinder 26 and the operating valve 45. As shown in Figs. VI and VII, the sealing valve 110 is a bevel-ended piston valve in a transverse chamber or bore 111, in the lower portion of the cylinder structure 26, movable lengthwise of the bore 111 by a stem 112, and seating against a correspondingly bevelled shoulder 113. The cylinder induction and eduction pipe 77 is connected in front of the valve 110, so that pressure inthis pipe tends. to unseat the valve. The connecting port or passage 114 between the bottom of the cylinder 26 and the bore 111 is open into the bore at the rear of the valve 110 when seated, so that pressure from the cylinder 26 tends to hold the valve tight on its seat 113. However, when the valve 110 is drawn away from its seat 113, it travels across the port 114 and puts the latter in free communication with the pipe 77 in front of the valve.

As shown in Fig. VII, the valve 110 has one or more axially extending peripheral grooves 115, which afford communication between the front and rear of the valve as soon as it leaves its seat 113, but are sealed when the valve is seated, -being shallower than the width of the valve bevel and seat at 113. These grooves 115 not only prevent trapping of fluid behind the valve 110 when retracted, but also equalize the pressure between its two faces when the valve is unseated, so as to balance the valve somewhat.

When the valve 110 is seated, of course, its front area exposed to pressure is reduced substantially, according to the width of the seat. When the valve 110 is seated, the back pressure due to the carriage 15, etc., tends to keep the valve tightly sealed to its seat 113.

The sealing valve 110 must, of course, be open (for admission or exhaust) whenever the table elevating motor 25 operates: i. e., under the same conditions for which the control valve 40 need be in its active position of Figs. II and III. At all other times, it may, like the valve 40, be closed. I have provided for operating the valve 110 with the valve 40, by the same pedal device 90, by connecting the valve 110 to the shaft 92. For this purpose, there is a rocker 116, mounted (for convenience) to turn loosely on the shaft 93 as a pivot, preferably slotted at 117 to accommodate the shaft 92 and swing relative thereto, and operatively connected to the valve stem 112 by a pivoted link 118. The rocker 116 is operatively connected to the shaft 92, to be operated there- ,by, by a spur gear connection, comprising a gear segment 119 fast on the shaft 92 and meshing with a corresponding gear segment 120 on the rocker 116, coaxial with the shaft 93. As shown in Figs. VI and VII, the rocker 116, consists, in effect, of a pair of plates united at their upper ends by the interposed gear 120,the gear 119 intervening loosely between their lower portions.

The general operation of the hydraulic feed mechanism may be briefly described as follows: In Fig. I, the stop 98 is shown so set relative to the stop 100 as never to be struck by the car- .riage arm 97; which adapts the machine for continuous operation, automatically feeding the carriage 15 up and down indefinitely. The pedal device is in its inactive position, with the control valve 40 closed; the pedal device 91 is in mid-position (though in practice rarely so set by the operator); and the carriage 15 is at rest about at mid-stroke.

In putting the feed into continuous operation, the operator first presses down one of the up" and down pedals of the device 91, according to the direction in which he wishes the carriage 15 to start,thus throwing the pilot valve 41 to the proper end of its stroke. He then presses down the start pedal of the device 90, thus throwing the control valve 40 to its active position (Figs. 11 and III) and admitting fluid pressure through the operating valve 45 to the proper end of the cylinder 26. Assuming that the up pedal was depressed, the carriage 15 starts and travels upward until the arm 97 (or its collar 105) strikes the stop 99 and throws the pilot valve 41 to the other end of its stroke, thus throwing the valve 45 and reversing the travel of the carriage. When the downward moving arm 97 strikes the stop 100, the movement of the carriage 15 is again reversed-and so on indefinitely; until the operator stops the feed by pressing down the stop pedal of the device 90.

By setting the stop 98 in about the position of Fig. V relative to the stop 100, so as to be struck by the downward moving arm 97, the machine is adapted to intermittent double-stroke or up, down, and stop operation. With this setting of the stop 98, the feed is put in operation just as before; but when the arm 97 strikes the stop 98, it throws the control valve 40 to its (lowermost) inactive position about as the pilot valve 41 is shifted to its position for upward carriage movement,thus stopping the feed. To make the next double stroke, it is only necessary to press down the start pedal and hold it down momentarily, thus compressing the stop spring 101, throwing the control valve 40 to its active position, and restarting the carriage 15 upward. v For a substantially constant rate of feed of the inelastic motive fluid (oil) by the pump 28, as usual in machine tool feeds, the carriage 15 will return downward more rapidly than it travels upward, because the piston displacement above is much less than that below, owing to the large piston rod 27,-even though the pressure of the oil in the system may be greater on the upstroke, when the piston is working against the weight of the table 16, etc., and sometimes also against the resistance of the work to cutting. The general rate of feed of the carriage can be varied and regulated by means of the hand vavle 75, as already explained. The rate of feed when cutting is slower than in approaching the work, however, owing to the slip in the rotary pump 28. By pressure on the stop pedal of the device 90, the feed can be stopped instantly at any point of travel up or down; and the carriage 15 will remain indefinitely wherever stopped. By pressure on one of the up and down pedals of the device 91, the carriage 15 can be instantly reversed at any point of its movement either way.

No harm results from jamming of the carriage 15, since this merely causes-the relief valve47 to open.

The use of a fluid-actuated operating valve (45) controlled by a pilot valve (41) affords this advantage over a single mechanically actuated operating valve: that the motor 25 thus equipped cannot be stalled with the operating valve fluid-locked on dead center (covering both exhaust ports, for example), since by voluntary movement of the pilot valve 41 the operating valve 45 can always be thrown to one end of its stroke. However, such a pilot control arrangement is not essential to my invention in its broader aspects.

Having thus described my invention, I claim:-

1. A machine tool of the character described, comprising a base and a'standard with a motive fluid reservoir in said standard; a carriage in front of said standard movable up and down along it; a fluid motor for moving said carriage as aforesaid; a motive fluid pump drawing from said reservoir and delivering to said fluid motor and a driving motor for said pump, to the rear of said standard; valve casing means on one side of said standard receiving motive fluid from said pump and discharging spent motive fluid to said reservoir; operating valve means in said casingmeans for admitting and venting motive fluid to and from said motor according to its desired direction of movement; control valve means in said casing for controlling the flow of the motive fluid to said operating valve means according to whether operation of said motor is desired or not; valve actuating rods extending downward from said operating and control valve means and movable up and down along said standard; horizontal shafts mounted on said base, operatively connected to said rods beside said standard and extending forward under said carriage, and there provided with foot pedals for independently actuating said rods at the will of an operator; and means projecting rearward from said carriage beside said standard forcooperating with said rods to shift said operating'and control valve means automatically.

2. A machine tool of the character described, comprising a standard, a carriage movable up and down along said standard, and a fluid motor for moving said carriage as aforesaid; in combination with operating valve means for admitting and venting motive fluid to and from said motor according to its desired direction of movement; control valve means for controlling the flow of motive fluid for said motor to said operating valve means according to whether operation of said motor is desired or not; upright operating rods for said operating and said control valve means movable up and down along said standard; and horizontal rock shafts operatively connected to said rods beside said standard, and extending forward under said carriage and there provided with double foot pedals, one in front of the other, for independently shifting said rods and valve means at the will of an operator.

3. A machine tool of the character described, comprising a standard with a base, a carriage movable up and down along said standard, and a fluid motor for moving said carriage as aforesaid; in combination with valve casing-means on one side of said standard at a distance above its bottom exceeding the range of movement of said carriage; operating valve means in said casing-means for admitting and venting motive fluid to and from said motor according to its desired direction of movement; control valve means in said casing-means for controlling the flow of motive fluid to said operating valve means according to whether operation of said motor is desired or not; valve operating rods extending downward from said operating and control valve means and movable up and down along said standard; horizontal actuating shafts mounted on said base and operatively connected to said rods beside said standard, and extending forward under said carriage and there provided with foot pedals for independently shifting said rods and their valve means at .the will of an operator; and means projecting from said carriage beside said standard and cooperating with said valve operating rods, between their connections to said horizontal shaft and said casingmeans, to shift the valve means automatically at extremes of movement of said carriage.

4. A machine tool of the character described, comprising a standard, a carriage movable up and down along said standard, and a. fluid motor for moving said carriage as aforesaid; in combination with valve casing-means on one side of said standard at a distance above its bottom exceeding the range of movement of said carriage; operating valve means movable up and down in said casing-means for admitting and venting motive fluid to and from said motor according to its desired direction of movement; control valve means movable up and down in said casing-means for controlling the flow of motive fluid to said operating valve means according to Whether operation of said motor is desired or not; valve stems extending downward from said operating and control valve means a distance exceeding the range of movement of said carriage, and movable up and down along said standard; horizontal actuating shafts operatively connected to said valve stems beside said standard, and extending forward to an operator in front of the carriage, for independent operation to shift said stems and valve means at the will of the operator; and means projecting from said carriage beside said standard and cooperating with said valve stems, below said casing-means, to shift the valve means automatically at extremes of movement of said carriage.

5. A machine tool of the character described, comprising a standard, a carriage movable up and down along said standard, and a fluid motor for moving said carriage as aforesaid; in com bination with valve casing-means on one side of said standard at a distance above its bottom exceeding the range of movement of said carriage; operating valve means movable up and down in said casing-means for admitting and venting motive fluid to and from said motor according to its desired direction of movement; control valve means movable up and down in said casing-means for controlling the flow of motive fluid to said operating valve means according to whether operation of said motor is desired or not; valve stems extending downward from said operating and control valve means a distance exceeding the range of movement of said carriage, and movable up and down along said standard; and means projecting from said carriage beside said standardand cooperating with said valve stems, below said casing-means, to shift the valve means automatically at extremes of movement of said carriage.

6. A machine tool of the character described, comprising a standard, a carriage movable up and down along said standard, and a fluid motorcomprising a standard, a carriage movable up for moving. said carriage as aforesaid; in combination with operating valve means for said motor including fluid-actuated operating valve means proper forsdmitting and venting motive fluid to and from said motor according to its desired direction of movement, and pilotvalve means controlling the movement of said operating valve means proper; by-pass valve means controlling the flow of motive fluid for said motor to said operating valve means according to whether operation of said motor is desired or not; upright operating rods for said pilot valve means and said by-pass valve means movable-up and down along said standard; means for independ ently shifting said rods at the will of an operator to operate said pilot and by-pass valve means; and means projecting from said carriage beside said standards cooperating with said operating rods to automatically shift them, and. thereby operate the valve means, at the extremes of movement of said carriage.

7. A machine tool of-the character described, comprising a standard, and a carriage movable up and down along said standard; in combination with a double-acting fluid motor for moving said carriage as aforesaid, having a differential piston with its greater area for raising the carriage, so as to give a slow rise and a quick descent for a constant rateof supply of motive fluid; operating valve means for admitting and venting motive fluid to and from opposite sides of the motor piston according to the desired direction of carriage movement; control valve means .for controlling the flow of motive fluid to said operating valve means according to whether operation of said motor is desired or not; upright operating rods for said operating and control valve means movable up and down along said standard; means for independently operating said rods at the will of an operator; an arm projecting from said carriage beside said standard for cooperating with said rods to shift said valve means automatically; and spring yielding stop devices on said rods for engaging said arm at the extreme of the downward movement of the carriage, to absorb its downward momentum and permit subsequent upward voluntary movement of the rods.

8. A machine tool of the character described, comprising a standard, and a carriage movable up and down along said standard; in combination with a double-acting fluid motor for moving said carriage as aforesaid, having a differential piston with its greater area for raising the carriage, so as to give a slow rise and a quick descent for a constant rate of supply of motive fluid; operating valve means for admitting and venting motive fluid to and from opposite sides of the motor piston according to the desired direction of carriage movement; control valve means for controlling the flow of motive fluid to said operating valve means according to whether operation 'of said motor is desired or not; upright operating rods for said operating and control valve'means movable up and down along said standard; means for independently operating said rods at the will of an operator; an arm projecting from said carriage beside saidstandard for cooperating with said rods to shift said valve means automatically; and sealing valve means interposed between said motor and said operating valve means and positively closed whensaid control valve means is operated to interrupt supply of fluid to said operating valve means.

9. A machine tool of the character described,

and down along said standard, and a fluid motor for said carriage supporting the same unbalanced, in combination with operating valve means for admitting and venting motive fluid to and from said motor according to its desired 7 direction of movement, means for controlling supply of motive pressure fluid to said operating valve means according to whether operation of said motor is desired or not, sealing valve means interposed between said motor and said operating valve means andurged to seat by back pressure from the motor, and means connected to said supply controlling means for opening said sealing valve means when said means is operated to supply fluid as a aforesaid and permitting it to close when said controlling means interrupts such supply.

10. A machine tool of the character described, comprising a standard, a carriage movable up and down along said standard, and a fluid motor for said carriage supporting the same unbalanced, in combination with operating valve means for admitting and venting motive fluid to and from said motor according to its desired direction of movement, means for controlling supply of motive pressure fluid to said operating valve means according to whether operation of said motor is desired or not, sealing valve means interposed between said motor and said operating valve means, and means for positively opening said sealing valve means when said controlling means is operated to supply fluid as aforesaid, and permitting it to close when said controlling means interrupts such supply.

11. A'machine tool of the character described comprising a standard, a carriage movable up and down along said standard, and a fluid motor for said carriage supporting the same unbalanced, in combination with operating valve means for admitting and venting motive fluid to and from said motor according to its desired direction of movement, valve means for controlling the' supply of motive pressure fluid to said operating valve means according to Whether operation of said motor is desired or not, sealing valve means interposed between said motor and said operating valve means and urged to seat by back pressure from the motor, means for operating said controlling valve means, and means for opening said sealing valve means actuated by said control valve operating means.

12. A machine tool of the character described, comprising a standard, a carriage movable up and. down along said standard, and a fluid motor for moving said carriage as aforesaid, in combination with operating valve means for said motor and control valve means for controlling the flow of motive fluid for said motor to said operating valve means, upright operating rods for said valve means associated with said standard, sealing valve means interposed between said operating valve means and said motor, horizontal shafts operatively connected to said rods and arranged one above another, a rocker pivoted on the upper-shaft and connected to said sealing valve means, and gearing operatively connecting the lower shaft to said rocker.

13. A machine tool of the character described, comprising a standard, a carriage movable up and down alongsaid standard. and a fluid motor for moving said carriage as aforesaid; in combination with operating valve means for admitting and venting motive fluid to and from saidmotor according to its desired direction of movement;

by-pass valve means controlling the flow of motive fluid for said motor to said operating valve means according to whether operation of said between said by-pass valve means and said motor, so as to be brought into action, normally, only when said by-pass valve means permits flow of fluid to said motor.

LLOYD G. WHEELER.

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