US1905132A - Control for hydraulic feeding mechanism - Google Patents

Description

April 25, 1933. B, s. T. BISHOP UAL Y 1,905,132

CONTROL FOR HYDRULIC FEEDINGr MECHANISM Filed De c. 21, 1927 Patented Vljan'- 25 1933" UNITED STATES PATENT ol-"Flcr:I l

BENJAIIN B. T. BISHOP, 0F BHBEWSBUBY, .AND ERIC J. mvONEN, O' WOEIBESTEB, IABSACHUSETTS, ABSIGNORS TO LELAND-GIFIOBD COMPANY, A CORPORATION. 0I

n ssacnusnrrs l CONTROL FOB HYDRAULIC FEEDING MEUHANIBI p Application led December 21, 1927. Serial No. 241,894.

This invention relates to a hydraulic feed for operating a piston and a work table or tool in the machine tool industry. These hydraulic feeds ordinarily are operated by oil and that is the intention in this case, a1- though other iiuids can be employed.

The principal objects of this invention are to provide means controlled by the back pressure for directly controlling the flow of pressure fluid to the pressure side of the piston on the working stroke; to provide improved means for controlling the speed of the work table at the time when the cutter or drill passes beyond the surface of metal on which it is operating, or at any other time when, for any reason, the resistance of the Work against the tool is reduced; and to provide an improved mechanism for keeping the speed of the feed constant under such varying conditions as have been mentioned.

The resistance offered to the feeding of a cutting tool in engagement with the work is variable due to irregular thickness of the cut taken and of the variable density of the material operated upon. This variable resistance imposes variable stresses upon the parts of the mechanism and is such that when the cutter passes from a highresistance to a low resist-ance section and the stresses on the parts of the mechanism are released, the parts suddenly spring forward resulting in the Jumping of the tool or the work, as the case may be. This jumper action is particularly true of hydraulically actuated feeding mechanisms due to the compressibility of the liquid or the elasticity of the parts associatedv therewith. Thus it is an object of the presentinvention to provide means that shall prevent such uncontrolled or jumping movement of the cutting tool or the work. To this end I employ a feeding mechanism for the tool or the work, as the case .may be, actuatedby a hydraulic cylinder and a piston, the arrangement being such that a high pressure liquid is applied on one side of the cylinder to advance the work and the tool in engagement, and the piston is forced against an entrapped body of liquid contained in the cylinder on the other side of the piston. The piston is thus positively confined between the high pressure liquid and the entrapped body of liquid and so can not jump forwardly upon a suddenly reduced cutting resistance as1 it is restrained from such movement by thev entrapped body of-liquid. The liquid -is allowed to escape from said entrapped liquid body at a slow rate that can be varied at will so that the rate of advance of the piston 1s governed not by the cutting resistance but by the rate of escape of liquid from the entra ped liquid body. The' entrapped liquid bo y thus constitutes a slowly retreating abutment or restraint which governs the advancing movement of the piston. Such an apparatus and such method of controlling the advance of the feeding mechanism consti- Entes another object of the present invenion.

The pressure applied on the entrapped liquid body through the piston is always intended to be greater than the cutting resistance so that the liquid body is under constant pressure during the advance of the piston although the amount of pressure varies in accordance with the cutting resistance. Since the rate pf escape of `liquid from the v entrapped llquid body depends upon the pressure thereof and thus the rate of advance of the piston would vary withvvariations in cutting resistance, and since it is desired that the rate of advance shall beconstant regardless of variations of cutting resistance, it is a further object of this invention to provide mechanism for maintaining a constant rate o f advance of the piston regardless of variat1ons of the cutting resistance thereon.

,In carrying o-ut this feature of the inveni tion I provide valve means to control the rate of admission of the high pressure liquid into the cylinder on the other side of the piston, said valve means being subjected to variations of pressure of the entrapped liquid body in such a manner that a high pressure tends to close the valve and admit high pressure liquid at a lower rate on the .other side of the piston, and vice versa,"thereby tending'to maintain a constant rate ofadvance of the piston and the feeding mechanism regardless of variations of cutting resistance.

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Such an arrangement constitutes a yet further object of the invention.

Other objects and advantages of the invention will appear hereinafter.

Reference is to be had to the accompanying drawing in which Fig. 1 is a diametrical sectional view of the pressure cylinder of a hydraulic feed with a preferred embodiment of our controlling device applied thereto and shown in position to allow full force of the pressure uid to enter the cylinder, and

Fig. 2 is a similar view showing the controlling device as havin moved for the purpose of restricting the gow of pressure fluid to the high pressure side of the cylinder and preventing the speeding up of the piston.

, This invention is adapted to be applied to milling machines, drills and various other machine tools. It is not shown as connected with such a tool, but it will be understoodl that a movable work table, if it is used for that type of machine, or movable tool, is connected with the piston rod 10 which is operated by the piston 11 located in a cylinder 9. The oil for operating the piston cornes into a passage 12 in a casing 13. In this casing is a cylindrical passage in which operates a reversing valve stem 14 having two valves 15 and 16 thereon of well-known construction and for the usual purpose. The valve stem 14 can be operated either manually or automatically, so no means is shown for operating it.

The piston 11 is reversed by the movement of the valve stem 14 further to the left than in Fig. 2. The valve 15 closes the port 17 and the valve 16 opens iirst the passage 32 and then the passage 26. Then pressure is introduced into the left' end of the cylinder 9, through the passage 25 and, previously, behind the valve 18, in the space 22 through the passage 31. Thus the oil at the right of the piston 11 is free to escape through 19.

1n the positionshown in Fig. 1, the oil under pressure comes from the passage 12 and is free to be discharged through a passage 17 toward the high pressure side of the piston. The passage of the power Huid to the cylinder is controlled by a hollow regulating valve 18 having an inlet from the passage 17 and an outlet 19 into the end of the cylinder. This valve is provided with two sets of perforations located in a circumferential ring, one set normally receiving liquid from the passage 17 and the other discharging it into the outlet 19. This valve is located in a recess in which is a spring 20 normally forcing the valve up against a stop'21 at the end into the position shown in Fig. 1. This is the normal position. The valve casing has a passage 22 at its end opposite the spring closed by a plug 23 lwhich can be removed. The oil or other non-compressible fluid flows out on the return stroke through the port 19 and plassage 17 and to the right of the valve 1.5.w ich at that time is in its left-hand po sition. The oil at this time is open to the at- ;noslphere and flows back into the supply The oil from the other side of the piston 1s discharged, as the piston moves forward, through a passage 25. The back ressure iluld 1s normally discharged throng a passage 26 in the valve casing 13 outwardly in the usual w ay when the valve 16 is open, as shown 1n Fi'g. 1. There is also a by-pass 27 which dlscharges throu h a passage 28 which 1s controlled by a nee e valve' 29 adjusted by the operator. For convenience, this is shown as discharging into a passage 30 which 1s connected with the recess in which the valve 18 is located, and also discharges into the outlet of the valve casing 13.` This bypass is adjusted b the needle valve so that under normal con itions, when the valve is in the osition shown in Fig. 1, the full flow of liquid will take place through the normal pathway and only a little oil passes out through the by-pass under low pressure. The passage 30 is to keep the pressure back of the Valve down to atmospheric pressure during the backing stroke.

The passage 25 is connected by a passage 31 with the space 22 behind the valve 18. Now under the conditions shown in Fig. 1, which shows the fast feed forward on the working stroke, with a free passage for the oil at the left, the fact that the oil is capable of entering the passa e 22 will not alter the condition of things ecause there is a free passage for the oil as shown, and the spring resists the normal pressure.

En Fi 2, the valve 16 has moved over to cut oi' t e free outlet from the back pressure side for the slow cutting feed, and then the only outlet is through the by-pass 28. When there is a sudden increase in the pressure in the left-hand side of the cylinder 9 due to the fact that the work has passed beyond cutting position and the back pressure on the cutter is no longer present to add resistance, there will be a sudden flow of oil runder pressure back of the valve 18. This overcomes the resistance of the spring 20 and forces the valve, for example, into a position as shown in Fig. 2. This reduces the flow of fluid under pressure into the cylinder on the high pressure side and thus tends to reduce thespeed of the pistonwhich would be increased by the loss of the resistance due to the cutting action otherwise. There is a passage 32 into the valve casing for the valve 18 to keep the pressure balanced on vthe return 60 exhaust of the 'back rese ure side as indicated by the arrows in iferent ways according to the position of the valve 16 asshown in Figs. 1 and 2 respectively. 5 In this way the speed of the piston is rendered practically constant. Not only is it effective at the end of the cutting action, but at any time before that in case for any reason the resistance, due to the work, is lost. This results in a more smooth action of themachine tool and its articular advantage is in preventing the sudden rush forward of the" a work or tool at the end of the cutting action.' The action is direct as the pressure duid is restricted.

In this way, it will be seen that the flow of the ressure liquid to the driving side of the cylinder is restricted directly at a point as close to the cylinder as possible by a very simple mechanism, and that indirect methods therefore are avoided.- It has no effect on the back stroke of the piston, and itis always read to work while the piston is going forwarg. l.

Although we have illustrated and described only one form of the invention we are aware of the fact-that'changes can be made therein by any person skilled in the art witho.ut departing from the scope of the invention as expressed in the claims. Therefore, we do not wish to be limited to the exact form shown, but what we do claim is 0 1. In a hydraulic actuating mechanism, the combination with a driving piston and cylinder, of means for introducing fluid under pressure into the cylinder on the driving side of the piston to advance it on a cutting stroke, a hollowvalve for controlling said means having two sets of passages for normally allowing the fluid to iiow freely into the cylinder, means for admitting a non-compressible Huid to the back side of the piston and allowing it to escape therefrom, a conduit connected with the back pressure side of the cylinder for introducing back pressure behind the valve and moving the valve to restrict the effective flow through the valve into the cylinder, and means for restricting the outflow of fluid from the back pressure side-of the piston, on the cuttingstroke. y

2. In a hydraulic actuating mechanism for a machine tool or the like, the combination with a'piston and cylinder, and means for feeding pressure iiuid to the cylinder to drive the piston on its working stroke, of a valve located in the line of supply to the cylinder, means connected with the back pressure side of the piston operating said valve by the direct action of the back pressure fluid a mainv ort from the back pressure side, a'

by-pass or the back pressure line of {iid to allow escape of a small amount of fluid from the back pressure side, and a valve for'controlling the by-pass to restrict the amount of fluid passing through it.

tion.V of the spring, and means for introduc- 3. In a hydraulic actuating mechanism, the combination with a piston and cylinder, and

lmeans for feeding pressure liquid to the cylinder for driving the piston on its working stroke, of a spring pressed valve, located L10 -in the line of supply to the cylinder, a passage connected with the back .pressure side of the piston for introducing the back pressure behind said valve to reduce the access of pressure fluid to the cylinder by the direct action of the back pressure liquid and means including a valve movable into different positions that correspond with the advancing and retracting condition of the piston for venting the spring side of said valve at times when the liquid is driving the piston on its working stroke, y

4. In a hydraulic actuating mechanism, the combination with a piston and cylinder, and means for feeding pressure liquid to the cyl- 5.85 inder for driving the piston on its working j stroke, of a valve located'in the line of supply to the cylinder, means connected with the back pressure side of the piston for reducing the flow through said valve by the direct acl9,0 tion of the back pressure liquid and a valve -for controlling the supply of liquid to and through the first named valve and venting the' side ofthe first named valve opposite that at which the back pressure acts on the first 5 named valve, to reduce the ilow. y

5. In a hydraulic actuating mechanism, the` combination with a driving piston and cylinder, of means for introducing liquid under pressure into the cylinder on the driving side 1.1.90 of the piston, a valve for controlling said means having passages for allowing the liquid Ito low into the cylinder, a passage connected with the back pressure side of the cylinder for introducing back pressure behind the valve and moving the valve to restrict the flow into the cylinder of the first named passage, and means for; introducing full pressure in front of said valve and preventing such restriction.

6. In a hydraulic actuating mechanism for machine tool units or the like, the combination With `a driving piston and cylinder, of means for introducing liquid under pressure on the driving side of the piston, a valve for controlling-said means and having passages for normally allowing the liquid to flow into the cylinder, a spring for keeping said valve in its open position normally, means for moving the valve contrary to the direction of acing full pressure at the spring end'of the valve and assisting the spring to prevent restriction of the flow from the cylinderI lthrough the valve.

for feeding pressure liquid to the cylinder to drive thel piston on its working stroke, of a vregulating .valve located in the line of. supi Ely to the cylinder, means connected with the versal to enter behind the second valve to ack ressure side ofthe iston for introducin t e back pressure iquid behind said va ve, a passage for the pressure liquid to U3.' the opposite end of the reversing valve, and

a valve for controlling the flow of liquid to the cylinder on the working stroke of the piston arranged to open said' when the second valve is near t e end of its i8) travel to prevent restriction of flow of liquid from the working end of the cylinder.

8. In a hydraulic actuating mechanism for machine tool units or the like, the combina;- tion with a piston and cylinder, and a supply assage for fluid for operating the piston for riving purposes, of a s ring pressed regulating valve in the line o flow of iiuid to the pressure side of the iston, said valve having ports for either free y or restrictivel allowing the fluid to flow, a passage to sald valve from the fluid supply, a second valve structure having means for closing and opening the passage to the first valveand also means for controlling the flow of fluid from the low pressure side of ther piston, and two portsfrom the second Valve to the front or spring side of the first valve, one of said ports adapted to be opened when the second valve is in position to fully open said passa e to assage only move it back when the pressure iiuid is admitted to the first named valve.

In testimony whereof we have hereunto ailixed our signatures.

BENJAMIN S. T. BISHOP. l v

ERIC J. HIRVONEN.

vent the first valve, and the other port a apted to be opened by the second valve when it is in position to entirely close said passage to conduct the main pressure fluid in front of the first valve to prevent that valve being moved to restrict the llow of fluid through it.

9. In a hydraulic feeding mechanism for cutting machines, the combination ofa feeding member, hydraulic operating mechanism therefor including a c linder and a piston for actuating said feeding member, a valve port through which high pressure liquid enters one side of said cylinderfor advancing said piston, a variable-setting iston valve having a piston controlling Vt e eiective opening of said port, a conduit establishing liquid communication between the cylinder space on the other side of said piston and the piston of said piston valve, and a reversing valve for said actuating piston controlling the pressure conditions on the piston of said piston valve.

10. In amachine comprising a cylinder and a reciprocatory piston, the combination therewith of a valve for admitting pressure to the high pressure side of the piston, a second valve through which the fluid passes, a

connection from the low pressure side of the cylinder back into the first valve, a second connection from the low pressure side of the cylinder leading into the second valve for moving said valve into a position to restrict the flow of fluid into the high' pressure side of the cylinder and a restricting by-pass for allowing a small amount of iiuid from the low pressure side of the cylinder upon re-

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