US2317524A - Control system - Google Patents

Description

April 27, 1943. w. ERN ST CONTROL SYSTEM Filed March 11, 1942 III! uh/Mm ATTORN EY Patented Apr. 27, 1943 UNITED STATES PATENT; OF'Fl-CEY .7 y

2,317,524 I CONTROL SYSTEM Walter Ernst, Mount Gilead, Ohio, assignor to The Hydraulic'Development Corporation; Inc.,

Wilmington; Del., 2. corporationo! Delaware Application lilarch 11, 1942, Serial No. 434,210 (c1. cos-e) 10 Claims.

This invention relates to control systems and, in articular, to control systems for hydraulic presses such as die casting machines.

In hydraulic press systems, such as used in connection with die casting, one hydraulic circuit is usually provided for closing the molds and a second hydraulic circuit brings about the actual injecting operation.

With such systems it may happen that, for some reason, for instance due to leakage, a break in the control system, or an error on the part of the'operator, the second hydraulic circuit is put into action for bringing about an injecting operation, while the molds are not completely closed. In this instance, the materialwould be injected into the open molds and not only be wasted, but might even severely injure the operator as well as the machine.

Accordingly, it is an object of the present invention to provide a safeguard againstsuch acci dents. I

It is another object of the invention to provide a control system for use in connection with hydraulic press-systems comprising two circuits for subsequently actuating two separate members, in which operation of the second member is possible only when and as long as a predetermined pressure acts upon the said 'first member.

Another object of the invention consists in the provision of a hydraulic press system having two fluid operable members, in which theoperation of one fluid operable member is automatically interrupted whenever the other fluid operable member fails to be acted upon by a predetermined pressure.

It is still another object of the invention to provide a hydraulic system having two fluid operable cylinder-piston-assemblies, in which the supply of pressure fluid to one of said cylinder-pistonassemblies is' controlled by a valve which, in its turn, is automatically controlled so that it may be shifted into open position for conveying pressure fluid to said last mentioned cylinder-pistonassembly when a predetermined pressure has been established in the other cylinder-pistonassembly, whereas said valve is prevented from being shifted into said open position, or is automatically shifted into closing position when the pressure in said other cylinder-piston-assembly is below said predetermined pressure. I

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing.

General arrangement 1 The control system accordingto the invention which is illustrated in connection with a die casting machine having a clamping plunger for. 0105 ing the molds and an injecting plunger for injecting the material into the molds, comprises a valve controlling the supply of pressure fluid to the injection cylinder. 4 v

According to the invention, a control plunger is provided which is hydraulically connected with the, clamping plunger so that when the clamping plunger has performed its clamping stroke, the pressure acting upon said clamping plunger'is conveyed to the control plunger and moves the latter into a first position against the thrust of a spring, thereby allowing said control valve to beshifted into a predetermined position enabling the supply of pressure fluid to said injectw ing plunger. v

If for some reason the pressure acting on the control plunger drops or the pressure acting on the control plungerisbeneath a predetermined pressure, the. saidv spring moves said control plunger into a'second position, thereby preventing said control'v'alve from being moved into said predetermined position so that. no fluid pressure can be conveyed to said injecting plunger.

' structural arrangement Referring to the drawinggin detail, the'latter diagrammatically illustrates an injection press comprising a clamping cylinder l with a clamping ram 2 reciprocably mounted in said clamping cylinder l. Connected to and movable by the clamping ram 2 isa mold half 3 for cooperation with a stationary mold half 4. Connected to the .mold'half'l is an injection chamber 5 adapted to receive molding material which maybe in jected by an injection plunger 6 into the mold halves} and 4. g The injection plunger 6 has a fluid operable portion reciprocably mounted in an injection cylinder 1.

One end of the injectioncylinder l.-is connected by a conduit't with a four-way,.valve 9 of any and the conduit 20 leading to the conduit The conduits l8 and iii are respectively connected with the ends of the clamping cylinder I. When the valve member I1 is shifted into the opposite position, the conduit I9 is connected with the conduit 20, while simultaneously fluid connection is established between the conduits l4 and I9.

The valve member I1 is pivotally connected by a link 2| with a three-arm lever 22, having foot pedals 23 and 24 for selectively shifting the lever 22 into clockwise or anticlockwise direction. Similarly, the valve member I0 is connected by a link 25 with a three-arm lever, generally designated 26, having 'i'oot pedals 21 and 23 for shifting the valve member III in one or the other direction. V

s The valvemember 0 has an extension 29 passing through a control cylinder 30 and adapted to be engaged by a control piston 3| reciprocably mounted in the control cylinder '39. Arranged between one side of the control piston 3| and the adjacent end of the control cylinder 30 is a stron spring 32 which urges the control piston 3| continuously into engagement with the extension 29 of the valve member ID.

The hydraulic system shown in the drawing is suppliedwith pressure fluid from a pressure fluid sourceor pump 33,'the pressure side of which is connected to the conduit ll, while the suction side communicates through the conduit 34 with the surge valve I 5.

Operation It may be assumed that the mold halves 3 and 4' are in open position so that the clamping ram 2 and the injection plunger 6 are in retracted position, while the foot pedals 23 and 21 are'in their lowermost position and the foot pedals 24 and 28 are in their uppermost position. In this instance, the extension 29 will be in its left hand position so that the spring 32 has moved the control piston 3| into and holds the same in its left hand position. The spring 32 is strong enough to prevent movement of the piston 3| by the extension 29 from its left hand position to the positionshown in the drawing, in other words, when the piston 3| is held in its left hand position by the spring 32, the operator will not be able to depress the foot pedal 28.

In order to start a working cycle, the operator now depresses'the foot pedal 24, thereby moving the'valve member l'l into its right hand position.

As soon as the mold halves 3 and 4 are closed so that further rightward movement of the ram 2 is not possible, pressure begins to build up in the conduit I! which pressure is conveyed through conduit 35 into the left end of the control cylinder 30 where it acts upon the control piston 3| and, after having reached a predetermined value, overcomes the force of the spring 32, thereby moving the control piston 3| into the position shown in the drawing. When the piston 3| has reached this position, it will be possible for the operator to completely depress the foot pedal 23, thereby shifting the valve member Ill into its right hand position, in which the conduit ll communicates with the conduit 8, while fluid connection is established between the conduits l2 and I3.

Consequently, pressure is now conveyed from the pump 33 through conduits H and 3 into the injection cylinder 1, which pressure advances the injection plunger 6 toward the left to eject material from the injection chamber 3 into the mold. During this operation, fluid is exhausted from the injection cylinder 1 through conduits I2 and I3 into the tank II.

After the injecting operation has been completed, the operator depresses the foot pedals 23 and 21 to reverse the valves 9 and I3, thereby also reversing the movement of the clamping ram 2 and the injection plunger 6. This spaces the mold halves 3 and 4 from each other and allows removal of the work piece from the molds.

It may now be assumed that, during the first phase of the cycle, 1. e., while the clamping ram 2 was moving toward the right, the operator thought that the mold halves 3 and 4 had already been closed and tried to depress the pedal 28. However, since at this time the picton 3| is still in its left hand position and held in the same by the spring 32, the extension 23 is positively prevented from being shifted to ward the right, thereby positively preventing the operator from depressing the pedal 23 and starting a premature operation of the valve-9.

. If duringthe actual injection operation the pressure in the clamping cylinder I suddenly drops for some reason, for instance due to a break in the pipe system, the pressure in the left hand portion of the control cylinder 33 likewise drops and the strong spring 32' immediately shifts the piston 35 -award the left, thereby preventing further 'sur ily of pressure fluid to the injection plunger and stopping the injecting operation of the vtter. Y As will be clear from the a'.ive, the inven-' .tion constitutes a material s: eguard against accidents caused by the advancement of the injection plunger 3 into the injection chamber 5 while the mold halves 3 and 4 are not properly closed or not under the desired clamping or closing pressure.

It should be noted that, while the invention has been described, for the sake of simplicity, in connection with two four-way valves operated by the operator, it is of course understood that these valves may also be operated subsequently in an automatic manner by means oi any control systems of standard design. Furthermore, while the present invention has been described with one delivery pump only, it is of course understood that, if desired, separate pumps may be provided for supplying pressure fluid to the clamping and injection cylinder re-. spectively. In this instance, the supply of one pump to the clamping cylinder will be controlled by the four-way valve it, while the supply of pressure fluid from the other pump will be controlled by the four-way valve 9. The operation of the control system, including the control piston 3| and cylinder 30, will obviously not be impeded by such a variation of the hydraulic system. I t,

It is also to be understood that, although the invention has been described in connection with a die casting machine, it is by no means limited thereto and may be used in connection with any hydraulic system in which a plurality of fluid operable plungers are operated subsequently, and in which it is desired that pressure fluid should be conveyed to one plunger only after and as long as another plunger is acted upon by a predetermined fluid pressure.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims and the invention.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a hydraulic system, a first fluid operable plunger, a second fluid operable plunger, means for admitting pressure fluid to said first plunger, means for admitting pressure fiuid to said second plunger, means for preventing the supply of pressure fluid to said second plunger prior to the establishment of a predetermined pressure on said first plunger, and means responsive to a drop in pressure on said first plunger below said predetermined pressure for automatically interrupting the supply of pressure fluid to said second plunger.

2. In a hydraulic system, a first fluid operable plunger, a second fluid operable plunger, first valve means for controlling the supply of pressure fluid to said first plunger, second valve means movable selectively from a first position in which it prevents supply of pressure fluid to said second plunger into a second position for admitting pressure to said second plunger, and control means normally preventing movement of said second valve means into said predetermined position, said control means being arranged to move into inoperative position in response to a predetermined pressure on said first plunger, to thereby allow movement of said second valve means into said predetermined position, and also being arranged to bring. about a return of said second valve means into its first position in response to a drop in pressure on said second plunger below said predetermined pressure.

3. In a hydraulic system, a first fluid operable plunger, a second fluid operable plunger, first valve means for controlling the supply of pressure fluid to said first plunger, second valve means movable from its closing position into its open position for admitting pressure fluid to said second plunger, 2. control member movable into a first position forpreventing movement of said second valve means into said predetermined position and movable into a second position to allow movement of said second valve means into said second position, yielding means continuously urging said control member into i adapted in response to a drop in pressure in said conduit means below sald .predetermined pressure to automatically cause said control member to return said second valve means into I its'closing position. i r

4. In a hydraulic system, a firstcylinder, a first plunger reciprocable in said first cylinder, asecondcylinder, a second'plunger reciprocable in said second cylinder, valve means operable to subsequently admit-pressure fluid to said first cylinder and said second cylinder, and means responsive tofa predetermined pressure condition in said first cylinder for automaticallyactuating said valve. means soasflto prevent further supply of pressure fiuid- .to said second cylinder," M i v 5. Ina hydraulic system, a first cylinder, a first fluid operable plunger reciprocable in said first cylinder, a second cylinder, a second fluid operable plunger reciprocable in said second cylinder, first valve means for controlling the supply of pressure fluid to said first cylinder, secondfirst fluid operable plunger reciprocable in said first cylinder, a second cylinder, 9. second fluid operable plunger reciprocable in said second cylinder, first valve means for controlling the supply of pressure fluid to said first cylinder to actuate said first plunger, second valve means controlling the supply of pressure fluid to said second cylinder, a control cylinder hydraulically connected with said first cylinder, and a fluid operable control plunger reciprocable in said control cylinder and normally preventing movement of said second valve means into position for admitting pressure fluid to said second cylinder, said control plunger being arranged for movement into inoperative position in response to a predetermined pressure in said first cylinder.

7. In a hydraulic system, a first fluid operable plunger, first valve means movable into position for conveying pressure fluid to said first plunger, a second fluid operable plunger, second valve means movable into a predetermined position for admitting pressure fluid to said second plunger, yielding means normally preventing movement of said second valve means into said predetermined position, and means responsive to a predetermined pressure on said first plunger for making said yielding means ineffective to thereby allow movement of said econd valve means into said'predetermined p0 ition.

8. In a hydraulic system, a first fluid oper: able plunger, first valve means operable to admit pressure fluid to said first plunger, a second fluid operable plunger, second valve means including a reciprocable valve member movable into a predetermined position ior admitting pressure fluid to said second plunger, a reciprocable control plunger normally urged into a first position for preventing said valve member from being moved into said predetermined position, and means responsive to'a predetermined pressure on said first plunger for moving said control plunger into a second position to allow movement of said valve member into said premaintaining its tendency to urge said second determined position. valve means into said second predetermined 9. In a hydraulic system, -a flrst fluid operable plunger, first valve means for controlling the supply of pressure fluid to said flrst plunger for actuating the same, a second fluid operable plunger, second valve means including a reciprocable valve member movable selectively into a predetermined first position for admitting pressure fluid to saidsecond plunger or into a predetermined second position for preventing the supply of pressure fluid to said second plunger, a control cylinder hydraulically connected with said first plunger, and means associated with said control cylinder for continuously urging said valve member into said predetermined second position, said means being movable into inoperative position in response to a predetermined pressure on said first plunger while position.

10. In a hydraulic system, a plurality of fluid operable plungers, a plurality of control valves respectively associated with said plungers for admitting pressure fluid thereto to actuate said plungers, and means preventing the movement of one valve into position for admitting pressure fluid to the plunger pertaining thereto prior to the establishment of a predetermined pressure on the plunger previously actuated, said means also being operable automatically to interrupt the supply oi pressure, fluid to said first mentioned plunger when the pressure on said last mentioned plunger drops below a predetermined value.

WALTER ERNST.

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