US3249019A - Quick-acting multiple-force air cylinder - Google Patents

Description

y 3, 1966 M. M. SEELOFF 3,249,019

QUICK-ACTING MULTIPLE-FORCE AIR CYLINDER Filed June 12, 1964 39 ADJUSTABLE RELIEF VALVE INVENTOR. MELVIN M. SEELOFF ATTORNEY United States Patent 3,249,019 QUICK-ACTING MULTlPLE-FGRCE AIR CYLINDER Melvin M. Seeioli, Warren, Ohio, assignor to The Taylor Winfield Corporation, Warren, Ohio, a corporation of Ohio Filed dune 12, 1964, Ser. No. 374,791 9 Claims. (Ci. 91-165) the present invention is to devise a practical and dependable arrangement in air-actuated force applying cylinder for more rapidly increasing the force applied and for doing the same in a more closely controllable and predictable time intervalmeasured in milliseconds, for example.

It has been heretofore proposed to provide apparatus of the general nature discussed above with means to apply one value of air pressure to one side of a piston in a cylinder and lesser air pressure to the other side of the piston together with means to rapidly discharge the lesser air pressure at a critical time to effect an abrupt increase of force exerted by the piston. However, the inherent geometry of a conventional cylinder and piston limits the rate of drop of the lesser air pressure and renders the timing of the application of the higher force somewhat erratic so that such devices have been found to be unsuitable for certain critical applications.

The present invention overcomes the deficiency of the above described prior art devices by providing a quickacting exhaust valve for the back-pressuring air which is of exceedingly large capacity and which is instantaneously operable to relieve the pressure from all circumferential segments of the piston thereby dispensing with practically all of the delay heretofore caused by required movement of the back-pressuring air.

The above and other objects and advantages of the invention will become apparent upon consideration of the following specification and the accompanying drawing wherein there is disclosed a preferred embodiment of the invention.

The sole figure of the drawing is a longitudinal section of a double-acting air cylinder specially constructed in accordance with the principles of the invention, with air supply and control components being shown in appended schematic outline.

In the drawing, reference numeral 1% designates a first cylinder barrel which is fitted to a head 11, which has a shoulder 12 on its outer surface, and which has a rounded nose 13 at its inner end. Fitted against the shoulder 12 is a second cylinder barrel 14 having an enlarged annular recess 15 in a portion of its inner surface adjacent the shoulder 12, and which is provided with an integral protuberance 16. For a purpose to be later described, the barrel 14 is also formed provided in its side wall with an enlarged aperture 17. Closing off the opened end of the barrel 14 is a head 18, and in actual practice tie rods, not shown, are employed to clamp the heads 11 and 18 tightly towards one another to keep the parts assembled, it being observed that the head 18 is shouldered to engage the end of the barrel 14.

Head 18 is centrally bored to Slideably receive a piston rod 19 which is rigidly connected to a piston 20 slideably 3,249,019 Patented May 3, 1966 received in the barrel 10. Piston 20 is provided with an O-ring or other suitable packing 21, and mounted in the bore of the header 18 is a gland 22 acting on a packing ring 23 which bears against the rod 19. Member 24 is a vertically adjustable cushioning stop to limit the upward travel of the piston 2d whereby an adjustable stroke may be obtained, but since this feaure is not a part of the present invention the same will not be further described.

Slideably received within the barrel 14 at the end 13 of the barrel 10 is a free-floating piston 25 having a centrally disposed bore for the passage of the rod 19, this bore being sealed by the resilient O-ring 26 or other suitable packing which is received in an annular recess in the bore and which bears against the rod 19. A larger resilient O-ring 27 or other suitable packing slideably seals the piston 25 in the barrel 14. For a purpose to be later described, the working diameter of the barrel 14 and consequently of the piston 25 is somewhat larger than the working diameter of the barrel 1i Extending longitudinally inward from the end face of piston 25 which is adjacent the piston 20 and thence radially outward to the periphery of the piston 25 is a passageway 28 which is fitted with a conduit 29 extending outwardly through the aperture 17 of the barrel 14. In another circumferential portion of the piston 25 there is provided a longitudinally extending passage and a spring-pressed check valve 30 which allows for the passage of air from the face of the piston 25 which is opposite the piston 20 to the aforementioned face of piston 25 which is adjacent the piston 20 but which blocks the flow of air in the opposite direction. Radially outward of these passages the end face of the piston 25 which is adjacent or toward the piston 20 is provided with an annular groove to receive and retain a ring 31 of soft rubber-like material for bearing against the adjacent end 13 of the barrel It to form therewith a sealing valve.

The protuberance 16 on the barrel 14 is cored out and machined to provide a mounting manifold for a solenoid actuated three-way valve 32, and for this purpose there is one passageway 33 extending entirely through the protuberance and barrel from the valve 33 while another passageway 34 in the protuberance extends from the valve to the atmosphere. Passageway 33 communicates with a recess 35 in the cylinder head member 18, which recess is in open and wide communication with the inner face of the cylinder head 18 directly opposite the adjacent end face of the piston 25. Extending through the side wall of the barrel 14 and communicating with the annular space 15 therein is one or more large discharge openings or conduits 36. Air is supplied to the barrel 10 outwardly of the piston 26 by a three-way valve 37 connected to the cylinder by a passageway 38 formed in head 11. For a purpose to be later described, the outer end of conduit 29 is connected to atmosphere through an adjustable pressure relief valve 39.

Considering now the operation of the above described apparatus, and assuming that the same is being used to apply the welding force to the movable electrode of an electric resistance welding machine it should be noted, first, that the parts are so dimensioned that when the valve 13, 31 is closed the piston 25 will be spaced from the head 18 to provide the illustrated dimension and space 40. The movable electrode holder (not shown) is so adjusted with respect to the rod 19 that when the electrodes are first closed onto the work to apply the squeeze pressure, the piston 20 will be quite close to but still spaced from the piston 25 to effect the waferlike air space 41. The valve 32 is operated by a solenoid to couple the passage 33 with the exhaust passage 34 and it may be of the bias type whereby the passage 33 is coupled to a source 42 of regulated air pressure when the solenoid is de-energized. Of course, a pair of oppositely acting solenoids may be employed, if desired, to shift the valve from one of its operating positions to the other. In any event, the valve 32 is so shifted that the source of regulated air pressure 42 is connected through passages 33 and 35 to the space 40.

The air pressure from passage 35 and space 40 can move upwardly through the check valve 30 to the space 41. However, because of the greater effective area of the space 40 as compared to the effective area of the space 41, the piston 25 will hold in upper position and the valve 13, 31 will remain closed. During this part of the operating cycle the force exerted by the rod 19 will be determined by the differential of the air pressure exerted on opposite sides of the piston 20. This, of course, is, in turn, determined by the pressure of the air admitted to the head end of barrel through valve 37 and by the setting of the relief valve 39. This relief valve is always set for a lower pressure than the pressure of the supply 42.

At the start of a spot welding cycle, for example, the piston 21 will, of course, be in uppermost position under the back pressure of the air source 42, the valve 37 being then so actuated that the passage 38 is connected to atmosphere. The piston 25 will be in upper position as aforesaid. The valve 39 is set for a pressure lower than the pressure of the source to the valve 37, and if now the valve 37 is actuated the piston will move down until the electrodes are clamped onto the work, the excess air in the space below the piston 20 bleeding off through valve 39. The electrodes will now hold at a squeeze force since any leakage of air from the now fixed space 41 will be made up infiltration through the valve 30.

During the above-mentioned squeeze period, the welding electrodes are electrically energized to bring the metal clamp therebetween to welding temperature, and it is well recognized in the art that at a critical time during or shortly after the flow of welding current it is commonly desired to impart a much heavier but controlled force to the movable electrodei.e. a forging hammer-like blowand this is accomplished in accordance with the present invention by actuating the valve 32 to quickly exhaust the air pressure from the space 40 through the passages 35, 33 and 34 to the atmosphere. Almost immediately the pressure in space 41 forces the piston downwardly and quickly opens the very large annular valve 13, 31 allowing the pressure in space 41 to quickly escape into the annular recess 15 of the barrel 14 from whence it is exhausted to atmosphere through the ports 36. This very abrupt drop in pressure on the rod end of piston 20 causes the air on the free end of the piston to react quickly in increasing the force applied to this piston and rod 19. The action is very rapidbeing of the order of a few milliseconds after actuation of the valve 32 and this slight lag is dependably consistent. It may therefore be integrated in the setting of the heretofore known precision timing and/ or synchronizing circuits for the actuating solenoid of the valve 32.

By providing the mounting manifold for the valve 32 in the form of the protuberance 16 integral with the barrel 14 the length of passages required for the evacuation of the space is kept to a minimum. Further, the cross sections of these passages are quite large in relation to the small volumetric capacity of the space 40. The withdrawal of pressure from the space 40 is therefore substantially instantaneous.

As regards the evacuation of pressure from the space 41, it should be observed that the same proceeds radially outward throughout the whole of the circumferential extent of the barrel 10. The drop in pressure in space 41 is thus also almost instantaneous. The two or three millisecond delay in the application of the forging or higher pressure exerted by the rod 19 is therefore caused almost entirely by the inertia of the parts which is predictable and consistent and thus capable of being compensated for in the precise timing of the application of the higher force in the normal use of the device.

Having thus described my invention, what I claim is:

1. A double-acting air cylinder assembly for imparting in one direction and in quick succession an initial force and a larger force comprising a first barrel having a piston slideable therein rigidly connected to a rod for imparting said force, a second barrel in axial alignment with said first barrel and having an internal diameter greater than the internal diameter of said first barrel, a free-floating piston slidably received on said rod and within said second barrel, a cylinder head on said first barrel and a second cylinder head for said second barrel, said second cylinder head having a packed bore therethrough for the slideable reception of said rod, means comprising the end of said first barrel opposite said first header and the adjacent end face of said free-floating piston to provide an annular valve which discharges outwardly to the atmosphere, means comprising an adjustable relief valve to maintain air pressure in a first space between said end face and said first mentioned piston at a predetermined value, means to supply regulated air pressure to a second space between said free-floating piston and the cylinder head on said second barrel whereby said annular valve is held closed, means to supply air under pressure to the head end of the space within said first barrel whereby said first mentioned piston and rod may be caused to move and exert an initial force, and means to abruptly withdraw the air pressure from said second space to cause said free-floating piston to move relatively to said first barrel and open said annular valve whereby a greater force is imparted by said rod.

2. A double-acting air cylinder assembly for imparting in one direction and in quick succession an initial force and a larger force comprising a first barrel having a piston slideable therein rigidly connected to a rod for imparting said force, a second barrel having a cylinder portion spaced from but in axial alignment with said first barrel, a free-floating piston slideably received on said rod and within said second barrel, a cylinder head on said first barrel and a second cylinder head for said second barrel, said second cylinder head having a packed bore therethrough for the slideable reception of said rod, means comprising the end of said first barrel opposite said first head and the adjacent end face of said free- -floating piston to provide an annular valve which discharges outwardly to the atmosphere, means comprising an adjustable relief valve to maintain air pressure in a first space between said end face and said first mentioned piston at a predetermined value, means to supply air pressure to a second space between said free-floating piston and the cylinder head on said second barrel whereby said annular valve is held closed, means to supply air under pressure to the head end of the space with-in said first barrel whereby said first mentioned piston and rod may be caused to move and exert an initial force, and means to abruptly withdraw the air pressure from said second space to cause said free-floating piston to move relatively to said first barrel and open said annular valve whereby a greater force is imparted by said rod.

3. An assembly according to claim 2 further including a passage through said free-floating piston interconnecting said first and second spaces, a check valve in said passage to permit the flow of air only in the direction from said second space to said first space, the arrangement being such that upon the exhaustion of air from the head end of said first barrel the air in said second space may move to said first space to retract said first mentioned piston and rod, and said arrangement being further operative to prevent the pressure of air in said first space from escaping during the said withdrawal of air pressure from said second space.

4. An assembly according to claim 2 further including an aperture in the cylinder portion of said sec-0nd barrel longitudinally intermediate the normal ends of stroke of said freedloating piston, and said means to maintain air pressure in said first space comprising a passage in said free-floating piston extending longitudinally of said end face and thence radially outward through said aperture, said relief valve being in said passage.

5. A double-acting air cylinder assembly for imparting in one direction and in quick succession an initial force and a larger force comprising a cylindrical structure having a head end and open end and an intermediate valve seating means on the open end of a cylindrical outer wall portion thereof, a force-applying piston slideably received in one end of said structure and having a connected piston rod slideable through a packed bore in the head at the other end of said structure, a freefioating piston slideable on said rod and within said structure and being positioned longitudinally between said first mentioned piston and said last mentioned head, said free-floating piston being slideable in said structure between first and second limiting positions which are, respectively, toward and away from said first mentioned piston, an enlarged annular valve providing a large port to atmosphere and being in sealing relation with said valve seating means in the side wall of said structure on the rod end of said first mentioned piston, means to maintain air pressure on opposite ends of said free-floating piston to maintain said annular val-ve closed whereby upon supplying air pressure to the head end of said first mentioned piston said rod may exert an initial force based on the diiference of air pressure at opposite ends of said first mentioned piston, and means to rapidly exhaust the air pressure from the end of said free-floating piston which is opposite said first mentioned piston to allow said free-floating piston to retract from said first mentioned piston and thereby open said annular valve to rapidly exhaust the air pressure from the rod end of said first mentioned piston.

6. Apparatus according to claim 5 further including a longitudinal passage through said free-floating piston and a check valve in said passage whereby air may flow through said free-floating piston in a direction toward said first mentioned piston but not in the opposite direc tion, the arrangement being such that said passage and check valve is operative to convey air to retract said first mentioned piston.

7. A double-acting dual force air cylinder comprising a first barrel with a head on one end and having an exposed opposite end, a piston slideably received in said first barrel and having an operating rod extending outwardly of said exposed end, a second barrel of larger diameter than said first barrel and having an internal annular recess surrounding said exposed end and connected to said first barrel intermediate the ends thereof, a head for said second barrel bored and packed to slideably receive said rod, said annular recess being ported to atmosphere, la free-floating piston slid-eably received for a. limited movement in said second barrel and slideable on said rod intermediate said exposed end and said head for said second barrel, said freefloating piston having an annular sealing ring on its inner face to engage said exposed end to form therewith an enlarged annular valve, means to supply air pressure to the opposite face of said free-floating piston to maintain said annular valve closed, means to apply differential air pressures to said first barrel on opposite sides of said first mentioned piston to cause said rod to exert a predetermined initial fierce, and means to exhaust the air pressure from the said other face of said free-floating piston to thereby rapidly open said annular valve by the air pressure existing between said first mentioned piston and said free-floating piston.

8. Apparatus according to claim 7 further including a passage in said free-floating piston interconnecting the opposite faces thereof, and a check valve in said passage permitting the flow of air therethrough only in a direction toward said first mentioned piston.

'9. Apparatus according to claim 7 further including a valve-mounting manifold formed integrally with said second barrel, and a valve secured directly to said manifold for exhausting the air from the face of said free-floating piston which is opposite said annular valve.

References Cited by the Examiner UNITED STATES PATENTS 2,720, 864 10/ 195 5 Smith 9 l442 2,994,302 -8/ 1961 Murek 91165 X 3,136,220 6/ 1964 K'arnm 9 l SAMUEL LEVIN-E, Primary Examiner.

P. T. COBR'IN, Assistant Examiner.

Claims (1)

1. A DOUBLE-ACTING AIR CYLINDER ASSEMBLY FOR IMPARTING IN ONE DIRECTION AND IN QUICK SUCCESSIVE AN INITIAL FORCE AND A LARGER FORCE COMPRISING A FIRST BARREL HAVING A PISTON SLIDEABLE THEREIN RIGIDLY CONNECTED TO A ROD FOR IMPARTING SAID FORCE, A SECOND BARREL IN AXIAL ALIGNMENT WITH SAID FIRST BARREL AND HAVING AN INTERNAL DIAMETER GREATER THAN THE INTERNAL DIAMETER OF SAID FIRST BARREL, A FREE-FLOATING PISTON SLIDABLY RECEIVED ON SAID ROD AND WITHIN SAID SECOND BARREL, A CYLINDER HEAD ON SAID FIRST BARREL AND A SECOND CYLINDER HEAD FOR SAID SECOND BARREL, SAID SECOND CYLINDER HEAD HAVING A PACKED BORE THERETHROUGH FOR THE SLIDEABLE RECEPTION OF SAID ROD, MEANS COMPRISING THE END OF SAID FIRST BARREL OPPOSITE SAID FIRST HEADER AND THE ADJACENT END FACE OF SAID FREE-FLOATING PISTON TO PROVIDE AN ANNULAR VALVE WHICH DISCHARGES OUTWARDLY TO THE ATOMSPHERE, MEANS COMPRISING AN ADJUSTABLE RELIEF VALVE TO MAINTAIN AIR PRESSURE IN A FIRST SPACE BETWEEN SAID END FACE AND SAID FIRST MENTIONED PISTON AT A PREDETERMINED VALUE, MEAN TO SUPPLY REGULTED AIR PRESSURE TO A SECOND SPACE BETWEEN SAID FREE-FLOATING PISTON AND THE CYLINDER HEAD ON SAID SECOND BARREL WHEREBY SAID ANNULAR VALVE IS HELD CLOSED, MEANS TO SUPPLY AIR UNDER PRESSURE TO THE HEAD END OF THE SPACE WITHIN SAID FIRST BARREL WHEREBY SAID FIRST MENTIONED PISTON AND ROD MAY BE CAUSED TO MOVE AND EXERT AN INITIAL FORCE, AND MEAND TO ABRUPTLY WITHDRAW THE AIR PRESSURE FROM SAID SECOND SPACE TO CAUSE SAID FREE-FLOATING PISTON TO MOVE RELATIVELY TO SAID FIRST BARREL AND OPEN SAID ANNULAR VALVE WHEREBY A GREATER FORCE IS IMPARTED BY SAID ROD.

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