US2500383A - Pneumatic pressure operated device - Google Patents

Description

March 14, 1950 I H. J. SADLER ET AL PNEUMATIC PRESSURE-OPERATED. DEVICE 2 Sheets-Sheet 1 Filed April 3, 1948 March 14, 1950 H. J. SADLER ET AL 2,500,383

PNEUMATIC PRESSURE-OPERATED DEVICE Filed April 5, 1948 r 2 Sheets-Sheet 2 Patented Mar. 14, 1959 PNEUMATIC PRESSURE OPERATED DEVICE Harry J. Sadler and ErnestE. Cook, Minneapolis,

Minn; said Geek assignor to said Sadler Application April 3, 1948, Serial-No. 18,754

11 Claims.

under pressure from one thereof to the other thereof.

Still more specifically; an important object of our invention is the provision of a novel chuck or collet closer utilizing our novel valve mechanism and apparatus for. transfer of fluid under pressure from a stationary to a relatively movable part thereof, whereby to contract and release said collet.

A still further object of our invention is the provision of a device of the class above-described which includes relatively few movable parts, which is extremely durable in construction, which is inexpensive to manufacture, and which is efficient and trouble-free in operation.

The above and still further objects-of our invention will become apparent from the following detailed specification, appended claims, and attached drawings;

Referring to the drawings, wherein like characters indicate likeparts throughout the several views:

Fig". l is a view in front elevation of a collet chuck built in accordance with our invention and mounted upon a; conventional lathe, some parts being broken away andsome. parts shown in section;

Fig. 2 is a view, partly in horizontal section and partly in diagram, taken substantially on the line 2-2. of Fig. 1. and turned. 90 with respect thereto;

Fig. 3 is afragmentary-cross section, taken on the line 3-45: of Fig. 2,.v with some parts being broken away;

Fig. 4 is axfragmentary cross section, taken substantially on the line i-d of Fig. 2;

Fig; 5 is a; fragmentary detail in section, taken onthe line 55 of Fig. 2;

Fig. 6 is a transverse section, taken on the line 55 of Fig. 2; and

Fig, 7 is an enlarged fragmentary sectional detail, taken on the; line '!T-of Fig. 3.

Referring; with; greater particularly to the drawings, the numeral! indicates, in its entirety,

aheador. casinglhaving acup-shaped front wall Zandarelatively, flat rear wall 3 connected to the outer peripheral edge of said; front wall 2 by means ofmachinescrews or the like l. The elements Zanddare preferably made from lightweight; material such as aluminum, in order to reduce the weight of. the entire device. The rear wall}: is-lp-referably cast around and secured fast on an. annular, bushing; 5, preferably made from steel or other material of considerably greater hardness thanthe Wa1l3- The bushing 52.15. internally: threaded to enga e the threaded end E5. of; a hollow rotary; spindle l which may berotatively carried bythe head of a conventional, lathe,,, screw, machine, or the like, not shown.- A spacer 8;,and a collar llperform no particular function with; regard to the instant invention, being merely parts, of conventional lathe structure.

Elements; l, 2', and 5; cooperate to produce a circular cavity;v la into which axially projects an annular, bearing boss portion l l of the bushing.;5.- Theinner peripheral wall section of the front; wall 2 isprovided with a, sleeve l2 which may be made of suitablebearing material. An annular pistonl3 is axially slidably mounted in the, cavity ill; with the inner periphery thereof snugly encompassing. the bearing boss H and the outer periphery thereof slidably engaging the: sleeve l2, Annular seals i l and i5 prevent leakageof, fluid under pressure between the piston l3 and the'bearing block H and sleeve l2 respectively. The piston l3, a portion of the sleeve l2, the rear wall 3, and bearing boss M define a. pressure chamber It, the piston it being inthe nature of a movable wall thereof. The piston is is yield-ingly biased in one direction (toward a pressure chamber-contracting position) by means of aplurality of circumferentially-spaced coil compression-springs l'l seated in alignedpockets l8 and 29 in the front wall I and piston l3 respectively. An annular seal 26 is interposed in the connection between the peripheral portion. of the front wall Zand the rear wall 3 topre-vent leakage of fluid from the chamber; l6 therethrough The piston I3 is provided with an axially forwardly-projecting annular flange 21!, which is internally-threaded to; receive an externallythreaded collar which is provided with a plurality of: circumferentially spac ed inwardly opening cup-shaped pockets-23 which snugly receive the ballelike radially outer'ends 2,. l'of radially-projecting lever'armslfi. The lever arms 25 are disposed withinradialchannels 26. in an annular ring 21, which is internally-threaded to receive the threaded end 28 of a collet 29, having a plurality of jaws 38 formed by slotting the collet 29 axially, as indicated at 3i, in the conventional manner. The collet 29 is provided with a tapered peripheral outer face 32 which is adapted to be engaged by a corresponding tapered portion 33 of an annular contraction ring 34 axially slidable on the outer peripheral surface of the collet '29 and in an opening or bore 35. Forward movement of the contraction ring 34 is lifted by engagement of a circumferential flange 36 with a shoulder in the front Wall 2 formed by a counterbore therein.

The bottoms of the channels adjacent the outer ends in the annular ring 2'! are each provided with a projecting fulcrum-forming edge or shoulder 3'7 which is adapted to engage the intermediate portion of its respective lever arm 25. As shown in Fig. 2, the radially inner ends of the lever arms 25 abut the inner end of the contraction ring 35. Centering of the collet 29 with respect to the piston i3 is insured by the seating of an annular flange 38 On the ring 2? within an annular groove 39 in the piston 13.

From the above, it should be obvious that movement of the piston 13, against the bias of the springs I'i, axially in the direction of the collet 29, or from the left to the right with respect to Fig. 2, removes the axial thrust imparted by the radially inner ends of lever arms 25 upon the contraction ring 34. Removal of axial pressure against the contraction ring 34 allows the same to slide axially from the right to the left with respect to Fig. 2, thereby releasing the grip of the several jaws 36 upon the stock or workpiece contained therein but not shown. Movement of the piston 13 in a direction from the right to the left with respect to Fig. 2 under bias of the springs ll, on the other hand, causes the radial lever arms 25 to engage the edges or shoulders 3'], whereby to produce an axial thrust of the inner ends of the arms 25 against the contraction ring 34 in a direction to contract the jaws of the collet 29.

The collet 29 is provided with a plurality,.as shown four, of circumferentially-spaced keyways El], and which are adapted to slidably seat the inner ends of diametrically-opposed pins ll. The pins M are provided with head portions 42 which are slidable in radial bores 43 in the central portion of the front wall 2. The pins 4! extend radially through diametrically-opposed radial passages M in the contraction ring 34 and are biased in a radially outward direction by means of coil compression springs 45 (see particularly Fig. 6). It will be seen particularly by reference to Fig. 2, that the bores 13 are located outwardly of the main body portion of the front wall 2 in an axially projecting hub portion 2' thereof. A ring or collar 4-5 encompasses and is rotatably slidable on the outer periphery of the hub 2 and is provided with a pair of diametrically-opposed recesses 4'! that are adapted to receive, under rotary movements of the collar to, the heads 42 of the pins M. The pins 4| are of such a length, that when the heads 32 thereof are contained within the recesses l! the inner ends 4| are spring pressed radially outwardly of the keyways ill so that the collet 29 may be rotated with respect to the annular ring 21. Rotation of the collet 29 with respect to the ring 2'! due to the threaded engagement therein provides axial adjustment of the collet 29 with respect to the contraction ring 34. When the proper adjustment has been obto close the inlet port 6!.

tained, the ring 46 is rotated to a point where the recesses 47 are circumferentially opposite from the heads 12 so that the pins ii are moved into opposed keyways it. The recesses 41 are so shaped that rotation of the ring 46 moves the heads 42 therefrom with a camming action against bias of the springs 45. Accidental rotation of the ring 36 with respect to the hub 2' is prevented by a pair of diametrically-opposed spring pressed bore elements 38 adapted to engage circumferentially-spaced detents 19. The ring 4%; at one and engages the outer surface of the wall 2 and is limited in axial movements outwardly of the wall 2 by means of an annular plate 58 which is secured to the outer end of the hub 2' by means of machine screws or the like 5| (see particularly Figs. 1 and 2). The internal and external diameters of the plate 56 are such that the plate so does not interfere with free rotating movements of the ring 36 nor free axial movements of the contraction ring 34.

The rear wall 3 is formed to provide an annular inlet passage 52 which communicates with the pressure chamber 13 through a pair of diametrically-opposed disc-like check valves 53. The check valves are contained in recesses 54 in the rear wall 3 and are secured by screws or the like 55, whereby to be seated over valve openings 52' communicating with the passage 52 and the pressure chamber :5. The rear wall 3 is channeled adjacent the inlet passage 52 to receive an annular check valve 56 which is held in place by means of a clamping ring 51 which is rigidly secured to the wall 3 by means of a plurality of screws 58. As shown in Fig. 2, the rear wall 3 is provided with a radially inwardly projecting flange 55 which is bevelled at its inner edge and cooperates with a bevelled outer edge 6B of the ring 5'. to form an inlet port 61. The annular check valve 55 may be made from any resilient flexible material, but preferably, and as shown, is made from soft rubber or the like and is normally seated against the axially inner ends of the flange 59 and clamping ring 57 whereby The annular passage 52 communicates with atmosphere exterior of the head i through a restricted bleeder orifice 52 and an internal passageway 63.

Air is exhausted from the pressure chamber l5 through a passage 64 leading therefrom into an exhaust valve chamber 65, and from thence through a passage 58 into a cavity I ll. From thence, the exhaust air from the pressure chamher it is dissipated outwardly from the cavity lo through the slots 3| in the collet 29. An exhaust valve 61 is provided at one end with a head 68 that is preferably rectangular in cross section and which is cone-shaped at its extreme outer end. The circumferentially-spaced outer end is covered with a sealing cap 69 which, under axial movements of the valve 6i, is adapted to seal off one end of the passage 66. The valve 6'! is proided with an axially extending reduced shank 1B which terminates at its rear end in a circumferential flange H which is preferably made of relatively soft flexible material such as rubber or the like and which is held against axial movement adjacent its peripheral portion by engagement at one side thereof with an annular shoulder l2 formed in the peripheral portion of the wall 2. The flange H is held against axial movement in the opposite direction by means of an annular stop collar 13 which abuts the outer peripheral portion of the rear wall 3. It will be seen, particularly by reference to Figs. 2 and 7, that the atom-see passageway-63 communicateswiththe-end of the chamber 65 opposite the exhaust passagefit, but is sealed again st communication with the exhaust passages ti and 66 by the resilient flange H. The flange H, due to its resilient nature, permits axial movement of the valve 6'3 within the chamber 55 for a purpose which willhereinafter become apparent.

Fluid medium underl'elatively high pressure, preferably air, is applied to the annular port 6! and against the check valve 56 in a highly concentrated jet by means of a nozzle i l which is adapted to be located in the path or" travel of the annular port A hose coupling 75 has screwthreaded engagement with the nozzle l l andas shown in Figs. 1 and 2 is clamped in a split block 76 by means of a nut-equipped bolt l'lwhich also secures the block it to a bracket it. The bracket '18 may be fastened to the machine tool in any number of ways, but as shown in Fig. 1 rests upon a lathe bed is and is firmly held thereon by means of a clamp Bil and a clamping screw 8i. As shown diagrammatically in Fig. 2, air is supplied to the coupling 55 and nozzle i l from a pressure tank 82 and a pump or the like 83 through conduit means 84. A valve 85 is interposed in the conduit 84 between the tank 82 and the coupling l5, and may be either automatically or manually controlled.

As above pointed out, the check valve 56 normally closes the annular port 6!, but due to its flexible and resilient nature is adapted to become unseated and to open the port 6: to communication with the annular passage 52 at localized areas of an extent very slightly larger than the cross sectional area of the jet of fluid projected thereagainst (see particularly Fig. 5). Air admitt-ed to the annular passage 52 passes through the openings 52', unseating. the check valves 53, and into the annular pressure chamber E6. Simultaneously, the air under pressure in the passage passes through the passageway t3 and exerts pressure against the flange 7 i, whereby to move the valve ii to close exhaust passage 66. size of the bleeder orifice 52 is such that air escapes therethrough at a much slower rate than it is being projected into the annular passage 52 by means of the nozzle E i, so that pressure is built up within the pressure chamber 55 at a I the annular piston I3 in a direction from the it to the ri ht with respect to Fig. 2. As herenbeiore described, such movement of the piston .eases pressure of the radial lever arms 'ainst the contraction ring 34 and subsequent '-'=ease of gripping pressure of the ccllet 29 ainst a workpiece held therein. Cutting off of he fluid pressure supplied to the nozzle Hi, which may be caused by manipulation of the valve 85, allows the annular check valve 56 to seat against the flange 59 and seal the port 6! over its entire circumferential area. This rescaling is enhanced by the relatively high fluid pressure within the passage 52. With the cutting off of the fluid supply from the nozzle it, however, the fluid or air continues to bleed from the orificeiiz and a differential in pressure is formed between the passage 5'2 and the pressure chamber it. It will be noted that fluid pressure in the pressure chamher it and in the valve chamber 55 is equal due to the connection therebetween of the exhaust passage The consequent diiierential in pressure in the valve chamber 65 and the annular passage 52 causesthe valve 5? to move from the right to the left with respect to Figs. 2 and 7,

.te suiiicient to cause relatively rapid movement thereby disengaging the sealing cap 69 from the passage 56 and allowing rapid exhaust or fluid from the pressure chamber 18. It will be remembered that the piston i3 is under yielding bias of the several springs H to move'in a direction to exhaust fluid fromthepressure chamber it" or from the right to the left with respect to Fig. 2, and-movement in this direction causes the lever arms 25 to move the contraction ring Ed in a direction to close the jaws til of the collet 29.

In operation, it may be assumed that the fluid supply is cut off from the nozzle it and that spindle l and headl are under rotation at operating speed. With the pressure supply cut off, the springs ll have moved the piston is and means carried thereby to close the collet 29 over the workpiece. Opening of the valve allows fluid under pressure to pass through the nozzle it in a concentrated highly localized jetwhich impinges against the annular check valve 55 through the annular port ti, causing the valve 56 to become unseated only atthe point of impact Of the jet thereagainst. It will be appreciated that this point of'impact travels rapidly about the entire periphery of the valve 58 due to its rotation relative to the nozzle i i. In other words, the outer peripheral edge of the valve 58 assumes the position of a ripple or wave (see particularly Fig. 5), which ripple travels continuously about the periphery thereof under rotation of the head as long as the jet of the fluid is applied thereto. Normal seating of the valve 56 against the flange 59in addition topressure of the fluid built up within the passage 52 insures the sealing of the annular port 65 at all points about the periphery thereof other than that at which the jet occurs, thus insuring against any leakage of iluid out-, wardly through the port 5!. When sufficient pressure has been built up withinthe pressure chamber It, the movable wall element or piston 83 moves in a direction to release the collet 29 from the action of the contraction ring 3t. At this point, the workpiece may be removed and another inserted or material fed axially through the spindle l and collet it for machining thereof. As soon as the material has been properly fed through the collet 29, the valve 85 may be closed, thereby shutting off fluid supply to the nozzle. Bleeding of fluid through the orifice 52 to atmosphere rapidly causes a differential in pressure therefrom between the annular passage 52 and the pressure chamber it. As hereinbeore described, this differential in pressure allows the exhaust valve to open the passage 56, whereby to allow rapid escape'of the air or fluid from the pressure chamber it to atmosphere through the cavity ill under bias of the springs it upon the piston or movable wall element It. Of course, movement of the piston i3 caused by the springs I? again causes the contraction ring 3 3 to close the collet ZQ'upon the workpiece.

Our improved device has been thoroughly tested and found to be extremely eilicient and rapid in its operation. In fact, it has been found that our device may be operated entirely automatically by the use of an automatic valve in connection with an automatic screw machine with entirely satisfactory results.

Although the foregoing description is necessarily of detailed character, in order that the invention may be completely set forth, it is to be under-stood that the specific terminology is not intended to be restrictive or confining, and that various rearrangementsof-parts and modifica..-. tions of detail may be-resorted to without departing from the scope or spirit of the invention as herein claimed.

We claim:

1. In a fluid pressure-operated device, a rotary head structure defining a pressure chamber and a port through a wall thereof connecting said pressure chamber to atmosphere, an inwardlyopening check valve closing said port, and a nonrotary nozzle for directing a highly concentrated jet of fluid under pressure toward said head and the path of rotary travel of the check valveequipped port.

2. In a fluid pressure-operated device, a rotary head structure incorporating means for mounting on a rotary shaft, said head structure defining a pressure chamber and a port through a wall thereof connecting the pressure chamber to atmosphere, an inwardly-opening check valve closing said port and having a surface exposed to atmosphere through said port, and a nonrotary nozzle adapted for connection to a source of fluid under pressure and incorporating mounting means adapting it to be positioned to direct a highly concentrated jet of fluid toward the head and the path of travel of the check valveequipped port, said check valve opening under the impact of the jet when the pressure of the jet against the outer surface of the check valve exceeds the pressure against the inner surface thereof.

3. In a fluid-operated device, a head structure, said head structure defining a pressure chamber and an elongated port through a wall thereof connecting said valve chamber to atmosphere, an inwardly-opening check valve closing said port and having a surface exposed to atmosphere through said port, a nozzle adapted for connection to a source of fluid under pressure and incorporating mounting means adapting it to be positioned to direct a concentrated jet of fluid toward said head and check valve-equipped port, said head and said nozzle being mounted for relative movements one with respect to the other, said check valve closing said port at all points where internal pressure exceeds atmospheric pressure and having sufficient resilience to permit unseating at localized areas of much less extent than the length of the valve port, Whereby upon relative movement of said head with respect to said nozzle said valve will be opened only at the constantly changing localized area adjacent said nozzle by the concentrated fluid jet directed by said nozzle against said valve.

4. In a fluid pressure-operated device, a rotary head structure incorporating means for mounting on a rotary shaft, said head structure defining a pressure chamber and an elongated arcuate port through a wall thereof connecting said chamber to atmosphere, an inwardly-opening check valve closing said port and having a surface exposed to atmosphere through said port, and a non-rotary nozzle adapted for connection to a source of fluid under pressure and incorporating mounting means adapting it to be positioned to direct a concentrated jet of fluid to ward the head and the path of travel of the check valve equipped port, said check valve closing said port at all points where internal pressure exceeds atmospheric pressure and having suflicient resilience to permit unseating at localized areas of much less circumferential extent than the circumferential length of the valve port, whereby upon rotation of said head said valve will be opened only at the constantly changing localized area adjacent said nozzle by th concentrated fluid jet directed by said nozzle against said valve.

5. The structure defined in claim 4 in which said port and said valve are annular in shape and are concentric to the axis of rotation of said head.

6. In a fluid pressure-operated device, a rotary head structure incorporating means for mounting on a rotary shaft, said head structure defining a pressure chamber, an annular port in one wall thereof opening to atmosphere, and an inlet passage connecting said port to said pressure chamber, flexible inwardly-opening annular check valve normally closing said port and having a surface exposed to atmosphere through said port, a non-rotary nozzle adapted for connection to a source of fluid under pressure and incorporating mounting means adapting it to be positioned to direct a highly concentrated jet of fluid toward the head and the exposed surface of the check valve upon rotation of said head, said check valve closing the port at all points where internal pressure exceeds atmospheric pressure and having sumcient resilience to permit unseating at localized areas, whereby upon rotation of said head said valve will be opened only at the constantly changing localized area adjacent said nozzle by the concentrated fluid jet directed by said nozzle against said valve, a check valve in the passage between said first-mentioned check valve and said pressure chamber permitting passage of fluid only from said passage to said chamber, means for creating a differential in fluid pressure between said pressure chamber and said inlet passage, and an exhaust valve for said pressure chamber responsive to differential in fluid pressure between the pressure chamber and said passage.

7. In a fluid pressure-operated device, a rotary head structure incorporating means for mounting on a rotary shaft, said head structure defining a pressure chamber, an annular port in one Wall thereof opening to atmosphere, and an inlet passage connecting said port to said pressure chamber, a flexible inwardly-opening annular check valve normally closing said port and having a surfac exposed to atmosphere through said port, a non-rotary nozzle adapted for connection to a source of fluid under pressure and incorporating mounting means adapting it to be positioned to direct a highly concentrated jet of fluid toward the head and the exposed surface of the check valve upon rotation of said head, said check valve closing the port at all points where internal pressure exceeds atmospheric pressure and having sufficient resilience to permit unseating at localized areas, whereby upon rotation of said head said valve will be opened only at the constantly changing localized area adjacent said nozzle by the concentrated fluid jet directed by said nozzle against said valve, a check valve in the passage between said firstmentioned check valve and said pressure chamber permitting passage of fluid only from said passage to said chamber, means for creating a differential in fluid pressure between said pressure chamber and said inlet passage, said means including a bleeder orifice connecting said inlet passage to atmosphere, said head having an exhaust passage connecting said pressure chamber with atmosphere, and an exhaust valve in said exhaust passage responsive to diiferential in fluid pressure between said pressure chamber and said inlet passage to exhaust fluid from said pressure 76 chamber when the pressure in said inlet passage is less than the pressure within said pressure chamber.

8. In a device of the class described, a collet and a collet closer, said collet closer comprising a rotary head structure incorporating means for mountin on a rotary shaft, said head structure defining a pressure chamber and a port through a Wall thereof connecting the pressure chamber to atmosphere, an inwardly-opening check valve closing said port and having a surface exposed to atmosphere through said port, a non-rotary nozzle adapted for connection to a source of fluid under pressure and incorporating mounting means adapting it to be positioned to direct a highly concentrated jet of fluid against the exposed surface of said valve upon rotation of the head, said check valve opening under the impact of the jet when the pressure of the jet against the outer surface of the check valve exceeds the pressure against the inner surface thereof, one of the walls of said pressure chamber being movable with respect to the others thereof, a contraction ring mounted concentrically on said collet for axial sliding movements and adapted to contract and release the jaws thereof under said sliding movements, and means operatively connecting the movable wall of said pressure chamber with said contraction ring.

9. In a device of the class described, a collet having a tapered peripheral outer face, and closer mechanism for said collet, said closer mechanism comprising a head structure incorporating means for mounting on a rotary shaft, said head structure defining a pressure chamber, an annular port in one. wall thereof opening to atmosphere, and a passage connecting said port to said pressure chamber, a flexible inwardly-opening annular check valve normally closing said port and having a surface exposed to atmosphere through said port, a non-rotary nozzle adapted for connection to a source of fluid under pressure and incorporating mounting means adapting it to be positioned to direct a highly concentrated jet of fluid toward the head and the exposed surface of the check valve, said check valve closing the port at all points where internal pressure exceeds atmospheric pressure and having sufficient resilience to permit unseating at localized areas,

whereby upon rotation of said head said valve will be opened only at the constantly changing localized area adjacent said nozzle by the concentrated fluid jet directed by said nozzle against said valve, one of the walls of said pressure chamber being movable with respect to the others thereof, a contraction ring axially slidably mounted on said collet and having a tapered portion engageable with the tapered peripheral outer surface of said collet, whereby to contract the jaws of said collet and release the same upon axial movements of said contraction ring with respect to said collet, and means operatively connecting said contraction ring with the movable wall of said pressure chamber.

10. The structure defined in claim 9 in which said head is provided with an exhaust passage connecting said pressure chamber with atmosphere and a restricted bleeder orifice connecting said inlet passage with atmosphere, and in further combination with an exhaust valve in said exhaust passage responsive to differential in fluid pressure between the pressure chamber and said inlet passage.

11. In a fluid pressure-operated device, a rotary head structure incorporating means for mounting on a rotary shaft, said head structure defining a pressure chamber and an elongated arcuate port through a wall thereof connecting the pressure chamber to atmosphere, an inwardly-opening check valve closing said port and having a surface exposed to atmosphere through said port, a non-rotary nozzle adapted for connection to a source of fluid under pressure and incorporating mounting means adapting it to be positioned to direct a highly concentrated jet of fiuid toward the head and the exposed surface of said valve, said check valve opening under the impact of the jet when the pressure of the jet against the outer surface thereof exceeds the pressure against the inner surface thereof, one of the walls of said pressure chamber being movable with respect to the others thereof, means biasing said movable wall in one direction, and means for controlling the flow of fluid through said nozzle and said valve, whereby to move said movable wall against the bias applied thereto, said port and valve being angular in shape and concentric with the axis of rotation of said head.

HARRY J. SADLER. ERNEST E. COOK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,291,147 Carlsen July 28, 1942 2,383,094 Walder Aug. 21, 1945 2,392,999 Redmer Jan. 15, 1946 2,393,458 Cook Jan. 22, 1946 2,454,593 Chalicarne Nov. 23, 1948

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