US2616398A

US2616398A - Apparatus for controlling air cylinder stroke motions

Info

Publication number: US2616398A
Application number: US21665A
Authority: US
Inventors: Company Manufacturers Trust
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-04-17
Filing date: 1948-04-17
Publication date: 1952-11-04
Anticipated expiration: 1969-11-04

Description

G. w. EMRICK Nov. 4, 1952 APPARATUS FOR CONTROLLING AIR CYLINDER STROKE MOTIONS 3 Sheets-Sheet 1 Filed April 1'7, 1948 wig 4 m w Z W// IIIIUIIIIIIIIIIIIIII INVENTOR GEORGE W. EMRICK ATTORN Y NOV. 4, 1952 I w, EMR|K 2,616,398

APPARATUS FOR CONTROLLING AIR CYLINDER STROKE MOTIONS Filed April 17, 1948 3 Sheets-Sheet 2 59 I I 26 O :2

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I INVENTOR GEORGE W. EMRICK v ATTORNEY G. W. EMRICK Nov. 4, 1952 APPARATUS FOR CONTROLLING AIR CYLINDER 'STROKE MOTIONS Filed April 1'7, 1948 3 Sheets-Sheet 3 INVENTOR GEORGE W. EMRICK ATTORNEY Patented Nov. 4, 1952 UNITED STATES PATENT OFFICE APPARATUS FOR CONTROLLING AIR CYLINDER STROKE MOTIONS George W. Emrick, Forest Hills, N. Y.; Manufacturers Trust Company executor of said George W. Emrick, deceased Application April 17, 1948, Serial No. 21,665

10 Claims.

This invention relates to apparatus employing an air cylinder, with a piston operating in the cylinder with automatic means controlling the stroke or movement of the piston in the cylinder in controlling various types and kinds of feed motions in machines of various kinds. Still more particularly, the invention deals with apparatus of the character described wherein a solenoid actuated valve is employed for automatically controlling air flow to the cylinder in control of the stroke or movement of the piston in the cylinder. Further, the invention deals with apparatus of the character described having means controlling the speed of the piston stroke so as to provide in a definite piston stroke or movement, piston operation at two different speeds.

broken away.

Fig. 2 is a plan view of the structure seen in Fig. 1, showing the casing in section, with part of the structure broken away.

Fig. 3 is a section on the line 3-3 of Fig. 2, on an enlarged scale and omitting part of the construction.

Fig. 4 is a section on the line 4-4 of Fig. 3, showing only the valve mechanism, and with part of the construction shown in elevation.

Fig. 5 is a section substantially on the line 5-5 of Fig. 4, with part of the construction shown in elevation.

Fig. 6 is a section on the broken line 6-6 of Fig. 4, showing the valve in a different position, with parts of the construction broken away.

Fig. 7 is a section substantially on the line 11 of Fig. 5.

Fig. 8 is a partial section on the line 8-8 of Fig. '7.

Fig. 9 is ase'ctional plan view through a casing of an auxiliary solenoid mechanism, showing the mechanism therein and illustrating part of the main casing in elevation and omitting part of the structure.

Fig. 10 is a sectional view through the structureshown in Fig. 9, the section being substantiallyon the line l0-l ll of Fig. 11'.

the lower wall of the workpiece. time given above are examples of the many uses 2 Fig. 11 is a section substantially on the line Hll of Fig. 10.

Fig. 12 is a diagrammatic view of the several mechanisms of the apparatus, indicating the wiring diagram and the switch control mechanism; and

Fig. 13 is a view looking in the direction of the arrowv l3 of Fig. 1, showing the upper portion of the valve casing, and part of the solenoid mounting thereon.

In machines or apparatus of various kinds and classes, it has been desirable to employ means to control stroke motion of an operating part of the machine. For example, in a drilling machine, it is desirable to control the stroke of a drill in drilling the depth of cut in a workpiece, and at the same time, to control speed of motion of the drill through operation of an air cylinder. In certain uses of the control apparatus, it is also desirable to operate, for example, a tool at a relatively high speed in one predetermined move ment of the tool and then to check or retard the motion of the tool in one period of the cycle of operation. To illustrate, in operating a drill, through a workpiece when the drill is to pass through the full depth or thickness of the workpiece, it is desirable to slow the speed of the drill feed as and when the drill is about to pass through The illustrato which apparatus of the kind under consideration can be applied.

In the several views, Figs. 1 to 11 inclusive, all wiring has been eliminated for sake of clarityin the showing, and in Fig. 12, the wiring diagram is shown to illustrate the electrical means of the apparatus. In this figure, the several parts of the apparatus and the switch controls thereof are shown diagrammatically.

.In practice, I provide a suitable frame or housing for support of my improved control apparatus in conjunction with a machine of any type or kind. This frame or housing is generally identified by the reference character 20, and includes a mounting end portion, part of which is shown at 2|, and a box-shaped casing part 22, in which the cylinder 23, two solenoids 2425 and the control valve mechanism 26 are arranged, as will appear from a consideration of Figs. 1 to 3 inclusive of the drawing. At one side of the casing 22 of the frame 20, is a supplemental casing 21 in which a supplemental or auxiliary solenoid 28 is arranged.

The cylinder 23 in the construction shown, comprises a tubularmember 29, note Fig.3, to

the ends of which are secured upper and lower end plates 36-3l, these plates being bolted together by four corner bolts 32, two of which are shown in Figs. 1 and 9 of the drawing. The end plate 36 has an intake port 33 which also acts as an exhaust, whereas the end plate 3| has a similar port 35. Slidably mountedin the plate 3 l, and suitably sealed therein, is a piston rod 35, carrying at its upper end, a suitable composite piston structure 35. The rod 35 externally of the piston may be coupled with any type or kind of tool or any mechanism of a device, actuation of which is to be controlled by the apparatus.

Noting Fig. 12 of the drawing, it will appear that an arm 37 is coupled with the rod 35, the arm being freely guided in an extension 38 on the frame 23, through a guide finger 39.

The valve casing 26 is suitably supported on two of the bolts 32 and arranged within the frame or the casing 22 thereof. Fixed within a transverse bore 46 of the valve casing 26, is a sleeve or bushing 6| in which a valve 62 is mounted for rotary reciprocating motion. The valve has'trunnion ends 4364 to which are secured gears 65-46, as clearly seen in'Fig. 4 of the drawing. The valve casing 26 has a single air admission port 41, which may be termed the intake. A pipe 48 is coupled with this port, and with which an air line from a source of high pressure air supply is adapted to be connected. This supply is not shown, as it is'well known in the art.

The port 41 opens into two branches 46-56, as will clearly appear from a consideration of Fig. 4 of the drawing, and communicating with these branches, the sleeve or bushing 6| has registering ports l52. Directly opposed to the ports 5 l52, the sleeve or bushing has other ports 53-56, the latter opening into a horizontal port 5", with which a vertical port 56 communicates, the port 55 being plugged, as seen at 5?, note Fig. 6. The port 53 opens into a horizontal port 58, with which communicates a downwardly extending port 53, the port 53 being also plugged, as seen at 66.

The port 59 is placed in communication with the intake passage 36 at the bottom of the cylinder through a series of pipe or tube fittings, as at 6!, note Fig. l of the drawing, so that air under pressure admitted to the

ports

53, 53 and 59 will extend to and enter the lower end of the cylinder 29 to move the piston 36 upwardly, thus this will be regarded as the upstroke. All reference to up and down is with respect to showing in the accompanying drawings, itbeing understood that the apparatus can be mounted in any desired position.

Coupled with the passage 56 are pipes and fittings, generally identified as 62, in Fig. 1 of the drawing to place the port 56 in communication with the intake exhaust 33 at the upper end of the cylinder, so that in the discharge of air under pressure from the

ports

54 and 55, will be directed through th pipes and fittings 62 to the port 33, causing the piston 36 to move downwardly in the cylinder 23. To control the upward and downward stroke movement of the piston 36, the valve 52 is given rotary oscillatory movement in order to place the ports 5! and 53 and 52 and 54 in communication. The valve 42 has two sets of substantially Y-shaped passages, one of which is clearly shown in section in Fig. 6 of the drawing. These passages will be generally identified by the

reference characters

63 and 64, the passage 64 being shown in transverse section in Figs. 3 and 6 ofthe drawing. The passage 63 is shown in dotted lines in its relationship to the passage 64, in Fig. 6. The passage 63, in Fig. 6, is shown in position placing the passages 5i and 53 in communication, thus admitting air, under pressure, to pass into the passage '59 and thus into the lower end of the cylinder 29 to move the valve into raised position. When the passage 63is in the position shown in Fig. '6, the passage 64 is in position exhausting air from the upper end of the cylinder by placing

passages

55 and 54 in communication with an exhaust passage 65 in the sleeve or bushing 4|, and registering with an exhaust passage 66 in the valve casing 26, as clearly seen 'in Fig. 6 of the drawing. Another exhaust passage 61 is arranged in the sleeve or bushing 4| and registers with another exhaust passage 68 in the casing 26.

The passage 66 registers with a horizontal passage 69 in which an adjustable needle valve 16 is arranged, and another adjustable needle valve H is arranged ina similar passage'l2-which communicates with the passage 66 through-a vertical passage 73. Another horizontal passage 14 is disposed above the passage 12 and also-opens into the vertical passage 13 and an automatically actuated sliding needle valve 15 is arranged in the passage 14, the valve 15 operating in a suitable stuifing box 16, note Fig. -8. Both passages 69 and 12 are placed in communication through a passage ll, note Fig. 7, and register'with a communication exhaust 18, with which a pipe 194s connected, and this pipe may extend to any suitable position.

From the foregoing, it-will be apparent that when the Y--shaped port is in the full lines position shown in Fig. 3 of the drawing, the companion port 63 is in the exhausting position, so as to exhaust air from the bottom of the cylinder as the piston 36 is being moved downwardly by air under pressure passing through the ports 5264 and 56-55 and thus into the port 33, as will be apparent. Considering Figs. 6, 7, and 8 of the drawing, it'will be apparent that, many of the ports are shown as plugged at their outer ends and no specific description will be given of this structure as it is purely a mechanical expedient in showing the mannerof forming and intercommunicating the separate portsand passages through the valve.

To control operation of the valve 42,- the

solenoids

24 and 25 are employed, the cores of these solenoids terminating at their'lower ends in racks 39-6l, which are slidably mounted in the valve casing 26, and operate in connection with the gears 45-46 respectively. One of these racks and its engagement with the companion gear is clearly shown in Fig. 5 of the drawing. In the construc-. tion shown, each core hasan enlarged-forked end, one of which is indicated at 82, in Fig. 5 of the drawing and the racks are coup-led with the core through the medium of a pin'33, The hanging or mounting of each rack 366 lis the same, except that one rack is disposed at one side of theaxis of the valve 42 and the other on the opposite-side, as will appear from a consideration of Fig. 4 of the drawing. Both racks are in constant engagement with their respective gears, and a balanced effect is provided, inthat upward movement of one rack-automatically transmits downward-movement to the opposed rack. In other words, as each solenoid is electrically actuated, its core is drawn upwardly to transmit one rotary motion to the valve, andthe other solenoid will reverse these rotary actions,'thus moving the valves from theposition showniniFig 3, to:that

shown-in Fig. 6, in the two stages of operation of the'apparatus. The forked ends of thecore include-a cross-head portion 84,. one of which is shown in end elevation in Fig.v 5, and these cross heads striking the lower portions of the solenoid windings, limit and check upward stroke movement of each core and correspondingly, the movement of the racks. It will thus be apparent that drilling of the ports in the valve will be made preferably in assemblage of the valve and by movement of the racks and cores to the limit of their upward movement, as will be apparent. In-this way, positive registration and timing will be-provided.

.Considering Fig. 4.- of the drawing it will appear that'the bore 49 is closed and sealed by suitable end plates 8586, thus providing a seal for lubrication in operation of the valve mechanism. It is also desirable that the fit of the valve 42 in the bushing 4| be extremely snug, so as to prevent any possible air leakage.

The needle valves Hl1l extend outwardly through the casing 22 and have knurled heads HY-4| by means of which these valves may be manually adjusted to control air flow through the respective exhaust passages, and thereby control speed of actuation of the piston 39 in the initial up and down movement thereof. For illustrative purposes, the down movement may be said to be the feed movement, and thus the feed of a tool to be actuated by the mechanism in engagement with a workpiece can be controlled by regulating the exhaust of air from the lower end of the cyllnder23. Means is also provided in this down or feed stroke to provide-what might be termed a delayed action or slower feed motion, which is accomplished through the sliding needle valve which is adapted to choke-off the passage 13 immediately above the needle '52, as will clearly appear from a consideration of Fig. 8 of the drawing. This latter control is an auxiliary control, and thus may or may not be employed in different types and kinds of work. However, the solenoid 28 is provided for control "of the needle valve 15. The core of the solenoid 28 has a cross head 8?, generally similar to the cross head 84. To this crosshead is attached a depending arm 38, with which'is adjustably coupled an actuating rod 89 having a head 99 which is adapted to strike against a head 9! at the outer end of the-needle valve 15. A spring 92 normally urges the rod 15 outwardly, or in other words, supports the same in inoperative position, and this spring also retains the solenoid core in an inoperative position. However, when the solenoid 28 is energized, the core isdrawn inwardly, moving the cross head 8'! 'to the'right,'as' seen in Fig. 11, correspondingly moving the rod 89 and the needle valve '15. It will be understood that the adjustment of the rod 89 will control the degree of inward movement of the needle valve in controlling the degree of choking the port 73. In Fig. 8 of the drawing,

the valve lii may be said to assume a partially springs have been omitted from the other showlngs for sake of clarity.

Turning now to the diagrammatic illustration of Fig. 12 of the drawing, here certain parts of the control mechanism are indicated in outline form, together with the wiring diagram. On the arm 31 is arranged an adjustable trip finger 95 adapted to actuate a micro or other switch 96 in circuit with the solenoid 24, so that as the piston 36 reaches a predetermined up position, the switch 96 will close the circuit to the solenoid 24, causing the rack to move upwardly and the rack 8| downwardly, thus moving the valve 42 into the position shown in Fig. 3, allowing air to be admitted to the upper end of the cylinder'for down movement of the piston 36. Also carried on, and by the arm 31, is a screw rod 91 having adjustable trip nuts 98 r adapted to I operate a switch actuator sleeve 99 slidably mounted in the extension 38 of the frame. A spring I99 normally supports the sleeve 99 in raised position. However, as the piston 36 moves downwardly, the nuts 98 will strike the upper end of the sleeve and start downward movement of the sleeve. The instant this movement takes place, another micro or other switch IOI will be actuated through movement imparted through a switch actuator 12 which is moved by the bevelled surface I93 on the sleeve. If the switch 93 is in closed position, the solenoid 28 will be operated to move the needle valve I5 into its control position. thus retarding the speed of downward movement of the piston 36.

Upon completing the desired downward stroke, another bevelled surface H14 on the sleeve will strike a pin 195, operating this pin toactuate another micro or other switch I96 which will close the circuit to the solenoid 25, causing the rack 8| to be moved upwardly, thus moving the valve 42 to the position shown in Fig. 6. In this latter position of the valve 42, air is admitted into the.

cylinder in the up and down movement of the piston, the speed at which the piston travels in the cylinder is controlled, the heads 10'--1I' being accessible for manual adjustment at all times.v

It will also be understood that the showing in Fig.

12 with respect to the sleeve 99 and the mecha-- nisms associated therewith is purely diagram-v matic and illustrates generally the idea of a twostep or two-station control, the relative distances of travel between the stations may be varied. However, in such work, as control of the operation of a drill, the control of last stages of drill operation are relatively slight and this type of illustra tion is diagrammatically shown in Fig. 12.

While the circuit wiring is quite apparent, it might briefly be described in stating that wires HIT-I08 represent a source of electrical supply. The circuit to the solenoid 24 is controlled through branches I09, leading to the switches 99, I ID from the switch to the solenoid and I l I from the solenoid to the wire I08. The circuit to the solenoid 25 is controlled by the wire I I2 extending to switch I06, while the wire H3 from the switch I06 extends to the solenoid 25 and wire H4 from the solenoid to the wire I 08. Circuit to the solehoid N ls-controlled by wire H 'leadingrto: switch I0 I, then through wire I lfi fromswitch. I.0.l.:to: the solenoid- 28 through switch 93 and then by. wire H! from solenoid 2-8 to wire 38;

I Fig. 13 has been shown in order to illustrate the mounting of the solenoids upon the upper portion of the valve-casing 26. This valve casing has-at-its ends, upwardly extending lugs H3 and a center lug l 19 with whichare coupled upwardly extendingmetal straps, all indicated by thereference-character E29. To these straps'are attached the side members of the U-shaped frames 2425- of thesol'enoidsZA-JE. Also illustrated in Fig. 13, is the forked-end 82' of the core ofth'e solenoid 24, as'wellas thecross head-8 t. The cross head 8% is in the raised position, whereas the-cross head 84i-s in the lowered position, thus in Fig. 13, the rack-86 is in the raised position and the rackBl in the lowered position. The straps I20 guide the cross heads in their movements; At'83 is-shown the pin which couples the rack 88 with the forked portion B2 of the crosshead84';

By providing the balanced action between the solenoids 2E25 and the mechanism thereof, the apparatus can be mounted and utilized 'inany position without danger of faulty operation due to unbalanced conditions of the operating part. Furthermore, this balance provides an ease of action in actuation'of the valve. The total rotary oscillating motion of the valve is between the two positions shown inFigs. 3 and 6 and by providing the wide type'passages (W-66, automaticmovement from the intake to exhaust positions is provided; one passage of the valve exhaustingwhile the other passage is in the intake position. It will also be apparent that a very compact control, unit'or apparatus is provided which may be readily attached to'or mounted in conjunctionwith machinesof any type or kind incontrolling operation of a predetermined member of the machine or a tool driven by the machine.

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

1. An apparatus of the character described comprising an air cylinder, a piston operating in the cylinder and including an operating rod extendingthrough one end of the cylinder, a'val've controlling admission of air under pressure to opposed ends of the cylinder and the exhaust of airfrom said ends of the cylinder, said valve being arranged in a valve c'asing,ggears on opposedends' of saidvalve within said casing, a'pair of racks slidably mounted in the ends of the casing and operatively engaging said gears for imparting rotary'reciprocating motion to the valve, means 'adjustable in the casing controlling the speed of travel of the piston in the cylinder in both directions, and a pair of solenoids for'operating said racks in controlling operation of said'valve.

2. An apparatus of the character, described comprising an air cylindena piston operating-in the cylinder and-including anoperatingrod extending'through one end of the cylinder, a valve controlling admission of air under pressure to opposed ends of the cylinder and the exhaust'of air from said ends of the cylinder, said valve being;

arranged in a-valve casing, gears on opposed ends of said valve within said casinga pair'of racks slidably mounted in the ends of the casingand operatively engagingsaid; gears for imparting rotary reciprocating motion to the-valve,- means adjustablein the casing controlling the, speed of' travel ofjthe piston in the cylinder in both directions; a pair ofsolenoids for operating'saidracks' in controlling: operation: of saidvalve,andiadjuste able; meansin circuit. with; said. solenoids controlling the: stroke of the piston in:the cylinder..

3.. An. apparatus .of the. character described comprising. an air' cylinder, a piston operating .in the. cylinder and including .an. operating rod ex tending throughone end of the. cylinder, .a valve controlling admission of air under pressure to opposedends of the cylinder. and the exhaust. of air from said'endsof the cylinder, said valve being arranged in avalve casing, gears on opposed. ends of. said valve withinsaidi casing, apair of racks slidably mountedin. the: ends. ofv the casingiand operatively engaging said gears for impartingrotaryreciprocating'motion to the:valve,,.means.adjustable in thexcasing controlling the. speed; of travel of thepistonin the cylinder in. both direce tions, a pairv of:solenoids.ior operatingsaidracks in controlling, operation of said valve, adjustable meansv in circuit withlsaidi solenoidsv controlling the stroke of the pistonin'the'cylinder, and means comprising another movable element in-the valve casing for varying thev speed of travel of the piston in the cylinder in one stroke motion thereof.

4. An apparatus of. the character described comprising anair cylinder, a; piston operating. .in the cylinderan'd including an-operatingrodextending through oneend of thecylinder, a valve controlling admission ofv air under pressure to opposed ends of the cylinder and. the exhaustof air from said ends of the cylinder, said valve being arranged in a valve. casing, gears. on opposed ends of said valve within said casing, a pair. of racks slidably mounted in theends: of the casing and operatively engaging said gears for impartingrotary reciprocating motion to the va1ve,,meansad.- justablev inthe casing controlling the speed .of travel of the piston in thecylinder in both directions, a pair of solenoidsfor operating said racks in controlling operation of said valve, adjustable means in circuit with said solenoids controlling the. stroke of the piston in the cylinder, means comprising another movable elementin the valve casing for. varying the speed of travel of the piston in the cylinder in one stroke motion thereof, and a solenoidcontrolling.the, operation of said last named element.

5. In drivecylinders of the character described, acontrol valve, saidvalvelcomprising a casing,.a bushing, in said casing. having fixedv ports communicating with intake and discharge passages in the valve casing, a valve mounted in the bushing and having passages adaptedjto register with intake and discharge passages of the bushing and casing, the valve havinggears, at end portions thereof, racks slidably mountedfin thecasing and operatively engaging said. gears, said gears and racks being adapted to impart-rotary reciprocating motion to the valve in movingthe ports thereof' into intake and exhaust positions, a pair'of solenoids on the valve casin and coupled with said racks for actuating the valve, and automatically actuated means controlling operation of the solenoids in controlling operation of a piston'in the drive cylinder in both directions.

6. In'drive cylinders of the character described, a control valve, said valve comprising a casing, a bushing in said casing having fixed ports communi-cating with intake and'discharge passages in the valve casing, a valve mounted in the bushing and having passages adapted to register with intake and discharge passages of the bushing and casing; the valve having gears at end portions thereof, racksslidably mounted in the casing and operativelyengaging said gears, said gears and racks being adapted to impart rotary reciprocating motion to the valve in moving the ports thereof into intake and exhaust positions, a pair of solenoids on the valve casing and coupled with said racks for actuating the valve, automatically actuated means controlling operation of the solenoids in controlling operation of a piston in the drive cylinder in both directions, the intake and exhaust passages being arranged in two series, and the valve having two ported sections operatively engaging the series of ports in control of the intake and exhaust of said cylinder.

7. In drive cylinders of the character described, a control valve, said valve comprising a casing, a bushing in said casing having fixed ports communicating with intake and discharge passages in the valve casing, a valve mounted in the bushing and having passages adapted to register with intake and discharge passages of the bushing and. casing, the valve having gears at end portions thereof, racks slidably mounted in the casing and operatively engaging said gears, said gears and racks being adapted to impart rotary reciprocating motion to the valve in moving the ports thereof into intake and exhaust positions, a pair of solenoids on the valve casing and coupled with said racks for actuating the valve, automatically actuated means controlling operation of the solenoids in controlling operation of a piston in the drive cylinder in both directions, the intake and exhaust passages being arranged in two series, the valve having two ported sections operatively engaging the series of ports in control of the intake and exhaust of said cylinder, and adjustable means on the valve casing controlling the exhaust from the cylinder in controlling the drive action of the piston in the cylinder.

8. In apparatus employing a drive cylinder for controlling the feed and operation of a tool or the like, a piston in said cylinder, the opposed ends of the cylinder having means for admitting and discharging a pressure medium in the drive of the piston in both directions in the cylinder, a valve casing, an intermittently reciprocating valve in said casing, means slidably mounted in said casing for actuating said valve, automatically actuated electrical means for actuating said last named means for controlling intake and discharge of the pressure medium with respect to opposed ends of the cylinder by movement imparted to said valve, means comprising manually adjustable devices controlling the circuit to said electrical means for actuating said valve to control travel of the piston in said cylinder in both directions, manually adjustable means in the valve casing controlling discharge of the pressure medium from both ends of the cylinder in controlling speed of travel of the piston in both directions in the cylinder, a pair of gears and racks for actuating said valve, and said electric means comprising a pair of solenoids actuating said racks.

9. A valve mechanism comprising a casing having ports, a valve rotatably mounted in said casing and having two sets of ports for registering with the ports of said casing, a gear and rack structure at each end portion of said casing, each gear and rack being adapted to impart rotary reciprocating motion to the valve in moving the two sets of ports of the valve into predetermined positions of registration with the ports of said casing, and means simultaneously operating said racks in opposite directions in the rotation of said valve.

10. A valve mechanism comprising a casing having ports, a valve rotatably mounted in said casing and having two sets of ports for registering with the ports of said casing, a gear and rack structure at each end portion of said casing, each gear and rack being adapted to impart rotary reciprocating motion to the valve in moving the two sets of ports of the valve into predetermined positions of registration with the ports of said casing, means simultaneously operating said racks in opposite directions in the rotation of said valve, and means adjustable in the casing controlling the area of predetermined ports therein.

GEORGE W. EMRICK.

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

UNITED STATES PATENTS Number Name Date 967,565 Rohan Aug. 16, 1910 1,001,565 Lininger Aug. 29, 1911 1,256,602 Slaw Feb. 19, 1918 1,724,635 Bath Aug. 13, 1929 1,817,180 Drake Aug. 4, 1931 1,938,762 Haas Dec. 12, 1933 2,157,240 Keel May 9, 1939 2,176,985 Arms Oct. 24, 1939 2,283,397 Tucker May 19, 1942 2,285,968 Harrington June 9, 1942 2,319,125 Grote May 11, 1943 2,384,760 Matulionis Sept. 11, 1945 2,388,369 Shendrick Nov. 6, 1945 2,433,471 Mayer Dec. 30, 1947