US2404262A - Servomotor and control - Google Patents

Description

.1.,y E. WHITFIELD 2,404,262

SERVOMOTOR AND CONTROL Filed sept. 27, 1945 s sheets-'sheet 1 July 16, 1946.

Patented July 16, 1946 UNITED STATES 'PATENT oFFlCE sERvoMoToR AND CONTROL Joseph E. Whitfield, Hamilton, ohio Application September 27, 1943, Serial No. 503,955 14 claims. (ci. `eso- 16) This invention relates generally to expansible chamber motors and more particularly to a fluid pressure actuated servomotor for operating apparatus that is rotated in opposite directions to perform a function, such .as operating a reversing valve.

This servomotor is adaptable tovmany different applications but was specifically designed for operating a reversing valve which controls the flow of scavenging or supercharglng air produced by a screw blower for a reversible Diesel engine wherein the blower is driven directly from the shaft of the engine.

The principal object of this invention is' the provision of a servomotor in which the diminishing chamber ahead of the vane is supplied with a charge of the motivating fluid under pressure to retard the vane adjacent the end of its stroke.

Another object is the provision of apparatus for supplying from the expanding chamber a charge of the motivating uid under pressure to the diminishing chamber ahead of the vane to cushion the movement of the vane intermediate of or adjacent the end of its stroke.

Another object is the provision of apparatus for supplying a charge of compressed fluid in the diminishing chamber of a servomotor and for venting the fluid under pressure in the expanding chamber to cushion the movement of the vane toward the end of its stroke.

Another object is the provision of a vane type expansible chamber servomotor'wherein the vane functions as a valve at the end of its stroke for controlling the passage of the motivating fluid under pressure.

Another object is the provision of a Diesel engine reversing control circuit which includes a servomotor that operates a reversing valve and then completes the control circuit to start the engine in the opposite direction.

Another object is the provision of a method for charging the expanding chamber, charging the diminishing chamber, and discharging the eX- panding chamber in sequence of a servomotor intermediate of its complete operating stroke.

Other objects and advantages will be apparent from the disclosure shown on the drawings and in the following description and claims:

lin theY accompanying drawings a practical embodiment illustrating the principles of this invention is shown wherein:

vertical section of the servomotor,

2 v Fig. 3, is a view in horizontal section of the servomotor showing the vane in one extreme position.

Fig. 4 is a view similar to Fig. 3 showing the vane in a first intermediate positionlr Fig. 5 is a View similar to Fig. 3 showing the vane in a second intermediate position.

Fig. 6 is a view similar to Fig. 3 showing the vane in the other extreme position.

Fig-'7 is a diagrammatic view of a Diesel engine with reversing control circuit.

Fig. 8 is a vertical sectional View 'of the servomotor showing a portion of the vane andhousing with their ports in registration.

Referring to Figs. 1 and 2 of the drawings, the housing 9 of the servomotor is provided with a cylindrical chamber II which is' closed at the top by the removable cover l 2 and 'at the'bottom by the integral end wall I3. The cover I2'and the wall I3 are provided with axially aligned bearings I4 in which the servomotor shaft 'I5' is journaled. The shaft I5 is coaxial with the cylindrical chamber I I and extends above the "cover I2 lto receive the hand operating arm `I6 forman'- ually rotating the servomotor shaft.

The lower side of the housing 9 and wall I3 is provided with an annular seat I'I arranged to fit the mating seat I8 which defines the upper' opening of the adapter casting I9 which in turn has a stepped connecting t with thereversingvalve housing 20 which encloses a reversing valve that is employed in combination with the screw blower to change the direction of flow of scavenging air to a Diesel engine when the'latter is re'- versed. The valve may be seenv in Patent No. 2,345,780, issued April 4, 1944. 'Ihel lower end of the shaft I5 is provided with the coupling member 2l which is arranged to receive the'r end of the upper gudgeon 220i the valves The cylindrical chamber II in the servomotr housing is provided with a removable sector or stationary abutment 23 which is fastened 'tothe housing by the bolts 24 as shown in Fig. 2. The v outer cylindrical surface of the stationary abutment mates with the cylindrical wall ofthe chamber II and the inner' cylindricaly surface mates with the surface of the vane 'hub125`as against the cylindrical surface of the hub 25 by means of the coil springs 2B which are inserted in the tapped holes that receive the bolts 24, which holes are aligned with the slot.

The wearing face and the upper and lower ends of the shoe 26 are grooved asindicated at 30 and small holes 3I connect the face of the long groove 35 with the/bottom of the slot 21.

` A passageway 32through the wall I3 of the hous-` ing connects the `lower end of the groove 30 with theinterior of the reversing valve housing 20.`

The passage 32 could extend to the atmosphere. However if compressed air is employed as the motivating fluid for the servomotor, and the reversing valve controls the flow of air under a relatively low pressure, any leakage or discharge of air passed Vto the abutment will flow yto the chamber in the housing and cannot accumu-- late on either side of the abutment but seeks'the low pressure area through these passages.

rThe vane 33 with the abutment 23 occupy substantially one-half the volumeof the chamber I I and the hub of the vane is splined .on the shaft I5 as shown in Fig. 2. The outer arcuate surface of the hub and vane have a slight running clearance `with the abutment andthe walls of the chamber II which prevents wear between these surfaces having relative rotary movement.

may kenter the valve mechanism through theright port 5I moving the valve 52 to the left permitting the air to continue flowing through the port 53 that passes through the right end vof the stationary abutment 23'into the chamber I I in back of the vane 33 as shown in Fig. 3. The fluid un-V der pressure moves the. vane 33 to the position shown in Fig. 4 Where yit may flow into the recess 41 and through the port 45'into thecharging chamber -44 within the vane.

The fluid under pressure continues to move the vane in a counterclockwise direction until it reaches the position shown in Fig. 5 where the charge of fluid under pressure within the charging chamber 44 escapes through the port 45 )and the Yrecess 48 to the chamber II on the leading side of the vane. At this instant the diminishing This .clearance also permits the motivating or en Y trapped fluid to ow orvexhaust therebetween and prevents the motivating fluid from reaching theleading' face of the vane and thus check its movement. Thus the running clearance, which exhausts the fluid under pressure from either side of the vane,'is 'a defined orifice the size of which determines the rate of discharge. A sloping or triangularly shaped radially extending slot., 34 is provided in the center ofthe vane and is arranged to receive a similarly shaped shoe 35.

This shoe'is provided with a plurality of pockets for receiving the. coil springs 35 which'bear against theb'ottom of the slot 34 and force'one leg surface of the triangular shaped shoe 35 into engagement with the under surface'of the cover I2 and the otherleg surface into engagement withfthe cylindrical wall of the chamber-,I I.. A :groove 31 is centered in the wearing faces of the surfaces of the triangular shoe 35, which groove matches with similarY grooves in the upper and lower surfacesof the vane. The holes 38 through the shoe 35 connect the groove 31 with the bottom of the slot 34. The inner end of the groove 31 .in the bottom face of the vane is connected c to the enlarged bore forming an annularchamber 40 adjacent the shaft I5. A hole 4I connects.

the chamber 40 to the axial passageway 42 vin the lower end of the Vshaft I5 which in turn is connected with the radial passage 43. Any uid flowing to theV center of the vane may leak into the groove 31 of the shoe and mayY thus. flow` through the passages 4I), 4I, 42and 43 into the chamber of thevalve housing 20. Twodirect passageways for the flow of fluid are Yprovided between the servomotor chamber I I to the valveA housing 20. Y

'I'he vane 33 is hollow having the charging chamberf44 which'is provided'with ports 45, 46 adjacent the ends thereof. These 'ports are in 'the Vupper part '.of the vane andare arranged to connect the charging chamber with the chamber II through recesses'41 and 48 in thecylindrical Wallof the chamber II, as shown in Fig. 8.

Y The Lservomotor is controlled by the valve mechanism secured to the front'of the hous ing 9. As shown in Figs. 3 `to 6, compressed` air portion of the chamber II is substantially equal in volume to .the charging chamber 44 in the vane. Thus aportion of the charge of fluid under pressure fills the diminishing portion of the chamber II and retards the movement of the vane'in 'accordance with the differential in pressure on each side of the vane less the forceV of inertia of the latter. 'Y

The vane continues to move at a decreasing speed until it engages theleft side of the stationa'ry abutment 23 as shown in Fig. 6. It will benoted that the port 54 is closed by the valve 52 rsothe fluid in frontof the moving vaneV is being continuously compressed even though a charge of fluid under pressure has been added thereto. Thus the fluid seeks its escape from the Y diminishing portion of the chamber II to the low pressure areas by means of rthe grooves 35 and 31.in the shoes 26 and 35 of the stationary abutment and vane respectively. These leakage paths act asa choke and thus cushion themovementr of the vane toward the end of yits stroke. y

Just before the vane is about to strike the stationary abutment 23 the trailing edge of the vane uncovers one ofthe ports` 55 or 56, depending on the direction of movement of the vane. Thus the vane acts as a valve in conjunction with these ports. IThese ports are'in the 'lower part of .theI chamber II as indicated in Figs. 2 and 8 and do not'matewith the ports of the charging y chamber in thel vane. As shownr Vin Fig/.16 the fluid under pressure in back of the vane escapes through the port 55 and travels through a pipeV to the port 51 which isopened by thesetting of Y clockwise and follow the same sequence of events e just Ydescribed in the other direction.

y i If the fluid .under pressure is continuously applied to the servomotorjwhenY in one position a vcertainportion will/be continuously discharged through the dual passages in the shoes 26 and 35 'to the reversing valve chamber.V However it will `be noted that Ythe motivating rfluid is discharged through theport 55 as soon as the latter is opened Ya slight amount which is prior to theend of the vane Stroke, and the inertia of the mass, making up the vane and the movable parts connected thereto,ris depended'upon for completing the Vstroke of the vane. By varying or changing the positions of the recesses 41 and 48 and the ports 55 and 56 and controlling the pressure of the motivating fluid the desired operating characteristics of the vane and device it actuates may be obtained.

One application of the servomotor is shown in diagrammatic view, Fig. 7, where the source of fluid pressure is received by the pipe line 62 which in this case is compressed air employed for starting the Dieselengine. The supply line 62 is connected to the lower chamber 63 of the relay valve 64.

The relay valve is provided with a valve 65 attached at one end to the stem 66 `which is provided with a piston head 61 at the other end. The piston is operated in the chamber 68 and is urged upwardly by the coil spring 69, Thus the fluid pressure and the spring tend to maintain the valve 65 closed but the piston 61 is larger in diameter than the valve, thus requiring a lower differential in pressure to open thevalve.

Assuming that the valve 65 is closed and air under pressure is supplied to the chamber63, this air is effective in the control line to the manual control valve 1I which when in its neutral 'position maintains the line 1D closed and exhausts both control lines 12 and 13 but when moved to the position indicated Ahead admits compressed air to the line 12 and the line 13 not being charged is connected to the exhaust return line 14 and when moved to the position indicated Reverse admits compressed air to the line 13 and connects line 12 to exhaust.

The lines 12 and 13 are connected to opposite sides ofthe fluid motor piston 15 which through the linkage and sector gears 16 shift the valve actuating ycam shaft 11 of the Diesel engine, thereby changing the fuel cams 18 and the starting air distributor 19 for operating theengine in either the forward or reverse direction.

Thus when the selected control line 12. is er1- ergized the piston 15 moves downwardly, causing the cam shaft 11 to move to the right. The lower sector engages a compressible check which insures a complete movement of the cam shaft in either direction.

The connecting rod which supports the piston 15 is provided with valves 80 at each end thereof for permitting the compressed air to continue to flow through the lines 12 and 13 only after the cam shaft has completed its movement to the selected position. When the manual control valve 1I is moved to a selected operating position to reverse the engine the discharge line 14 releases the pressure inthe opposite control line through its corresponding valve 8,!) to the servomotor I0, the control line 8| and the chamber 68 of the master relay valve 64 and also continues to drain the chamber of the piston 15 before fluid under pressure is admitted to the opposite side of the second section of the control line. As previously stated the shoes 26 and 3570i the abutment and the vane respectively of the servomotor l0 are provided with restricted discharge passages that are constantly open to the atmosphere or to the chamber of the housing 20; Thus after the selected control line is closed by the movement of the piston 15 the entrappedl air in front of the moving vane in the servomotor I0 escapes past the shoes 26 and 35 and passes directly to a low pressure discharge, thus preventing the vane from being blocked from movement. Initial movement of the piston 15 closes the valve 80 and thus blocks further discharge of the second- .section of the nonselected control, line through the manual control valve 1l. However the servomotor l0 is provided with an independent. discharge or leakagev path which continuously exhausts fluid under pressure simultaneously from either side of the servomotor. When the piston 15 completes its stroke the selected valve 80 admits fluid under pressure through the corresponding control line to the Aservomotor l0.

As shown in Fig. 7 the line 12, which is energized, with compressed air, is connected to the port 5I of a servomotor I0. The compressed air having swung the vane counterclockwise,y and properly positioning the reversing valve for di.- recting the scavenging air to the engine when the latter is set to move `the boat or train ahead, it is permitted to flow out the port 58 to the pipe lin where it travels to thef chamber 68" of the-relay valve64 where it forces the piston 61'downQ- wardly against the fluid pressure in the cham- Vber 63 and compressing the spring 69 to open the to Ythe air the pistons down and causing the engine to turn over. As the Diesel engine gains speed as an air motor, it is switched to fuel oil Vand operates as an internal combustion engine. Thus each reversing device must properly function before the engine can be revolved in the opposite direction.

I claim:

1. In a fluid circuit for starting and reversing a Diesel engine as an air motor the combination of ailuid pressure supply, a normally closed fluid actuated master relay valve arranged to connect the supply to the valve-controlled cylinders of Diesel engine to operate the same, a manual control valve, a fluid motor for shifting a distributor and valve operating cam shaft reversing gear mechanism which control the ope-ration of the Diesel engine, a fluid servomotor for controlling a blower reversing valve of said engine, a pair of fluid control lines connecting the associated sides of the servomotor, the fluid motor and the manual control valve thelatter of which selectively conects one control line to said supply andthe other to exhaust, and a. third fluid control line connected to the master relay valve and arranged to receive fluid under pressure from the selected control line through the servomotor after the latter has functioned, to open the master relay valve and admit fluid under pressure from the supply to the valve controlled cylinders lto turn over the engine.

2. The structure of claim 1 which also includes a valve in each control line leading to the servomotor and operated by the fluid .motor to admit fluid to the alternate sides of the servomotor only after the fluid motor has functioned.

3. The structure of claim 1 wherein the control valve exhausts the .control line circuitV when neither control is connected to the supply.

4. In a fluid. circuit for starting and reversing a- Diesel engine equipped with a direct drive air blower. the combination of a fluid pressure-supply,

a normally closed master relay valve arranged to connect the supply tovalve-controlled cylinders of. the Diesel engine to: Startthe'same, a manual 7 control valve,-a iiuid motori for shifting a distributor and valve operating cam shaft reversing gear mechanism which4 control'the operation of the Dieself engine in either direction, a uid ser-1 vomotor for actuating a blower reversing valve ofthe engine, a pair of `iuid control lines in two sections connecting the associated sides of the manual control valve, the uid motor and the servomotor inthe order named, the manual control valve arranged to selectively connect the first l s'ection'ofr one control'line to exhaust and the other tov said supplyrto energize the ud motor and the'servomotor, means operatedl by the fluid motor Y'at the end of its energized movement to :connect theisecon-dsection to therst section of the selected control line to energize the servomotor,and a third Vcontrol line. connected tothe' master relay valve and energized by the servomotor after the'latter has-functioned, to open the master relay valve to admit fluid underpressure from the supply tothe valve controlled cyl'-V inders to turn over the engine.

5.*In a iluid circuit for starting and reversing a Diesel engine equippedV with a direct drive air Vblower the combination of ay fluid pressure supply, a differential master valve biased to close sections connecting the associated sides of the manual control valve, the fluid motor and the servomotor in the order named, a third control line connecting the servomotor to the differential masterV valve, theY manual control valve arranged to selectivelyconnect the rst section of one of said pairs of control lines to the fluid pressure i supply and the alternate control line to exhaust,

means actuated by the completed movement of the uid motor to energize the fluid servomotor through the second section of the selected con- Y trol hline, and means actuated bythe completed 4movement of the fluid servomotor through the third control lineto energize the differential master valve and open the latter to admit fluid to the valve controlled cylinders of the Diesel engine to sta'rt the same.

6. In a fluid circuit the combination of a source of fluid under pressure, a manual controlvalve connected thereto, a double action iluid motorga doubleraction fluid servomotor, a singleiaction fluid motor, a pair of fluid control lines connecting the associated sides of the manual control valve andthe double action fluid motor, a second pair offluid control lines Vconnecting the associated sides of the double action fluid motor and the double action fluid servomotona third control Lline connecting the double action fluid servomotor with the single action uid motor, the manual control valve being arranged to connect the source of fluid under'pressure with a selected control line to operate the double action uid moto'r, means operated by the double action iluid motor `as it completes its stroke to operate the double acting iiuid servomotor through a selected 'control line of the second pair, and means operated by the vdouble action fluid servomotor as it'completes its stroke toV operate the single actingV fluid motor throughthe third controlline.V

7., AInl a fluid circuit the'combination of a source .oftiluid under pressure,` a manual control valve 8 t connected thereto, a doubleaction fluid motor, a double action uid servomotor, a single action fluid .moton a pair of fluidV control lines in two sections connecting the Vassociated vsides of the manual control valve, the double action fluid motor and the double action fluid servo-motorl in the order named a third control line connecting the single action fluid motor with the double ac'Y tion fluid servomotor, the manual control valve being arrangedto 'selectively connect the source of iluid'underV pressure with one of said pair .of control lines, and means to prevent the operation of themotors in the sequencea'named precedingmotor has functioned.

8. The structure of claim '7 characterizedn that. lsaid means includes a fvalve4 in the second section of each control line operatedby the double action fluid motor as the latter completes its stroke. Y

9. The structure of claim 7 characterizedin that said means includes a valve for directing the flow of huid to the third control line from the double action fluid servomotor when the latter completes its stroke.- Y f v 10. The structure of claimv '7 characterized in that said means includes a valve actuated by. the uid flowing through'the selected control line for directing the fluid ilow to the third control line. ll.. They structure of claim 7 characterized in that said means includes a valve actuated'bythe iluid flowing throughl the selected control line for directing the fluid flow. to vthethird controlline from the doubleaction fluid servomotor whenthe latter completes its stroke.

12. In a fluid circuit the combination cfa source of fluid kunder pressure, arvdischarge, a manual control valve, connected with thesupply and'with the.f discharge, Aa double actionfluid motor, a double action fluidservomotor.havingran independent restricted outlet constantly openfto discharge, a` single actionfluid motor, apairl of ,control lines in two sections vconnecting thel as- ,action iluid motor for controlling the ow of fluid to the double action uid servomotor, a third control line connecting the servomotor with the single action fluid motor, and'means to direct the fluid to the third control line to operate the Asingle action fluid motor from aV selected one ,ofthe pair of control lines after the double action fluid servomotor has completed itsV stroke;

13. In a fluid circuit for starting and vreversing a Diesel engine as an air motor which consists in asupply of air under pressure,l a discharge, a manual controlvalve connected with .the supply and with the discharge, a double action air Y motor for 'shifting a distributor and cam shaft reversing mechanism which control the operation of the engine, a double action air servomotor'for actuating a blower reversing valve of said engine, a single actionair motor arranged to operatea valve which connects the supply to valve-controlled cylinders of the engine to operate .the same as an air motor, a pair of control lines connecting theassociated sides of the manual control valve, the double action motor and the dou-Y ble action servomotor, Vsaid manual control valve arranged to selectively connect'one control vline -to the supplyand the other todischarg'e 'or both control linesA to discharge, a' valve inA eachV control Yjuntilij the line operated by the double action motor for controlling the ow of air to the servomotor, a third control line connecting the servomotor with the single action motonand means to prevent the operation of the motors in the sequence named until the preceding motor has functioned.

14. In a fluid circuit for starting and reversing a Diesel engine as an air motor which consists in a supply of air under pressure, a discharge, a manual control valve connected with the supply and with the discharge, a double action air motor for shifting a distributor and cam shaft reversing mechanism which control the operation of the engine, a double action air servomotor for actuating a. blower reversing valve of said engine, a single action air motor arranged to operate a v-alve which connects the supply to valve-controlled cylinders of the engine to operate the same Aas an air motor, a pair of control lines connecting the associated sides of the manual control valve, the

double action motor and the double action servoi motor, said manual control valve arranged to selectively connect one control line to the supply and the other to ydischarge or both control lines to discharge, a valve in each control line operated by the double action motor for controlling the flow of air to the servomotor, a third control line connecting the -servomotor With the single action motor, and means to direct the air to the third control line from a selected one of the pair of control lines after the servomotcr has completed its stroke to operate the single action motor.

JOSEPH E. WHITFIELD.

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