US2708354A - Hydraulic timing means - Google Patents

Description

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y 17, 1955 J. v. BRADY ETAL 2,708,354

' HYDRAULIC TIMING MEANS,

Filed June 5, 1952 s Sheets-Sheet 1 INVENTORS. Jcwnea' K15324241 B ZZZ fiMZ y 7 1955 J. v. BRADY ETAL 2,708,354

HYDRAULIC TIMING MEANS y 17, 1955 J. v. BRADY ETAL 2,708,354

HYDRAULIC TIMING MEANS Filed June 5. 1952 5 Sheets-Sheet 3 INVENTORS. Jamzea l BYZ/Zmffi I M M17 MQM United States Patent HYDRAULIC TIMING MEANS James V. Brady, New York, N. Y., and William I. Hamilton, Hackensaek, N. J., assignors to Lanova Corporation, Long Island Cit N. Y., a corporation of Belaware Application June 3, 1952, Serial No. 291,412

4 Claims. (Cl. 6425) This invention relates to means for varying the angular relation between a drive shaft and a shaft driven thereby, for timing the injection or admission of fuel in internal combustion engines, and analogous purposes.

Injection or diesel engines are quite sensitive to the timing of the injection of fuel. It is desirable for most efiicient operation of injection engines, particularly engines operating over a Wide speed range, to advance and retard the injection timing in accordance with increase and decrease in engine speed. Injection timing devices are known. In general, the known devices are rather complicated and expensive in construction, lack sensitiveness in operation and often are inadequately lubricated.

Our invention is directed to means for varying the angular relation between a drive shaft and a shaft driven thereby, particularly suitable for use as injection timing means, but suitable also for other purposes. The drive shaft has driving connection to the driven shaft through a hydraulic servo-motor effective for varying the angular relation between the shafts. As used with injection engines, the drive shaft is driven from the engine shaft, the driven shaft is the operating or cam shaft of the injection pump, and the servomotor is controlled by valve means. The valve means is adjustable responsive to the speed of the drive shaft, to provide automatic adjustment of injection timing. The control valve means comprises a control valve adjustable relative to the housing and the rotor of the servo-motor, the rotor being turnable relative to the housing and the control valve. The latter and a sleeve valve turnable with the rotor, and the drive shaft, are provided with cooperating ports and ducts or passages for admitting and discharging operating hydraulic fluid to and from the servo-motor effective for turning the rotor in proper direction to an appropriate extent for effecting and maintaining desired angular adjustment of the driven or pump cam shaft relative to the drive shaft. Conveniently, the operating hydraulic fluid is the engine lubricating oil delivered by the usual oil pump from the engine crank case sump to the servo-motor under substantial pressure. The servo-motor is provided with means for preventing clogging thereof by dirt contained in the oil and is also provided with means guarding against movement of the rotor relative to the housing due to variations in torque required to drive the injection pump shaft, which is maximum at the instant of injection and then rapidly falls to a minimum. All of the moving parts of the servo-motor and the control valve and associated parts operate in oil so that no appreciable friction occurs, which is conducive to sensitiveness and accuracy in operation. Further objects and advantages of our invention will appear from the detail description.

In the drawings:

Figure 1 is a lengthwise central vertical sectional view, taken substantially on line 1-1 of Figure 2, of injection timing means embodying our invention, certain parts being shown in elevation and certain other parts being shown partly in elevation and partly broken away and in section, the injection pump being shown fragmentarily and the sleeve valve turnable with the rotor.

parts being shown in the positions which they occupy when the injection pump cam shaft is in full retard position;

Figure 2 is an end view of the timing means of Figure 1, with the housing cover plate removed and the housing shown fragmentarily, with the parts in the positions which they occupy when the cam shaft of the injection pump is in full retard position;

Figure 3 is a sectional view taken substantially on line 33 of Figure 1;

Figure 4 is a sectional view taken substantially on line 44 of Figure 1;

Figure 5 is a sectional view taken substantially on line 5-5 of Figure 1;

Figure 6 is a sectional view taken substantially on line 6-6 of Figure 1;

Figure 7 is a sectional view similar to Figure 3, but with the parts in the positions which they occupy at advanced position of the injection pump cam shaft;

Figure 8 is a sectional view similar to Figure 4, but with the parts in the positions which they occupy at advanced position of the pump cam shaft;

Figure 9 is a sectional view similar to Figure 4, but with the parts in the positions which they occupy when the injection pump shaft is in retard position; and

Figure 10 is a sectional view similar to Figure 3, but with the control valve and the other parts in the positions which they occupy in Figure 9.

Our instant invention is in the nature of an improvement over the hydraulic timing means of the copending application of James V. Brady, Serial No. 255,891, filed November 6, 1951. in the timing means of our instant invention admission of oil to, and drainage of oil from, the servo-motor is controlled by the control valve and a The control valve is piloted in the sleeve valve, the latter is piloted in the head of the drive shaft, and the passages or ducts for supplying oil to, and draining oil from, the servo-motor are in the head of the drive shaft. With that arrangement, but two ports and a groove, in the control valve, and four ports, in the sleeve valve, are required, regardless of the number of vanes on the rotor. That is conducive to accuracy in indexing of the ports in the control valve and in the sleeve valve, which is of importance. Further, the passages or ducts for supplying oil to, and discharging -=,oil from, the servo-motor are arranged in two groups,

those of one group opening into a common channel in the head of the drive shaft and those of the other group opening into another and separate channel in the head of the drive shaft. That avoids necessity for precision in ,drilling the passages or ducts in the head of the drive shaft, thereby reducing expense and assuring accuracy in operation. An additional and important advantage of our invention is that the control valve and the drive shaft may be quite short so that possibility of bending and binding of parts, due to any slight misalignment or distortion, such as might be caused by the drive gear thrust, is effectively guarded against. That eliminates binding and objectionable wear of parts and renders it possible to reduce clearances to a minimum thereby reducing oil leakage to a minimum, which is conducive to sensitivity and accuracy in operation.

The timing means of our invention is particularly suitable for use with injection engines and will be so described, though in its broader aspects it may be used for other purposes, as above noted. We have shown the timing means of our invention, by way of example, as used with an injection pump 2%, which may be any suitable known purnp, having a casing 21 and an operating A cylindrical casing 24 is bolted to one end of the pump outer end of collar casing 21, about annular flange 25 thereof, with an intervening sealing O ring 26. The casing 24 is coaxial with cam shaft 22 and is bolted at its other end to an inner plate 27 of a casing 28 which extends upwardly from and opens downwardly into the crank case (not shown) of an injection engine with which the injection pump 29 is associated. The casing 2-8 is provided with a front wall or plate 29 having a circular opening therein about which is disposed an annular collar fill on theouter end of which seats a cover plate 31, this plate 31 and collar 39 being bolted or otherwise suitabl secured to front wall 29 of casing 23.

The outer end wall 33 of casing 23% is thickened and is provided with an outwardly extending annular flange 34 about which plate 27 seats, with an axial bore in which is mounted a bearing bushing 35. A tubular drive shaft 36 is rotatably mounted through bushing and is, provided with radial inlet ports 37 opening interiorly thereof and opening at their outer ends into an interior circumferential groove 38 in the bushing 35. The shaft 36 extends outward beyond plate 27 and has its outer end'portion slightly reduced in diameter to provide a shoulder against which seats a flanged collar 49 keyed on shaft 32: and restrained against outward movement thereon by a thimble ili threaded into the outer end of shaft 36 and provided at its outer end with a head 42, there being .a washer 43 confined between head 42 and the A gear 44 seats on flange 45 of collar 4 and is suitably secured thereto, conveniently by bolts 46. This gear 44, in practice, is driven, through suitable gearing,from the engine crank shaft so that the shaft 3: is driven at predetermined speed relative to the engine crank shaft,- as is known.

The bolts 46 pass through an annular clamping and reinforcing plate 48 seating on the web of gear 44 and, in cooperation with the belts in, clamping it tightly against flange 45. A substantially oblong arm i9 is keyed on the outer end of a control valve mounted for relative turning movement in drive shaft 36 and extending outward therebeyond. The arm 59 is recessed at its midlen'gth for reception of a spring washer 51 confined between arm and head 52 of a cap screw 53 threaded into the outer end of control valve portion of control valve 5% is slightly reduced in diam-. eter, as shown in Figure l, to provide a shoulder between which and the washer 51 arm 49 is confined. Two oppositely disposed fly weights 5'4, shown more clearly in Figure 2, are pivoted at their outer ends, at 55, on the clamping plate 48, the studs or pivots 55 being secured to plate 48 andprojecting an appropriate distance outward therebeyond. Posts 56 are pivotally mounted on Weights 54 radially inward thereof beyond the pivot studs 55and a tension spring 57 extends between and is anchored at its ends to the posts 56. Pins 58 are secured in the'fly weights 54, adjacent the ends thereof remote from the pivot studs 55, and extend through oppositely disposed cam slots 59 in the end portions of arm 49. As will be understood from what has been said, the tension spring 57 urges the fly weights 54 toward each other and,

when the drive shaft 36 is not rotated, or is rotated at a speed corresponding to or less than the full retard angular position of the pump cam shaft 22 relative to drive shaft 36, as will be explained more fully later, pulls the fly weights54 into their innermost positions, with the pins 58 at the inner ends of the cam slot 59, as shown in Figure 2. When the speed of rotation of drive shaft 36 is increased to or beyond a predetermined value, which may be termed its advance injection speed, as will be ex plained more fully later, the fly weights 54 swing outward in opposition tothe tension spring 57 and the pins 58, in cooperation with the cam slots 59, turn thearrn 49 and thereby turn the control valve 58. The cam slots 59 are so disposed that unit 49 is turned clockwise, as viewed in Figure 2, by outward movement of fly' weights 54 and is turned counterclockwise by inward movement thereof. Accordingly, the control valve 50 is turned clockwise responsive to increase in speed of rotation of the drive shaft 36 and is turned counterclockwise responsive to decrease in the speed of rotation of drive shaft 36, within the speed range thereof from full retard injection to full advance injection.

The control valve 50 is provided with an outer circumferential shoulder 61 confined between the inner end of thimblc 41 and an interior shoulder of shaft 36, effective for restraining control valve 55) against endwise movement in either direction while permitting free turning thereof within shaft 36. A plug 62 is threaded into and closes the inner end of a bore in the control valve 50 extending from the inner end thereof, providing an admission chamber 63 for operating hydraulic fluid, as will be explained more fully later. The control valve 50 is provided with a reduced bore or inlet duct 64 extending from the outer end of chamber 63 and with inlet or admission ports d5 opening radially outward from duct 64 into an annular space (it) surrounding control valve 56), as will appear more fully later.

The bearing bushing is provided with an admission port 67 which opens into an admission passage 65 in end wall 33 of casing 24. The outer end portion of passage 68 is enlarged and threaded to receive the threaded end portion of a tube 69 connected to a suitable source of The outer end i supply of operating. hydraulic fluid under appropriate pressure. in practice, the tube 69 is connected to the discharge of an oil pump of suitable known type, which withdraws oil from the sump of the engine crank case and delivers it under appropriate pressure to tube 69. Referring further to Figure l, the inner end of admission duct 6-; is formed to provide a seat for a ball check valve '70 urged in closing direction by a compression spring 71 confined between valve 79 and plug 62, for a purpose which will be described later.

The drive shaft 36 is provided, at its inner end, with, an enlarged frusto-conical head 66 and a cylindrical head 72, comprising a cylindrical body or barrel 73 within which are disposed a suitable number-six being shownoi' abutment elements 74 of approximately sector shape. These abutment elements 74 fit tightly against the inner circumferential face of barrel 73, are spaced apart circumferentially thereof and extend radially inward of barrel 73. ring 75 fits tightly in the inner end of barrel 73 and is secured therein by bolts 76 passing through head 66 and through the abutment elements 74 and threading into plate 75. The barrel 73 is positioned axially by flanges 77 and 73 of head 66 and plate 75, respectively, and abutment elements 74 are clamped tightly between plate 75 and head 66 and are held accurately in position thereby and by the bolts 7 6.

The head 72 provides a cylindrical housing closed at its ends for reception of a rotor 30 shown more clearly in Figures 1 and 6. This rotor "30 comprises a central cylindrical hub 81 and vanes 82 integral with and extending radially outward from hub 51 into the spaces 83 between the abutment elements 74. The outer end of hub 81 of rotor 89 has a sealing, but not tight, fit against the flat inner face of head 66 of drive shaft 36. Hub 81 also has a sealing, but not tight, fit between the inner ends of the abutment elements 74, and the inner end of hub 81 has a sealing, but not tight, fit against the fiat.

outer face of the end closure plate 75. The vanes 82 of rotor 36 are of substantially less thickness than the width of the spaces 83 between the abutment'elements' 74 and have a sealing, but not tight, fit with the circumferential wall of barrel 73 and with the inner face of 7 cap screw Blthreaded into the end of cam shaft 22, there An annular flanged closure plate or 33 being a retaining ring 92 and a lock washer 93, of suitable known type, confined between me head of screw 91 and an interior shoulder of hub 81 for restraining the latter against outward movement lengthwise of cam shaft 22, hub 31 being restrained against inward movement by the inner race of the ball bearing 23, as will be clear from Figure l. The hub 81 is provided with suitably disposed discharge ducts 94 extending therethrough from the inner end of chamber 85 of rotor 8%, for discharge of the hydraulic operating fiuid or oil from chamber 85 into the l casing 24, as will appear more fully later. The oil is discharged from the lower portion of casing 2-7? through an opening 95 in end wall 33 of casing 24 and thence downward through casing 2-3 into the crank case of the engine.

The frusto-conical head 66 of drive shaft 36 is provided with a first set of substantially radial ducts 98 with their radially outer ends opening through the inner face of head 66 at one side of the vanes 82 into the spaces 33 between the abutment elements 7%. Head 66 is further provided with a second set of substantially radial ducts 101 with their radially outer ends opening through the inner face of head 66 into the spaces 83 between the abutment elements '74 and at the sides of vanes 82 opposite to those at which the ducts 93 are located.

The drive shaft 36 is bored out from its inner end to receive a sleeve valve 86 fitting snugly, but not tightly, in shaft 36 and over the inner end portion of control valve 59, the latter being piloted in sleeve valve 86 and sleeve valve 85 being piloted in shaft 36 with the latter piloted thereon. The sleeve valve 86 is provided with two upper ports 87 and 88 and two lower ports 89 and 99, spaced apart lengthwise thereof. The ports 87 and 89 open into an inner circumferential channel 96 in head 66 of drive shaft 36, and the ports 88 and 96 open into a second inner circumferential channel 97 in head 66. The outer end of sleeve valve 86 is spaced from the outer end of the bore in shaft 36, to provide the space 66 about control valve 50, previously mentioned. The sleeve valve 86 is provided, at its inner end, with two diametrically opposite slots S 9 and 160 which receive a key 102 fitting snugly therein and in diametrically opposite grooves in the outer end of hub 81 of rotor 89. The sleeve valve 86 is thus attached to rotor 89 for rotation therewith and is restrained against relative axial movement, by hub 31 of rotor 89 and by the pressure of the oil in space 69 on the outer end of sleeve valve 86. The slot 1% is extended so as to overlap the inner end portion of a lengthwise drainage or discharge groove or passage 103 in the outer face of control valve at the lower portion thereof as shown in Figure l. The groove 103 is of approximately the same width as the respective ports 89 and 9t) and of a length to brid e both thereof.

The control valve is further provided, at the opposite side thereof from groove 163, with two radial ports 1135v and 106 extending from the admission chamber 63, disposed in the same transverse planes as the channels 96 and 97, respectively. The abutment members 74 are provided at one side of the outer ends thereof with recesses 107 aligned with the ducts or passages of head 66 of drive shaft 36, and at the opposite sides of their outer ends with recesses 168 aligned with the ducts or passages 101, for admitting oil under pressure to the servo-motor at one side of the vanes 82 of rotor 86 while draining oil from the other side of vanes 82, as will be explained more fully presently.

When the drive shaft 36 is not rotating, or is being driven at a speed less than that requiring advancement of injection, the rotor 80 is in its full retard position, in which the leading faces of the abutment elements 74 are in contact with the vanes 82 of rotor 86, it being understood that the shaft 36 is driven clockwise as indicated by the arrow in Figure 2. The control valve 50 is then also in its maximum counterclockwise or retard position and both of the ports 105 and 1% thereof are then closed at their radially outer ends by sleeve valve 86, and groove 193 is closed to ports 89 and 9t) of sleeve valve 86, by control valve 58, as will be clear from Figures 3 and 4. The rotor is then driven from the drive shaft 36 through the direct mechanical driving connection provided by the abutment elements '74 and the vanes 82, and the angular relation between the drive shaft 36 and the injection pump cam shaft 22 remains unaltered.

Referring to Figures 7 and 8, upon increase in speed of rotation of the drive shaft 36 to a value requiring advancement of injection, the fly weights 54 move outward in opposition to tension spring 57, under the influence of centrifugal force, turning the control valve 50 in clockwise direction. This turning of the control valve 50 brings port 165 into communication with port 87, while maintaining groove 163 closed to port 39. Oil then flows under pressure from the admission chamber 63 into channel 96 and thence through ducts 98 into the servo-motor, between the abutment elements 74 and the vanes 82 of rotor The entering oil exerts pressure upon the corresponding faces of the vanes 82 and turns the rotor 86 in clockwise or injection advance direction relative to the associated housing. That advances the angularity of the injection pump cam shaft 22 relative to the drive shaft 36 thereby advancing the timing of injection to the desired extent corresponding to the engine speed. When the desired advancement of injection has been eifected, the turning of sleeve valve 86 on the control valve 50 substantially closes the radially outer end of the port 1G5, leaving it cracked slightly open for a purpose to be described presently.

During clockwise turning of rotor 86 relative to the enclosing housing, the oil at the opposite sides of the vanes 82 from the ducts 98 is displaced and passes through ducts 161 into channel 97 and thence through port 99 and groove 1% into the outlet or discharge chamber 85 of rotor hub 31, from which the oil flows through ducts 94 into casing or housing 24 and is returned to the engine crank case as previously described. As will be understood, when the radially outer end of the port 195 of control valve 59 is uncovered by turning thereof, the radially outer end of the port 196 remains closed by sleeve valve 86 and groove 103 is opened to port 9% as shown in Figure 8. If the speed of rotation of drive shaft 36 continues to increase, the control valve 56 will be turned a further distance clockwise and that may continue until the maximum speed of rotation of drive shaft 36 is reached and the maximum advancement of injection has been attained, at which time the rotor 81 will have been turned into its maximum advance position. When the rotor 80 has been turned, clockwise relative to drive shaft 36, a distance corresponding to the speed of rotation of shaft 36, with corresponding turning of the sleeve valve 86 about control valve 56, the ports and 99 are cracked open. That is desirable in order to maintain oil under appropriate pressure in the spaces between the vanes 82 and the elements '74, in the event of slight leakage about the vanes, since the drive between the housing and the rotor is then through the oil confined between the vanes 82 and elements 74. As will be understood from what has been said, the rotor 89, and with it the injection pump cam shaft 22, may be advanced to any desired extent, within limits, relative to the drive shaft 36. The rotor 38 and its enclosing housing and associated parts thus constitute a servo-motor controlled by the control valve 50 and the sleeve valve 86 and responsive to the speed of rotation of the drive shaft 36 and, therefore, responsive to engine speed, for automatically advancing the timing of injection in accordance with increase in speed of rotation of drive shaft 36.

When the speed of rotation of drive shaft 36 decreases,

the control valve 50 is turned counterclockwise thus opening port 106, closing groove 1% to port 99, closing port 1135, and opening the port 89 to the groove 193, as shown in Figures 9 and 10. Oil then flows through ducts 191 under pressure into the servo-motor at one side of the vanes 32 thus turning the rotor 86 in counterclockwise direction, the oil at the opposite sides of the vanes being discharged through ducts 98, channel 96, port 8 and groove 1133 into the discharge chamber 85, from which it is delivered into the casing 24 and thence into casing 28 and downward into the engine crank case, as before. This counterclockwise turning of rotor 84? reduces the angle of advancement of the injection pump cam shaft relative to the drive shaft 36, thereby retarding the timing of injection, as will be understood. if there is no further decrease in the speed of rotation of drive shaft 36, the counterclockwise turning of rotor 813, and with it sleeve valve 86, closes the ports 88 and 196, and closes port 8? to groove 1%, ports 37 and H35 being then cracked slightly open to supply make-up oil to the rotor 80 in replacement of oil which may leak past the vanes 82, and port K) also beingithen cracked slightly open to groove 103 to drain off the oil leakage; thus maintaining the angular adjustment between the shafts 36 and 22.

If thespeed of rotation of drive shaft 36 continues to decrease, the continued turning movement of control valve 50 counterclockwise maintains the ports 88 and itl open and the port S9 open to groove 1%, while maintaining ports 87 and 165 closed and port 9% closed to groove 1%, until the rotor 86 is returned to full retard position, at which time all of the ports'lt o, fill, H35 and 89 are again closed, as before. 7

As will be seen, from what has been said, the servomotor, under control of the control. valve is effective for advancing and retarding the timing of injection responsive to increase and decrease in the speed of rotation of the drive shaft 36, throughout the range of turning movement of the rotor 8t relative to the servo-motor housing. in general, an angular adjustment of approximately fifteen degrees of the rotor 86 relative to its associated housing is sufficient, though that angle may be varied to suit conditions. Also, by varying the cam slots 59, the rate of adjustment, or advancing or retarding of the timing of injection, may be adjusted or set to suit any particular engine.

In the operation of the injection pump, the peak torque required occurs at the instant of injection and then falls off rapidly to a rninirnum'. Accordingly, at the instant of injection there would be a tendency to force oil from between the vanes 82 and the abutment members 74 back into and through the admission chamber 63 of the control dirt, such as carbon and other impurities. Such impurities are urged toward the circumferential wall of the housing of the servo-motor, during rotation thereof, by centrifugal force, and are removed therefrom through the passages or ducts 98 or iii} and the corresponding channels and ports of the drive shaft 36, sleeve valve 36 and control valve 5%, and groove M53 of control valve St), as will be understood from what has been said. lnthat manner, dirt which would tend to accumulate within the servo-motor and might causeclogging thereof to such an extent as to interfere objectionably with its accuracy in operation, is continuously'removed therefrom, which is conducive to accuracy in the timing of injection, it will alsobe noted that the movable parts of the servo-motor,

including the control valve 5?, operate in oil, which elimi- 1 hates friction and resultant wear and further contributes that precision in drilling of those ducts is not required.

Operation of the servo-motor is controlled by but four ports in the sleeve valve 86 and two ports and the groove 14)? in control valve 56, all of which are spaced well apart and may be precisely indexed without difficulty, which is conducive to accuracy in operation. Further, by provid- 5 ing the sleeve valve 36, the drive shaft 36 may be quite short so as to avoid risk of bending and binding of parts, thereby reducing necessary clearance and resultant oil leakage to a minimum. 7

The timing means of our invention is particularly suitable for timing the injection in injection engines, and has been described as used for that purpose, by way of example. In its broader aspects, however, it may be used for varying the angular relation between a drive shaft or member and any driven shaft or member. Accordingly, the driven shaft may be, for example, a cam shaft for actuating the valves of an aspiration internal combustion engine receiving fuel-air mixture from a carburetor or other suitable source, or any other shaft or member which it is desirable to adjust for timing purposes.

As above indicated, and as will be understood by those skilled in this art, changes in detail may be resorted to. without departing from the field and scope of our invention, and we intend to include all such variations, as fall within the scope of the appended claims, in this application in which the preferred form only of our invention has been disclosed.

We claim:

1. lrrmeans for varying the angular relation between two shafts, a driven shaft, a tubular drive shaft coaxial with said driven shaft, a servo-motor providing driving connection between said shafts comprising a housing fixed to said drive shaft and a rotor within said housing fixed to said driven shaft, said housing having circumferentially spaced abutment elements fixed thereto extending in- Wardly thereof, said rotor having vanes extending between said elements, said drive'shaft having two interior inwardly opening circumferential channels spaced apart axially thereof and two sets of ducts respectively opening into said channels, the ducts of one set opening into said housing at one side of said vanes and the ducts of the other set opening into said housing at the other side of said vanes, a control valve concentric with said drive shaft turnable relative thereto and having a discharge passage, and a sleeve valve cooperating with said control valve concentric with said drive shaft and turnable with said rotor about said control valve, said valves having cooperating ports effective for admitting operating hydraulic fiuid to one of said channels and connecting the other thereof to said discharge passage and vice versa responsive to turning of said control valve in one direction and in the other direction respectively relative to said drive shaft.

2. In means for varying the angular relation between two shafts, a driven shaft, a tubular drive shaft coaxial with said driven shaft, a servornotor providing riving connection between said shafts comprising a housing fixed to said drive shaft and a rotor within said housing fixed to said driven shaft, said housing having circumferentially spaced abutment elements fixed thereto extending in-. wardly thereof, said rotor having vanes extending between said elements, said drive shafthaving two interior inwardly opening circumferential channels spaced apart axially thereof and two sets of ducts respectively opening into said channels, the ducts of one set openinginto said housing at one side of said vanes and the ducts of the other set opening into said housing at theother side of said vanes, a control valve concentric with said drive shaft turnable relative thereto and having an admission chamber and a discharge passage, and a sleeve valve con centric with said drive shaft and turnable with said rotor about said control valve, said valves having cooperating ports effective for opening one of said channels to said chamber while closing it to said passage and closing the other of said channels to said chamber while'opening it to 9 said passage and vice versa responsive to turning of said control valve in one direction and in the other direction respectively relative to said drive shaft.

3. In means for varying the angular relation between two shafts, a driven shaft, a tubular drive shaft coaxial with said driven shaft, a servomotor providing driving connection between said shafts comprising a housing fixed to said drive shaft and a rotor within said housing fixed to said driven shaft, said housing having circumferentially spaced abutment elements fixed thereto extending inwardly thereof, said rotor having vanes extending between said elements, said drive shaft having two interior inwardly opening circumferential channels spaced apart axially thereof and two sets of ducts respectively opening into said channels, the ducts of one set opening into said housing at one side of said vanes and the ducts of the other set opening into said housing at the other side of said vanes, a control valve in said drive shaft concentric therewith turnable relative thereto and having an interior admission chamber and an exterior discharge passage, and J a sleeve valve fitting in said drive shaft and about said control valve and turnable with said rotor about said control valve, said valves having cooperating ports effective for opening one of said channels to said chamber While closing it to said passage and closing the other of said channels to said chamber while opening it to said passage and vice versa responsive to turning of said control valve in one direction and in the other direction respectively relative to said drive shaft.

4. In means for varying the angular relation between two shafts, two coaxial shafts, a servo-motor providing driving connection between said shafts comprising a housing fixed to one of said shafts and a rotor within said housing fixed to the other shaft and turnable in either direction relative to said housing, said one shaft being tubular and h ving two interior inwardly opening circumferential channels spaced apart axially thereof and two sets of ducts respectively opening into said channels for admitting and exhausting operating fluid to and from said housing, a control valve in said one shaft concentric therewith turnable relative thereto and having an interior admission chamber and an exterior discharge passage, and a sleeve valve fitting in said one shaft effective for closing the inner sides of said channels and fitting about said control valve and turnable thereabout with said rotor, said valves having cooperating ports effective for opening one of said channels to said chamber while closing it to said passage and closing the other of said channels to said chamber while opening it to said passage and vice versa, responsive to turning of said control valve in one direction and in the other direction respectively relative to said one shaft.

References Cited in the file of this patent UNITED STATES PATENTS 2,488,361 Witzky et a1 Nov. 15, 1949 FOREIGN PATENTS 467,808 Great Britain June 23 ,1937

561,811 Great Britain June 6, 1944

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