US2037358A - Reversible fluid pressure motor - Google Patents

Description

April 14, 1936. 1.. A. AMTSBERG REVERSIBLE FLUID PRESSURE MOTOR Filed June 9, 1934 3 Sheets-Sheet 1 N50 TEA L llll El I INVENTOR Z55 TEE A.AM7'JBEE6.

M 'WTTQRNEY April 14, 1936.

L. A. AMTSBERG REVERSIBLE FLUID PRESSURE MOTOR Filed June 9, 1934 3 Sheets-Sheet 2 M MW. 4 E

INVENTOR 'ZEJm'eAAMTJ55e6 BY M ATTORNEY April 14, 1936. L. A. AMTS BERG 2,037,358

REVERSIBLE FLUID PRESSURE MOTOR 7 Filed June 9, 1954 3 Sheets-Sheet 3 Z5 Z3 35 30 Z9 26 Tlzlil. a a

fbEWMAEM) WORNEY Patente is. 14, was

UNITED STATES PATENT OFFICE REVERSIBLE FLUID PRESSURE MOTOR- Application June 9, 1934, Serial No, 729,796

11 Claims. (Cl. 121-87) This invention relates to rotary motors operated by an expansible fluid, such as air, steam, or gas. More specifically it concerns rotary motors of the movable vane type in which the vanes or blades are carried by a rotor eccentrically mounted within a cylinder. The invention has particular reference to reversible motors of the type described which are of wide application, for example in connection with the operation of portable tools or for use on gate valves in oil refineries.

In rotary motors of the described type dimculty has been encountered in keeping the vanes in the desired close contact with the cylinder wall, 15 which is necessary in order to prevent leakage of pressure fluid through the space between the outer edges of the blades and the surface of the cylinder. The eifectof leakage around the edges of the vanes is more pronounced at the time of starting the motor than when the speed of the motor aids in maintaining contact by centrifugal force, although at all times there will be more or less leakage unless positive means are provided to force the vanes outwardly against the cylinder.

The particular means employed in the present invention consists of live air admitted underneath the blade for forcing it outwardly.

An object of this invention is to increase the efliciency of a, rotary fluid pressure motor by preventing waste of fluid pressure. It will be pointed. out hereinafter that the live air, which is used to prevent leakage does not increase the air consumption of the motor because the same air is caused to pass into the inlet side of the fluid chamber to provide power means acting against the sides of the blades for driving the rotor.

Another object of this invention is to reduce leakage around the outer edges of the vanes by applying fluid pressure urging the vane outwardly, characterized in that this pressure is efiective during a large portion of the cycle through which the blade passes. One objection to the known methods of employing fluid pressure for sealing the outer edges of the vanes is that while they are eiiective during the period that a blade passes through a short are, the blade becomes automatically disconnected from the source of holding pressure prior to the time that it leaves the inlet side of the fluid chamber between the rotor and cylinder. In those devices in which fluid is first passed underneath a vane and then conducted through a radial passage in the rotor to the .fluid chamber, the port admitting air to the latter is 5 usually arranged rearwardly of the vane with respect to the direction of rotation. In prior existing motors of this description, it has been found necessary to cut off the supply of air to the inner edge of a blade prior to the time that the blade leaves the inlet side of the fluid chamber. Otherwise, live air would be admitted to that part of the fluid chamber disposed between the inlet and exhaust sides. In the case of a reversible rotary motor, provision must be made for conducting the air from beneath a blade through a port leading to the fluid chamber which port may be either in the rear of or in advance of the associated blade depending on the direction of rotation. Consequently the are through which the blade passes while in communication-with the supply of air for forcing the blade outwardly, is still further restricted to prevent any possible supply of live air between .two blades that have passed beyond the inlet side of the fluid chamber. The result is that the blades having reached this position are not supplied with fluid pressure in a radial direction'for providing a tight seal against the cylinder wall.

A further object of this invention'is to prolong the holding pressure underneath a blade until after it has-left the inlet side of the fluid chamber and has provided a seal between said inlet side and the space in front of the blade. In order to accomplish this object, there is provided a novel means for conducting the holding pressure fluid away from the inner edge of the blades, whereby during the initial application of holding pressure this fluid will be conducted to the fluid chamber either in front of or in back of the associated blade, depending upon the direction of rotation, and whereby after the blade has passed through a predetermined arc the holding pressure continues but the fluid creating this pressure does not flow into the fluid chamber adjacent the blade. To this end the invention comprises a novel cut-off device including an arcuate slot in the cylinder end plate, the slot being arranged to be passed over by ports in the rotor communicating with the inner edges of the blades. In the case of those blades communicating with the slot, the latter conveys the fluid from its holding to its torque producing position, but after a blade has passed beyond a predetermined position, there is no communication between the inner edge of the blade and the fluid chamber, the holding pressure on the inner edge of the blade continuing even after the side of the blade has been cut off from the supply of torque producing pressure fluid.

A further advantage provided by the devious the fluid chamber cause an initial drop in pres- I sure, and this difference in pressure, between the inner and the outer edge of the blade, seats the blade against the cylinder and provides the necessary seal for starting.

A feature of this invention is a reservoir associated with the inlet side of the fluid chamber which provides a by-pass for pressure fluid around the edges of those blades which lie on the inlet side and which delays the building up of pressure in the fluid chamber to facilitate sealing of the blades upon starting of the motor. The reservoir, moreover, provides a steady, rather than a fluctuating pressure against the blades because it is supplied with pressure fluid at all times, even after the blade communicating therewith has been cut off from the arcuate slot which conducts the live air from the inner edge of the blade to the fluid chamber.

Other objects and features will appear more clearly from the following description taken in connection with the accompanying drawings and appended claims:

In order to illustrate the invention one comcrete embodiment thereof is shown in the accompanying drawings in which:

Fig. 1 is a longitudinal sectional view of a reversible motor with the controlling valve shown in neutral position;

Fig. 2 is a right end elevational view with the operating handle and the inlet and exhaust pipes removed;

Fig. 3 is a sectional view substantially'along the line 3-3 of Fig. 4 showing the cylinder and the housing therefor;

Fig. 4 is a transverse sectional view substan-- tially on the line 4-4 of Fig. 1 but showing the control valve arranged for forward rotation;

Fig. 5 is a similar transverse sectional view substantially on the line 55 of Fig. 1 with the rotor omitted;

Figs. 6 and '7 are fragmentary sectional views conforming to Figs. 4 and 5 respectively but showing the control valve in neutral position;

Fig. 8 is an end elevational view of the rotor, drawn to a larger scale and showing the position of the cylinder and of the rotor inlet and outlet ports in broken lines; I

Fig. 9 is an end view of the rotor looking in the same direction as in Fig. 8, but on a smaller scale,

and showing the cylinder, the rotor being broken away to show one of the cylinder end plates;

Fig. 10 is a sectional view 01' the rotor'taken along the broken line IIl--I0 of Fig. 4; and

Fig. 11 is a sectional view taken substantially along the broken line I I-II of Fig. 5.

The embodiment of the invention chosen for the purpose of illustration comprises a. motor having a housing I and cylinder heads 2 and 3, which are maintained in assembled relation by bolts 4. Heads 2 and 3 provide bearings 2a and 3a, respectively for the shaft ends 5a, 5b of rotor 5. Shaft 'end 5b projects beyond head 3 and bearing 3a to provide a power take-oi! 50. In the upper part of housing I control valve 6 is supported for limited rotary movement with its stem 6a projecting through a stufling box I of any suitable or desired type on cylinder head 2, an operating handle 611 being secured to the outer end of the stem. Stops 6c and 6d (Fig. 2) on valve 6 are arranged to engage a fixed stop 8 (Figs. land 2) on head 2 to limit the movement of valve 6. A fluid pressure supply pipe 9 is mounted on cylinder head 2 and connects with one end of the chamber in which valve 6 is mounted while an exhaust pipe I0 secured to cylinder head 3 leads from the opposite end. A partition 6e across valve 6 separates the fluid pressure supply from the exhaust.

Rotor 5 is eccentrically mounted within a cylinder I I which'takes the form of a cylindrical liner secured to housing I. Rotor 5, as clearly I2 in which are slidably supported vanes or blades I3. Fluid pressure is utilized positively to hold the blades I3 in contact with liner II. To this end the motor is so arranged that pressure fluid is first admitted directly beneath blades I3 and is then conducted into the fluid chamber between the rotor 5 and cylinder I I.

As shown in Fig. 11, the slots are preferably deeper at the central portion than at the ends of the rotor, and the blades are of corresponding shape. To facilitate introduction of live air to the central portion of the inner edge of each slot,- this edge is provided with counterbores I2a extending inwardly from the rotor ends for a limited distance. enlarging the slot to permit air to flow around the inner edge of the blade as well as underneath it for a distance equal to the length of the bores. The counterbores I20. are adapted to register in succession with arcuate grooves or ports I5a (or' be seen from Fig. 8 that each blade registers at its inner edge with the fluid supply port I5a. for a considerable part of its travel and accordingly will be forced outwardly against the cylinder wall These counterbores have the effect of I II during this interval to provides. tight seal at the outer edge of the blade.

After the live motive fluid is utilized as a h0ld+ ing force, it is conducted through a series of ports and passages to the fluid chamber where it is permitted to expand to drive the rotor. Referring to 'Figs. 1, 4, 8, l0 and 11, a series of spaced passages 22 are associated with each blade and extend from the inner edge of the slot I2 outwardly for a limited distance, terminating at a longitudinal passage 23 extending for the entire length of the rotor and parallel with the axis thereof. The ends of the longitudinal passages are adapted to register successively with an arcuate groove 25 (or 26) formed in each of the end plates I9 and 20 and disposed adjacent to the arcuate supply port I5a (or Ilia). Each end plate is provided with slots 28 leading from the rotor outlet ports 25, 26 to the periphery of the end plate which is recessed at 29 (see Fig. 10) to provide communication from the slot 28 through a cooperating recess 30 in the cylinder I I to the inlet side of the fluid chamber or crescent-shape space separating the rotor from the cylinder.

The inlet side 32 of the fluid chamber is always in communication with a fluid accumulator chamber or reservoir 34 by means of slots 35 formed in the cylinder II. The circumferential length of the cylinder slots 35 corresponds approximately with the circumferential length of the end plate slots 28 and rotor outlet slots 25. The accumulator chamber on the inlet side of the motor is closed with respect to atmosphere, while the corresponding chamber 36 on the exhaust side is opened through port 6h, the interior of valve 6 and exhaust port l0, it being understood that when the motor is reversed, chamber 36 becomes the accumulator and chamber 34 is opened to exhaust.

The manually controlled throttle mechanism for supplying live air to the rotor supply ports 15a and l6a.' and for venting the accumulator chambers 34 and 36 will now be described. Figs. 1, 2, 6 and 7 show control valve 6 in neutral position. Figs. 4 and 5 show the valve set to drive the rotor 5 in a clockwise direction as indicated by the arrows in Fig. 4. The fluid pressure enters the motor through supply pipe 9, passes through port 31 to the inlet side of control valve 6, through 6f (Fig. 5) into passage 15 which opens into the fluid chamber through port I5a in end plates l9 and 20. A similar passage I6 is adapted to convey motive fluid from the port 6f in the valve to the rotor supply port l6a when the throttle valve 6 is turned to reversing position. Referring particularly to Figs. 5 and 11, each inlet passage l5 (or I6) comprises an upper port I I5 (or I I6), a horizontal duct H5 (H6), and branch arms 3l5 (3l6) terminating at the port 15a (l6a). When the throttle valve 6 is adjusted for forward movement to admit live air to the rotor supply passages on the right hand side of the rotor, looking in the direction of Figs. 4 and 5, the valve 6 cuts oil the upper end of the chamber on the right side which becomes the accumulator chamber, or reservoir, on the inlet side of the fluid chamber. At the same time, the corresponding chamber 36 on the left, or exhaust side, is vented through an exhaust port 6h in the valve. When the throttle valve is thrown to reversing position, it cuts off the upper end of chamber 36 on the left side, making that chamber the accumulator for pressure fluid admitted through the rotor inlet ports Mia and at the same time vents chamber 34 through a port By in the throttle valve.

To facilitate explanation of the operation of the invention, the component parts of q the crescent-shape space between the rotor and. the cylinder will be designated respectively as the inlet side 32 of the fluid chamber, the exhaust side 42 and the intermediate portion 43, as shown in Figs. 4 and 8, it being understood that for operation in the reverse direction, 42 becomes the inlet side and 32 the exhaust side. As long as there is a tight seal between the blades l3 and the inside wall of the cylinder H, all pressure fluid passing from the inlet side to the exhaust side must act against the side faces of the blades in the intermediate portion to produce the necessary torque for driving the rotor. Assuming that the motor is at rest and is started under a heavy load, pressure of the live air may be insuiiicient to overcome the initially high load and, unless there is a tight seal at the outer edges of the blades, pressure fluid will escape between the blades and the cylinder wall, passing direct from the inlet to the exhaust side of the fluid chamber without driving the blades thereby resulting not only in a waste of motive fluid but also lowering the maximum torque adapted to be developed by the motor when starting from rest under a heavy load. In many applications ofthe invention, the starting torque is of much more importance than the torque developed by the motor after it has obtained its normal speed, particularly if the motor is employed for turning or unscrewing a gate valve as employed in oil refineries. Unless the motor can be depended upon to overcome the maximum possible friction of the valve when themotor starts to operate, it will be unsafe in operation and therefore not suitable for the purpose. By the use of applicant's novel arrangement for providing a tight seal before the live air on theinlet side has a chance to pass over the edges of the blades, a dependable method of securing high starting torque is employed, as will now be described.

' 36 and exhaust port 6h in the throttle valve 6.

The exhaust pipe It] may be vented to atmosphere. At the same time that the exhaust side of the rotor is connected to atmosphere or any other suitable exhaust, the control valve 6 admits air through the port 6, and passages l5 to the arcuate supply ports |5a disposed at opposite ends of the rotor 5 and in alignment with certain of the counterbores I20, which conduct the live motive fluid from the ports I5a to the bottom edges of the slots l2 in which the blades I3- are mounted. All blades which happen to register with the arcuate supply ports 15a are thereby forced radially outwardly against the I wall of the cylinder. The admission of live air underneath the blade is particularly effective at this stage of the operation to provide a'tight seal, for the reason that the pressure underneath the blade'is not counteracted by any appreciable pressure at the outer edge of the blade, by virtue of a novel arrangement for delaying the building up of pressure in the inlet side of the fluid chamber. One of the means employed to retard development of high pressure at the outer edge of the blade while the inner edge is being subjected to full line pressure comprises a series of ports and passages (22, 23, 25, 28, 29, 30) through which the air must pass, which results in a drop in pressure of the live air in travelling from the inner edge of the blade to the inlet side 32- of the fluid chamber. These ports and passages, as described in detail above comprise the rotor outlet ports 25 and slots 26 leading to the inlet side 32 of the fluid chamber.

As shown in Fig. 8, the rotor outlet port 25 is in the form of an arcuate groove or slot which is suppliedwith live air by some but not all.of the blades which register with the rotor inlet ports I511. As seen in Fig. 5, the lower end of arcuate groove 25 is approximately adjacent to the lower end of the slots 35 in the cylinder wall. The position of the lower end of the slots 35 and of the slots 28 determines the size of the inlet side of the fluid chamber (and of the exhaust side in the case of a reversible motor), while the position of the lower end of rotor inlet slots l5a.

stant that the holding pressure is cut off. Since there is a limit to the size of the inlet side of the fluid chamber, a corresponding limit was placed on the size of length of the arcuate inlet port in prior devices of this type in order to prevent admission of air from the inner edge of the blade though the rotor to the fluid chamber at point intermediate the inlet and exhaust sides. The present invention, however, permits the inlet slots to be lengthened to continue the outward holding pressure over a longer period, without correspondingly lengthening the inletside of the fluid chamber. Referring to Fig. 9 it will be seen that the blades register with the supply grooves I511 and are accordingly subjected to the holding or sealing pressure until they reach approximately the 5:30 oclock position. It was not found possible to continue the application of the outward holding pressure over so long a period in prior devices which employed a radial port leading directly from the inner edge of the blade to the fluid chamber, inasmuch as it would result in the admission of air between two blades both of which have been cut off from the inlet'side of the fluid chamber. In the case of a reversible motor, even the blade in the four oclock position could not be connected to the supply ports because that would result in the admission of air to the intermediate portion of the fluid chamber in case the rotor was travelling in such direction that air was admitted to the chamber in front of the associated blade.

After the live air has forced the blade outwardly and has undergone a drop in pressure in passing through a series of ports and passages to the inlet side'32 of the fluid chamber, it comes into communication with the accumulator chamber 34,. The accumulator chamber, in conjunction with the cylinder slot 35, provides a by-pass around the edges of the blades on the inlet side of the fluid chamber. The chamber 34 preferably has sufficient volume that it retards the building up of pressure within the fluid chamber until the blade has first been forced outwardly to provide a tight seal. Thus leakage around the outer edges of the blades on the intermediate side of the fluid chamber is prevented and the rotor is permitted to start under a heavy load. The accumulator chamber moreover receives pulses of air from the interior of the rotor as the blades register in succession and, due to the larger volume of the accumulator chamber 34 as compared with the inlet side 32 of the fluid chamber, these pulses are absorbed to produce a more constant and less fluctuating pressure against a blade for driving the rotor.

The operation of the motor in the reverse direction will be understood without further description inasmuch as the parts of the motor are symmetrical excepting that for one direction the longitudinal passages 23 are in advance of their assoplated blades while for reverse operation these passages trail their associated blades. The position of the longitudinal rotor passages with respect to the blades is not material in the present invention inasmuch as the arcuate slots I5a. and 25 registering with the blades and rotor passages respectively, need not bear any exact phase relationship with respect to each other.

While the invention has been herein disclosed in what is now considered to be a preferred form, it is to be understood that the invention is not limited to the specific details thereof but cover all changes, modifications and adaptations within the scope of the appended claims.

What I claim is:

1. A fluid pressure rotary engine comprising a rotor, a cylinder enclosing said rotor and having end plates engaging the ends of the rotor, said rotor having slots extending from end to end of the rotor, blades movably mounted in said slots and adapted to contact at their outer edges with the cylinder, means for admitting pressure fluid to the inner edges of the slots to hold the blades in tight contact with the cylinder, said means comprising a port in one of the end plates connected to a source of pressure fluid and comprising a series of rotor inlet ports in the rotor adapted .to register successively with said end plate port, said rotor inlet ports being arranged at one end of the rotor at a common radius, said rotor having a series of rotor outlet ports arranged on a different radius at the same end of the rotor:

having a port with which said rotor outlet ports are adapted to register to receive pressure fluid from the rotor outlet ports.

2. In a fluid actuated rotary motor, a cylinder having a pressure fluid supply passage for the motor, a rotor in said cylinder, a fluid chamber being provided between the rotor and cylinder. said rotor having radial slots extending lengthwise thereof, blades slidably mounted in said slots, plates closing the ends of the cylinder, said plates having ports connecting the supply passage with the slots for feeding pressure fluid to the bottoms of the slots through inlet passages in the rotor adapted to register with the ports, said rotor hav ing outlet passages therein connected with the bottoms of the slots and leading to one side of the fluid chamber for supplying pressure fluid to the fluid chamber for rotating the rotor, means for exhausting the other side of the fluid chamber, and means for closing the outlet passages after the blades associated therewith have passed beyond a predetermined position.

3. In a fluid actuated rotary motor, a cylinder having a pressure fluid supply passage for the motor, a rotor in said cylinder, said rotor having radial slots extending lengthwise thereof, blades slidably mounted in said slots, plates closing the ends of the cylinder, said plates having ports conmeeting the supply passage with the slots for feeding pressure fluid to the bottoms of the slots through inlet passages in the rotor adapted to register with the ports, said inlet passages leading from the ends of the rotor to the bottoms of the slots, said rotor having outlet passages therein connected with the bottoms of the slots for supplying pressure fluid to the cylinder for rotating the rotor, and meahs for closing the outlet passage associated with the blade when it has passed a predetermined position and means for continuing the supply of pressure fluid to said blade through said inlet passage after it has passed said predetermined position.

4. A rotary engine comprising a cylinder, a rotor eccentrically mounted therein to provide betweenfor driving the rotor, means for rendering said passed beyond a predetermined position, the supply ports being in register with the inlet passages after the blades have passed beyond said predetermined position. I

5. A rotary engine comprising a cylinder and having a source of pressure fluid and an exhaust therefor, a rotor eccentrically mounted therein to provide between the rotor and cylinder a ores-- cent-shape fluid chamber, one'side of which is connected with said exhaust, the rotor having radial slots, blades slidably mounted in said slots, said rotor having inlet passages communicating with said pressure fluid source and leading to said slots for supplying pressure to force the blades outwardly, and outlet passages communicating with the slots and adapted to deliver pressure fluid from said slots to the inlet side of the fluid chamber, and means for closing both the inlet and exhaust passages associated with a blade from said source and fluid'chamber respectively during one portion of its movement, said means opening both the rotor inlet :Tnd the rotor exhaust .passages when the blade arrives at a predetermined position and being adapted to close the 'rotor exhaust passages before the inlet passages.

6. A rotary engine comprising a cylinder, a rotor eccentrically mounted therein to provide between the rotor and cylinder a crescent-shape fluid chamber, the rotor having radial slots, blades slidably mounted in said slots, said rotor having inlet passages leading to said slots for supplying pressure to force the blades outwardly, and outlet passages communicating with the slots and adapted to deliver pressure fluid from saidpla' es closing the ends of the cylinder and engag ing he ends of the rotor, a control member having a forward and a reverse position and controlling the direction of rotation of the rotor, a first and a second set of passages connected to the re rpective ends of the fluid chamber, means controlled by said control member for simultaneously connecting the first set of passages to the fluid supply and the second set of passages to the exhaust in theforward position of the control member, means controlled by said control member for simultaneously connecting the second set of passages to the fluid supply and the first set of passages to the exhaust in the reverse position of the said rotor having radial slots extending length-- wise thereof and opening through the periphery and the ends of the rotor, blades slidably mounted in said slots and extending from end to end of the same, plates closing the ends of the'cylind'er, said end plates having ports connecting the supply passage with the slots for feeding all of the pressure fluid furnished the motor first to the bottoms of the slots through the ends of the, same at the opposite ends of the rotor for holding the blades against the cylinder on the pressure side of the motor, and then to the fluid chamber, said rotor having outlet passages \therein connected with the bottoms of the slots for supplying pressure to the inlet side of the fluid chamber for rotating the rotor, said outlet passages being indirect and restricted whereby to create a substantial drop in pressure between the irmer and outer edges of the blades upon starting of the motor. I

9. In a fluid actuated rotary motor, a cylinder having a pressure fluid supply passage for the motor, a rotor eccentrically mounted in said cylinder to provide a fluid chambertherebetween, said rotor having radial slots extending lengthwise thereof and opening through the periphery and the ends of the rotor, blades slidably mountedin said slots and extending from end to end of the same, plates closing the ends of the cylinsupply passage with the slots for feeding pressure fluid furnished the motor to the bottoms of the slots through the ends of the same at the opposite ends of the rotor for holding the blades against the cylinder on the pressure side of the motor,

'der, said end plates having ports connecting the said rotor having outlet passages therein connected with the bottoms of the slots for supplying pressure to the inlet side of the fluid chamber for rotating the rotor, said outlet passages being indirect and restricted whereby to create a substantial drop in pressure between the inner and outer edges of the blades upon starting of the motor, and including ports in the end plates adapted to receive pressure fluid from the rotor.

10. In a-fluid actuated rotary motor, a cylinder having a pressure fluid supply passage for the motor, a rotor eccentrically mounted in said cylinder to provide a fluid chamber therebetween, said rotor having radial slots extending lengthwise thereof and opening through the periphery and the ends of the rotor, blades slidably mounted in said slots and extending from end to end of the same, plates closing the ends of the cylinder, said end plates having ports connecting the supply passage with the slots for feeding pressure fluid furnished the motor to the bottoms of the slots through the ends of the same at the opposite ends of' the rotor for holding the blades against the cylinder on the pressure side of the motor, said rotor having outlet passages therein connected with the bottoms of the slots for sup plying pressure to the inlet side of the fluid chamber for rotating the rotor, said outlet pas-1 sages being indirect and restricted wherebylto create a substantial drop in pressure between the inner and outer edges of the blades upon starting of the motor, and means for prolonging the drop in pressure comprising an accumulator chamber of greater volume than the inlet side of the fluid chamber and connected to the latter through openings in the cylinder.

11. In a fluid actuated rotary motor, a cylinder having a pressure fluid supply passage for the motor, a rotor eccentrically mounted in said cylinder to provide a fluid chamber therebetween, said rotor having radial slots extending lengthwise thereof and opening through the periphery and the ends of the rotor, blades slidably mounted in said slots and extending from end to end of the same, plates closing the ends of the cylinder, said end plates having ports connecting the supply passage with theslots for feeding pressure fluid furnished the motor to the bottoms of the slots through the ends of the same at the opposite ends of the rotor for holding the blades against the cylinder on the pressure side of the motor, said rotor having outlet passages therein con- 10 nected with the bottoms of the slots for supplying pressure to the inlet side of the fluid chamber for rotating the rotor, said outlet passages including ports in the end plates, and means for by-passing pressure fluid around the ends of blades in the fluid chamber, said means including slots in cylinder of limited circumferential length and a chamber connected to the inlet side of the fluid chamber through said slots.

LESTER A. AMTSBERG.

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