US2891775A

US2891775A - Vibrator

Info

Publication number: US2891775A
Application number: US707197A
Authority: US
Inventors: George L Malan
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-01-06
Filing date: 1958-01-06
Publication date: 1959-06-23
Anticipated expiration: 1976-06-23

Description

June 23, 1959 I G, L, MALAN 2,891,775

VIBRATOR Filed Jan. 6, 1958 2 Sheets-Sheet 1 F/GJ.

\ 1 INVENTOR.

650/?6: L. MAL AN I BY 24 62 54 6/ 6560 7/ A T TORNE Y June 23', 1959 G. L. MALAN 2,891,775

VIBRATOR Filed Jan. 6, 1958 2 Sheets-Sheet 2 INVENTOR.

A rromvs Y GEORGE L. NALAN United States Patent VIBRATOR George L. Malan, Covina, Calif.

Application January 6, 1958, Serial No. 707,197

Claims. (Cl. 259-4) This invention relates to an eccentric vibrator of the type useful for distributing and compacting viscous substances such as wet concrete, and the like.

The need for packing and distributing wet concrete throughout the entire volume of a form is well known, and many devices have been proposed for the purpose. One well-known type is shown in Malan Patents 2,187,- 088 and 2,743,090 issued January 16, 1940, and April 24, 1956, respectively. This type of vibrator is simple and involves few moving parts, principally a rotor which rolls around inside a larger race thereby exerting an eccentric force.

The rotor in this type of vibrator is caused to roll by creating compartments for receiving air under pressure at the peripheral surface of the rotor. Each compartment is formed between a vane which is forced outwardly from the rotor to contact the race, and the race and rotor. As pressurized fluid such as compressed air is admitted to each compartment in sequence, the compartment is expanded, thereby rolling the rotor around the race. When the compartment reaches maximum volume, it is connected to exhaust means. Further rolling of the rotor exhausts the air, and the cycle is thereafter begun again. This action is carried out in sequence, a plurality of compartments being spaced around the rotor, so the result is a continuous rolling of the rotor.

The vibrators shown in the aforesaid two patents have stood up well and have given good service. However, it has been found that they are relatively inefiicient consumers of compressed air. In addition, their vanes have sometimes worn down more rapidly than desired, requiring disassembly and repair which ought to be minimized. Excessive down time of such vibrators results either in the need to store extra units for use in the event of breakdown, or of tolerating work stoppage on a pouring job, both of which are expensive.

Accordingly, it is an object of this invention to provide improvements for a vibrator of the type described, by means of which the efficiency and longevity of the device are increased.

A feature of this invention resides in maintaining a continuous fluid pressure in passageways supplying air to the compartments at a point immediately adjacent the compartments, and providing valve means actuable by contact with the race for governing the flow of air to the respective compartments. This is a considerable improvement over prior arrangements, wherein the valving was performed at the end of the rotor, according to which arrangements it was necessary for pressure to change throughout a relatively voluminous passageway system before there was any significant pressure effect in the compartment itself. The instant arrangement, in effect, reduces the volume whose pressure must be changed in order to actuate the device.

Another feature of the invention resides in providing retraction means for the vanes used in the device. As shown in detail in Malan Patent No. 2,743,090, it is advantageous to use vanes whose total throw is insufiicient to maintain the vane in constant contact with the race. This advantage has been offset by the hard usage the vane receives when it strikes the race. This feature reduces the wear on the vanes.

The above and other features of this invention will be fully understood from the following detailed description, and the accompanying drawings, in which:

Fig. l is a side elevation, partly in cutaway crosssection, showing the vibrator of this invention;

Fig. 2 is a fragmentary view, in cross-section, showing valving means according to this invention;

Fig. 3 is a cross-section, looking upwardly, taken at line 3-3 of Fig. 1, showing the rotor at one operative position; and

Fig. 4 is a cross-section similar to Fig. 3, showing the rotor at another operative position.

As best shown in Fig. 1, the vibrator 10 is connected to a pair of concentric hoses: a first central pressure hose 11, and a surrounding exhaust hose 12. The central pressure hose is attached to an inlet pipe 13 and the exhaust hose is attached to the neck 14 of an end member 15, The inlet pipe 13 is threaded through a central hole 16 in the end member 15.

An annular chamber 17 surrounds the pipe 13 and makes fluid communication through passage 18 with an exhaust ring 19 which is a groove formed in the inner face 211 of the end member 15. The face 20 is smooth and planar, being interrupted only by the exhaust ring 19 and the opening at the hole 16. The opening of inlet pipe 13 provides a stationary pressure inlet port 21, which is located on the central axis 22 of the device. The exhaust ring 19 provides a stationary exhaust port which is concentric with the port 21 around the central axis.

A cylinder 23 having an internal cylindrical race 24 has one of its ends fixed by welding or other means to the end member 15, and has attached to its other end a second end member 25. These attachments are airtight. End member 25 is provided with a centrally disposed stationary inlet port 26 and a stationary exhaust port 27, these ports being of the same size and axially aligned with the corresponding ports in end member 15.

A passage 28 extending through the two end members and the wall of cylinder 23 communicates between the inlet pipe 13 and the stationary inlet port 26, while a second passage 29 extends through the same elements to interconnect the stationary exhaust port 27 with the passage 18 in the end member 15. The inner face 30 of the second end member 25 is smooth and planar, being interrupted only by the stationary inlet port 26 on the central axis and the annular exhaust port 27. The space within the cylinder which is defined by the race and the end members is substantially a right circular cylinder, the planes of the end members being interrupted only by the ports which are sunk therein.

A rotor 31 is placed between the end members inside the race. It is of the same axial length as the race, but of smaller lateral dimensions. The end face 32 of the rotor makes a smooth sealing sliding contact with the inner face 20 of end member 15. End fact 33 of the rotor makes a similar sealing sliding contact with the inner face 30 of end member 25. It will be seen that this rotor is able to move freely around the inside of the race in rolling contact therewith, while its end faces remain in constant sliding contact with the end members.

The rotor has at its outer periphery three

recesses

34, 35, 36. (See Fig. 3.) These recesses are spaced from each other. Each has associated with it a compartment and a number of parts, passages, and ports. For clarity in disclosure, only recess 34 will be described and shown in complete detail, it being understood that the other two recesses have identical provisions disposed 120 3 away from the corresponding elements associated with recess 34. If all of the elements were shown in a single figure, the drawings would be extremely confusing, wh1lc a separate drawing of each recess would be repetitious.

The recesses extend from end to end of the rotor, opening onto the race and terminating at the end members. Each has a narrow neck portion 37 adjacent the surface of the rotor and an enlarged stroke portion 38 located radially inwardly of the neck portion. A

vane

39, 40, 41 fits respectively in each of the recesses 34-, 35 and 36. Each vane has an L-shaped cross-section in a plane perpendicular to the central axis 22. Each vane has a first arm 42 which passes through the neck portion 37 so as to be extensible beyond the periphery of the rotor. The second arm 43 is disposed substantially at a right angle to the first arm and extends transversely across the stroke portion of the recess in contact with both sides thereof so as to form a piston reciprocable within the stroke portion of the recess.

The extensible arms 42 are too short to reach the race wall in all positions of the rotor; that is, the maximum reach of the vane plus the diameter of the rotor, is less than the diameter of the race. The inner portion of the recess which is bounded by the second arm 43 and the radially innermost end of the recess comprises an extension chamber l l of variable volume, the volume being a function of the radial position of the vane. The outer portion of the recess which is bounded by the second arm 43 and the radially outermost end of the stroke portion forms a retraction chamber 45 of variable volume, the volume being a function of the radial position of the vane.

As can be seen best in Fig. 3, the vane is reciprocated in the recess by two classes of force. A first force is exerted by fluid pressure conveyed through an extension chamber supply passage 4:; which connects the extension chamber to an extension chamber supply port 47. For convenience, this extension chamber supply port 47 is sunk in the lower end face 33 of the rotor where it slides along the inner face 30 of the second end member The chamber supply passage enters the extension cham ber 44 at its innermost end.

A retraction chamber supply port as is disposed in the end face 33 of the rotor and is connected by a retraction chamber supply passage 49 to the radially outermost end of retraction chamber 45. The extension chamber supply port 46 and the retraction chamber supply port are spaced from each other and are are so disposed at the end of the rotor that as the rotor rolls around the inside of the race, the ports periodically and at separate times register with the stationary inlet port 26 in the end me: ber 33. The location of the port 2.6 is shown in d line in Fig. 3 for the purposes of illustration, this port being below the section line 3 3 in Fig. l. The location of port 21 in end member 15 relative to axis 213 is also shown part of this port being behind the rotor in Pig. 3.

Extension chamber supply ports 51?, and retraction

chamber supply ports

51, 53 respectively supply corre sponding chambers associated with

recesses

35 and 36, through corresponding passageways which are not shown.

As illustrated in Fig. 1, an annular compartment sup ply groove 54 is sunk in the upper end face 32. of the rotor. This groove is centered on the central axis 5'5 of the rotor. It is desirable to have the compartment supply groove 54 in continuous communication with the port 21 as shown in Fig. i, but other dimensions than those shown can give the same continuous communication.

A compartment supply passa ends from the groove 54 to the surface of the rotor .cent each of the vanes. Compartment supply passage 56 is shown because it is associated with vane Corresponding compartment supply passages (not shown) are provided for compartments

adjacent vanes

35 and 36.

Valve means (see Fig. 2) located partly in the compartment supply passage 56 includes an enlarged valve chamber 57 within which a valve plug 58 is operable to open or close the passage by being dropped onto or lifted oif of a valve seat 59. The valve seat is partly formed by an insert which is held in place by screws 61. The insert can be removed to permit installation or removal of the plug. This plug has a tendency to be seated on seat because of the air pressure in passage 56 and because of the centrifugal force which results from rotation of the rotor. The valve plug is formed on an arm e2. which arm is pivoted at a joint 63. A cam portion 6 of the arm projects outwardly from the surface of the rotor as the rotor rolls around the race, except when it is pressed inwardly by contact with the race. As can best be seen in Fig. 1, two cam portions 64 are provided, each on an individual arm. The plug is supported on an elongated structure so that it extends a considerable portion of the length of the rotor, as does the valve chamber 57. This large valve area permits a rapid flow of air to an adjacent compartment. In Fig. 3, cam s4 is shown pressed inwardly to open its valve, while the arms of

valve members

65 and 66 are shown with their cam portions thrown radially outward (in Fig. 3), so that their valves are closed.

A chamber relief passage 67 intersects the sides of the recess 34 where it is intermittently in communication with extension chamber 44-, and always out of communication with retraction chamber 4-5. The relief passage opens onto the surface of the rotor.

The term compartment as used herein is defined as the region between the two end members, an extended vane in contact with the race, the race wall, and the rotor periphery, the rotor and race being tangent at one edge of the compartment. The sequential forcible opening up of these compartments is what causes the rotor to roll. This action is illustrated in Pig. 3 in which compartment 68 is just opening up clockwise of vane 39, and in Fig. 4, where compartment 68 has been enlarged. The compartment opens behind the line of contact between the race and rotor.

The operation of this device will now be described, it being understood that the direction of movement of the centroid of the rotor is shown by arrow 69, while the direction of rotation of the rotor around its centroid is shown by arrow 7%. The centroid moves in a clockwise direction around the race as seen in Pig. 3, while the rotor itself rotates in a counter-clockwise direction around its centroid.

The condition of the device as shown in Fig. 3 will be considered as a starting position. The operation of the elements associated with recess 34 will be described in detail, it being understood that the elements associated with

recesses

35 and 36 will go through the same movements after the line of contact between the race and the rotor has moved along and 240, respectively of the rotors surface. Rotor movement is caused principally by the extension of vane 39, by the enlargement of compartment 68, and by the sequential similar action of corresponding elements associated with the other recesses.

Compartment 68 is about to be opened in Fig. 3. EX- tension chamber supply port 47 has just come into registration with stationary inlet port 26 by overlapping the same in its cycloidal path within the race. Air under pressure is conveyed through passage 46 to extension chamber 45 so as to extend the vane and maintain it in firm contact with the wall of the race. The force exerted by the vane on the race also tends to rotate the rotor.

The cam section 64 of arm 62 has moved into contact with the wall of the race thereby opening the valve means in passage 56 at plug 58. This admits pressure from the compartment supply passage 56 to the compartment 68, which tends to enlarge the compartment, which enlargement is attained by rolling of the rotor along the race.

It is desirable for pressure to be exerted in the compartments as soon as possible after the line of contact between the rotor and race has swept past a vane. For this reason the cam section 64 is caused to protrude a significant distance beyond the outer periphery of the rotor and also the cam has a projection 71 (see Fig. 2) which tends to cause the cam to contact the race at about the same time that the vane is in tangent contact with the race. Therefore the pressure from passage 57 will be built up at the periphery of the rotor at about the time that the chamber 68 is opened up. The timing of valve means 58 can be adjusted by varying the distance by which the cam protrudes from the rotor, and also by varying the length of projection 71. By not using projection 71, and undercutting the cam at its free end, cam contact can be delayed. This cam is therefore applicable to any desired timing arrangement by changing its length, the distance it projects, and its angular location on the periphery.

The longer time the cam is in contact with the race, the longer time the air pressure is on in the compartment. The valve means 58 will be held open as long as the cam 62 is in contact with the wall of the race and as can be seen from Fig. 4, this may extend for a considerable number of degrees depending upon the length of arm 62 and the shape of the cam section 64. At any rate when the compartment is opened to the designed volume, the cam moves away from the race by virtue of the continued rotation of the rotor, and the air supply to the compartment is cut ofi.

Shortly after the condition shown in Fig. 4, vane 39 will no longer be in contact with the race, because it is too short. Then air can leak past the vane 39 from compartment 68, and exhaust quickly into groove 19. In addition, it will be seen that compartment 68 will, itself, overlap groove 19 after a few degrees of rotor movement beyond the position shown in Fig. 4.

At a later time it will be desired to retract the vane, so that the vane will not project beyond the surface of the rotor when the recess approaches the surface of the race. To facilitate the retraction, the relief passage 67 opens by virtue of extension of the vane and the pressure drops in the extension chamber by exhaust of the air therein into the compartment and out to exhaust. In addition, the chamber supply port 47 will have moved away from the stationary inlet port and no additional air pressure will be supplied to the extension chamber 45.

In Fig. 4 the compartment 68 is about to begin to exhaust. It will be observed that the compartment is about to overlap

exhaust grooves

19 and 27 in the end members through which the pressure escapes.

When the line of tangency is near a particular vane, the rotor periphery near the vane is moved outwardly beyond the exhaust grooves. The line of contact, a vane, and the end members, then define an expansible compartment for receiving air under pressure. When the rotor rolls far enough that a given compartment is no longer receiving air under pressure, the rotor periphery at this region has moved radially inward beyond the exhaust grooves, and that region is vented. It is also vented past the vanes which are not in contact with the race. It will therefore be appreciated that the major portion of the rotor periphery is, at any given time, vented to exhaust, while there is a part of the periphery, perhaps thereof, which is under pressure as part of an expansible compartment. The compartments are sequentially pressurized, one after another, around the periphery, and this sequential pressurization moves the rotor.

The position of vane 41 in Fig. 4 illustrates a later condition of vane 39. This vane is extended to its maximum reach but does not make contact with the race. The outer periphery of the rotor on both sides of this vane is vented through the exhaust grooves, and the extension chamber is vented to the surface of the rotor by virtue of opening of release passage 67 by extension of the vane. As the vane again approaches contact with the wall of the race (for example see the position of vane 40 in Fig. 3), it is desirable to avoid a sudden blow on the vane. Sudden iblows have caused accelerated vane wear in previous vibrators of this type. In this invention, such a blow is avoided by retracting the vane. For this purpose and with reference to Fig. 3, the retraction chamber supply port 48 will register with the stationary inlet port 26 just before such a contact is imminent and air admitted to the retraction chamber will retract the vane into the recess. In Fig. 4, vane 40 is shown retracted nearly all the way into the recess by air admitted through port 51. In Fig. 3, port 51 is shown approaching port 26 to accomplish this retraction of vane 40. The relief passage 67 bleeds ofi suflicient air from the extension chamber 45 that the vane can be retracted in this manner. When the vane laps over the opening to said relief passage in its retraction stroke, sufficient air is held in the extension chamber and its supply passage to pillow the vane so as to prevent a hard striking contact of the vane against the back of the extension chamber. The vane is therefore substantially retracted so that there is no sudden bending blow on the vane by the race. This markedly lengthens the life of the vanes. Thereafter the vane cycle as described above is repeated.

More or fewer than three vanes and recesses could have been supplied if desired but three vanes have been found to be sufficient. Utilizing more vanes simply makes the device more complex and more expensive to manufacture.

To start the device, it is sometimes necessary to shake it so as to bring an extension chamber supply port into registration with a stationary inlet port. Then the rotor is in such a position within the race that it will begin to move, and in a short time it is operating at full speed.

By providing the valve means in the surface of the rotor, the efliciency of this vibrator has been greatly improved and faster speeds have been obtained from the the same air flow rates, or, stated conversely, less air has been required for the same speeds. This device operates efiectively at about 7800 revolutions per minute on line pressures of about p.s.i.

The life of the

vanes

39, 40 and 41 has been greatly increased by providing the retraction ports and passages so that the direct blow between the race and the vane is eliminated. This feature permits the shorter vane to be used effectively by means of which an existing compartment can bleed past a vane which is out of contact with the wall of the race and utilize a substantially larger portion of the exhaust grooves to discharge compartment air, thereby providing a quicker exhaust cycle which, of course, reduces the back pressure against which the pressure side must work. Expansion past the vane into the next compartment also aids in making a quick pressure drop.

This invention is not to be limited by the embodiment shown in the drawings and described in the description, which is given by way of illustration and not of limitation, but only in accordance with the scope of the appended claims.

I claim:

1. In a vibrator of the type which includes a casing having an inner cylindrical curved race with a central axis, end members closing both ends of said casing, one of said members having a stationary inlet port therein for a source of pressurized fluid and one of said members having a stationary exhaust port therein, said ports being disposed in said end members symmetrically with respect to the central axis of the race, a free rotor of smaller lateral dimensions than the race positioned inside the race and having a curved peripheral surface interrupted by a plurality of recesses formed therein, said rotor having a central axis, and being adapted to roll around inside the race with the curved peripheral surface in rolling contact with the race and with each end of the rotor in flat sliding contact with an end member, a vane in each recess which extends from end to end of the rotor, each vane being reciprocable in its respective recess so as to define a chamber of variable volume at the inner end of each recess, and being of such dimensions that it can be moved entirely within the peripheral surface of said rotor, and can also be moved to project beyond said peripheral surface in its reciprocating movement, whereby, at some position of the rotor within the race, each vane can project beyond the peripheral surface to make sealing contact with the race and thereby form a compartment adjacent to a portion of the pe ripheral surface, said compartment being defined by the vane, the peripheral surface between the vane and the line of contact between the race and the peripheral surface, and the end members, and chamber supply ports and passages which are so disposed and arranged as to periodically register with said stationary inlet port to supply pressurized fluid for enlarging said chambers by moving the vanes toward the race, the improvement comprising: means for supplying pressurized fluid from said stationary inlet port to a compartment adjacent each of said vanes, said means including a compartment supply groove in an end of the rotor adjacent to the stationary inlet port, said compartment supply groove being in constant communication with the stationary inlet port, a com partment supply passage leading from said compartment supply groove to the peripheral surface adjacent to each one of said vanes so that an individual one of said compartment supply passages discharges into each of said compartments when formed, whereby all compartment supply passages are constantly maintained under pressure, and valve means adapted to be opened by contact with the race, one of said valve means being disposed in each of said compartment supply passages for controlling passage of pressurized fluid to its respective compartment, whereby, when a compartment is opened up between a vane and the line of contact of the rotor and race, the respective valve means are opened by contact with the race to supply pressurized fluid to said compartment.

2. In a vibrator of the type which includes a casing having an inner cylindrical curved race with a central axis, end members closing both ends of said casing, one of said members having a stationary inlet port therein for a source of pressurized fluid and one of said members having a stationary exhaust port therein, said ports being disposed in said end members symmetrically with re spect to the central axis of the race, a free rotor of smaller lateral dimensions than the race positioned inside the race and having a curved peripheral surface interrupted by a plurality of recesses formed therein, said rotor having a central axis, and being adapted to roll around inside the race with the curved peripheral surface in rolling contact with the race and with each end of the rotor in flat sliding contact with an end member, a vane in each recess which extends from end to end of the rotor, each vane being reciprocable in its respective recess so as to define a chamber of variable volume at the inner end of each recess, and being of such dimensions that it can be moved entirely within the peripheral surface of said rotor, and can also be moved to project beyond said peripheral surface in its reciprocating movement, whereby at some position of the rotor within the race, each vane can project beyond the peripheral surface to make sealing contact with the race and form a compartment adjacent a portion of the peripheral surface, said compartment being defined by the vane, the peripheral surface between the vane and line of contact between the race and the peripheral surface, the race, and the end members, and chamber supply ports and passages which are so disposed and arranged as to periodically register with said stationary inlet port to supply pressurized fluid for enlarging said chambers by moving the vanes toward the race, a compartment supply passage leading from an end of said rotor adjacent an end member having the stationary inlet port leading to the peripheral surface adjacent to each one of said vanes so that an individual one of said compartment supply passages is interconnected with each of said compartments when formed, and means for periodically interconnecting a compartment through its respective compartment supply passage with the stationary inlet port, the improvement comprising: providing the vanes with an L-shaped cross-section viewed in a plane normal to the central axis of the rotor, said vane thereby having a pair of arms, a first of said extending in the direction of reciprocation, and making a close fit in a portion of said recess, the second of said arms extending across the chamber so as to divide said chamber into two portions: an extension chamber and a retraction chamber, said retraction chamber lying on the side of the second arm closer to the peripheral surface, and providing the rotor with a retration passage for each vane which enters the retraction chamber there being means periodically registrable with said stationary inlet port for retracting each of said vanes by passing pressurized fluid through its respective retraction passage.

3. Apparatus according to claim 2 in which the vanes are L-shaped, thereby having a pair of arms, a first of said arms projecting in close-fitting relationship from the recess toward the rac and the second arm extending across the recess, and in which the rotor is provided with a retraction passage for each vane which enters its recess on the opposite side of the second arm from the chamher, there being means periodically registrable with said stationary inlet port for retracting each of said vanes by passing pressurized fluid through its respective retraction passage.

4. Apparatus according to claim 1 in which the said valve means comprises a closure adjacent to the surface of the rotor which is actuable to open its respective compartment supply passage by contact with the race.

5v Apparatus according to claim 1 in which the said valve means comprises a closure adjacent to the surface of the rotor, and actuator means comprising a member deflectable by contact with the race for moving the said closure, to open the passage in which it is displaced.

6. Apparatus according to claim 1 in which the said valve means comprises a valve member disposed in said compartment supply passage, an actuator arm mounted in a slot in the rotor, which arm has a portion adapted to project beyond the periphery of the rotor and to be pressed into said slot by contact with the race, the arm being connected to said valve member so as to close the valve means when the race does not bear against the arm, and open said valve means when the race bears against the arm.

7. Apparatus according to claim 6 in which the actuator arm is pivotally mounted to the rotor, and in which its portion which is movable beyond the surface of the rotor is disposed to one side of the valve member.

8. Apparatus according to claim 1 in which the vanes are provided with an L-shaped cross-section as viewed in a plane normal to the central axis of the rotor, said vane thereby having a pair of vane arms, a first of said arms extending in the direction of reciprocation and making a close fit in a portion of the recess, the other of said arms extending across the chamber so as to divide the chamber into two portions: an extension chamber and a retraction chamber, the retraction chamber being on the side of the said second arm closer to the peripheral surface. 3"

9, Apparatus according to claim 8 in which the rotor is provided with a retraction passage for each vane which retraction passage enters the retraction chamber, and means periodicall registrable with said stationary inlet port for retracting each of said vanes by passing pressurized fluid through its respective retraction passage.

10. Apparatus according to claim 9 in which each chamber is side-tapped on its side adjacent to the first 9 arm by a relief passage which is out of communication with the retraction chamber, said relief passage making connection with the peripheral surface adjacent the said vane.

11. Apparatus according to claim 9 in which each chamber has its own separate chamber supply ports and passages.

12. Apparatus according to claim 2 in which a sidetapped relief passage is provided for each of the chambers adjacent the first vane arm and out of communication with the retraction chamber, said relief passage connecting to the peripheral surface adjacent its respective vane.

13. Apparatus according to claim 1 in which the stationary exhaust groove comprises a continuous ringshaped groove in one of the end members, said ringshaped groove having a diameter such that it overlaps the rotor over a significant length of the peripheral surface.

14. In a vibrator of the class which includes a casing having an inner cylindrical curved race with a central axis, end members closing both ends of said casing, the

casing being provided with stationary inlet and outlet ports, a free rotor of smaller lateral dimensions than the race positioned inside the race which has a curved peripheral surface interrupted by a plurality of recesses formed therein, said rotor having a central axis and being adapted to roll around inside the race with its curved peripheral surface in rolling contact with the race and with each end of the rotor in flat sliding contact with an end member, there being a vane reciprocably disposed in each of said recesses for making contact with the race in some positions thereof, the improvement comprising: means for conducting fluid pressure to said vanes for extending the same to make contact with the race, and means for retracting said vanes out of contact with the race.

15. Apparatus according to claim 14 in which each of the vanes has an L-shaped cross-section viewed in a plane normal to the central axis of the rotor, thereby having a first arm and a second arm, said first arm extending in the direction of reciprocation and making a fluid sealing sliding contact with a portion of said recess, and a said second arm extending across the recess so as to divide said recess into an extension chamber and a retraction chamber, the retraction chamber being on the side of the second arm closer to the peripheral surface, said means for retractin the vanes comprising a retraction chamber supply passage adapted to be periodically registered with a source of pressurized fluid for retracting said vane.

References Cited in the file of this patent UNITED STATES PATENTS 1,819,867 Carlton Aug. 18, 1931 2,187,088 Malan Jan. 16, 1940 2,743,090 Malan Apr. 24, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,891,775 June 23, 1959 George L. Malan It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 60, for "fact 33" read face 33 column 8, line 42, claim 5, for "displaced" read disposed Signed and sealed this 8th day of December 1959.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents