US2900961A - Linear fluid actuator utilizing vanes - Google Patents

Description

Aug. 25, 1959 CHlE N-BOR SUNG LINEAR FLUID ACTUATOR UTILIZING 'VANES Filed April 5, 1957 2 Sheets-Sheet l INVENTOR.

CHIEN BOR SUNG ATTORNEY Aug. 25, 1959 CHIEN-BOR SUNG 2,900,961

LINEAR'FLUID ACTUATOR UTILIZING VANES Filed April 5, 1957 2 Sheets-Sheet 2 INVENTOR.

CHIEN BOR SUNG Q24 ATTORNEY United States Patent Claims. (Cl. 121-38) This invention relates to devices for producing linear mechanical motion from hydraulic pressure.

Hydraulic and pneumatic actuators are commonly'used in automatic equipment to produce linear motions. These actuators take the form of pistons which movethrough cylinders under fluid pressure and are known as the rams. The fluid which provides-the force for the motion isintroduced into a chamber behindthe piston. As fluid enters the cylinder under pressure the piston moves linearly to provide a larger chamber space to accommodate the fluid. Therefore, the amount of fluid which must be introduced'to the chamber is proportional to the length of the piston stroke.

In long stroke applications the'pistons must be made relatively large in area in order to avoid the undesirable effects of the fluids compressibility which are accentuated by the large ratio between piston area and length of stroke. As a result of these two requirements oflong fluid columns and high area, very large fluid power systems arerequired to provide the high flowrate necessary to produce longmotions. In many cases, even the system using largest practical piston area wouldstill not be stiif enough to provide adequate dynamic response for both open loop and closed loop control due to the, inherently large volume of fluid involved.

In order to overcome these disadvantages of long stroke ram type fluid actuators; the present invention contemplates alinear actuating device in which the volumeunder compression is independent of the length of stroke.

The present invention generally comprises a-linear cam member and a straight surface which are disposed in parallel opposed-slidable relationship with respect to one another. A vane structure issupported in thestraight surface so as to extend normally from it and abut the. cam surface, formingsealed chambers between the two. Fluid inlets and outlets which are spaced alongone of the members to admit andremove fluid from these chambers in such a manner as to cause relative motion of the members.

In general, the configuration may be thought of as a vane type rotary pumpor motor which has been cut along a=radius and stretched out along a straight line. The prinoiples involved in the two are similar although the present invention involves different structure necessary to attain the straight line motion.

A primary object of the present invention is to. provide a linear fluid actuator in which the fluid volume causing compression is independent of'the length of stroke.

Another object of the present invention is to produce a linear actuator which employs vanes interacting with cam areas to produce a series of expanding. chambers, which are filledunder the fluid pressure from the source andthen exhausted back to the source aslinear motion is produced. Two preferredembodiments .of the invention are disclosed in the. following description. The de-. 7 scription refers to thepaccompanying drawing inwhich:

Figure 1 is a plan view. of alinear fluidactuator which 2 employs vanes onthe movable member and afluid supply and cam structure on the-stationary memberg Figure 2 is a cross sectional elevational view of theembodiment of Figure 1 taken along line 2-2 of Figure 1;

Figure 3 is a detail of the vane retaining structure of the embodiment of Figure 1 taken along line 33 of Figure 1;

Figure 4 is a plan view ofa second embodiment of a linear fluid actuator which employs a cam structure on the movable member which coacts with vanes and fluid sources andoutlets on the stationarymemberyand Figure 5 is a cross sectional view of the embodiment of Figure 4 taken along line 5-5 of Figure4.

In the embodiment of Figures 1; 2 and3 the movable member is a long rectangular bar- 10 which carries a plurality of vanes 12' spaced at regular intervals with respect to one another along two opposite longitudinal sides of the bar. The vanes- 10 comprise rectangular plates which have their outwardly extending lengthwise edges rounded. Their lowerends are disposed in grooves'l4 which extend acrossthe width of tlie bar 10.

Springs 16 whieh may be of the coil on leaf variety are situated'in'the end of eachgroove 14 'heneath eachof the vanes 12' and act to bias. the vanes outwardly. Al ternatively. it would be possible to provide fluid under pressure beneath the vanes to bias them outwardly. As shown in Figure 3 small pins 18- extend {normally from the. barsnear their loweredges: and slidin grooves 21 forward of each of the grooves 14 and thereby act to retain the vanes 12 against sliding completely outof the grooves 14';

The. stationary, cylinder member ofthe actuatorcom prises two rectangular members 20 which have carnsurfaces 22xon their'opposing surfaces and which are maintained in spaced relationship bytwo end plates 24 which attach torsides of the members 20 toform a-rigid; hollow; rectangular structure.

The spacing between the'two plates:20 issuch that the high points 26 of the inner: cam surfaces: of the two plates 20 are separatedby a distance approximatelyequal to thethickness;of the barlth Therefore, when the bar 10 passes between these. twozpointsaitlformsa-hydraulic seal between. the two members: This end: seal between the bar 10-andthe plates-20rcan also beaccomplished by the vanesthemselves. 'Ihelow points zfii of thercannare. so: spaced! from= the high points 26:: as to maintain the vanes 12 .within thexgrooves lr4tof 'the ibar 10in; awbiasedx relationship, that is, with the pins- 18' beingseparated from the ends of the grooves 21.

At the. outer end. of. the: housing-formed bythe-plates 20 and the end members 24..the camzsurface. of they plates 20 are cut away to adeeperppint thanthe lowrpoints 28. in order to allow the. vanes to enter the area without contacting the edge of the plates 20.

Each of the plates 20.has twocircular. fluid passages 32, 34, 36 and 38'. which aredisposed along the. center line of the plates 20, and pass .through the thickness of the plates.

The passages may be threaded at their, outer ends to receive standardhydraulicfittings;

In operation, two of the lines, one on each plate 20, would be connected tothe source ofa first; higher, pressure and the other two lines would be connected to asump of a-lower, second pressure. With a connection to producemotion of the bar 10 toward the right the two. lines 32"and 3 6 would beconnected to the higherpressure and li-nes 34' and 38" would be' connected'to the lower pressure:

The high pressure from the source; would fill up the first 'chambervformed by the two vanes 13 andjliwhich were. positi'onediadjacent to the passage 32. Since the blade-15 whichformstthe right wall of thechamberex periences a higher pressure on its left side than on its right side, it produces a force which tends to move the bar toward the right. Similarly, the vane 17 which is immediately to the left of the passage 36 experiences .a lower pressure on its right than on its left wall since leakage around the vanes builds up the pressure on its left which is greater than the pressure of the sink. Therefore, the resultant force on the bar is toward the right.

As the bar begins to inove toward the right the next chamber to the left is introduced to the higher pressure. This process continues until the first filled chamber reaches one of the outlet ports 34 and 38. At that point it exhausts its fluid as it is compressed by the cam 26.

The lines 32, 34, 36 and 38-would normally connect to a reversing valve which, when shifted, would put high pressure on lines 34 and 38 and low pressure on lines 32 and 36 to cause the rod 10 to move toward the left. Neither the cam configuration nor the vane spacing is critical, subject to the limit that at least one isolating vane must exist between the high pressure source and the low pressure source at all times. However, more vanes provide intermediate chambers causing smoother operation due to pre-expansion through leakage.

It is apparent that more than one set of sources and sinks may be included along the length of a particular plate 20. For each such set another cam trough 28 must be cut in the interior surfaces of the plates 20. It would also be possible to provide only one side of the bar 10 with vanes and have the other side bear on a flat surface. Similarly, any number of reacting vane and cam surfaces could be created upon as many sides as the rod 10 may present.

An alternative embodiment of the invention is illustrated in Figures 4 and 5. The movable element comprises a substantially rectangular rod 50 which is square on 3 of these longitudinal surfaces and has a regular cam shape 52 disposed along the length of its fourth longitudinal surface. The longitudinal side 54 which is opposed to the cam surface 52 bears on a block 56 which is attached to a vane'and port housing 58 by two end plates 60 and 62. This bearing surface should have a low frictional coefiicient as may be attained through proper choice of materials or through use of anti-friction elements such as balls or rollers.

The porting and vane assembly 58 along with the bearing block 56 and the end plates 60 and 62 form a rigid rectangular structure. A manifold 64 which is supported on top of the port and Vane housing 58 has passages to connect one fluid line 66 with two ports 68 and 70 and also connect the second fluid line 72 with the other two ports 74 and 76.

Three vanes 77, 78 and 80 are disposed within the vane and port housing 58 and extend the full width of that housing. Springs 81 are located between the internal end of the vane and the bottom of the grooves in which they operate and act to bias the free, pointed or rounded ends of the blades against the adjacent portions of the cam surface 52. Here again fluid pressure might be used to provide the biasing.

The blades 77 and 80 at the ends of the housing 58 serve to seal the fluid contained within the housing and the cam troughs from the exterior. The vane 78 disposed between the ports 70 and 76 acts to isolate these ports from one another.

When the fluid line 66 is connected to a higher source pressure than is the fluid line 72, the rod 50 will move towards the right. The forces causing this motion operate in the following manner. The high points 53 and 55 of the cam 52 which are located immediately to the right of the sources 70 and 68 have higher pressures on their left sides, whilehigh points 57 and 59, immediately to the left of the sinks 74 and 76 experience low pressures on their right sides. Through leakage between the cam 4 and the block 58 this pressure differential is distributed on to each cam side.

The total movement of these forces is such as to cause the rod 50 to move toward the right. This motion is halted when the pressures on lines 66 and 72 are made equal. When the pressures are reversed, providing a higher pressure on the line 72 than on the line 66, the rod 50 moves to the left. This pressure reversal can be normally accomplished by a spool type reversing valve.

In order for the embodiment of Figures 4 and 5 to be operative, a particular relationship must exist between the number of complete contours of the cam 52 and the number of spacings of the vanes such as 77, 78 and 80. Within two vane groupings, such as are included between the vane 77 and the vane 80, an odd, integral number of cam contours must exist. This is necessary so that forces produced by the various sources and sinks are synchronized.

In the example, five cam contours exist between the two vane spacings.

It should be understood that the configuration can easily be reversed and the vanes and ports could be carried on a movable inner member While the cam contours exist on the inner surface of an outer member. Also the number of operative surfaces could be increased to the limit of the number of sides on the rod 50.

In the embodiment of Figures 4 and 5 another port and vane housing could be substituted for the block 56 which would cooperate with another cam surface cut on the lower side of the rod 50. In fact, the only general requirement for operation is that cam and vane mountings be on opposed surfaces.

Having thus described my invention I claim:

1. In a fluid actuator device in combination: a first member having a longitudinal hole passing through it; a second member having a length substantially greater than that of said first member and having a traverse crosssection substantially similar to that of said hole; parallel opposed surfaces disposed on said first and said second members, one of said parallel surfaces having a cam contour along its length, and the other of said parallel surfaces having a plurality of traverse grooves spaced along its length; vanes disposed in each of said grooves and having their extending edges abutting said cam surface; means for biasing said vanes against said cam contour; and ports for injecting and removing fluid from the chambers formed between the opposed surfaces of said first member, said second member and said vanes, whereby the fluid pressures thereby created cause relative movement between said first and said second members.

2. A fluid powered device, including a motor member having a planar surface of rectangular configuration with its length substantially greater than its width, a stator member having a cam surface disposed to face the planar surface, the cam surface varying in a direction normal to the planar surface along the length of the planar surface, a plurality of transverse grooves provided in the planar surface, the grooves being spaced from one another along the length of the planar surface, vanes disposed in the transverse grooves and having their extending edges in contact with the cam surface of the stator member, means for maintaining the edges of the vanes in constant contact with the cam surface during movement of the motor member relative to the stator member, side walls disposed relative to the motor and stator members to form fluid sealed chambers between adjacent vanes, the planar surface and the cam surface, and ports in the stator member for introducing fluid to and removing fluid from the sealed chambers to produce a movement of the motor member relative to the stator member, the movement being in the direction of the length of the planar surface- 3. A fluid powered device as recited in claim 2 wherein the transverse grooves in the planar surface are spaced at equal intervals and the cam surface varies regularly.

4, A fluid PQWfired device, including a stator member having a planar surface of rectangular configuration, a motor member of substantially greater length than its Width, a cam surface on the motor member along its length and disposed to face the planar surface on the stator member, the cam surface varying in a direction normal to the planar surface along the length of the planar surface, a plurality of transverse grooves in the planar surface, the grooves being spaced from one another along the length of the planar surface, vanes disposed in the grooves and having their extending edges in constant contact With the cam surface of the motor member, means for maintaining the edges of the vanes in contact with the cam surface during movement of the motor member relative to the stator member, side Walls disposed relative to the motor and stator members to form fluid sealed chambers between adjacent vanes, the planar surface and the cam surface, and ports in the stator member for introducing fluid to and removing fluid from the sealed chambers to produce a movement of the motor member relative to the stator member, the movement being in the direction of the length of the motor member.

5. A fluid powered device as recited in claim 4 wherein the transverse grooves in the planar surface are spaced at equal intervals and the cam surface varies regularly.

References Cited in the file of this patent UNITED STATES PATENTS 628,960 Parker July 18, 1899 761,512 Lecomte May 31, 1904 1,178,695 Yost Apr. 11, 1916 2,141,953 Hawes Dec. 27, 1938 FOREIGN PATENTS 21,188 Great Britain 1910 480,242 Canada Jan. 15, 1952

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