US2830543A

US2830543A - Fluid pressure transducer for converting rotary force to fluid pressure, or vice-versa

Info

Publication number: US2830543A
Application number: US524760A
Authority: US
Inventors: Jay M Roth
Original assignee: MECHANISMS Co
Current assignee: MECHANISMS Co
Priority date: 1955-07-27
Filing date: 1955-07-27
Publication date: 1958-04-15
Anticipated expiration: 1975-04-15

Description

United States Patent FLUID PRESSURE TRANSDUCER FOR CONVERT- INGV ROTARY FORCE TO FLUID PRESSURE, R VICE-VERSA Jay M. Roth, Uhrichsville, Ohio, assignor to Mechanisms Company, a corporation of Ohio Application July 27, 1955, Serial No. 524,760 5 Claims. (Cl. ID3-135) This invention relates to a tluid pressure transducer, namely, a mechanism capable of operation either as a pump or as a motor, and, more particularly, is concerned with a transducer of the character described wherein the rotor carries in slots radially movable vanes adapted to seal outwardly against the inner periphery of the bore of the casing receiving the rotor, b ut the vanes being called slippers for the reason that they have arcuate outer faces substantially conforming to the arcuate inner surface of the casing bore and slipping thereon.

In more conventional vane type pumps and motors, the vanes are normally confined by the sides of the vanereceiving slot, so that the vanes are allowed to have only radial movement, and the result is that the outer ends of the vanes make only line contact with the casing bore. At high pressures or high rotational speeds, this can result in rapid wear.

It has been proposed, therefore, to replace the vane of a conventional pump or motor with a slipper which can be dened as a special type of vane whose outer end is curved to substantially the same radius as the maximum radius of the bore and which lits the rotor slot with suicient clearance so that centrifugal force and Huid pressure will combine to hold the curved outer end or face of the slipper against the casing bore when the rotor is rotated. There are not a very large number of slipper-type transducers in the art, because of various problems which arise as hereinafter discussed, but U. S. PatentNo. 2,278,131 illustrates a slipper of generally square or rectangular cross section. In a construction of this patented type such `a large clearance is necessary in the rotor slot that the carry-over volume spoils the dry-lift of the pump. Additionally, in the structure shown in this patent, the throw, i. e., radial movement of the slipper, is only 5.2% of the rotor diameter so that pumping capacity is relatively small. Additionally, tests of pumps constructed in accord with Patent No. 2,278,131 using transparent casings and stroboscopic examinations of moving parts indicate that the Huid pressure acts on the slippers to move them radially inward of their slot so that the slippers do not seal with the casing bore during the important time of travel through the sealing arc.

Another effort in the art to provide a slipper-type transducer is illustrated in U. S. Patent No. 1,651,336 in which close clearance between the rotor and casing bore is provided to prevent leakage from the outlet back to the inlet. But, this clearance depends on tive manufacturing tolerances, and it is diliicult commercially to hold this clearance sutliciently small for high pressure pumping. In this patent, also, stroboscopic light examination of moving parts through transparent casings of sample pumps constructed has revealed that the slipper does not contact the rotor casing in the sealing arc due to the uid pressure tending to push the slipper radially inwardly rather than radially outwardly of the slot during at least this portion of the travel of the slipper through the sealing arc. The structure of U. S. Patent 2,278,131 alsolhas a slipper throw of only about 5% of the rotor ICC Patented Apr. 15, 195.8

2 diameter making the capacity of the pump relatively small.

Eorts to avoid. and overcome the objections to the prior art structures discussed can lead to noisy parts, tilting of the slippers to positions where the arcuate outer face of the slipper does not contact over substantially its entire area with the inner face of the casing bore, to problems of leakage, and the like.

It is the general object of my invention to avoid and overcome the foregoing and other diiculties of and objections to prior art practices by provision of a relatively, simple, inexpensive, and durable transducer capable of operation as either a pump or a motor, and which is capable of handling relatively high pressures and volume.

Another object of ,my invention is to provide a transducer of the type described in which the cross-sectional shape of each slipper and the cross-sectional shape of each slot receiving the slipper are carefully designed and correlated to insure proper positioning of the slipper in substantially full arcuate sliding contact with the inner periphery of the bore at all times, the tluid pressure is `utilized to assist in positioning the slipper in this manner, and `cocking of the slipper out of position is eliminated.

Another object of my invention is to provide in a slipper type pump or motor, a slipper having -a leading face received in a slot having a leading face, one or the other of the faces being at and the other ilatly curved or angled so as to provide a line contact between them directed substantially always at about the center of the slipper regardless of the radial position thereof.

Another object of my invention is the provision of a slipper type pump or motor in which the trailing face of the slipper is received in a slot having a trailing face which is undercut so that the trailing face of the slot is adapted to engage substantially only adjacent the outer periphery of the rotor with the trailing face of the slipper.

mother object of my invention is to provide a structure of the type described in which inlet and outlet ports are provided in the casing, these ports being separated a minimum distance just slightly greater than the distance between adjacent slippers.

Another object of my invention is to provide a slipper type pump or motor having inlet and outlet ports separated by a sealing arc and a pumping arc, one or both of which can be concentric with the rotor.

Another object of my invention is the provision of a slipper type transducer for fluid pressure and having a throw in the neighborhood of 20% of the rotor diameter to materially increase the volumetric capacity thereof.

The foregoing objects of my invention, and other objects which will become apparent as the description proceeds, are achieved by the provision of a Huid pressure transducer including a casing having a bore, a rotor journalled eccentrically in the casing and having transverse slots on its periphery, a slipper received in each slot and mounted for radial movement therein, each slipper having an arcuate outer face substantially corresponding to the arcuate inner face of the bore, and sliding thereon, a cut-back leading face on each slipper, making an angle of about 60 with the tangent to the leading edge of the arcuate outer face of the slipper, the leading face of the slot having a generally similar angle, one of said leading faces being hat and one flatly curved or angled so as to provide substantially a line Contact between the leading face of the slot and the leading face of the slipper, the trailing face of each slipper making an angle of about with the tangent to the trailing edge of the slipper, and with the trailing face of the slot being undercut so that the trailing face of the slot is adapted to contact the trailing face of the slipper only adjacent the outer periphery of the rotor. Usually the casing has opposedV inlet and outlet ports spaced apart a distance only slightly greater than the distanceV between adjacent slippers, and

a sealing arc and a pumping arc between the ports at least one of the arcs being concentric with the rotor.

` For `a better understanding of my invention, reference should' be had tothe accompanying drawings wherein Fig. 1 is a semi-diagrammatic cross-sectional view through a transducer incorporating the principles of my invention and illustrating the casing rotor and slippers; Fig. 2 is a view similar to Fig. 1 but illustrating an embodiment of the invention in whichthevpumping are is concentric with the rotor; and

Fig. 3 is a View similar to Figs. l and 2 but showng another embodiment of the invention providing a double inlet and a double outlet pump of balanced construction. More particularly, considering Fig. l, the numerall lli) indicates generally a casing having a bore 12, and inlet port 14 to which is connected a conduit 16, and outlet port 18 to which is connected a conduit 20.

Received within the bore 12 is arotor, indicated as a whole by the numeral 22, the rotor being carried upon a shaft 24 journalled in the ends of the casing 10 so as to position the rotor 22 eccentrically of the bore l2. The rotor 22 is provided with a plurality, for example four, as shown, of slots 26 extending transversely of the outer periphery of the rotor at circumferentially spaced points. Each slot 26 has a leading face 28 and a trailing face 30, so designated in the direction of rotation of the rotor 22, this being indicated by the arrow 32.

The slots 26 are of generally V or triangular shape, or more specifically, of truncated-triangle shape, the leading face 28 making an angle of about 30 with a line 34 extending from the axis of the rotor through the middle, i. e. bisecting the outer periphery of the slot 26. The trailing face 30 of the slot 26 makes a negative angle, for example of about with the bisecting line 34, so that it can be stated that the trailing face 30 of the slot is undercut, whereby only the outer edge of the trailing face 30 engages with each slipper, indicated as a whole by the numeral 36, during the operation of the transducer, as hereinafter, more particularly explained. Thus, the trailing and leading faces of each slot make an angle of about with each other in the example given. This results in an inwardly opening angle between the

trailing faces

30 and 44 of each slipper and its slot, as is clearly shown in the drawings.

Each of the slippers 36 received in the slots 26 is likewise formed of a V or triangular shape, or more particularly, of a truncated-triangular shape, as illustrated, with the leading face 38 of each slipper making an angle of about 60 with a line 40 tangent to the leading edge of the arcuate outer face 42 of the slipper, for example, an angle of 67 in the embodiment of the invention illustrated. The leading face 38 of each slipper 36 cooperates with leading face 28 of its associated slot 26 so that there is substantially only line contact between these surfaces. To accomplish this, one or the other of the faces is formed flat, and the other face is slightly curved. In the invention shown, the leading face 38 of the slipper 36 is formed with a slight curve in the manner illustrated so that line contact results between the faces 2S and 3S. Note also, that this line contact occurs substantially near the center of the slipper 36 so that no tilting movement is imparted to the slipper 36 tending to force or tilt it away from substantially full bearing contact between its arcuate outer face 42 and the bore 12 of the casing 10.

The trailing face 44 of each slipper makes an angle somewhat greater than 90 with the line 46 tangent to the trailing edge of the arcuate face 42 of the slipper 36. As a result, the trailing face 44 of the slipper 36 engages with the trailing face 30 of the slot 26 only adjacent the outer periphery of the rotor 22, in the manner described before, so that forces applied to the slipper 36 by the rotor and by the fluid pressure generated hold the slippers 36 in engagement over their arcuate faces 42 with thebore 12 of the casingl during the rotation` of' 4 the rotor and the slippers in the casing. Thus, the trailing face and the leading face of each slipper make an angle with each other of about 40 in the example given. It will be understood that in the description of the angle given that the exact angles set forth are not critical but that the angles should be in the neighborhood of those recited, for example, within a range of plus or minus 5 to plus or minus 10 degrees.

The outer face 42 of each slipper is curved to substantially the same radius as the maximum radius vof the bore 12 of the casing. There is only a slight radial travel of the slipper in passing through the sealing are indicated by the numeral 50, and also in traveling through the pumping arc, indicated by the numeral 52. Any radial travel of the slipper in passing through the sealing and pumping arcs can be eliminated by making the arc or arcs concentric with the rotor. The remainder of the bore 1 2 is made as a smooth curvesuch that the radial accelerations of the slippers are minimized during rotation. As seen in the drawings, the inner face of eacli slipper has a length in a circumferential direction of between about and about 50% of the circumferential length of its outer face 42, and the inner and outer facesv are substantially parallel.

lt will be noted that the sealing arc 50 and the pumping arc 52 are of a length just slightly greater than the distance between the slippers 36 so that slipper is always in sealing contact with the arcs 50 and 52, but with these arcs being kept to a minimum of length so that the greatest volume of fluid can be pumped, to reduce and keep to a minimum carryover volume and to prevent bypassing of fluid or leakage back to the inlet port. Fig. l also illustrates that the outlet port 18 extends nearly' to the top of the casing 10 to eliminate trapping.` l j In the operation of the apparatus of Fig. l, when functioning as a pump, the man skilled in the art will understand that the rotor 2 2 and slippers 36 contact with the ends of the casing 10 to prevent by-passing of uid. Also, that the slippers 36 take the positions shown in Fig. 1 during a rotary movement, the slippers being held in position by centrifugal force and by the iluid pressure of the uid being pumped. The trailing face 30. of the rotor 22 contacts the trailing face 44 of each slipper 36 only adjacent the outer periphery of the trailing face 30 during the movement of the slipper by the inlet 14 and through the pumping arc 52. This contact is such that it will not cock the slipper 36 to move its arcuate face 42 away from the bore 12 because the pressure 0f the iluid on the inclined leading face 38 of the slipper holds the slipper against cocking. Near the end of the pressure stroke of each slipper as it moves away from the outlet 18 and into the sealing arc 50, the uid pressure differential in the sealing are resulting from outlet pressure acting against the trailing surface of the slipper by leakage past the rotor causes each slipper to move in its slot 26 to the position shown at the upper right side of Fig. l wherein the slipper leading face 38 contacts the leading face 28 of the slot. But, in my improved construction,

` this has .been found to occur without any noise or clicking because of the relatively short distance that the slipper has to travel. The relatively large throw, marked 56 eiects relatively large volume displacement of the pump.

Inthe embodiment of the invention illustrated in Fig. l, the bore 12 is shown to be substantially circular about point 58. In the form of the invention illustrated in Fig. 2, the pumping arc 60 is made concentric with the axis of the rotor 22a, with the remainder of the bore 12a being smooth curves owing into the pumping arc 60, and with a point of substantial tangency between the rotor 22a and the casing 12a in the region of the sealing arc 62.

The embodiment of the invention illustrated in Fig. 3 illustrates a transducer 70 of balanced construction having opposed

inlets

72 and 74 and

opposed outlets

76 and 78,. Also provided are opposed pumping arcs 80 and 82,

al1-4993?@ SFFPSPECS l- 2.11.1436.. The rOtOr; isiarsr..

vided with slots 88 of the general character heretofore des-cribed, each receiving a slipper 90 of substantially the construction heretofore described, but with the number of slots and slippers being substantially doubled and with the trailing face 92 of each slipper making an angle of about 73 with a tangent to its arcuate face in the manner illustrated. Cutting down this angle from the hundred degree figure heretofore given allows the undercut on the trailing face 94 of slot 88 to be reduced to somewhat less than the figure heretofore given.

The casing of the transducer 70 is made with an oval bore 100 in the manner illustrated, and with the transducer operating as heretofore explained in conjunction with the apparatus of Fig. 1, but with the rotor being substantially counterbalanced so as to eliminate bearing wear.

From the foregoing description, it will be recognized that the objects of my invention have been achieved by the provision of relatively simple and inexpensive apparatus for performing pumping and/or motor operations to transpose fluid pressure to rotary motion or vice versa, and tests conducted with apparatus of the invention have indicated high efficiencies and ability to handle relatively large volumes of fluid and at high pressures.

While in accord with the patent statutes, certain embodiments of the invention have been illustrated and described in detail, it is to be particularly understood that the invention is not to be limited thereto or thereby, but that its scope is defined in the appended claims.

I claim:

1. A uid pressure transducer comprising a casing having a smoothly curved bore, a rotor smaller than said bore mounted Within said bore with the perimeter of the rotor substantially tangent to said bore, said rotor having a plurality of radial slipper-receiving outward divergentwalled slots extending axially thereof, said slots each having a leading face inclined about 20 to about 30 to a radius bisecting the mouth of the slot, and a slipper mounted in each slot for engaging the bore of the casing during rotation of the rotor, said casing having inlet and outlet ports communicating with its bore with a pumping arc extending from the inlet to the outlet and a sealing arc extending from the outlet to inlet in the direction of rotation, said arcs being greater than the distance between slippers, each slipper being of keystone shape in cross-section with a curved outwardly presented surface having the same curvature as the greatest curvature of the bore of the casing for sliding engagement therewith and of peripheral length slightly less than the width of the mouth of the slot, the inner surface being substantially parallel to said outwardly presented surface and only 30% to 50% as long, the angle between the diverging faces of the slots being up to about 20 less than the angle between the leading and trailing faces of the slippers, whereby contact between the trailing face of the slipper and the trailing face of the rotor slot results in an inwardly opening angle between the faces, the leading face of each slipper being substantially parallel to the leading face of its slot during movement through the sealing arc where fluid pressure differential at such arc resulting from outlet pressure acting against the trailing surface of the slipper by leakage past the rotor forces the slipper ahead against the leading face of the slot, the leading faces being shaped to have line contact therebetween.

2. A fluid pressure transducer comprising a casing having a smoothly curved bore, a rotor smaller than said bore mounted within said bore with the perimeter of the rotor substantially tangent to said bore, said rotor having a plurality of radial slipper-receiving outward divergent-walled slots extending axially thereof, and a slipper mounted in each slot for engaging the bore of the casing during rotation of the rotor, said casing having inlet and outlet ports communicating with its bore with a pumping arc extending from the inlet to the outlet and a sealing arc extending from the outlet to the inlet in the direction of rotation, said arcs being greater than the distance between slippers, said slots each having a trailing face undercut up to about 10 to a radius bisecting the mouth of the slot whereby the radially outer edge of the trailing face of the slot is adapted to engage the trailing face of a slipper in the slot during travel through the pumping arc, each slipper being of keystone shape in cross-section with a curved outwardly presented surface having the same curvature as the greatest curvature of the bore of' the casing for sliding engagement therewith and of peripheral length slightly less than the width of the mouth of the slot, an inner surface substantially parallel to and shorter than said outwardly presented surface, each slipper having a leading face and trailing face making an angle with each other of between about 35 to about 50, this being up to about 20 greater than the angle between the diverging walls of the slots, whereby contact between the trailing face of the slipper and the trailing face of the rotor slot results in an inwardly opening angle between the faces, the leading face of each slipper being substantially parallel to the leading face of its slot during movement through the sealing arc where fluid pressure differential at such arc resulting from outlet pressure acting against the trailing surface of the slipper by leakage past the rotor forces the slipper ahead against the leading face of the slot.

3. A fluid transducer as defined by claim l in which the slipper has a convex leading face to provide for rocking in line contact during adjustment movements of the slipper to maintain surface contact with the bore during the sealing arc where fiuid pressure differential at such arc resulting from outlet pressure acting against the trailing surface of the slipper by leakage past the rotor pressure forces the slipper ahead against the leading face of the slot.

4. A fluid transducer as defined by claim 1 in which at least one of the faces of the leading face of the slipper and the leading face of the slot is shaped to provide for rocking in line contact during adjustment movements of the slipper to maintain surface contact with the bore during movement through the sealing arc where fluid pressure differential at such arc resulting from outlet pressure acting against the trailing surface of the slipper by leakage past the rotor pressure forces the slipper ahead to bring its leading face against the leading face of the slot.

5. A fluid transducer as defined in claim l in which the trailing face of each slot is undercut up to about 10 to a radius bisecting the mouth of the slot so that the radially outer edge of the trailing face of the slot engages the trailing face of the slipper during travel through the pumping arc.

References Cited in the file of this patent UNITED STATES PATENTS 1,495,526 Phillips May 27, 1924 1,651,336 Wissler Nov. 29, 1927 1,898,914 Vickers Feb. 2l, 1933 2,278,131 Livermore Mar. 31, 1942 2,333,323 Livermore Nov. 2, 1943 2,371,081 Tucker et al. Mar. 6, 1945 2,462,481 Estey Feb. 22, 1949 2,499,763 Livermore Mar. 7, 1950 2,551,623 More May 8, 1951 2,628,568 Rhine Feb. 17, 1953