Патент USA US2405061код для вставки
July 30, 1946. 2,405,061 C. W: SHAW‘ PUME STRUCTURE Filed Dec. 2, 1942 2 Sheets-Sheet 1 (a I 22 (gé 1N VEN TOR fzdrgyce 9/ Ame_ ATTORNEYS July 30, 1946. c. w. SHAW PUMP STRUCTURE Filed Dec. 2, 1942 2,405,061 v 2 Sheets-Sheet 2 . INVENTOR (‘Zara/70¢? W554 m E-i- @?éé A TTORNE Y5. 2,405,061 Patented July 30, 1946 UNITED STATES PATENT OFFICE 2,405,061 PUMP STRUCTURE Clarence W. Shaw, Grosse Pointe Woods, Mich, assignor to Eaton Manufacturing Company, Cleveland, Ohio, a corporation of Ohio Application December 2, 1942, Serial No. 467,565 5 Claims. (Cl. 103—-42) 2 1 having end walls cooperating with the end faces thereof, one of the walls being movable toward This invention relates to fluid pumps and par» ticularly to pumps of the rotating positive dis and from the other thereof and said other of said placement type, the principal object being the end walls having inlet and outlet ports leading provision of a pump structure of this type of therethrough to said rotors or gear-like elements, and the outer of said gear-like elements is mov able axially toward and away from the second mentioned end wall in accordance with variations in pressure on the discharge side of said pump improved design and construction providing im~ proved pumping characteristics. Objects of the invention include the provision of a rotating pump of the positive displacement type capable of maintaining a predetermined pressure on the discharge side thereof within 10 whereby to provide for direct by-pass of fluid between said inlet and said outlet without the extremely close limits over a wide range of speeds; necessity of passing through the gear-like ele the provision of a pump of the type described particularly adapted for supplying fuel under ments; the provision of a pump structure as above described in which the outer gear-like element is pressure to internal combustion engines; the pro vision of a pump of the type described which is 15 normally urged towards engagement with the ?xed wall of the housing through engagement with the movable wall thereof but in which it is freely movable axially between the ?xed wall and particularly efficient in passing volumes of gas therethrough which may become entrapped in the liquid being pumped thereby; and the provision of a pump of the type described in which the by the movable wall whenever the movable wall is passing of excess fluid between the discharge and 20 retracted under the force of the discharge pres intake side of the pump is accomplished in- a sure of the pump; and the provision of a pump simple, accurate and efficient manner. structure of the type described in which the by Other objects of the invention include the pro passing of ?uid between the inlet and outlet sides vision of a rotating positive displacement type of the pump for the purposes of controlling the of pump including inner and outer gear-like ele 25 discharge pressure is accomplished in an easy and ments rotating in a, surrounding casing and in ef?cient manner. which one side of the gear-like element is pro Still further objects of the present invention is vided with a cooperating wall movable toward the provision of a pump structure as above de and from the same to provide for by~passing scribed in which a ?lter or strainer is incorpo fluid between the inlet and outlet sides of the 3 l. rated in the pump in a simple and ef?cient man pump to maintain a predetermined pressure, the ner; and the provision of“ a pump structure as wall being mounted for movement axially on a above described in which a ?lter or strainer of rotating part whereby to eliminate the presence relatively large surface area is incorporated with of static friction opposing this pressure control . in the pump. ling movement; the provision of a pump of the The above being among the objects of the pres type described in which the discharge pressure of ent invention, the same consists in certain novel the pump acting on one face of the movable wall thereof is limited to a de?nite area of such wall features of construction and combinations of parts to be hereinafter described with reference and the suction pressure of the pump is applied to the entire opposite face thereof; the provision at of a pump structure as above described in which the movable wall is formed for direct equalization between the suction pressure of the pump on one face thereof and the entire opposite face of the wall; the provision of a pump structure as above described in which the suction pressure of the pump is substantially atmospheric; and the pro vision of a pump structure of the type described in which the movable wall is provided with novel means for preventing its rotation upon its ro 50 tatable support. Further objects of the present invention include the provision of a pump structure including in~ ternal and external inter-meshing gear-like pumping elements and a cooperating housing to the accompanying drawings, and then claimed, having the above and other objects in view. In the accompanying drawings which illustrate suitable embodiments of the present invention and in which like numerals refer to like parts throughout the several different views, Fig, 1 is a vertical sectional view taken axially through a pump structure embodying certain fea tures of the present invention; Fig. 2 is a vertical sectional view taken trans versely of the pump structure shown in Fig. 1 as on the line 2—2 thereof; Fig. 3 is a vertical sectional view taken trans versely of the pump structure shown in Fig. 1 as on the line 3——3 thereof; Fig. 4 is a fragmentary, vertical sectional view 2,405,061 3 4 . taken transversely of the pump structure shown portion 28 in suitable bearings 33 carried thereby in Fig. l as on the line 4-4 thereof; and projects into the chamber formed within the Fig. 5 is a fragmentary, horizontal sectional cap 32. The righthand face of the main body view taken on the line 5~—5 of Fig. 4 to better portion 28 is disposed perpendicular to the axis illustrate the means employed for preventing the 5 of rotation of the shaft 32 and the inner rotor 20 movable end wall from rotating with its support is mounted on the shaft 32 in substantial contact ing shaft; with the righthand face of the housing 28. Any Fig. 6 is a fragmentary view of a, portion of the suitable means such as a key 34 may be pro construction illustrated in Fig. l to show the vided between the shaft 32 and the inner rotor 20 position of the movable end wall and the outer to constrain the two for equal rotation with each rotor under actual pumping conditions; other. Preferably some means is provided to lock Fig. 7 is a vertical sectional view taken axially the inner rotor against outward movement on the through a modi?ed form of pump structure; shaft 22, and a snap ring 35 partially received in Figs. 8 and 9 are vertical sectional views taken a complementary peripheral groove in the shaft transversely of the pump structure shown in Fig. 15 32 and abutting the righthand face of the rotor '7 as on the line 8-8 and 9-—9, respectively, there 2:3 is shown in Fig. 1 for this purpose. The cap of; member 36 receives therein a wear ring or bush Fig. 10 is a view similar to Fig. '7 but showing ing 36 in transverse alignment with the inner a modi?ed form of construction; rotor 20 and within which the outer rotor 22 is Fig. 11 is a vertical sectional view taken trans rotatably received. As is evident from an inspec versely of the pump structure shown in Fig. 10 20 tion of Figs. 2 and 3 the ring at‘ is eccentric to the as on the line H-H thereof; and, axis of the shaft 32 so as to position the rotors 20 Fig. 12 is a fragmentary, vertical sectional view and ‘22 in the proper relation with respect to each taken axially through a pump structure of the other as indicated in Fig. 3. general type shown in the preceding views and The righthand face of the main body portion 25 illustrating a modi?ed form of construction for as best brought out in Fig. 2 is provided with preventing rotation of the movable wall with re an intake port 38 and an outlet port 40, these spect to its rotating support. ports being, of segmental conformation and ex In the broader aspects the present invention is tending approximately circumferentially with capable of use in connection with various types of rotatable pumps of the positive displacement 30 respect to the axis of the shaft 32 in overlapping or encompassing relation to the space exposed at type and where the language of the claims so per one end of the rotors 20 and 22 between the teeth mits they are to be interpreted in this broad thereof and each at one side of a plane including sense. The invention is, however, particularly the axis of the shaft 32 and passing centrally adapted for use in connection with those types of through the point of full mesh of the rotors. 35 positive displacement rotary pumps that include They approach each other relatively closely at inner and outer members having inter-engage able tooth-like elements. One such type of pump is illustrated in United States Patent No. the point of full mesh where the teeth of the in ner and outer rotors completely engage one an other and are spaced from each other to a great 1,682,563, issued August 28, 1928 to Myron F. Hill 40 er extent at their opposite ends where such teeth on Internal rotors, and, accordingly, such type are spaced from each other by a maximum dis of pump structure is illustrated in the drawings tance, The inlet port 38 leads into an intake by way of explanation. Accordingly, in each of the pumps shown in the drawings there is an in ner rotor 29 and an outer rotor 22, each of these rotors having tooth-like projections 24 and 26, passage 42 within the main body portion 28 from which an opening 44 leads to an exterior face of the main body portion 28. Such opening may be threaded for reception of an intake pipe or tube such as 45. The outlet port 40 is similarly con other, The inner rotor is mounted eccentrically nected to a discharge passage 48 which com to but on an axis parallel with the axis of rotation municates with an opening 50 leading to an ex of the outer rotor, this eccentricity being such 50 terior face of the main body portion 28 and which that at one point in the circumference of the may be threaded for reception of a discharge pipe respectively, which teeth intermesh with one an pumping chamber which lies in the plane includ or tube such as 52. ing the axes of rotation of the rotors 20 and 22 The shaft 32 projects to the right beyond the the teeth of the rotors completely engage one an inner rotor 29 and rotatably mounted upon such other and a tooth of one substantially complete 55 projecting end and within the cap member 30 is a ly ?lls the space between the teeth of the other. plate member 54 of an outside diameter substan The outer rotor has one more tooth 26 than the tially equal to the outside diameter of the outer number of teeth 24 of the inner rotor, the ar rotor 22. The lefthand face of the plate member rangement and design of the rotors being such 54 is flat and is constantly urged toward the left that the teeth 24 and 26 are at all times in sub 60 into contacting relationship with respect to the stantial engagement with one another. Thus corresponding faces of the inner and outer rotors from the point of full engagement of the teeth 20 and 22, respectively, by means of a coil spring with one another when there is substantially no 56 which is maintained under compression be space between them the teeth, during rotation of tween the plate member 54 and the end wall of the rotors, ?rst recede from one another and then 65 the cap member 30. The actual pumping cham approach one another during each revolution of ber is thus formed between the righthand end of the rotors to provide variable volume chambers the main body portion 28 and the movable plate through which the pumping effect is obtained. member 54 within the wear ring 36, and the plate In the construction illustrated in Figs. 1 to 6, member 54 thus forms a movable wall for this inclusive, the housing for the pump comprises a 70 pumping chamber which is capable of moving main body portion 23 inthe form of a casting having a flat righthand face, and a cap member 3i) suitably mounted and piloted on the righthand end thereof as viewed in Fig. l. A shaft 32 is rotatably mounted centrally of the main body 75 axially of the shaft 32 against the force of the spring 55 in response to variations of pressure in the pumping chamber to maintain the dis charge pressure substantially constant. This general type of construction, that is one 2,405,061 5 which employs a spring pressed plate to form a movable wall for one side of a pumping chamber is in itself broadly old, but in constructions as heretofore suggested I have found that it is im possible to accurately control the discharge pres sure within the narrow limits required, for in stance, in supplying fuel to internal combustion engines, for the reason that when the pump is driven at high speed the discharge pressure is built up beyond permissible limits. The construc tion shown involves certain departures from the prior. art along this general line through the me dium of which the discharge pressures may be 6 speeds is that in all prior constructions that I am aware of the discharge pressure of the pump acted over substantially one-half the area of the movable wall and the suction pressure acted over the remaining half thereof, the tendency of the two pressures thus being to cook the plate rela tive to its guiding means thereby increasing the static friction which it was necessary to overcome before movement of the plate or movable end wall could occur in response to pressures existing in the discharge side of the pump. In accordance with the present invention such plate or movable end wall is either cut away or apertured on the suction side of the pumping element or elements gardless of the speed of the pump and these will 15 so as to transmit the suction pressure on the pump to the back face of the movable plate or now be discussed. One reason why the pressures end wall. This feature, therefore, effects an in the prior art pumps of this general type can equalization of the suction pressure acting on the not be accurately controlled is that the mova operative face of the movable end wall with the ble wall was conventionally supported on ?xed pins or the like between which and the movable 20 pressure existing behind it and thus eliminates any pressure differential between the two opposite wall static friction necessarily existed. In order maintained within the required tolerances re to overcome this static friction in order to ad» just itself to variations in pressure of the dis charge side of the ‘pump in an attempt to main tain a constant pressure the movable wall neces sarily was required to overcome the static friction between it and its guiding means. The result was sides of the plate or movable end wall over that area thereof subject to the suction pressure of the pump and on the operative face thereof. In the construction illustrated in Figs. 1 to 6, 25 inclusive, the end wall 54 is provided with a slot 62 for the above described purposes, the slot 62 opening onto the adjacent marginal faces of the that when the speed of the pump increased and inner and outer rotors 20 and 22, respectively, at the volume pumped therefor increased, the dis~ charge pressure was required to build up to an 30 that point in the position of rotation thereof which is subjected to the suction pressures exist undesirable degree before it could overcome such ing in the pump, Thus it will be appreciated that static friction and cause the movable wall to all of the space within the cap 30 back of the plate properly respond in accordance therewith. Like 5-5, or to the right thereof as viewed in Fig. 1, is wise when the speed of the pump was decreased and the volume pumped thereby correspondingly 36 subjected to the suction pressure of the pump and, therefore, the entire rear face of the plate mem decreased the discharge pressure would drop‘ be ber or movable wall 54 is subject to such suction low a desired minimum ?gure before the forces pressure. In this connection it wili be readily acting on the movable wall could overcome the appreciated by those skilled in the art that in static friction and allow the movable wall to move to accommodate such change in volume. 40 many cases and perhaps the most cases, depend ing upon the position of the supply point from In the present case, the movable wall in being which the pump draws its liquid to be pumped, mounted upon the shaft 32 is mounted upon a the pressure acting on the rear face of the plate rotating part so that no static friction exists 54 will be atmospheric pressure or substantially between it and the shaft. Thus the static fric tion which caused the trouble in conventional 45 such pressure. In any event the pressure which exists on the back face of the movable wall of constructions is eliminated in this construction plate member 54 will remain substantially conin this respect. The only static friction necessary 'stant throughout the entire operation of the to be overcome .in the pump shown in Figs. 1 to 6, pu'itip. As a result of the above described con inclusive, is that in the connection between the movable wall 54 and the cap 30 for maintaining 60 struction the only force effective on the operative face of the plate member or movable wall 54 is the movable wail against relative rotation with the discharge pressure of the pump and this is respect to the housing. This means, as illustrated aided by the suction pressure of the pump which best in Figs. ‘4 and 5, consists of a pin 58 secured exists on an equivalent area from the back face in the movable wall or plate member 54 in parallel relation with respect to the axis of the shaft 32 55 thereof, in opposition to the force of the spring 56. With the above described construction and un and projecting to the right therefrom as viewed less compensated for, the center of pressure act in Fig. 5. The cap member 30 is provided with a ing on the plate or movable Wall member 54 would hollow boss 60 within which the pin 58 is axially still be concentrated on the plate or movable end loosely slidably received. It will be appreciated that, of course, the amount of static friction 60 wall member 54 on one side of the axis of the shaft 32 and would still have a tendency to cause which is required to be overcome to eifect move the plate or movable end wall 54 to become cooked ment of the pin 58 within the hollow boss 60 is on the shaft. This possible disadvantage is over extremely small and offers no material resistance come in accordance with a further phase of the to axial movement of the movable wall for plate member 54 in response to changes in pressure 65 present invention. According to this later-men tioned phase the spring 56 is so’ located with re acting upon the same. It will be noted that the spect to the plate or movable end wall member periphery of the movable wall or plate member 54 that it acts centrally of the center of pressure 54 is spaced from the inner walls of cap member of the discharge side of the pump on the plate 30 so that no static resistance can be set up at this point which would interfere with the free axial 70 or movable end wall 54. In other words and as best brought out in Fig. 1 the spring 56 is not movement of the plate member 54. concentric with the shaft 32 but is arranged with Another reason why rotor pumps of the prior its axis radially offset from the axis of the shaft art employing a spring pressed end wall were not 32 toward the discharge side of the pump, the able to accurately control the discharge pressure of the pumps over a relatively wide range of 76 amount of offset being ‘such that the center of 7 2,405,061 pressure of the spring 56 and the center of pres sure of the discharge side of the pump on the plate member 54 are substantially coincident with one another. To maintain the spring 56 in such positionv the plate 54 is provided on its back face with an outstanding boss portion 54, best brought out in Fig. 4, which is disposed at the desired eccentricity and direction of offset with respect to the axis of the shaft 32 for the spring 56. The 8 a direct passage is provided between the outer rotor and the main body portion 28 between the inlet port 38 and the outlet port 40 around the exterior of the inner rotor 20 through which the liquid may ?ow or by-pass to maintain a con stant discharge pressure. This feature is very important inasmuch as in the prior types of pumps where the outer rotor is not capable of following the movement of the plate member closed end wall portion of the cup-shaped cover 10 and where, for instance, the pump is intended to 35, is likewise offset from the axis of the shaft 32 maintain a constant pressure of five pounds per so that the spring 56 in seating against the end square inch gage, as the speed of rotation of the wall thereof will be arranged at the desired eccen pump is increased the pressure increases up to as tricity with respect to the axis of the shaft 32. much as ?fteen pounds per square inch solely Thus the pressure of the spring 56 and the dis 15 because of the resistance to flow of the liquid charge pressure of the pump on the opposite face between the two pumping elements. With the of the plate member 54 are balanced so as to present construction and because such Icy-passed eliminate any cocking tendency of the plate mem liquid is not forced to flow through the pumping ber 54 of the shaft 32. The result is that the plate elements but is provided with a free and direct member 54 is freely movable on the shaft 32 and path of ?ow between the inlet and outlet sides of being substantially free of any static friction in the pump, it has been found that the discharge its axial movement is free to move in response to extremely slight variations of pressure on the dis charge side of the pump to maintain such pres~ sure constant. The sensitivity of the plate mem ber 54 to changes in pressure on the discharge side of the pump is, of course, increased if the plate member 54 is constructed from a light metal pressure of the pump may be maintained ex tremely close to the desired maximum pressure for which the pump is adjusted even under those conditions where pumps designed according to the prior art as above described build up two or three times the desired pressure. The above described pump may, of course, be such as aluminum or magnesium or suitable alloys mounted and driven in any suitable manner. In thereof. This is preferably done. In such case 30 the particular construction shown the lefthand the plate member 54 has less inertia to be over end of the main body portion 28 is provided with come in effecting movement thereof than where a flat face 10 arranged perpendicularly with re constructed of a heavier metal as will be appre spect to the axis of the shaft 32 and is centrally ciated by those skilled in the art. provided with an annular pilot portion 12. Ac It will be noted from an inspection of Figs. 35 cordingly, this pump is adapted to be received 1 and 6 that the inside diameter of the wear ring upon a ?at face provided upon the crankcase or or bushing 35 is less than the inside diameter of other structural part of an internal combustion the cap member 30 immediately to the right engine with the pilot portion T2 closely ?tting an thereof. Accordingly, it is possible for the outer opening provided therein for properly locating it rotor 22 to move to the right with the plate mem 40 on such face. The shaft 32 may, of course, be ber 54 as the latter recedes under increased pres~ sure within the pump chamber and this actually and desirably occurs as indicated in Fig. 6 which illustrates the plate member in receded position. This movement of the outer rotor 22 may be caused by the fact that its right-hand face be ing in ?at contacting relation with respect tojthe operative face of the plate member 54 is sealed against the flow of liquid under the discharge pressure in the pump between them, while its lefthand face is at least partially exposed to the discharge pressure of the pump in the discharge port 4-0. Whatever the reason, the outer rotor 22 does follow the movement of the plate 54 in the latter’s movement toward or from the op posed face of the inner rotor 20, in response to variations in the discharge pressure of the pump. The fact that the outer rotor 22 follows the movement of the plate 54 is important for the fol lowing reasons. If this movement did not occur, then as the plate member 54 receded from the rotors under an increased pressure and in order to permit a larger volume of liquid to be bypassed between the inlet and outlet sides of the rotors in an attempt to maintain a constant discharge pressure, it would require the by-passed liquid to flow axially through the length of the pump before it could be by-passed to the opposite side of the rotors. This ?ow of the liquid axially through the length of the pump under such cir cumstances is not required where the outer rotor follows the movement of the plate member 54 in accordance with the present invention as in such case as soon as the outer rotor moves away from connected in any suitable manner to a rotating part of such engine but in the particular con struction shown the lefthand end of the shaft 32 is hollow and its outer end portion is interiorly provided with axially parallel serrations 14. A stub shaft 76 provided exteriorly with axially parallel serrations 78 has one end thereof re ceived within the end of the shaft 32 with the serrations 18 thereof inter?tting with the serra~ tions 74 of the shaft 32. To maintain the stub shaft 16 against axial movement with respect to the shaft 32 a snap ring 80 is partially received within a groove formed circumferentially of the stub shaft 16 in the outer portions of the serra tions 18 thereof and abuts against the outer end of the shaft 32. A similar Snap ring 82 partially received within a groove formed at the right hand or inner end of the stub shaft 16 bears against the inner ends of the serrations 14 of the shaft 32 to lock the stub shaft 15 against out ward movement with respect to the shaft 32'. A suitable hollow drive shaft (not shown) having internal serrations corresponding to the serra tions '14 of the shaft 32 may envelope the outer end of the stub shaft it so that the driving force may be transmitted therefrom to the stub shaft 16 and from the stub shaft 16 to the shaft 32. The fit between the serrations 14 and 18 and also preferably between the serrations 18 and those of the driving shaft above explained but not shown, is sufficiently loose to permit a limited amount of universal movement of the stub shaft 16 in the shaft 32 and also in the drive shaft so as to eliminate the necessity of aligning the shaft the cooperating face of the main body portion 28, 75 32 with the drive shaft with absolute accuracy. 2,405,061 In order to prevent the possibility of fuel es caping along the shaft 32 and into the crankcase or other part of the internal combustion engine where the pump is mounted directly upon the same, the lefthand face of the main body por tion 28 is provided with a recess 84 around the corresponding end of the shaft 32 and within which a sealing device 85 is pressed. The recess 04 is provided with a smaller extension inwardly of the sealing device 85 forming a pocket 86 between the outer bearing 33 and the sealing de vice and this pocket is connected by a passage 81 with the suction passage 42 so as to permit a small amount of the pumped liquid to circulate over the bearing 33 for lubrication and any liquid that is pumped between the shaft 32 and the outer bearing 33 will be drawn back into the pump, thus preventing any liquid from ?nding its way along the shaft 32 into the engine. It will be appreciated from the foregoing de 20 scription and explanation that in accordance with the present invention certain improvements have been incorporated in a pump of the general type described which overcomes disadvantages in similar pumps constructed in accordance with the prior art and that as a result of such im provements a pump having improved operating characteristics is provided. Invthe construction illustrated in Figs. '7, 8, and 9 the main body portion 28a and the cap mem ber 30a correspond with the main body portion 20 and cap member 30 of the previously described construction. Likewise the shaft 32a and the inner and outer rotors 20a and 22a, respectively, correspond with the shaft 32 and inner and outer rotors 40 and 22 of the previously described con struction. The cap member 30a in this case in stead of terminating at its transverse 0r end wall as in the ?rst construction has its side walls ex tended therebeyond and the outer ends of the same are closed by a sheet metal cap 90 which is secured to the cap member 30a by means of a screw 02 threaded into an outwardly projecting boss 04 formed on the transverse wall of the cap member 30a. An inlet passage 96 is provided through such side wall extension and is inter nally threaded for reception of an intake pipe or tube 98. The sheet metal cap 90 is provided with an inwardly projecting central boss portion I00 and the boss 94 is enlarged near its base and between these two portions a cylindrical screen I02 is mounted, the ends having a close ?t with such portions. A passage I04 is provided through 10 32a and collaborates with‘ the plate 54a in sub stantially the same manner as the spring 56 co operates with the plate 54 in the previously de scribed construction. In the construction illus trated in Figs. '7, 8, and 9 no wear ring'such as the wear ring 36 in the previously described con struction is provided but instead the outer rotor 22a has bearing directly in the cap member 30a and is capable of moving axially therein with the plate member'54a in the same general manner as the equivalent parts in the previously described construction. _ It will be appreciated that in the construction illustrated in Figs. '7, 8, and 9 the liquid flowing into the pump is admitted to one side of the rotors 20a and 22a while the main body portion is pro vided with a discharge port Ma on the opposite side of the rotors, the port 40a being connected to a discharge passage 48a which leads to the ex terior face of the main body portion 28a in the same general manner as the discharge passage 48 in the previously described construction. Ac cordingly, the liquid being uinped must flow ax ially through the full width" f the rotors in pass ing through the pump and, unless otherwise taken care of, the advantages described in‘ connection with the ?rst described structure in being able to by-pass liquid between the intake and dis-v charge sides of the pump without flowing through the rotors would not be realized. To obtain this same advantage the main body portion 20a is provided with a port 38a of substantially the same shape and contour as the inlet port 38 of the previously described construction but, of course, ': in this case such inlet port does not lead to the exterior face of the housing 28a. The only func tion of the port 38a is when the outer rotor 22a moves axially with the plate member 54a away from the coacting face of the main body portion 28a upon increase in volume ofthe liquid being pumped, liquid may be by-passed directly be tween the passage 38a and the discharge port 40a in exactly the same manner as in the previously described construction and without necessitating such liquid flowing through the length of the ro tors. The only volume of liquid that will ?ow axially through the length of the rotors will be that actually discharged from the pump. Thus with the construction illustrated in Figs. '7, 8, and 9 the same lay-passing effect as in the previously described construction is obtained. In the construction illustrated in Figs. '7, 8, and 9 the outer end of the shaft 32a is sealed against leakage of the fluid being pumped by means of the transverse wall of the cap member 30a from a conventional type of seal Ill] and a drainage the space within the screen I02 so that the liquid 55 passage IIZ which connects the bearing for the ?owing through the inlet passage 95 must flow shaft 32a in the main body portion .280. with the through the screen I02 before it may ?ow through passage 38a which is, of course, under the suc the passage I04 to the space within the cap mem tion pressure of the pump and which, therefore, ber 30a to the right of the rotors 20a and 22a. serves the same purpose as the passage 87 in the The screen I02 is of such ?neness as to ?lter out ?rst described construction. foreign particles of objectionable size from the It may also be noted that in the construction fluid being pumped. ‘ ' illustrated in Figs. '7, 8, and 9 the inner end of the Between the rotors 20a and 22a and the trans shaft 32a is reduced in diameter and that the verse wall of the cap member 30a a plate member 65 plate member 54a is rotatably mounted upon this 54a, corresponding to the plate member 54 in the previously described construction, is provided, but in this case instead of providing an opening such as 62 ‘in the previously described plate on the ‘suction side thereof, the same side of the plate is-cut off as best illustrated at I116 in Fig. 9, this having the same effect as providing the open ing or slot 62 in the previously described con struction. Thespring 56a which corresponds with the spring 56 previously described is arranged eccentrically with respect to the axis of the shaft reduced diameter portion. Also, that the trans verse wall of the cap member 39a is provided with a central pocket in which a bushing II4, for the inner end of the shaft 32a is received. The bush ing H4, therefore, provides an outboard bearing for the shaft 32a. It may also be noted that in stead of the pin and boss construction employed in the ?rst described construction for maintain ing the plate member 540. against rotation, in the construction illustrated in Figs. '7, 8, and 9 the 2,405,061 r l1 plate member 54a, as best brought out in Fig. 9, is provided with an integral radially projecting 12 housing movable axially with respect to said rotors and relatively rotatable with respect thereto, said‘ projection or boss H6 on its periphery which is wall having a flat face arranged in parallel and loosely received within the groove or notch H8 formed in the inner wall of the cap member 30a, 11 opposed relation with respect to the end faces of said rotors remote from said face of said hous~ this construction simply providing an alternative method of maintaining the plate member 54a against rotation with the shaft 32a. In the construction illustrated in Figs. 10 and 11 the same main body portion 28a is employed , as in the construction illustrated in ‘Figs. '7, 8, and 9. The cap member 301) is different, however, the extended side wall portions of the construc tion illustrated in Figs. 7, 8, and 9 being elim~ inated as well as the ?lter screen and sheet metal cap employed in the previous construction. In this case the cap is provided with an inlet pas~ ing, spring means constantly urging said movable wall toward said face of said housing, said face of said housing being provided with a pair of ports therein one registering with the suction side of said rotors and the other registering with the discharge side of said rotors forming the sole means for admitting and discharging ?uid through said housing to and from the space with in said rotor, the outer of said rotors being pe ripherally imperforate and bodily shiftable ax ially in said housing whereby said outer rotor may follow the movement of said movable wall in the movement of the latter toward. and from said face of said housing in response to variations in respectively, which are the same as in the pre~ 20 pressure on the discharge side of said pump sage I20, threaded to receive an inlet pipe I22, which discharges directly into the space between the righthand end of the rotors 20a and 2211. viously described construction, and the end wall of the cap member 301). The plate member 5413 and spring 56b are substantially the same as the plate member 54a and the spring 56a in the pre viously described construction. In this case the structure, whereby to provide a by-pass passage of varying cross-sectional area between said outer rotor and said face of said housing between said ports and said movable wall being formed to pro vide constant open communication between the suction side of said pump and that face of said shaft 32b, corresponding with the shafts 32 and well remote from said rotors. 32a of the previously described constructions, is 2. In a pump structure, in combination, a hous provided with an enlarged inner end I24 upon ing having a ?at face therein, a shaft rotatably which the plate member 54b is rotatably received and the extreme free end portion of which is ro 30 mounted in said housing in perpendicular rela tionwith respect to said face, an inner rotor driv tatably received in a bushing I26 carried by the ingly connected to said shaft within said housing transverse end wall of the cap member 30b. The in substantial contact with said face, an outer plate member 541) in this case is cut away on its rotor within said housing surrounding said inner suction side in the same manner as in the con struction of the plate member shown in Figs. '7, 35 rotor in eccentric relation with respect thereto, a wall within said housing movable axially with 81, and 9 but in this case instead of being held respect to said rotors and relatively rotatable with against rotation in the same manner as in such respect thereto, said wall arranged in opposed re previously described construction, the plate mem lation with respect to those end faces of said ber 54b is provided with a notch I30 in its'periph cry and the cap member 30b is provided with an 40 rotors remote from said flat face of said housing, spring means constantly urging said movable wall integral inwardly projecting rib or boss I32 which is received therein. Otherwise the construction illustratedin Figs. 10 and 11 is the same as that illustrated in Figs. '7, 8, and 9 and functions in the same manner. 7 toward said ?at face of said housing, said ?at face of said housing having a pair of ports therein one of which is in communication with the inlet side of the pumping space between said rotors and the other of which is in communication with the discharge side of the pumping space between said rotors forming the sole means for admit In Fig. 12 a modi?ed form of construction for maintaining the plate or movable end wall mem ber against rotation with respect to the enclosing cap member is illustrated. The shaft in this case is illustrated at 320, the cap member at 30c, ‘ the outer rotor at 220, the inner rotor at 200, the movable end wall of plate member at 54c, and its cooperating spring at 56c, and all of which parts correspond with the equivalently numbered parts of under the influence of the discharge pressure acting on that end face thereof opposed to said of the previously described constructions and ' which function in the same general manner. In outer rotor to follow the movement of said mov ting and discharging ?uid through said housing to and from the space within said rotor, the outer of said rotors being peripherally imperforate and bodily movable Within said housing axially there flat face of said housing whereby to enable said this case, however, the plate member 540 is pro able wall in response to variations in discharge pressure occurring in said pump, thereby provid ing a by-pass passage of varying cross-sectional‘ (30 size between said outer rotor and said ?at face cap member 300 is provided with a hollow boss of said housing and extending between said I42 in which the projection I40 is loosely received ports, and said movable wall being formed to pro thus to maintain the plate member 540 against vide constant open communication between the rotation with the shaft 326. suction side of said pump and that face of said Having thus described my invention, what I wall remote from said rotors. claim by Letters Patent is: 3. In a rotary pump, in combination, a housing 1. In a rotary pump, in combination, a housing having a flat face therein, a shaft rotatably having a substantially ?at face therein, a shaft mounted in said housing in perpendicular rela rotatably mounted in said housing in perpendic tionship with respect to said face, a peripherally ular relation with respect to said face and project imperforate inner rotor within said housing fixed ing therebeyond, a pair of rotors within said hous for equal rotation with said shaft in concentric ing arranged with one end face of each thereof relation with respect thereto and said shaft pro in opposed and parallel relation with respect to jecting beyond one end of said rotor, a second said face of said housing and one of said rotors peripherally imperforate rotor in said housing in being driven by said shaft, a wall within said, vided with an integral axially parallel pin portion I 40 cast integrally therewith and projecting to the right therefrom as viewed in Fig. 12. The enveloping and eccentric relation with respect 2,405,061 13 to said inner rotor, said rotors providing co operating pumping elements, said face of said housing having an inlet and an outlet port ar 14 mounted on said projecting end of said shaft within said housing, means cooperating between said wall and housing preventing relative rota tion between said wall and housing, and single spring means cooperating between said housing and wall constantly urging said wall towards said rotors, said spring means being arranged in ec centric relation with respect to the axis of said shaft and with the center of pressure thereof ranged in operative relation with respect to the suction and discharge sides of said rotors respec tively and forming the sole means for the intro duction and discharge of liquid to and from said rotors, a wall relatively rotatably and axially mov ably mounted on said projecting end of said shaft within said housing, means cooperating between 10 approximately in balancing relation with respect to the discharge pressure of said pump acting on said wall and housing preventing relative rota 'he opposite side of said wall. tion between said wall and housing, said wall be 5. In a rotary pump, in combination, a housing ing formed to provide constant open communi having a ?at face therein, a shaft rotatably cation between the suction side of said rotors and that face of said wall remote from said rotors, 15 mounted in said housing in perpendicular rela tionship with respect to said face, a peripherally and spring means cooperating between said hous~ imperforate inner rotor within said housing ?xed ing and wall constantly urging said wall towards for equal rotation with said shaft in concentric said rotors, said spring means being arranged in relation with respect thereto and said shaft pro eccentric relation with respect to the aXiS of said jecting beyond one end of said rotor, a second shaft and with the center of pressure thereof peripherally imperforate rotor in said housing in approximately in balancing relation with. respect enveloping and eccentric relation with respect to to the discharge pressure of said pump acting on said inner rotor, said rotors providing cooperat the opposite side of said wall. ing pumping elements, said face of said housing 4. In a rotary pump, in combination, a housing having a ?at face therein, a shaft rotatably having an inlet and an outlet port arranged in mounted in said housing in perpendicular rela tionship with respect to said face, a peripherally imperforate inner rotor Within said housing ?xed for equal rotation with said shaft in concentric relation with respect thereto and said shaft pro forming the sole means for the introduction and discharge of liquid to and from said rotors, a wall jecting beyond one end of said rotor, a second ' peripherally imperforate rotor in said housing in enveloping and eccentric relation with respect to said inner rotor, said rotors providing coopera ing pumping elements, said face of said housing having an inlet and an outlet port arranged in operative relation with respect to the suction and discharge sides of said rotors respectively and forming the sole means for the introduction and discharge of liquid to and from said rotors, a wall relatively rotatably and axially movably operative relation with respect to the suction and discharge sides of said rotors respectively and relatively rotatably and axially movably mounted on said projecting end of said shaft within said housing, means cooperating between said wall and housing preventing relative rotation between said wall and housing, said wall being formed to provide constant open communication between the suction side of said rotors and that face of said wall remote from said rotors, and spring means cooperating between said housing and wall con stantly urging said wall towards said rotors. CLARENCE W. SHAW.