US2336479A - Pump construction - Google Patents

Description

a 5676 E67 fiat? Dec. 14, 1943.

F. J. GRAEF 2,336,479 PUMP CONSTRUCTION Filed May a, 1939 2 Sheets-Sheet 1 i7 v fl as f I8 K War] an a0 l3 no 17 :2 F 53 17 -4 fie.

IE. liq. lib \EJIL lab INVENTOR.

Forrest JGlFaef @0 1/ y ffzww TTORNEYJ.

Dec. 14, 1943.

PUMP CONSTRUCTION Filed May 8. 1939 INVENTOR.

F. J. GRAEF 2,336,479

2 sheets-sheet 2 A TTORNEYJ Patented' Dec. 14. 1943 2,336,479 PUMP CONSTRUCTION Forrest J. Graef, Fort Wayne, .Ind.-, assignor to Tokheim Oil Tank and Pump Company, Fort Wayne, Ind., a corporation of Indiana Application May 8, 1939, Serial No. 272,428

6 Claims. (01. 103126) i This invention relates to pump constructions, and particularly'to rotary pumps of the intermeshing gear type and to the method of producing the rotary gear members therein.

It is an object of the invention to produce an intermeshing gear rotary pump of improved construction and operating characteristics, including improved efiiciency, smoothness, and quietness of operation.

More specifically it is an object of the invention to produce a rotary gear pump having an improved manner of cooperation between the intermeshing gears wherein the teeth of the gears are brought into engagement as soon as possible and held in engagement as long as possible at the engaging position, thereby producing smooth and quiet operation of the gears and precluding play or backlash between them.

Another object of the invention is to produce a pair of cooperating gear members having the foregoing features of construction and. operation, particularly for use in a rotary gear pump.

A further object of the invention is to incorporate the foregoing features in a pump of the internal gear type including a toothed rotor gear, an idler gear disposed internally of the rotor teeth and in geared engagement therewith, and an intermediately disposed crescent member; and wherein the rotor teeth are substantially semicylindrical in form.

Still other objects, advantages and features of the invention will appear from the following specification when takenin connection with the accompanying drawings wherein a preferred embodiment of the invention is illustrated.

In the drawings wherein like reference numerals refer to like parts throughout:

Fig. 1 is a sectional view of a pump structure of the aforesaid internal gear type constructed in accordance with the principles ofthe invention;

Figs. 2 to 9 inclusive are partial detail views,

on an enlarged scale, illustrating the successive trated comprises a rotor member ll adapted to be driven from a shaft II and provided with a series of teeth I! annularly disposed and projectngparalleitotheaxlsoftheshaft ll,ina

- manner well understood in pump constructions of this type. The shaft II by which the rotor is adapted to be driven projects through-the rear side of the pump casing and is adapted to be connected to any suitable power source. An idler gear I3 is mounted on-a shaft I4 journalled in the front of the pump casing, and carries teeth i5 which cooperate with the rotor teeth I2. As will be seen the axes of shafts II and M are offset or eccentrically disposed. A crescent member I6 carried by the front of the pump casing is interposed between the rotor and idler gear, and engages the teeththereof at a position opposite to the point of intermeshing tooth engagement indicated by the reference'numeral ii. The ends ll! of the idler gear teeth are curved accurately to conform to the interior curved surface of the crescent member for sealing engagement therewith, and also conform in a general way to the curvature of the boss I9 formed on the pump casing. Similarly the rotor teeth l2 are provided with internally facing indentations 'or curved surfaces 20 accurately conforming to the curvature of the exterior side of the crescent member and adapted to be brought into sealing engagement with the crescent during the operation of the pump as shown in Fig. 1. The outwardly facing surfaces 2i of the rotor teeth are curved accurately to conform to the curvature of the casing boss l9 and to the curvature of the lower casing portion 22, for sealing engagement with these casing parts. The rotor teeth are generally semi-cylindrical in cross section as will more specifically appear hereinafter.

Inoperation, as tne pump rotor is driven in a clockwise direction from its driving shaft ll, fluid which may be liquid, such for example as gasoline, will be pumped from the inlet 23 to the outlet 24 in the manner illustrated by the arrows in Fig. 1, the liquid being carried in the pockets between the teeth of the rotor and idler gear. Liquid is prevented from leaking back from the.

outlet to the inlet side of the pump by reason of the inter-meshing ensuing of the gears as indicated at ii, and by the crescent member it which engages the rotor and idler gear teeth sealing the pockets therebetween. The idler gear receives its rotary motionby reason of its geared engagement with the rotor.

While the invention has been illustrated as applied to an internal gear pump of the foregolns ype, a pump to which it has particular applicability, it is to be understood that certain features vof the invention may be adapted for use with other types of structures having intermeshing gears, including other types of rotary gear pumps.

Referring to Figs. 2 to 9 inclusive illustrating the various positions which the idler gear teeth assume in their cooperation with therotor teeth, it will be seen that in Fig. 2 the idler gear tooth l6, while approaching the position of intermeshing engagement, has not as yet contacted either the leading rotor tooth l2a or the trailing rotor tooth lZb. As rotation takes place in a clockwise direction, as indicated by the arrow in Fig. 2, the idler gear tooth first engages the trailing tooth lib of the rotor, as shown in Fig. 3. As rotation continues, the idler gear tooth next engages the leading tooth I2a oi the rotor, maintaining its contact with the trailing rotor tooth l2b, as shown in Fig. 4. In Fig. 5 the idler tooth has reached its fully meshed position, corresponding to the position il shown in Fig. 1, in

which position it remains in engagement with both of the rotor teeth. In Fig. 6 the idler tooth bodiment, the rotor and idler having 9 and 7 teeth respectively, the speed ratio of the rotor and idler will be 7 to 9, and accordingly the ratio of the pitch circles radii will be 9 to '7. In other words the radii of the pitch circles of the rotor and idler, represented by the linesX and Y respectively in Fig. 10 bear the ratio of 9 to 7, and for any given eccentricity 0Q, the values of the radii and resultingly the size of the gears may be determined, or for any given relative gear sizes the required eccentricity may be calculated.

As previously stated, the rotor teeth are semicyiindrical in contour, the radius of the tooth cylinder being represented by the line H. in Fig. 10; and in order to insure an acute angle for the corner oi the tooth preventing the formation of reverse curvature, the center C from which the radius R. is swung is located somewhat beyond or externally of the exterior surface 2| oi the tooth. Preferably the trough portions 26 oi the idler gear teeth are also semi-cylindrical has passed the position of full mesh, but it still maintains its contact both with the leading 'rotor tooth lid and the trailing rotor tooth l2b.

In Fig. 'l the idler tooth has left its contact with the trailing tooth lib, but still maintains its contact with the leading rotor tooth Ila. In Fig. 8 the contact between 'the end of the idler gear toothand the leading rotor tooth lie is still maintained, and in Fig. 9 the posithe outer side portions thereof which shaping and its method of production constitute a principal feature of the invention as will now be described with reference to P18. 10.

Assuming that it is desired to construct a pump wherein the rotor will have 9 teeth and the idler gear 7 teeth, as shown for example in Fig. 1, it is well known'in the art of gearing that every gear has a so-called pitch circle, and in the case of two intermeshing gears the pitch circles are tangent at the point of mesh: and knowing the gear or speed ratio which the gears are to have, the ratio or the radii oi the pitch 7 circles or the size of the gears canbe determined.

In Fig. 10 a rotor tooth l2 and an idler gear tooth II are shown in contact, on a further enlarged scale, the rotor tooth being disposed at the full position of mesh il (Fig. 1) as distinguished from the position of the gears shown in Fig. 1 wherein the idler gear tooth is shown in the hill position of mesh. The axis of the idler is indicated at O, and the axis of the rotor at Q in Fig. 10. the eccentricity of the gears corresponding to the eccentricity of the shafts ii and il, therefore being represented by the distsnce 0Q. The. pitch circle for the idler gear is represented by the line I and the pitch circle for the rotor by the line H, the two pitch circles being in tsngency and in contact at the point E, the position of mesh. As is known, in the case in shape. being illustrated as formed with the radius J in Fig. 10. To provide a clearance space 21 between the rotor tooth and the trough of the idler teeth, the center D from which the radius J is swung is located somewhat inwardly or'the center C, and to provide contact between the rotor tooth and the idler tooth at a point such as indicated at A the radius J is made slightly smaller than the radius R. The width oi the rotor teeth with respect to the width of the idler teeth will be determined by the size of the radius R, and these values are selected so that the size of the teeth will be substantially as shown in Fig. 1. the rotor teeth which have considerable unsupported axial length being appreciably wider than the idler teeth to impart strength thereto.

The idler gear tooth is reversely curved from the point A to the point B where the side wall of the tooth and the outer surface l8 thereoi Join. It is this surface AB which insures the maintained contact between the idler and rotor teeth. in the manner previously described, and its method of formation constitutes a principal feature of the invention.

To form the surface AB the rotor may be considered as rolling around the idler while it is held stationary, the pitch circles of the gears rolling in contact as they do in actual operation; and the rotor tooth may be considered in the nature of a grinding or cutting wheel as indicated by of intermeshing gears the gear or speed ratio th broken line U, the rotor tooth thus grinding or cutting the surface AB on the idler tooth to the precise shape that it should have to Just maintain contact with the rotor tooth during the actual operation of the gears.

Assume any point such as K on the pitch circle H of the rotor. Locate another point Kl on the pitch circle F of the idler so that the length of the line Him is equal to the length of the line EK. As the rotor is rolled around the stationary idler gear by means of the pitch circles, the point K will move down and coincide with the point Ki when the rolling operation has progressed to the K-Ki position to bring the pitch circles into tangsncy at this point. As will be seen by reference to Fig. 1.0 the point oi tangency E and the centers 0 and Q are in a straight line when the gears are in the original position illustrated. Similarly when the point of tangeney has prograssed to the point Ki, this. new point of tangency. the idler center 0, and the new center Qi for the rotor will be in-a straight line. Accordingly to find a new center Qi for the rotor is straight line may be drawn through the points K1 and O to the intersection of the arc M drawn about the center with the radius 0Q.

To find the position which the rotor tooth I! will occupy with respect to the idler gear tooth l5 when the point of tangency between the gears has progressed to the position K1 arcs may be swung to determine the point 01in such manner that the line C1, K1 is equal in length to the line CK, and the line C1Q1 is equal to the line CQ. The. two triangles CKQ and C1K1Q1 are equal,

and they represent different positions assumed by'the same parts of the rotor as it is rolled on the pitch circle of the idler gear to move the point of tangency between the gear pitch circles from the point E to the point K1. The point C1 accordingly indicates the position which the center of the rotor tooth 12 will assume with respect to the idler tooth l5 when the point of mesh has progressed to the point K1, and if the radius R1 equal to the radius R is swung from the center C1 an arc T1 is found which determines the point of contact between the rotor and idler teeth when the point of tangency has progressed to the point K1, and finds the curvature which the surfaces AB must have at such point to maintain contact with the rotor tooth.

To determine additional points for the surface AB, additional points such as P and P1 are laid out on the pitch circles H and F so that the length of the line EP equals the line EP1. When the rolling of the rotor about the idler Pitch circle has progressed to bring the point P into position to coincide with the point P1, new positions Q2 for the rotor center and C: for the center of the rotor tooth may be found in the manner previously described. The same process may be followed to find the additional rotor tooth centers C304 etc., and by swinging the radii RzRs and R; from these centers arcs 'I2T3T4 are found which determine the sequential points of contact between the rotor and idler teeth and accordingly determine the proper curvature for the surface AB. Obviously the process may be repeated sufiiciently to accurately determine the entire length of the surface AB, but on the drawings in the interest of simplification only a few illustrative examples have been shown. Considering the rotor tooth as a grinding or cutting wheel, as it moves successively to the centers C1, Ca, Ca, and C4 the surfaces AB will be accurately shaped.

In accordance with the foregoing method the surface AB on the outer end of the idler gear tooth is in effect cut or shaped by the rotor tooth itself, the rotor tooth being moved with respect to the idler tooth in the actual manner in which motion takes place when the gears are in operation. The surfaces AB which will be similarly formed on the two sides of each of the idler teeth, are accordingly accurately shaped so that they continuously maintain contact between the rotor and idler gear teeth from the point of initial engagement, such for example as illustrated in Figure 3 to the point of final engagement such as is shown in Fig. 8. Improved efliciency,

smoothness and quietness of operation is obtained.

It is obvious that various changes may be made in the specific embodiment of the invention heretofore described and in the several method steps set forth without departing from the spirit of the invention. Accordingly the invention is nt to be limited beyond the limita tions set forth in the following claims.

The invention is hereby claimed as follows:

1. A rotary pump of the internal gear type comprising a rotor, and a mating gear engageable therewith, the rotor teeth being provided with convex cylindrical surfaces and the mating gear being provided with concave cylindrical tooth surfaces cooperable with the cylindrical tooth surfaces of the-rotor, the center of curva-' ture of the cylindrical tooth surfaces of the mating gear being radially inwardly displaced from the center of curvature of the cylindrical tooth surfaces of the rotor at the point of meshing engagement.

2. A rotary pump of the internal gear type comprising a rotor, and a mating gear engageable therewith, the rotor teeth being provided with convex cylindrical surfaces and the mating gear being provided with concave cylindrical tooth surfaces cooperable with the cylindrical tooth surfaces of the rotor, the radius of curvature of the mating gear cylindrical tooth surfaces being less than the radius of curvatureof the cylindrical rotor tooth surfaces, and the center of curvature of the cylindrical tooth surfaces of the mating gear being radially inwardly displaced from the center of curvature of the cylindrical tooth surfaces of the rotor at'the point of meshing engagement 3. A rotary pump of the internal gear type comprising a rotor having circumferentially discontinuous teeth, and a mating gear engageable therewith, the rotor teeth being provided with convex cylindrical surfaces and the mating gear being provided with concave tooth surfaces coop-' erable therewith, the center of curvature of said convex cylindrical rotor tooth surfaces being disposed radially outwardly from the outer edges of the rotor teeth.

4. A'rotary pump as defined in claim 3 wherein said concave mating gear tooth surfaces are cylindrically shaped.

5. A rotary pump as defined in claim 3 wherein said concave mating gear tooth surfaces are cylindrically shaped, and wherein the radius of curvature of the mating gear cylindrical tooth surfaces is less than the radius of curvature of the cylindrical rotor tooth surfaces.

6. A rotary pump as defined in claim 3 wherein said concave mating gear tooth surfaces are cylindrically shaped, and wherein the center of curvature of the cylindrical tooth surfaces of the mating gear is radially inwardly displaced from the center of curvature of the cylindrical tooth

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