US2986097A - Gear pump or motor device - Google Patents

Description

2 Sheets-Sheet 1 GEAR PUMP 0R MOTOR DEVICE R. S. CHRZANOWSKI EI'AL III IIII" VHL May 30, 1961 Filed Jan. 7, 1959 May 30, 1961 R. s. CHRZANOWSKI EIAL GEAR PUMP OR MOTOR DEVICE 2 Sheets-Sheet 2 Filed Jan. 7, 1959 United States Patent GE'AR PUMP OR MOTOR DEVICE Richard S. Chrzanowski and WilliamB. Walker, Rockford, I1l., assignors to Sundstrand Corporation, a corporation of Illinois Filed Jan. 7, 1959, Ser. No. 785,360

2 'Claims. or. 103-126) This invention relates to a gear type pump or motor device and has for a general object the provision of a new and improved device of this type.

A more specific object is to provide a new and improved, gear type pump-or motor device having improved efliciency due to reduction in leakage across the meshing gear teeth, that is, at the sides of the gears, between the gears and the housing, at the point where only one tooth separates the lower pressure and high pressure sides of the device.

Another object is to provide a new and improved gear pump including bolt means extending through the inlet and outlet closely adjacent the point-of meshing gear teeth for drawing the pump cover plates together to prevent .bulging thereof and leakage of fluid past the sides of the gears on development of high pressures.

A further object is to provide a new .and improved device of the type described in the preceding paragraph including spacers on the bolts in the inlet and outlet to prevent drawing the cover plates too closely against the gears and binding the latter.

Other objects and advantages will become readily apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Fig. 1 is a side elevational view of a gear type pump or motor device constructed according to the principles of the present invention, showing inlet and outlet conduits in section;

Fig. 2 is asectional view taken-at about the line 22 of Fig. 1;

Fig. 3 is a sectional view taken at about the line.33 of Fig. 2; and, f

Fig. 4 is a sectional view taken along the line 4'4 of Fig. 1.

While an illustrative embodiment of the invention is shown in the drawings and will be describedin detail herein, the invention is susceptible of embodiment in many different forms, and it s houldbe understood that the present disclosure is to be considered as an exemplification of the principles ofthe invention and is not intended to limit the' invention to the embodiment .illustrated. The scope of the invention willvbe pointed out in the appended claims.

Referring now to the drawings in more detail, as illustrated, the invention is embodied in a gear pump including a housing formed of assembled parts including end caps or cover plates 11, and 12 and a spacer plate 13 positioned between the cover plates. The cover. plate 11 may be referred to as a mounting plate, asit'includes a pair of laterally extending ears :14 having suitable bores 15 to facilitate mounting of the pump as desired. The cover plate 12 may be referred to as 'a port plate as it includes an inlet port 17 and an outlet port. 18 both pass- 2,986,097 Patented May 30, 1961 ing completely through the plate and each adapted to receive suitable conduits as at 19 and 20.

When assembled, the cover plates and spacer plate are held together in the positions illustrated in the drawings by means of a series of bolts 22 arranged adjacent the outer perimeters of the plates each bolt including a head as at 22a and carrying a nut as at 22b.

Internally, when assembled as illustrated, the cover plates and spacer plate form a pumping chamber, .generally designated 25 (Fig. 3), including a pair of connecting part-circular cavities 25a and 25b each cavity adapted to receive one of a' pair of meshing spur gears -26 and 27 which form the pumping mechanism. As will be understood from the drawings, the width or thickness of'the spur gears 26 and 27 is substantially the same as the thickness of the spacer plate 13, so that the gears are housed completely within the spacer plate in cavities 25a and 25b which are closed at opposite sides by cover plates 11 and 12. Adjacent the left side of the pumping chamber as viewed in Fig. 3, an inlet chamber 29 leads into the pumping chamber from its communication with the inlet port '17 in the port plate 12. Simi- ,in the spacer plate at opposite sides of the point at which gears 26 and 27 are in mesh.

As best seen in Fig. 4, the pump gears as and 27 are mounted respectively on an idler shaft 32 and a drive shaft 33, both shafts having opposite end portions rotatably supported in the cover plates 11 and 12 as by means of suitable bearings illustrated at 35. One of the shafts extends outwardly of the pump housing as seen at 33a and provides a means by which the device may be driven when operated as a-pump or a means by which the device may drive when operated as a motor. Bearings 35 are mounted in suitable recesses as at 36a, 36b, 36c,

and 36d, the first three of which are closed by seals including a disk 37 supporting an O-ring seal 38, both retained in the recess by a snap ring 39.

In operation, when the device is utilized as a pump, with the gear 26 rotating in a clockwise direction and gear 27 in a counterclockwise direction, fluid will be drawn into the pumping chamber 25 through inlet conduit 19, inlet port 17, and inlet chamber 29, dividing in the inlet chamber and passing with the rotating gears in a clockwise direction in cavity 25a and in a counterclockwise direction in cavity 25b to the position where the gear teeth begin to mesh, in the vicinity of outlet chamber 30 where the fluid is forced from between the gear teeth outwardly into outlet chamber 30 from whence it passes through outlet port 18 to the conduit 26. This will be understood as a conventional mode of operation for gear pumps. When the device is utilized as a motor, .it will be understood that the operation will dilfer from that described.

In gear pumps of the type described, most internalleakage occurs past the sides of the gears adjacent the point where the gears mesh andwhere only a single tooth separates the high pressure and low pressure sides of the device. Such leakage passes between the sides of thegears and plates such as cover plates 11 and 12. 'The clearance maintained between the sides'of the gears and the cover plates is a critical factor in maintaining efiiciency and for optimum performance, such clearance should' -be somewhat less than .001 inch. While such a clearance may readily be established in constructing the pump, and

in operating at relatively low pressures, as the pressure builds up the cover plates bulge outwardly thereby increasing the clearance between the sides of the gears and the cover plates. The greatest deflection of the cover plates is near their centers, and this coincides with the point of gear mesh where the tendency for leakage is greatest. Unless compensated for, these two effects cause a serious decay in volumetric efficiency at pressures excceding 1500 p.s.i.

In the past, the disadvantages referred to above have in some instances been compensated for by the use of floating pressure plates biased inwardly against opposite sides of the gears by fluid from the high pressure side of the device. This works effectively in a pump but when the device is used as a moto'r, the high inlet pressure frequently operates to clamp the floating pressure plates against the gears before the gears start rotating and thereby prevents starting.

In the construction illustrated herein, applicants have compensated for the above described disadvantages in a different fashion. More particularly, in order to prevent bulging of the cover plates on development on high prasures, the present invention contemplates the use of bolts as at 40 and 41, located respectively in the inlet chamber and the outlet chamber, closely adjacent, as close as possible, the point of gear mesh, each bolt being anchored at opposite ends respectively in the cover plates 11 and 12 so as to be capable of drawing the plates toward each other to thereby prevent their bulging beyond the predetermined desired maximum spacing. To this end, as best seen in Fig. 2, the port plate 12 is formed with a pair of ledges 42 and 43, one located in each of the inlet and outlet ports 17 and 18, and each suitably bored to receive one of the bolts. Each bolt is screw threaded and has its opposite end receivable in a suitably tapped bore in the mounting plate 11. It will be understood that the positioning of bolts 40 and 41 as illustrated will serve to provide means lo'cated as near as possible to the point of greatest bulging to prevent an increase in spacing between the plates and the sides of the gears to thereby prevent leakage from the high pressure side of the device to the low pressure side of the device across the point of gear mesh, that is, at the sides of the gears, between the gears and the housing members 11 and 12.

In order to prevent excesssive tightening of the bolts 40 and 41 and a consequent drawing of the cover plates too closely and binding the gears to hinder their rotation, spacer means is provided to maintain a predetermined minimum separation between the cover plates. Preferably, each bolt passes through an incompressible spacer of predetermined length, as at 45 and 46, having opposite ends bearing against opposite cover plates. In the preferred embodiment illustrated, spacers 45 and 46 are formed integrally with spacer plate 13, and take the form of sleeves or bosses at the end of weblike projections 47 and 48 extending inwardly toward the point of gear mesh respectively in the inlet chamber 29 and the outlet chamber 30. The spacers are finished to a thickness equal the thickness of the spacer plate and act as washers or stops to maintain a predetermined minimum spacing be tween cover plates irrespective of the torque applied to the bolts. In addition to their primary function, the construction of the spacers integrally with the spacer plate lends rigidity to the assembled housing.

The suction operation at the inlet chamber is not adversely effected by the location of the bolt and spacers in this chamber, but on the other hand may possibly improve the filling of the spaces between gear teeth as the bolt and spacer tend to divide the flow into the chamber, directing the divided halves respectively towards the peripheries of the gears rather than towards the point of gear mesh.

Tests conducted on devices of the type described with and without bolts such as those illustrated at 42 and 41 indicate that these bolts provide a materially improved efliciency particularly in the pressure range above 1200 Plotting of the above values of pressure as abscissa vs. efiiciency as ordinate will indicate that without the bolts, at pressures above 1500 p.s.i., the volumetric etficiency drops oif in a rapidly falling curve while with the bolts, the efficiency at pressures above 1500 p.s.i. remains on a straight line curve substantially as at pressures below 1500 p.s.i.

The device illustrated herein and others like it have been constructed for and are intended primarily for use as pumps, but they have also been tested as motors with no internal changes and are found to be equally suited for either type of operation. While the preferred embodiment chosen for illustration includes inlet and outlet ports in one of the cover plates, it should be understood that alternatively these ports may be formed in the spacer plate if desired.

We claim:

1. In a gear type pump or motor device having a first cover plate, a spacer plate, and a second cover plate assembled together, said spacer plate having a recess therein defining a pumping chamber, a pair of rotatable gears in the pumping chamber, said spacer plate having additional recesses therein defining an inlet chamber on one side of and radially spaced from the pumping chamber and an outlet chamber on the other side of and radially spaced from said pumping chamber, an inlet port opening axially into the inlet chamber and an outlet port connected to the outlet chamber, in combination therewith, means for preventing bulging of the cover plates on pressure increase comprising a pair of bolts passing through the spacer plate on opposite sides of the point of gear mesh and substantially as closely adjacent thereto as possible without interfering with the rotation of the gears, each bolt fixed at opposite ends respectively in the cover plates to hold the plates against relative outward movement on development of high pressures to thereby prevent leakage of liquid between the gears and the cover plates from the high pressure side of the device to the low pressure side of the device across the point of gear mesh, and a pair of spacers integral with said spacer plate and located in the inlet and outlet chambers respectively through which said bolts pass to maintain a predetermined minimum spacing between the cover plates and thereby prevent the bolts from drawing the plates too tightly against the gears, the chamber forming the inlet recess being tapered to direct incoming liquid flowing axially through said inlet port radially through the inlet chamber and toward the pumping chamber, said spacer in the inlet chamber serving to divide the radially flowing liquid into two streams each directed toward a different one of the gears and moving in the direction of rotation of the gears.

2. In a gear type pump or motor device having a first cover plate, a spacer plate, and a second cover plate assembled together, said spacer plate having recesses therein defining a pumping chamber, an inlet chamber and an outlet chamber, and a pair of rotatable gears in the pumping chamber and meshing at a point between the inlet and the outlet chambers, in combination therewith, means for preventing bulging of the cover plates on pressure increases comprising, a pair of bolts passing through the spacer plate on opposite sides of the point of gear mesh and substantially as closely adjacent thereto as possible without interfering with gear rotation, each fixed at opposite ends respectively in the cover plates to hold the plates against relative outward movement on development of high pressures to thereby prevent leakage of fluid between the gears and the cover plates from the high pressure side of the device to the low pressure side of the device across the point of gear mesh, and, a pair of spacers integral with said spacer plate and extending through the inlet and outlet chambers respectively, through which said bolts pass to maintain a predetermined minimum spacing between cover plates and thereby prevent the bolts drawing the plates too tightly against the gears, said spacer in the inlet chamber having radially directed flow guiding means to divide the flow of incoming liquid into two streams each directed generally tangentially toward a diiferent one of said gears and moving in the direction of rotation of the gears.

References Cited in the file of this patent UNITED STATES PATENTS 237,764 Medden Feb. 15, 1881 237,988 Medden Feb. 22, 1881 1,129,091 Hawley Feb. 23, 1915 1,870,192 Butler Aug. 2, 1932 1,940,410 Fitch et al. Dec. 19, 1933 2,233,709 Osborne Mar. 4, 1941 2,263,548 Mueller et al. Nov. 18, 1941 2,498,911 Chittenden Feb. 28, .1950 2,655,108 Osborne Oct. 13, 1953 2,880,678 Hofler Apr. 7, 1959

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