US3433168A - Gear pump with takeup for wear - Google Patents

Description

March 18, 1969 o. H. BANKER 3,433,168

GEAR PUMP WITH TAKEUP FOR WEAR Filed Jan. 13, 1967 iiiai-i k-i- INVENTOR. OSCAR H. BANKER BY m fla mw,

ATTORNEYS United States Patent 3,433,168 GEAR PUMP WITH TAKEUP FOR WEAR Oscar H. Banker, Bay Village, Ohio, assignor to Meyer Products, Inc., Cleveland, Ohio, a corporation of Ohio Filed Jan. 13, 1967, Ser. No. 609,060 US. Cl. 103-126 6 Claims Int. Cl. F04c 1/04; F 04b 21/08 ABSTRACT OF THE DISCLOSURE A gear-type pump includes a shiftable shroud member for radially sealing against the peripheries of the gears. The shroud is shifted under influence of pressure exerted against the shroud at the outlet port of the pump. The shroud is shifted into engagement with the gears adjacent the inlet port of the pump. The shroud is releasably locked in position sealingly engaged with the gears. When the shroud becomes worn so that the radial seal is ineffective, the locking means may be released to allow the shroud to shift once again into proper sealing engagement with the gears. The shroud is symmetrical on opposite sides of a line connecting the rotational axes of the two gears so that it may be reversed when one side becomes worn. The releasable locking means for retaining the shroud against further shifting movement may comprise the same clamping means for holding the pump housing parts together.

This invention relates to gear pumps and, particularly, to such pumps having means for taking up for wear of certain of its parts to regain Original efi'iciency.

Gear pumps as usually constructed comprise a housing having cavities for driving and driven meshing gears, an inlet port at one side of the meshing teeth of the gears, and an outlet port on the opposite side of the meshing teeth. Appropriate means are provided for effectively sealing the outlet port from the inlet port in the housing, the means comprising a close-fitting wall on the gear cavities to seal the peripheries of the gear teeth, and side plates for sealing the sides of the gears. In one form which has been proposed for relatively low pressures, fluid pressure responsive deformable means are used to effect the seal at the periphery of the gear teeth, and the same type of seal may be used at the sides of the gears. The latter form, however, is not recommended for high fluid pressures because of the high friction developed between the gears and deformable member which increases wear and decreases efficiency.

Thus, high pressure gear pumps are presently made of metal parts which must be closely machined to provide the necessary seal between the input and output parts of the pump. Such close machining encompasses all surfaces in the interior of the pump and, particularly, the confronting surfaces of the gear cavity and the gears in the cavity. The requirement for close machining results in a high cost for high pressure gear pumps. Furthermore, as the confronting surfaces wear, the efiiciency of the pump decreases and cannot be restored without replacing the worn parts.

The principal object of this invention is the provision of a gear pump in which only the gear width and the width of a gear cavity defining ring are machined, all other interior surfaces of the parts of which are die cast, or produced by powdered metal molding techniques.

Another object of this invention is the provision of a gear pump, the original etficiency of which may be readily restored merely by changing the relationship of the parts thereof without disassembling the pump and without replacing any of the worn parts.

As a more specific object, this invention has within its 3,433,168 Patented Mar. 18, 1969 purview the provision of a gear pump in which a peripheral seal for the gears is effected by a ring encompassing the gears and drawn against the gear peripheries by the pressure of the outlet port, the ring being adjustably mounted in the pump housing so that its position relative to the gears can be adjusted from time to time.

These and other objects of this invention will become apparent from the following detailed description when taken together with the accompanying drawing in which:

FIGURE 1 is a cross section through a pump made in accordance with this invention;

FIGURE 2 is a side elevational view of the pump of FIGURE 1 with the cover removed and looking in the direction of arrows 2--2 in FIGURE 1;

FIGURE 3 is a section through the pump of FIGURE 1 taken along lines 33 of FIGURE 1;

FIGURE 4 is a fragmentary section of the housing taken along lines 44 of FIGURE 1;

FIGURE 5 is a fragmentary section through the housing of FIGURE 4 taken along lines 55 thereof, showing a side plate in place;

FIGURE 6 is a partial section through a side elevation of a modification of the pump of FIGURE 1; and,

FIGURE 7 is a front elevational view of the pump of FIGURE 6 with the cover thereof removed.

According to the present invention, the element of the pump forming the shroud for the gears in the gear cavity is separate from the housing and is loose and shiftable under fluid pressure developed by the pump to bear against the peripheries of the teeth of the pump gears and thereby form a seal therewith. Unlike other pressure responsive gear pump shrouds, the pressure on the gear teeth is limited by determining the relative positions of the gear teeth and shroud under relatively low pressure and then locking the shroud in place in the housing so that upon the development of much higher pressures within the pump the relative locations of the gears and their respective shrouds remain fixed.

When the gear teeth and/ or the shroud have become worn to the point where the efliciency of the pump is noticeably reduced, the shroud is then loosened, the pump is operated at a lower pressure again to bring the shroud against the gear teeth to form a seal, and the shroud is then locked in place as before during subsequent operation under the high pressures for which the pump is designed. When this adjusting procedure has been carried out so many times that no further adjustment is possible in the same manner, the pump is disassembled, the shroud is reversed so that the part which formerly formed the seal is now at the output end of the pump and the output end which is unused now becomes the input end at which the seal is again formed in the same manner.

Referring now to the drawings for a detailed description of the invention, the pump is comprised of a hous ing 10 which is preferably made as a die casting to reduce as much as possible machining costs. Thus, housing 10 is formed with openings 11 and 12 in which are pressed needle bearings 13 and 14, respectively, for the reception of a drive shaft 15 and an idler shaft 16. Drive shaft 15 extends outwardly to the left as viewed in FIGURE 1 beyond housing 10 for attachment to an appropriate drive for the pump. A cavity for a conventional lip seal 17 is provided for sealing the opening around shaft 15.

In the left hand side of housing 10 as viewed in FIG- URE 1 is die cast a circular cavity 18 which is shown in greater detail in FIGURE 4. Said cavity 18 has a peripheral recess 19 and is in communication with an inlet port 20 and an outlet port 21, also formed in the initial die casting operation. Outlet port 21 is smaller than inlet port 20 and has a counterbore 22 therearound to receive a ring of packing, such as an O ring 23 (FIGURE 5).

Shafts and 16 extend through cavity 18 and pump gears 24 and 25 are mounted on shafts 15 and 16, respectively, for rotation with their shafts. Said pump gears 24 and 25 are of such size as to have their teeth 27, 28 intermesh to provide the pumping action. Also in cavity 18 is disposed a shroud in the form of a ring 29 which has an outer circular periphery 30 the diameter of which is smaller than the diameter of the circular wall 31 of cavity 18 by an appreciable amount so that ring 29 is loose in cavity 18. In one illustrative embodiment the outer diameter of ring 29 was less than the diameter of wall 31 of the cavity by approximately 0.050, leaving a space of 0.025" between the ring 29 and cavity wall 31. The interior of ring 29 is formed with semi-circular cavities 32 and 33 which are connected together by rectangular notches 34 and 35. Rectangular notch 34 is disposed around inlet port and defines an inlet chamber 79 with gears 24, 25, and rectangular notch 35 is disposed around outlet port 21 and defines an outlet chamber 80 with said gears. Inlet chamber 79 is disposed on one side of the intermeshing teeth 27, 28 and outlet chamber 80 is disposed on the other side of said intermeshing teeth. With the direction of rotation of the gears as shown by the arrows thereon, and with appropriate shrouding of the gears by ring 29 the fluid being pumped is picked up in chamber 79, carried around by the gear teeth and then pressurized in chamber 80.

The diameter of the semi-circular cavities 32 and 33 is slightly greater than the outer diameter of their respective gears 24 and 25, to avoid interference with gears 24 and 25. Ring 29 may move along a horizontal diameter, as viewed in FIGURE 2, relative to the gears 24 and to the extent permitted by the clearance between the gears and their cavities. Such movement is also permitted by the difference in diameters between the circular cavity wall 31 and the outer periphery of the ring 29, but to a much larger degree. This freedom of movement of the ring relative to the gears will be made use of in a manner hereinafter to be described.

Ring 29 is symmetrical about a line passing through the centers of the circles forming the semi-circular walls of the cavities 32 and 33 for the gears 24 and 25, respectively. Thus, said ring may be installed in cavity 31 with notch at the left as viewed in FIGURE 3 instead of at the right as shown therein, so that if it is initially installed as shown with rectangular notch 34 at the left as shown in FIGURE 2, it may, after a period of use, be turned around so that said notch 34 is at the right as shown in FIGURE 2.

Ring 29 and gears 24, 25, particularly the teeth of the latter, are made by powdered metallurgy techniques to reduce the number of machining operations on their surfaces. The only surfaces which are machined are the flat sides of the gears and the sides of the ring 29, to provide a predetermined gear width and a predetermined width of the ring, the latter being slightly wider than the gears so that the gears will have lateral clearance therewith within which to function.

Stamped and coined side plates 36 and 37 are provided adjacent the sides of the ring 29. Side plate 36 has openings in it for shafts 15 and 16 and also for inlet port 20 and outlet port 21. Side plate 37 has openings only for shafts 15 and 16.

Cavity 18 is closed by a cover plate 38 which may likewise be a die casting. As such it is formed initially with openings 39 and 40 for bearings 41 and 42 into which the shafts 15 and 16, respectively, are inserted, and with a circular shoulder 43 which is adapted to fit into cavity 18 against side plate 37. An 0 ring 44 disposed in an appropriate peripheral recess 45 in the end of the cover plate provides a seal between side plate 37 and wall 31 of cavity 18. Shoulder 43 is longer in an axial direction than the axial length of wall 31 remaining after the side plates and gears are assembled in the cavity. This 7 leaves a clearance 46 between the cover plate and housing for take up for wear which, in one typical example, was approximately 0.040". Said cover plate 38 is securely fastened to housing 10 by four machine screws located at the corners of the housing.

Housing 10 is formed with inlet and outlet passages 48 and 49, respectively, and is provided with a pressure relief valve 50 of any well-known construction by which excess pressures in outlet passage 49 are relieved and fluid released through said valve is returned through said valve 50 to the inlet port 48. Said housing 10 also has molded passageways 51 and 52 by which leakage past the side plates 36 and 37 toward the shafts 15 and 16 may be drained off and returned to the inlet passage or port 20.

Under operating conditions, pump pressure in outlet chamber will produce a thrust upon notch 35 to urge ring 29 to the right, as viewed in FIGURE 2. If ring 29 is not restrained, it will move to the right in response to such pressure and cause the opposite sides of cavities 31, 33 to move against gears 24, 25 to provide a pressureresponsive seal. Variable restraint upon lateral movement of ring 29 is provided by screws 47 through cover plate 38 and side plate 37 so that the pressure on ring 29 may be made high enough to prevent leakage under low pres sure and yet allow ring 29 to be moved against gears 24 and 25 by such pressure.

For maximum efliciency, it is necessary that a good seal be had between the tips of the teeth of the gears 24, 25 and the semi-circular cavities 32 and 33 in the ring 29 to prevent leakage from the high pressure side of the pump to the low pressure side through said semi-circular cavities. This close fit is secured in the present pump by assembling the parts in the relations shown in FIGURES 1 and 2, but without tightening the screws 47 to the extent required to hold ring 29 against lateral movement under low pressure conditionsin outlet chamber 80. The pump is first run without any restriction in the outlet opening to make certain that all of the parts run freely. After it is determined that all the parts are properly as sembled and running without interference, the outlet port is restricted by any suitable valve means (not shown) until a pressure of about 200 pounds per square inch is developed therein. Since the screws 47 were not tightened to their maximum intended pressure, ring 29 is relatively free to shift in its cavity 18. With pressure in the outlet chamber 80 at 200 pounds per square inch and the pressure in the inlet notch 34 at atmospheric or slightly less, there will be a net effective pressure on ring 29 tending to push it toward the right, as viewed in FIGURE 2, until the semi-circular cavities 32 and 33 contact the tips of the teeth of the gears 24 and 25. At this point the maximum efliciency of the pump is reached and the screws 47 may then be tightened to their maximum intended pressure. This increases the pressure on the plates 36, 37 which, in turn, increases the pressure upon ring 29 to lock said ring in place in the cavity 18. With ring 29 locked in place, the pressures at the outlet port may then be increased to the maximum for which the pump is designed and this additional pressure now will not be transmitted through the ring 29 to the tips of the gear teeth so that no additional appreciable friction will be developed between the gear teeth and the cavities 32 and 33. Thus, the efiiciency, that is to say, the friction losses developed at this point will remain substantially the same for as long as there is contact between the cavities and the gear teeth.

As the pump is used, however, the gear teeth, as well as the cavities 32, 33 will become worn and the efficiency of the pump will gradually decrease. When the lowered etficiency is no longer tolerable, the pump may be restored to its original efiiciency by loosening screws 47, operating the pump again at a reduced outlet pressure of about 200 pounds per square inch, and allowing the loosened ring 29 to move to the right, as viewed in FIGURE 2, until the cavities 32, 33 again contact the peripheries of the teeth of gears 24 and 25. This will be detected by an increase in the efficiency of the pump. When this event occurs, screws 47 are again tightened to the maximum required under full operating pressure and the pump may again be operated as before until the efficiency drops "below an accepted value.

This restoration of the efficiency of the pump may be repeated until ring 29 contacts the right hand (FIGURE 2) side of the wall 31, indicating that it can no longer move to bring the cavities 32, 33 in contact with the peripheries of the teeth of the gears 24 and 25. When this occurs, the pump is disassembled by removing cover plate 38 and the side plate 37, and then ring 29 is removed and turned end for end so that notch 35 is now on the left, as viewed in FIGURE 2, and notch 34 is on the right. The side plates and cover plates are then reassembled and bolts 47 tightened sufliciently to allow a pressure of 200 pounds per square inch to be built up in the outlet opening. From this point on the adjustment is identical to that already described, using the opposite unworn sides of the cavities 32 and 33 to bear against the tips of the teeth of gears 24 and 25.

Although a pressure of 200 pounds per square inch has been mentioned above, it is understood that this may vary, the requirement being that suflicient pressure be built up to effect a side shift of ring 29.

The lining up of the screw holes in the cover and housing during assembly of the pump may be facilitated by the use of a dowel pin 53 which holds the cover plate against rotation relative to the housing.

The modification shown in FIGURES 6 and 7 is identical in principle to that shown in FIGURES 1 and 2, the difference residing in the fact that instead of using a cavity such as 18 and housing 10, the latter is made without a cavity and has instead, a fiat wall. An equivalent of the ring 29 is made to extend to the exterior of the housing, so that the net result is a sandwich, so to speak, of two housing portions separated by the equivalent of ring 29.

The housing of the FIGURE 6 form is shown at 54 and has inlet and outlet ports 55 and 56, respectively, formed therein. Said ports terminate in a flat face 57 against which a rectangular shroud or ring 58 bears. Said ring 58 has a flat surface 59 in contact with flat face 57 and is formed with a pair of opposed semi-circular cavities 60 and 61 connected by rectangular notches 62 and 63. Inlet opening 55 is disposed within notch 62 and outlet opening 56 is disposed within notch 63. A pair of gears 64, 65 is disposed within semi-circular cavities 60 and 61 and extend toward one another to provide interengaging teeth 66, 67 between the inlet and outlet openings 55 and 56, respectively.

The opposite face 68 of ring 57 is likewise fiat and bears against a similar flat surface 69 on a cover plate 70. Both housing 54 and cover plate 70 have bearings (not shown) to support driving shaft 71 which is suitably connected to gear 64 to drive said gear, and a driven shaft 72 on which gear 65 is mounted. Housing 54 and cover plate 70 are formed with substantially oval grooves 73, 74 in which are retained 0 rings for effecting a seal between ring 58 and housing 54 and cover plate 70.

The sides of ring 58, that is, flat face 59 and its opposite face 68 are ground to provide a predetermined thickness for ring 58, and the sides of the gears 64 and 65 are similarly ground to provide a predetermined slightly smaller thickness for said gears so that when ring 58 is clamped between housing 54 and cover plate 70, said gears will be free to rotate therebetween. Housing 59 and cover plate 70 are die cast and ring 58 and gears 64 and 65 are formed from powdered metal in a mold, so that the only machining required is that on the faces 59 and 68 of ring 58 and the faces of the gears 64 and 65 confronting faces 59 and 68.

The adjustment of ring 58 relative to gears 64 and 65 to provide maximum efficiency for the pump is made in the same manner as for the pump of FIGURES 1 and 2. However, instead of having a ring loose in a cavity, the ring 58 is loose on four machine screws 75 which pass through enlarged openings 76 in ring 58. Said ring 58 is also made symmetrical with respect to a line connecting the centers of the gears 64 and 65, so that the ring may be reversed and its face 68 made to contact face 57 on housing 54 and its face 59 made to contact face 69 on cover plate 70. Inasmuch as all of the bolts are loose in their openings 76, said ring 58 is free to move to the right, as viewed in FIGURE 5 in response to pressure created in the outlet opening 56.

Thus, to provide maximum efficiency in the pump of FIGURE 6, the machine screws 75 are first tightened to allow a pressure of approximately 200 pounds per square inch to be built up in outlet opening 56 'when drive shaft 71 is rotated. At this pressure, ring 58 will not be held tightly enough between housing 54 and cover plate 70 to prevent a shift of said ring 58 toward the right as viewed in FIGURE 7 and against gears 64, 65 to form a seal therebetween. When ring 58 has so shifted, as evidenced by the attainment of maximum efficiency in the pump, the machine screws are then tightened to the maximum permitted and the pump may thereafter be run at its maximum pressure. When the efliciency decreases to the point where it is no longer acceptable, the machine screws 75 are loosened, again only sufficiently to allow pressure of about 200 pounds per square inch to be built up in the outlet opening 56 which then shifts the ring 58 farther to the right as viewed in FIGURE 7 to restore contact between the cavities 60, 61 and the gears 64 and 65, respectively, whereupon the screws are tightened to their maximum pressure and the pump is again operated at its designed pressure.

When no further shift to the right is possible, by virtue of the fact that the screws 75 contact the edges of the openings 76, the pump is disassembled by removing cover plate 70, and ring 58 is then reversed, the cover plate 70 is replaced, and screws 75 are brought home sufliciently to permit a pressure of 200 pounds per square inch to initiate the adjusting procedure described above.

As in the FIGURES 1 and 2 form, the FIGURE 6 form is provided with dowel pins 77, 78 to facilitate the assembly of the pump. Said pins, however, are as loose in their openings as screws 75 are in their openings to avoid unnecessarily restricting movement of ring 58 toward gears 64, 65.

Referring again to FIGURE 2, a piston 26 is mounted in a cylinder 26a which is communicated with outlet port 21 by passage 26b, see FIGURE 3. In this manner, the piston applies a force against the gears at their meshing point in accordance with the outlet pressure to force side plate 36 into a tight sealing engagement with the gears. This enhances the seal at the meshing point during pump operation.

It is understood, of course, that in both forms the openings for the shaft bearings and for the dowel pins will be appropriately machined to provide the necessary accuracy in the size and alignment of such openings for the bearings and pins. Similarly, the threaded holes for the screws will also be appropriately machined to accept the threaded ends of the screws. All other surfaces are die-formed or molded, thus providing a low initial cost for the pump. Low maintenance cost and high operating efficiency are achieved by periodically adjusting the position of the shroud.

Having thus defined my invention, I claim:

1. A gear type pump including a pair of meshing gears rotatably mounted in a housing and shroud means surrounding said gears, said shroud means forming an inlet chamber on one side of said gears and an outlet chamber on the other side of said gears, said shroud means being shiftably mounted relative to said housing for movement into engagement with said gears adjacent said inlet chamher under influence of pressure force exerted on said 7 8 shroud means in said outlet chamber, and selective re- 6. A method of adjusting a pressure shiftable shroud leasable locking means for selectively and releasably lockin a gear pump comprising: ing said shroud means against movement. (a) operating the pump at a reduced outlet pressure 2. The pump of claim 1 wherein each of said gears to shift the shroud into a shifted position in engagehas a rotational axis and said shroud is formed symment with the gears due to the outlet pressure actmetrical on opposite sides of a line connecting said axes. 5 ing against the shroud, and

3. The pump of claim 1 wherein said housing is de- (b) locking said shroud in said shifted position against fined by first and second housing members and said lockfurther shifting movement. ing means comprises releasable clamping means for clamping said housing members together in squeezing engage- References Cited ment with said shroud means. UNITED STATES PATENTS 4. The pump of claim 3 wherein said housing members and said shroud have holes therein, said holes being aligned, and said clamping means includes a rigid member extending through said holes, said rigid member having a cross-sectional dimension parallel to the direction of shifting movement of said shroud means, at least said hole in said shroud means having a lateral dimension parallel to the direction of shifting movement of said shroud means which is substantially greater than said cross-sectional dimension.

367,374 8/1887 Deming.

689,251 12/ 1901 Unbehend. 1,118,533 11/1914 Crocker. 2,697,987 12/ 1954 Barclay. 2,993,450 7/ 1961 Weigert. 2,996,999 8/ 1961 Trautman. 3,055,307 9/1962 Thrap. 3,196,800 7/1965 Hofier. 3,208,393 10/ 1965 Kosch.

5. A gear type pump including a pair of meshing gears rotatably mounted on parallel axes in a housing and FOREIGN PATENTS shroud means surrounding said gears, said shroud means 1,165,531 6/1958 F n forming an inlet chamber on one side of said gears and an outlet chamber on the other side of said gears, said ROBERT WALKER P "nary Examine"- shroud means being shiftably mounted relative to said WILB U-R J OO L Assistant Examiner housing for movement into engagement with said gears adjacent said inlet chamber under influences of pressure US. Cl, XJR,

force exerted on said shroud means in said outlet cham- 103--216 her, said shroud means being formed symmetrical on opposite sides of a line connecting said gear axes.

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