US3597131A

US3597131A - Gear pump with travel limited tied wear block

Info

Publication number: US3597131A
Application number: US860667A
Authority: US
Inventors: John J Schofield; Charles W Grennan; Le Roy A Difford
Original assignee: Chandler Evans Inc
Current assignee: Colt Industries Operating Corp; Colt Industries Inc
Priority date: 1969-09-24
Filing date: 1969-09-24
Publication date: 1971-08-03
Anticipated expiration: 1988-08-03
Also published as: CA929417A; DE2038053A1

Abstract

A three-gear pump for pumping nonabrasive fluids having a center gear and two outer gears intermeshing with the center gear. Two pivotable and movable peripheral tooth-sealing members having respective arcuate wiping surfaces engage each of the outer gears and the center gear. The sealing members are positioned adjacent the outlets of the pump. The sealing members are capable of only limited movement toward the gears due to respective stop elements integral with the pump housing and respective contact elements integral with the sealing members adapted to engage the stop elements. The sealing members are also pivotable about an axis transverse to the axes of rotation of the gears. As the sealing members wear due to contact with the gear teeth, the contact elements will respectively advance toward the stop elements until they contact one another to transmit the load on the sealing members to the housing.

Description

United States Patent Inventors John J. Schotield Glastonbury; Charles W. Grennan, Newington; Le Roy A. Dil'l'ord, Simsbury, all 01', Conn. Appl. No. 860,667 Filed Sept. 24, 1969 Patented Aug. 3, 1971 Assignee Chandler Evans Inc.

West Hartford, Conn.

GEAR PUMP WITH TRAVEL LIMITED TIED WEAR BLOCK 7 Claims, 5 Drawing Figs.

US. Cl 418/126, 418/ 135 Int. Cl F0lc 19/02, FOlc 19/08 Fieldoisearch 418/126, 135; 91/80, 87; 123/12 References Cited UNlTED STATES PATENTS 2,622,534 12/1952 Johnson 418/126 Primary Examiner-Carlton R. Croyle Assistant Examiner-Wilbur J. Goodlin Attorney-Radford W. Luther ABSTRACT: A three-gear pump for pumping nonabrasive fluids having a center gear and two outer gears intermeshing with the center gear Two pivotable and movable peripheral tooth-sealing members having respective arcuate wiping surfaces engage each of the outer gears and the center gear. The sealing members are positioned adjacent the outlets of the pump. The sealing members are capable of only limited movement toward the gears due to respective stop elements integral with the pump housing and respective contact elements integral with the sealing members adapted to engage the stop elements. The sealing members are also pivotable about an axis transverse to the axes of rotation of the gears. As the sealing members wear due to contact with the gear teeth, the contact elements will respectively advance toward the stop elements until they contact one another to transmit the load on the sealing members to the housing.

Patented Aug. 3, 1971 3,597,131

2 Sheets-Sheet 1 GEAR PUMP WITH TRAVEL LHVIITED TED WEAR BLOCK BACKGROUND OF THE INVENTION This invention pertains to gear pumps and also to gear pumps utilized to pump a nonabrasive fluid. This invention further pertains to gear pumps which incorporate a peripheral sealing member. More particularly, this invention pertains to gear pumps which incorporate a one-piece peripheral sealing member.

One-piece cantilevered wear block designs previously considered for high-speed pumps have been found not to be practicable because of the relative deflection of the wiping faces due to pressure tending to separate the wear faces and because of the excessive weight and manufacturing cost of refractory wear resistant parts.

Prior art pumps have embodied either cantilevered onepiece sealing wear blocks or independently pivoted blocks. In prior art pumps featuring sideplates, no attempt has been made to provide block articulation about an axis transverse to the axes of gear rotation. Also, no effort has been made in the prior art to limit the ability of the sealing member to follow the gear.

Certain gear pumps embody wear blocks positioned between a fixed sideplate and a movable sideplate; the movable being urged into contact with the wear block. It is desirable to have the lateral surface of the wear block adjacent the fixed sideplate in firm contact with the fixed sideplate so that movement of the wear block toward the gear is guided by this contact between these surfaces. A problem arises when the asymmetrical forces are exerted such that a loss of guiding contact between the fixed sideplate and the wear block is occasioned which could result in diminishment of the volumetric efiiciency of the pump and undesirable stress concentrations. It has been found that in high-speed pumps while refractory wear blocks yield satisfactory performance in many applications, they add weight and manufacturing cost to a pump in which they are incorporated and are prone to fail under repeated stresses as refractory materials have poor fatigue qualities. If the wear blocks are made of a soft metal and are not limited in travel, the service life of the pump will be impaired as prohibitive wear will result from extended use.

SUMMARY OF THE INVENTION The instant invention concerns a pump adapted to handle a nonabrasive fluid. A wear block, according to the invention, is made of a relatively soft metal, such as a bronze alloy, and the wiping faces thereof are joined by a tensile member to give added rigidity to the wear block. The wear block is mounted for limited movement relative to the gears such that the wear upon the blocks is limited to break-in wear. The wear block is also mounted for pivoting movement about an axis transverse to the axes of rotation of the gears to provide accurate guiding of the wear block against the fixed sideplate. A wear block according to the invention is unique in that its travel toward the gears is limited and also in that it is mounted for rotation about an axis transverse to the axes of rotation of the gears. The aforementioned construction enables a pump made in accordance with the invention to incorporate wear blocks made of a relatively soft metal and yet have a relatively long service life. A pump according to the invention also permits accurate guiding of the wear block irrespective of the lateral forces exerted thereon.

The problem of bending associated with cantilevered sealing elements is overcome by utilizing a tensile member to connect the cantilevered sealing elements. Since the instant device was not conceived for use with abrasive contaminants, significant journal wear is not anticipated. Hence, further ability of the wear block to firmly engage the periphery of the gear after break-in is not considered necessary.

Accordingly, it is an object of the present invention to provide a gear pump having wear blocks which are made ofa relatively soft metal and capable of a limited movement toward the gears.

Another object of this invention is to provide a gear pump incorporating a wear block wherein the wear block is pivotably mounted about an axis transverse to the axes of rotation of the gears.

A further object of this invention is to provide a gear pump incorporating wear blocks made of a relatively soft metal wherein the pump has a relatively long service life.

A still further object is to provide a pump having reduced inlet pressure requirements.

Yet a still further object is to provide a pump which does not mandate expensive overhauls.

Many other advantages and features of the invention will become manifest to those well versed in the art upon making reference to the detailed description which follows and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross section of the three-gear pump having a pivotable movable peripheral sealing assembly positioned adjacent each pump outlet.

FIG. 2 is a partial sectional view along the line 2-2.

FIG. 3 is a partial sectional view along the line 3-3.

FIG. 4 is a sectional view along the line 4-4.

FIG. 5 is a schematic cross section of another three-gear pump having a pivotable movable peripheral sealing assembly positioned adjacent each pump outlet.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings and generally to all of the forms shown in the following description, like parts are designated throughout by like numerals.

Referring to the example shown in FIGS. 1, 2, 3 and 4, there is provided a pump having a housing 1 defining therein a cavity 2 and comprising a pair of

end plates

3 and 4 positioned on opposite sides of housing I and secured in fluidtight relation to said housing by a plurality of bolts (not shown). Rotatably mounted about axes of

rotation

5, 6 and 7 in cavity 2 in housing 1 are three

gears

8, 9 and 10, the center gear 9 intermeshing with the two

outer gears

8 and 10 and engaging said outer gears at an area of intermesh indicated generally at 11 and 12. Shaft 13 is rigidly secured to gear 9 by means well known in the art. Shaft 13 drives gear 9 through a source of motive power (not shown) secured to shaft 13. Shaft 14 is secured to gear 8 and shaft 15 is secured to gear 10 such that shaft 14 and gear 8 and shaft 15 and gear 10 respectively rotate in unison responsive to rotative movement of driver gear 9.

Shafts

13, 14 and 15 are journaled in bearings (not shown) by means well known in the art with a close running fit such that axes of

rotation

5, 6 and 7 are maintained substantially parallel. Gears 8 and 9 are disposed in cavity 2 such that an inlet 16 is formed on one side of intermesh 11, and an outlet 17 is formed on the opposite side of intermesh 11. Similarly, gears 9 and 10 are disposed in cavity 2 such that an inlet 18 is formed on one side of intermesh l2, and an outlet 19 is formed on the opposite side of intermesh 12. The center gear 9 and the

outer gears

8 and 10 intermeshing therewith are so arranged that they comprise rotary fluid displacement means that will operate to move the fluid medium acted upon by the center gear and the two outer gears interrneshing therewith from the inlet 16 to the outlet 17 and the inlet 18 to the outlet 19 simultaneously. It is to be understood that inlets l6 and 18 and outlets 17 and 19 can be so interconnected as to provide a single inlet supply conduit to the separate inlets 1.6 and 18 and similarly manifold outlets 17 and 19 to provide a single outlet conduit.

As is clearly indicated in FIG. 1, the outer diameter of the

gears

8, 9 and 10 at the tips or periphery of the gear teeth are disposed in relation to the peripheral wall of cavity 2 adjacent each pump outlet so that there is a pronounced clearance between the periphery of each of the gear teeth and adjacent the cavity wall. This clearance is provided to reduce the possibility of cavitation at the pump inlet when the pump is operated at high speed. In order to provide peripheral tooth sealing adjacent the pump outlets 17 and 19, there are provided in accordance with the teachings of this invention novel movable peripheral tooth-sealing members or

wear blocks

20 and 21 engaging the periphery of each outer gear and the center gear respectively adjacent each pump outlet. In this particular embodiment the movable sealing members takes the form of first and second

movable sealing elements

22 and 23 respectively positioned on opposite sides of outlet 17, and

movable sealing elements

24 and 25 positioned on opposite sides of outlet 19. The

sealing elements

22, 23, 24 and 25 have arcuate wiping surfaces which substantially engage at least two teeth in the peripheral gear areas respectively designated 34, 35, 45 and 46. Before the pump is broken in the peripheral engagement of

sealing elements

22 and 23 with gears 8 and 9 is continuously urged by

springs

36, 37, 38 and 39 received by

mating depressions

40, 41, 42 and 43 respectively of sealing spacer 44. Similarly,

peripheral sealing elements

24 and 25 are continuously urged into peripheral sealing engagement with at least two teeth in he areas 45 and 46 of gears 8 and 9 respectively by springs 47, 48, 49 and 50 received by depressions 51, 52, 53 and 54 respectively of sealing spacer 55. Discharge pressure is communicated from discharge chamber 56 via interconnecting passageway 57 to variable volume chamber 58 to provide a discharge pressure responsive force supplemental to that provided by

springs

36, 37, 38 and 39. Similarly, discharge pressure is communicated from discharge chamber 59 via interconnecting passageway 60 to variable chamber 61 to to provide a discharge pressure responsive force supplemental to that provided by springs 47, 48, 49 and 50. Said pressure responsive and spring forces are combined to generate a single force on each sealing member.

The detailed construction of the peripheral tooth-sealing

members

20 and 21 is shown in FIGS. 1 to 4. Referring to FIGS. 1 and 2, sealing

elements

22 and 23 are structurally interconnected by

struts

26 and 27, between their inner surfaces, the struts bearing a tensile load induced by discharge pressure acting on the inner surfaces. Sealing member 20 comprises two

channel members

62 and 63 which are fixedly secured thereto and serve as contact elements to restrict travel of the sealing member toward gears 8 and 9 as will be more fully explained hereinafter. Contact

elements

62 and 63 respectively abut stop elements 64 and 65 as illustrated in FIGS. 1 and 4 after the pump has been broken in. Step element 64 is secured to housing 1 and is integral therewith. Stop element 64 comprises a base segment 66 having pivot in the form of a fulcrum 67 which is supported by L-shaped legs 68 and 69, the extremities of which are inserted into bores 70 and 71 respectively located in the sides of the housing. As a study of FIGS. 1 and 4 reveals, the sealing member cannot possibly advance past the position in which fulcrum 67 contacts contact member 62. This position represents a second or final position of the sealing member. Sealing member 20 is made of a relatively soft metal, such as an aluminum bronze alloy, and is designed such that a small space (of the order of 0.02 inch) exists between fulcrum 67 contact element 62 when the arcuate wiping faces of sealing

elements

22 and 23 are in firm contact with the teeth of gears 8 and 9 respectively. Thus a first position of sealing member 20 is defined when its wiping surfaces firmly contact their respective gears, that is, before the wiping faces have sustained wear sufficient to cause the fulcmm 67 to engage contact member 62. During the break-in period, sealing

elements

22 and 23 of sealing member 20 will undergo wear due to the friction between the wiping surfaces thereof and the respective gears and thus the sealing member 20 will advance from its first position toward its second or final position as wear progressively increases. When the

contact elements

62 and 63 and stop elements 64 and 65 respectively establish firm contact in the second position, illustrated in the drawings, the load transmitted to the sealing member by

springs

36 and 37, 42 and 43 and the pressure in chamber 58 will be transmitted to the housing 1 by

contact elements

62 and 63 and stop elements 64 and 65. In this second position the sealing member will not be in firm engagement with the gears, as was the case before it reached its second position, but the wiping surfaces and gears are nevertheless in substantial engagement. As it is not envisioned that a pump according to the invention will handle fuel containing abrasive elements, further wear should not be a problem.

The structural arrangement of contact element 63 and stop element 65 is the same as that described with reference to contact element 62 and stop element 64. Also, the structure of sealing member 21 and the surrounding housing is similar to that of sealing member 20 and thus will not be described.

Side members and 81, 80 being a fixed member and constituting part of the housing 1, are positioned intermediate the lateral faces of gears 8 and 9 respectively and the side surfaces 84 and 85 of

end plates

3 and 4 respectively. Similarly,

side members

86 and 87 are positioned intermediate the lateral faces of gears 9 and 10 respectively and the side surfaces 84 and 85 of

end plates

3 and 4 respectively. Fluid at discharge pressure is directed to the area intermediate the outboard surfaces on the

side members

80, 81, 86 and 87 and the adjacent side surfaces of

end plates

3 and 4 respectively such that

side members

80, 81, 86 and 87 are urged into sealing engagement with the lateral faces of

gears

8, 9 and 10 respectively to form discharge pockets 56 and 59 bounded by the intermesh 11 of the gear teeth of gears 8 and 9, the intermesh 12 of the gear teeth of gears 9 and 10 and peripheral sealing

contact areas

34 and 35 and 45 and 46 respectively. In order to achieve a firm sealing contact between the side members 80 and 81 and lateral sides of sealing

elements

22 and 23, the fulcrums of stop elements 64 and 65 permit limited pivoting of the sealing member 20 about an axis transverse to the axes of rotation of the gears. This pivoting feature not only insures a tight seal between the side members 80 and 81 and the sealing member 20, but also allows for greater manufacturing tolerances in producing the sealing member. Of course, sealing member 21 pivots in a like manner.

Referring now to FIG. 5, an alternative construction for the sealing members is shown. Channel and 102 in housing 1 each

support contact elements

104 and 106 which are respectively integral parts of

support portions

108 and 110. The main portion of the sealing member is pivotably attached to support

portions

108 and 110 by means of pivots in the form of

pins

114 and 116 which are axially aligned with one another. The

lower surfaces

118 and 120 of

channels

100 and 102 respectively act as stop elements after the sealing element wear permits full contact between these surfaces and contact

elements

104 and 106.

Pins

114 and 116 transmit the net load applied by the springs and pressure in back of the sealing member to

respective surfaces

118 and 120 of housing 1, thus relieving load transfer between the wiping faces of the sealing member and the gears. The degree of rotational freedom of the sealing member permits the member to establish sealing contact between the sideplates in a manner similar to that described with reference to FIG. 1.

Before break-in is fully realized, the sealing member occupies a first position in which the

contact elements

104 and 106 are spaced from

surfaces

118 and 120. During the break-in period, contact

elements

104 and 106 advance towards the

surfaces

118 and 120 as the sealing elements progressively wear. After break-in, when-

contact elements

104 and 106 are in firm contact with surfaces 1 18 and 120, the sealing member 21 will be established in a second or final position.

As the pumps of FIGS. 1 and 5 are not intended to handle a fluid containing highly abrasive contaminants, the sealing members may be made of a relatively soft metal, and the gears may be made of tool steel, thereby contributing to a further weight reduction. Further, the pumping of a fluid, devoid of abrasive elements, should not engender significant journal wear and hence further ability of the sealing member to advance toward the gear after break-in is not considered necessary. However, it should be noted that either a positionable stop element or contact element is within the contemplation of the invention.

It will be understood that the sealing members heretofore described need not each comprise an integral structure, as illustrated, but may include two independent structures having respective wiping surfaces. The term members as used in the specification and the claims is therefore intended to embrace such arrangements. it will be further apprehended that the sealing members of the invention could be applied to pumps with any number of gears.

Obviously many variations and modifications of the invention are possible in light of the above teachings without departing from the scope or spirit of the invention.

What we claim is:

1. In a gear pump, the combination comprising: a housing having at least one inlet, at least one outlet, and a pumping cavity therein; at least two interrneshing gears mounted for rotation within said pumping cavity to pump fluid from said inlet toward said outlet; at least one peripheral tooth-sealing member mounted in said pumping cavity in a first position for eventual movement between said first position and a second position during the break-in period, said sealing member having two arcuate wiping surfaces in contact with the respective peripheries of said gears; a stop element integral with said housing disposed within said cavity; a contact element integral with said sealing member, said contact element being spaced from said stop element in said first position, and adapted to contact said stop element in said second position, means urging the sealing member toward said gears such that said wiping surfaces are in firm contact with said gear peripheries in said first position and said elements are in firm engagement in said second position, and whereby sufficient wear of said wiping surfaces produced by rotation of said gears will cause said member to advance from said first position to said second position.

2. The combination, as defined in claim 1, wherein said stop element comprises: a fulcrum adapted to contact said contact element in said second position such that said sealing member may pivot thereabout on an axis transverse to the axes of rotation of said gears.

3. The combination, as defined in claim 1, wherein said sealing member comprises: a main portion to engage said gears; a support portion integral with said main portion to operatively interconnect said main portion and said housing, said support portion comprising said contact element; and a pivot interconnecting said portions such that said sealing member may pivot thereabout in an axis transverse to the axes of rotation of said gears.

4. The combination, as defined in claim I, wherein said sealing member comprises sealing elements having vertically extending inner surfaces, and wherein means are provided to structurally interconnect said surfaces.

5. The combination, as defined in claim 1, wherein said sealing member at least partially comprises a bronze alloy.

6. In a gear pump, the combination comprising: a housing having at least one inlet, at least one outlet, and a pumping cavity therein; at least two intermeshing gears mounted for rotation within said pumping cavity to pump fluid from said inlet toward said outlet; at least one peripheral tooth-sealing member mounted in said pumping cavity adjacent said outlet for movement toward and away from said gears, the said member having two arcuate wiping surfaces at least substantially engaging the respective peripheries of said gears; at least one side member disposed in said pumping cavity such that it is adapted to contact a lateral side of said sealing member for urging the other lateral side of said sealing member into sealing engagement with the housing, said housing, gears, sealing member and side member sealingly enclosing a high pressure discharge chamber; a pivot engaging said sealing member such that said sealing member may pivot thereabout on an axis transverse to the axes of rotation of said gears; means urging said scaling member into engagement with said pivot, said pivot serving to limit the movement of said sealing member toward said gears; means integral with said pivot operatrvely interconnecting said pivot and said housing such that the load exerted on said pivot by said sealing member is transmitted to said housing.

7. The combination, as defined in claim 6, wherein said sealing member is made of a bronze alloy and said gears are made of tool steel.

Claims

1. In a gear pump, the combination comprising: a housing having at least one inlet, at least one outlet, and a pumping cavity therein; at least two intermeshing gears mounted for rotation within said pumping cavity to pump fluid from said inlet toward said outlet; at least one peripheral tooth-sealing member mounted in said pumping cavity in a first position for eventual movement between said first position and a second position during the break-in period, said sealing member having two arcuate wiping surfaces in contact with the respective peripheries of said gears; a stop element integral with said housing disposed within said cavity; a contact element integral with said sealing member, said contact element being spaced from said stop element in said first position, and adapted to contact said stop element in said second position, means urging the sealing member toward said gears such that said wiping surfaces are in firm contact with said gear peripheries in said first position and said elements are in firm engagement in said second position, and whereby sufficient wear of said wiping surfaces produced by rotation of said gears Will cause said member to advance from said first position to said second position.

4. The combination, as defined in claim 1, wherein said sealing member comprises sealing elements having vertically extending inner surfaces, and wherein means are provided to structurally interconnect said surfaces.

6. In a gear pump, the combination comprising: a housing having at least one inlet, at least one outlet, and a pumping cavity therein; at least two intermeshing gears mounted for rotation within said pumping cavity to pump fluid from said inlet toward said outlet; at least one peripheral tooth-sealing member mounted in said pumping cavity adjacent said outlet for movement toward and away from said gears, the said member having two arcuate wiping surfaces at least substantially engaging the respective peripheries of said gears; at least one side member disposed in said pumping cavity such that it is adapted to contact a lateral side of said sealing member for urging the other lateral side of said sealing member into sealing engagement with the housing, said housing, gears, sealing member and side member sealingly enclosing a high pressure discharge chamber; a pivot engaging said sealing member such that said sealing member may pivot thereabout on an axis transverse to the axes of rotation of said gears; means urging said sealing member into engagement with said pivot, said pivot serving to limit the movement of said sealing member toward said gears; means integral with said pivot operatively interconnecting said pivot and said housing such that the load exerted on said pivot by said sealing member is transmitted to said housing.