US2403796A - Gear pump - Google Patents

Description

' July 9, 1946. .1. C. HANNA- GEAR PUMP 2 she ts-sheet 1 Filed May 15, 1943 INEN TOR. 1/6574 C/ /KZIZ/ZQ,

Patented July 9, 1946 UNITEDTSTAT GEAR PUMP v John CJHanna, Chicago, Ill., assignor to Hanna Engineering Works, Chicago, 111., a corporation of Illinois I Application May 15 1943, Serial No. 487,076

1 The invention relatesto gear pumps and has reference more particularly to an improved construction of pump which will operate with a minimum of slippage and noise and whichwill have increased output per revolution in comparison'to other gear pumps of equal size operating at the same speed.

The conventional gear pump essentially con- 7 Claims. (Cl. 103-426) V 2 Y When the teeth leave their line of contact and enter the inlet of the pump, whichis a space of low pressure, a totally opposite action takes place since the teeth are separating at this time with sists of two mating'gears of equal diameter and equal width rotating in a closely fitting housing. The oil or'other liquid is drawn into the housing at one side of the gear pump and is propelled to the opposite side by means of the gear teeth which trap the liquid in 'the'spaces between the gear teeth and a wallfof the housing and carry it around in the direction of rotation of th gears. Since it is the function of a pump to deliverj liquid at an increased pressure over that supplied to the pump and since present day requirements demand higher and higher pressures, the prevention of leakage or slippage, as it is commonly called, is of the first importance. In the case of a gear pump with its metal to metal construction, extreme accuracy in forming and aligning and close watchfulness in operation and maintenance are required. Notwithstanding the care that may b exercised in the construction and operation of gear pumps, nevertheless slippage isfat all times a serious factor even at rated outputs. When the pumps are operated below their rated capacities obtained by a. reduction in speed, extremely low operating efiiciencies result.

With the pump in operation liquid is delivered by each gear to the outlet side of the pump which thus'contains liquid under a high pressure. The,

'liquid is nipped oil and pinched between the the formation of small sealed spaces under negative pressures, which negative pressures tend to draw the gears together. This vacuum forming action, although probably not as great as the pressure forming action, nevertheless adds to the .wear, vibration and noiseheretofore produced by pumps of this type. v

Therefore an object of the invention is to provide a gear pump of improved construction which will obtain maximum output with acceptable operation by. eliminating the nipping and pinching of the liquid between the gears and by the use of resilient material. on the gear teeth which aids in accomplishing the above and'also is substantially eliminating slippage.

In conventional gear pumps as heretofore constructed the gearshad two very distinct and in a sense contradictory or opposing functions,

l the increase in the size of the teeth, the gear gears. This trapped liquidis infinitesimally compressible and thus the same acts like a solid to push the gears apart. This action takes place for each passing tooth and the same is truly a toggle action, being destructive to the" gears,

shafts and bearings,- and causing excessive vibration and noisewhich for many applications makes this type of pump impractical. H j I V y diameter and width remaining constant.

Another object of the invention is to provide a gear pump having teeth of relatively large size on the pumping gears and wherein means are provided in the nature of driving gears to obtain a smooth driving connection between the pumping gears.

With these and various other objects in view, the invention may consist of certain novel features of construction and operation, as will be more fully described and particularly pointed out in the specification, drawings and claims appended hereto. 7

In the drawings which illustrate an embodiment of the invention and wherein like reference characters are used to designate like parts Figure 1 is a sectional view of the improved pump of the invention in the plane of the axes of the two shafts; t

Figure 2 is a sectional view of the pump taken through the pumping gears substantially along line, 2--2 of Figure 1:

on shaft II.

Figure 3 is a fragmentary sectional view showing the manner in which the liquid is trapped in the spaces between the gear teeth and the housing and propelled in the direction of rotation of the gears;

Figure 4 illustrates the mode of operation of the mating gear teeth as they initially make contact on the outlet side and break contact on the inlet side;

Figure 5 is a sectional view taken substantially H along line 55 of Figure 4;

Figure 6 is an enlarged view of a portion of Figure 5;

Figure '7 is a sectional view of one of the teeth substantially along line 7-7 of Figure a;

Figure 8 is a perspective view of one of the teeth of the pumping gears showing the manner of fitting the resilient packing thereto; and

Figure 9 is a sectional view more clearly illustrating the combination metal and resilient packing gear tooth.

'Ref'erring more particularly to Figure l, the gear pump of the invention is suitably driven from any external source of power by means of shaft H which carries the driving gear 52 and the'pumping' gear E3. The pumping gear I3 is shown integral with shaft H; whereas gear i2 i splined to the shaft by means of internal teeth formed in the central opening of the gear, which teeth have interfitting relation with grooves is Shaft H is suitably journalled in the gear housing by means of bearings i5, i5 and IT. The packing l8 and the packing gland is serve to prevent leakage of the liquid in an axial direction along shaft H. The gear l2 has meshing relation 'Witha similar gear 2!]. Said gear Zll dr'iv's the follower shaft 21 since "said gear is splined to the'follower shaft by means of teeth formed in the gear which have interfitting relationwith grooves 22 provided on said follower shaft. The bearings 23, 2:3 and Z5 suitably journal follower shaft 2i and thus the integral pumping gear 25 of substantially the same size and width as gear l3 and which has meshing relation with saidgear.

The housing for the present pump consists of a gear section 28, a bearing section 29, a cover 36 forjthe driving end, a second bearing section 35, and acover 32 for the closed end. In assembling the pump the shafts with their pumping gears 5'1 are inserted within a portion of the housing formed by the gear section 28 the bearing section 3| and the end coverC-lZ. The bearing-section. 29 is then applied, whereupon the driving gears l2 and 25! are fitted to the driving and follower shafts respectively. The end cover 38 is then applied to complete the housing, it being understood that the various sections of the housing are suitably bolted or otherwise secured together toprovide a unitary structure.

The driving gears 32 and 28 are so named because shafts H and it are driven by them. The splined relation which the driving gear have with their respective shafts provides for an aocurate and permanent fit such as will give minimum play and therefore a minimum of back lash. By this nieansthe relatively angular mo 4 ance of undue heating of said gear and likewise the oil.

Figure 2 illustrates the manner in which the pumping gears operate to pump liquid which is drawn into the housing through the inlet 33, the inlet space thus provided being indicated by numeral 34. The liquid is propelled in the direction of rotation of the gears since it is trapped in the spaces formed by the gear teeth 35 and the arcuate surfaces 35 of the groove in the gear section 28 of the housing. The liquid is discharged into the outlet space 3"! and eventually said liquid is conducted from the housing through outlet 38. In Figure 3 a portion of Figure 2 been enlarged to illustrate the smooth gradual approach of the teeth 35 into contact with the arcuate surface 36 of the gear section.

The present invention is based on the concept that the best means of preventing leakage between two. relatively moving parts is to make one of these parts of metal or'o-ther rigid material with as perfect surfaces a possible both as to form and finish and to make the contacting portions of the other relatively moving parts of a soft and highly resilient material which will rub against the hard surfaces with sufficient pressure to prevent leakage of the liquid between them. In the following description this resilient part is called packing and the same is mounted upon and securely attached to the metal of each gear tooth.

Referring more particularly to Figures 4, 5, 7 and 8, it will be seen that each gear tooth indicated in its entirety by numeral 35 consists partly i of metal and partly of resilient packing. The

packing includes strips 40 of small cross sectional area which extend around each gear on the respective sides thereof approximately at the clearance circle and which therefore have contact with the gear teeth at the roots of the teeth. The

circular strip for each gear are joined by integral portions having interfitting relation with the metal of the their respective tooth. As shown in Figure 8, the circular strip 48 has an integral strip 4| extending upwardly at the corner of the tooth 35 and on the leading side thereof which is integral with a strip 42 extending along the top edge'of the tooth also on said leading side. The connecting strips 43 join the portion 24 thereto, which portion covers the entire area of the tooth on the follower side. The said portion 44 of the resilient packing applied to each tooth includes a'fiap 4-5'adapted to fitinto a recess or space it when pressure is applied to said The resilient packing applied to each gear tooth effectively prevents leakage between the trunk portion of the gears and the bearing sections 29 and 31 from the high pressure or outlet side back into the low pressure or inlet side. The

circular strips 40 function primarily to accomplish this objective. In Figures 5 and 6 the strips 40 are shown in section and it will be observed that groove 48 is somewhat larger than said strips. This groove makes it possible for the liquid under pressure to act against the surface of thestrip thus exposed by'the groove in such manner as to force the curved front surface 49 against the wall of its adjacent bearing section.

Leakage I between the pump gears and said bearing s ections from onetooth space to the next tooth space is prevented by the pressure ofportion 44 of the packing which, is mounted on the follower side of each tooth, againstthe said bear ing sections 29 and 3i, which-pressure is caused ibylthe lateral spread. of'portionnfl under the pressure ofthe liquidwhile the teeth are moving from the outlet space to the inlet space. Corner strips 4!; are provided to guard against leakage between :thelend'areas of the teeth and. said bearing sections during the passage of the teeth from the inlet space to the outlet'space. Leakage over the-addendum from one toothspace to the next tooth space during travel of the teeth between the outlet side and the inlet side is prevented by the contact between the mating teeth; vTightness over the'addenda of the'teeth is made 'more secure by the action of centrifugal force upon the flaps 45 which acts additionally with the pressure-of the liquid to force the flap against the followingtoothr :L'eakage over the addendum from one tooth spaceto the follow.-

ing tooth space-during. the travel of:the teeth 'into contact with tooth 35a on gear I 3; Tooth 35a'is in contact with tooth 351). This full contact is due to the differential pressure efiect on the 'flap caused by the; pressure of the liquid. The centrifugal actionon the fiap serves to'make thisc'ontact more eflt'ective. In'the position-of the gears showhiuFigiire 4 the liquid is escapfrom space Mi through the'gap 50 whichis still'open although the same is gradually closing. Due" to the resilient character of the packing material slight excess of pressure created in the liquid which is being forced from between the gears deforms the tooth 35a at the corner 5| sumciently'to allow practically all the liquid to be forced out of the gap 50. During this discharging action space 46 has been closed by'its flap- 45, which flap is gradually forced into closing position beginning at the extreme. inner end of its space 46. This closed condition is shown by contact ofgear tooth 350 with tooth 35b. Rotation of the teeth away from the line of contact causes movement of the teeth away from each other to produce a gradually opening gap identified by numeral 52. The provision of the flap with its free end toward this increasing space makes it possible for the liquid to be drawn into this space as the same is being created.

It can be shown mathematically that a pump havinggear teeth of large size will deliver a greater volume of liquid per revolution than if the gear teeth were smaller in size, their pitch diameter and width being the same in both cases. The per revolution output of the present pump is therefore increased over present designs by making the gear-teeth of ample size insofar as is practicable and smooth operation is attained byproviding auxiliary driving gears which leave the pumping gears with only one operation to perform, namely, that of pumping the greatest volume of liquid for any particular speed and with the minimum ofslippage. Smooth operation is further assured by the provision of resilient packing on each gear tooth of the pumping gears, This eliminates nipping and pinching of the liquid between gears which has been the source ooflexcessiv'e strain, noise and vibration in pumps asheretofore constructed. In providinga resilient contact with the rigid metal parts of a coacting tooth the packin additionally prevents leakage of the'liquid especially ,past thelinevof contact from the high pressure side to the low pressure side. Any reduction in, leakage or slippage, as it is generally called, increases the efiiciency of the pump.

The invention is notlimited to or by details of construction of the particular embodiment thereof illustrated 'by the drawings as various other forms of the device will of course be apparent to those skilled in the art without departing from the spirit of the invention or the scope of the claims. a For example, although the present gear pump has been described as having particular utility in the pumping of oil and other liquids, the said device'is not necessarily limited thereto -si'n'ce it canbe used very advantageously; in the pumping or compressing of air and othergases. I

What is claimed is:

1. In a gear pump, a housing, a driving shaft and a follower shaft'journalled by the housing in spaced parallel relation, a pumping gear fixed to each. shaft, said gears having meshing relationwhereby the teeth of said gears have contact as they approach, pass through, and leave the plane of said shafts, a compartment provided by the housing adapted to receive said gears, an inlet to said compartment on one side of the plane of contachan outlet for said compartment on theoppQsite side of said plane of contact, and resilient material on the teeth of each pumping gear wherebysaid teeth consist partly of rigid 'material and partly of 1 resilient material,v said I material being located at the edges only of each tooth on the leading'side-thereof and extending to completelyrcover the follower side of .each

tooth from edge to edge and from top to bottom thereof. V

2. In a gear pump, a housing, a driving shaft and a follower shaft journalled by the housing in spaced parallel relation, apumping gear fixed to each shaft, said gears having meshing relation whereby the teeth of said gears have contact as they approach, pass through, andleave the plane of said shafts, a compartment provided by the housing adapted to receive said gears, an inlet to said compartment on one side of the plane of contact,'an outlet for said compartment on' the opposite side of said plane of contact, and resilient material on'the teeth of each pumping gear whereby the teeth consist partly of rigid material and partly of resilient material, said material having location only in recesses at the edges of each tooth on the leading side of the same and extending in recesses on the top 'of each tooth at the respective sides to completely cover the follower side thereof edge to edge and from top to bottom of the tooth.

3. In a gear pump, a housing, a driving shaft and a follower shaft journalled by the housing in spaced parallel relation, a pumping gear of metal fixed to each shaft, said gears having meshing relation whereby the teeth of said gears have contact as they approach, pass through, and leave the plane of said shafts, a compartment provided by the housing adapted to receive said gears, an inlet to said compartment on one side of th plane of contact, an outlet for'said compartment on the opposite side of said plane of contact, resilient material on the teeth of each pumping gear whereby said teeth consist partly of metal and partly of resilient material, said resilient material having location in recesses at the edges ofl'each tooth ontheileading side. and extending in recesses -on the top of each tooth to completely cover the followerside thereof, and said resilient material on the follower, side providing a flap located adjacent. the. base of each tooth space for eliminating the pinching and trapping of liquidiin said tooth space during meshing of the gear teeth.

4. In a gear pump, a housing, a..olriving shaft and a follower shaft journalled b the housing in spaced parallel relation, a pumping gear of metal fixed to each shaft, said gears having meshing relation wherebythe teeth ofsaid gears have contact as they approachpass through, and leave the plane of said shafts, a compartment provided by, the housing adapted toreceive-said gears, an inlet to said compartment on one side of the plane of contact, an; outlet for said compartment on the, opposite side of said plane. of contact, resilient material on the teeth of -each pumping gear, said material completely covering the follower side of each tooth and providing a flap located adjacent the base of its tooth space, and a gap located directly below said flap, Whereby the pinching and trapping of liquid in said tooth space during meshing of the gear teeth is substantially prevented by the maintenance of an exit from the diminishing tooth space made possibl by the resilient nature of said material.

5. In a gear pump, a housing, a driving shaft and a follower shaft journalled by the housing in spaced parallel relation, a pumping gear of metal fixed to each shaft, said gears having meshing relation whereby the teeth of said gears have contact as they approach, pass through, and leave the plane of said shafts, a compartment provided by the housing adapted to receive said gears, an inlet to said compartment on one side of the plane of contact, an outlet for said compartment on the opposite side of said plane of contact, resilient material .on the. teeth of each pumping, gear, said material completely covering thefollower side of each tooth and providing a flap located adjacent the base. of. its toothspace, anda gap located directly below said. flap, whereby suction action caused, by a tooth moving out of its. tooth spacev is substantially prevented by the maintenance of a passage into the increasing spacemade possible by theresilient nature of the material.

6; In a device for providing 'fiuid power, a pair of cooperatingrotary pumpi-ng'elements, a housing fore-said pumping elements providing an inlet and an, outlet on the respectivev sides of the housing, a pair of driving gears for-operatively connectingsaid rotary pumping elements whereby the elements. are maintained in definite. relation with each other, resilient material in associated relation with theiindividual gearteeth of each said rotary pumping element for preventing leak= age, past said-teeth from the high pressure, side to the low pressure side-of the housing duringv a pumping operation,. said resilient tmaterial .com-

pletely coveringthefollower side of each tooth and including, portions locatedin recesses at the edges of each. toothgon the leading side thereof and extending in recesses :acrossrthe'top .of :each tooth at, the sides;thereof, and circularxstrips of resilient material having location on, the, respec: tive :-sides,cf1each rotary pumping element approximately atHthe clearance circle for joining with said portions onthe gear teeth.

7. In a device for providing'fluid power, a, pair of cooperating. rotary pumpingelemen-ts, a house ing for said pumping elements providing'an inlet and an outlet on therespective sideslofthe'housing, a pair of driving, gears for; operatively connecting said rotary pumping; elements whereby the elements are maintained indefinite;relation with each other, resilient materialin associated relation with the individual; gear teethof ,each said rotary pumping element for preventingleak? age past saidteeth from the high-pressure side to the low pressure side-of the housing, during a pumping operation, said ,resilient material com pletely covering thefollowerside of each-tooth and including portions located in recesses at the edges of-eachtooth on theleading side and extend-ing inirecesses on the top of. each tooth at the sides thereof, and circular strips having. location inrecesses on the respective sides of each rotary; pumping element approximately at the clearance circle for -joining, withsaid portions onthe gear-teeth and with said resilient material covering the; follower sideof the teeth.

JOHN C. HANNAa

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