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Full text of "US Patent 2601003: Gear pump"

June 17, 1952 

Filed May 17, 1946 

G.W. PONTIUS, TIT 
GEAR PUMP 

2,601,003 

2- SHEETS--SHEET 1 



June 17, 192 

F£1ed May 17, 1946 

G.W. PONTIUS, IE 
GEAR PUMP 

2,601,003 

2 SHEETS---SHEET 2 

/ TTO,qA/6"Y . 



Patented June 17, 1952 2,601,003 

UNITED STATES PATENT 

1 
This invention relates fo improvements in gear 
pumps. 
Since the advent of the gear pump there has 
always been the problem of trapping fluid 
tween the meshing teeth of the gears. Fiuid 
trapped between the teeth adversely affects the 
mechanical efiïciency and pump lire. Vrious 
ways have been proposed for releasing this 
trapped fiuid but all seem fo have some objec- 
tionable feature which renders the pump im- 
practical and/or expensive. Not a few of the 
attempts ai relieving the entrapped fluid have 
resulted in a loss of volumetric efficiency with- 
out having accomplished the primary objective 
of adequately relievin high trapping pressures. 
If is, therefore, an object of this invention fo 
oovide a gear pump which has ifs teeth formed 
fo allow the escape of fluid confmed between 
teeth which are in meshing relationship. 
A îurther important object of the invention 
resides in the provision of a gear pump, the 
teeth of which have ffrooves in their faces ex- 
tending frorn the addendum circle fo a point in 
their faces where the line of action intersects 
the tooth faces when two mating tooth surfaces 
have their pitch lines substantially co-extensive 
ai the pitch point. 
A yet more important object of the invention 
resides in the provision of a gear pump, the teeth 
of which have cutout portions in the exterior 
surfaces thereof fo provide escape means for 
fluid conflned between teeth .in mesh. 
A still further important object of the in- 
vention resides in the provision of a gear pump 
equipped with means for communicating the 
space between teeth in mesh fo either the out- 
let or the inlet ai II rimes. 
Another important object of the invention 
the provision of a ffear pump, the teeth of which 
have their surfaces constituted fo provide an 
escape for fluid between teeth in mesh. 
The above and other objects and features of 
the invention will be apparent from the follow- 
ug description of the device taken in connection 
with the accompanying drawings which form a 
part oï this speciflction and in which: 
Figure ! is a top plan view of one form of 
ear purnp incorporating the invention; 
Figure 2 is an isometric view of one of the 
gears of the pump; 
Fiure 3 is an enlarged view of the two gears 
n meshing relationship with portions broken 
away; 
Figure 4 is an enlarged view of parts of two 
ears utilizing a modified form of the invention; 
Fure 5 is taken on the line -- in Figure 4 
showing a view of one of the teeth; nd 
Figure 6 is a view of the two gears of Figure 1 
with portions removed, and showing the 

2,60î,003 
GEA PUMP 
George W. Pontius, III, Sotth Bend, Ind., 
signor to Bendix Aviation Corporation, South 
Bend, Ind., a corporation of Deaware 
Application May î7, î96, Serial No. 670,452 
10 Clams. (CI. î03--î26) 

OFFICE 

2 
tionship of the teeth af their initial stage of 
mesh. 
leferring now to Figure î, reference numeral 
 designates a pump housing or body having a 
 cover  mounted thereon by screws . The 
body is provided with an iniet 6 and an ourlet 
. A driving gear  is rotatably disposed 
within the body in meshing relationship fo a 
gear . The latter gear is keyed fo a shaft 
10  which is carried by the ody. The driving 
gear ] is keyed fo a shaft  and constructed 
and arranged fo rotate the gears. The interior 
of th pump body or housing is formed at $ nd 
$ to cooperate with the gears  and  for 
] conveying fluid from the inlet $ to the ourlet 
 where the fluid is put under pressure. The 
driving gear  is considered to rotate in a clock- 
wise direction as illustrated in Figure i by the 
direction of the arrow. 
20 The gears  and  a'e of the spur gear type 
with teeth 3 and $ having tips  and  
 spectively, leferring now to Figures i and 
these gears are comprised of an addendum circle 
, a pitch circle , base circle , dedendum 
2 circle , pitch line , pitch point $ and a line 
of action . The tooth surfaces of the respec- 
tive teeth are located between the addendum 
and dedendum circles and are divided by the 
pitch lines $ into tooth faces  and tooth 
0 flanks . 
Fluid is received af the inlet by the .gear teeth 
and carried fo the ourlet in a manner familiar 
fo those skilled in the art. To prevent the 
trapment of fluid in pockets  and  formed 
 between mshing teeth  and  the leading 
faces of the teeth  ar slotted or channelled 
ai S, and the trailing faces of teeth  are 
channelled af  as best shown in Figures î fo 
Backlash, designated at 3, is formed between 
40 contiguous faces of the meshing gears and pro- 
rides communication between the pockets  and 
 which actually move as the gears rotate. 
Backlash rnay be obtained in any suitable 
manner familiar to those skilled in the art. I 
.5 actual practice the slots or channels would be 
ïormed in both faces of a gear tooth to permit 
operation of the pump in ëither direction.  Sec 
Figure . 
These channels are disposed in the tooth faces 
. so that when the teeth  and  move into con- 
tact, the fluid confined in the space or pockets 
 and  between the teeth is allowed to escape. 
See Figure 6. I is obvious that if an escape of 
some kind is not provided for this confined fluid 
: thc gear teeth would tend to compress the sub- 
stantially non-compressible fluid, such as off, 
which in ail probabilities would result in pump 
destruction. That is, at the rime of initial con- 
tact between teeth  and 3 (sec Figure 6) 
C0 poçke$  i smaller in volume than the pocket 



2»601»003 

3 
58. As the driving gear 20 rotates the driven 
gear 22 the pocket 55 increases in volume and 
pocket 55 decreases in volume but the rate of 
decrease in volume of the latter pocket is greater 
than the rate of increase in volume of the former 5 
pocket until a predeterntined position of rota- 
tion of the teeth is reached, whereby there is 
a tendency to put the confined or entrapped fluid 
under pressure. 
If these channels are not properly and accu- I0 
rately located in the teeth faces mal-function of 
the pump is inevitable. For optimum pump op- 
eration it has been ïound that the channels 0 
and 62 must be of a definite length. The length, 
of course, varies with gear size and construction. 15 
The wdth V of the channels should be such as to 
allow a reasonable flow velocity of fluid from the 
pockets. If shouid ibe noted that the width W of 
the channels iS always less than the tooth width 
.. in order to provide driving contact in all positions 20 
of meshing teeth. When teeth 32 and 34 are in 
con_tact at predetermined points A and B along 
their surfaces th length of the channels 6 and 
52 is eqtal to the distance from the points of 
contact o said teeth to the addendum circle. The OE5 
points A and B are located by the intersection of 
the line of action with the points of tangency 
between the driving and driven teeth of gears 20 
and 2 respectively. That is, stating it another 
way, the location of the channels is determined 30 
as follows: When two mating tooth surfaces have 
their pitch lines substantially coextensive af the 
pitch point, tooth faces are channelled or other- 
wise exteriorly relieved ïrom the addendum cir- 
cles to points where the line of action intersects , 
the tooth Ïaces. 
If should be noted that when the line of action 
5 passes through points A and B as aïoremen- 
tioned pockets 56 and 50 are substantially of the 
saine volume. When contact between gea teeth 4o 
3 and 34 was first ruade pocket  was larger 
in volume than pocket 55. See Figure 6. In the 
position shown in Figures 1 and 3 the pockets 0 
and 5 have just closed to outiet by reason of the 
contact between the tooth faces across the entire 5 
teoth width to thereby close the passage or chan- 
nel 6. Likewise, channel 6 is also closed at this 
instant. A slight amount of rotation of gear  
wfll open the passage 0 to communicate the 
pockets with the inlet. Continued rotation of the 50 
driving gear, beyond where the line of action 
passes through points A and B, wfll cause pocket 
5 to decrease in volume but at a rate slower than 
the increase in volume of pocket 56 to thereby 
tend to create a low pressure or vacuum in the 5 
pocket or chamber 56, which low pressure is con- 
ducive to gear chatter. However, as aforemen- 
ti0ned this condition is avoided by providing a 
channel or passage 60 which communicates pock- 
et 56 with the inlet 6 substantially simultane- 60 
ously with the sealing of the chamber or pocket 
55 from the ourlet  as best shown in Figures 1 
and 3. To illustrate the criticalness of location 
and size of these passages it will be well to point 
out that if the channels are teo long there wfll 65 
be leakage from the ourlet to the inlet whereby 
the volumetric efliciency of the pump will be re- 
duced and if too short high pressures will be de- 
veloped within the pockets between the gears. 
It should be emphasized that a gear pump in- 70 
corporating the features of this invention has a 
relatively higher eflciency. 
Figure 4 is a modifled form of the invention 
and is adapted to function in much the saine 
manner as the preferred embodiment of Figures 75 

4 
1 to 3. Instead of the tooth faces being grooved 
as hereinbefore described, the tooth flanks are 
grooved at @ and 2 of teeth  and 5 respec- 
tively. To permit use of the pump in either di- 
rection of rotation both flanks of a tooth are 
channelled. However, for clockwise rotation, 
only channels 8 and 2 will be needed. For 
counter-clockwise rotation channels  and 2 
are used. When two mating teoth surfaces bave 
their pitch lines substantially coextensive at the 
pitch point tooth flanks are channelled from a 
predetermined point below the base circles fo a 
point in the tooth flanks where the line of action 
intersects the tooth flanks to thereby provide an 
escape for the entrapped fluid. The piteh line is 
designated by the numeral 00 in Figure 5. 
Although the invention has been described in 
connection with certain speciflc embodiments the 
principles are susceptible of numerous other ap- 
plications that will readily occur to persons 
skilled in the art. The invention is, therefore, fo 
be llmited only as indicated by the scope of the 
appended claims. 
Having thus described the various ïeatures of 
the invention, what I claire as new and desire fo 
secure by Letters Patent is: 
1. In a fluid pump or motor, a body having 
inlet and outiet ports, a driving gear located in 
the body, a driven gear, said driving and driven 
gears having teeth in mesh with faces in con- 
tact relationship and backlash therebetween, said 
teeth in mesh forming pockets therebetween in 
whlch fluid is entrapped, and a channel in the 
leading tooth faces of each of the teeth of the 
drlving gear ,and in the trailing tooth faces of 
each of the teeth of the driven gear extending 
along the tooth faces ïrom the addendum circles 
of the gears fo a point in the tooth faces inter- 
sected by the line of action at a rime when the 
piteh lines of two mating gear teeth pass through 
the piteh point. 
2. The method of locating channe]s in the 
tooth fa.ces of mating gears having back!ash 
therebetween to provide a means of escape for 
fluid entrapped between the teeth in mesh, the 
steps of which comprise placing the gear teeth 
in engaging relationship so that two mating 
tooth surfaces bave their pitch lines substantialiy 
coextensive ai the pitch point, and locating a 
channel in the leading tootl] face of one oï the 
gears and in the trailing tooth face of the other 
gear so that said channel will extend along the 
teoth faces from a point in the tooth faces wherc 
the line of action intersects said tooth faces fo 
the addendum circles of the respective gears. 
3. In a fluid pump or motor, a body having an 
inlet and an ourlet, driving and driven gears 
disposed within the body with backlash there- 
between, said gears havin teeth with surfaces 
in contact when the gears are in meshing rela- 
tionship, the teeth in mesh having pockets 
formed therebetween in which fluid is entrapped, 
and a channel in the flanks of the leading tooth 
surfaces of each of the teeth of the dïiving gear 
and in the flanks of the trailing tooth surfaces 
of each of the teeth of the driven gear extend- 
ing from a predetermined point below the base 
circles of the gears to a point where the line of 
action intersects the tooth flanks when the two 
mating tooth surfaces have their pitch lines sub- 
stantially coextensive at the pitch point. 
4. A fluid pump or motor comprising a body 
having inlet and outiet ports, a pair of gears 
locaed in the body in meshing relationship and 



»601»008 

having backlash therebetween, said meshing 
gears constructed and arranged fo form two 
moving pockets between the teeth in mesh and 
having variable volumes which entrap fluid, the 
increase in volume of one of the pockets being 
ata slower rate than the decrease in volume of 
the other pocket, whereby the entrapped fluid in 
said one pocket tends tobe subjected to a de- 
creasing pressure and the entrapped fluid in said 
other pocket tends tobe subjected to an increas- 
ing pressure, and means providing an escape for 
the entrapped fluid fïom the pockets comprising 
a passage in the trafling tooth faces of the teeth 
of one of said gears and in theqeading tooth 
faces of the teeth of the other gent, said passage 
extending from the addendum circles of said 
gears to a point in the tooth faces of said gears 
intersected by the line of action ata rime when 
the pitch lines of two mating gear teeth pass 
through the pitch point. 
5. A fluid pump or motor comprising a body 
having inlet and ourlet ports, a pair of gears 
located in the body with the teeth of said gears 
meshing in such a manner as fo provide backlash 
therebetween, said meshing teeth .constructed 
and arranged to form two moving pockets be- 
tween the teeth in mesh having variable volumes 
which entrap fluid, the increase in volume of 
one of the pockets being ata slower rate than 
the decrease in volume of the other pocket, 
whereby the entrapped fluid in said one pocket 
tends to be subjected fo a decreasing pressure 
and the entrapped fluid in said other pocket 
tends tobe subjected to an increasing pressure, 
and means providing an escape for the entrapped 
fluid from the pockets comprising a passage in 
the leading tooth faces of each of the teeth of 
one of the gears and in the trailing tooth faces 
of each of the teeth of the other gear, said Pas- 
sage extending from the addendum circles of the 
gears to a point in the tooth fa.ces intersected by 
the line of action at a rime when the pitch lines 
of two mating gear teeth pass through the pitch 
point, whereby said other pocket is communi- 
cated to ourlet to expel the entrapped fluid there- 
fo and said one pocket is communicated to inlet 
to equalize the pressure therein after communi- 
cation with the ourlet is cut off. 
6. In a fluid pump or motor, a body having 
inlet and ourlet ports, a pair of gears located in 
the body in meshing relationship, said gears hav- 
ing backlash, with the teeth in mesh forming 
movinŒE pockets therebetween in which fluid is 
œentrapped, and a relief in the trailing tooth 
faces of one of the gears and in the leading tooth 
faces of the other gear, said relief extending 
from the addendum circles of said gears to a 
point in the tooth face of said gears intersected 
by the line of action af a rime when the pitch 
lines of two mating gear teeth are substantially 
coextensive at the piteh point. 
7. In a fluid pump or motor, a body having 
inlet and ourlet ports, driving and driven gears 
in the body arranged in meshing relationship, 
with the teeth in mesh forming pockets there- 
between in which fiuid is entrapped, said gears 
having backlash therebetween, and a channel in 
the leading tooth faces of each of the teeth of 
the driving gear and in the trafling tooth faces 
of each of the teeth of the driven gear extending 
along the tooth faces from the tooth tips of the 
gears to a line in the teoth faces normal to and 
intersecting the line of action ata rime when the 
Pitch lines of two mating gear teeth pass through 
the pitch point. 

6 
8. In a fluid pump or motor, a body having 
inlet and out]et ports, driving .and driven gears 
in the body arranged in meshing relationship, 
with the teeth in mesh forming pockets there- 
5 between in which fluid is entrapped, said gears 
having backlash therebetween; and a channel in 
the leading tooth faces of each of the teeth oî 
one of the gears and in the trafling toth faces 
of each of the teeth of the other gear extending 
lO along the tooth faces from the tooth tips of the 
gears fo a line in the ooth faces normal fo and 
intersecting the line of action ata rime when 
the pitch lines of two m.,ting gear teeth pass 
tln'ough the pitch point. 
15 9. In a fluid pump or moter, inlet and ourlet 
ports, a pair of gears arranged in meshing rela- 
tionship with the teeth in mesh forming two 
pockets therebetween in whichfluid is entrapped, 
said gears having backlash, and a charmel in the 
20 leading tooth surfaces of each of. the teeth of 
one of the gears and in the trailing tooth sur- 
faces of each of the teeth of the other gear, each 
of said channels of one of said gears having one 
of its ends located in the surface ata predeter- 
25 mined point so as to communicate one of the 
pockets with one of the ports belote the pitch 
lines of the two mating gear teeth forming the 
pockets are coextensive and each of said chan- 
nels of the other gear having one of its ends 
30 located in the surface af a pïedetermined point 
so as to communicate the other pocket with the 
other port after said pitch lines are coextensive, 
the other end of each of said .channels being 
located in the surface ata point where the line 
35 of action intersects the tooth surfaces when two 
mating tooth surfaces have their pitch lines co- 
extensive af the pitch point. 
10. In a fluid pump or m0tor, driving and 
driven gears arranged in meshing relationship 
40 with the teeth in mesh forming pockets there- 
between in which fluid is entrapped, said gears 
having blacklash, and a channel in the flanks of 
the leading tooth surfaces of each of the teeth 
of one of the gears and in the flanks of the 
45 trafling tooth surfaces of each of the teeth of 
the other gear extending along the tooth flanks 
from a predetermined location therein below the 
base circles of the gears to a point where the line 
of action intersects the tooth flanks when two 
50 mating tooth surfaces bave their pitch lines sub- 
stantialiy coextensive at the pitch point. 
GEORGE W. PONTIUS, III. 
55 REFERENCES CITED 
The following references are of record in the 
file of this patent: 
UN1TED STATES PATENTS 

6O 

65 

7O 

7 

Number 
884,812 
1,252,160 
1,633,793 
1,686,867 
1,712,095 
1,728,529 
1,813,875 
1,923,268 
1,976,227 
2,159,744 
2,344,628 

Number 
439,908 

Naine Date 
Gfllmor et al ....... Apr. 14, 1908 
Pagel .............. Jan. 1, 1918 
Porst ............. June 28, 1927 
Kuhn .............. Oct. 9, 1928 
Schurr ............. May 7, 1929 
Butler ............ Sept. 17, 1929 
Fehr ............... July 7, 1931 
Jensen ............ Aug. 22, 1933 
Howard ............ Oct. 9, 1934 
Maglott ............ M.ay 23, 1939 
Monahan .......... Mat. 21, 1944 
FOREIGN PATENTS 
Country Date 
Great Britain ...... Dec. 17, 1935