Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FIELD S)F THE Il!~E~TION
This invention relates to grease guns.
BAt~KGROU27D AND SUM~ARY OF T~ IEN~ION
Grease guns are used to force grease from a
cartridge through a cavity and associated conduit in
the head of the grease gun to the object being
serviced. Typically, grease guns use a combination of
a lever and piston to propel the grease from the
cavity. The cavity is filled for example by exerting
pressure on the cartridge which forces grease into the
cavity. In typical devices, the delivery of grease
into the cavity is not efficient, and in particular
air may be trapped in the chamber holding the grease
which may make it impossible to pump grease.
In one proposed device to over come this
defect, shown in United States patent no. 2,521,569 to
Davis, a lever is used to propel grease from a chamber
through a cylinder into a conduit. A threaded rod is
pasaed through the chamber holding the grease and a
movable follower is threaded on the rod. The
downstroke of the lever forces grease in the cylinder
~ ~ through the conduit and simultaneously activates a
;~ ratchet that turns the threaded rod. As the rod turns,
the follower moves in the chamber towards the conduit,
~ compressing the grease and forcing it into the
cylinder. In this manner, grease is delivered from the
chamber to the conduit.
In another device by Davis (United States
patent no. 2,477,726), there is shown a toothed rod
3~5~ disposed within a chamber. A cammed piston
reciprocates the toothed rod, so that it moves
; lengthwise of the chamber on the up and down strokes
of the~piston. As the rod moves away from the head, it
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compresses a spring. A follower on the rod stays in
place when the rod moves away from the head. On the
downstroke, the compressed spring forces the rod
towards the head and pawls on the follower catch the
teeth on the rod, forcing the follower towards the
head and pushing grease into a cavity in the head.
These devices have disadvantages. The
ratchet, and the teeth and pawls, are in the chamber
containing the grease which impedes the operation of
the ratchet, particularly in cold conditions. Also, in
the case of the Davis patent no. 2,5Z1,569, when the
piston has moved to its clvsest position to the head
of the grease gun (chamber empty) it must be rotated
all the way back to the top of the rod to reset it. In
the case of the other Davis patent, the pawls must be
moved by hand from inside the chamber. Further, in the
case of the patent no. 2,521,569, the ratchet is
operated simultaneously~ with the downstroke that
forces grease out of the cavity which may cause the
device to jam. Davis has addressed this problem by
providing a clutched disc on the follower.
Other devices have used springs to urge the
grease forward in the chamber. ~owever, in the case of
air trapped in the chamber, the spring may not have
~sufficient force to overcome the air pressure.
; The inventor has provided an improved grease
gun to address the problems in existing grease guns.
In one aspect of the invention, the invention provides
a grease gun including a chamber with a cap on one end~ ; 3~ and head on the other end. Inside the head is a cavity
which may receive grease from the chamber. Part of the
cavity forms a cylinder in which reciprocates a
piston.~The piston in turn operates a ratchet on its
upward stroke, as grease fills the cylinder. The
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ratchet turns a rod on which is threaded a follower.
The rotation of the rod moves the follower towards the
head and forces grease into the cavity and thus into
the cylinder. On the downward stroke, the piston is
disengaged from the ratchet and forces grease out of
the cavity into a discharge conduit. Valves control
movement in and out of the cavity.
The ratchet is rotatably mounted outside of
the chamber. Also, the grease gun preferably includes
means for disengaging the follower from the rod,
operable from outside of the chamber, preferably a
split nut threaded on the rod adjacent the follower;
a shoulder adjacent the cap and oriented to split the
split nut on engagement with the split nut; and means
for resetting the split nut on the rod.
BRIEF ~ES~RIPTION OF THE DRAWI~GS
There will now be described a preferred
embodiment of the invention, with reference to the
drawings, by way of illustration, in which like
numerals denote like elements and in which:
Figure lA is a section through an embodiment
of the invention showing the grease gun loaded and
ready for use;
Figure lB is a plan view of a ratchet and
pawl for use with the grease gun of Figure lA;
Figure 2 is a section through an embodiment
of the invention showing the operation of the grease
gun when the handle is stroked upwards; and
Figure 3 is a section of part of the grease
gun showing the rod moved to one end of the gun.
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DETAILED D~SCRIPTION OF PREFER~ED E~OD~ME~TS
Referring to Figures lA, lB and 2 there is
shown a grease gun indicated generally at 10. The
grease gun is formed by a chamber 12 for holding
grease 14. At a first end of the chamber 12 is a head
16, and at a second end is a cap 18, both threaded
onto the chamber 12. Within the chamber 12 is a
grease cartridge 30 of conventional construction. The
cap 18 includes a setting ring 20 having splines 21
that protrude through slots in the cap 18. The head 16
includes a cavity 22 in fluid connection with the
chamber 12 for receiving grease from the chamber. The
cavity 22 is fluidly connected to a discharge conduit
24 which may be formed for attachment to a machine
part requiring servicing. A conduit 25 with check
valve 27 may be provided ~or bulk filling of the
chamber 12. A part o~ the cavity 22 is formed as a
cylinder 26.
In the head, and extending into the cylinder
26 is a user activated piston 28. The piston 28 moves
in the cylinder from the bottom of the cylinder (Fig.
2) to the top of the cylinder (Fig. lA) (and vice
versa). The piston 28 as shown is hand operated by a
lever 32 but may be operated automatically or by a
pistol grip with trigger (not shown). With grease in
; ; ~ the cylinder, the downward stroke of the piston will
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force grease into th~ cavity, while the upward stroke
of the piston will tend to suck grease into the
- cylinder from the cavity.
30 ~ A ratchet 34 is formed from a disc 36 and a
shaft 38 3ournalled within the head 16. The ratchet is
located within the head at one end of the shaft. The
other end of the shaft includes a socket 42 and pin
44.~A pawl 46 mounted ~or rotation on the piston 28
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engages with the teeth on the ratchet. Upon movement
of the piston 28 on the downstroke of the lever, the
pawl 46 clears the teeth, while on the upstroke, the
pawl 46 engages the teeth and moves the ratchet 34.
Mounted axially within the chamber 12 and
extending from the head 16 to and through the cap 18
is a threaded rod 48. A follower 52 is threaded onto
the rod 48. The follower 52 is snugly fitted within
the chamber 12. One end 50 of the rod 48 engages with
the pin 44 so that rotation of the ratchet 34 rotates
the rod 48. On the other end 64 of the rod 48 is a
handle 66.
The follower 52 includes a split nut 56, and
the end of the rod 48 includes a bevelled surface or
shoulder 58 formed for engagement with the split nut
56. The distance from the end 62 of the split nut 56
to the follower 52 should be less that the length of
the splines 21 of the setting ring 20, as discussed
below.
A check valve 54 is disposed between the
cavity 22 and the chamber 12 to allow grease to move
only from the chamber 12 into the cavity 22. Another
check valve 59 is disposed between the cavity 22 and
the discharge conduit 24 to alIow grease to move only
from the cavity into the conduit and not vice versa.
In operation, the grease gun 10 may be
assumed to be full of grease as shown in Fig. lA.
;Upward movement of the lever as shown in Fig. 2 moves
the piston 28 upward in the cylinder 26. The pawl 46
30~ on the piston 28 engages the ratchet 34 as shown in
Fig. lB and rotates the rod 48, which moves the
follower 52 towards the head 16, thus forcing grease
in the chamber into the cavity past valve 54. At the
same time, the cylinder 26 fills with grease from the
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cavity. On the downward stroke of the piston, pawl 46
is disengaged from the ratchet, and the piston forces
grease from the cylinder 26 into the cavity 22. The
check valve 54 prevents grease from flowing back into
the chamber 12, while the check valve 56 allows grease
out of the cavity 22 into the discharge conduit 24.
Upon successive strokes of the lever, the chamber is
emptied of grease.
Once the chamber 12 is empty of grease, the
chamber 12 is unthreaded from the head 16, thus
removing the chamber 12, cap 18 and rod 48 from the
head 16, with the rod 48 disengaging from the pin 42.
The rod 48 is moved lengthwise of the chamber until
the follower clears the end of the cartridge 30. The
rod is then moved back towards the head to remove the
cartridge in conventional fashion, and again back
towards the cap to allow a new cartridge to be added.
The chamber is then threaded back onto the head. The
rod is then moved further lengthwise of the chamber
(with its end 50 moving towards the cap 18) until the
;~ ~split nut 56 on the follower 52 engages the shoulder
58 and the split nut 56 is then moved by gentle force
onto the shoulder 58 and opened, as shown in Fig. 3.
This disengages the split nut from the threads on the
rod 48 as the ends of the split nut move over the
shoulder 58. The rod 48 may then~be moved lengthwise
in relation to the cap 18 to the~original position
shown in Fig. 1, wlth the rod énd 50 engaged with the
pin 44 but with the split nut 56 still being in the
30~ open position. The~setting rin~g 20 and therefore the
splines 21~of the~setting ring 20 may then be moved
towards the head untll the splines abut against the
follower 52 and then the follower 52 may be urged
toward~s the~ head 16. This disengages the split nut
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from the shoulder 58, and engages it with the threads
on the rod 48. The setting ring may then be reset. A
few turns of the handle 66 of the rod 48 will bring
the follower down to the cartridge where it will set
in the cartridge to pump grease to restore the grease
gun to the ready position shown in Fig. lA. The
follower cannot force the cartridge out of the chamber
because the head is now on the chamber.
The resulting grease gun may be re-filled
quickly by the quick action of unthreading the
chamber, removing the cartridge, adding a new
cartridge, pulling the rod back, threading the chamber
back on the head with the rod engaging the pin,
splitting the nut, pushing the rod in, resetting the
split nut, and resetting the setting ring.
Alternative Embodiments
A person skilled in the art could make
immaterial modifications to the invention described
~and claimed in this patent without departing from the
essence of the invention.
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