Note: Descriptions are shown in the official language in which they were submitted.
CA 02605218 2007-10-03
BATTERY POWERED GREASE GUN WITH STRAIN
GAUGE BASED PRESSURE TRANSDUCER
CROSS-REFERENCE TO RELATED APPLICATIONS
1001] This application is a Continuation-in-Part of United States Patent
Application serial
number 11/159,502, filed June 23, 2005, which claims the benefit of United
States Provisional
Patent Application, serial number 60/582,686, filed June 24, 2004 the contents
of which are
incorporated in full herein.
FIELD OF THE INVENTION
[002] The present invention relates to powered grease guns and particularly to
portable battery
powered grease guns.
BACKGROUND OF THE INVENTION
[003] Existing portable battery powered grease guns operate by the repeated
compression of a
motor-driven compression mechanism such as a reciprocating plunger moving
through a
compression chamber. Grease compressed by the plunger moving through the
compression
chamber will move through an exit check valve which is biased by a spring to
prevent grease
from exiting the compression chamber at a pressure less than a preselected
preferred pressure.
Grease exiting the compression chamber at sufficient pressure overcomes the
exit check valve
and passes through an outlet port either directly from the grease gun into a
grease zerk on a
machine to be lubricated, or from the outlet port of the grease gun into a
hose which terminates in
a zerk coupler. When no restriction in movement of grease through the outlet
port is encountered,
the grease gun operation is satisfactory. However, if a clogged or otherwise
stubborn grease zerk
is encountered, the operation of the grease gun can create an overpressure
condition within the
grease gun head causing leaks and damage to seal components of the grease gun,
wear on the
grease gun compression mechanism, or possible explosion of the grease gun.
[004] Prior efforts to overcome the problems with overpressure within the
grease gun head when
back pressure in the outlet port is encountered due to a clogged grease zerk
have included a
1
CA 02605218 2007-10-03
battery powered grease gun with relief check valve which allow grease to be
exhausted into the
environment directly from the grease gun head. This apparatus permits grease
to be spilled and to
coat the exterior of the grease gun. A solution to alert a user to pressure of
grease in a grease gun
or grease under excess pressure when an overpressure condition is encountered
is needed.
BRIEF SUMMARY OF THE INVENTION
[005] A battery or powered grease gun is disclosed. In one embodiment, the
grease gun is
provided with a passageway through which grease at elevated pressure may be
retumed to the
source of grease coupled to the grease gun. The grease gun head includes a
small relief
passageway joined to the compression chamber of the grease gun head which is
closed by an
adjustable check valve biased by a spring. When grease at a pressure above a
preselected pressure
is present in the relief passageway, the bias of the check valve is overcome
and grease may pass
from the relief passageway to a return conduit which is joined to the grease
barrel or the grease
supply hose adapter which is mounted to the grease gun head. Grease at excess
pressure within
the compression chamber may therefore be vented back to the grease barrel or
into the adapter
which supplies grease to the grease gun head.
[006] Alternatively, the grease gun head may be additionally provided with a
sampling duct
which is joined to the compression chamber. The sampling duct couples the
compression
chamber to a port in which a pressure gauge may be installed.
[0071 Alternatively, a pressure transducer may be installed in the port.
[008] A grease gun having one or more strain gauge based pressure transducers
is also disclosed.
The pressure transducer in one embodiment comprises a pressure sensor that
measures output
pressure. Altematively, pressure within the gun can be monitored. The grease
gun of this
embodiment uses one or more strain gauges to sense minute expansion and/or
contraction of the
grease gun, and preferably on the surface of the grease gun body or head. The
expansion and/or
contraction permits determination of the pressure in the output chamber or
exit port. The strain
gauge based pressure transducer is placed in operable communication with a
control and/or
display unit to both monitor and control the pressure within and upon the
grease gun.
2
CA 02605218 2007-10-03
[009] The pressure transducer is electrically coupled to an external display
on which the pressure
of grease may be indicated visually. The pressure of grease in various
locations may be
displayed on the pressure gauge.
[0010] It is, therefore, an object of the invention to monitor and/or control
pressure within and
upon the grease gun.
[0011] These and other objects of the invention will be apparent from
examination of the
drawings and the detailed description of the invention which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[001 ] FIG. I is a front elevation of an exemplary battery operated grease
gun.
[002] FIG. 2 is a front elevation of a grease gun head, with cover removed, of
a battery powered
grease gun according to the present invention.
[003] FIG. 3 is a section taken along line 3-3 of FIG. 2.
[004] FIG. 4 is a section taken along line 4-4 of FIG. 2.
[005] FIG. 5 is a transverse cross section of an altemative grease gun head
equipped with an
optional pressure transducer and display.
[006] FIGS. 6A-6D are views of a strain gauge comprising a diaphragm in an
embodiment of the
pressure transducer.
[007] FIG. 7 is an enlarged front elevation of an exemplary display for a
grease gun equipped
with a pressure transducer.
[008] FIG. 8 discloses the battery powered grease gun of FIG. I coupled to a
remote pressurized
grease supply.
[009] FIG. 9 is a cross-sectional, cut away view of an alternative grease gun
equipped with a
strain gauge based pressure transducer.
[0010] FIG. 10 is a view of a strain gauge based pressure transducer fitting.
[0011] FIG. 11 is a cross-sectional view of the strain gauge based pressure
transducer fitting of
FIG. 10 taken along line 11-11 of FIG. 10.
3
CA 02605218 2007-10-03
[0012] FIG. 12 is a flow chart illustrating the monitoring and control of the
grease gun.
[0013] FIG. 13 is a flow chart illustrating the monitoring and control of the
grease gun.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] Referring to FIG. 1, an exemplary portable grease gun 2 is illustrated
which includes a
barrel 4 containing a supply of grease and a grease gun head 6 joined to a
handle 8. A battery 10
is coupled electronically and mechanically to handle 8. The grease gun head 6
is coupled to a
grease conduit 12 such as a flexible hose by fittings 14. An adjusting screw
16 is provided on the
grease gun head 6 to permit a user to adjust the pressure of grease within the
head at which
grease will be bled off to the barrel 4. This adjusting screw may additionally
be fitted with an
external pointer (not shown) to allow the user to set a desired pressure when
aligned with a
calibrated dial on the head. The adjusting screw may alternatively be
adjustable with the use of a
tool such as an allen wrench or a screwdriver, or it may be provided with a
knob which can be
restricted manually. The grease barrel4 may be removed and an adapter for
attachment of a hose
attached in the place of barrel 4. The adapter with attached hose would permit
transfer of grease
from a grease canister or other bulk supply to the grease gun head 6.
[0015] Referring now to FIGS. 2-4, the internal mechanics within grease gun
head 6 are
schematically illustrated. An eccentrically mounted cam disk 20 is driven in
rotation by a drive
shaft 22 which is rotated by a battery powered motor which is not shown in
this figure but which
is housed within handle 8 of grease gun 2 as seen in FIG. 1. As cam disk 20
rotates, plunger 24
reciprocates along passageway 26. Grease entering passageway 26 from inlet
port 18 is forced
along passageway 26 by plunger 24 until it enters compression chamber 28
wherein the pressure
of grease therein is raised by the thrusting movement of plunger 24. Once at
sufficient pressure to
overcome the bias of outlet check valve 30, grease passes into grease exit
port 32 and may exit
port 32 into a hose or other conduit such as grease conduit 12 seen in FIG. 1.
Plunger 24 is urged
away from compression chamber 28 by main return spring 34 which is disposed in
enlarged bore
35.
[00161 An elongate axial bore 46 extends partway through plunger 24 from the
head 48 thereof
such that cross bore 62 of plunger 24 intercepts axial bore 46 and will
communicate with inlet 18
4
CA 02605218 2007-10-03
so that grease at inlet 18 may move along and within plunger 24 to provide
lubrication of cam
disk 20 as it engages head 48 of plunger 24.
[0017] Grease enters passageway 26 from inlet port 18 which is communicative
with the interior
of grease barrel 4, which contains a source of grease under slightly elevated
pressure. As plunger
24 is urged toward check valve 30 by cam disk 20, grease is forced from inlet
port 18 into
compression chamber 28 and urges check valve 30 to be displaced, allowing
grease at sufficient
working pressure to flow past check valve 30 and into exit port 32. A cap
screw 36 holds check
valve spring 38 in place to urge ball 40 against seat 37.
[0018] Typically, exit port 32 will be coupled to a conduit 12 (see FIG. 1) to
assist in delivery of
grease distant from the grease gun. Should grease not flow freely through exit
port 32, due, for
example, to resistance of a plugged zerk to accept grease, the reciprocating
action of plunger 24
will cause pressure of grease in the compression chamber 28 and in exit port
32 to rise above the
working pressure. Once the grease pressure in compression chamber 28 reaches a
predetermined
level, in one embodiment, grease may be vented from exit port 32 back into the
barrel 4 through
a relief passageway 50 best seen in FIG. 4.
[0019] It may be observed in FIG. 4 that head 6 includes barrel receiver 42
which is a connection
point for a grease barrel 4. Barrel receiver 42 is typically internally
threaded so that the open end
of barrel 4 may be threaded into barrel receiver 42. In this embodiment, a
relief passageway 50 is
communicative with barrel receiver 42 and with a collection chamber 44
containing relief check
valve 52. Relief passageway 50 is of substantially smaller cross section than
exit port 32.
Adjusting screw 16 is received in threaded bore 54 and may be adjusted to vary
the force needed
to overcome relief check valve 52. When pressure of grease in exit port 32
exceeds a
predetennined level controlled by the adjustment of adjusting screw 16, relief
check valve 52 is
deflected from its seat and grease may leave exit port 32 and pass along
relief conduit 56 past
relief check valve 52 and into relief passageway 50 which allows the grease to
return to the
supply within barrel4. The bias provided by relief check spring 53 is greater
than that of check
valve spring 38 so that grease will not pass relief check valve 52 unless
check valve 30 is open.
[0020] A pressure gauge may be installed in gauge port 58 to measure the
pressure of grease in
exit port 32. A small sampling duct 60 interconnects exit port 32 and gauge
port 58. Sampling
CA 02605218 2007-10-03
duct 60, like relief conduit 56, is much smaller in cross section than exit
port 32. Grease under
pressure may pass along sampling duct 60 to be urged against a diaphragm of a
pressure gauge
which may be installed in gauge port 58. As an alternative to a gauge mounted
in gauge port 58, a
hose may be coupled to gauge port 58 to convey the grease pressure in sampling
duct 60 to a
remote measuring device.
[0021] In FIG. 5, an alternative embodiment of the grease gun head 6 is
illustrated. In this
alternate embodiment, grease gun head 6 is provided with a pressure transducer
64 fitted into
gauge port 58 and communicative with sampling duct 60 such that pressure of
grease in exit port
32 is sampled and may be detected by pressure transducer 64.
[0022] In the altemative embodiment of the transducer 64, the transducer may
comprise an inlet
opening 61. No outlet would be provided. As shown in FIGS. 6A-6D the
transducer 64 further
comprises a diaphragm 65 that may be deformed as a result of the application
of pressure by
grease within the inlet opening 61. In this embodiment, one or more strain
gauges 82, 84 may be
attached or bonded to the diaphragm 65 via means commonly available in the
art. Additionally,
fixed resistors 85 may also be applied. Likewise, a movable block 67 may be
provided in
association with the diaphragm 65 opposite the side exposed to the application
of pressure and
may include one or more fixed points 69. The strain gauges 82, 84 on the
diaphragm 65 detect
minute deflections of the diaphragm 65 as grease pressure is applied.
[0023] Signals from a pressure transducer 64 may be transmitted along wiring
68 to display 66 at
which the sensed pressure in exit port 32 or gauge port 58 may be visually
displayed exterior to
the grease gun head 6. The display 66 may be attached to the grease gun at any
location, may be
attached to a separate device, or may be a stand alone display device.
[0024] As is known, a pressure transducer 64 is a transducer that converts
pressure into an
analog electrical signal. There are various types of pressure transducers
available with a variety
of electrical outputs and in a variety of styles, any of which may be
contemplated for use with the
grease gun, based upon user and/or manufacturer preference. While specific
embodiments are
disclosed herein, it is understood that alternate types of pressure
transducers may be used with
the embodiments of the grease gun disclosed. The conversion of pressure into
an electrical
signal is achieved by the physical deformation of strain gauges which are
bonded in a particular
6
CA 02605218 2007-10-03
location. For example, in one embodiment, described above, the strain gauges
82, 84 may be
bonded to a diaphragm 65 connected to the pressure transducer 64 and wired,
for example, into a
wheatstone bridge configuration. The pressure applied produces a deflection of
the diaphragm
65 which introduces strain to the gauges 82, 84. The strain produces an
electrical resistance
charge proportional to the pressure. Namely, pressure is applied to the strain
gauge 82, 84, the
strain gauge element wires increase in length and decrease in diameter,
thereby increasing the
resistance to flow of current through the wires of the wheatstone bridge.
Strain gauge elements
82, 84 may be combined, so that while some strain gauge elements may stretch,
others may
simultaneously compress, exaggerating the signal.
[0025] Pressure transducers are available from Measurement Specialties, Inc.
of Hampton,
Virginia under product numbers MSP300 and MSP340 which may be acceptable for
use in an
embodiment of the pressure transducer 64 described herein having a diaphragm
65 attached
thereto. Preferably, the pressure transducer 64 comprises a stainless steel
transducer having a
solid piece of uniform construction. The pressure transducer 64 may be
threaded thereby
allowing the threaded insertion into a mating port on a grease gun. The
diaphragm 65 may
comprise a stainless steel diaphragm to which strain gauges 82, 84 may be
fused with, for
example, high temperature glass. The pressure transducer 64 may comprise a
range of from 0 -
10,000 or 15,000 PSI or 0 to 700 or 1,000 BAR, may provide millivolt or
amplified outputs, and
may operate under wide temperature ranges. In addition, the sensors of the
device may be
hermetically sealed.
[0026] FIG. 7 discloses an exemplary display 66 which includes an LCD array 70
or similar
display panel on which the pressure within grease gun head 6 may be displayed.
[0027] Display 66 may include a controller to convert the raw pressure data
from the pressure
transducer 64 into a numeric output on LCD array70. Warning lamps 72, 74 may
be provided on
display 66 to alert the user of an overpressure condition or other malfunction
of the grease gun,
signals for which would be generated by a preset entry in the controller of
display 66. The LEDs
may be used in place of the LCD array 70 in an alternate configuration. An
intermediate
controller for LCD array 70 is not illustrated but is well known in the
display controller art.
7
CA 02605218 2007-10-03
[0028] FIG. 8 discloses an embodiment of the battery powered grease gun head 6
coupled to an
adapter 76 coupled to a hose 78 coupled to a pressurized grease supply
reservoir 80. Grease
within supply reservoir 80 may pass under slightly elevated pressure along
hose 78 to adapter 76
which is received in barrel receiver 42 in place of a grease barrel. If grease
is prevented from
exiting grease conduit 12, the internal pressure of grease in grease gun head
6 will rise as the
motor driving the plunger 24 operates. Grease within the exit port 32 (see
FIG. 3), when pressure
thereof substantially exceeds working pressure, may be vented into adapter 76
through relief
passageway 50 (see FIG. 3). The pressure at which grease is vented to adapter
76 is selected by
adjustment of adjusting screw 16.
[0029] In addition to, or as an altemative to, the relief passageway and
sampling duct systems
described hereinabove, FIG. 9 discloses an embodiment of the battery powered
grease gun with
head 6 having one or more strain gauge based pressure transducers 64, 82, 84.
In basic terms,
the pressure transducer 64, or strain gauges 82 or 84 comprise a pressure
sensor that measures
output pressure. The grease gun of this embodiment uses one or more strain
gauges 82 or 84 to
sense minute expansion and/or contraction of the grease gun, and preferably on
the surface of the
grease gun body or head 6. The expansion and/or contraction is proportional to
the pressure in
the output chamber 86, the exit port 32 or other designated portion of the
grease gun. In a
preferred embodiment, a separate output chamber 86 may be provided which may
be threaded
into or integral with the grease gun head 6. The output chamber 86 comprises
one or more strain
gauges 84 operably attached thereto. The strain gauges may be fastened or
bonded to the output
chamber 86 by means commonly available in the art. Alternatively, strain gauge
sensors 82 may
be fastened or bonded, by means commonly available in the art, to the surface
of the cylinder or
grease gun head 6 through which grease is passed during operation. In one
embodiment, a strain
gauge may be provided as portion of a fitting that is threaded into the grease
gun at a tee at the
output from the grease gun, or may alternatively be threaded directly into the
grease gun body at
a port connected to the output pressure (see FIGS. 9 and 10).
[0030] As can be seen from FIG. 9, the grease gun head 6 comprises an output
chamber 86. The
output chamber 86 has at least one strain gauge 84 attached thereto.
Preferably, more than one
strain gauge 84 is operably attached. The output chamber 86 is integrally
attached or threaded
into the grease gun head 6 at or near the check valve 30 and exit port 32.
During operation, the
8
CA 02605218 2007-10-03
movement of the check valve 30, as set forth hereinabove, allows a flow of
grease into the output
chamber 86. The flow of grease into the output chamber 86, as it increases,
causes the chamber
to expand slightly which expansion is monitored or detected by the strain
gauge(s) 84 positioned
on the output chamber 86. Conversely, the loss of pressure and/or contraction
of the output
chamber 86 may be sensed by the strain gauge(s) 84. The pressure sensed by the
strain gauge is
communicated to the control and/or display 66 of the grease gun via the
pressure transducer and
associated wiring as described herein.
[0031] In addition, or as an alternative to the positioning of the strain
gauge(s) on the output
chamber 86, one or more strain gauge(s) 82 may be positioned on the grease gun
body 6 at or
near the pressure or compression chamber 28. Attachment to the grease gun is
the same as
described above. As a result of this position, this strain gauge(s) 82 will
sense the pressure of
grease within the chamber 28 by the expansion and/or contraction of the grease
gun at this
location and communicate the variable to the system.
[0032] While specific locations of attachments of the strain gauge(s) are
described hereinabove,
the locations are disclosed for purposes of example only, and one of skill in
the art would
understand that any location on or around the grease gun upon which the
pressure, and in
particular the expansion and contraction of the particular component, could be
sensed would be
acceptable for the purposes provided.
[0033] The strain gauges 82, 84 are attached integrally or via means commonly
available in the
art to the grease gun. The strain gauges are further attached, via wiring 68,
and if necessary,
through a microprocessor, to an LCD array 70 or like display which displays
the pressure sensed
by the strain gauges 82, 84.
[0034] In further detail, preferably, the pressure transducer 64 uses one or
more strain gauges 82
or 84 to sense pressure. The transducer 64 sends a signal to a module 66. The
module 66
displays a pressure reading calculated based upon the signal received from the
transducer. As a
result, the pressure is sensed and displayed on display 66 for the operator of
the grease gun. In
this manner, the user can monitor the pressure of or the grease gun can use
that reading for
control of the gun.
9
CA 02605218 2007-10-03
[0035] FIGS. 10 and 11 discloses an embodiment of the strain gauge based
pressure transducer
used in a preferred embodiment. Specifically, FIG. 10 illustrates a strain
gauge fitting 88
comprising one or more connection areas 90 and a strain gauge area 92. Within
the strain gauge
fitting is a conduit 91 for the passage or receipt of grease or other flowable
substance. An outer
surface 93 surrounds the conduit 91 and the strain gauge(s) 94 and may include
the connection
portions 90 thereon. The strain gauge fitting 88 preferably comprises a
stainless steel material
and may have a threaded end at one or more connection areas 90 for threading
into a receiving
port on a grease gun. While stainless steel is specifically claimed, other
materials suitable for
grease guns would be acceptable for the purpose provided. At least one, but
preferably two strain
gauge coupons 94 may be attached to the strain gauge fitting 88, preferably in
the strain gauge
area 92. As shown in FIGS. 10 and 11, two strain gauge coupons are attached or
are positioned
along a portion of the strain gauge fitting 88, applied 180 apart. The strain
gauge coupons 94
are wired as a full bridge having four flying leads, and further include a
heat shrink wrapper
thereon. The strain gauges of the preferred embodiment are preferably 350 ohm,
open-faced
gauge coupons 94 having a brushed-on coating. An encapsulated 90 tee rosette
strain gauge,
such as is available from Vishay Micro-Measurements in Raleigh, North
Carolina, comprising a
resistance of 350 ohms 0.4 % (product no. J2A-XX-S114L-350) to 1000 ohms
0.4% (product
no. J2A-XX-S152M-lOC) may be used for the strain gauge coupons 94 (or 82, 84)
of the
embodiment disclosed. However, other strain gauges may be acceptable for the
purposes
provided.
[0036] Referring to FIGS. 12 and 13, in addition to the system for sensing
pressure described
above, a system may also be provided for measuring flow from the gun 2 by, for
example, timing
pump operation or via a more complex mechanism. Flow rate and/or total
displacement may be
determined by a microprocessor 96 in communication with the mechanism for
measuring flow.
Preferably, a displacement sensing device 98 or mechanism, as shown in FIG. 8,
may be used.
Displacement devices are well known and any such device may be installed and
used with this
grease gun of the embodiment described. The displacement sensor 98 may be a
dedicated device,
or may be combined with, for example, the strain gauge based pressure
transducer 64, 82, 84. In
one instance, a non-contact switch may be provided as a displacement sensing
device 98 in
association with the grease gun to count cycles of the plunger 24 or piston
during operation.
CA 02605218 2007-10-03
Each cycle of the plunger 24 represents a known displacement of grease.
Therefore, the number
of cycles of the plunger 24 can be used by the microprocessor, using an
algorithm, to calculate
and display a quantity of grease. Alternatively, an encoder mounted to the
pump drive motor
may be used as a displacement sensing device 98 to determine flow. This system
could be used
in conjunction with an algorithm utilized by the microprocessor 96 to
intelligently compensate
flow measurement with current pressure for accuracy. The display 66 of a
preferred
embodiment, therefore, may display a pressure, as well as a volume of flow of
grease through the
grease gun 2. Specifically, the display 66 comprises an electronic display
(such as described
herein above) that reports output pressure, flow rate, and/or flow
totalization individually, or in
any combination thereof. As a result, the operator is advised of and can
monitor the passing of
grease through the grease gun, the volume of grease, and the amount of back-
pressure or build-up
that has developed in the grease gun.
[0037] In association with the foregoing, the user may reset a volume, via a
reset control. The
display 66 may include user-resettable totalizers. A non-reset display and at
least one, but
preferably two or more reset volume displays may also be provided on the
grease gun.
Moreover, a user input control 100 may be provided on the grease gun 2 along
any portion
thereof, or may be provided as a separate component. The electronic control
system 100 may
include a communication interface for any one of, or combination of,
monitoring and control of
grease gun operation, calibration, service, malfunction diagnostics,
communication with plant
systems for process control and/or validation (including, for example, a plant
system that records
grease pressure delivered on an assembly line to set maximum pressure based on
current
application), and monitoring gtease gun usage to determine service intervals
for routine
maintenance. The communication may further, optionally, include a
communication interface to
additional electronics, such as a USB device, CAN device, or similar system.
This user input
control 100 may be used, for example, to set a maximum output pressure or any
of the conditions
necessary for operation of the grease gun. Preferably, an electronic control
system 100 is
provided that stops the flow through the grease gun when certain variables are
reached, such as
when a user-defined pressure is achieved or when the gun's maximum pressure is
reached.
[0038] The foregoing description of the invention has been presented for
purposes of illustration
and description and is not intended to be exhaustive or to limit the invention
to the precise form
11
CA 02605218 2007-10-03
disclosed. Modifications and variations of the embodiments are possible in
light of the above
disclosure or such may be acquired through practice of the invention. The
embodiments
illustrated were chosen in order to explain the principles of the invention
and its practical
application to enable one skilled in the art to utilize the invention in
various embodiments and
with various modifications as are suited to the particular use contemplated.
It is intended that the
scope of the invention be defined by the claims appended hereto, and by their
equivalents.
12
