Note: Descriptions are shown in the official language in which they were submitted.
' ' ' CA 02305996 2006-03-O1
CONTROL SYSTEM FOR JACK FOR A SNOW PLOW
BACKGROUND OF THE INVENTION
Conventional snow blade mounts for four wheel drive vehicles such as pick-up
trucks can weigh several hundred pounds, and generally include a chassis frame
that can
be permanently fixed to the vehicle chassis, usually behind the vehicle front
bumper. A
lift frame is then removably coupled to the chassis frame, and the snow blade
is then
coupled to the front end of the assembly via an A-frame and trip frame
assembly. The A-
frame with the snow blade attached is typically removable from the vehicle.
Conventionally, the lift frame has been permanently mounted to the chassis
frame (and
therefore not readily removable from the vehicle), and the hydraulic pump used
to
operate the snow blade was located under the vehicle hood, and were driven
using a belt
drive driven by the vehicle engine. However, safety considerations now often
dictate that
the lift frame be removed when the plow is not in use.
One drawback of conventional snow blade mounts is the difficulty in readily
attaching and removing the lift frame assemblies from the vehicle chassis,
especially in
view of their weight. To that end, U.S. Patent No. 5,125,174 discloses a
removable
snowplow including a removable lift frame and A-frame combination. However,
the lift
frame assembly is permanently
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CA 02305996 2000-04-18
mounted to the A-frame, thus requiring removal of both
simultaneously, as a unit. U.S. Patent No. 5,353,530 is of a
similar vein.
Conventional mounting systems utilize a. pin arrangement,
whereby the vehicle and mount assembly must be properly aligned
prior to coupling the mount to the chassis with a pair of pins.
This mounting and dismounting is difficult and tedious.
It is therefore an object of the present invention to provide
a snow blade mount and lift assembly for a vehicle that is easily
attachable and removable from the vehicle.
It is a further object of the present invention to provide a
control system for a jack for lifting the assembly for proper
vertical alignment with the vehicle chassis mount receiving unit.
SUMMARY OF THE INVENTION
The problems of the prior art have been overcome by the
present invention, which provides a control system for a jack for
a mount and lift assembly for snow blades or other accessories. A
plow assembly and lift frame are removably coupled to a mounting
frame attached to the bottom of the vehicle chassis. The jack
enables proper positioning of the lift frame relative to the
vehicle chassis for easy mounting and dismounting thereto. The
control system operates the jack in conjunction with the snow plow
blade, and prevents the jack from being in its deployed position
during operation of the blade.
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CA 02305996 2000-04-18
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective exploded view of an exemplary snow
blade mounting system that can be used in accordance with the
present invention;
Figure 2 is a cross-sectional view of one embodiment of the
jack assembly in accordance with the present invention;
Figure 3 is a side view of a second embodiment of the jack
assembly in accordance with the present invention;
Figure 4 is a side view of a third embodiment of the jack
assembly in accordance with the present invention;
Figure 5A is a side view of a fourth embodiment of the jack
assembly in accordance with the present invention, shown in a
raised position;
Figure 5B is a side view of a fourth embodiment of the jack
assembly in accordance with the present invention, shown in a
lowered or deployed position;
Figure 6 is a side view of a fifth embodiment of the jack
assembly in accordance with the present invention;
Figure 7 is a side view of a sixth embodiment of the j ack ,
assembly in accordance with the present invention;
Figure 8 is a diagram of the circuitry of the control system
of the present invention;
Figure 9 is a schematic of the hydraulics of the control
system of the present invention;
Figure 10A is a top view of the lift frame assembly showing
the safety pin engaging the safety switch in accordance with one
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CA 02305996 2000-04-18
embodiment of the present invention; and
Figure 10B is a top view of the lift frame assembly showing
the safety pin disengaged from the safety switch in accordance with
one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Turning first to Figure 1, there is shown generally at 10 a
snow blade lift and hitch assembly that is suitable for use in the
present invention. Those skilled in the art will appreciate that
the assembly shown is for purposes of illustration, and that the
invention is not limited to any particular lift and hitch assembly
design. For example, although the illustrative embodiment includes
the use of an A-frame, T-frames or other designs could be used.
Vehicle mounted receiver frame 11 attaches to the vehicle the
chassis frame (not shown) behind the front bumper by means of pins
or bolts (not shown). Any suitable means can be used to secure the
receiver plate 11 to the chassis, such as bolting. The actual
design of the receiver plate 11 interface for attachment to the
chassis will depend upon the identity (and thus design) of the
particular chassis, and is well within the skill in the art.
The receiver plate 11 preferably remains permanently mounted
to the vehicle chassis, regardless of whether the snow blade or
other accessories are in use. Its main purpose is to provide a
means of attachment of the follow-on components, such as those that
provide the lift and angle of the snow blade where the follow-on
component is a snow blade, and to absorb and transfer any shock
4
' ' CA 02305996 2006-03-O1
loads imposed on the snow blade (or other accessory) into the vehicle chassis.
A receiver arrangement is created for the removable lift frame 10 and A-frame
30
integral therewith, or for any other accessory to be attached to the vehicle
via the receiver
plate 11. A pair of spaced side guides 40, 41 extend vertically downward from
the frame
11, and then inward toward each other as shown. Two spaced discontinuous male
portions 215a and 215b tapering towards each other extend from the lift
assembly 10 as
shown. Each male portion 215a' and 215b' is configured to be received by the
corresponding spaced female guide members 40, 41 of the receiver 11.
Alternatively, the
male portions could be located on the receiver 11, and the female portions on
the lift
assembly 10.
Tubular lift frame 10 and A-frame 30 assembly is adapted to be releasably
coupled to the receiver frame 11. The following description of the lift frame
10 and A-
frame 30 is similar to that disclosed in co-pending U.S. Serial No.
08/640,145, now U.S.
Patent No. 5,815,956, although those skilled in the art will appreciate that
the present
invention is not limited to that particular lift frame and A-frame design. The
lift frame 10
as shown has a generally rectangular shape, although the present invention is
not to be so
limited. A transverse vertical actuator support tube 50 is coupled to the
frame 10
between side gusset plates 54, 55, and includes a central bracket 51 for
attachment of one
end of a vertical lifting means 52 such as a hydraulically driven actuator or
cylinder. The
opposite end of
CA 02305996 2000-04-18
the vertical lifting means 52 is coupled to pivot hood 53, which in
turn is pivotally mounted to the underside of top cross bar 45 of
the frame 10 as shown. The pivot hood 53 has means to which one
operative end of a linking means such as a chain 110 or the like
can be mounted. The other operative end of the linking means is
mounted by any suitable means to an angle iron coupled to the snow
plow blade, so that actuation of the vertical lifting means 52
causes a corresponding vertical lift of the hood 53, which thereby
lifts the snow plow blade.
Side gussets 54, 55 are shown coupled to vertical legs 46, 46'
of the lift frame 10, such as by welding, and will be discussed in
greater detail below. Triangular light mounts 56, 57 are provided
on the frame 10 to support additional lighting or the like. Fixed
to inside edges of the legs 46, 46' of the lift frame 10 are
opposite right angle A-frame limit stops 98, 99 (only 99 shown)
positioned to prevent the A-frame 30 from lifting too high.
A compartment in the A-frame 30 is defined by a top plate 60
and an opposite, substantially co-extensive and spaced parallel
bottom plate 61. A stabilizer 36 comprising a formed C-channel is
mounted on the top surface of the A-frame and mates to a stabilizer
1/2 ring 77 attached to the trip frame 70. The stabilizer 36
contains and stabilizes the 1/2 ring 77, thus stabilizing the trip
frame to which the 1/2 ring 77 is attached. Those skilled in the
art will appreciate that the stabilizer 36 can be designed having
shapes other shapes than that shown, as long as it properly
stabilizes the trip frame assembly 70.
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CA 02305996 2000-04-18
Located in the body of the A-frame substantially between top
and bottom surfaces 60, 61 is an actuator drive cavity. Locating
the actuator drive means (preferably an electric/hydraulic pump
assembly) substantially within the body of the A-frame 30 lightens
the lift frame 10 (where the pump was conventionally located) for
easy removal. Instead, the dead weight of the actuator drive means
is advantageously added to the blade, assisting in creating a
cleaner snowplow pass. Importantly, the actuator drive means in
this location in no way obstructs the radiator of the vehicle,
thereby allowing proper air flow to cool the vehicle engine and
help prevent overheating. In addition, the actuator drive means is
well sheltered, minimizing potential damage as the vehicle
approaches the blade assembly for mounting. It also allows for
shorter hydraulic lines to the angle pistons, and allows for more
clearance in the basic geometry, thereby allowing higher blade
motion for stacking snow. Preferably, the bulk of the actuator
drive means is located substantially in the horizontal plane of the
A-frame defined by the top and bottom surfaces 60, 61. Most
preferably, a lower recess/skid plate coupled to the underside of
plate 61 supports the pump assembly slightly below the plane of
plate 61 of the A-frame 30, thereby maximizing the lift height of
the A-frame 30. A removable top cover optionally having a
hydraulic fluid reservoir fill cap 68 provides further protection
for the pump assembly.
Trip frame assembly 70 is the preferred means for attaching
the snow blade to the A-frame 30. The trip frame 70 allows the
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CA 02305996 2000-04-18
blade to pivot forward, which allows it to trip over obstacles and
absorb shock that would otherwise be transferred into the plow
frame assembly and vehicle, which in extreme cases would cause
substantial damage. The front of the trip frame 70 is defined by
a trip frame angle pivot, which comprises a top horizontal plate 96
and a spaced, parallel, co-extensive bottom horizontal plate 97.
Angled plates 90, 91 receive the apex of the A-frame and provide a
stop. The A-frame is pivotally mounted through axially aligned
hole 92 in horizontal plates 96, 97. The trip frame angle pivot
includes four horizontal axially aligned pivot bushings 70a-70d
each mounted on a rib 83 intersecting horizontal top and bottom
plates 96, 97. The pivot bushings 70a-70d each mate to a recess
formed in the back of the plow blade. Welded at extreme opposite
ends of trip frame 70 are right angle blade trip stops 73, 74.
These provide an angled stop against the vertical blade rib of
blade. Were the blade allowed to trip forward all the way to the
ground, it could become lodged or could spring board up very
abruptly, causing damage. In addition, the lower stop keeps the
spring extension within its designed operating range which prevents
the springs from stretching (overstretching of the springs
permanently damages the springs, making them unable to return the
blade to its full upright position).
Those skilled in the art will recognize that the foregoing
trip frame assembly is not required; the snow blade can articulate
directly from the A-frame and by directly coupled thereto via
pistons and pivots. Other trip frame designs could also be used.
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CA 02305996 2000-04-18
Welded on the top cross bar 96 is the 1/2 ring 77 mentioned
above, which stabilizes the trip assembly and pivot. A right angle
cross bar 85 is positioned within the 1/2 ring 77, and supports a
plurality of trip return springs means 84a-84n (three shown). The
opposite ends of the return springs means 84 are coupled to the
snow blade through an upper spring mount on the rear of the blade.
A pair of spaced horizontal actuators such as cylinders 86, 87
are each mounted at one end between top and bottom horizontal
plates 96, 97. The opposite ends of each horizontal actuator 86,
87 are pivotally coupled to the A-frame at shoulders 80, 80', 81,
81' (81' not shown). These horizontal actuators 86, 87 are
operatively connected to the actuator drive assembly (not shown)
housed in the A-frame 30 cavity by suitable hosing.
The snow blade can be conventional in,design. The preferred
blade is a sheet of steel bumped or rolled to a semi-round shape
and then braced on the backside with a plurality of vertical ribs
and horizontal members comprised of formed stiffeners and a frog
angle at the very base to absorb shock. C-shaped shoe mounts
coupled to the back of the plow blade provide a surface for the
blade to ride on.
Receiver frame 11, preferably made of 3/8" mild steel, is
coupled to the vehicle chassis by suitable means. The front plow
engaging end of the receiver plate 11 includes a round elongated
bar or rod 200, preferably solid and at least about 1" in diameter,
secured to the receiver frame by suitable means such as welding.
In the embodiment shown, the bar 200 extends horizontally a
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CA 02305996 2000-04-18
distance sufficient to be engaged at or near its opposite ends by
a pair of opposite latch hooks 220 discussed in detail below.
However, those skilled in the art will appreciate that the bar 200
need not be continuous; two separate bars could be used at each end
of the receiver frame 11, as long as they are appropriately
positioned for engagement by the latch hooks 220. Receiver frame
11 includes generally longitudinally extending (in the direction
from the vehicle front to the vehicle rear) guide members 40, 41 as
discussed above, which help ensure proper alignment of the lift
assembly 10. The spacing or volume between these guide members and
the top of receiver frame 11 is configured to accommodate the male
ends 215a, 215b of the hitch assembly coupled to the lift frame 10
via the side gussets 54, 55. Thus the male ends 215a, 215b are
preferably tapered as shown, and can include rounded corners to
facilitate hitch engagement. Stated differently, the male ends
215a, 215b are each tapered such that the length of its free
engaging end is shorter than the length of its opposite end coupled
to the lift assembly. Similarly, guide members 40, 41 are
configured and placed such that the receiver volume is tapered,
with its end farthest from the vehicle front being shorter than the
end at the bar 200. The guide members 40, 41 thus act as a track
for receiving and aligning male ends 215a, 215b.
Pivotally coupled to each side gusset 54, 55 via pivot shaft
219 are respective latches 220. Preferably the latches 220 share
a common pivot shaft, the pivot shaft extending from one latch to
the other so that movement of the two latches is coordinated;
CA 02305996 2000-04-18
actuation of one latch results in a corresponding movement of the
other latch. In this way, the movement of the latches can be
controlled by a single lever 221 coupled to one of the latches 220.
Alternatively, separate pivot pins could be used for each latch
220, with each latch having separate means for actuation.
Each latch 200 has a hook shape including an arcuate recess
225 corresponding in angle to the circumference of the bar 200.
The latch is thereby adapted to receive the bar 200. Preferably
the tip 228 of the hook extends beyond the body of the latch. This
design facilitates the grasping and interlocking of bar 200 of
receiver frame 11. Preferably the latches 220 are positioned such
that the arcuate recess 225 is open to (i.e., faces) the bar 200 of
receiver plate 11 when in the unattached position. Each latch 220
includes a lower sloped portion 227 that serves to guide bar 200
into the arcuate recess 225, and an opposite hook 228 that helps
engage the bar 200 once guided into arcuate recess 225.
This positioning of latches 220 relative to bar 200 allows for
the automatic or semi-automatic mounting of the lift frame 10 to
the vehicle. Once the height of the lift frame 10 relative to the
bar 200 is appropriately positioned (which is preferably
accomplished by proper movement of the jack as discussed above),
the vehicle to which the receiver plate 11 is attached is simply
driven towards the lift frame 10 until the latches 220 engage the
bar 200. Due to the configuration of the slope portion 227, hook
portion 228 and arcuate recess 225, the force of the bar 200
engaging the latches 220 cause the latches 220 to rotate counter-
11
CA 02305996 2000-04-18
clockwise and lock the bar 200 in place. Suitable locking pins
(not shown) or other safety locking mechanism can be used to ensure
that the lift frame 10 does not prematurely disengage from the
vehicle. One suitable locking assembly includes a spring loaded
pin assembly, with spring biasing against the pin. In the locked
position, the spring forces the pin through an appropriately
dimensioned aperture in side gusset 54, thereby fixing the latch
220 in place. A lever prevents the pin from retracting out of the
aperture in the gusset 54. In the unlocked position, the pin is
retracted from the aperture, allowing movement of the latch for
engagement or disengagement of the hitch. Each latch 200 can have
a safety lock, or preferably a single safety lock can be used,
preferably in conjunction with the latch that is located on the
same side of the apparatus as lever 221, for operator convenience.
Those skilled in the art will appreciate that the latches 220
(i.e., the engaging means) could be located on the receiver plate
11, and the bar 200 (i.e., the engaged means) on the lift assembly
10. Thus, the receiver 11 and the lift assembly 10 cooperate to
create a releasable coupling of the two.
Turning now to Figure 2, one embodiment of the jack assembly
is shown. The jack is preferably power operated with drive means
such as by a hydraulic cylinder 300 positioned in the cavity of the
A-frame as shown, or with a screw jack (e. g., electric or manual)
similarly positioned. The cylinder 300 is located in the body of
the A-frame substantially between top and bottom surfaces 60, 61 in
the actuator drive cavity, forward (away from the vehicle) of where
12
' , CA 02305996 2000-04-18
the snow blade hydraulic assembly is located. Locating this jack
drive means substantially within the body of the A-frame 30
lightens the lift frame 20 (where the pump was conventionally
located) for easy removal. Instead, the dead weight of the jack
drive means is advantageously added to the blade, assisting in
creating a cleaner snowplow pass. Importantly, the jack drive
means in this location in no way obstructs the radiator of the
vehicle, thereby allowing proper air flow to cool the vehicle
engine and help prevent overheating. In addition, the jack drive
means is well sheltered, minimizing potential damage as the vehicle
approaches the blade assembly for mounting. Preferably, the bulk
of the jack drive means is located substantially in the horizontal
plane of the A-frame defined by the top and bottom surfaces 60, 61.
Jack foot 310 is rigid so as to support the weight of the item
being lifted and lowered, and is preferably made of steel. The
jack foot 310, which preferably includes a curved skid shoe portion
311 for contacting the ground (or other substrate) and a relatively
straight elongated portion 312, is coupled to tab 319, such as by
welding, at about a 45° angle. This assembly is pivotally coupled
to the A-frame assembly via pin 315 through opposite side gussets
317 (one shown) The jack shoe 311 is lowered by actuation of the
hydraulic cylinder 300, which contacts the tab 319 and causes
counter-clockwise rotational movement of the tab 319 about the axis
of the pin 315. A return spring 325 biases against the cylinder
300 such that the jack 310 can be raised by retraction of the
cylinder 300, this time by clockwise rotational movement of the tab
13
' CA 02305996 2000-04-18
319 about the axis of the pin 315. An adjusting nut 327 is used to
provide the proper tension on spring 325. Alternatively, the
spring 325 can be eliminated by using a multi-stage hydraulic
cylinder, which is coupled to the jack by any .suitable means to
raise and lower the same. By lowering the jack 310, the jack shoe
11 engages the ground (or other substrate), supports the lift
assembly, and raises the lift assembly to the appropriate height
for engagement with the hitch assembly mounted on the vehicle.
This design allows for raising or lowering of the jack to virtually
any extent within its raised (i.e., stowed in a position where the
jack will not interfere with the operation of the snow plow or
other utilitarian accessory, such as a position parallel or
substantially parallel to the A-frame) and lowered (i.e., as shown
in Figure 2) range, in contrast to the prior art which allowed for
only incremental lowering or raising (such as in half inch or one
inch increments). This non-incremental, infinite height adjustment
greatly facilitates the mounting operation, especially where the
height of the vehicle relative to the lift assembly has changed,
such as due to snow accumulation on the ground.
Figure 3 shows an alternative embodiment of the jack assembly.
Jack drive means 300, such as a screw jack or more preferably a
multistage hydraulic cylinder, is fixed to the jock bet~.~een jacr
shoe 311 and pivot pin 315, preferably about midway therebetween,
at 400 such as with a pin 401, preferably at about a 45° angle
thereto.,The jack 310 is pivotally connected to the A-frame.30 at
pin 315, allowing the jack 310 to move between a retracted position
14
CA 02305996 2000-04-18
parallel or substantially parallel to the A-frame as shown in the
Figure, to a ground-engaging position (not shown), wherein the
relatively straight elongated portion 312 of the jack 310 can be
approximately perpendicular to the ground but is preferably about
45° to the ground. '
Figure 4 shows another alternative embodiment of the jack
assembly. Jack drive means 300, such as a screw jack (e. g.,
electric or manual screw) or more preferably a single stage
hydraulic cylinder, is fixed to the jack such as with a pin 401,
preferably at about a 45° angle thereto. The jack 300 has an A-
frame engaging end 500 and a spaced foot 311 for engaging the
ground (or other substrate). Preferably the jack drive means 300
is fixed to the jack about midway between end 500 and foot 311.
The jack 310 is movably connected to the A-frame 30 at pin 315,
allowing the jack 310 to slide in the track or retaining guide
created by slotted bracket 510 and move between a retracted
position parallel or substantially parallel to the A-frame, and a
ground-engaging position as shown in Figure 4, wherein the
relatively straight elongated portion 312 of the jack 310 can be
approximately perpendicular to the ground but is preferably about
45° to the ground.
Figures 5A and 5B show another alternative embodiment of the
jack assembly. In this embodiment, a chain 110 or the like, which
is generally coupled to attachment 38 for raising and lowering the
plow, is disconnected from attachment 38 and coupled to the. jack.
The jack includes an L-shaped leg 410 pivotally connected at one
CA 02305996 2000-04-18
end to an elongated leg 412, such as with pin 415. The L-shaped
leg 410 also pivots through the axis of pin 420 on mounting plates
422. Actuating the lift assembly lift cylinder 52 (Figure 1)
causes chain 110 to life the jack into the deployed position shown
in Figure 5B.
Figure 6 shows another alternative embodiment of the jack
assembly. In this embodiment, screw style jack 450 includes an
inner shaft 455 received in an outer housing 460 that is threaded
in at least a portion of its outer surface. The inner shaft 455
includes a plurality of key holes or slots 461, into which pin 465
is slidingly engageable to lock the inner shaft 455 in place
relative to the outer housing 460. To that end, the outer housing
also has a slot near its upper end for insertion of pin 465.
Removal of the pin 465 allows the inner shaft to drop to the ground
by action of gravity. The pin 465 is then re-inserted through the
appropriate slot 461, locking the inner shaft 455 in place.
Further adjustment is then obtained by rotating the threaded outer
housing/inner shaft combination about its longitudinal axis through
fixed nut 470 coupled to the A-frame 30. Handle 475 is provided
for ease in rotating the assembly.
Figure 7 shows a further embodiment of the jack as;~ernbly. In
this embodiment, a rocker 480 is used, having a slot 481. Linking
means 110 such as a chain has a f first end f fixed to the hood 53 , and
a spaced second end coupled to the rocker 480 in slot 481. Also
coupled to the rocker 480 in slot 482 is the jack 510, which is an
elongated leg terminating in a shoe 511. A spring 512 surrounds
16
CA 02305996 2000-04-18
the elongated leg between the rocker 480 and the A-frame 30 as
shown. The linking means 110 is shown in position "A", in which
the jack 510 is in the deployed position, the shoe 511 contacting
the ground. As the linking means 110 is raised, the rocker 480
pivots about pin 490 until the linking means 110 is now in position
"B" in slot 481. This causes a corresponding lifting of the jack
510 in the vertical direction towards the A-frame 30. As the
lifting continues, the shoe 511 contacts the A-frame, providing a
stop to the vertical movement of the jack 510. Continued lifting
the linking means 110 results in lifting of the plow blade.
The controls for operating the lift assembly are preferably
housed inside the cab of the vehicle for easy access to the
operator. Typically, there are two separate momentary contact
switches in any position but the down position, where it is not
momentary. A plurality of solenoids are used to control the
mechanism, such as a solenoid to control the power that runs the
motor for the pump. This circuit is energized off of any of the
control positions except the down position, thereby actuating the
pump to raise and/or angle the blade. Gravity allows the blade to
return to ground. Three hydraulic solenoids are mounted to the
output manifold of the pump. One is the unit that opens the path
to lift the blade, another is the unit that opens the path to lower
the blade assembly. In the up position, the first solenoid opens
the valve and the pump is energized, which raises the blade. In
the down position, the other solenoid opens its respective valve,
but the pump is not energized, which allows the blade to lower.
17
CA 02305996 2000-04-18
There is a three-position hydraulic spool valve for the
angling of the blade. As the switch is pushed to one side, it
opens the corresponding valve and energizes the pump, which then
pumps fluid into the corresponding piston which causes the piston
to extend and to thereby angle the blade . At the same time, it
allows the non-pressurized piston to collapse and fluid to return
to the tank (the force of the extending piston collapses the
opposite piston). When the switch is engaged in the other
direction, the reverse occurs. When the switch is returned to the
neutral position, so does the valve.
The control system for the jack meets several important safety
criteria. The jack should not be operable from within the vehicle
cab, as the jack should be visible to the operator during
operation. In addition, the jack should not be capable of being
deployed if the snow plow blade is raised up off the ground, in
order to avoid damage to the jack arm when the blade is
subsequently lowered. Similarly, there should be no possibility of
the jack retracting when the electrical power/control connector is
connected or disconnected. Also, the jack should retract
automatically whenever the snow plow bade is raised off the ground,
in order to prevent the operator from inadvertently driving off
with the jack arm in the deployed position. Lastly, the snow plow
(or other accessory) should not be able to be raised unless the
lift assembly is securely latched to the vehicle.
Some of these criteria are met by integrating the snow plow
control system with the jack control system. Other of these
18
CA 02305996 2000-04-18
criteria are met by the design of the hydraulic valve circuit and
the placement of the jack control.
Specifically, the jack controls are preferably placed in an
accessible location, such as on the snow plow A-frame 30, on the
front of the vehicle grill/bumper area, in the head gear area,
etc., so that the operator can operate the jack while visually
inspecting the height of the lift assembly and align it
appropriately with the vehicle.
As can be seen from the circuit diagram of Figure 8, to
prevent the jack from being deployed with the snow plow blade in
the raised position, the power supply (12v DC) for the jack control
electric circuit is taken directly from the snow plow control
"lower/float" electrical circuit (pin 3). This causes the jack
control circuit to receive power only if the snow plow control is
in the lower/float position. The jack will not deploy unless it
receives power to its control circuit.
To prevent the possibility of the jack retracting when the
power/control electrical connection is connected or disconnected
from the vehicle, the hydraulic valve circuit controlling the jack
retract function is designed with a separate "normally closed"
valve, illustrated as hitch retract coil ##6 in Figure 9. As a
result, the solenoid valve assembly must be separately powered to
actuate and force toe jack to retract. This prevents the
possibility of a 3-way or 4-way valve sticking in the opposite
position and allowing the jack to retract when the power supply is
cut of f .
19
CA 02305996 2000-04-18
To force the jack to retract automatically when the snow plow
blade is raised, the control for retracting the jack is cross-
connected with the control for raising the snow plow blade, with a
diode 150 between the two circuits (Figure 8). The diode 150
permits the snow plow "raise" control to also energize the jack
"retract" control, but will not permit the jack retract control to
energize the snow plow raise control by back feeding power through
the snow plow control. Thus, when the operator places the snow
plow control in the raise position via lift solenoid coil ##3, the
snow plow blade raises and the jack retracts (hitch retract
solenoid coil ## 6) simultaneously. However, if the operator places
the jack control in the jack retract position, the snow plow blade
will not raise.
As illustrated in Figure 9, preferably,the hydraulic controls
include a flow divider which routes the hydraulic fluid to either
the actuator drive or to the jack drive, as needed. The actuation
means for raising and lowering the jack is dedicated to this
operation, thereby eliminating any labor that would be necessary
were one to use an actuator that is "borrowed" from another
application, such as the cylinder 52 for lowering or raising the
plow blade. The flow restrictors also serve to slow the flow of
hydraulic fluid, thereby easing the rate at which the snow plow
blade is lowered, and preventing it from slamming into the ground.
The flow restrictor also allows smooth operation of the retracting
and deploying of the jack.
To prevent the possibility that the vehicle is driven without
_ ~ CA 02305996 2000-04-18
the lift assembly being properly secured to the vehicle, a
mechanical switch is placed in the latch 220 so that when the latch
220 properly engages bar 200, a circuit is completed allowing the
lift solenoid coil #3 to operate. This can .be accomplished by
placing a "normally open" switch, such as a plunger-type switch 350
(Figures 10A, 10B), mounted to the lift frame on the passenger's
side of the plow and in electrical communication with the control
float and the lift solenoid coil #3 (Figure 8). The safety switch
is closed when the latch 220 is properly engaged and locked, such
as with the snap-lock safety pin 310 which can be moved to contact
the switch 350, thereby allowing current to flow and the snow plow
to lift upon actuation of the control float. The pin 310 can be
locked in place as shown in Figure 10A. Without activating the
switch 350, the operator will not be able to lift the plow. This
forces the operator to engage the locking pins, ensuring that the
plow (or other accessory) is properly attached to the vehicle
before lifting the same.
In operation, the vehicle is positioned close to the hitch
assembly, and the jack mechanism is operated so that the lift
assembly is raised or lowered depending upon the height of the
receiver plate 11. Once the proper height is achieved (as
determined by visual inspection) , the vehicle is driven towards the
male end 215 of the hitch assembly so that it is received under the
receiver plate 11. At this point the latches 220 are in the
unlocked position shown in Figure 1, configured to grasp and engage
the bar 200. Once the bar 200 is positioned in the recesses 225 of
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CA 02305996 2000-04-18
the latches 220, the lever 221 is used to draw the latches 220
around the bar 200 and interlock the same. The lift assembly is now
locked to the vehicle chassis. (This closes the normally open
switch bewteen the control float and the lift coil #3, allowing the
snow plow to be raised.) The, jack is then retracted to its
inoperative position where it is stowed during use of the plow. To
disengage the lift assembly from the chassis, the jack is lowered
to the ground to support the assembly, and the lever 221 is placed
in the up position, which pushes the latch away from the bar 200,
disengaging the same and actually pushing the receiver plate 11
away from the lift assembly.
Those skilled in the art will appreciate that the present
invention is not limited to application to snow plows; other
utilitarian accessories such as brushes,, sweepers, carts, push
bars, hitches, winches, etc. can be used.
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