U.S. patent number 3,802,589 [Application Number 05/250,697] was granted by the patent office on 1974-04-09 for dual extensible reach truck.
This patent grant is currently assigned to Clark Equipment Company. Invention is credited to Donald A. Holtkamp.
United States Patent |
3,802,589 |
Holtkamp |
April 9, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
DUAL EXTENSIBLE REACH TRUCK
Abstract
An extensible mechanism for reach trucks in which the mechanism
has an extensible and retractable vertical member pivotally
attached to the rear portion of the vehicle for pivoting forwardly
and rearwardly, a boom connected to the upper end of the vertical
member and extending forwardly for supporting a load attachment
such as a fork, and an extensible and retractable member spaced
forwardly from the vertical member for supporting and pivoting the
boom. Power cylinders are preferably used to extend and retract the
two extensible and retractable members, and a power means is
provided for pivoting the vertical member forwardly and rearwardly.
The two extensible members may be moved in unison to lift the boom
vertically on a plane, or one of the members may be moved while the
other remains stationary, or they may be moved at different rates
in order to lift, move and place a load on the boom attachment in a
desired location. Either single or multiple extensible and
retractable vertical and power members may be used to control the
operation of the boom.
Inventors: |
Holtkamp; Donald A. (Battle
Creek, MI) |
Assignee: |
Clark Equipment Company
(Buchanan, MI)
|
Family
ID: |
22948788 |
Appl.
No.: |
05/250,697 |
Filed: |
May 5, 1972 |
Current U.S.
Class: |
414/707;
414/728 |
Current CPC
Class: |
B66F
9/0655 (20130101) |
Current International
Class: |
B66F
9/065 (20060101); B66f 009/00 () |
Field of
Search: |
;214/133,141,148,770,771
;212/46B,57,64,59R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Forlenza; Gerald M.
Assistant Examiner: Oresky; Lawrence J.
Attorney, Agent or Firm: Hobbs & Green
Claims
I claim:
1. An extensible reach mechanism for a truck having a frame with a
forward end and a rearward end, comprising a telescoping extensible
and retractable post pivotal in either direction from a
substantially vertical position, at its lower end to the rear end
of the truck frame, a boom pivotally connected to the upper end of
said post and extending toward the forward end of the truck frame,
a load carrying attachment connected to and adjustable relative to
the forward end of said boom, a power means connected to said post
for pivoting said post forwardly and rearwardly to move said boom
and load attachment forwardly and rearwardly, an extensible and
retractable leg spaced forwardly from said post for pivoting said
boom upwardly and downwardly to raise and lower the forward end of
said boom and thereby to elevate and lower said load attachment,
said leg forming a fulcrum for said boom when said post is extended
or retracted independently of or at a different rate from said
power means.
2. An extensible reach mechanism for a truck as defined in claim 1
in which said leg and said power means include hydraulic
cylinders.
3. An extensible reach mechanism for a truck as defined in claim 1
in which a pair of said posts and a pair of said second legs
support and operate said boom, and said posts and second power
means include hydraulic cylinders.
4. An extensible reach mechanism for a truck as defined in claim 1
in which a hydraulic cylinder is connected to said load attachment
and to said boom to position said attachment angularly with respect
to said boom.
5. An extensible reach mechanism for a truck as defined in claim 1
in which said leg is spaced further from said post at the top than
at the bottom, and said boom includes a downwardly extending
portion to facilitate lowering said load carrying attachment to a
point below the level of the ground on which the truck is
supported.
6. An extensible reach mechanism for a truck as defined in claim 3
in which said leg is spaced further from said post at the top than
at the bottom and said boom includes a downwardly extending portion
to facilitate lowering said load carrying attachment to a point
below the level of the ground on which the truck is supported.
7. An extensible reach mechanism for a truck, comprising a
telescoping extensible and retractable member pivotal in either
direction from a substantially vertical position and connected at
its lower end to the truck near one end thereof, a boom structure
pivotally connected to the upper end of said vertical member and
extending toward the other end of the truck, a load carrying
attachment connected to and adjustable relative to said other end
of the boom structure, a power means connected to said vertical
member for pivoting said vertical member forwardly and rearwardly
and moving said boom structure and load attachment forwardly and
rearwardly, and an extensible and retractable leg for pivoting said
boom structure upwardly and downwardly to raise and lower the
forward end of said boom structure and thereby to elevate and lower
said load attachment either separately from or in unison with said
extensible and retractable vertical member.
8. An extensible reach mechanism for a truck as defined in claim 7
in which said power means and leg include hydraulic cylinders, and
in which a source of hydraulic fluid under pressure and a pair of
valve means control the operation of said cylinders.
9. An extensible reach mechanism for a truck as defined in claim 7
in which a hydraulic cylinder is connected to said load attachment
and to said boom to position said attachment angularly with respect
to said boom.
10. An extensible reach mechanism for a truck as defined in claim 8
in which a hydraulic cylinder is connected to said load attachment
and to said boom to position said attachment angularly with respect
to said boom.
11. An extensible reach mechanism for a truck as defined in claim 7
in which a pair of said posts and a pair of said second legs
support and operate said boom, and said posts and second power
means include hydraulic cylinders.
Description
An extensible reach lift truck has special applications and
advantages in the construction field in that loads can be picked
up, delivered to the construction or building site, and lifted to
and placed on scaffolding without the necessity of special or
separate handling to transfer the load from the truck load carrying
attachment to the scaffold platform or other work supporting
structure. This type of truck has the further special advantage of
being able to pick up a load immediately in front of the truck
where the ground is firm, transport the load to the work site, and
deliver it to the scaffolding platform or partially completed
building and yet avoid driving onto the usual soft backfill around
the outside of the building. The extended reach trucks of the
standard or well known construction utilize a parallelogram
arrangement for the members supporting the forwardly extending
support or boom, with the members pivoted to one another and to the
truck frame. Movement of the members forwardly to a point
approaching the fully extended position result in a dropping of the
forward end of the support, thus causing difficulty in locating the
load at the desired level and maintaining it at that level while
advancing the load until it is positioned onto the scaffold
platform or other work support. Further, the problem caused by the
failure of the prior extended reach trucks to advance the load on a
horizontal plane, particularly as the load approached its fully
extended position, was compounded by the effect of heavy loads and
the weight of the conventional upright compressing the tires on the
front wheel adjacent the load attachment, and by the dip caused by
soft ground traversed by those wheels as the truck approached the
place where the load was to be discharged. While movement of the
load on a horizontal plane would not eliminate the difficulty
caused by the load on the tires of soft ground, it would result in
easier and more effective control of the extended reach mechanism
and load attachment under those adverse conditions. It is therefore
one of the principal objects of the present invention to provide an
extended reach truck having a boom structure in which the boom is
pivoted at its rear end to extensible posts and is supported midway
by an extensible power means, thus permitting the boom to be lifted
and lowered and extended and retracted on a plane, thereby
providing good maneuverability and maximum reach of the boom at
various load pick up and discharging levels.
Conventional extensible lift trucks have an upright mounted on the
front, and this upright is relatively heavy and has two or more
vertical tracks and cross members and operating cylinders which
obscure the view of the operator. It is therefore another object of
the invention to provide an extensible reach truck mechanism which
does not require an upright to lift a load to the desired height,
and which is so constructed and designed that the principal weight
of the truck and reach mechanism is near the end of the vehicle
opposite the load lifting end, thus effectively counterbalancing
the load during the lifting and maneuvering operations.
Another object of the invention is to provide a truck having an
extended reach mechanism which has the ability to pick up a load
below ground level, and which can be controlled either manually or
automatically to compensate for compression of the truck tires by
the load or downwardly or upwardly tilting of the forward end of
the truck as a result of the terrain, to obtain movement of the
load on the horizontal plane under those conditions.
Still another object of the invention is to provide a material
handling truck having an extended load mechanism of the aforesaid
type which is so constructed and designed that it has maximum
stability in all load handling positions and can be adapted to
various types of truck designs without any appreciable
modifications in the basic structure of the mechanism.
Further objects and advantages of the present invention will become
apparent from the following description and accompanying drawings,
wherein:
FIG. 1 is a perspective view of an extended reach truck embodying
the present invention and showing the extended reach mechanism in
its lowered position in full lines and in an elevated position in
broken lines;
FIG. 2 is a side elevational view of the present lift truck showing
the extended reach mechanism in its lowered and elevated
positions;
FIG. 3 is a front elevational view of the truck shown in FIGS. 1
and 2;
FIG. 4 is a rear elevational view of the truck shown in the
preceding figures; and
FIG. 5 is a schematic diagram of the operating system of the
extended reach mechanism.
Referring more specifically to the drawings, numeral 10 indicates
generally a lift truck on which the present extended reach
mechanism 12 is mounted, the truck having front drive wheels 14 and
16 and rear steerable wheels 18 and 20. While only the front wheels
are driven and the rear wheels are steerable, the truck may be one
in which the front and rear wheels are steerable and in which both
sets of wheels are drive wheels. The motor driving the truck and
providing the power for operating the extended reach mechanism is
under hood cover 22 and is mounted on frame 24, and the truck is
controlled by an operator from cab 26 wherein the manual controls
shown in FIG. 5 are located. While the extended reach mechanism may
be mounted on various types of trucks and truck frames, the one
shown has two longitudinal side members and a plurality of cross
members forming the support for the motor, controls and cab, and
also forming the basic support for the extended reach mechanism.
Various changes in the truck structure can be made to adapt it to
the desired operation to be performed thereby.
The extended lift mechanism 12 includes a pair of posts 30 and 32
normally assuming a substantially upright position and being
pivotally mounted on a shaft 34 secured to the rear end of frame 24
by mounting fixture 36. The two posts are rigidly joined to one
another by a steel plate 38 to form a bifurcated structure which is
adapted to tilt forwardly and rearwardly on the two pivot means 40
and 42, respectively, at opposite ends of shaft 34. Boom or arm 44
consisting of two longitudinal members 45 and 46 is pivotally
connected to the upper ends of posts 30 and 32, respectively, and
extends forwardly therefrom parallel to the sides of frame 24, the
two members being adapted to pivot on the upper ends of the posts
from a position such as that shown in solid lines in FIG. 2 to an
elevated position shown in broken lines. Arm member 45 is pivotally
connected to the upper end of post 30 by a shaft 48, and arm member
46 is pivotally connected to the upper end of post 32 by a shaft
50. A plurality of cross members 52 tie the two arm members
together so that they operate in unison in moving loads from one
position to another, both forwardly and rearwardly and up and down.
Joined to the forward end of the arms and forming a part thereof
are extensions 54 and 56 joined rigidly at one end to the main
portion of the arms and pivotally supporting a load attachment 60
at the other end. Pivot pins 62 and 64 connect the forward end of
the extensions to fixtures 66 and 68, respectively, on the
attachment. The load attachment, which may be considered
conventional for the purpose of the present description, is shown
as a fork lift, and is moved to various angular positions by a
suitable power mechanism such as a hydraulic cylinder 76. The fork
attachment is provided with two spaced forks 77 and 78 rigidly
connected to and supported by body or back structure 79.
Posts 30 and 32 are of a telescopic construction, i.e., are
extensible and contractable between the contracted position shown
in full lines in FIG. 2 and the extended position shown in phantom
in the same figure, the posts each having a conventional hydraulic
cylinder assembly 80, consisting of an external cylinder 81, and a
piston and piston rod 84 and 86, respectively, the latter being
connected to the rear end of the boom 44. Posts 30 and 32 are
pivoted forwardly and rearwardly on pivots 40 and 42 by cylinder
assemblies 90 on opposite sides of the truck, which are connected
at one end to frame 24 by fixtures 92, and connected at the other
end through the piston rod 93 to pivot means 94, the two hydraulic
cylinders being operated together from the same hydraulic system.
Boom 44 is raised and lowered and pivoted relative to posts 30 and
32 by a pair of extensible and contractable legs 96 and 98, each
consisting of hydraulic cylinder assemblies 100, the lower end of
each cylinder being connected to the frame by a fixture 102 and the
upper end through piston rod 103 to the arm members by a fixture
104. Fixture 104 for the upper end of cylinder assembly 100 is
spaced further from pivot 48 than fixture 102 for the lower end of
the assembly is from pivot means 40. Movement of the hydraulic
mechanism in the two posts 30 and 32 moves the rear end of the boom
upwardly or downwardly, causing the fixture 104 to which hydraulic
cylinders 100 are connected to function as the fulcrum for the
boom. The hydraulic cylinder 76, which is pivoted to extension 54
by a fixture 112 and to one of the side members of the upright by a
fixture 114, may be operated from the hydraulic system of the truck
as part of the system which operates the hydraulic cylinders of the
extended reach mechanism, or by a separate hydraulic system, as
described.
The hydraulic system for operating cylinder assemblies 80, 90 and
100 is shown schematically in FIG. 5, numeral 118 indicating
generally the portion of the system controlling cylinder 80 in the
posts, numeral 120 indicating generally the portion of the system
controlling the cylinder 90, and numeral 122 indicating generally
the portion of the system controlling cylinder 100. System 120 is
connected to hydraulic pump 124 which deliveres oil from a tank or
sump 126 through line 128 to a valve 130. The valve is connected to
the cylinder on opposite sides of piston 132 by lines 134 and 136,
and line 128 is connected through the valve to the sump by line
138. Line 128 is also connected to the valve by a branch line 140
which has a check valve 142 therein, and the return line for the
valve is connected to line 138 and to the sump by a line 144. When
post 30 is to be moved forwardly, i.e., to the left as illustrated
in FIG. 5, the valve is moved downwardly as viewed in the drawing,
thus connecting branch line 140 with line 136 and line 134 with
line 144, thus causing piston 132 and piston rod 93 to move to the
left, as viewed in FIG. 5, and to swing post 30 forwardly. When the
post is to be moved in the opposite direction, the valve is moved
upwardly as viewed in the drawing, thus connecting line 142 with
line 134 and line 136 with line 144. After the post has been moved
to the desired position, the valve is returned to its centered
position where the valve permits hydraulic fluid to pass
therethrough. A pressure relief valve indicated generally by
numeral 150 connects line 128 with line 138, thus limiting the
maximum pressure in line 128 for operating the piston when the pump
is in operation.
Hydraulic system 122 is connected to pump 124 by line 128', which
is an extension of line 128. Line 128' is connected to valve 158 by
a branch line 160 containing a check valve 161, and to the return
line 138 by a line 162 when the valve is in its centered position.
The valve is connected to cylinder 100 by lines 164 and 166. When
boom 44 is to be raised by legs 96 and 98, the valve 158 is moved
upwardly, as viewed in FIG. 5, thus connecting branch line 160 with
line 164 and with the cylinder on the under side of piston 168, and
connecting line 166 with return line 169, thus causing piston rod
103 to move the arm upwardly. When the boom is to be lowered, the
valve is moved downwardly, connecting branch line 160 with line 166
and line 164 with return line 169. Since system 122 depends on
valve 130 being in its neutral position for operation, valve 158
cannot control cylinder 100 while valve 130 is being controlled to
operate cylinder 90, since movement of the latter valve in either
direction disrupts the flow of fluid to valve 158.
Hydraulic system 118 which controls the operation of hydraulic
cylinder assembly 80 consists of a valve 180 connected to sump 126
or other suitable source of hydraulic fluid, by pressure line 182
and pump 184 and return line 186. A pressure relief valve 188
connects lines 182 and 186, thus limiting the maximum pressure in
line 182 for operating the cylinder 82. The valve, which is shown
as operated manually by a lever 189, is connected to the cylinder
on opposite sides of piston 84 by lines 190 and 192. When the rear
end of the boom is to be elevated, the valve is moved downwardly as
viewed in FIG. 5, thus connecting lines 182 and 192 with the lower
part of the cylinder assembly below piston 84, thus causing piston
84 to move upwardly and to pivot the boom on the fulcrum provided
by fixture 104 at the upper ends of cylinder assemblies 100. When
he rear end of the boom is to be lowered, the valve is moved
upwardly as viewed in the drawings, thus connecting the upper part
of the cylinder above piston 84 with return line 182, and the lower
part of the cylinder line 186.
Cylinder assembly 100 may be held in a stationary position while
cylinder assembly 80 is operated to tilt the boom upwardly or
downwardly, and hence move the attachment 60 downwardly or
upwardly, or the two cylinder assemblies 80 and 100 may be operated
simultaneously to lift or lower the boom while maintaining the boom
at a fixed angular position. In this operation, the two hydraulic
assemblies 80 and 100 operate to raise the load directly upwardly
or downwardly without an arcuate movement as normally occurs when
only, for example, cylinder assemblies 100 are operated while
maintaining the rear of the boom of a fixed pivot. The movement of
the two pivot points at which cylinders 80 and 100 connect to the
boom provides good versatility in the operation of the lift truck
and provides a substantial increase in the height the load can be
lifted without the use of an upright. Likewise, the load attachment
can be lowered to a point beneath the ground level on which the
truck rests, and it can be retracted or advanced at various levels
for raising and discharging a load by the operation of cylinder 90.
This permits a load to be picked up without the wheels of the truck
traversing the earth around the building under construction and to
be placed in a door, window or other opening, or on a platform at a
level substantially above the height of the truck.
In the operation of an extended reach truck having the lift
mechanism described herein, starting with the fork attachment in
its lowered position, the operator moves the truck forwardly to
slip the tines of the fork attachment under a load, and lifts the
load from the ground. Normally the attachment is operated by
cylinder 76 to tilt the load rearwardly and/or to lift it a short
distance from the ground. Cylinders 100 are then normally operated
to lift the load sufficiently from the ground to effectively clear
the area to be traversed by the truck. The truck is then maneuvered
to the position where the load is to be displaced such as, for
example, on the platform of a scaffold, and cylinder assemblies 80
and 100 are operated to lift the load in a substantially vertical
line to the platform. When the load is on a level with the upper
surface or slightly above the upper surface of the platform,
cylinder 90 is operated to move attachment 60 and the load thereon
onto the platform. Cylinder 100 is then lowered sufficiently to
place the load on the platform, and cylinder 90 is operated to
withdraw the attachment from the load and the platform. Cylinders
80 and 100 are operated by separate and independent controls so
that the load can be maneuvered effectively, either by raising the
boom upwardly or downwardly while maintaining it on a substantially
horizontal plane, or one cylinder may be moved while holding the
other cylinder fixed, thereby pivoting the boom at the center or at
the rear end, depending upon which of the two cylinders is moved.
The tines of the attachment are maintained on a substantially
horizontal plane by cylinder 76 as the boom is moved from the
position shown in full lines in FIG. 2 to the position shown in
broken lines.
It is seen from the foregoing that the present extended reach
mechanism places a substantial part of the mechanism near the rear
of the vehicle, thus counterbalancing at least a portion of the
load attachment 60 and at the same time giving the driver a good
forward view and a good view of the load and the attachment, so
that the truck can be easily maneuvered and the lift mechanism can
be operated effectively to place the load in any desired elevated
position, without interference from any upright or other mechanism
which could seriously obscure the view. The mechanism permits the
load to be readily placed in any desired location on a scaffolding
platform or through an elevated door or window of the building
being constructed, without requiring the truck to move directly
beneath the scaffolding or building wall and without requiring
special handling of the load.
A compensating mechanism such as the hydraulic system indicated
generally by numeral 180 in co-pending U.S. Pat. application Ser.
No. 221,346, filed Jan. 27, 1972, and owned by a common assignee,
can be incorporated in the present extensible reach mechanism to
prevent drooping of the load on the attachment and, under certain
operating conditions, to maintain the movement of the boom and load
on a horizontal plane. When the compensating mechanism is used in
conjunction with the extensible and contractable posts, an
adjustment means such as a hydraulic cylinder which extends and
contracts with cylinder 80, maintains the mechanism in proper
relationship with the posts and boom regardless of any temporarily
adjusted length of the posts. The compensation for droop, however,
can be performed entirely by the manual controls if desired.
While only one embodiment of the present dual extensible reach
mechanism for a lift truck has been described in detail herein,
various changes and modifications may be made without departing
from the scope of the invention.
* * * * *