Lift Truck With Mast
A lift truck includes an operator compartment having a center operating position providing an operator with a first field of view and an off center operator position providing the operator with a second field of view. A pair of forks extend away from the operator compartment. Each of the forks include a distal end. A pair of base legs extend away from the operator compartment and space laterally outwardly from the pair of forks away from a central axis of the truck. Each of the base legs include a distal end. A pair of mast columns is interposed between the operator compartment and the forks. A portion of the first field of view is blocked by the mast columns and a portion of the second field of view is blocked by the mast columns. The distal ends of the forks and the distal ends of the base legs are visible in the first field of view and the second field of view.
This is a continuation of U.S. patent application Ser. No. 12/106,802, filed Apr. 21, 2008, which is a continuation of U.S. patent application Ser. No. 11/467,754, filed Aug. 28, 2006, now U.S. Pat. No. 7,398,859, which is a continuation of U.S. patent application Ser. No. 10/634,377 filed Aug. 5, 2003, now U.S. Pat. No. 7,096,999, all of which are fully incorporated herein by reference.
BACKGROUND OF THE INVENTIONThe field of the invention is industrial lift trucks, and particularly lift trucks with telescopic masts.
A lift truck typically is a battery powered vehicle having an operator compartment with controls that enable the operator to drive the truck and to hoist materials and carry them quickly throughout a factory or warehouse. An upright telescopic mast is attached to the forward end of the truck and with a carriage, or forks, supporting materials can be hoisted by extending the telescopic mast upward.
An exemplary lift truck is shown in
A fork carriage 13 is slidable mounted to the inner telescopic section 23 and it is moved up and down thereon by carriage free lift cylinders 13A and B via chains 13C which pass over pulleys 13D. The outer telescopic section 22 is moved relative to the base section 21 by a main lift cylinder 22A located midway between the left and right mast sections. Lift chains (not shown in
These mast elements plus the associated hydraulic hoses and electrical cable provide obstructions which limit the operator's field of view when looking forward towards the forks from the operator compartment 10. This is particularly true when the mast is lowered and all the cylinders 22A, 13A and 13B are disposed directly in front of the operator.
Many efforts have been made to improve the operators' field of view when looking forward through the mast. These include shortening the main lift cylinders as disclosed in U.S. Pat. Nos. 4,191,276 and 4,261,438 so that it does not obstruct view when the mast is lowered, shifting the location of the main lift cylinder to one side as disclosed in U.S. Pat. No. 4,355,703; shifting the location of the single main lift cylinder to one side and shifting a single carriage free lift cylinder to the other side as disclosed in U.S. Pat. No. 4,506,764; and shifting the location of the two carriage free lift cylinders to locations nearer the mast uprights to increase visibility as described in U.S. Pat. Nos. 4,369,861; 4,365,693; 4,030,568 and 4,441,585. Yet another approach disclosed in U.S. Pat. No. 4,585,093 is to locate the two carriage free lift cylinders substantially behind the mast uprights and provide two main lift cylinders which are also behind the respective mast uprights. This is carried one step further in U.S. Pat. No. 6,505,710 in which the two main lift cylinders are formed into the base section of the mast.
A significant constraint on the design of a lift truck mast structure is its fore to aft dimension. The length of a lift truck is a very important characteristic, since turning radius is directly related to length. The productivity of a truck and operator is directly related to the turning radius since in the tight confines of factories and warehouses a smaller turning radius translates to less back-and-forth jockeying of the truck. The elimination of one or more inches in the length of a truck therefore has significant economic significance.
SUMMARY OF THE INVENTIONThe present invention is a lift truck in which the mast elements and associated lift elements are arranged to maximize the operator's field of view when looking forward from the operator compartment. In a preferred embodiment, an operator compartment provides an operator with a center operating position providing the operator with a first field of view and an off center operator position providing the operator with a second field of view. A pair of forks extend away from the operator compartment. Each of the forks include a distal end. A pair of base legs extend away from the operator compartment and space laterally outwardly from the pair of forks away from a central axis of the truck. Each of the base legs include a distal end. A pair of mast columns is interposed between the operator compartment and the forks. A portion of the first field of view is blocked by the mast columns and a portion of the second field of view is blocked by the mast columns. The distal ends of the forks and the distal ends of the base legs are visible in the first field of view and the second field of view.
A general object of the invention is to maximize the operator's field of view from both operating positions. In one embodiment, this objective is accomplished by nesting the mid rail members in the base rail members and mounting the lift chain pulleys forward of the top rail members, the two obstructing profiles of the mast columns are minimized when viewed from the operator compartment.
Another aspect of the invention is the arrangement of the main lift cylinders and a pair of free lift cylinders. The free lift cylinders are mounted to the top rail members and positioned substantially behind the mast columns and laterally inward from the main lift cylinders. Operation of the free lift cylinders raises and lowers a carriage slidably mounted to the inner telescopic section. The lateral location of the free lift cylinders is asymmetric with respect to the truck center line to provide clearance for a hose pulley which the left cylinder supports without reducing operator visibility.
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A mast 122 connects to the front end of the power unit 110 and extends vertically upward therefrom. The mast 122 supports a fork carriage 124 which can be elevated to different heights as will be described in detail below. The mast 122 is comprised of three telescopic sections which are shown best in
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Another asymmetry between the left mast column and right mast column is a set of hose pulleys 205 disposed behind the left mast column, between the main lift cylinder 172 and the free lift cylinder 160. As shown in
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The operator can also take a right forward position, in which his field of view emanates from a point 214 far to the right of the central axis 208. Two regions 216 and 218 are blocked from view by the left and right mast columns when the operator is in this position. It should be apparent that by shifting between these two operator positions the forward field of view extends to all but two, small triangular areas 220 and 222. Most importantly, the forks 224 are in complete view as are the ends of both baselegs 118. This expanded field of view facilitates driving the truck in confined spaces and placing loads on the forks 224.
Claims
1. A lift truck comprising:
- an operator compartment providing an operator with a center operating position, in which the operator takes a center forward stance, and an off center operator position, in which the operator takes an offset forward position, said center operator position providing said operator with a first field of view emanating from a point located near a central axis of said truck, and said off center operator position providing said operator with a second field of view emanating from a point located proximal a side of said truck far from the central axis within the operator compartment;
- a pair of forks extending away from said operator compartment, each of said forks of said pair of forks including a distal end;
- a pair of base legs extending away from said operator compartment, each of said base legs of said pair of base legs being spaced laterally outwardly from said pair of forks away from said central axis of said truck and including a distal end;
- a pair of mast columns interposed between said operator compartment and said forks; and
- wherein a portion of said first field of view is blocked by said mast columns and a portion of said second field of view is blocked by said mast columns, said distal ends of said forks and said distal ends of said base legs being visible in said first field of view and said second field of view.
2. The lift truck as recited in claim 1, in which each of said mast columns comprising:
- an outer telescopic section having an upright mid rail member, and
- an inner telescopic section having an upright top rail members slidably attached to the mid rail member and disposed laterally inward therefrom toward said central axis of said truck;
- said lift truck further including:
- a base section having a pair of spaced, upright base rail members attached to the lift truck;
- said mid rail members slidably attached to the pair of base rail members and disposed laterally inward therefrom;
- a pair of lift chain pulleys, one mounted to the upper end of each mid rail member and each being interposed between the top rail members of the inner telescopic section and said forks;
- a pair of lift chains, one disposed over each of the lift chain pulleys and having one end connected to the base rail member and a second end connected to the top rail member; and
- a pair of main lift cylinders connected between the base section and the outer telescopic section and being operable to extend the mast upward by sliding the outer telescopic section with respect to the base section.
3. The lift truck as recited in claim 1, in which each of said mast columns comprising:
- an outer telescopic section having an upright mid rail member, and
- an inner telescopic section having an upright top rail members slidably attached to the mid rail member and disposed laterally inward therefrom toward said central axis of said truck;
- said lift truck further including:
- a carriage slidably mounted to the inner telescopic section; and
- a pair of free lift cylinders mounted to the inner telescopic section and being operable to slide the carriage up and down the inner telescopic section, said free lift cylinders being disposed adjacent the inner telescopic section.
4. The lift truck as recited in claim 3, in which one of said free lift cylinders is connected to one of said top rail members and substantially laterally aligned therewith, and the other free lift cylinder is connected to the other top rail member and laterally aligned inboard of said other top rail member.
5. The lift truck as recited in claim 3, in which a hose pulley is mounted to the upper end of the outer telescopic section, the hose pulley being aligned laterally between one of said main lift cylinders and the other of said free lift cylinders and being disposed adjacent the mid rail member of said outer telescopic section.
6. The lift truck as recited in claim 1, in which each of said mast columns comprising:
- an outer telescopic section having an upright mid rail member, and
- an inner telescopic section having an upright top rail members slidably attached to the mid rail member and disposed laterally inward therefrom toward said central axis of said truck and each lift chain pulley extends through a web portion of the mid rail member to which it mounts.
7. The lift truck as recited in claim 1, in which said off center operator position provides said operator with the second field of view emanating from a point between one fork of said pair of forks and an adjacent base leg of said pair of base legs.
8. A lift truck comprising:
- an operator compartment providing an operator with a center operating position, in which the operator takes a center forward stance, and an off center operator position, in which the operator takes an offset forward position;
- a pair of forks extending away from said operator compartment, each of said forks including a distal end;
- a pair of base legs extending away from said operator compartment, each of said base legs of said pair of base legs being spaced laterally outwardly from said pair of forks away from said central axis of said truck and including a distal end;
- a pair of mast columns interposed between said operator compartment and said forks; and
- wherein said center operator position providing said operator with a first field of view emanating from a point located near said central axis of said truck, and said off center operator position providing said operator with a second field of view emanating from a point between one fork of said pair of forks and an adjacent base leg of said pair of base legs, a portion of said first field of view is blocked by said mast columns and a portion of said second field of view is blocked by said mast columns, said distal ends of said forks and said distal ends of said base legs being visible in said first field of view and said second field of view.
9. The lift truck as recited in claim 8, in which each of said mast columns comprising:
- an outer telescopic section having an upright mid rail member, and
- an inner telescopic section having an upright top rail members slidably attached to the mid rail member and disposed laterally inward therefrom toward said central axis of said truck;
- said lift truck further including:
- a base section having a pair of spaced, upright base rail members attached to the lift truck;
- said mid rail members slidably attached to the pair of base rail members and disposed laterally inward therefrom;
- a pair of lift chain pulleys, one mounted to the upper end of each mid rail member and each being interposed between the top rail members of the inner telescopic section and said forks;
- a pair of lift chains, one disposed over each of the lift chain pulleys and having one end connected to the base rail member and a second end connected to the top rail member; and
- a pair of main lift cylinders connected between the base section and the outer telescopic section and being operable to extend the mast upward by sliding the outer telescopic section with respect to the base section.
10. The lift truck as recited in claim 8, in which each of said mast columns comprising:
- an outer telescopic section having an upright mid rail member, and
- an inner telescopic section having an upright top rail members slidably attached to the mid rail member and disposed laterally inward therefrom toward said central axis of said truck;
- said lift truck further including:
- a carriage slidably mounted to the inner telescopic section; and
- a pair of free lift cylinders mounted to the inner telescopic section and being operable to slide the carriage up and down the inner telescopic section, said free lift cylinders being disposed adjacent the inner telescopic section.
11. The lift truck as recited in claim 10, in which one of said free lift cylinders is connected to one of said top rail members and substantially laterally aligned therewith, and the other free lift cylinder is connected to the other top rail member and laterally aligned inboard of said other top rail member.
12. The lift truck as recited in claim 10, in which a hose pulley is mounted to the upper end of the outer telescopic section, the hose pulley being aligned laterally between one of said main lift cylinders and the other of said free lift cylinders and being disposed adjacent the mid rail member of said outer telescopic section.
13. The lift truck as recited in claim 8, in which each of said mast columns comprising:
- an outer telescopic section having an upright mid rail member, and
- an inner telescopic section having an upright top rail members slidably attached to the mid rail member and disposed laterally inward therefrom toward said central axis of said truck, and each lift chain pulley extends through a web portion of the mid rail member to which it mounts.
14. The lift truck as recited in claim 8, in which said off center operator position providing said operator with the second field of view emanating from a point located proximal a side of said truck far from the central axis within the operator compartment.
15. A lift truck comprising:
- an operator compartment providing an operator with a center operating position, in which the operator takes a center forward stance, and an off center operator position, in which the operator takes an offset forward position, said center operator position providing said operator with a first field of view emanating from a point located near a central axis of said truck, and said off center operator position providing said operator with a second field of view emanating from a point located proximal a side of said truck far from the central axis within the operator compartment;
- a pair of forks extending away from said operator compartment, each of said forks including a distal end;
- a pair of base legs extending away from said operator compartment, each of said base legs of said pair of base legs being spaced laterally outwardly from said pair of forks away from said central axis of said truck and including a distal end;
- a pair of mast columns interposed between said operator compartment and said forks; and
- wherein said center operator position providing said operator with a first field of view emanating from a point located near said central axis of said truck, and said off center operator position providing said operator with a second field of view emanating from a point between one fork of said pair of forks and an adjacent base leg of said pair of base legs, a portion of said first field of view is blocked by said mast columns and a portion of said second field of view is blocked by said mast columns, said distal ends of said forks and said distal ends of said base legs being visible in said first field of view and said second field of view.
16. The lift truck as recited in claim 15, in which each of said mast columns comprising:
- an outer telescopic section having an upright mid rail member, and
- an inner telescopic section having an upright top rail members slidably attached to the mid rail member and disposed laterally inward therefrom toward said central axis of said truck;
- said lift truck further including:
- a base section having a pair of spaced, upright base rail members attached to the lift truck;
- said mid rail members slidably attached to the pair of base rail members and disposed laterally inward therefrom;
- a pair of lift chain pulleys, one mounted to the upper end of each mid rail member and each being interposed between the top rail members of the inner telescopic section and said forks;
- a pair of lift chains, one disposed over each of the lift chain pulleys and having one end connected to the base rail member and a second end connected to the top rail member; and
- a pair of main lift cylinders connected between the base section and the outer telescopic section and being operable to extend the mast upward by sliding the outer telescopic section with respect to the base section.
17. The lift truck as recited in claim 15, in which each of said mast columns comprising:
- an outer telescopic section having an upright mid rail member, and
- an inner telescopic section having an upright top rail members slidably attached to the mid rail member and disposed laterally inward therefrom toward said central axis of said truck;
- said lift truck further including:
- a carriage slidably mounted to the inner telescopic section; and
- a pair of free lift cylinders mounted to the inner telescopic section and being operable to slide the carriage up and down the inner telescopic section, said free lift cylinders being disposed adjacent the inner telescopic section.
18. The lift truck as recited in claim 17, in which one of said free lift cylinders is connected to one of said top rail members and substantially laterally aligned therewith, and the other free lift cylinder is connected to the other top rail member and laterally aligned inboard of said other top rail member.
19. The lift truck as recited in claim 17, in which a hose pulley is mounted to the upper end of the outer telescopic section, the hose pulley being aligned laterally between one of said main lift cylinders and the other of said free lift cylinders and being disposed adjacent the mid rail member of said outer telescopic section.
20. The lift truck as recited in claim 15, in which each of said mast columns comprising:
- an outer telescopic section having an upright mid rail member, and
- an inner telescopic section having an upright top rail members slidably attached to the mid rail member and disposed laterally inward therefrom toward said central axis of said truck, each lift chain pulley extends through a web portion of the mid rail member to which it mounts.
Type: Application
Filed: Nov 8, 2010
Publication Date: Mar 3, 2011
Inventors: Robert Lewis (Chenango Bridge, NY), John A. West (Vestal, NY)
Application Number: 12/941,647
International Classification: B66F 9/08 (20060101); B66F 9/06 (20060101); B66F 9/075 (20060101);