US 4,392,554 AGranted

Lift mast assembly

AssigneeTowmotor Corporation

InventorJames W. Russey

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Abstract

This invention relates to an improved visibility free lift mast (10) which eliminates the problems of reduced lift height, upright strength and excessive guide bearing loading. The lift mast assembly (10) has a fixed upright (42) and a movable upright (52) mounted on the fixed upright and elevationally movable relative thereto. A lower guide bearing (80) is mounted on a lower end portion (78) of the movable upright (52) and an upper (88) and intermediate (98) guide bearing is mounted on an upper end portion (92) of the fixed upright (42). The intermediate guide bearing (98) is positioned between the upper and lower guide bearings (88,80) a preselected distance (D) spaced from the upper guide bearing (88). The movable upright (42) is elevationally movable a first preselected distance at which the movable upright (52) is contactable with the intermediate guide bearing (98) and free from contact with the upper guide bearing (88) and a second preselected distance at which the movable upright (42) is free from contact with the intermediate guide bearing (98) and contactable with the upper guide bearing (88). Thus an improved visibility lift mast with free lift has been provided which offers maximum lift height for a given upright length, superior upright strength, and sequenced roller loading for improved roller life. The lift mast assembly is particularly useful in a fork lift truck.

Claims21

Dependent claims

In a lift mast assembly (10) having a fixed upright (42) and a movable upright (52) mounted on said fixed upright (42) and elevationally movable relative thereto, said fixed upright (42) having first (60) and second (62) spaced apart elongate flanges and an upper (92) end portion, said movable upright (52) having first (66) and second (68) spaced apart elongate flanges and a lower (78) end portion, said movable upright (52) having a lower guide bearing (80) mounted on the lower end portion (78) thereof and contactably engaged with one of the first and second spaced apart flanges (60,62) of said fixed upright (42), and said fixed upright (42) having an upper guide bearing (88) mounted on the upper end portion (92) thereof;

the improvement comprising:
an intermediate guide bearing (98) mounted on said fixed upright (42) at the upper end portion (92) thereof at a preselected elevationally spaced distance ("D") from said upper guide bearing (88) and between said upper (88) and lower (80) guide bearings;
said movable upright (52) being elevationally movable a first preselected distance, between a lowered position and an intermediate position, at which one of said first and second spaced apart elongate flanges (66,68) of the movable upright (52) is contactably engaged with the intermediate guide bearing (98) and said first and second spaced apart elongate flanges (66,68) of the movable upright (52) are free from contact with said upper guide bearing (88);
and
said movable upright (52) being elevationally movable a second preselected distance, between said intermediate position and a fully raised position, at which one of said first and second spaced apart elongate flanges (66,68) of said movable upright (52) is contactably engaged with the upper guide bearing (88) and both of the first and second spaced apart elongate flanges (66,68) of the movable upright (52) are free from contact with the intermediate guide bearing (98).

2 more elements

In a lift mast assembly (10) having a fixed pair of spaced apart uprights (12), a movable pair of spaced apart uprights (14) mounted on said fixed pair and elevationally extensibly movable relative thereto between a lowered position and an extended position, and a carriage (16) mounted on said movable pair of uprights (14) and elevationally movable relative thereto, each of said uprights (42,44,52,54) of said fixed and movable pair (12,14) have first (60,66) and second (62,68) spaced apart load bearing flanges interconnected by a web (64,70), each of said uprights (42,44,52,54) of said fixed (12) and movable (14) pair have an upper (106,134) and lower (102,110) end, said movable pair of uprights (14) has a lower end portion (78) and said fixed pair of uprights (12) has an upper end portion (92), a lower pair of cylindrical load rollers (74), one load roller (80) of said lower pair (74) being connected to the web (70) of one upright (52) of the movable pair (14) at the lower end portion (78) thereon, said one load roller (80) being contactably engaged with one of said first (60) and second (62) flanges of one upright (42) of the fixed pair (12) and the other load roller (82) of said lower pair (74) being connected to the web (70) of the other upright (54) of the movable pair (14) at the lower end portion (78) thereon, said other load roller (82) being contactably engaged with one of said first and second flanges (60,62) of the other upright of the fixed pair (12);

the improvement comprising:
an upper pair of cylindrical load rollers (84) each having a preselected diameter (A), one of said rollers (88) of the upper pair (84) being connected to the web (64) of one of said uprights (42) of the fixed pair (12) at the upper end portion (92) thereon and the other of said rollers (90) of said upper pair (84) being connected to the web (64) of the other of said uprights (44) of the fixed pair (12) at the upper end portion (92) thereon;
an intermediate pair of cylindrical load rollers (94), one of said rollers (98) of said intermediate pair (94) being connected to the web (64) of one of said uprights (42) of the fixed pair (12) at the upper end portion (92) thereon and between said upper (88) and lower (80) rollers, and the other (100) of said rollers of the intermediate pair (94) being connected to the web (64) of the other (44) of said uprights of the fixed pair (12) at the upper end portion (92) thereon and between said upper (90) and lower (82) rollers;
and
said movable pair of uprights (14) being elevationally movable a first preselected distance from said lowered position at which said intermediate pair of rollers (94) are engaged with one of said first (66) and second (68) flanges of the movable pair (14) of uprights and said upper pair of rollers (84) are free from contact with the first (66) and second (68) flanges of the movable pair of uprights (14), said movable pair of uprights (14) being elevationally movable a second preselected distance to said fully elevated position at which said intermediate pair of rollers (94) are free from contact with the first (66) and second (68) flanges of the movable pair of uprights (14) and said upper pair of rollers (84) are engaged with one of said first (66) and second (68) flanges of the movable pair (14) of uprights.

2 more elements

Dependencies are inferred from the claim text.