A hoist includes two lift columns with a base for supporting the upright on a floor, the base projecting to a working side of the upright and a lift arm mounted for sliding movement up and down along the upright with the lift arm projecting to the working side of the upright. A safety mechanism, for limiting movement of the lift arm slide downwardly along the upright towards the base, has an upright rack and a latch engageable with teeth spaced along the rack with an upper cross member coupling the uprights of the two column assemblies at a position spaced above the bases thereof; and a lift mechanism for simultaneously raising and lowering the lift arm slides along the respective uprights.
In use, this hoist is positioned to one side of the equipment to be elevated with the column assembly placed just beyond each corner of the equipment and the lift arms spaced to the front and back respectively. Adapters on the lift arms are used to engage the equipment, usually the frame, at jacking positions where access is generally not required. The equipment may then be raised to provide substantially unfettered access to all sides of the equipment.
Fig 1 shows a hoist (10) that includes two column assemblies (12) and (14) that are mirror opposites and spaced apart. Each column assembly includes an upright column (16) mounted on a base (18) that projects to a working side of the hoist where the equipment is located when it is to be raised. The base has ramps (20) and (22) on its opposite sides so that wheeled equipment can travel over it to and from the lifting position without undue obstruction.
The column is supported on the base (18) by a pair of spaced gusset plates (24) on the working side, and by gussets (26) on the opposite side. The column is cylindrical and carries a slide sleeve (28) that is configured to slide up and down on the column. A lift arm (30) projects from the slide sleeve to the working side of the hoist, above the base (18). A lift arm is mounted on the slide sleeve by two arcuate gusset plates (32). The lift arm is of square cross section and has an open outer end which serves as a socket (34). A tool tray (36) is mounted on a square section shaft (38), which slides into the end socket (34) of the lift arm to support the tool tray at the end of the arm.
Adapters (40) are used to mount equipment on the lift arms. Each adapter includes a square sleeve (42) that slides onto a lift arm (30) and lift members (44) projecting from the sleeve to engage the equipment, usually at a jack point and in a manner recommended by the equipment manufacturer. This arrangement makes it very simple to set the hoist up for various kinds of equipment from different manufacturers while still meeting the manufacturer’s recommendations.
Each gusset (26) connects to a bracket (50), which supports a safety upright (52) on the side of the column opposite the working side. The safety upright (52) is a channel open to form two side walls forming racks (54) on the side confronting the column (16). Each rack (54) has a series of hooks or teeth (56) projecting from the upright towards the column. The safety mechanism also includes a latch or pawl (58) mounted on the slide sleeve (28). The latch includes two spaced side plates (60) and a cross pin (62) that is configured to engage in the hooks (56) of the safety rack.
The side plates are pivotally mounted on a pin (63) of the latch bracket and spring biased to rotate the side plates in a clockwise direction bringing the pin (62) upwardly. A stop (64) on the slide sleeve (28) limits this pivotal movement at the 9:00 position (on a clock face).
In use, as the slide sleeve ascends along the column, the latch and its pin (62) is deflected past the curved backside of each of the hooks (56) in turn so that should the slide sleeve be released, as it descends, the pin (62) will engage in the next lowest hook (56) to prevent uncontrolled descent.
The slide sleeve (28) is free to rotate on the column (16). The safety upright (54) is coupled to the upper end of the column (16) by a bracket (68).
In the hoist, the two column assemblies are joined by an upper cross member (80) which extends between the upper ends of the two columns and a lower cross member (82) which extends between the two bases (18). Mounted on the upper cross member (80) is a gearbox (84) carrying a cable drum (86). The gearbox is driven by a reversible electric motor (88) mounted on the cross member (80) beside the gear box through a pulley drive (90). Two cables (92) are wound on the drum (86). Each cable (92) extends from the drum to a respective end of the cross member (80) hoist where it passes over a sheave (94) mounted on the cross member (80) at the top of the respective column (16). Each cable then extends downwardly from sheave (94) and around a sheave (96) mounted between the lift arm gussets (32) and then back upwardly to a dead end cable anchor (98) at the top of the column, mounted on the cross member (80), thus forming a pulley system.
The motor (88) is controlled by a control box (100) on the end of a flexible electric cable (102) so that the hoist may be operated without restriction on the operator’s position.
At the centre of the cross member (80) is an upright sleeve (104). A shaft (106) is mounted for rotation about the vertical axis of the sleeve (104). At its bottom end, the shaft (106) carries a engine suspension arm (108) that projects to the working side of the hoist.
An engine hanger slide (110) is mounted slideably on the arm (108) and is equipped with fittings from which a chain or the like may be suspended. The arm (108) is supported by a brace (109) extending from the cross member shaft (106) to the free end of the arm.
A modification can be provided by which the gussets 32A carried on the sleeve (28) have a transverse support hole 32B or generally square cross-section for receiving a transverse support beam 32C to which the arm (30) is attached.
In this way the arm (30) is no longer aligned with the gussets 32A and it can be moved to the left or to the right of the gussets 32A to increase or decrease the spacing between the arms 30 and therefore between the lift adapters 40.
