Loading Height Automatically Controlled: New Gallows Truck
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THE problem of . loading from a raised-deck vehicle with different floor heights has.successfully been overcome by Cleco Electric Industries, Ltd., Foundry Square, Leicester, by the production of an electro-hydraulic levelling ramp, which automatically controls the height of the rear wheels of the vehicle, so that a ramp between the deck and floor is always horizontal.
When the vehicle is backed up to the deck, the rear wheels rest on a hinged platform. A hinged ramp at deck level is lowered on to the floor, and if the flooris either above or below the deck, the platform is raised or lowered accordingly, the automatic operation of the platform also compensating for load variations.
H:nged Platform
The platform is hinged at its outer end and is actuated by two hydraulic rams below ground. A lever, linked to the ramp, is connected to a mercury switch, which controls a relief valve in• the hydraulic system and a contact in the electric circuit of the pump driving motor. If the ramp is raised above the level position the valve is opened, and if it falls below the horizontal the motor ' cuts in to operate the ramp pump. The current is switched off when the ramp is fully raised or lowered.
The platform is stabilized by two robust guides mounted in rollers, and lounging with an uneven load is impossible. The pump-driving motor of the prototype is a d.c. unit with a 1 h.p. rating; the circuit incorporates an R.C. rectifier, Ramp movement is controlled by a dashpot.
Equipment can be supplied to suit any loading requirement, with height variations up to plus or minus 20 ins. The prototype is used for vehicles with capacities up to 8 tons, and loading is from a 3-ft. 4-in. deck. The platform is made in sections and is 9 ft. wide by 10 ft. long. The excavation at the deck end of the platform is 8 ft. deep.
Cost £475 to £525 It is estimated that all the items of equipment can be supplied ready for erection for £475 with an a.c. motor, or £525 with a 48-volt d.c. motor and rectifier. Installation occupies about 12 man-hours, and its cost would vary between £50 and £200.
The advantages of a straddle-fork truck and a counter-balanced truck are combined in the new Cleco travellinggallows high-lift fork truck, known as the F.8.S.S.X. Mark 3. The gallows is Winched forward with the forks for pickkng up or setting down the load. and at the same time the rubber-tyred wheels of the straddle legs move outwards to extend the wheelbase and increase the load capacity.
It is claimed that use of the appliance enables up to 60 per cent, of the floor space to be used for storage. A standard 40-in. by 48-in. stillage can be stacked in an aisle of 6 ft., and with a 40-in. by 40-in. stillage the truck cart be turned A32 in an aisle of this width. The forks can be lowered to a height of 21 ins., so that all standard pallets and stillages can be handled.
The truck can ba produced for approximately 50 per cent, of the cost of a counter-balanced vehicle, and the saving in terms of weight and running cost is said to be about 75 per cent. Its weight is approximately 27 cwt. and it has a travelling length of 5 ft. 4 ins.
With pallets up to 3 ft. the capacity of the truck is 2,000 lb.; if longer pallets are used, the hydraulic relief valve is adjusted to reduce the capacity. The maximum lifting height is 8 ft. 2i ins., and the speed of elevation with two standard rotary pumps driven in tandem by I h.p. motors is 8 ft. in 37 secs.
A standard Cleco tiller-controlled single-wheel traction power head is driven by a • h.p. motor, which gives a pull of 600 lb. The truck can climb a gradient of 1 in 15 with a full load and 1 in 8 when travelling light with the ballast weights in place.
The hydraulic lifting gear is of the single-ram type, the rope pulleys being mounted at right angles to the frame to save space. The winch action is controlled by two enclosed hydraulic jacks, one on each side of the gallows to which are attached twin pulley blocks carrying the wire rope of the traversing system.
One jack is used for gallows extension and the other for withdrawal. The ropes are anchored at one end to the power head and form an effective guard between the gallows and the head when the gallows is extended. Winch action and lifting are controlled by a single twist-shaft lever mounted in the head of the gallows. Both the control lever and the traction-unit tiller are telescopic.