Even if the lifting devices function well, they, suffer from drawbacks. In the first place the pneumatic cylinder mechanism entails a large installation dimension because the wire runs entirely inside the cylinder. At a lifting height of for instance two meters, the cylinder must also have a length of two meters. As a consequence of this fact, it will be difficult to reach every part of a room provided with such a lifting device. Further, the wire wears seals inside the cylinder, as a very long section of the wire must pass through the seals. This often leads to leakage and undesired maintenance. Further, there is always a risk that the handle or hook will break during the lifting. The wire can then be rapidly snatched upwards, before the air pressure in the cylinder stops the cylinder piston. This can cause damage to the cylinder and its seals. The operator himself must determine when the lifting shall be ended. If the operator interrupts the lifting too late, this can lead to the hook turning against the cylinder, which also can lead to detrimental jerks.
Therefore, this invention can be installed in smaller installation dimensions than has hitherto been possible, as the rope or wire in the pulling device is not stretched to its full length but is reeved around pulleys. The rope or wire does not either run through any pneumatic cylinder and therefore the risk for leakage because of the rope guide does not occur. An upper limit stop automatically interrupts the lifting operation at a pre-set distance and helps reduce jerking.
Fig. 1 shows a lifting device comprising two pneumatic cylinders 1A, 1B, which are attached to a basic element 2, suitably a U-beam or L-beam, which can form a suitable support construction to the horizontal cylinders 1A, 1B. Said two pneumatic cylinders (which can also be hydraulic) comprise a piston rod each 3A, 3B extending from the end wall which is not attached to the basic element 2. Said piston rods 3 are joined by a cross bar 4, and a first fiddle block 5 is provided on the cross bar 4 halfway between the piston rods 3A, 3B. The fiddle block 5 consists in a known manner of a large rope wheel 5A and a small rope wheel 5B, which are provided adjacent to each other between two plate-like side elements, so that the rope can be brought to and fro through the block without bringing the rope parts in the same plane in contact with each other. Said fiddle block interacts with a second fiddle block 6, which is attached to the basic element 2. A rope 7 runs between the two fiddle blocks 5, 6.
The rope 7 can be made very short. Often a length of two to three meters is sufficient. In rare cases, a longer rope can be needed, but more than five meters might in principle never be needed. The rope 7 is at one end provided with a handle 9 with a hook 8. The other end of the rope is secured in the second fiddle block 6. The rope 7 runs from the handle 9 up and beyond the large rope wheel 6A of the second fiddle block, further to the first fiddle block 5, around the large rope wheel 5A of the first fiddle block, and then back to the second fiddle block 6, and around its small rope wheel 6B. Then back to the first fiddle block 5, around its small rope wheel 56, and finally the second end of the rope is secured in the second fiddle block 6. Thanks to this arrangement a gear between the two fiddle blocks is created. The cylinders 1A, 1B are preferably provided inside a protected space by the provision of a protecting cover 14 (shown in phantom) around the device. The rope 7 can suitably be a Kevlar rope or a wire. The hook 8 is intended to be hooked on the object to be lifted. The handle 9 comprises a controller 90, which via a conduit 94 controls valves for the pneumatic operation.
The lifting device can also be attached to the ceiling or provided on a system of rails making the device movable in any optional direction. A suitcase coming on a truck can for instance be lifted by means of the luggage hoist and, without any large effort, be pushed over a belt, and then lowered the suitcase onto the belt.
Fig. 2 is an exploded view of an embodiment of the invention, where the pulling device consists of a so called rodless cylinder 1. The rodless cylinder, which is a standard element, consists of a pneumatic unit with a piston (not shown) inside a longitudinal cylinder 1 and an endless belt (not shown) secured in a loop to said piston. At the belt a pulling element 15 is provided on the outside of the cylinder 1, so that the pulling element 16 can be activated to move to and from along the cylinder 1. A first rope wheel 16 is then provided on the pulling element 15. A second rope wheel 17, which is fixedly mounted, is provided at one end of the cylinder 1.
The cylinder 1 is provided with two brackets 18, 19. At respective bracket double wheel pairs 20, 21 are provided, so called bogies. Said wheel pairs 20, 21 are intended to be provided inside a rail provided with a slit, so that the entire cylinder 1 can be moved along the rail by the wheels resting and rolling inside the rail, the slit of which is large enough, so that the brackets 18, 19 can protrude through. Said rail (not shown) is in its turn suitably displaceably arranged in an additional rail system, which enables movement of the cylinder in the transverse direction.
Further, it is shown that the rope wheels 16, 17, a gear rack 41, and a housing 40 are provided inside a case 22, 23. At one end of said case parts 22, stop bushings 24A, 24B are provided in each end thereof to limit the motion of the pulling element 15. At the bottom of the same casing part 22 a nozzle 70 is provided, through which the rope 7 runs. Then the rope runs around the second rope wheel 17 and further around the first rope wheel 16 in order to be fixed inside a stop means 25 with one end, which means is attached to one end of the cylinder 1.
The other end of the rope is fixed to the handle 9, which is provided with a hook 8. The handle is provided with a controller 90, which is pivotable around an axis 93. The lower portion of the controller 90 can interact with the first controller 92, and its upper portion with the second controller 91. Through a conduit 94 the signals are transmitted from the controllers to a control unit (not shown).
Automatic stop
On Fig.2 and Fig.7 is a mechanism to automatically interrupt the lifting, independent of the operator, at a predetermined acceleration. A housing 40 is movably provided along a gear rack 41. As can be seen from Fig. 3, there is a catch 43, which is movably mounted in the housing 40, which is movable together with the cylinder pistons. The catch 43 is arranged to move by inertia to a locking position, when the rope/wire and hence also the cylinder pistons accelerate rapidly, so that the acceleration exceeds a predetermined value. The housing 40 is fixedly connected to a movable part of the lifting device, for instance the pulling element 15, shown in Fig. 2. The mounted housing 40 then follows the motion performed by the cylinder piston. The housing 40 is arranged to move over the gear rack 41 interacting with the gearwheel 42, which is spins in the housing 40. The gear rack 41 is fixed to a stationary part such as the rear and front end piece 60, 61 of the cylinder 1, as is indicated in Fig. 2. The catch 43 is mounted so it can move in the housing 40. During normal drive, a compression spring 45 keeps the catch 43 in its ready position. If a suitcase handle breaks, the housing 40 will accelerate. Inertia will drive the catch 43 forward against the cog. A small part 46 of the catch 43 at the end of the catch 43 facing against the gear rack will then wedge between the cogs of the gear rack 41 and the gear wheel 42 and lock the drive, preventing the hook from moving upward.
