A traveller unit connected below the main frame has wheels coupled to bearings on both sides of the unit through a bored space. Each wheel has an involute spline gear groove on its centre bore matching a groove gear on the drive shaft. This design reduces the weight and volume of the main frame compared to previous designs, thereby making production costs lower. Other claims include reduced transports costs and simpler installation.
Existing art problems
According to the inventor, one type of conventional electric hoist has an intermediate shaft, connected to the traction motor, and extending through the inside of the wire-rope drum to a decelerator and electromagnetic brake. This makes it comparatively long, causing a loss in power. Any widening of the wire-rope drum also means that the intermediate shaft has to be lengthened, but the wire-rope drum cannot be increased over a predetermined width. The conventional design also means that the extended intermediate shaft rotates with the lifting operation of the hoist.
It is claimed that a high speed in the intermediate shaft causes vibration, which can damage the object being lifted. Avoiding this problem by rotating the intermediate shaft at a predetermined speed limits the speed and capacity of the traction motor, and thus limits the weight of the object that can be conveyed by the hoist.
An existing design of hoist, adapted to carry heavier objects, uses a motor rotating at high speed. In this a decelerator, hoisting traction motor and brake are mounted at one side of the drum with a horizontal arrangement on the upper portion of a main frame, also carrying the wire-rope drum. Four wheels on the corners of the frame each have a travelling decelerator, travelling motor and brake formed at one side of each to operate in cooperation. This arrangement of horizontal fixing means that each part occupies a relatively large space, resulting in a bulky structure. The large weight increases installation and production costs.
The design employs a sheave to support the wire-rope drum at its centre and perpendicular to it. This gives an angular differential to the object being transported, necessitating a capacity of hoist traction motor greater than the weight of object being carried, again increasing production costs.
The decelerator is housed in a gearbox with upper and lower portions containing lubricating oil. This may result in oil leakage through connections over a long period of time. In addition, the couplings of the decelerator, traction motor and wire-rope drum are force fittings that cause difficulties in assembly, disassembly, maintenance and repair.
The travelling wheels, driven in cooperation with each other, are integral with the main frame of the hoist, causing higher conveyance costs and high installation costs for high-capacity hoists.
How the invention helps
The invention tackles these problems with a winding sheave at the lower part of the winding drum connected to a driving sheave with a lifting hook to operate in parallel with each other. All the parts can be packaged separately for transport to the installation site, to make installation work easy and reduce transport costs. The travelling section is detachably mounted to the lower part of the main frame. Each of the parts can be exchanged in accordance with the load and size of the object, helping to standardise the product’s components, and improves power efficiency through connecting the parts in series.
The previously mentioned spline gear couplings on each of the travelling wheels and drive shafts makes the assembly process easier and increases the rotational efficiency of the couplings between the gears.
How it worksAbout the patent
This article is an edited version of patent WO/2006/135132, published December 21 2006 following the earlier award of a patent in the Republic of Korea. The inventor is Duck-Rae Cho of Kyunggi-do, and the joint applicant is KG Inc. of Incheon City. Korea Gorbel, also known as KG Cranes, is part of the international Gorbel group, headquartered in Fisher, New York state, US. KG Cranes manufactures a wide range of lifting and other materials handling equipment in four factories throughout South Korea and two in China. It was established in 1968, and makes a variety of industrial cranes including models for heavy-duty processing and shipyards, hoists, parts and maintenance services.Disclaimer
This article is an edited version of the patent and may omit legally or technically important text. To see the full patent go to www.hoistmagazine.com/patents.Marketing
The invention is understood to form the basis of the new db Hoist Series manufactured by KG Cranes in its Moke Po (RoK) factory. There are 10 main models, and 40 individual models, in the series with capacities from 2.5 to 400t, depending on other dimensions and requirements.
Fig 4 – Side view of the hoist travelling part in eccentric mode Fig 4 Fig 3 – Section through the travelling part, a significant part of the invention Fig 3 Fig 1 – Perspective of a hoist according to the invention Fig 1 Fig 2 – View of hoist from beneath with magnified view of decelerator connector Fig 2
