Metal working – Method of mechanical manufacture – Disassembling
Patent
1986-06-30
1988-11-01
Eley, Timothy V.
Metal working
Method of mechanical manufacture
Disassembling
294264, 219 70, B23P 1900, B23P 1902
Patent
active
047809442
DESCRIPTION:
BRIEF SUMMARY
The object of this invention is to provide a method and a tool for the freeing of parts held fast together, especially for the freeing of rusted bolts and nuts.
According to prevailing current practice percussion wrenches or hydraulic tools are used for the freeing of rusted nuts. Among the drawbacks of such solutions it must be mentioned that the work is physically arduous and that at every moment there is the danger of industrial accident. Particularly awkward in the freeing of rusted nuts is the long-established additional use of heat, such as the use of gas welding equipment.
Among the disadvantages of such heating method must be mentioned that the gas bottles and pipes must be conveyed ot the object to be freed which is often located in sites that are difficult to reach and even hazardous. Naturally this is especially undesirable and timeconsuming. It must be further mentioned as a drawback connected with the use of gas welding equipment that in the heating of larger nuts in difficult places the flame may become excessive which can damage the flanged or machined surfaces.
The objective of this invention here presented is to eliminate suchlike shortcomings and drawbacks of the long-established freeing methods. This objective is achieved with the method according to the invention in which the electrically conducting endpiece of the tool is pressed against the part that is held fast together, an electrical potential difference is created between the fast-held part and the endpiece which induces an electric arc and with the thermal energy generated by the arc the fast-held part is heated and thermally cut, after which it is freed from its fastening point, and by the tool according to the invention, having a body part fitted with an electrically conducting, detachable and advantageously sprung endpiece and equipped for the conduction of electrical current to the endpiece for the formation of an electrical arc.
An advantage of the invention which must be mentioned is that the physical accomplishment of freeing is accelerated, which significantly shortens the working time taken by the freeing operation. Further it must be realised that a gas flame is not needed at all, so that the freeing operation can be accomplished without difficulty in connection with various cast constructions and in machine repairs. In accordance with the invention heat does not rise too high so that fire-and metallic damage are avoided. It must be held as an especially significant advantage that working in fire and explosion-hazard sites is safe and also that freeing work can be performed in underwater circumstances.
Certain advantageous modes of application of the invention are described in the following with the aid of reference to the accompanying drawing, which depicts the tool for freeing parts held fast together according to the invention, in part cross section as seen from the side.
As is evident from the drawing the freeing tool according to the invention comprises a rotated, electrically conducting and spring-loaded endpiece 21 and means for the conduction of electricity to the aforementioned end piece 21. Both endpiece 21 and the electricity-conducting equipment to it are fitted to advantage to the tool body part 20.
Use of the tool according to the invention, in freeing the fast-bound part 1, especially a rust-bound nut, takes place as follows: first the electrically-conducting endpiece is pressed against the nut to be freed, after which an electrical potential difference is created between the nut and endpiece, which induces arcing from endpiece 21 to nut 1, which arc in developing thermal energy heats the nut 1. which due to thermal expansion expands, which makes possible freeing of the nut.
In accordance with an advantageous application mode of the method according to the invention the endpiece 21 is essentially rotated throughout the heating stage, when in addition to heating of the nut, thermal cutting of nut 1 is possible. It is then advantageous that the endpiece 21 be formed at its end as an open hollow part and man
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patent: 4538043 (1985-08-01), Alexander
Makelainen Hannu
Niinivaara Juhani
Eley Timothy V.
Oy GSS General Sea Safety Ltd.
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