Abrasive tool making process – material – or composition – Impregnating or coating an abrasive tool
Patent
1986-09-22
1987-12-08
Whitehead, Harold D.
Abrasive tool making process, material, or composition
Impregnating or coating an abrasive tool
83397, 83478, 125 13R, B24B 5504
Patent
active
047110554
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a displaceable protective cover, or guard, for handtools provided with rotatable, disc-shaped tools, such as disc cutters, grinding discs, circular sawblades etc.
Protective covers, or guards, of this kind are known to the art, and in particular in connection with circular saws, and comprise a stationary part and a displaceable part, this latter part, when in its rest position, together with the stationary part completely embracing the saw blade. The protective cover prevents personal contact with the tool and also protects the operator from flying chips, shavings etc.
Hand-operated cutting and grinding machines are used in a different manner than circular saws, and a protective cover of the aforesaid kind would present a serious obstacle in the operation of such machines. Consequently, there is used in conjunction with such machines a protective cover or guide of simpler construction which does not offer any protective function in the true sense of the word, despite the fact that these machines are the most dangerous to use. Because of its great mass, a cutting and grinding disc will continue to rotate at a high speed long after the drive motor has been switched off, and consequently a protective cover which fully encloses the disc would seem an obvious necessity. If it were possible to provide a protective cover of this kind which would not make the cutting and grinding work involved difficult to carry out, it might then be possible to reduce the amount of red-hot chips, dust etc. which are flung from the machine to the surroundings in work of this nature, or even to eliminate such an occurrence.
In order for the protective cover to live up to its name, it must be capable of preventing accidents should the tool throw to one side, i.e. move violently, as often occurs with both circular saws and with grinding and cutting machines. When a tool throws it moves extremely violently, and when the protective cover provided includes a displaceable part, the cover is likely to be moved to a position in which the tool is fully exposed. It is also possible that the workman will completely lose his grip on the handtool in such eventualities.
The object of the invention is to provide a protective cover which will practically totally obviate the aforesaid risks with all of the aforementioned kinds of handtools, without rendering the tool difficult to use to any appreciable extent.
This object has been achieved with a protective cover or guard means according to the invention having the characteristic features set forth in the following claims. The invention is based on the concept that when in its rest position the protective cover will fully embrace the rotary tool. In addition, it shall also be possible in the majority of cases to open the protective cover, by bringing the handtool into normal engagement with a workpiece. Moreover, it shall not be possible under any circumstance, for any of the displaceable cover-halves to be thrown up when subjected to impact, for example due to involuntary, violent movement, or throw, of the handtool.
This latter facility can be achieved in several ways. For example, both cover-halves may be provided with a latching mechanism which locks the cover-halves against continued rotary movement when the speed of rotation becomes excessively high, i.e. similar to the effect achieved with automatically coilable, vehicle safety belts.
The said facility can also be realized with a latching mechanism constructed to allow the two cover-halves to rotate synchronously from their rest position, and to lock the cover-halves against further rotation when one of said cover-halves has been rotated through an angle greater than the other. In this case, the handtool must be handled in such a manner that both cover-halves are pressed apart by the workpiece with substantially the same pressure. Tests have shown that this can be very readily achieved. This construction also imparts a highly valuable property to the handtool, inasmuch as the handtool will work the workpiece
REFERENCES:
patent: 1208765 (1916-12-01), Fow
patent: 1402959 (1922-01-01), Quinton
patent: 1464924 (1923-08-01), Drummond
patent: 2589309 (1952-03-01), Tompkins
patent: 3913437 (1975-10-01), Speer
patent: 4033218 (1977-07-01), Donatelle
patent: 4318324 (1982-03-01), Hall
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