Cutlery – Cutting tools – Plural cooperating blades
Patent
1993-11-30
1996-01-02
Rada, Rinaldi I.
Cutlery
Cutting tools
Plural cooperating blades
30175, 30357, B26B 1700
Patent
active
054797101
DESCRIPTION:
BRIEF SUMMARY
This invention relates to apparatus for dismantling bolted connections and in particular to apparatus for removing a nut from such a connection.
BACKGROUND
It is sometimes extremely difficult to remove a nut by conventional means, especially after prolonged exposure to a corrosive environment, for example seawater. Whilst there are power driven tools such as hydraulic wrenches, it is often easier to simply cut the nut away or burn through it with a blow torch. Both of these methods have their own problems and/or risks, so relatively simple tools for splitting nuts have been developed.
A known nut splitter comprises a nut-encircling frame, or clamp which supports a cutting blade and means for forcing the blade into the side face of the nut to split it apart.
Common problems with existing nut splitters include the need for frequent blade replacement due to wear and tear, but more especially due to actual damage which is not repairable by re-grinding/sharpening. When as often happens the blade tip breaks off, a new blade is essential.
SUMMARY OF THE INVENTION
It is an object of the present invention to improve the performance of a conventional nut splitter.
According to the present invention, a nut splitter comprises a nut-encircling frame, a blade supported by and displaceable relative to said frame together with means for effecting said relative movement in a direction to split a nut within said frame, the cutting edge of said blade being formed with a blunt, rounded cross-section at said edge.
The blade is preferably triangular in cross-section, with an included angle at the cutting edge of from 40.degree.-60.degree.. The blunted tip preferably has a radius of from 0.5 to 2.5 mm. It is also preferred that the distal .ends of the cutting edge are also rounded, the exact degree of rounding being not particularly critical.
According to a further aspect of the invention the blade is symmetrical in cross-section, each of the three apices of the resultant equilateral triangle being formed as a cutting edge of the kind just set forth. By this means, a single blade can be provided with three working edges instead of the one previously available. In the event of damage the blade need only be rotated through 120.degree. in order to present a different working edge for use. Advantageously the nut splitter further incorporates a blade holder adapted to removably receive a blade having the cross-section of an equilateral triangle, thereby facilitating changing the working edge as necessary. The blade holder preferably includes means for retaining the blade. In practice a spring loaded ball detent is satisfactory for this, although other easily releasable means such as spring clips may be employed.
Surprisingly it has been found that the blunt, rounded edge profile of this invention is more efficient and considerably less vulnerable to damage than a conventional blade edge used for nut splitting. To illustrate this, the durability of a conventional, relatively sharp blade was compared with that of a blade with an edge according to this invention. Almost regardless of the metal used, the relatively sharp blade proved very liable to damage, including fracture of some or all of the cutting edge. Failure occurred after splitting only a very small number of nuts, in some cases only a single nut. By contrast, the cutting edge of the present invention proved to be almost indestructible.
In order that the invention be better understood a preferred embodiment of it will now be described by way of example with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view partly in section of a nut splitter according to the invention,
FIG. 1A is a right side view of the nut splitter shown in FIG. 1;
FIG. 2 is a side elevation of a cutting blade for use in the nut splitter of FIG. 1,
FIG. 3 is a cross-sectional end view of the blade of FIG. 2 on line X--X thereof,
FIG. 4 is a further cross-sectional end view of the blade of FIG. 2, but on line Y--Y thereof,
FIG. 5 is a plan view of a blade
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patent: 4875289 (1989-10-01), Poling
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Hydra-Tight Limited
Rada Rinaldi I.
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