Cutlery – Pipe and rod cutters – Rotary
Patent
1986-08-11
1989-05-23
Watts, Douglas D.
Cutlery
Pipe and rod cutters
Rotary
30102, B23D 2108
Patent
active
048317322
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a pipe cutter.
Pipes that require to be cut are often situated in confined spaces, e.g. under floor boards or close to walls.
Existing types of pipe cutters tend to have an awkward shape requiring a comparatively large clearance around the pipe when they are used.
Thus, a well known design of pipe cutter is based on a metal frame shaped as a rectangular "C" shape. A feed screw is threaded in the base of the C, parallel to the side, so that turning an external end knob moves the screw, and a freely rotatable circular cutting blade journalled at its other end, towards the inside of the top of the "C" whereat two rollers are located to hold a length of pipe so as to permit relative rotation.
The screw is adjusted outwards to accommodate the pipe of any dimension, and tightened. Then the whole device is rotated around the pipe, to cut into the pipe. As the whole device is rotated, the knob is also from time to time tightened up.
Not only this technique difficult, especially in confined spaced, but also the uneven cutting pressure often resulting from this action tends to leave a high degree of distortion to the pipe, particularly with ductile materials, which effectively reduces their bore size.
It is also noted by the inventor that domestic and industrial piping now comes in a limited range of standard diameters.
The earlier device described and ( other more complicated devices known primarily from Patent literature) are well capable of use with a wide range of diameters of piping. The present inventor has observed, however, that in practice domestic and industrial piping comes only in a few standard diameters, and has accordingly approached the problem differently. The present invention envisages a device non-adjustable, or of only limited adjustment capability, as to diameter though capable of enbodiment in a number of sizes, e.g. as a plumbers kit for standard central-heating installation or repair. Thus, there may be provided an easy to grip, comparatively small, pipe cutter which has a snap on/off action on a given size of pipe. Moreover, the cutting wheel derives an inward feed by the direct result of rotating the device around the pipe, to give uniform cutting pressure and thus minimal distortion.
In one aspect, the present invention consists in a pipe cutter for receiving a pipe in a holder permitting relative rotation, comprising a circular cutting blade caused to rotate by frictional contact of its edge with the pipe on such relative rotation and mounted on a shaft means which rolls along an arcuate surface in the holder as the blade rotates, the arcuate surface being so shaped as to cause the cutting edge to enter the wall of the pipe.
More specifically, the invention consists in a pipe cutter comprising a circular cutting blade of diameter d.sub.1 mounted on a shaft means of diameter d.sub.2 and a holder defining (a) an opening to accept pipe of diameter d.sub.3 and wall thickness t and to constrain relative rotation of the holder and the pipe about a centralpoint P fixed in relation to the holder and (b) an arcuate surface parallel to the pipe direction the distance of which from point P smoothly decreases from a value of (d.sub.1+d.sub.2+d.sub.3)/2 to a value not greater than (d.sub.1+d.sub.2+d.sub.3)/2-t, for constraining the movement of the cutting blade shaft means, as it is caused to rotate by the frictional engagement of the pipe with the edge of the blade, to follow the arcuate surface until the pipe is severed.
The holder may, for example, be a member easily graspable in one hand, having a central hole communicating with a slot extending along its length so that it can be pushed longitudinally over a pipe.
It is possible that some tolerance can exist in the pipe diameter i.e. distance d.sub.3 even without making the holder actually adjustable. For instance, the holder may have a suitably contoured recess or support rolls, to hold the pipe.
The arcuate surface may be fixed, but is preferably slightly movable against a spring-bias to facilitate smooth operation. Su
REFERENCES:
patent: 1431546 (1922-10-01), Servais
patent: 2466179 (1949-04-01), Milan
patent: 3249998 (1966-05-01), Shultz
patent: 3715804 (1973-02-01), Kelley
patent: 3795051 (1974-03-01), Feamster
patent: 3932937 (1976-01-01), Bastiansen
patent: 4422238 (1983-12-01), Kloster
patent: 4438562 (1984-03-01), Courty
Folkerts Michael D.
Watts Douglas D.
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