US2341309A - Cutting tool - Google Patents

Description

Feb. 8, 1944-. BETT|N| 2,341,309

CUTTING TOOL Filed oct. 28, 1940 Patented Feb. 8, 1944 UNITED STATES PATENT OFFICE CUTTING TOOL I David Joseph Bettini, Baltimore, Md., assignor' to Locke Insulator Corporation, Baltimore, Md., a corporation of Maryland Application October 28, 1940, Serial No. 363,222

2 claims.

The invention relates to insulators and more particularly to a tool for removing from insulator bushings that portion of the clay which tends to cause cracks and hence renders the bushing unfit for electrical use.

The principal object of the invention, generally considered, is to provide a cutting tool which may be inserted in the opening of the bushing and rotated therein, such cutting tool being adapted to cleanly cut a conical section from the bushing without detriment to the interior or exterior thereof.

Another object of the invention is to provide a cutting tool which is extremely simple in construction and in which the angle of the conical section to be cut may be regulated and which, by the substitution of simple parts, may be used with bushings of various sizes.

A still further object of the invention is to provide a cutting tool which may be rotated about its axis of symmetry and in which the cutting elements are taut wires which will cut clay without any tendency to drag the portions of the clay through which the wire is adapted to pass.

To these and other ends the invention comprises the various elements as hereinafter set forth, the novel features thereof being pointed out in the appended claims.

In the drawing:

Figure 1 is a side elevational view of the cutting tool in operative position in a bushing blank.

Figure 2 is a sectional view on the line 2-2 of Figure 1, the direction of view being indicated by the arrows adjacent said section line.

Figures 3 and 4 are, respectively, side elevations of bushing blanks showing in dotted lines the openings therein and also indicated by dotted lines are the conical sections removed by rotation of the cutting tool.

Figures 5 and 6 are respectively partial sections on lines 55 and 65 of Figures 3 and 4.

Figure 7 is an enlarged view of the end of the cutting tool showing the method of maintaining the cutting wires in position.

Before describing the invention in detail it might be pointed out that in the manufacture of bushings it has been common practice to provide in the orifice of the pug mill a die member centrally disposed with reference to the surrounding walls of the orifice and by which a longitudinally extending opening of the desired configuration and size may be forced in the clay as extruded. Definite lengths of the extruded pug are cut as the clay is being extruded and these pug segments are then allowed to dry until they reacheither the leather or the bone dry state. In the leather dry state they may be operated upon by a profile machine and the necessary ribs, skirts or corrugations formed on their exterior surfaces, or if the clay is allowed to reach the bone dry state the necessary surface conformation can be produced by the use of proper grinding wheels and tools. It has been known fora great number of years that, in bushing blanks in which the diameter of the bushing is large compared with the diameter of the orifice, during the drying stage a very large percentage will develop incipient cracks adjacent the central opening. These cracks, of course, destroy the value of the bushing as an electrical insulator. In a number of casesthe cracks do not develop until after the insulator has been glazed and fired, the result being a great decrease in volume production and a tremendous factory loss due to defects in the insulator not appearing until after the entire cycle of operation thereon has been performed.

- Attempts have been made to obviate the formation of these cracks by inserting in the ends of the bushing blank opening properly shaped wooden plugs so as to compress the clay by enlarging the ends of. the opening in the bushing, but such attempts have been found detrimental rather than beneficial.

As a-result of the investigation carried on by the applicant he has determined that the cracks above described are primarily due to the fact that the clay in the central portion of the insulator has been compressed to a high degree by its passage over an adjacent die member, the cutting of the pug permitting the clay adjacent the ends of the cut pug to expand to relieve the compression strains, and such expansion of the clay forms incipient cracks which are nearly microscopic in dimension in the initial stage but which, on the drying of the insulator blank tend to increase both in size and depth. Applicant found further that by removing from the ends of each pug or preliminary insulator blank a conical section from the clay surrounding the central opening there is no tendency of the clay to expand adjacent the thus enlarged opening. To accomplish this clay removal simply and expeditiously without injury to the surrounding body applicant has devised the tool illustrated in the accompanying drawing and which will now be described in detail.

In the drawing the cutting tool comprises a handle I to which is rigidly connected a metal rod 2 having at the outer end thereof a slot or from bushings having openings of different diameters. f v I I Adjustably mounted on the rod between the cap and the handle I is a cylindrical disk 6 having a boss 1 provided with an opening 8 in which a set screw 9 is positioned and by means of which the disk 6 may be adjustably positioned on the rod 2 at any desired point. The' disk isprovided with recesses H) at or adjacent the pe-/ riphery into which are received and secured the ends of a wire II, the latter preferably beingseated within the slot 3 formed in the outer end of the rod 2.

It will be understood that by substituting disks of different diameters the angle which the wires l l form with reference to the longitudinal axis of the rod 2 can be adjusted so that the maximum diameter of the conical section to be cut from the interior ofthe bushing can be adjusted as desired. Such adjustment may also be made by merely extending the recesses H1 in the form of radial slots in the disk and securing the Wires at any desired position in such slots.

The operation of the device is as follows:

After the insulator blank has been brought to the leather dry state the operator grasps the handle of the cutting tool and forces the end of the same into the opening l2 of the bushing, and after the rod has moved into the opening a predetermined distance, which may be indicated for example by the marks I3 carried by the rod I2, the handle is rotated, causing the wires H to cut from the bushing a conical segment of the shape designated by the reference character I4. The cutting tool is then removed, causing the conical segments to be withdrawn from the opening and the operation is repeated at the opposite end of the bushing, forming at'each end of the bushing a frusto-conical opening of the desired size and depth, both of which may be regulated with great nicety by the instrument hereinbefore described. Not only is the bushing thus prevented from cracking but the enlarged opening in each end thereof causes a much more rapid and even drying of the bushing and in this manner tend materially to reduce the formation of incipient or visible cracks in the bushing blank.

It is common practice to provide the openings in the bushing of cruci-form shape, indicated by the reference character [5, but it will be obvious to those skilled in the art that by the use of the cap 5, whose external diameter is equal to the diameter of the cylindrical segments of the cruciform opening, conical segments may be removed from bushings of this type by the same tool operated in exactly the same manner.

It will be apparent to those skilled in the art that a single wire may be used rather than a pair of wires and that the tool so modified would operate in the same manner and perform the same operation.

Having thus described my invention, what I claim is:

1. A rotatable tool for forming a frusto-conical opening in a clay'mass, comprising a rod having at one end a cylindrical thimble concentric with the longitudinal axis of said rod, said thimble engaging the inner wall of an opening in said clay mass to position said tool and center the same during the rotation thereof, a member slidably positioned on said rod and extending normal to the longitudinal axis thereof, a pair of wires extending from diametrically opposite points on the surface of said rod to said slidable member, said wires each making a predetermined angle with the longitudinal axis of said rod, and means for rotating said rod about its longitudinal axis.

2. A-rotatable tool for forming a frusto-conical opening in a clay mass, comprising a rod having at one end a. cylindrical thimble concentric with the longitudinal axis of said rod, said thimble engaging the inner wall of an opening in said clay mass to position said tool and center the same during the rotation thereof, a disk member slidably positioned on said rod and concentric therewith, and a pair of cutting members extending from diametrically opposite points on the surface of said rod and adjacent the inner end of said thimble and connected to diametrically opposite points on said disk member, said last named points being equally spaced from the longitudinal axis of said rod, and means for rotating said rod about its longitudinal axis.

DAVID JOSEPH BETTINI.

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