US1946239A - Electrician's tool - Google Patents

Description

Feb. 6, V RY N ELECTRICIANS TOOL 2 Sheets-Sheet Filed April 25, 1933 INVENTOR- wZa flfiyan ELM Mm AT ORNEYS Feb. 6, 1934. v. A. RYAN ELECTRICIAN S TOOL Filed April 25, 1933 2 Sheets-Sheet 2 I I II, I I //II"! I INVENTOR- 1 VZFZW A. Ryan BY r/ ea M AT RNEYS Patented Feb. 6, 1934 UNITED STATES PATENT OFFICE ELECTRICIANS TOOL Application April 25, 1933. Serial No. 667,789

8 Claims.

The present invention relates to electricians hand tools insulated against high tension electricity.

The invention is disclosed herewith as a matr ter of illustration as applied to a screw driver. It is to be understood, however, that the invention is equally applicable to other hand tools.

Electricians hand tools are usually used on the line or in man-hole pits where the tools are subject to and are affected by atmospheric conditions. Regardless of the character of material used for insulation and its high di-electric strength, hand tools become coated with a film of moisture during damp weather or with moisture 15 from the hands of the workman and serious accidents may occur by flash-over voltage following the coating surface on the insulation of the tool. Serious and fatal accidents have occurred by currents flashing over the insulation where the dielectric strength of the insulating material used was entirely sufficient to prevent a direct breakdown of the insulating material.

Experimentation has shown that a substantially plane surface insulation is dangerous in damp weather and in hot summer weather when the hands of the workman perspire, if the tool is used on lines in the excess of 440 volts due to the danger of flash-over short circuits through the hand, arm, and body of the workman.

The present invention overcomes the difficulty of the known art by providing a construction wherein sheds or discs are provided to dissipate surface leakage and to trap any current which may leak over the surface of the insulated part 4 of the tool. The insulating sheds or discs may be located at angles of 90 or less from the axis of the tool. Preferably, the curvatures of the surface of the sheds are designed along lines at equal potential. Under these conditions, any current flowing on the surface of the insulating material tends to have a portion of its path comprise a back-flow which further increases the insulating characteristics. The number of sheds used on the tool may be increased to obtain higher resistant characteristics. Experimentation has shown that tools equipped with the present invention will withstand flash-over voltages which are four or five times the strength of the dielectric when dry; and even where saturated with moisture vapor, the flash-over voltage is higher than the dielectric strength of insulating material capable of withstanding several thousand volts.

The present invention is disclosed herewith on a specific tool such as an electricians screw driver, in which the entire shaft of the'screw driver is insulated with the exception of the working tip thereof and wherein the sheds are located between the handle and the exposed metal part of the screw driver. In the use of dewioes of this kind, it frequently becomes necessary to work over high tension lines to reach a lower tension line and which high tension line may touch the shank of the screw driver. When the present invention is in use, the tool is entirely safe under these conditions providing the contact is made on such portion of the tool as permits the sheds to lie between the point of contact and the handle held by the hand of the workman.

While the preferred form of the invention is disclosed in the drawings herewith, it is to be understood that the invention may be practiced F in constructions other than those specifically disclosed herewith.

Fig. 1 is a longitudinal sectional view through a screw driver in accordance with the present invention.

Fig. 2 is an enlarged view of the insulating sheds shown in Fig. l with one-half of the view shown in section.

Fig. 3 is a slightly different form of the sheds and one-half of the view is shown in section.

Referring now to Fig. 1 illustrating the screw driver in accordance with the present invention, a steel shaft 1 for the screw driver terminates in a driving head 2. The opposite end of the shaft is provided with extensions 4 or lands which are adapted to be embedded into the handle of insulating material to communicate torsion from the handle to the blade. insulating material 5 of a high dielectric strength is preferably molded around the steel shaft to entirely enclose the same with the exception of the exposed operating head 2. This insu1at ing material may comprise a bulbous portion 6 adjacent the driving head and a substantially straight portion '1 extending along the shaft 1. A bead 8 may be provided adjacent a conical portion 9 which leads tothe first shed 10 which is a circumferential flange preferably inclined toward the exposed end of the shaft comprising the driving head 2. This shed in the preferred form is slightly spaced from a series of other circular sheds l1 encircling a portion of the handle. Another bead 12 may be provided adjacent the handle 14: comprising the grip adapted to be held in the hand of the work man. The insulating material used preferably comprises a composition of high dielectric quality rubber for the reason that such tools are often dropped or roughly handled and it is particularly desirable that the insulating material shall not crack or chip. Any material which has high dielectric characteristics and will withstand rough usage is satisfactory for making the insulating handle for purposes of the present invention. The path of the tendency of flash-over or leakage voltage is indicated by the arrows A in Fig. 1, which shows the effect of the first shed 10 in doubling the current back upon itself so as to destroy its tendency to pass beyond this shed.

Fig. 3 illustrates a form which for some purposes may be preferable in that the sheds 15, 16, and 17 are constructed of such form and in such manner as to produce a condition wherein the air between the sheds is under equal stress and no sub-normal rupture is likely to occur by a flash-over. The lines A, C, and D indicate the preferred form of sheds in this Figure 3 and the lines B and D indicate zones wherein the air is of equal potential stress. Preferably, in this type of device, the sheds extend from a bulbous enlargement 18 and the sheds are progressively enlarged in diameter from the shed 15 to the shed 17.

This type of tool can be safely used up to voltages of several thousand even during conditions where the air is full of moisture or when the workmans hands are moist. Danger from surface flash-overs is particularly present on shipboard or adjacent the seashore where the moisture content of the air includes a small amount of salt which tends to deposit on the 2 surface of the electricians tools and to produce a surface coating of moisture with salt in solution which greatly increases the conductivity on the surface of the tool. The present invention, especially the form shown in Fig. 3, is particularly adapted to provide security under these adverse conditions. Furthermore, in handling the tool with moist hands, the moisture does not get into the valleys between the sheds.

It is to be understood that the location of the sheds need not be in exactly the position disclosed in the drawings, so long as the sheds are located between the handle or grip and the working head of the tool. The position shown in the drawings is the most suitable position for these sheds, and, therefore, is the preferred form of the invention particularly when it is applied to screw drivers. It is also to be understood that the sheds may be of different shapes or bends although the preferred form is that of an angle of or less as measured between the surface of the shed and the axis of the tool with the angle specified being toward the working head of the tool.

What I claim is:

1. As an article of manufacture, an electricians insulated hand tool comprising a metallic tool member provided with a working head, a jacket of insulating material enclosing said metallic member with the exception of said working head, a handle portion provided on said jacket, and a continuous annular shed on said insulating jacket between said handle and the exposed working head of said tool.

2. As an article of manufacture, an electricians insulated hand tool comprising a metallic tool having a working head and a metallic extension for manipulating said tool, an insulating jacket enclosing a metallic portion of said tool with the exception of the working head, a hand grip portion on said insulation jacket, and a plurality of annular sheds carried by said insulating jacket between the working head of said tool and the handle thereof to comprise surface insulating means.

3. As an article of manufacture, an electricians insulated hand tool comprising a metal tool member provided with a working head, a jacket of insulating material completely enclosing said metallic member with the exception of said working head, a handle portion on said jacket, and a plurality of insulating annular sheds encircling said jacket between said handle portion and said working head, said sheds being associated one with another to provide a plurality of annular rings with valleys between said rings to prevent the leakage of electrical currents over the surface of the insulating material from the working head to said handle.

4. As an article of manufacture, an electricians insulated hand tool comprising a metallic member provided with a working head, an insulating jacket enclosing said metallic member with the exception of said working head, a handle portion formed upon said jacket, and a plurality of annular sheds encircling said jacket between the handle portion and the working head, said sheds presenting re-entrant angles toward said working head.

5. As an article of manufacture, ajn electricians insulated hand tool comprising a metallic member having a working head, an insulating jacket molded around said metallic member to com pletely enclose the same with the exception of said working head, a handle on said insulating jacket and a plurality of insulating sheds formed on said jacket between said handle and said working head, said sheds comprising a principal shed presenting a re-entrant angle toward the said working head and a group of i e-enforcement sheds slightly separated from said principal shed.

6. As an article of manufacture, an electricians insulated screw driver comprising a metallic shaft having a screw driving head, an insulating jacket molded around said metallic shaft to completely enclose the same with the exception of said head, a handle portion on said insulating jacket, and a plurality of surface insulating sheds formed on said jacket between said handle portion and said working head, said sheds comprising a principal shed presenting a, re-entrant angle toward the said head and a group of re-enforcement sheds slightly separated from said principal shed.

7. As an article of manufacture, an electricians insulated hand tool comprising a metallic member provided with a working head, an insulation jacket enclosing said metallic member with the exception of said working head, a handle portion on said jacket, and a plurality of sheds on said jacket between said working head and said handle portion, said sheds constituting a surface insulating zone of equi-potential stress to provide an area of high surface insulation qualities between said working head and said handle portion.

8. As an article of manufacture, an electricians insulated screw driver comprising a metallic shaft provided with a screw driver head, an insulation jacket enclosing said metallic shaft with the exception of said head, a handle portion on said jacket, means to lock said shaft to said handle portion, and a plurality of sheds on said jacket between said head and said handle portion, said sheds constituting a surface insulating zone of equi-potential stress to provide an area of high surface insulation qualities between said head and said handle portion.

VICTOR A. RYAN.

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