US2899996A - Insulated screw driver - Google Patents

Description

INSULATED SCREW DRIVER Earle F. Stockman, Flushing, N.Y., assignor of one-half to Frank M. Nishio, New York, N.Y.

Application December 13, 1957, Serial No. 702,591

5 Claims. (Cl. 145 50) This invention relates generally to hand tools, and more particularly has reference to an electrically insulated hand tool, such as'a screw driver. Although hereinafter the invention will be described specifically with reference to a screw driver, it will be understood that it is applicable with equal facility and to equal advantage to any of van'- ous other hand tools.

The problem of electrically insulating a hand tool is a continually recurring one in various elds of work.. Electricians, particularly those who work on high voltage apparatus, must have insulated tools, to provide maximum safety. The mere provision of a handle of insulation material, such as plastic, is not sucient inmany instances, and it has, accordingly, heretofore been proposed to enclose the shank of the ytool in a comparatively thick, sleeve-like covering of electrically insulative-material that will have high dielectric characteristics, and will not break down except at very high voltages. Such materials are somewhat analogous to those used in electrically insulated conductors, and may include latex rubber, synthetic rubbers, plastics, and various resinous materials.

It has been found, however, that the mere coating of the exposed portion of a shank of a tool with a material of the character stated is not su'icient to provide maximum safety. At the point at which the insulation covering abuts the inner end of the tool handle, there is no protection, and furthermore, the portion of the tool shank that is embedded in the tool handle is not covered by the special insulation. Accordingly, other than the relatively minor insulating qualities of the handle itself, there is no protection at this location.

In view of the above, it is proposed to provide an improved hand tool, of the electrically insulated type, which will provide far more protection than tools previously insulated.

Another object is to so form the tool that not only will the exposed portion of the shank be covered with the special insulation, but also, there will be a portion of said insulation continuing directly into the tool handle itself, with this portion being embedded in an epoxy resin of high electrically insulative qualities. In this way, it is proposed to eliminate completely the point at which electrical insulation has heretofore not been provided, that is, the location at which the inner end of the insulative shank covering abuts the handle itself.

Another object is to provide a tool of the character described that will be formed in a manner to insure to the maximum extent a iirmembedding of the tool shank within the handle, in such a way that the epoxy resin that surrounds the insulated inner portion of the tool shank will not work loose from either the shank or from adjacentportions of the handle.

" nited States Patent O ice inner end portion of the shank, which material will have so close an ainity tothe material of the handle itself as to become, in effect, an integral part thereof when the manufacture of the tool is completed.

For further comprehension of the invention, and of the objects and advantages thereof, reference will be had to the following description and accompanying drawings, and to the appended claims in which the various novel features of the invention are more particularly set forth.

In the accompanying drawings forming a material part of this disclosure:

Fig. 1 is a longitudinal sectional view of a screw driver according to the present invention, shown partly in ele- Vation.

` tive View in which the tool has been inverted, showing the Yet another object .is to provide an electrically insulated manner in which the same is manufactured.

Fig. 7 is an enlarged, fragmentary longitudinal sectional view of a modification.

Fig. 8 is a transverse section on line 8 8 of Fig. 7.

Fig. 9 is a transverse section on line 9 9 of Fig. 7.

Referring to the drawings in detail, a handle 10 formed of plastic material is externally configured in any desired manner, and for example can have deep, longitudinally :extending grooves 12 uniformly, angularly spaced about the circumference of and vextending substantially the full length of the handle, to provide a good grip thereon. The inner end portion of the handle may 'be of reduced diameter and may have circumferentially extending ribs 14, said series of ribs 14 merging at the inner extremity in an annular flange 16.

An elongated axial recess 18 of the handle opens upon the inner extremity thereof, and snugly, txedly engaged therein is the inner end portion of an elongated shank of a screw driver bit 20. Shank 20, adjacent its inner extremity, has diametrically opposed, longitudinally extending, anchoring fins 22 xedly engaged in the material of the handle. n

In accordance with the invention, a frusto-conical or aring recess or counterbore'24 is formed in the inner end o-f the handle, communicating with recess 18. At its inner end, counterbore 24 is of a diameter slightly 'greater than the diameter of bit shank 20, so that a sleeve-like covering 26 of electrically insulative material may extend within counterbore 24 fully to the inner end thereof.

The covering 26 is of a material known in and of itself, and in accordance with the present invention, and appreciable part of the length of said covering extends directly into the handle, being seated within couuterbore 24.

Referring to Fig. 6, in the manufacture of the device, the handle is inverted as shown in Fig. 6 so that the counterbore opens upwardly, Then, liquid epoxy resin or a similar material of high electrically insulative qualities and readily molded, settable characteristics, is poured into the recess 18 and counterbore 24, as for example from a container C.y The container is illustrated merely diagrammatically, and the liquid resin would be poured into the recess from any suitable source.

In any event, when the resin has been poured into the recess, the inner end portion of the bit shank `is Vforced into the recess 18. As a result, the resin 28 will flow upwardly about the inner end portion of the shank, so

Y shank 20a.

3 Y A as to in effect line the bore 18, fully covering the handleembedded end of the bit shank. Movement of the shank to the recess 18 will cause some of the resin to be trapped in the inner end of the recess as shown in `Fig. l, so as to provide even more of a bond between the shank and handle. The rest of the resin will flow about the inner end portion of the covering 26, within counterbore 24, and excess resin will be wiped off or otherwise removed. Then, the complete unit is put into an oven to cure, and on hardening of the resin 28, a tool that is fully electrically insulated, and does not have any gaps 4that are not covered by electrical insulation of high substantially completely enclosing the outer end portion and extending over part of ,the inner end portion, and a material of high electrically-insulative qualities disposed within the handle and sealably encasing the part of the inner end portion of the shank that is enclosed by said covering, said recess of the handle extending axially thereof, the handle having a counterbore communicating with the recess, said material being disposed within said counterbore, said counterbore being of ared formation, said handle having diametrically. opposed locking -grooves communicating with the counterbore, for engagement of said material in the locking grooves, said handle having diametrically opposed longitudinal grooves formed in the Wall of said recess, said material filling the last-'named teristics communicating with an axial bore 18a of a j handle Litta.

in this arrangement, an even more effective lock of the tool shank within the handle is provided, with the locking action making use of the resin 2S. The resin 2S thus is firmly embedded both in the tool shank and in the handle, preventing loosening of the Vtool shank rela` tive to the handle. Further, the arrangement prevents loosening of the resinous filler 2S itself.

Accordingly, in this form of the invention there are diametrically opposed, narrow, deep grooves 32 communicating with counterbore 24a. Further, covering 26a at its inner end has a spiralling groove 30 opening into the counterbore. Still further, the inner end portion of the bit shank'has longitudinal grooves 34, in opposed relation to complementary grooves 36 formed in the wall of the recess 18a (see Fig. 8).

The manufacture or assembly is carried out in the same way as in the iirst form of the invention. rThe resin 28 when poured into the counterbore and recess 1891, will fill the same, and will ilov/ into the grooves 36 and 32. When the bit shank is forced into the handle, the resin will extend, key fashion, within the communieating grooves 34, 36, locking the shank to the handle (see Fig. 8) in cooperation with the ns 22a of the tool Further, the resin will flow into the grooves 32, locking the resin within the counterbore so as to prevent any accidental loosening of the same after curing.

While l have illustrated and described the preferred embodiments of my invention, it is to be understood that I do not limit myself to the precise constructions herein disclosed and that various changes and modifications may be made within the scope of the invention as defined in the appended claims.

Having thus described my invention, what'l claim as new, and desire to secureV by United States Letters Patent is:

l. An electrically insulative tool comprising a handle having a recess, a shank having an inner end portion engaged in said recess and having a work-engaging outer end portion projecting exteriorly of the recess, an electrically insulative Vcovering on said shank, said covering substantially completely enclosing the outer end portion and Vextending over part of the inner end portion, and a material of' high electrically insulative qualities disposed Within the handle and sealably encasing the part of the inner end portion of the shank that is enclosed by said covering, said recess of the handle extending axially thereof, the handle having a counterbore Vcommunicating with the recess, said material being disposed within said counterbore, said counterbore being of iiaredv formation, said handle having diametrically opposed locking grooves communicating with the counterbore, for engagement of said material in the locking grooves.

2. An electrically insulative toolV comprising a handle having a recess, a shank having an inner end portion engaged in said recess and having a work-engaging outer end portion projecting exteriorly of the recess, an electrically insulative covering on said shank, said ,covering grooves.

3. An electrically insulative tool Vcomprising a handle having a recess, a shank having an inner end portion engaged in said recess and having a work-engaging outer end portion projecting exteriorly of the recess, an electrically insulative covering on said shank, said covering substantially completely enclosing the outer end portion and extending over part of the inner ,end portion, and a material of high electrically insulative quaities ,disposed within the handle and sealably encasing ythe part of the inner end portion of the Vshank that `is enclosed by saidV covering, said recess of the Vhandle extending axially thereof, the handle having a counterbore communicating with the recess, said material being disposed within said t counterbore, said counterbore being of ared formation, said handle having diametrically opposed locking grooves communicating with the counterbore, for engagement of said material in the locking grooves, said handle having diametrically opposed longitudinal grooves formed in the wall of said recess, said material iilling the lastnamed grooves, said shank having longitudinal grooves in confronting, communicating relation to the grooves formed in the Wall of the recess, whereby said material will extend key fashion within the confronting grooves of the shank Vand handle. i Y Y 4. An electrically insulative tool comprising a handle yhaving a recess, a shank having an inner end portion engaged in said recess and having a work-engaging outer end portion projecting exteriorly of the recess, an electrically insulative covering on said shank, said covering substantially completely enclosing the outer endportion and extending over part of the inner end portion, and a material of high electrically insulative qualities disposed within the handle and sealably encasing the part of the inner end portion of the shank that is enclosed by said covering, `Said recess of Vthehandle ,extending axially thereof, the handle having acounterbore communicating with the recess, said material being disposed within said counterbore,` said counterbore being of ared formation, said handle having diametrically opposed locking grooves communicating with the counterbore, for engagement of said material Ain the locking grooves, said handlehaving vdiametrically opposed longitudinal grooves formed inthe wall of said recess, said material lling the last-named grooves, said shank having longitudinal grooves in confronting, communicating relation to the grooves rformed in the wall of the recess, whereby said material willV engaged in said recess and having a worloengaging outer end portion projecting exteriorly of` the4 recess,an elec-V trically insulative coveringl onf'said shank, said covering substantially completely enclosing* the outer .end I portion and extending over part of the inner end portion, fand a material of high electrically'insulative qualifies disposed within .the handle yand sealably encasingl thepart ofhthe` inner end portion of the shank that is enclosed by said covering, said recess of the handle extending axially thereof, the handle having a counterbore communicating with the recess, said material being disposed Within said counterbore, said counterbore being of flared formation, said handle having diametrically opposed locking grooves communicating with the counterbore, for engagement of said material in the locking grooves, said handle having diametrically opposed longitudinal grooves formed in the wall of said recess, said material filling the last-named grooves, said shank having longitudinal grooves in confronting, communicating relation to .the grooves formed in the wall of the recess, whereby said material Will extend key fashion within the confronting grooves of the References (Citedv in the le of this patent UNITED STATES PATENTS Y Wood Nov. 19, 1907 871,155 1,225,249 Holtschneider May 8, 1917 1,343,101 Weaver .Tune 8, 1920 1,902,438 Foley Mar. 21, 1933 1,946,239 Ryan Feb. 6, 1934

Images