US 2525414 A
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Description (OCR text may contain errors)
1950 w. e. KLEINSCHMIDT 2,525,414
WORK ILLUMINATING TOOL HANDLE -Filed June 15, 1946 z; a L
1N VEN TOR.
Patented Oct. 10,
UNITED STATES PATENT OFFICE 2,525,414 WORK ILLUMINATING TOOL HANDLE Willard G. Kleinschmidt, Milwaukee, Wis. Application June 15, 1946, Serial No. 676,876-
This invention relates to an improvement in work illuminating tool handles.
It is a primary object of the invention to provide means whereby a well defined spot of light may be delivered from a tool handle to a working surface therebeneath without obstruction by shadows caused by the means used to support the tool from the handle.
Another object of the invention is to provide a novel and improved tool such as a screw driver or the like having an easily controlled source of illumination built into a handle which is an electrical non-conductor of transparent material, preferably a plastic.
In the drawings:
Fig. l is a view in longitudinal section through a screw driver handle embodying the invention.
Fig. 2 is a view of the complete screw driver in side elevation.
Fig. 3 is a view in side elevation showing the removable light and battery assembly.
Fig. 4 is a fragmentary detail view in perspective showing a screw and a fragment of a screw driver and illustrating the manner in which the work is illuminated by a screw driver handle made in accordance with the present invention.
Fig. 5 is a fragmentary detail view in section similar to Fig. 1 showing a modified embodiment of the invention.
While the invention is applicable to a wide variety of tools, it is particularly serviceable as applied to the handle 5 of a screw driver 6, preferably having a knurled shank at l engaged in the handle. V
The handle 5 comprises a transparent body of glass or clear plastic such as polystyrene, a suitable phenolic material, or methy1 methacrylate, for example. Within the handle is a centrally disposed, conically tapered surface 8 at the end of a light chamber 9 in which the lamp in is positioned. In practice, I have found it desirable that the taper of the conical surface 8 should be of the order of approximately 21 with reference to a transverse plane normal to the axis of the handle. It is possible to vary the angularity of a few degrees plus or minus, but I have found that if the taper is as much as 30 the light will emerge from the side of the handle rather than the end thereof.
While it is broadly unimportant how the lamp it is mounted, I have found it desirable to mount the lamp by means of a socket shell I I into which it is threaded. The socket shell is mounted in a carrier l2 seated against the shoulder it at the end of chamber 9. The carrier [2 and shell ll are preferably made of electrically conductive material.
The counterbore I4 is sufficiently larger than the dry cell battery l5 to accommodate a light compression spring it, the end of which is coiled about the battery and the opposite end of which is engaged in the groove i! in the lamp carrier 52.. The bias of this spring normally serves to keep the battery contact I8 and the central light contact l9 separated. However, the closure 20 which is screwthreaded into the rear end of the handle, and socketed at 2| to receive the end of the battery, may be rotated to advance the battery axially until its contactv l8 engages the lamp contact l9, thereby completing a circuit to the lamp l0, and returning to the battery through the shell I l, carrier l2 and spring l6.
Where it is desired that the plug at the end of the handle be seated firmly to take pressure of the operators palm, theplug 2!! may be used as shown in Fig. 5, such plug being shouldered to engage the end of the handle body 5. For moving the battery into operative contact ,with the lamp terminal against the compression of the spring IS, a separate screw 21 having a knurled end 28 disposed in a recess 29 of the handle may be employed. The screw preferably has an enlarged head 39 engaged with the bottom of the battery. Since the plug '20 is-not concerned either with light transmission or electrical conductivity, it may be made of metal, if
In either construction, removal of the plug 20 or 20' permits the battery and the spring and the carrier l2 and the lamp to be removed as a unit from the cavity in the handle. The connection of the spring about the battery facilitates such removal and is therefore preferred to any other means of completing the return side of the circuit. The spring E5 is contractile about the zinc or other metallic case which forms the outer electrode of the dry cell l5. It holds securely against the relative axial displacement but permits the ready release of'the battery for replacement purposes when the battery is retated with respect to the spring. In both constructions, the movement of the battery as a whole serves as a switch, the battery being moved by the compression spring iii in an outward or switch opening direction and. being moved by the plug 20 or the set screw 2'! in a circuit closing direction.
The purpose and effect of the conically tapered surface at 8 is to function like the surface of a lens or circular prism to throw outwardly the light from lamp In which would otherwise encounter the end of the shank of the tool. By reason of this bevel, the light enters the plastic composition of the handle in the form of a cone, the light diverging until it strikes the tapered surface 25. In practice, this surface has an angle of approximately 8 or 9 degrees inwardly from the grip portion of the handle. In any event, the angularity of the surface 25 should be below the socalled critical angle at which the light would emerge laterally from the handle. Thus, the light will be confined in the plastic instead of emerging therefrom.
Surrounding the tool 6 is a bevel 26 which, in practice, has an angle of approximately 60 from a transverse plane normal to the aXis of the handle and tool. With the other proportions 'substantially as indicated in the drawing, it is found that the light of lamp 9 will almost entirely emerge through the beveled surface 26 and will pass convergingly toward the work surface at which the tool is to be used, thus creating'a well defined and relatively brilliant spot of concentrated light immediately around the end of the tool when the lamp I is energized.
This result is achieved by reason of the fact that the light is transmitted through handle portions which provide a path of approximately uniform length and within which the light is confined and guided and concentrated for delivery to the surface 8, the taper of the handle at 25 being insufficient to permit the light to escape. Since the portions of the handle which pipe the light to the delivery surface are the same portions which provide mechanical support for the tool, as represented by screw driver 6, it will be apparent that no shadow is cast.
For different lengths of tool shank, different angles of light receiving and light emitting surfaces may have to be employed to focus the light on the work as desired. The principles involved are well known to those skilled in optics and the angles specified are given merely by way of example of one operative arrangement. In the device using the angles specified, the total width of the light receiving bevel is A; inch, while the total diameter of the lamp chamber 9 is g2 of an inch. The light receiving bevel 8 is spaced 1%; inches from the socket in which the tool shank is disposed. The overall diameter of the handle is 1 inch. The length of its tapered portion 25 is 1 inch and a quarter and the diameter of the conical light emitting surface 26 is of an inch. The tool shank socket happens to be of an inch.
As above noted, total refraction is achieved in this arrangement and substantially all of the light of the lamp is concentrated in a spot at the workin zone at the operative end of the tool.
In a lamp-illuminated tool handle for a tool such as a screw driver provided with a shank, a light transmitting body of generally circular form in cross section having an axial tool-shank receiving bore, said body being provided in axial alignment with said bore with a conical light receiving surface of approximately a 21 angle with respect to a plane normal to the handle axis, the said surface being disposed in immediate proximity to the said lamp to receive light therefrom and t0 refract the light rays within said body, the said body also being provided around said bore with an annular frusto-conical surface at an angle not to exceed approximately from a transverse plane normal to the axis of the handle and tool, said surface refracting and directing light rays emanating from said body convergently along said axis, the wall of said bore closely engaging the shank of the tool throughout the portion of the tool received in said bore, the surface of the body disposed between said conical light-receiving surface and said firstmentioned annular frusto-conical surface being annular and frusto-conical and tapering inwardly toward the first-mentioned frusto-conical surface at an angle less than that at which light would emerge laterally from the said last-mentioned frusto-conical surface of the body.
WILLARD G. KLEIN SCHMIDT.
REFERENCES CITED The following references are of record in the file of this patent;
UNITED STATES PATENTS