Patent Application
20080028622
While the invention will be described with reference to a particular embodiment of the invention, it is understood that many modifications may be made thereto without departing from the full scope of the invention. Some particular modifications will be discussed herein while other modifications will be readily apparent to those skilled in the art.
Referring now to the drawing, there is seen in the various figures an embodiment of the invention in the form of a knife 10 having a blade 12 and a handle assembly 14. Blade 12 may be substituted with other types of tools as desired such as a hammer, screwdriver, file, or awl, for example. The tool or blade 12 is made of a strong metal material which by its nature is electrically conductive. An extension 16 connects to the blade 12 either as a separate or integral part thereof and is also made of a strong metal material which is electrically conductive.
The handle assembly 14 includes a handle grip 18 made of an electrically insulating material such as plastic or rubber, for example. The handle assembly 14 further includes an end piece for securing the handle grip 18 to the knife blade 12 via extension 16. The end piece may take a variety of forms and is preferably formed of a strong metal material which is inherently electrically conductive. In the embodiment of
As seen best in
Handle assembly 14 further includes an insert 26 made of an electrically insulating material such as plastic or rubber, for example. As seen best in
Insert 26 further includes a flange 26e which extends radially outwardly of central portion 26a. To provide a complete and uninterrupted electrically insulating barrier between butt cap 20 and blade 12 including extension 16 and coupling element 24, insert flange 26e follows the contour of and lies in complete covering relation to the surfaces of butt cap 20 which would contact handle grip 18 and extension 16. Referring still to
As stated above, it is important that handle assembly 14 be water-tight since water entering the handle assembly could create an electric path that bypasses insert 26 causing a shock to the user at butt cap 20 should blade 12 come into contact with a source of electricity. In this regard, the insert-butt cap interface geometry is provided with a plurality of discontinuous, interfacing surfaces to create a tortuous path between the exterior and interior of handle assembly 14. For example, to create this geometry, insert annular neck portion 20c may include a squared notch 20e which interfaces with a squared flange 26h of insert 26. This squared notch-flange interface alone has three discontinuous, interfacing surfaces. Another benefit of this squared notch-flange interface is that it provides a very secure fit between insert 26 and butt cap 20. A second squared notch-flange interface 27 may be provided adjacent head portion 26b, for example, for added bond strength between these parts. Other insert-butt cap interface geometries are of course possible.
In one embodiment, the insert 26 is molded into butt cap 20 which, combined with the notch-flange interfaces, creates an extremely secure bond between these two parts. During assembly, butt cap 20 is screwed onto threaded shank 24 and a sealant may be provided at the interfacing surfaces of insert 26 and handle grip 18a to further ensure a watertight seal between the exterior and interior of handle assembly 14.
A portion 18a of handle grip 18 is radially spaced from coupling element 24 (or extension 16 in an embodiment where the coupling element does not extend outwardly of the insert central bore 26c) to form an air gap 28 therebetween. Insert shoulder segment 26e radially spans air gap 28 such that air gap 28 is an enclosed space, being defined by shoulder segment 26e, handle grip portion 18a, extension 16 and coupling element 24. The handle grip portion 18a is made of a material which can absorb the shock (by flexing, for example) of a force applied to any part of knife 10 including the extreme impact force received when using butt cap pointed end 20a to break through glass, for example. With air gap 28 and handle grip portion 18a absorbing these shocks, the integrity of the handle assembly and seal between insert 26, handle grip 16 and butt cap 20 is protected through the expected rigorous use of knife 10.
While the invention has been described with reference to particular embodiments thereof, it is understood that various modifications may be made thereto without departing from the full spirit and scope of the invention as defined by the claims which follow.
