US 1713972 A
Description (OCR text may contain errors)
MayZl, 1929. ,L,LUFK|N 713,972
HACK SAW FRAME Filed. March 2, 1928 avwento'c Jay/v JLuF/r/N Patented May 21, 1929.
I UNITED STATES PATENT OFFICE.
JOHN L. LUFKIN, or NEW YORK, N. Y.,,assrenon TO THE nneru'nnnme rnonuc'rs I conroanrron, me, on NEW YORK, N. Y., A CORPORATION or new YORK...
- Application filed March 2,
The invention is directed particularly to the providing of a hack saw frame or holder which can be safely and efficiently used in electrical work, though it may also be used 5 in other classes of work.
The accompanying drawings illustrate an embodiment of the invention.
Fig.'1 is a side elevation partly in section;
*Fig. 2 is an underside plan view F ig. 3 is an oblique plan showing the adjusting nut.
In electrical work, especially in cable cutting in underground manholes, the usual metal frame for hack saws is dangerous because of its electrical" conductivity. Such cable cutting is often done while the cables are alive with several thousand volts.
workmen use rubber gloves and they'sometimes wind the adjacent parts of the metal handle with rubber and use various other makeshifts to avoid accidental metal contact.
The present invention is designed particularly for this class of work. It provides a frame which is not only of an insulating character but has various other advantages referred to hereinafter. I
The back 1 of the frame is a fairlyheavy rectangular strip of wood having an outer end 2 extending downward and a hand-grip 3 eX- tending obliquely backward and downward. The portion between the back and the grip is provided with an upward projection 1 and a downward projection 5. The intermediate portion 6, which we may call the inner end of the frame, is diagonally bored to form a long square hole 7 and an enlarged round hole 8. A squared holder 9 lies in the portion 7 and has at its lower end a projecting portion 10 in which is fixed a backwardly bent pin 11 engaging a hole in the inner end of the blade 12. The outer end of the bladeholder 9 is threaded and engaged by a round nut 13 lying in the lower part of the recess 8 and slotted on its outer end for engagement by a screw driver some distance below the top of the opening. The opposite end of the blade 12 has a hole which is engaged by a hook 14 having a forward projection 15 lying in a slot 16 in the outer end 2 of the frame and having an upwardly bent end 17 which is driven into a recess in the holder and is barbed to prevent it moving downward out of the recess.
To insert a new The blade is turning up the nut 13. lade the nut is turned 1928. Serial 1x01258454;
backward to permit pulling the holder 9 downward sufficiently for the purpose.
The downwardly projecting outer end 2 of the frame is strengthened by a dowel 18 extending upward through the central portion. The frame is made of hard close-grained tough wood, such, for example, as ash. The grain of the wood extends lengthwise. It is then treated with a special filling and insulating hard varnish which serves two purposes. It prevents the wood from absorbing moisture or any of the liquids which are encountered and thus preserves its insulating quality. I H I The" hard varnishlargely prevents copper, iron orlead or other metal chips andparticles from becomingembedded in the wood, which would tend to provide a conducting medium.
The entire frame is: made of a single piece of wood of uniform lateral thickness of sufficient cross-section to provide a frame which is stiffer than the usual steel frame. Experionce shows that with such a frame there is less breakage of the saw blade when cutting strandedcables, where the strands sometimes bind and gripthe blade closely, than with the usual steel frame.
The downwardly inclined handle 3 provides a very effective grip in a direction which experience has shown gives the greatest strength to resist breakage under the strains which are encountered in use. The shoulders formed by the projections 4 and 5 at the forward end of the handle prevent the operators hands from slipping forward and coming into contact with the saw blade or the metal parts of the holder or the work. The depression of the butt 13 below the top surface of the holder also prevents accidental contact. The lower end 19 of the outer portion 2 of the frame projects below the far end of the blade. This and the underhang of the rear projection 5 protect the blade from accidental contact with adjacent cables and other metal parts within the manhole. The projecting part 19 particularly prevents the saw from being pushed so far as to make contact with an additional cable or the like. The cables are always arranged close together and it is important to avoid a metal contact between the cable which is being sawed and the one next beyond it.
Various other insulating materials than wood may be used for all or for parts of the frame; and the latter, though preferably made in a single piece, may be made of two or more pieces.
Various modifications may be made by those skilled in the art without departing from the invention as defined in the followingclaims.
What I claim is:
1. A hack saw frame made of wood cut away to form a back and projected ends with grain substantially parallel tothe back, a blade holding hook having a shank disposed at an angle to the hook portion and extended upwardly into a depending end of the frame and reinforcing the same.
2. A hack saw frame made of insulating material having a back and projected ends, and a blade holding hook located in a plane intermediate to extremity of said ends and said back, said hook having an angular shank portion which is embedded below the outer surfaces of said frame so as to avoid accidental contact with electric conductors. 3. A hack saw frame made of wood cut away to form a back and projected ends with grain substantially parallel to the back, a blade holding hook having a shank embedded in one of said ends and having its saw engaging portion in a plane intermediate the extremity of said one end and said back.
4. A hack saw frame made of wood cut away to form a back and projected ends with grain substantially parallel to the back, a blade holding hook having a shank embedded in one of said ends and a reinforcement dowel in the end carrying said hook.
5. A hack saw.frame made of a single piece of wood cut away to form a back, projected ends and a rearwardly and downwardly projecting hand-grip a holder lying in a recess in the frame and secured to one end ofrthe blade, the end of the holder to which the blade is secured lying between said projected ends, and an adjusting nut engaging the opposite end of said holder and located below the surface of the frame, and a blade holding hook having a shank embedded in one of the projected ends. 7 i
6. A hack saw frame made of a single piece of stock, shaped to form a back, projected ends and a rearwardly and downwardly projecting hand-grip, a holder lying in a recess in the frame and having its blade engaging end terminating between said projected ends and in a plane intermediate the extremity of said ends and said back. a
In witness whereof, I have hereunto signed my name.
JOHN L. LUFKIN.