Blade holders

The invention relates to a blade holder of the hacksaw type which comprises a C-shaped portion spanned by a blade having a conventional pair of projections being receivable in a slot having a cruciform or T-slot in one arm of the C-shape and the other pair in a similar slot formed in a lever pivotted to the other arm. Movement of the lever from a loading position to an operative position imparts tension to the blade and in the example shown, involves movement into an over-center condition of the lever with respect to its pivotal mounting. The lever has an abutment surface projecting outwardly from its end portion adjacent the pivotal mounting so as to contact the second arm member when the lever is in its loading position to thereby act as an end stop.

BACKGROUND OF THE INVENTION 
The invention is concerned with improvements in or relating to blade 
holders, in particular holders in which the blade is mounted to span a 
portion of the holder and held in position under tension. 
Blade holders of this type are conveniently used for saw-toothed blades and 
it is often only with difficulty that the blade is mounted across the span 
of the holder and secured in position. Such mounting frequently involves 
exerting manual pressure on the holder temporarily to reduce the length of 
the span while the blade is inserted. 
BRIEF SUMMARY OF THE INVENTION 
The invention provides a blade holder for use with a strip blade arranged 
to span a C-shaped portion of the holder and having an opposed pair of 
mounting projections provided at each of its two end portions, wherein the 
C-shaped portion comprises two arm members, a first arm member being 
provided with a T-slot to receive the projections of a first end portion 
of the blade and a second arm member being provided with a pivot mounting 
on which is mounted one end of a pivotal lever, said lever being provided 
with a T-slot inwardly spaced from its mounting and into which are 
inserted the projections of the second end portion of the blade when the 
lever is in a first, loading position, the construction and arrangement 
being such that movement of the lever from its first position into a 
second, operating position, causes the distance between the T-slot of the 
first arm member and the T-slot of the lever to increase, thereby enabling 
tension to be imparted to the blade. 
Advantageously, the movement of the lever into its second position involves 
the arcuate movement of the projections of the second end of the blade 
into an over-centre condition with respect to the pivot mounting of the 
lever, the arcuate movement of the blade being described about the 
projections of the first-end portion of the blade, received in the 
first-mentioned T-slot.

DETAILED DESCRIPTION OF THE DRAWINGS 
The Figures show a small blade holder of the kind sometimes known as a 
hacksaw. The holder comprises a handle 2 and a C-shaped portion 4 
comprising a first arm portion 6 and a second arm portion 8. A 
conventional blade 10 is illustrated, having a serrated edge 12 and two 
pairs of opposed projections, a first pair 14 provided at the first, 
upper, end (as shown in the Figures) and a second pair 16 at the lower 
end. 
A loading lever 18 is mounted at one end thereof on a pivotal point 20, for 
movement between a first, loading position shown in FIG. 1 and a second 
position in FIG. 2 in which it lies flush with the portion of the holder 
linking the arm 8 with the handle 2. 
The lever 18 has a finger-engaging free end portion 22 and, spaced slightly 
inwardly from its opposite end and the pivot point 20, a cruciform slot 24 
(more clearly shown in FIGS. 5 and 7) in grooves 26 of which are received 
the projections 16 of the blade 10. The entry into the slot 24 is 
facilitated by the provision of a projection 25 and the lever 18 which 
abuts a stop surface 28 of a recess 30 into which the lever is received in 
the operative condition of the saw. Abutment of stop surface 28 ensures 
that the lever is in the correct location to receive the lower end portion 
of the blade as it is pivoted into place about the projections 14. The 
projections 16 are held captive in the grooves 26 while the lever is moved 
manually into the position shown in FIG. 2 and thus tension is imparted. 
This is further explained below with reference to FIG. 4. 
In FIG. 4, the line AB represents the centre line of the blade 10 (between 
the projections 14 and 16) in the position shown in FIG. 1, that is, with 
lever 18 in its first position. Movement of the lever 18 about its pivot 
point 20 causes the point A (projection 16) to move to the position shown 
at C, which is "over-centre" with respect to the point 20. It will be 
observed that the distance BC is greater than AB and that therefore the 
desired degree of tension has been imparted to the blade 10.