IMPROVEMENTS IN SAWING MACHINERY
Year: 1884

page_text: f. I FRIEDRICH WILHELM HOFMANN, Constructor of Mills of Berliner Chaussée,
Breslau, Prussia, German Empire do hereby declare the nature of the said'
invention for "IMPROVEMENTS IN SAWING MACHINERY" to be as follows:-
=
This invention relates to improvements in sawing machinery the object being to
effectually prevent the points of the teeth of the saw from coming against the
bottom of the saw cut as the saw moves backwards that is to say during the
time the saw is not cutting. According to my invention the guides of the saw
frame are caused to move slightly backwards in the direction of advancement of the
material being cut.
For this purpose instead of the fixed guides at present in use I employ moveable
guides which when the saw is cutting move in the direction of the advancement of
the material so that the teeth of the saw will cut, and which move backwards
when the saw moves backwards so that the teeth can move freely in the saw cut
and the saw-dust drop from the cut.
The advantage of having moveable guides is firstly that it allows of employing
teeth of the form shewn in figure 6, of the accompanying drawing instead of
triangular teeth as shewn in figure 5 and as generally employed up to the present
time which do not cut the wood so. well-but-tear.or. force it, the former teeth
cutting the wood and requiring much less motive power and allowing a quicker
advancement of the timber and whereby a greater quantity of work is effected.
The suspension of the guides on the saw frame can be effected in various ways such
as by means of levers or their equivalents or by horizontal or oblique guide ways
as shewn in the accompanying drawing.
I employ by preference the arrangement shewn in figures 1 to 4 which arrange-
ment in this case is applied to a set of sawa.
The frame A which receives the saw in the usual way slides in lateral
guides B which are not fixed to the frame as has hitherto been the case but are
suspended on levers a, and a', fixed on moveable parallel shafts b, b', connected
one with the other by levers c, and c³, and a connecting rod d, and are suitably
carried in bearings on the saw frame so that the material can freely advance. By
revolving the shafts the two guides with the frame A, sliding up and down in the
guides can be moved so that the points of the teeth of the saw can move back from
the bottom of the saw cut when the saw moves upwards. The rotation of the

page_text: parallel shafts b, and b, can be effected from the main shaft by an eccentric or cam.
In the arrangement shewn in the drawing an eccentric e, is employed acting on a
crank lever, which operates by means of a connecting rod a lever g, fixed on one
of the parallel shafts b.
In order to regulate the extent of the backward movement of the guides of the
saw frame according to the nature of the wood the lever g, may be provided with
several holes or with a slot in which slides a piece which can be fixed by means of
a set screw and on which acts the connecting rod of the eccentric e.
In the arrangement shewn in figure 7, the guides B are suspended at two fixed
points by two single hinged lovers a, and a', which are also operated from the
main shaft by camis or eccentrics so that at the end of the downward. movement
the guides will have already moved backwards, disengaging the points of the teeth
for the upward movement of the saw.
Instead of suspending the guides of the frames on levers, slide ways can be
employed applied to the frame and which allow of a displacement of the saw frame
in the direction of the advancement of the block.
In figure 8 for example these slide,ways are, shewn oblique and the backward
movement of the saw frame guides g, is effected by lifting the slide ways.
In figure 9 horizontal slide ways are employed and in this case the saw frame
guides are moved by an arrangement of levers similar to that shewn in figures 1
to 4.
The hereinbefore described arrangements as well as the modifications of the
moveable guides may be applied as well to horizontal as to vertical saw frames.
It is preferable to effect the advancement whilst the saw is cutting but it can
also be effected in a continuous manner.

page_text: COMPLETE SPECIFICATION.
I FRIEDRICH WILHELM HOFMANN, Constructor of Mills of Berliner Chaussée;
Breslau, Prussia, German Empire do hereby declare the nature of the said
invention, for "IMPROVEMENTS IN SAWING MACHINERY" and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement :-
This invention relates to improvements in aawing machinery the object being to
effectually prevent the points of the teeth of the saw from coming against the
bottom of the saw-cut as the saw moves backwards, that is to say, during the time
the saw is not cutting. According to my invention the guides of the saw frame
are caused to move slightly backwards in the direction of advancement of, the
material being cut.
For this purpose, instead of the fixed guides at present in use, I employ moveable
guides which, when the saw is cutting, move in a direction opposite to that of the
advancement of the material so that the teeth of the saw will cut, and which move
backwards when the saw moves backwards so that the teeth can move freely in the
saw cut and the saw-dust drop from the cut.
In order to enable my invention to be fully understood I will describe the same
by reference to the accompanying drawing.
The advantage of having moveable guides is, firstly, that it allows of employing
teeth of the. form shewn in figure 6, of the accompanying drawing.instead of
triangular teeth (as shown in figure 5 and as generally employed up to the present
time) which do not cut the wood so well but tear, or force it, the former teeth
cutting the wood and requiring much less motive power and allowing a quicker
advancement of the timber and whereby a greater quantity of work is effected.
The suspension of the guides on the saw frame can be effected in various ways such
as by means of levers or their equivalents or by horizontal or oblique guide ways
as shewn in the accompanying drawing.
I employ by preference the arrangement shewn in figures 1 to 4 which arrange-
ment in this case is applied to a set of saws.
The frame A which receives the saw in the usual way slides in lateral guides B
which are not fixed to the frame as has hitherto been the case but are suspended
on levers a, and a¹ fixed on moveable parallel shafts b, b¹ connected one with the
other by levers c, and c¹, and a connecting rod d, and are suitably carried in bearings
on the saw frame so that the material can freely advance. By revolving the shafts
the two guides with the frame A, sliding up and down in the guides can be moved
so that the points of the teeth of the saw can move back from the bottom of the
Baw-cut when the saw moves upwards. The rotation of the parallel shafts b, and b',
can be effected from the main shaft by an eccentric or cam. In the arrangement
shown in the drawing an eccentric e, is employed acting on a crank lever f, which
operates by means of a connecting rod a lever g, fixed on one of the parallel
shafts b.
In order to regulate the extent of the backward movement of the guides of the
saw-frame according to the nature of the wood the lever g, may be provided with
several holes or with a slot in which slides a piece which can be fixed by means of
a set screw and on which acts the connecting rod of the eccentric e:

page_text: In the arrangement shewn in figure 7, the guides B are suspended at two fixed
points by two single hinged levers a, and al, which are also operated from the main
shaft by cams or eccentrics so that at the end of the downward movement, the
guides will have already moved backwards, disengaging the points of the teeth for
the upward movement of the saw.
Instead of suspending the guides of the frames on levers, slide ways can be
employed applied to the frame and which allow of a displacement of the saw-frame
in the direction of the advancement of the block.
In figure 8 for example these slide ways are shown oblique and the backward
movement of the saw frame guides g, is effected by lifting the slide ways,
In figuro horizontal slide ways aro employed and in this case the saw
frame guides are moved by an arrangement of levers similar to that shewn in
figures 1 to 4.
The bereinbefore described arrangements as well as the modifications of the
moveable guides may be applied as well to horizontal as to vertical saw frames.
It is preferable to effect the advancement whilst the saw is cutting but it can also
be effected in a continuous manner.
Having now particularly described and ascertained the nature of the said
invention and in what manner, the same is to be performed I declare that what
I claim is
1. In sawing machinery the adjustable movable guides B for the saw frame A
the said guides working at right angles to the movement of the saws in order to
disengage the points of the teeth when the saw is travelling back, and to clear the
saw-dust and shavings out of the way of the saw substantially as hereinbefore
described and represented in the accompanying drawing.
2. Suspending the movable guides of the saw frames to the levers a and á¹ of
the parallel shafts b, and b' which are .connected by means of levers o' and cl, and
rod d having an oscillating movement so as to draw the saw on its backward
movement away from the Block substantially as described and shown in figures ]
to 4 of the drawing; or instead of the said suspension, the arrangement herein-
before described and represented in figures 7, 8, and 9 of the drawing.