Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a cixcular saw
with a riving knife, and particularly to such a saw comprising
a support plate and a saw~blade adjustable ln relation to the
surface thereof, for the purpose of adjusting the ~epth of
cut.
In the case of circular saws, it is known and
prescribed that the ri~ing knife (or spLitting wedge) be
arranged in such a manner that when the depth of cut is
adjusted, the said knife does not alter its position in relation
to the saw or to the highest point of the saw blade above the
support surface. If the depth of cut is altered by displacing
the saw housing and saw blade vertically in relation to the
support plata, then, in known circular saws, the riving knife
is secured to the motor-housing.
If, for the purpose of adjusting the depth of cut,
the motor-housing and saw blade are connected pivotably to the
support plate with a motor-carrier, then follow-up means must
be provided, in known fashion, for the riving knife, to guide
the latter as desired in relation to the saw blade.
Although the rivlngknife must normally be used to
protect the operator, it is sometimes necessary to remove it
for certain applications, for instance if the saw blade has
to be introduced into the surface of the workpiece for the
purpose of producing cut-outs in boards, or if, under certain
circumstances, it is necessary to saw backwards. In such
cases, the riving knife would interfere with the work and
must therefore be removed. As soon as the circular saw is to
be used again for normal work, the riving knife should be re-
lnstalled, but this is often forgotten, or neglected for the
sake of convenience, and the operator may thus be seriously
endangered and injured by rebounding workpieces.
It is therefore the purpose of the invention to
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arrange the riYing k~ife of a circu~ax s~ i~ such a m~p~er
that the sa~ hlade may be inserted inta thle woxkpiece, ox
the workpiece may be sawn baçkwards, without the necessity
of removing the riving knife.
According to the present inYention there is provided
a circular saw having a ri~ing knife, a saw blade having an
axis and adjustable in relation to a support sur~ace of a
base plate, and a follow-up device to provide positive pivot-
ing of the riving knife about the axis of the saw blade,
characterized in that the follow-up device has at least one
additional degree of freedom permitting the riving knife to
move in relation to its positive follow-up motion.
.
Thus, when the saw blade is inserted into the
workpiece, the riving knife is pivoted, preferably against
the action of restoring force, behind the support surface
and slides, during further sawing in the forward direction,
in the cut produced by the sa~ blade. This ensures that the
prescribed riving knife is in place during further sawing
operations, and that the operator aannot therefore be
endangered.
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According to one advantageous example of embodiment,
this additional degree of freedom may be produced in that the
length of the rocker which is not driven may be ~aried against
a restoring force. Provision may also be made for one bearing
of the articulated quadrangle to be made mobile.
A releasable locking device may be provided between
the riving knife and the circular saw. In the locked position,
- this device prevents free relative movement between the
riving knlfe and the highest point on the saw blade. This
eliminates the said additional degree of freedom, and the
riving knife maintains its position at the highest point on
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the saw blade. If a circular saw of this type is to be used
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for insert-woxk, the locking deYice must be released, to
allow the riYing knife to swing back behind the support plate.
- If, during further sawing, the said riving knife slides in
the saw-cut, provision may be made for the locking device to
engage automatically, in which case lt must be released again
for the next insert-work. Provision may also be made to
adjust the riving knife without any spring, weight, magnetic,
hydraulic, or the like restoring force, but manual operation
and locking in the terminal positions.
The riving knife according to the in~ention may be
used with advantage both for portable circular saws and for
stationary circular saws mounted on tables.
Examples of embodiment of the invention are described
hereinafter in greater detail, without any limi~ative manner in
conjunction with the drawings attached hereto, wherein:
Fig. 1 shows a portable circular saw, having a
riving knife according to the invention, in
part section;
Figs. 2-4 show diagrammatlc representatlons of
~0 three different examples of embodiment
of the riving knife according to the
invention with its follow-up device;
Fig. 5 is a section along the line V-V in Fig. 4;
Fig 6 is a section along the line VI-VI in Fig. 3;
Fig. 7 shows diagrammatically a table-mounted circular
saw having a riving knife according to the
invention and a follow-up device.
In the portable circular saw illustrated in Fig. 1,
with vertical adjustment of the depth of cut, a motor-housing
3 with a saw blade 4 is vertically displaceable in relation
to a base-plate (or support-plate) 1 having a support surface
2. A riving knife (or splitting-wedge) carrier 5, to which
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a riving knife (spiittin~ wedge) 6 is secured detachably, is
mounted pivotable upon motor-housing 3 aPd concentrically with
axis 7 of saw blade 4. Motor-housing 3 also comprise a stop
8 and a tension-spring 9 between the said stop 8 and riving
knlfe carrier 5, so that, in its posltlon of rest, the sald
carrier bears against the said stop. At this time, riYing
knife 6 assumes its position for normal sawing, with highest
polnt 10 of saw blade 4 projectlng a few mlllimetres beyond
the said riving knife.
If, for the purpose of sawing lnto the surface of
the workpiece (insert-sawlng), the portable clrcular saw is
now placed thereon wlth the blade rotating, then the saw blade
penetrates into the workpiece, but riving knife 6 is swung
back therefrom, against the action of tension spring 9, into
the positlon shown in dotted lines ln Fig. 1, to allow the
saw blade to enter into the workpiece untll support-surface
2 rests thereon. As the circular saw moves forward, riving
knife 6 slides, under the action of tension spring 9, in the
cut made by the saw blade, thus performing its prescribed
safety function.
Figs. 2 to 4 are diagrammatic representations of
portable circular saws having a pivotably mounted motor-carrier
and a follow-up device for the rlving knife, various examples
of the movement, according to the invention, of the riving
knife being shown. Rocker 15 of a motor-houslng 16 is
secured pivotally, in a bearing 13, 14, to a base (or support
plate) 11 with a support surface 12, for the purpose of adjust-
ing the depth of cut of saw blade 17. A riving knife carrier
19 is mounted pivotally upon motor-housing 16, and concentrical-
30 ly with axis 18 of saw blade 17, a riving knife 20 being
secured detachably to the said carrier 19. High-point 21 of
saw blade 17 again projects by a specific amount beyong riving
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knife 20.
Riving knife carrier 19 is in the form of a~
elbow-lever, ri~ing knife 20 being secured to carrier-arm
22 thereof, while the other arm forms a link 23. Attached
pivotally to hinge-point 24 of the said link is a rocker or
connecting rod, or balance arm 25 (Fig. 2) or 26 (Flgs. 4 and
5), the other ends of the said rockers being connected at
hinge-points 27, 28, 29 to support-plate 11.
The imaginary connecting lines between hinge-points
13-27, 14-28 and 13-29 form, in known fashion, in conjunction
with driven rocker 15, link 23 and additional non driven rocker
25, 26 an articulated quadrangle which, when motor-housing
16 is plvoted, for the purpose of adjusting the depth of cut
of saw blade 17, guides the riving knife 20 in such a manner
as to keep the pre-determined distance between high-point 21
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and the riving knife constant.
In order to achieve a further degree of freedom,
rocker 25, as shown in Fig. 2, has a sleeve 30 attached
pivotable to hinge-point 27. Mounted displaceably in the
said sleeve ls a rod 31, and a compresslon sprlng 34 ls
arranged between a plate 32 on rod 31 and end-wall 33 of the
said sleeve. Rod 31 is connected pivotably to hinge-point
24 and, in the position of rest, plate 32 is urged by spring
34 towards the other end-wall 35 of sleeve 30.
The arrangement according to the invention,
illustrated in Fig. 2, provides guidance (follow-up) for
riving knife 20 upon adjustment of the depth of cut. If the
circular saw is used for insert-sawing, riving knlfe 20 is
; swung away from the surface of the workpiece, against the
action of compression spring 34, into the position shown in
dotted lines in Fig. 2. After a saw-cut has been made,
compression spring 34 automatically guides the said riving
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knife in the said cut~
In Fig. 3, hiP~e-point 28 is not.attached.to
support-plate 11, but is connected pi~ota.lly, by ~eans of an
intermediate member 36, to bearing 14 secured to support-plate
11. A compression spring 37 is arranged between in.ter~ediate
member 36 and bracket 38 on.support-plate ll, the said sprin.g
urging the said intermediate member towards a stop-cam 39
on bracket 38. Again in this example of embodiment, rivin.g
knife 20 may be pivoted, during insert-sawing, towards support-
surface 12. After a saw-cut has been made~it returns auto-
matically to its position of rest.
As shown in Figs. 4 and 5, in these examples of ~.
embodiment hinge-point 29 is mounted in a curved slot 40 ~:~
. in a bracket 41 on support-plate 11. A shoulder-bolt 43 is
located in a hole 42 in rocker 26, the said bolt being ~.
displaceable in slot 40 and being adapted to be locked to
. bracket 41 by means of a wing-nut 44. In this example of
embodiment, the additional degree of freedom may be eliminated
~ by the operator, the mo~ement of the riving kn.i~e being
20 limited to the follow-up movement. When wing-nut 44 is loosened,
.; the displaceable arrangement of hinge-point 29 in slot 40 .
allows riving knife 20 to be swung towards support-surface
12 when saw blade 17 is used for insert-sawing.
Fig. 6 shows a modification of the design according ;
to Fig. 3. In this case, bearing 14 is in the form of a
double hinge-point, carrying both rocker 15 for motor-housing .
~: 16 and intermediate member 36. :
Intermediate member 36 is mounted upon a bearing
; bolt 45 whlch is rotatable in bracket 38. An adjusting wheel
47 is secured to the said bolt by means of a pin 46. Arranged
between adjusting wheel 47 and bracket 38 is a helical spring
48 which holds the said i~termediate ~ember, through bolt 45,
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in the position of rest shown i~ Fig. 3.
A lock-pin 50 is mounted displaceably in a hole
49 in adjusting wheel 47, the said pin ha~ing t~o grooves 51
in which a spring-loaded ball 52 engages. When lock-pin 50
is in the release position, adjusting wheel 47 may ~otate
freely, but when the said pin engages in a hole 53 in ~racket
38, the said wheel is locked thereto. In this case, the
additional degree of freedom of ri~ing knife 20 is again
` eliminated.
The use of the riving knife according to the
5' invention in a stationary, table-mounted circular saw is
shown in Fig. 7. Here again rocker 57 of motor-housing 58,
with its saw blade 59, is mounted pivotably on a bracket 54
on support-table 55. Riving knife 60 is secured detachably
~; to one arm of riving knife carrier 61, the other arm thereof
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forming link 62 of an articulated quadrangle which is
complemented by a rocker 63 corresponding to rocker 25 in
` Fig. 3. One end of rocker 63 is secured to hinge-point 64
on bracket 54, while the other end is secured to hinge-point
65 on link 62.
Stationary, table-mounted circular saws are usually
provided with a protective hood which may be secured pivotally
to the end of riving knife 60, but this hood must be removed
if the riving knife is to be used in accordance with the
invention. When a workpiece 66 is in position, riving knife
60 assumes the position shown in full lines in Fig. 7. When
the workpiece is removed, it returns to the position of rest
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shown in dotted lines.
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