Note: Descriptions are shown in the official language in which they were submitted.
CA 02273584 1999-OS-28
1
ROTARY TRIMMER WITH FLEBIBLE BLADE GOARD
Related Applications
This application is based on and claims the
benefit of prior filed co-pending provisional
Application No. 60/087,081, filed May 28, 1998.
Field of the Invention
This invention relates to an apparatus for cutting
sheet material and more specifically to a paper trimmer
having a rotary cutting blade with a flexible blade
guard.
Background of the Invention
Sheet cutting devices, such as manually operated
paper cutters, find great utility in the home and
office, providing a user with the ability to make
precise, straight cuts on single or multiple sheets of
paper. Two types of paper cutters, the guillotine type
and the sliding-carriage type, are well known examples
of paper cutters currently in widespread use.
Guillotine-type cutters typically have a heavy
base with an extended surface area to provide support
for the paper being cut. A blade assembly having an
elongated cutting blade is mounted along one edge of
CA 02273584 1999-OS-28
2
the base. The blade is pivotally mounted to the base
at one of its ends and has a handle at the opposite
end. To operate this type of cutter, the blade is
grasped at the handle and pivoted upwardly away from
the base. Paper sheets are positioned on the base with
the portion to be cut overhanging the edge beneath the
blade. The blade is then pivoted downwardly by the
handle, engaging and shearing the overhanging portion
of the paper sheets.
While guillotine-type cutters are effective at
cutting relatively large numbers of sheets at one time,
the obvious safety hazard presented by a long exposed
cutting blade pivotally moving through a large arc
render this type of cutter dangerous to the user.
Careless use can result in serious injury or amputation
of a finger. Furthermore, guillotine cutters tend to
be relatively expensive, heavy and do not provide for
ready changing or sharpening of the cutting blade when
it becomes dull.
Sliding-carriage type cutters are also well known
and typically comprise a base having an extended
surface area for supporting the sheets to be cut. An
elongated guide rail positioned along one edge of the
base is pivotally mounted to the base at both its ends
and is movable from a position overlying the support
surface to a position spaced away from the support
surface. A carriage is mounted on the rail. The
carriage is slidable along the length of the rail and
holds a cutting blade, which could be a straight edge
or a rotary blade. The blade is mounted in the
carriage with its cutting edge parallel to the guide
rail. The cutting blade engages the support surface
CA 02273584 1999-OS-28
3
along a cut-line adjacent and parallel to the guide
rail when the guide rail is in the overlying position.
The sliding-carriage type cutter is operated by
pivoting the rail into the position spaced away from
the support surface. The sheet material to be cut is
then positioned on the support surface overlying the
cut-line. The guide rail is pivoted into its overlying
position, and the carriage is moved along the guide
rail where the cutting blade engages the sheet material
and severs it along the cut-line.
While the sliding carriage cutter marks a safety
improvement over the guillotine type cutter, the
cutting blade of the sliding carriage cutter still
presents a hazard. The blade is exposed when the rail
is in the position pivoted away from the base and can
cause injury when the device is handled or the user
accidently brushes against the blade. Furthermore, the
blade can also cut the user if the carriage is
inadvertently moved across a finger during the cutting
process.
Clearly, there is the need for improvements to
sheet cutters which eliminate the serious safety
hazards presented by both the guillotine-type cutter
and the sliding carriage cutter.
Summary of the Invention
The invention provides a blade guard for use with
a blade having a cutting edge for cutting sheet
material. The invention comprises a support for
mounting the blade with a portion of the cutting edge
extending from the support. A rim is yieldably and
CA 02273584 1999-OS-28
4
resiliently mounted on the support adjacent to the
cutting edge portion of the blade. The rim has a
surface portion extending beyond the cutting edge
portion, the rim resiliently yielding and exposing the
cutting edge portion for cutting the sheet material
when pressure is applied to the support forcing the
surface portion of the rim to engage the sheet
material.
Preferably, the blade is circular and has a
l0 circumferentially arranged cutting edge. A circular
rim is used in conjunction with a circular blade. The
surface portion of the circular rim is arranged
circumferentially of the rim and the rim is mounted
coaxially with the blade so that the rim surface
portion can be positioned adjacent to and extend beyond
the cutting edge portion of the blade.
The rim is supported on a circular hub mounted
coaxially with the rim on the support. Preferably, the
hub is rotatably mounted on the support. A plurality
of resiliently yieldable spokes are connected between
the hub and the rim for mounting the rim on the hub.
While there are many possible configurations for the
spokes, the preferred embodiment has three spokes
substantially equidistantly spaced around the hub, the
spokes extending from the hub to the rim in non-linear
paths, for example, in curved paths.
It is convenient to form the hub, rim and spokes
integrally from a plastic material having adequate
flexibility and elasticity to withstand constant
resilient yielding without permanently deforming or
breaking. BAYBLEND T G5 WN is an example of a plastic
CA 02273584 1999-OS-28
material suitable for fabricating the hub, rim and
spokes. The curvature of the spokes, the number of
spokes, the material from which the spokes are made, as
well as the cross-sectional properties of the spokes
5 all affect the relative flexibility of the rim.
The blade guard according to the invention is
conveniently used with a sheet cutting device
comprising a base having a surface for supporting the
sheets to be cut. The surface has a first edge
arranged along one side of the base along which an
elongated rail is arranged above the surface. The rail
is pivotally mounted at both ends to the base, enabling
the rail to move from a first position overlying the
surface to a second position away from the surface.
The blade support is movably mounted on the rail
and can slide lengthwise along it. A handle is mounted
on the blade support for manually applying a downward
force to the blade support and for manually moving the
blade support along said rail. The blade is preferably
circular and rotatably mounted on the blade support,
the blade having a cutting edge with a portion
extending from the support.
The rim of the blade guard is yieldably and
resiliently mounted on the support adjacent to the
cutting edge portion of the blade. As described above,
the rim has a surface portion extending beyond the
cutting edge portion. The rim surface portion engages
the sheet material supported on the surface beneath the
rail. The rim resiliently yields to expose the cutting
edge portion when the downward force is applied to the
support. Yielding of the rim exposes the blade
CA 02273584 1999-OS-28
6
allowing it to cut the sheet material when the blade
support is moved along the rail.
Brief Description of the Drawings
Figure 1 is a top plan view of a rotary trimmer
according to the present invention;
Figure 2 is a partial perspective view of the
rotary trimmer shown in Figure 1 featuring an exploded
view of the rail assembly and carriage assembly;
Figure 3 is an end view of the rail assembly and
l0 carriage assembly taken along line 3-3 of Figure 2;
Figure 4 is a cross-sectional view on an enlarged
scale of the carriage assembly taken along line 4-4 of
Figure 1;
Figure 5 is a sectional view of the carriage
assembly taken along line 5-5 of Figure 4;
Figure 6 is a sectional view on an enlarged scale
of the carriage assembly taken along line 6-6 of Figure
5;
Figure 7 is a detailed plan view of a component of
a blade guard according to the invention; and
Figure 8 is a partial exploded view on an enlarged
scale of components of the carriage assembly shown in
Figure 2.
CA 02273584 1999-OS-28
7
Detailed Description of he Preferred Embodiment
Figure 1 shows a manually-operated, sheet cutting
device 10 for cutting paper. Cutting device 10 has a
cutting board 12 having a generally planar support
surface 13 for supporting the sheet material to be cut.
Surface 13 is flanked by one or more raised edge
portions 11. For convenience, edge portions 11 display
indicia and scales lla allowing the user to position
the sheet material on surface 13 for precisely measured
l0 cutting.
As best shown in Figure 2, the edge portions 11
are raised slightly above the planar support surface
13. Accordingly, the edge portions 11 of the cutting
board proximate to the planar surface 13 provide two
parallel vertical abutment surfaces 29. The abutment
surfaces 29 are arranged perpendicularly to the line of
travel of the cutting blade (described below) allowing
the user to make a right angle cut when an edge of the
sheet material to be cut is abutted against the
abutment surface 29.
Figure 2 shows a rail assembly 14 comprising a
pair of rail supports 16 and 18, rail pivot pins 15 and
17 and a rail 20. Rail 20 is supported at both ends on
rail supports 16 and 18. The rail supports are
pivotally attached to cutting board 12 at respective
slots 19 and 21 by means of the pivot pins 15 and 17.
The pivot pins are coaxially arranged and define an
axis of rotation for the rail assembly which allows
pivotal movement of the rail assembly illustrated in
Figure 3. Rail assembly 14 is movable between a first
position overlying cutting board 12 (seen in solid line
CA 02273584 1999-OS-28
8
in Figure 3) to a second position away from the cutting
board (seen in phantom line).
The rail assembly 14 is mounted on one side of the
cutting board 12 with the rail 20 oriented lengthwise
perpendicularly to the planes defined by the vertical
abutments 29. Rail 20 defines the line of travel of
the cutting blade and a perpendicular arrangement of
the rail and the abutment surfaces ensures a right
angle cut when surface 29 are used to orient the sheet.
As seen in Figure 2, the rail 20 includes a head
20A, a web 20B and a flange 20C. The rail 20 is
suspended between the rail supports 16 and 18. In
order to provide stability to the rail, the preferred
embodiment of the rail supports include respective
notches 16A, 18A and end and side grooves 16B, 18B.
The notches receive the web 20B, and the end and side
grooves 16B, 18B receive the ends of flange 20C holding
the rail firmly in place.
As further depicted in Figures 1 and 2, a carriage
assembly 30 is slidably attached to the rail 20. The
carriage assembly 30 comprises a housing 32, a rotary
cutting blade 34, a blade support member 38 including a
spindle 48 and an actuating means comprising a handle
40.
The rotary cutting blade 34 has a
circumferentially extending cutting edge 34A and is
mounted for rotary motion on the spindle 48. The
cutting plane of blade 34 is oriented parallel to rail
20, which is perpendicular to the abutment surfaces 29.
CA 02273584 1999-OS-28
9
Carriage assembly 30 forms a support for mounting the
blade 34.
The housing 32 includes a front blade cover 32A
that is releasably attached to a rear blade cover 328
(described in detail below). A retainer plate 32C
having a finger 42 is located between the front and
rear blade covers. As seen in Figures 2, 4 and 5,
blade support member 38 is fitted to retainer plate 32C
and engages finger 42 with a bifurcated rear projection
39 which straddles the finger. Retainer plate 32C is
mounted onto rear blade cover 32B by means of holes 46B
in the retainer plate engaging pins 46A extending from
the rear blade cover 32B. Thus, the retainer plate
retains the blade support member 38 to the rear blade
cover 32B.
Figure 8 illustrates the attachment of front blade
cover 32A to rear blade cover 32B. A pair of tabs 50A
project from the front blade cover 32A. The tabs have
notches 50C and are designed to fit and interlock
behind ears 50B recessed within the rear blade cover
32B. Ears 50B are arranged next to locking slats 50D
which project inwardly of the rear blade cover. To
attach the cover portions, tabs 50A are aligned
adjacent to ears 50B. Upon relative clockwise twisting
movement of the two cover portions (as viewed from the
front blade cover), tabs 50A engage ears 50B until
notches 50C engage slats 50D on either side of the rear
blade cover 32B, thereby locking the front blade cover
32A to the rear blade cover 32B.
In the preferred embodiment, the front blade cover
32A has a substantially circular shape which enshrouds
CA 02273584 1999-OS-28
the cutting blade 34. A flattened portion 32D of the
front blade cover arranged along its lower part
adjacent cutting board 12 allows a portion 35 of blade
34 to project from the carriage 30 as best seen in
5 Figure 5.
The front blade cover 32A also supports the blade
34 laterally and prevents all but circular motion of
the blade as it cuts the sheet material. As seen in
Figures 4 and 8, the front blade cover 32A has a
10 circular boss 70 which extends inwardly toward rear
blade cover 32B and bears against the blade 34 to
prevent it from wobbling, thereby insuring a clean,
straight cut when the carriage is moved along the rail
and the blade engages the sheet material to be cut.
If the blade is damaged or becomes dull, it can be
replaced by twisting the front blade cover 32A
counterclockwise to disengage it from the rear blade
cover 32B, removing the old blade 34 by sliding it off
of the spindle 48, sliding a new blade onto the spindle
48 and locking the front blade cover 32A back on the
rear blade cover 32B by twisting it clockwise.
The rear blade cover 32B has a rail-hugging
raceway as shown in Figure 4 which slidably attaches
the carriage assembly 30 to the rail 20. The raceway
is formed by front and rear lips 68 and 66
respectively, which protrude from opposite sides of the
rear blade cover 32B toward each other. Rear lip 66 is
positioned between the head 20A and flange 20C,
proximate the web 20B. Front lip 68 is similarly
placed between head and flange on the opposite side of
the rail. The head 20A and web 20B are thus sandwiched
CA 02273584 1999-OS-28
11
between lip 66 and lip 68 forming the raceway. The
lips provide stability for the carriage assembly 30 and
prevent all motion of the carriage except sliding
motion lengthwise of the rail.
In the preferred embodiment, rail 20 is made of
aluminum and the housing 32 is made of a polymeric
material. In order to reduce the friction between the
carriage assembly 30 and the rail 20 (as the carriage
assembly is moved in a translational direction along
the rail), a ball and spring arrangement, illustrated
in Figure 6, is used. The rear blade cover 32B
includes a pair of wells 60 on its outer surface.
Guide springs 62 are placed in the bottom of each well
60 for urging a ball bearing 64 against the web 20B.
A ring 60A at the top of each well (or a slight
deformation made at the top of each well 60 during the
manufacturing process) secures the ball bearing 64 and
guide spring 62 in each respective well to facilitate
the attachment of the carriage assembly to the rail
assembly 14. A portion of each ball bearing 64
protrudes above the well 60 and contacts the web 20B of
the rail 20, thus, reducing friction between the
carriage assembly 30 and the rail 20.
In the preferred embodiment, the actuating means
(see Figures 1 and 2) consists of a semi-circular
handle 40 attached to the blade support member 38.
Handle 40 allows an operator to manually move the
carriage assembly 30 and rail assembly 14 between the
positions illustrated in Figure 3. The shape of the
handle also promotes the translational movement of the
carriage along the rail. By pushing and pulling the
CA 02273584 1999-OS-28
12
handle 40, the carriage assembly 30 can readily be made
to travel lengthwise along the rail assembly 14.
The positioning of the rail assembly along one
side of the cutting board promotes access to the blade
by an operator. As seen in Figure 3, the rail assembly
14 rotates away from the cutting board 12. The
operator can easily twist off the front blade cover 32A
to access the underlying blade 34, if it needs to be
replaced.
Referring to Figures 2 and 4, a self-healing
sacrificial mat strip 71 is placed in a channel 72 of
the cutting board 12 underlying the path of travel of
the cutting blade 34. The mat strip prevents damage to
the cutting board 12 during the cutting process. The
strip 71 has a tacky or lightly glued side which
secures the strip to the cutting board 12. The strip
71 is easily replaced if it is damaged or worn out.
Figure 2 shows an exploded view of the carriage
assembly 30 with blade guard 100. Blade guard 100, as
shown in detail in Figure 7, comprises a rim 102
supported on three curved flexible spokes 104 emanating
from a central hub 106. Guard 100 is preferably made
of a high quality plastic material having adequate
flexibility and elasticity allowing rim 102 to
repeatedly flex and deflect resiliently on the spokes
104 when a force is applied but to always return to a
round shape concentric with cutting edge 34A of blade
34.
As best illustrated in Figure 8, blade guard 100
is rotatably mounted on housing cover 32A. Central hub
CA 02273584 1999-OS-28
13
106 is sized to accept boss 70 which projects inwardly
from housing cover 32A toward blade 34. The cross-
sectional view shown in Figure 4 depicts boss 70
interfitting within hub 106 which allow the guard 100
to rotate freely about the same axis as the blade 34.
Figure 5 shows a side view of a section through
housing 32 which illustrates the relationship between
guard 100 and blade 34. A portion 35 of blade 34
extends from housing 32 and rim 102 overlies and
extends beyond cutting edge 34A of this extended blade
portion in adjacent relation. A portion of guard 100
is shown in phantom line to indicate that it is behind
blade 34 when seen in this view.
In operation carriage assembly 30 is pivoted
upwardly on rail 20 as seen in phantom line in Figure
3. This allows paper to be placed on support surface
13, a portion of the paper to be cut beneath rail
assembly 14 and overlying mat 71.
With the housing pivoted upwardly blade 34 would
otherwise be exposed and present a potential cutting
hazard, however, blade guard 100 is in position on boss
70 with rim 102 adjacent to and extending beyond
cutting edge 34A. Rim 102 effectively prevents
accidental contact between the operator's fingers and
blade 34, thereby preventing injury. If a finger does
contact the guard with sufficient force to deflects it
such that the finger contacts the blade, the contact
force between the finger and the blade is spread out
over the larger surface area of the rim thus the guard
100 continues to prevent the blade from injuring the
operator.
CA 02273584 1999-OS-28
14
The rim 102 is supported by the spokes 104 with
sufficient stiffness to prevent the blade from making
an unintentional cut, however, the spokes are also
flexible enough to allow the rim to deflect radially
away from the cutting edge to expose the blade for
cutting when sufficient force or pressure is applied to
handle 40.
Intentional cuts are made by rotating carriage
assembly 30 into the position away from board 12, as
seen in phantom line in Figure 3, and placing sheet
material to be cut on surface 13 overlying mat strip
71. Carriage assembly 30 and rail assembly 14 are then
rotated into position overlying board 12 as seen in
solid line in Figure 3. With the carriage positioned
as far to one end of the rail as possible, the rim 102
will rest on mat 71 with the exposed portion 35 of
cutting edge 34A displaced slightly above the mat.
Force or pressure is manually applied to handle 40,
forcing the blade downwardly and sliding carriage
assembly 30 along rail 20. As rim 102 of the blade
guard encounters sheet material to be cut the rim
deflects on flexible spokes 104 into a non-circular
shape, exposing the portion 35 of blade cutting edge
34A which engages and cuts the sheets on the cutting
board. Blade guard 100 rotates as necessary with hub
106 turning on boss 70 to ensure smooth operation.
Once the cut has been completed and pressure on the
handle released, rim 102 resiliently returns to its
circular shape extending beyond edge 34A, again
providing protection against inadvertent cuts.
Even though particular embodiments of the present
invention have been illustrated and described herein,
CA 02273584 1999-OS-28
they are not intended to limit the invention. It is,
therefore, to be understood that modification and
variation of the embodiments described herein may be
made without departing from the spirit or scope of the
5 present invention.
