Note: Descriptions are shown in the official language in which they were submitted.
CA 02231259 1998-03-06
1
SAFETY SLABBING KNIFE
The present invention relates to a hand held cutting implement and in
particular a knife
for stabbing rolls of paper stock.
BACKGROUND OF INVENTION
Paper malting and converting machines typically handle large quantities of
paper on
large rolls. There is frequently a need to remove an outer layer of paper from
the roll.
For example, paper rolls can suffer damage to their edges during handling.
This damage
is usually removed before the paper is rewound on customer sized rolls or
before being
delivered to a sheeter. In addition, paper breaks, splits or other damage that
can occur
as the papE~r web is delivered to t:he winder are routinely flagged in the
roll edge and
latter stabbed off the roll as it is being rewound or delivered to a
converting or printing
1 S operation. Moreover, the layers of paper close to the core of the roll are
usually curled
too tightly to be used and are dabbed off the core and repulped.
The current: industry standard tool for stabbing paper rolls is what is known
as a broke
knife. A broke knife resembles a large standard utility knife and uses a
replaceable
triangular blade. In use, the broke knife is usually held in a clenched fist
with the blade
depending from the bottom of the hand with the cutting edge facing forward.
The
worker walks along the longitudinal length of the paper roll (which can
measure up to
about 60 feet) pushing the broke knife forward through the paper. This
orientation and
action is required in order to achieve the high hand pressure required to be
exerted to
:25 advance the blade through the paper and to cover the entire width of the
roll in a
uniform raf>id cut. The broke knife has a number of deficiencies which lead to
a high
incidence of accidental injuries. Stabbing a %4" to 1" layer of paper requires
a substantial
amount of force to maintain the blade in full depth engagement in the paper
roll and to
advance the blade through the paper. This can quickly lead to fatigue in the
hand or
a0 wrist with the result that the blade can come out of contact with the paper
and expose
the worker's free hand and other body parts to severe injury. Chronic wrist
and elbow
CA 02231259 1998-03-06
2
damage similar to carpal tunnel syndrome and tennis elbow have also been
reported by
workers wllo repetitively slab paper rolls with a broke knife. Because of the
high force
required to advance the broke knife through the paper, blade breakage is
common
leaving a blade fragment projecting out of the paper roll on which a worker's
hand or
forearm can be accidentally cut. In addition, because the broke knife is used
as a free
hand tool, the depth and angle of= cut can be inconsistent, depending on the
worker's
expertise and fatigue level. Because the broke knife blade is fixed in the
operative
position, the worker is constantly at risk of injury from the exposed blade
merely in
carrying and handling the broke knife.
It is known to provide a knife with a spring loaded blade guard which can be
retracted
into the knife handle assembly when the blade is advanced into the workpiece.
One
example of such a knife is the Safety Carton Opener manufactured by The OLO
Corp.
of White Plains, New York. This device is intended for opening a carton by
cutting the
lid therefrom. The device employs a hollow handle assembly shaped to fit in
the palm
of the hand. A blade projects from the bottom surface and is shielded by a
retractable
blade guard. While the use of the blade guard greatly reduces the chance of
injury when
the knife is not in cutting position against the workpiece, the knife is not
suitable for use
as a slabbinl; knife. In particular, the OLO knife is configured to be used as
a draw knife
:ZO which is unsuitable for a slabbing application. Due to the high pressure
that must be
exerted to drive the knife through paper at full blade depth, and the
requirement to walk
across the longitudinal width of the paper roll, the dabbing operation
requires that the
knife be pushed in front of the worker. Moreover, while the OLO knife is
fitted with a
button to permit the blade guard to be retracted into the handle, the button
is actuated
1.5 by finger-tip action while gripping the knife handle. Such an arrangement
is not
optimal for use in a knife assembly that is configured to be pushed through
the
workpiece b;y the palm of the hand. Finally, the OLO knife has a sole plate
that is angled
to receive the upper edge of the carton to be cut and accordingly is
unsuitable for use on
the surface of a paper roll which, while cylindrical in shape, is
substantially planar in the
30 immediate vicinity of the cut line.
CA 02231259 1998-03-06
3
Accordingly, there is a need for a knife which employs a releasably
retractable blade
guard and is suitable to be advanced through the workforce at relatively high
pressures
by a pushing motion.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a hand held
cutting tool for
advancing; a blade through a workpiece with a pushing motion comprising a
generally
planar base member for sliding engagement with the workpiece, a cutting blade
extending down from the base member, a movable blade guard resiliently biassed
to a
first lower position in which said cutting blade is covered and movable to a
second
upper position in which said cutting blade is exposed, a handle member
extending
upward from the central portion of the base member, said handle member adapted
to
be gripped in the hand and having a rearward facing boss portion adapted to be
received in the palin of the hand and transmit a pushing force therefrom, a
latch means
for releasably securing the blade guard in the first lower position, said
latch means being
disposed on said boss portion of said handle and located so as to be actuated
by said
gripping action. The base member can extend laterally about said blade a
sufficient
distance to constitute an effective barrier 'preventing the thumb and fingers
from
contacting said blade when gripped and can include a rearwardly projecting
plate for
supporting the base of the palm when gripped. The latch means is preferably
located
so as to be actuated by the base of the thumb when gripped and the handle
member
preferably has opposed side walls adapted to be squeezed between the thumb and
fingers when gripped.
CA 02231259 1998-03-06
4
BRIEF DESCRIPTION OF THE DRAWINGS
FIG.1 is a right side elevation of the safety Blabber knife in accordance with
the present
invention.
_S
FIG. 2 is rear elevation of the safety slabber knife in accordance with the
present
invention.
FIG. 3 is a bottom view of the of the safety slabber knife in accordance with
the present
invention..
FIG. 4 is a an elevational view of the inside of the right half of the body
portion of the
safety Blabber knife in accordance with the present invention.
FIG. 5 is a side view of the safety Blabber knife in accordance with the
present invention
showing how it is held in the hand during use.
L>ETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Figures 1 and 2, there is shown a right side elevation of the
safety Blabber
knife in accordance with the present invention. The knife comprises a body
portion
generally indicated by reference numeral 2 which includes base member 4 and
handle
portion 10. Body portion 2 is hollow being formed of left and right halves 3
and 5 joined
together along parting line 7 by means of bolt 9 which passes through left
half 3 and
threads into right half 5.
Base member 4 has a generally flat or planar lower surface 6. In use, lower
surface 6 is
placed on a nd slides over the surface of the workpiece (not shown) to be cut.
Lower
surface 6 can have raised ribs 8 formed therein to both strengthen base member
4 against
:30 flexion and reduce the sliding friction with the workpiece. Base member 4
includes deck
11 which projects from the rear of body portion 2.
CA 02231259 1998-03-06
S
Handle portion 10 projects vertically from the upper surface of base member 4.
Handle
pol-tion 10 has rear boss portion 12 which has a generally rearward facing
forward thrust
surface 14 and a generally upward facing downward thrust surface 16. Handle
portion
also includes raised projection 7 8 which presents rearward facing abutment
surface
5 20.
Blade guard 22 projects downward from opening 24 in the bottom surface 6 of
base
member 4. Blade guard 22 closely surrounds blade 26 which is fixedly retained
in body
portion 2 with its cutting edge 28 (shown in phantom in FIG. 1) facing the
forward
10 direction.
As shown in Figure 4, blade 26 is retained in body portion 2 between ribs 30,
32 and with
notch 34 engaging pin 36, in a manner that is conventional in the utility
knife art. Blade
guard 22 is pivotally retained in body portion 2 by opposed pins 38 (one of
which is
shown in Figure 4) which engage corresponding sockets formed in halves 3 and
5. Blade
guard 22 is resiliently biassed to the down position by any suitable means,
such spring
21 shown in dotted line in Figure 4. Blade guard 22 is releasably locked in
the down
position by means of button 40. Button 40 is spring mounted to right half 5
and projects
through a corresponding opening in left half 3. In its undepressed state,
abutment
:?0 surface 41 prevents blade guard 22 from being retracted into body portion
2. When
button 40 is depressed, abutment surface 41 is brought out of engagement with
blade
guard 22 permitting it to retract into body portion 2 when pressed against the
workpiece.
'?S Figure 5 shows how the safety Blabber knife of the present invention is
gripped by the
hand when in use. The hand is placed over boss portion 12 with the thumb on
the left
side 3 and flue fingers on the right side 5. Rear boss portion 12 is
configured to conform
closely to the palm of the hand. In this position, the base of the thumb
naturally engages
and depresses blade guard release button 40 permitting blade guard 22 to
retract into
..0 body portion 2 when depressed against workpiece 50. When Blabbing
workpiece 50, the
hand is forced forward and down on boss portion 12. In this position, the
thumb and
CA 02231259 1998-03-06
6
fingers naturally squeeze the vertical surfaces on either side of raised
projection 18
thereby contributing to a secure grip on the tool. In addition, thrust
surfaces 14 and 16
are disposed to transfer the hand pressure into forward and downward motion of
the
tool and deck 11 is disposed to transfer downward pressure from the base of
the hand
to base member 4. Abutment surface 20 engages the cleft in the hand between
the thumb
and first digit and provides an additional thrust surface.
When dabbing rolled sheet material such as paper or plastic sheeting, it is
advantageous
to cut the stock at an angle to perpendicular. For this reason, blade 26 may
advantageously be disposed at an angle to bottom surface 6 of base member 4.
The use
of such an angle tends to cause the edge of the layer that is "undercut" to
lift thereby
facilitating the removal of the dabbed paper layers from the roll. In
practice, an angle
to the perpendicular of from about 10° to 30° achieves good
results.
In use, the safety Blabber knife of the present invention greatly reduces
fatigue and risk
of injury. The natural position of the wrist when pushing the knife through
the
workpiece and the support to the base of the palm provided by deck 11 permits
substantial force to be imparted to the tool without inducing fatigue, unlike
conventional broke knives which force the wrist into an unnatural bent
position. In
:?0 addition, the base member 4 which extends a substantial distance from
blade 26 protects
the fingers at all times from coming into close proximity to the blade. The
position of
blade guard release button 40 permits it to be depressed without having to use
the
fingertips ar otherwise vary the grip on the tool. Accordingly, the natural
grip for
applying a pushing force to the tool also depresses blade guard release button
40. This
lessens the amount of handling required to expose the blade and also leaves
the thumb
and fingers free to establish a secure grip on the tool while the tool is
being brought into
operative engagement with the workpiece.
For left handed applications, all that is required is to position blade guard
release button
40 on the right side of the tool. In the alternative a release button can be
provided on
both sides of the tool for ambidextrous use.
CA 02231259 1998-03-06
7
While the present invention has been described with reference to the preferred
embodiment, many alternatives, modifications and variants will be apparent to
those
skilled in the art without departing from the scope of the present invention.
