Note: Descriptions are shown in the official language in which they were submitted.
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10 .
Tltle of the Invention
A SAFETY KNIFE OR CUTTER
Technical Field
This invention relates to a knife or cutter with a safety shield
assembly. The knife or cutting tool is intended for many uses in
cutting materials, particularly sheet materials such as paper, fabric,
cardboard, plastic, film, floor coverings and the likè and is
generally of the type used in manual cutting tasks, "Do-lt-Yourself"
or home i o. Ls work or by ~,ari k~ ,. Hereinafter in this
description and claims the word "knife" is used to include a cutter or
cutting tool.
.
~ Known knives of this type are usually provided with very sharp
blades, which give rise to two different problems. Firstly when
cutting a material on a table or other substrate, the blade tends to
cut down into the substrate, causing damage to it. Secondly, a sharp
blade when projecting from a knife can cause injury if it encou,,Le,s a
hand or other part of the body of the user or of another person.
- It is an object of the invention to overcome these problems.
French Patent 2 639 574 Longet et a1 describes a safety cutter
having a slidable cover to hide the blade and a heel which is located
under the material to be cut, the heel being joined to the main body
. . .
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of the cutter by a thin and tapered body part which permits the
passage of the cut material. The slidable cover has a foot, and the
material to be cut is inserted between this foot and the heel of the
tool. However in order to accommodate materials of different
thickness it is necessary to relocate the slidable cover, and there is
no way of pressing the blade onto the material to be cut against a
firm backing. The blade does not have an exposed point and the
cutting edge is angled such that cutting is effected from beneath the
material to be cut which would make it difficult to cut on a line.
The heel is of substantial thickness and would not easily slide
between a sheet material (such as paper) and a table, workbench or
other substrate on which the material is laid.
US Patent 4 167 810 Gilbert describes a cutting tool for sheet
material, especially for opening cardboard cartons, which has a guide
member of bent wire fixed to its handle for keeping the blade in
cutting . , g L with the sheet material and away from the contents
of the carton. One arm of the guide member is above the blade tip so
as to keep the blade from di _ ~ from the sheet material.
Another arm of the guide member is below the tip of the blade for
preventing cans or other carton contents from being cut by the blade.
The guide member restricts access to the blade cutting edge, which is
said to provide a measure of protection for the user, especially the
user's finger. However there is nothing to prevent the blade tip
being pushed through the guide member, so that this tool could not be
safe~y used on a table top or other sensitive substrate, and the tip
could then come into contact with part of the user's body. Also, a
single wire, pressed down onto a table or other sensitive substrate,
could cause damage thereto.
Disclosure of the Invention
The present invention provides a knife comprising a body, a blade
having a cutting element projecting from the body, a guard plate
adjacent to the blade and facing the cutting element thereof, and an
attachment member for attaching the guard plate to the knife, the
attachment member adjacent to its attachment to the guard plate
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being thin and being forward of the blade and aligned therewith, such
that when material to be cut is introduced between the body and the
guard plate, and pressure is applied on the body, the cutting element
presses the material to be cut against the guard plate. Normally the
cutting element has a point or tip at an end thereof. Such a cutting
element is called a "pointed cutting element".
Preferably the attachment member is flexible and more
particularly is a spring member. Alternatively, flexibility may be
provided by a hinged joint, suitably at or adjacent to the attachment
point to the guard plate, the hinged joint preferably having a limited
amount of pivotal movement. Flexibility allows a gap between the
blade and the guard plate to be closed when pressure is applied on the
blade. It also facilitates use of the knife at a variety of angles to
the substrate. Flexibility also allows paper fragments to be cleared
from the blade point between cuts e.g. by "snapping" the guard plate
away from the point and dislodging the paper fragments.
In a preferred embodiment, a groove or slot is provided in the
guard plate, aligned with the blade. Although the blade presses the
material to be cut against the guard plate, the blade tip should not
reach the base of the groove in order to minimize wear on the blade
tip. The groove or slot may be short, suitably extending for less
than 25% of the length of the guard plate, as it only needs to be long
enough to receive the point of the blade.
Preferably the attachment member is a thin strip suitably having
a thickness (perpendicular to the blade) not more than 5 times, more
preferably not more than 2.5 times, the thickness of the blade. The
attachment member should be thin enough to permit easy passage of it
along the cut made in the material by the blade. If desired the
spring member may comprise a substantially rigid upper portion, e.g.
having a V-shaped cross section with the apex of the V facing the
blade, and a lower spring portion adjacent to its attachment to the
guard plate.
The guard plate suitably comprises a rigid abrasion resistant
, ~
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plast;cs material. It should be readily slidable on a smooth
substrate surface and it may be described as a "skid".
The guard plate suitably is of generally triangular shape,
tapering rearwardly. It preferably has a width of at least 0.5cm,
more suitably a width in the range I to 2 cm at it widest point e.g.
the base of the triangle.
Other preferred features of the inventibn''ar'e'~defined'~n~~e' ~'
claims.
According to another aspect, the present application provides a
knife comprising a body and a replaceable blade unit which fits inside
the body, wherein the blade unit comprises a housing and a multi-point
blade rotatably mounted inside the housing, the blade being rotatable
between rest positions in which all the points of the b1ade are within
the housing and cutting positions in which one of the points of the
blade projects from the housing and extends outside the body.
Preferably the blade is rotatable by means of a spindle which
carries a knob outside the body and which has a portion engageable
with the blade inside the housing.
In the preferred : b~ the spindle carries a locking
mechanism~for retaining the blade in either a rest position or a
cutting position, the locking mechanism being releasable by axial
retraction of the spindle.
In a further aspect, the present invention provides a blade unit
for a knife, comprising a housing and a multi-point blade rotatably
mounted inside the housing, the blade being rotatable between rest
positions in which all of the points of the blade are within the
housing and cutting positions in which one of the points of the blade
projects from the housing.
Preferably the blade has four points. Most preferably the blade
has a generally square configuration with indentations in the four
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sides. The blade may be star-shaped.
In the preferred embodiment, the housing has one dimension
slightly greater than the diagonal distance between opposed points on
the blade and a second dimension at right angles thereto which is less
than the said distance but slightly greater than the length of a side
of the blade.
Brief Description of Drawinqs
The invention is illustrated in the a~ , lying drawings, in
which:
Figure 1 is a pictorial view of a first embodiment of a knife
according to the invention.
Figure 2 is a side elevation of the knife of figure 1.
Figure 3 is a top plan view of the knife of Figures 1 and 2.
Figure 4 is a detailed pictorial view of the guard plate and
spring member.
Figure 5 is a pictorial view of a second embodiment of a knife
according to the invention.
Figure 6 is an elevation of the knife of Figure 5 from one side.
Figure 7 is an elevation from the other side of the knife of
Figure 5 and 6, showing a flap open.
Figure 8 is an exploded projection of the knife of Figures 5 to 7.
Figure 9 is a side elevation of a multi-point blade for the knife
of Figures 5 to 8.
Figure 10 is a projection of the multi-point blade.
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Figure 11 is a projection of a box housing for holding the blade.
Figure 12a and 12b is a pair of projections showing the blade
inside the box unit in two different orientations, the rest position
(a) and the cutting position (b).
Figure 13 is a pictorial view of a shield assembly from above.
Figure 14 is a view similar to Figure 10 of an alternative
blade.
Figure 15 is an exploded view of a third embodiment of a knife
according to the invention.
Figure 16 is an elevation on the centre line of one variant of a
knife of the third embodiment.
Figure 17 is a similar elevation of a second variant.
Figure 18 is a similar elevation of a third variant.
Figure 19 is a similar elevation of a fourth variant.
Figure Z0 is a similar elevation of a fifth variant.
Figure 21 is a similar elevation of a sixth variant.
Figure 22 is an exploded view of a fourth e bc', L of a knife
according to the invention.
Figure 23 is an elevation on the centre line of one variant of a
knife of the fourth embodiment.
Figure 24a is an elevation of a metal part for the variant of
Figure 23.
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Figure 24b and Zc are elevations of alternative metal parts.
Figure 25 is an elevation similar to Figure 23 of a second
variant.
Figure 26 is an elevation of a blade for the variant of Figure 25.
Figure 27 is an exploded view of a fifth embodiment of a knife
according to the invention.
Figure 28 i5 an elevation on the centre line of one variant of
the fifth embodiment.
Figure 29 is a similar elevation of a second variant.
Figure 30 is a similar elevation of a third variant.
Figure 31 is an elevation of a metal part for the variant of
Figure 30.
Figure 32 is an exploded view of a sixth embodiment of a knife
according to the invention.
Figure 33 is an enlarged view of a shield assembly for the
embodiment of Figure 32.
Figure 34 is an elevation on the centre line of the embodiment of
Figure 32.
Figure 35 is a pictorial view of an alternative version of the
embodiment of Figure 1.
Msdes for carryinq out the invention
Where similar features appear in the various embodiments, the
same reference numerals are used or are ' stood.
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As shown in Figures I - 3, a knife according to the invention
comprises a body 1 suitable to be gripped manually, a blade 2
projecting from the body, and a shield assembly 3 adjacent to the
blade.
The body I and blade 2 may be similar to those of a conventional
"trimmer" knife such as is sold under the Trade Mark STANLEY. The
blade 2 may suitably be housed in replaceable manner inside the body
I0 l, with one triangular portion-of~the blade proJ~L1ng ~, the body.
The triangular portion has a sharp point 4 and a cutting edge 5 which
extends generally parallel to the longitudinal direction of the body.
The shield assembly comprises a guard plate 6 and a thin spring
member 7 by which the guard plate 6 is attached to the body I. The
spring member 7 suitably comprises a thin strip of metal which is
anchored at the top end 8 to the body. A free portion 9 of the strip
extends downwardly in front of the body on the vertical mid-line of
the body and thus is aligned with the blade. At its bottom end the
spring member is fixed to the guard plate 6 suitably of plastics
material. The guard plate lies underneath the point 4 and cutting
edge 5 of the blade, which provides the pointed cutting element of the
blade. In the rest position of the spring member 7, there is a gap
"a" between the blade 2 and the guard plate 6 (see Figure 2). As
shown in the drawings, the guard plate has the shape of an isosceles
triangle with the apex pointing rearwardly. However the guard plate
may ~if desired have at least one edge parallel to the longitudinal
direction of the body so that the guard plate can be moved along a
straight edge such as a ruler when the knife is being used.
As shown in the drawings, the guard plate is a thin plate with
parallel top and bottom surfaces and a thickness of the order of 0.5 -
I.S mm. However it may if desired have converging top and bottom
surfaces reducing from a thickness of 3-3.5mm at the front edge (where
it is attached to the spring member) down to a minimal thickness e.g.
0.25 mm at the trailing edge or apex.
The guard plate preferably has a groove I0 in its top surface,
~ w 096/05027 2 1 9 7 1 0 1
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aligned with the blade 2. Dur;ng cutting the blade enters the groove
but the blade point 4 should not reach the base of the groove so that
it is kept sharp.
Optionally, the shield assembly includes a nose 11, suitably of
transparent plastics material, which encases the front of the body and
protects the spring member. The nose 11 does not extend downwardly
as far as the point 4 of the blade. The spring member 7 may be
anchored by its upper limb 8 in the nose 11-,~ wh1ch in t~n~ ec~Ped
to the body 1.
In use, the body is gripped by hand and the guard plate 6 is
placed on a table, work bench or other smooth substrate surface. An
edge of the material to be cut is introduced between the guard plate 6
and the body 1. Pressure is then applied on the body, the spring
member 7 flexes and the point 4 of the blade is pressed against the
guard plate 6. The knife is pulled rearwardly, causing the blade to
cut the material which is trapped against the guard plate, with the
groove 10 (if present) defining a line on which the material is not
supported so that the blade can more easily cut through it. As the
knife is drawn rearwardly, the guard plate slides on the substrate
surface, the spring member 7 enters the cut formed in the material,
and the material passes on either side of the spring member.
The guard plate protects the table (or other substrate surface)
from~being cut by the knife. When the knife is not in use, the guard
plate shields the blade and prevents accidental damage or injury being
caused by the exposed blade.
If desired, a roller 12 may be mounted in the underneath surface
of the body 1, above the rear portion of the guard plate 6 to
facilitate movement of the knife over the material to be cut, the
- material being pressed against the guard plate by the roller and to
restrict the depth of entry of the blade point into the groove 10.
The roller may be formed in two parts with a mid-axial gap so that it
does not interfere with the blade. Alternatively the roller may be
replaced by roller bearing(s). The roller or roller bearing(s) may be
, . .. : . _ _ . : _ . . _ . . . . . _ _ . . .
WO 96/05027 2 1 9 7 1 0 1 A ~ I l l _ ¦
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spring-mounted in the body.
The nose 11 suitably has a pair of internal walls (not shown)
which extend longitudinally on either side of the spring member 7 to
restrict possible movement of it out of alignment with the blade.
The spring member 7 may be anchored in the nose 11 rather than
directly onto the body. The shield assembly comprising the nose 11,
spring member 7 and guard plate 6 may be made and supplied as an
accessory to existing knives, with suitable means being provided for
securing the assembly to the knife e.g. the nose 11 may be extended
rearwardly as far as assembly screw holes in the body of the knife
(see Figure 15 below, holes 43 and 44) and a pair of ~" esr :~ing
holes may be provided in the extended nose so that a screw used for
assembling the knife body can also be employed to secure the shield
assembly.
As shown in Figures 5 to 14, a second embodiment of a knife
according to the invention comprises a handle 2 adapted to be gripped
manually and a body 1 which houses a blade unit 14. The body has a
shield assembly 3 similar to that described in relation to Figures 1
to 4. The shield assembly comprises a guard plate 6 and a spring
member 7 by which the guard plate is attached to the body 1. The
spring member comprises a thin strip of metal which is anchored at the
top end ~ to the body. A free portion 9 of the strip extends
downwardly at the front of the body, inside a nose portion 11 which
encloses the front of the body and protects the spring member. The
free portion 9 of the strip is on the vertical mid-line of the body
and thus is aligned with the blade (described below). It is
preferably formed of a strip of metal bent into a V-shaped cross
section, with the ridge pointing rearwardly. At its bottom end the
spring member is fixed to the guard plate 6 which extends underneath
the blade. As shown in the drawings, the guard plate has the shape of
an isosceles triangle with the apex pointing rearwardly. However the
guard plate may if desired have at least one edge parallel to the
longitudinal direction of the body so that the guard plate can be
moved along a straight edge such as a ruler when the knife is being used.
, . ... .. _ . . . . . ... . . _ _ . . .
~ W096/05027 21 971 01 r ~
11
The guard plate suitably comprises a riyid abrasion-resistant
plastics material. It should be readily slidable on a smooth
substrate surface and it may be described as a "skid". It has
converging top and bottom surfaces reducing from a thickness of 3 to
3.5mm at the front edge (where it is attached to the spring member)
down to a minimal thickness e.g. 0.25mm at the trailing edge or apex.
The guard plate has a groove 10 in its top surface (or a slot
extending through the guard plate) aligned with the~~bladë~ D~ihg
cutting the blade enters the groove but the blade point should not
reach the base of the groove so that it is kept sharp.
A roller 12 is mounted at the rear of the body, above the apex of
the guard plate, to facilitate movement of the knife over material to
be cut, the material being pressed against the guard plate by the
roller, and to restrict the depth of entry of the blade point into the
groove 10. Alternatively the roller may be replaced by roller
bearing(s). The roller or roller bearing(s) may be spring mounted in
the body.
The body has a flap 13 in one side wall. As illustrated, this
flap 13 is hinged at the top of the body 1. However it may
alternatively be slidable relative to the body. A blade unit 14 may
be installed inside the body via the opening i5 in the side wall 26
which is revealed by moving the flap 13. The blade unit comprises a
holl~w box 16 which houses the multi-point blade 17. As shown the
blade has four points 18 each with cutting edges 19, 20 leading to the
point. The blade resembles a square with slightly indented edges.
The blade 17 is rotatably mounted in the box 16, e.g. by means of
annular ribs (not shown) which project axially from the blade around
the central hole 22 and fit slidab1y inside co" e~ollding annular ribs
(not shown) on the inside of the side walls of the box.
Figure 8 shows a divider wall inside the body 1, against which
the blade unit 14 buts. Slots to accommodate the spring member 7 and
a recess to a L~ the top end 8 of the spring member are also
shown in Figure 8.
w os6/0so27 2 1 9 7 1 0 1 P~ c
The box 16 has a generally rectangular cross section, with a
width slightly greater than the diagonal span of the blade from point
to point, but with a height less than this diagonal span but greater
than the length of a side of the blade. The blade is mounted in the
box with its centre spaced from the top of the box by a distance
slightly greater than one half of the diagonal span of the blade, and
spaced from the bottom of the box by a distance less than one half of
the diagonal span of the blade. Thus the blade can be turned from the
position of Figure 12a, in which the blade is entirely housed inside
the box (with its sides parallel to the edges of the box), to the
position of Figure 12b in which one point 18 of the blade projects
downwardly from the box through a slot 21 in the base thereof. The
blade point 18 extends below the bottom edge of the body 1 into a
position in which it can cut material between the body 1 and the guard
plate 6 (see Figure 6).
The blade 17 has a central hole 22 which as illustrated is
hexagonal but which could be square or another non-circular shape or
could have grooves to receive splines. The hexagonal hole 22
co-operates with a hexagonal portion of a spindle 23 which extends
through the body and carries a knurled knob 33 outside the body,
beside one side wall 24. If the hole 22 is other than hexagonal, the
cooperating portion of the spindle 23 has a complementary shape. The
spindle is rotatable in round apertures 25 in the side walls Z4,26.
Mounted on the spindle, inside the side wall 24, is a spring 27 and a
locking member 28 comprising a disc with two diametrically opposed
pins 2g projecting therefrom parallel to the spindle. These pins
enter into a pair of holes 30 in one side wall 24 of the box 16 which
has a circular array of eight holes 30 spaced equiangularly. The
locking member 28 has a hexagonal hole 31 which is mounted on the
spindle 23 to be rotatable therewith, retained by a ring 32, which may
suitably be a rubber 0-ring.
The pins 29 can enter into any pair of the holes 30 to retain the
spindle 23 and thus the blade 17 in a particular orientation. For
example in the orientation of Figure 12a, the pins 29 would be engaged
in holes 30a, while in the orientation of Figure 8b, the pins would be
.. . . . . .... . . . _ _ _ _ _ . _ _ _ _
~ W o 9~05027 2 l 9 7 l O l r~
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_ 13 -
~i ,'.! 1 .
in holes 30b. In either position, the pins (which are held by the
holes 30 in the side wall 24 of the box 16) lock the spindle and thus
the blade 17 against rotation, so that in the orientation of Figure
12b one blade point 18 can be used for cutting while in the
orientation of Figure 12a the blade is safely stowed inside the box.
The box can only be inserted into or removed from the body with the
blade in the position of Figure 12a. This is also the position of the
blade when the blade unit is packaged for supply to the consumer.
To rotate the blade from one position to the next, the user pulls
the knob 33 in an axial direction to withdraw the pins 29 from the
holes 30 in the side wall 24. The spring 27 is ~ ~,scd between the
box 16 and side wall 24. The user then rotates the knob by one eighth
of a revolution and the blade 17 is turned accordingly from the
position of Figure 12a to that of Figure 12b (or vice versa). The
pins 29 then enter into the next pair of holes 30, urged by the spring
27.
The blade 17 can be turned progressively so that each of the
cutting edges 19 on the four points of the blade are used. When these
have become blunt, the blade unit 14 can be removed from the body 1
via the opening 15 and can be reinserted in the reversed position, so
that the cutting edges 20 on the points of the blade are used for
cutting. A ratchet mechanism may be incorporated if desired, to
restrict rotation of the spindle to one direction and to ensure that
it stops in each of the eight chosen positions (Figures 12a and 12b).
If desired, a pair of small rollers or feet, preferably
spring Led, may be provided alongside or ahead of the blade point
to press the material being cut against the guard plate.
Instead of having a rectangular cross section, the blade unit 14
could be circular with a diameter slightly greater than the diagonal
span of the blade but with one segment cut away so that a blade tip 18
protrudes (as in Figure 12b). In either case, the blade unit should
be shaped to fit neatly inside the hollow body 1, so that it does not
move inside the body during use.
W096105027 2197101 l~ 'C~0~
- 14 -
If desired, the flap 13 could be omitted and one side wall of the
blade unit 14 could fill the opening 15 in the side wall 26 of the
body.
In use, the knob 33 is rotated to bring a blade point 18 to the
position of Figure 12b. The handle 2 is then gripped by hand and the
guard plate 6 is placed on a table, work bench or other smooth
substrate surface. An edge of the material to be cut is introduced
between the guard plate 6 and the body 1. Pressure is then applied on
the body, the spring member 7 flexes and the point 18 of the blade is
pressed towards the guard plate 6. The knife is pulled rearwardly,
causing the blade to cut the material which is trapped against the
guard plate, with the groove 10 defining a line on which the material
is not supported so that the blade can more easily cut through it. As
the knife is drawn rearwardly, the spring member 7 enters the cut
formed in the material, and the material passes on either side of the
V-shaped spring member.
The guard plate protects the table (or other substrate surface)
from being cut by the knife. When the knife is not in use but the
blade has not been rotated to the position of Figure 12a, the guard
plate shields the blade point and prevents accidental damage or injury
being caused by the exposed blade.
The ~nives of the invention are particularly useful for cutting
paper. As the knife is not adapted for sharpening pencils, a
conventional pencil sharpener may be inco,~o~at~d into the body e.g.
at the end of the handle remote from the blade.
Figure 14 shows an alternative form of multiple-use blade which
;s similar to that of Figure 9 except that the blade tips 18 have been
omitted. Each cutting edge 19 is spaced from the opposed cutting edge
20 by a flat portion 35 which defines a point where it meets each of
the cutting edges 19, 20. Thus the use of cutting edge 19 does not
blunt the point on cutting edge 20.
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- 15
Figure 15 shows a third embodiment which is based on a knife body
of conventional type which is divisible into two parts 40, 41 on the
longitudinal centre line, and a standard blade 42 which is retained
between the two body parts when the body is assembled and held
together by a screw through holes 43, 44 in conventiona1 manner. The
body part 40 has a boss 45 which has a bore therein, with its axis
ila~v~se to the longitudinal centre line. A groove is cut in each
body part 40, 41, extending from the front edge to the boss 45. The
guard plate 46 has a longitudinal bore 47 in its front edge and a
short groove or slot 48 in its top surface, connected with the bore.
The groove or slot extends only for a minor part of the length of the
guard plate, as it is only required to receive the point 4 of the
blade. A spring member 49 comprises a rear arm 50 adapted to be
received between the body parts 40, 41 in the mating pair of grooves
described above, with a finger 51 at right angles to the rear arm S0,
adapted to be received in the hollow boss 45. The spring member has a
coil portion 52 extending forwardly and upwardly, below which there is
an inclined portion 53 which i5 displaced sidewardly so that the main
limb 54 of the spring member is aligned with the arm 50 (and thus is
aligned with the blade 42) when the unit is assembled. At the lower
end of the main limb 54, the spring member has a foot portion 55 which
enters into the bore 57 in the guard plate 46 and is secured therein.
Figure 16 shows the embodiment of Figure 15 in the assembled
position.~ The guard plate 46 mounted on the spring member 49 can flex
lnto~alternative positions which are shown in dotted outline, so that
the knife can be used at a variety of angles to a substrate. The
point of the blade 42 enters into the central slot 48 of the guard
plate 46 so that the point ls enclosed therein.
~ This embodiment uses a standard blade, which moves relative to
the anvil or guard plate 46, ensuring firm contact at the cutting
point. The spring action allows paper fragments which may accumulate
at the blade point to be cleared after each cutting action. The blade
e _ ~ -L in the anvil slot centres the blade on the spring limb 54,
so that it can pass through the paper (or other material being cut).
The closeness of the spring limb 54 to the cutting point allows a
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tight cutting radius, if the knife is being used for making curved
cuts.
Figure 17 shows a variant on the embodiment of Figure 15 and 16,
in which the arm 50a of the spring member is longer so that the coil
52 and the limb 54 are spaced in front of the blade 42. The cutting
point of the blade is nevertheless engaged in the slot 48 in the anvil
46.
Figure 18 shows another variant on the embodiment of Figures 15
and 16, in which the coil portion 52a of the spring is directed
rearwardly and downwardly so that the two coils of the spring can
embrace the front edge 56 of the standard blade 42. This puts the
coil in a less exposed position, and maintains the limb 54 in
alignment with the blade. The guard plate 46 can flex as in the
variants of Figures 16 and 17 to allow paper fragments to be cleared.
Figure 19 shows a further variant on the embodiment of Figure 16,
in which the coil portion 52b of the spring is located about half way
down the limb 54, which is formed as two inclined portions so that the
coil is offset in front of the edge 56 of the blade. The two coils of
the spring 52b embrace the front edge 56 of the blade to a minor
extent. The offset spring allows flexing and vertical collapse of the
assembly i.e. the guard plate 46 moves up to the blade in a parallel
movement.
Figure 20 shows a further variant on the embodiment of Figure 18,
in which the arm 50a of the spring member extends downwardly and
rearwardly from the coil 52a, alongside the front edge of the body,
and the finger 51 is received in a hole A in the blade. Two holes A
are provided in the blade to allow both points to be used.
Figure 21 shows a further variant on the embodiment of Figure 18,
in which the guard plate 46 does not have a central slot 48, so that
the point of the blade 42 acts against the top surface of the guard
plate 46. The embodiments of Figures 18 to 21 are particularly
suitable for use with a shielding nose such as shown in Figures 1 to
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3. The coil embracing the blade is sufficient to retaining centering.
~ ~ .
Figure 22 shows a fourth embodiment in which the body parts do
not require modification, but a special blade 62 of reduced height is
used. This blade has a notch 63 in its top edge.
The attachment member 64 is formed as a pressed metal part which
comprises a retaining portion 65, and two inclined limb portions 66,
10' 67 joined at an-elbow 68. -The ~cLa1nlng pu,Lfon D~ has Li,~ shape or
the upper part of a conventional blade, with a notch 69 in its upper
surface in the appropriate position for the seating notch of a
conventional blade. On its lower edge, the retaining portion 65 has a
projection 70 which mates with the notch 63 on the blade 62. Thus the
retaining portion 65 and the blade 62, when assembled together, occupy
the space of a conventional blade inside the assembled body portions
40, 41.
.
The upper limb 66 is inclined forwardly and downwardly from the
retaining portion 65 and the lower limb 67 is inclined rearwardly and
downwardly i' cr,~ The lower limb 67 fits into the bore 47 in the
guard plate 46, which also has a central slot 48. The guard plate can
- be replaced by pulling it off the lower limb 67 and pushing a fresh
guard plate 46 into position.
The assembled position of this embodiment is shown in Figure 23.
The metal part is shown in elevation in Figure Z4.
Although this embodiment may lack the flexibility of the
preceding embodiments, it is particularly suitable for cuttins
cardboard or shrink wrap film where the problem of accumulated paper
~ fragments at the blade tip is not cncûu,,Lc.~d. The metal part may, if
desired, be made of spring steel and flexibility may be provided at
the elbow 68. Figure 24b shows an alternative version of the metal
part in which the lower limb 67 has been twisted through 90~ at the
elbow 68, so as to allow for flexibility and also to arrange the lower
limb 67 with smaller dimension (i.e. the thickness of the metal) in
the plane of the guard plate 46. This has the advantage that the
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aperture 47 can have a reduced height and the thickness of the guard
plate 46 can be reduced, as compared to Figure Z2. Figure 24c shows a
further alternative version of the metal part in which a spring or
concertina region is provided in the upper limb 66 so that flexibility
is achieved in the attachment member. This feature may be used along
or in combination with the feature of Figure 24b.
In another embodiment, a pressed metal retaining bar 65 is
combined with a spring member as in one of the e~bodîmënts~of~F~gur~3
15 to 21 i.e. the limb 50 and finger 51 of the spring member are
replaced by the retaining portion 65, the two elements being welded or
otherwise secured together.
Figure 25 shows a further variant which utiiizes a uus' ~P
blade 72 which resembles a type of blade already commercially
available. The blade 72 is of conventional height and fits into the
body parts in conventional manner. It has two limbs depending
downwardly and inwardly from an elbow on its front and rear edges.
These limbs form the same function as the lower limb 67 in the
bc'i l of Figure 22, and can be pushed into the bore 47 in guard
plate 46. The blade 72 has a cutting edge which is generally parallel
to the limb 73 and terminates in a cutting point 74. The guard plate
46 is replaceable.
Figure 27 shows a further embodiment which is similar to that of
Figures 22 to 24, utilizing a blade 62 of reduced height. The shield
assembly comprises a blade retaining part 65 with a limb 76 inclined
downwardly and forwardly ~h~ ~rll The guard plate 80 comprises a
part of the metal part which has been folded at right angles to the
limb 76. A removeable plastic cover 81 can be slid onto the guard
plate 80. Figure 28 shows the assembly without the plastic cover 81,
while Figure 29 shows the plastic cover in position. A space 77 is
provided between the limb 76 and the guard plate 80. The plastic
cover 81 has a slot 78 which partly accommodates the limb 76 and
partly extends over the space 77, so that the blade point can enter
into this part of the slot.
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,.
Figures 30 and 31 show an alternative form of the meta1 part.
The limb 76a is indented and the guard plate 80a has~an çdge 83 which
(before folding) lies in the indented region, leaving a space 8Z
between the limb 76a and the edge 83. The guard plate 80a also has a
slot 84 on its centre line. When the guard plate 80a is folded so
that it is at right angles to the limb 76a ~as shown in Figure 27) the
slot 84 is aligned with the limb 76a. It therefore allows the blade
point to enter into this slot.
Figures 32 to 34 show a further embodiment, in which the shield
assembly is formed as a moulded plastics unit which is mounted on a
special blade 92 having holes 93 therein. The assembly 85 comprises a
flexible loop portion 86 with a plate portion 87 inclined downwardly
and rearwardly therefrom, with a channel-shaped flange 88 at the free
end thereof. A stud 89 projects tranversely from the plate 87. The
loop portion 86 is extended downwardly and forwardly into a thin limb
90 which is of similar thickness to a blade. A guard plate 91 extends
rearwardly from the base of the limb portion 90.
The shield assembly can be snapped onto a blade 92, with the
plate portion 87 alongside the blade and the stud 89 entering through
one of a pair of holes 93 in the blade. Part of the cutting edge of
the blade is housed in the flange 88. The assembly flexes about the
loop portion 86, so that the guard plate can be snapped back after
cutting to clear away debris.
Figure 35 shows an alternative version of the embodiment of
Figures 1 to 4 in which the shield assembly 3a includes a nose 111
which is extended rearwardly around the body 1 to the region where a
screw 112 is used to secure two parts 113 and 14 of the body
together. This screw 112 also passes through holes in the nose 111 to
retain the shield assembly 3a in position on the knife. The spring
member 7 is anchored by its top limb 8 in the nose 111. The shield
assembly 3a may be sold as an accessory for conventional knives.
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Industrial Applicability
The invention provides new knives and accessories therefor wh;ch
are suitable for manufacture and sale to the general public and to
workers in the building and craft trades and the like.
10 .
2~
