U.S. patent number 3,781,988 [Application Number 05/284,607] was granted by the patent office on 1974-01-01 for safety paper carton opening blade holder.
Invention is credited to Roger E. Jones.
United States Patent |
3,781,988 |
Jones |
January 1, 1974 |
SAFETY PAPER CARTON OPENING BLADE HOLDER
Abstract
A blade holder comprising a grip and a handle molded integrally
therewith, of hard plastic material, is provided with a guard
pivotally attached thereto for retracting movement to uncover the
corner of a blade held in the grip, the pivotal attachment being
provided by trunnions integral with respective sides of the grip
and received in apertures in respective side walls of the guard,
which are of sufficient resiliency to be sprung over the trunnions
during assembly of the guard to the grip. A tension spring is
connected to integral posts on a side of the grip and on a
corresponding side wall of the guard, positioned so that the spring
will move over center with respect to the pivot axis in shifting
from a closed to an open position, and the guard will be held in
each of such positions by the spring.
Inventors: |
Jones; Roger E. (Agoura,
CA) |
Family
ID: |
23090836 |
Appl.
No.: |
05/284,607 |
Filed: |
August 29, 1972 |
Current U.S.
Class: |
30/2; 30/286 |
Current CPC
Class: |
B26B
29/02 (20130101); B26B 27/005 (20130101) |
Current International
Class: |
B26B
29/00 (20060101); B26B 29/02 (20060101); B26B
27/00 (20060101); B26b 005/00 (); B26b
029/02 () |
Field of
Search: |
;30/2,286,295,336 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kelly; Donald G.
Assistant Examiner: Peters; J. C.
Attorney, Agent or Firm: Latta; Lynn H.
Claims
I claim:
1. In a carton-slitting knife, in combination:
a holder embodying a handle and a blade grip on one end thereof,
said handle and grip being integrally molded of an elastic,
moderately flexible hard plastic material;
said grip comprising a pair of laterally opposed grip fingers
spaced to define a thin flat slot in which the body of a cutting
blade is receivable;
one of said fingers having a longitudinal groove in which a
reinforcing back of said blade is receivable, and having a front
end part closing the forward end of said groove to provide an
abutment for engagement with the forward end of said blade back to
retain the blade in the grip when being dragged rearwardly through
a carton wall, said one finger having a head providing a
longitudinal shoulder along the top of said groove for supporting
said blade back against the reactive load of cutting action;
the forward end of said one finger being undercut below said
abutment with a downward and rearward inclination to provide a
carton wall engaging bearing land disposed in a plane diagonally
traversing a cutting corner of a blade mounted in the grip, with
said corner projecting beyond said grip for penetrating a carton
wall;
said head having integral pivot trunnions projecting from opposite
sides thereof;
a one-piece molded plastic guard comprising laterally spaced
opposed side walls having respective apertures receiving said
trunnions and pivotally mounting said guard on said grip with said
side walls closely embracing said grip, and a peripheral web
bridging between and connecting said side walls in spaced relation,
said walls having limited flexibility permitting them to be spread
apart for reception of said trunnions between them and insertion
thereof into said apertures;
a coil spring;
and integral anchor posts on said grip and guard respectively, to
which the ends of said spring are anchored with the spring under
tension, the point of anchorage to said guard being close to its
pivot axis and movable over center across the axis extending
between said pivot axis and said guard anchorage point, whereby
said spring is effective to yieldingly hold said guard in either of
two positions, one closed over said blade and the other in which
said grip is substantially fully exposed to provide convenient
access to said blade for removal and replacement.
2. A knife as defined in claim 1, said bridging web and the
adjoining periphery of said guard being of angular contour along
said periphery so as to brace said side walls against spreading
during normal use of the knife.
3. A knife as defined in claim 2, said guard being diamond-shaped
in peripheral contour, said bridging web and adjoining periphery
defining an obtuse upper corner of the guard, and said side walls
having free, spreadable corner extremities at a lower side of the
guard opposite said corner.
4. A knife as defined in claim 3, wherein said spreadable
extremities are bent laterally to provide diverging lips for
wedging entry of said trunnions between said side walls.
5. A knife as defined in claim 4, wherein said corner and corner
extremities are of obtuse-angular contour, and wherein said side
walls have pivot ears constituted by acute-angular tail extremities
beyond the rear end of said bridging web, said ears overlapping
said grip and pivoted on said trunnions, said web rear end being
engageable against said grip head to determine a limit open
position of said guard.
6. A knife as defined in claim 5, wherein said guard has an angular
end opposite said ears, with a rounded nose for bearing engagement
against a carton wall to be slit.
7. A knife as defined in claim 1, in which said spring including a
coiled body extending from its point of anchorage to said grip to a
point short of the periphery of said guard, and an extended tail
reaching from said coiled body to the anchor post on said guard,
said coiled body projecting laterally beneath the adjacent margin
of said guard.
8. A knife as defined in claim 7, the under side of said bridging
web abutting said head in said closed position, and the rear end of
said web abutting said head in said open position of the guard,
whereby to limit the movements of the guard toward said closed and
open positions respectively.
Description
BACKGROUND OF THE INVENTION
A carton opening knife embodying a grip in which a razor blade may
be mounted, with one corner of the blade projecting for piercing
the wall of a carton, and with a guard that is pivoted to the grip
and spring-loaded for movement to a blade-covering position, is
disclosed in Bailey U.S. Pat. No. 2,730,800. Knives embodying the
construction covered by that patent have been widely distributed
and used over a period of about 15 years, but none of them have
embodied any means for holding the guard in open position, and all
of them have embodied a construction fabricated of parts including
a separate pivot pin secured to the grip but not integral
therewith.
SUMMARY OF THE INVENTION
The general object of the present invention is provide a carton
cutter of the type referred to, in which the guard is spring-loaded
both to closed and to open positions, in a construction of maximum
simplicity and minimum cost. To this end, all parts are of molded
plastic construction with the exception of a coil spring providing
the spring loading for (1) normally holding the guard in a position
fully covering the projecting cutting corner of the blade, (2)
yielding under pressure of the guard against a carton wall being
severed, so as to allow the blade corner to project just enough to
pierce the wall, (3) automatically returning the guard to the fully
covering position when the blade is withdrawn from the carton wall,
and (4) holding the guard in a retracted, fully open position for
blade-changing when the guard is moved to such fully open
position.
These and other objects will become apparent in the ensuing
description and appended drawings, in which:
FIG. 1 is a right side view of a carton knife embodying the
invention, the guard being shown in the closed position;
FIG. 2 is a right side view of the same, the guard being shown in
the fully open position;
FIG. 3 is a front end view of the same, with the guard open;
FIG. 4 is a front end view of the same, with the guard closed;
FIG. 5 is a left side view of the grip portion and guard, with the
latter in open position; and
FIG. 6 is a cross-sectional view on an enlarged scale, taken on
line 6--6 of FIG. 2.
DESCRIPTION
Referring now to the drawing in detail, I have shown therein, as an
example of one form in which the invention may be embodied, a
carton opening knife comprising, in general, a cutter blade B, a
holder grip C having a handle H, a guard G for normally covering
the blade and grip, and a spring S for yieldingly urging the guard
C normally to the closed position shown in FIG. 1.
Blade B is of a type having a hardened blade body 10 and a
reinforcing back 11. Grip C is in the form of an integral claw on
the forward end of handle, H, and comprises spaced laterally
opposed fingers 15 and 16, the latter being fabricated of a
separate flat strip bonded to a rivet 17 formed as an integral
projection from finger 15 and received in a mating opening in
finger 16. A narrow slot 18 in which blade body 10 is snugly
received, is provided by spacing of the fingers 15, 16 laterally.
Finger 15 has an open longitudinal groove 19 to receive one side of
blade back 11, and finger 16 has a width approximately the same as
that of blade body 10, its upper margin being spaced from an
overhanging shoulder 20 (a lateral extension of the upper margin of
groove 19) so as to receive the other side of back 11. A foot 21,
formed as an integral downward projection from shoulder 20, bears
against the rear end of finger 16, for support which is reinforced
by a shoulder 22 on the forward end of handle H, bearing against
the rear end of finger 16 which is inclined so as to extend
diagonally beneath shoulder 22. Shoulder 20, and the upper margin
of groove 19, are defined by the underside of a head 28 which
carries the trunnions on which guard G is pivoted.
Fingers 15 and 16 have forward ends undercut on a diagonal such
that a substantial corner portion of blade B will project beyond
the grip C for penetration of a box wall, the angle of undercut
being such as to provide a bearing land 23 on which the holder can
slide against the surface of a box wall, thus functioning as a
depth gage to limit the penetration of blade B into the box wall.
Finger 15 at its forward end (FIG. 2) has a narrow web portion 24
extending downwardly and rearwardly from a vertical web 25 which
defines the closed forward end of groove 19, the latter being
enlarged in width at its forward end on its lower side, whereby the
forward end of the finger can be flexed outwardly enough to clear
the forward lower corner of blade back 11, for removal and
replacement of the blade. Web 25 is extended laterally to provide a
lip 26 (FIG. 4) which reinforces it in providing a support against
which the forward end of the blade will bear during a cutting
operation in which the blade is dragged rearwardly in the box wall
being cut.
Guard C comprises a pair of laterally spaced opposed skirts 30
joined by a bridging web including a front portion 31 and a back
portion 32, the latter resting on the top of grip C to limit the
closing movement of the guard, and terminating short of the rear
extremities of skirts 30, which project in the form of ears 33 for
mounting the guard on pivot trunnions 35. Trunnions 35 are formed
as integral projections from the sides of grip C above slot 19 and
shoulder 20, and are received in cylindrical apertures 36 in guard
skirts 30 (FIG. 6). In order to assemble the guard to the grip C,
it is provided with diverging lips 37 on skirts 30 at an open side
of the guard, remote from bridging web 31, 32 adapted to be wedged
over the ends of trunnions 35 so as to spread the walls 30 and
permit the trunnions 35 to enter the guard and pass between ears 33
with a spreading action until they reach the apertures 36 therein,
whereupon they will enter the apertures and the elasticity of the
ears 33 will cause them to close upon the trunnions, assuming the
assembled relation shown in FIG. 6.
Loading spring S comprises a coil spring body 40 attached at one
end to an integral post 41 on grip finger 15 and having at its
other end an extened tail 42 which is attached to an integral post
43 on a side wall 30 of guard G. Attachment to posts, 41, 43 is by
means of open loops or hooks 44,45 at the respective ends of the
spring unit S, the posts 41, 43 being provided with annular
retainer grooves 46 receiving these loops.
OPERATION
Guard G has a smooth, rounded bearing nose 50 at the end of web 31,
which is disposed at a point remote from pivot trunnions 35. In
using the knife, the nose 50 is pressed against a carton wall to be
slit, the pressure causing the guard G to yield while the point of
blade B enters the carton wall. In normal useage, the knife point
will pierce the carton wall until bearing lands 23 engage the
carton wall to function as depth-gage guides and runners to slide
along the carton wall during the slitting operation. When a cut is
completed, the knife is simply withdrawn, the spring S drawing the
guard G back to its closed postion as the blade B leaves the carton
wall. When a new blade is to be installed, the guard is swung back
to the fully open position of FIGS. 2 and 5 to expose the blade B
for manipulation, and the blade is grasped in one hand and tilted
laterally, functioning as a lever to spring the grip finger 23
outwardly in one direction while the finger 16 is engaged by the
other hand (e.g.) by pressing a thumbnail against lip 26, (FIG. 5)
and flexed in the opposite direction until the outer end of knife
back 11 can be lifted clear of lip 26 and slid endwise out of slot
19. Such flexing is facilitated by the thin web portion 24 of
finger 15.
Holder unit C, H and guard G are molded of a highly elastic,
flexible hard plastic (synthetic resin) material only slightly
plasticized, having high strength and not brittle.
* * * * *