Safety core cutting knife

A knife for cutting honeycomb core and other materials with a combination of safety features to prevent or minimize injury to operator. The blade used has a hole through which a fastening device e.g. threaded screw, locks it to a handgrip. A safety guard covers the blade when not in use and automatically retracts as the blade is removed from the workpiece. The guard cannot be accidently displaced from the blade. It must be purposely unlocked by a manually triggered self-locking release assembly located in the handgrip which also automatically relocks the safety guard when retracted. The safety features consist of an automatically retractable guard attached to a safety handshield working in conjunction with the safety self-locking release assembly to prevent accidental release. Embodiments include (1) wherein the guard is opaque and has viewing ports and is hinged mechanically with springs, supports, and spacers, (2) wherein the guard is transparent eliminating the need for viewing ports, (3) wherein the guard and many other metal components are comprised of plastic, (4) wherein the guard is transparent and is hinged by an integrally molded component, (5) wherein the guard is hinged by a combination of mechanical (1) and integrally molded (4) means and (6) wherein a disposable blade is used.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention consists of a knife with a unique combination of safety 
features to minimize and prevent puncture and laceration wounds to the 
user. It was specifically designed for cutting honeycomb core used in the 
fabrication of reinforced plastic composite structures. Embodiments of the 
invention provide for cutting of other materials e.g. rubber slabs, foam, 
plastic, livestock products, vegetables and other food. 
2. Description of the Prior Art 
A variety of implements are currently used for cutting honeycomb core, 
e.g., sharpened putty knives, straight edge blades, e.g. electric carving 
knife blades, also, general utility knives, and jackknives. 
Currently used implements for this application are dangerous and inflict 
severe punctures and lacerations to the hand and other body parts. Deep 
blood vessels and nerves can be seriously damaged. The resultant affect to 
industry, business and the domestic front is costly due to such factors as 
time loss, decreased productivity, increased operating expenses, etc. 
The frequency of injury may be reduced by implementation of protective 
sheaths (e.g. for putty knife and straight edge blades) or by handles into 
which the blades may be manually folded or retracted (e.g. jackknives or 
general utility knives). The value of such safety features is minimal, 
however, because implementation is limited to non-productive times and 
because operators tend to avoid their use. A knife can be designed with an 
automatically retractable guard as its sole protective feature, but it 
also is dangerous because the same retractability feature can cause it to 
open automatically as well, thus exposing the blade when not expected by 
the operator. 
It should again be noted that cutting implements currently used for 
sectioning honeycomb core are dangerous to use. Prior art safety measures 
are not production effective and/or depend upon operator implementation. 
The invention herein described overcomes these problems and automatically 
supplies the safety which is needed at all times by combining an 
automatically retractable guard with a manually triggered, automatically 
retractable, self-locking release assembly. 
SUMMARY OF THE INVENTION 
Embodiments of this invention comprise the following: blade, handgrip 
assembly for supporting the blade and manipulating the overall knife; 
handshield (or hilt) to prevent the hand from slipping towards the blade; 
and automatically retractable guard assembly which locks shut when the 
knife is not in use. The blade is thereby automatically covered and 
prevents contact with the hand or other body parts. When the guard is 
manually unlocked the knife can be guided over the workpiece, via guard 
flanges, allowing penetration of the blade into and through the workpiece. 
The blade is not exposed to lacerate the body parts. As the blade emerges 
from the workpiece, the guard automatically retracts and covers the blade 
again preventing contact with the hand or other body parts. Once the guard 
is shut it is automatically locked into that position. Also included is a 
manually triggered, automatically retractable, self-locking assembly to 
release the guard for cutting and then to automatically lock it shut when 
automatically retracted to its closed position. The blade, therefore, 
cannot be exposed accidentally to cause injuries. It necessitates the 
willful operation of said self-locking release assembly. Guard flanges 
provide a dual function, (1) positioning the knife level with the surface 
of the workpiece and maintaining it level with this surface while cutting 
and (2) preventing the opposite hand and fingers from getting into the 
cutting path. Embodiments of this invention include flanges which are 
somewhat narrower in the flat dimension in order to cut curved 
configurations. Additional embodiments include flanges wherein the forward 
flat ends are curved upward to allow initial piercing of the core. 
A unique feature of the present knife is the combination of an 
automatically retractable safety guard assembly coupled with an 
automatically, self-locking manual release assembly which prevents 
accidental release of the guard. The knife may be fabricated entirely out 
of metal (first embodiment), the guard may be fabricated out of a 
transparent plastic guard (second embodiment) thus eliminating the need 
for viewing ports to observe the workpiece and cutting motion. Many of the 
parts may be fabricated from plastic materials with the guard transparent 
and the remaining parts either transparent, translucent or opaque (third 
embodiment). A fourth embodiment includes a guard with integral hinge, 
fabricated from a transparent plastic. This permits simplification of 
design, fabrication and usage by eliminating the mechanical, spring hinge.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning now to FIGS. 1-7 of the first embodiment and FIGS. 1a-7a of the 
second embodiment of this invention, it is seen that the safety knife, 
herein disclosed, consists of a blade 7 of various forward configurations 
which may include straight edge, curved or pointed (which may comprise 
either plastic, ceramic, metal or a combination and may be of a throwaway 
or disposable type), handgrip halves 1 and 2, safety handshield assembly 
3, automatically retractable safety guard assembly 8 with viewing ports 
13, manually triggered self-locking release assembly 17 and threaded lock 
screw 16. Third and fourth embodiments are described hereinafter. In 
embodiments 1 and 2 of this invention, the aft end of the blade 7, blade 
slot 5 in the safety handshield 3 and blade cavity 31 in the handgrips (1 
and 2) are aligned with each other as illustrated in FIGS. 7 and 7a such 
that the blade can fit through the aforementioned slot and be secured in 
the aforementioned cavity. Furthermore hole 7a in said blade is concentric 
with and dimensionally aligned with holes 29, 30, 32 and 33 of said 
handgrips (1 and 2) and tines (24 and 9) of said safety handshield 3 to 
accommodate threaded lock screw 16. Therefore, the blade may be continuous 
with a uniform cross section throughout its length, it may be necked down 
and with tines towards the aft end (as shown in FIGS. 7 and 7a), it may be 
necked down, only, or it may be continuous but ending in tines, only, as 
long as the aforementioned requirements are complied with. A working 
knowledge of the detailed assembly of preferred embodiments of the knife 
will enable a better understanding of its operation also hereinafter 
described. The mass components of embodiments 1 and 2 of this invention 
are assembled sequentially in the following steps: 
Safety Guard Assembly 
Fasten forward torsion spring supports and spacers 12 and 27 to the left 
and right sides of safety guard 8 through threaded holes 12a and 27a, 
respectively. Insert aft supports and spacers 11 and 26 through coils 
(facing upwards) of corresponding torsion spring 10 and 25 and fasten to 
left and right sides of safety guard 8 through threaded holes 11a and 26a, 
respectively. 
Safety Handshield to Safety Guard Assembly 
Raise aft ends of torsion springs 10 and 25, slip notched ends of tines 9 
and 24 of safety handshield 3 over supports 11 and 26 and carefully lower 
aft ends of springs on them. Raise forward ends of springs carefully onto 
supports 12 and 27. 
Handshield and safety guard are now attached together so that the guard is 
free to swivel laterally away from the blade exposing it as presented in 
FIG. 3 and to retract automatically. 
Manually Triggered Self-Locking Release Assembly 
Fasten locking pin 22 to coiled, spring 20. Insert the assembly into slot 
19 of the left half of handgrip 2. Fasten the manual trigger 17 to the pin 
with attachment screw 18. 
Join Handgrip/Safety Handshield and Safety Guard Assemblies 
Fasten both halves of the handgrip 1 and 2 together by means of screws 14. 
Fasten the guard/shield assembly to the handgrip by slipping tines 9 and 
24 into respective handgrip slots 15 and 28. Pivot the guard out of the 
way and then insert blade 7 through slot 5 of the shield 3 and then into 
its cavity 31 of the handgrip 1 and 2. 
Insert threaded screw 16 through holes 32, 29, 7a, 30 and screwed into 
threaded hole 33. 
All components including safety features are now in place, locked and ready 
for use. The desired line of cut on the workpiece is lined up through 
viewing ports 13. Activate the manual trigger 17, thus unlocking the 
safety guard 8 so that it will rise permitting cutting of the workpiece. 
As the blade 7 is removed from the workpiece, the guard automatically 
retracts covering the blade once more and is automatically locked shut by 
the self-locking release assembly. 
The knife blade 7 may be sharpened without detaching the guard 8, or the 
blade may be removed for sharpening or replacement when needed or if a 
disposable blade is used by unscrewing the attachment screw 16 and 
removing the guard/handshield assembly as one unit. The knife blade cavity 
31 in the handgrip is designed oversize with respect to the blade 
thickness as a means of preventing use of the knife without use of the 
safety features. 
Proceeding now to the second embodiment of this invention the similarities 
(FIGS. 1a-7a) become obvious. A major difference is that the safety guard 
8 is fabricated from transparent plastic. Examples of the plastic include 
but are not limited to acrylic (polymethyl methacrylate), polycarbonate, 
copolymer of polymethyl pentene which is solvent resistant as well. 
Fabrication is by injection molding, compression molding or any other 
compatible process. Using a transparent plastic eliminates the need for 
viewing ports in the guard. Clear vision of the blade and workpiece is 
always available. 
A third embodiment of this invention includes substitution of many of the 
metal components in FIGS. 1-7 e.g. handgrips 1 and 2, safety self-locking 
release trigger 17, locking pin 22, handshield assembly 3 (including tines 
9 and 24), and safety guard assembly 8 with plastic components 
manufactured via injection molding, compression molding or any other 
compatible process. 
A fourth embodiment of this invention shown in FIGS. 1b-3b also includes 
plastic substitution for many of the metal components presented in FIGS. 
1-7 of the first embodiment. The unique feature of this embodiment is the 
substitution of a transparent plastic guard 23 with integrally molded 
hinge 34 and 35 sometimes referred to as "living hinge". The properties of 
said plastic, e.g. polymethyl pentene are such that the integral hinge 
provides automatic retraction of the guard over the blade 7. This replaces 
the metal hinge consisting of springs, supports, spacers and holes, 10, 
25, 11, 26, 12, 11a, 26a, 12a, and 27a. Handgrips 1 and 2 are modified to 
accept the integrally molded hinge 34 and 35 in embodiment 4.