Safety guard for the blade of carton openers

A blade guard is mounted to a conventional carton cutter for longitudinal, reciprocal movement between a "safe" position outwardly of and covering the tip of the cutter blade and a retracted position spaced inwardly from and exposing the tip and a portion of the blade. The guard is normally spring biased to the safe position, yet responsive to pressure against the carton wall to retract the guard until it passes the end of the carton wall in front of the blade.

BACKGROUND OF THE INVENTION 
Through the years, the increase in shipping of goods and supplies in paper 
cartons has necessitated the development of an opening device which will 
allow workers to quickly and easily open cartons to remove goods and 
supplies therein. The conventional carton opener, which has thus 
developed, is an elongated handle formed of complimentary side walls and a 
cutting blade, generally in the form of a razor blade, disposed between 
the sides. In use, one end of the cutting blade protrudes longitudinally 
from one end of the handle between the complimentary sides. When not in 
use, the fastening member which holds the sides together can be loosened 
and the blade retracted for storage between the sides. 
During the carton opening operation, however, the occasion often arises 
when a worker who is in a hurry and not using a sufficient degree of care 
will let the razor blade or cutter slip out of the carton wall or off the 
end thereof, with the result that the worker may injure himself or someone 
else in the immediate vicinity. 
Previous safety guards have been developed, as illustrated in U.S. Pat. No. 
2,730,800 to Bailey; U.S. Pat. Nos. 3,052,977 to Wise; 2,376,887 to 
Walters; and 3,781,988 to Jones. The guards illustrated and described in 
each of these patents are all similar in some respects, yet all suffer the 
same shortcoming. That is, the blade emerges from the carton being opened 
previous to the emergence of the guard. Therefore, at the end of a cutting 
stroke, there is a moment of danger when the guard is retracted and the 
blade is exposed. 
SUMMARY OF THE PRESENT INVENTION 
The present invention, on the other hand, eliminates this problem because 
the guard is so designed and operates as to emerge first from the carton 
wall prior to the emergence of the blade. Therefore, by the time the blade 
completes its cut and emerges from the surface of the carton, it is 
already protected and remains so until its next insertion through the 
carton wall. 
The construction of the guard which leads to such a desirable result 
includes a longitudinally reciprocal guard member which moves parallel and 
closely adjacent to the exposed edge of the blade from a point immediately 
beyond the tip end thereof to a retracted position in which the tip end 
and a portion of the blade is exposed. The blade exposure lasts only while 
a retracting pressure is applied to the guard which is normally spring 
biased to the safe position. 
It is therefore an object of the present invention to provide an improved 
guard for carton cutters. 
It is another object of the present invention to provide an improved cutter 
guard construction for carton openers of the type described in which the 
guard is normally spring biased to a safe position overlying the blade and 
its tip. 
It is a further object of the present invention to provide a carton opener 
guard of the type described wherein, as the cutting stroke is completed, 
the guard is moved to the safe position prior to the emergence of the 
blade and its tip, and provides immediate protection.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning now to the drawings, there is illustrated in FIGS. 1-3 the improved 
cutter guard G for conventional carton cutters C according to the present 
invention. Referring particularly to FIG. 1, the carton cutter is of 
fairly conventional design with a pair of side members 10, 12 held 
together by a clamping screw 14 through the body portions thereof. A 
longitudinally extending cutter blade 16, such as a razor blade or the 
like, protrudes longitudinally from the forward end of cutter C and is 
held in clamping relation between the side members 10, 12 and secured by 
clamping screw 14. The aforementioned construction is conventional and it 
is not believed that further description is required. 
The cutter guard means G includes a tubular housing 22 having a closed, 
inner end and an open, outer end. The housing is secured to the underside 
of the cutter C by welding, or the like. Alternatively, it may be molded 
integrally with the side walls 10, 12 to form the tubular member 22 when 
the sides are placed together. In any event, a shaft 24 having a shoe or 
plate 26 on the outer end thereof is mounted for reciprocal movement 
within the passageway in tubular member 22. A compression or coil spring 
28 is positioned between the inner end 27 of shaft 24 and the inner end of 
the passageway within tubular member 22. Stop member 25 extends downwardly 
from the shaft 24 and rides back and forth within a slot 30 in tubular 
member 22 to limit the outward movement of shoe 26. So arranged, the 
spring 28 normally biases the shaft 24 to the outermost position 
illustrated in FIG. 1. However, upon pressure exerted inwardly against the 
exposed surface of shoe 26, the shaft retracts against the spring pressure 
and exposes the tip end and a portion of the blade 16 for its useful 
purpose. Immediately upon a release of pressure, the shoe 26 moves 
outwardly to its safe position past the tip of blade 16 as illustrated in 
FIG. 1. 
Turning now to FIG. 3, it is believed that the invention, and particularly 
the heart of the invention is best illustrated by describing what occurs 
as the cutter C moves along a cut line X in carton Y. As the cutter C 
approaches the end of the carton wall, the guard G realizes a release of 
pressure against foot 26. Thus, as the foot clears the end of the wall, it 
is urged outwardly, so that at the moment the cutter blade 16 reaches the 
end of the carton, the guard is already in the safe position. It is 
important to emphasize this is not the case with known safety guards of 
the prior art. The cutting blade in all of the prior art reaches the end 
of the carton wall prior to the time the guard is moved to the safe 
position. This "moment of danger" even though it may be short, is long 
enough to inflict injury to the operator or anyone in the vicinity of the 
carton end. 
It is apparent that a preferred embodiment of the invention has been 
illustrated and described and various changes and modifications might be 
made without departing from the scope of the invention, which is set forth 
in the appended claims.