Synchronized folding knife

A folding knife having a blade and a pair of folding handles. The handles are channel shaped and bifurcated at one end for receiving one end of the blade. The bifurcated ends of the handles are attached to the blades by adjacent pivot pins. Rotation of the handles to the closed position encloses the blade inside the opposing channels of the handles. The ends of the handles are coupled by meshing gears pivoted on the same pins so that the handles must rotate together in opposite directions through 180.degree. between closed and open positions.

FIELD OF THE INVENTION 
This invention relates to a knife with a folding handle, and more 
particularly, to a knife in which the handle is in two pivoted sections 
which fully enclose the blade when in the folded position. 
BACKGROUND OF THE INVENTION 
Folding knives are well-known having two handle segments that are pivotally 
attached to one end of a blade and which rotate in opposite directions 
between a closed position in which the handles fully enclose the blade to 
an open position in which they form an extended handle. See, for example, 
U.S. Pat. No. 229,706, No. 881,294, No. 1,665,955, and No. 274,249. In the 
knives shown in each of these prior art patents, the handle is in two 
sections which, in the operative position, extend parallel to each other 
and are pivotally joined at one end to one end of the knife blade. The two 
handle sections can be rotated in opposite directions away from each other 
through 180.degree. to a closed position in which they fully enclose the 
blade of the knife. Optionally, some kind of latching arrangement holds 
the outer ends of the handle segments together when they are extended in 
the open position or rotated into the closed position. This arrangement 
requires that each of the handle sections be separately rotated through 
180.degree. between its opened and closed positions. Separately 
maneuvering the two handle sections between the two positions can be 
awkward and even hazardous. The maneuver usually requires the use of both 
hands to grasp each of the handle segments, and care must be taken to make 
sure that the fingers do not come in contact with the cutting edge of the 
blade in moving the handle segments into the closed position. 
SUMMARY OF THE INVENTION 
The present invention is directed to an improved folding knife of the type 
in which the handle is in two segments or sections which are pivotally 
secured to one end of the blade and rotate in opposite directions about 
separate axes between an open position and a closed position. The improved 
design of the present invention utilizes a pair of meshing gear sectors at 
the pivoted ends of the handles which rotate with the handle segments. The 
meshed gears link the handles together so that rotation of the handle 
sections is synchronized relative to the blade and the blade always 
bisects the angle formed between the two handle sections. This arrangment 
makes it easier for the operator to rotate the handles between the open 
and closed position. It also adds to the safety of the knife, since the 
blade is always maintained at equal angles with both handle sections. 
Another advantage is that the gears insure that the handle sections come 
together and contact each other to enclose the blade in the folded 
position without the knife edge coming in contact with a handle section. 
The gear sectors also provide a thumb or finger rest for certain cutting 
chores and help prevent the user's hands from slipping along the handle 
onto the blade during use.

DETAILED DESCRIPTION 
Referring to the drawings in detail, the knife of the present invention 
includes a blade 10 having a cutting edge 12. The blade is elongated and 
preferably terminates at one end in an outer point 14 and at the other end 
in a shank portion 16 of substantially uniform cross-sectional thickness 
and rounded to form a semicircular end 18. A handle 20 consists of two 
rotatable sections 22 and 24. Each of the handle sections is channel 
shaped to provide a pair of parallel side walls joined by a bottom wall, 
as best seen in the crosssectional view of FIG. 5. Each of the bottom 
walls, indicated respectively at 26 and 28, terminates short of the side 
walls to form a bifurcated ends 30 and 32, respectively, on each of the 
handle sections. The bifurcated ends receive the shank portion 16 of the 
blade and are pivotally joined to the blade by a pair of hinge pins 34 and 
36. 
The bifurcated ends 30 and 32 of the two handles are provided with gear 
sectors centered about the pivot axis of the pins 34 and 36 and with 
intermeshing gear teeth 40 and 42. The intermeshing gear sectors on the 
ends of the respective handle sections interlocks or synchronizes the 
relative rotation of the two handle segments in relation to the knife 
blade 10. Thus rotation of either handle section relative to the knife 
blade causes an equal and opposite amount of rotation of the other handle 
segment relative to the knife blade. Thus the axis of the knife blade 
always bisects the angle between the two rotating handle segments as they 
are rotated from the open position shown in FIG. 2 to the closed position 
shown in FIG. 1. Thus when rotated to the fully open position, both handle 
sections 22 and 24 are axially aligned with the blade 10. Similarly, when 
rotated to the fully closed position, as shown in FIG. 1, the handle 
sections, due to their channel shape, fit around and fully enclose the 
knife blade 10. 
Optionally, to lock the knife in either its fully closed or fully open 
position, the outer ends of the handle sections are bifurcated to receive 
a T-shaped latch member 46. The stem portion of the T-shaped latch member 
is pivotally secured to the handle section 22 by a pivot pin 48. The latch 
member 46 locks the outer ends of the handle sections together in either 
the open or closed positions by rotating the latch member so that the 
cross portion of the T-latch engages the bifurcated end of the handle 
section 24. It will be noted that the latch member 46 must be rotated 
through 180.degree. to move from the locking position with the handle open 
to the locking position with the handle closed. An optional alignment pin 
50 may be provided which projects from either side of the shank portion 16 
of the knife blade 10 and is engaged by notches in the handle sections 22 
and 24 when in the fully open position. While the pin 50 is not essential 
with the meshing gear sectors, it does provide additional strength in 
maintaining alignment between the handle sections and the blade when in 
the fully open position, and adding additional rigidity to the connection 
between the handle sections and the blade. 
It will be noted that the intermeshing gear sectors on the inner ends of 
the handle sections provide a number of advantages in addition to 
synchronizing the movement of the two handle sections. For instance, it 
will be seen that when the handle sections are moved to the closed 
position, the bottom wall 28 of the handle section will not come in 
contact with the knife edge 12 of the blade because the intermeshing gears 
cause the handle section 24 to first come in contact with the other handle 
section 22. Thus the knife edge is protected against impact with the 
handle even though the handle sections fully enclose the blade in the 
closed position. In this way the cutting edge of the blade is protected 
against any impact with its enclosing handle which would tend to dull or 
damage the cutting edge. Also, because the gear teeth must project beyond 
the margins of the handle to allow them to intermesh, they form a natural 
serration across the ends of the knife handle which tend to prevent the 
user's fingers from slipping along the handle into contact with the 
cutting edge of the blade when using the knife. Thus they serve as hand 
guards. The result is a knife which is improved both in utility and in 
safety.