Partial cut shearing device

A device for partially shearing single or multiple sheets of material comprising a base having a recess and a lower blade fixed in the recess. A pair of movable blades having opposed ends are pivotally attached to the base at one end. A lost-motion connecting link connects the free ends of the pair of movable blades together and is connected to a hydraulic piston which moves the link a limited distance towards the base, thereby to rotate both movable blades relative to the fixed blade with a scissors-like action. When the pair of blades is moved towards the lower blade, the material is cut inward from both sides or edges of the material, leaving an inner uncut portion of material having a width which corresponds to the stroke of the movable blades.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a device for partially shearing thin, 
flat, hard material with opposing blades having zero clearance. More 
particularly, the invention relates to a device for cutting the material 
inward from both sides to leave an inner uncut portion of material. 
2. Description of the Prior Art 
In the manufacture of electrical power transformers, it is necessary to cut 
a large number of thin sheets of transformer laminations from a sheet or 
from a roll supply of, for example, amorphous steel transformer core 
material. Such cut laminations, which may be about 0.001 inch thick, are 
then stacked to form a transformer core. 
There are many known devices for shearing such thin materials inwardly from 
an edge of the material. It is also known to use devices which cut 
material from both sides. Thus, U.S. Pat. Nos. 3,901,116 and 4,619,166 
disclose double-bladed saws which advance inward from both sides to cut 
the material. 
However, the above-mentioned devices completely cut the material from edge 
to edge, failing to leave an inner uncut portion. In modern processing, it 
is desirable to treat an entire sheet of material at once and, upon 
completion of processing, to separate the sheet into more manageable 
lengths for shipping or further processing. 
The present invention provides an apparatus and method for partially 
shearing an entire sheet of material but leaving uncut tab portions which, 
upon completion of material processing, may be easily broken to separate 
the sheet into discrete lengths. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a device for partially 
shearing single or multiple sheets of material. In accordance with the 
invention, the device comprises a base having a recess with a lower blade 
fixed in the recess and a pair of movable blades having opposed ends which 
have zero clearance with the lower blade. One end of each of the movable 
blades is attached to the base and the other end is free. Means for 
connecting the free ends of the pair of movable blades together is located 
between the free ends to space the free ends from each other a 
predetermined distance wherein, when the pair of blades is moved towards 
the lower blade, the material is cut inward from both sides, leaving an 
inner uncut portion of material having a width which corresponds to the 
predetermined distance. 
Another object of the present invention is to provide a shearing device for 
making a partial cut, as described above, which includes a biasing means 
which urges the cutting edges of the movable blades against the cutting 
edge of the lower blade so as to maintain minimal clearance between the 
cutting edges when the material is being cut, regardless of the thickness 
of the material. 
A further object of the invention is to provide a shearing device which 
leaves an uncut tab disposed between partially cut lengths of the 
material. After the sheet of material has been treated, the tabs can be 
broken to separate the lengths. 
Still a further object of the invention is to provide a method for 
partially shearing single or multiple sheets of material into lengths 
comprising the steps of driving a pair of movable blades towards a lower 
blade fixed in a base, cutting the material inward from both sides, to 
leave an inner uncut portion of material which corresponds to the 
predetermined distance. 
Other features and advantages of the present invention will become apparent 
from the following description of the invention which refers to the 
accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In accordance with the invention, the shearing device is capable of 
partially shearing single or multiple sheets of transformer steel material 
18. For example, the device will cut amorphous magnetic material sheets 
which are extremely hard material, and are as thin as 0.001". 
As depicted in FIG. 1, the device includes a base 12 having a rectangular 
recess 14 formed therein. A lower blade 16 is fixed in the recess, as 
shown in FIG. 2. The material 18 is fed along base 12 toward the cutting 
edge of blade 16 in the direction A in FIG. 2. 
A pair of movable blades 20, 22 is attached to base 12 at their respective 
lower ends 19. Each blade includes a hardened cutting edge 24, designated 
by the dashed lines in FIGS. 1 and 2. The lower ends 19 are pivotally 
attached to the base 12 by respective bias assemblies 32 which urge the 
movable blades 20, 22 against lower blade 16 to maintain minimal or zero 
clearance between the cutting edges of movable blades 20, 22, and lower 
blade 16 when the material is being sheared. 
Referring to FIG. 3, each biasing assembly 32 comprises a shaft 33 
extending from the base 12, with each shaft having a free threaded end. 
Shaft 33 extends from base 12 through its associated movable blade 20, 22. 
A spring 36 is provided on shaft 33. A nut 34 is disposed on the threaded 
end of shaft 33 to compress and secure the spring 36 against the outside 
surface of the movable blade. 
When a sheet of material 18 is being partially sheared by the movable 
blades 20, 22 and lower blade 16, the material tends naturally to separate 
the blades by a distance at least equal to the thickness of the material. 
However, spring 36 provides a biasing force against the respective movable 
blade to urge the cutting edges of the movable blades against the cutting 
edge of the lower blade, resulting in zero or minimal clearance 
therebetween. Therefore, the present invention can be used to partially 
shear varying thicknesses of material, ranging from a very thin sheet of 
material to multiple sheets of thick material. 
As shown in FIG. 1 and 2, the upper end 21 of each movable blade 20, 22 is 
free to rotate in relation to base 12. Each end 21 includes a lost-motion 
slot 23. A connecting means 30 is located between the free ends 21 and is 
movable in slots 23. 
In accordance with the invention, the movable blades can be driven downward 
a given distance to move blades 20, 22 toward lower blade 16. The driving 
force can be supplied by a hydraulic cylinder 26. A suitable stop (not 
shown) can adjustably limit the stroke of the plunger of cylinder 26. When 
the movable blades are driven toward lower blade 16, the material or web 
18 is cut inward from both sides leaving the inner uncut portion 40. Uncut 
portion 40 typically may have a length of 3/8 inch. The length of uncut 
portion 40 can be adjusted by changing the length of the stroke of 
cylinder 26 or the length of the plunger. 
As shown in FIG. 4, the uncut portion comprises a tab 40 disposed between 
partially cut lengths 28 of the material 18. The tab allows the material 
to be further processed as a strip, for example, for annealing, cleaning, 
or the like. After processing, the tab 40 is broken or slit and the 
material is easily separated into lengths 28 which are stacked to form a 
core for a transformer. 
In accordance with the invention, the material to be cut may be moved 
intermittently into position between the blades to partially cut the 
sheets of material into discrete lengths. As shown in FIG. 2, an actuator 
50, provided for this purpose, steps the material 18 toward the blades at 
intervals corresponding to the desired dimensions of the finished lengths 
28. 
In operation, actuator 50 has means to grip and move web 18 to a rest 
position between lower blade 16 and upper movable blades 20, 22. When the 
hydraulic cylinder 26 is actuated, connecting link 30 moves downward, 
thereby moving blades 20, 22 downward simultaneously. Web 18 is cut 
through a scissor-type motion inward from both sides. However, due to an 
incomplete cutting stroke, the inner uncut portion 40 remains in the 
center of the material. Blades 20, 22 then return to their original 
position, and actuator 50 again steps the material 18 a distance, 
corresponding to the desired length 28 to make a new incomplete cut. 
The sheet of material is then further processed, with all sections or 
laminations held together by the uncut tabs. Upon the completion of 
processing, the uncut tab portions 40 can be easily broken to separate the 
material into lengths 28. 
Although the present invention has been described in relation to particular 
embodiments thereof, many other variations and modifications and other 
uses will become apparent to those skilled in the art. It is preferred, 
therefore, that the present invention be limited not by the specific 
disclosure herein, but only by the appended claims.