Document shredding machine

A shredding mechanism having a continuous stripper to strip shredded material from the cutting surface of the shredding mechanism and having a bearing support for rotatably carrying the shafts of cutting cylinders. The stripper consists of upper teeth integrally formed on the inside surface of a top housing and bottom teeth integrally formed on the inside of a bottom base. The bearing support comprising two bearing plates integrally formed onto the inside surface of the bottom base. The bearing plates have semicircular indentations to rotatably carry the shafts of cutting cylinders.

BACKGROUND OF THE INVENTION 
This invention relates to a compact, easy to assemble, low cost paper 
shredder. 
In order to destroy documents to preserve their confidentiality, commercial 
shredders exist which cut the paper into narrow strips. Typically, the 
cutting is achieved by a series of circular cutters which are arranged 
along the axis of two rotating members. The cutters of one rotating member 
are offset so that the cutters pass between the cutters of the other 
member. 
The actual structure of the rotating members having cutters can be a solid 
bar of steel or similar material in which cutters and spacers are formed 
by machining so that the cutters and spacers are all integral to one 
another. Another structure has separate cylindrical members of a large 
diameter which are used as the cutters and are spaced apart by separate 
cylindrical spacers which are assembled on a shaft in an alternating 
relationship. 
The problem with these shredding devices is that the shaft must be mounted 
on bearing plates within the housing. This requires assembly of a number 
of parts and fasteners. The present invention solves these problems by 
providing molded bearing plates integral to the inside surfaces of the 
housing. Therefore, no parts or assembly is required to mount the shafts. 
Another problem with known and existing shredding devices is that after the 
paper has been cut into strips, the strips tend to wind around the cutters 
and spacers, clogging the cutting area. To solve this problem it has been 
suggested to provide a stripping means to strip away the cut paper. 
Typically, the stripping means consist of a serrated member or a comb type 
member having teeth which protrude in the spaces between the individual 
cutters. These members are located on the outward or post-shredder side of 
the cutting area. 
For example, U.S. Pat. No. 4,068,805 shows a comb means rigidly placed at 
the exit of the cutters and extending into at least one of the cutters. 
Another method of providing a stripping means is shown in U.S. Pat. No. 
3,033,064 which discloses a pair of combs each having a series of spaced 
teeth that project into the spaces between the cutters to remove the cut 
strips of paper. Each comb is rigidly mounted so that the teeth protrude 
into the side of the cutter shaft opposite of the cutting area. In 
addition, they are formed in a semi-circular shape so that they wrap 
around the series of cutters. 
In addition, it has been suggested to provide a comb type member before the 
cutters. The comb then guides the uncut paper into the cutters. U.S. Pat. 
No. 4,018,392 shows a pair of combers attached to support rods, each 
comber having a tongue protruding forward of the cutters to comb and 
direct the material being fed to the cutting surfaces of the cutters. 
The problem with these shredders and others is that a number of individual 
parts are required. Separate parts are required for the comb assembly and 
for mounting to the shredder housing. This increases the time and labor 
required to assemble the shredder which in turn increases the cost of the 
shredder. Therefore, the present invention is directed to a paper shredder 
that has few parts and is easy to assemble. This will result in a paper 
shredder that has a lower cost than conventional paper shredders. 
SUMMARY OF THE INVENTION 
The invention provides a continuous stripper for removing cut material from 
the cutting area of a paper shredder. The stripper extends from the inside 
surface of the top housing through the cutting area to the inside surface 
of the bottom base. The stripper consists of upper teeth integrally formed 
on the inside surface of the top housing. The upper teeth substantially 
abut lower teeth integrally formed on the inside surface of the bottom 
base to form the continuous stripper. The continuous stripper thus 
prevents the cut material from winding around the cutting mechanism and 
clogging the shredder. 
The invention further provides a paper shredder having a molded top housing 
with a feed opening and a molded base with a discharge opening. When 
joined, they form the outside structure of the paper shredder. 
Both the top housing and the base have teeth that are integrally formed to 
their inside surfaces. The teeth on the top housing have a female end at 
their tip, whereas the teeth on the base have a male end at their tip. 
When the top housing and the base are joined, the teeth substantially abut 
to form a continuous stripper. The stripper extends from the top housing 
through the spaces formed by the spacers and to the bottom of the base. 
This arrangement provides a stripper both before and after the cutter 
surface. The stripper can guide the paper into the cutting surface and 
prevent the cut paper strips from clogging the cutting area. Furthermore, 
because the teeth are molded as part of the housing and the base, no 
mounting parts or assembly labor is required for the stripper. This 
results in a shredder having a cost less than that of a conventional paper 
shredder. 
In addition, there are provided a pair of top debris plates and a pair of 
bottom debris plates. The top debris plates are located inside the top 
housing opposite each other and extend laterally at the sides of the feed 
opening. In a similar fashion, bottom debris plates are located inside the 
bottom housing opposite each other and extend laterally at the sides of 
the discharge opening. Each plate has a pair of semicircular indentations 
so that when the top housing is joined to the bottom housing the top 
debris plates and the bottom debris plates will prevent stripped material 
from entering the shredder, yet allow the shafts of cutting cylinders to 
pass through. 
The invention also provides a bearing support integrally formed on the 
bottom base to rotatably carry the shafts of cutting cylinders provided in 
the shredder. The bearing support consists of two bearing plates formed on 
the inside surface of the bottom base and located opposite each other. 
Each bearing plate has two semicircular indentations formed into the 
bearing plate to carry the shafts. 
The top housing has bearing plates opposite each other and integrally 
molded on the inside surface. The bearing plates have two semicircular 
indentations formed in the plate. The indentations cooperate with the 
respective semicircular indentations provided in the bearing plates 
located on the inside surface of the base. 
Two cutting cylinders are mounted parallel to each other so that they 
interleave to form a nip. The cutting cylinders have cutter portions 
alternately spaced on a central shaft. Preferably, the cutting portions 
are cutter discs alternately spaced by spacers. When the shafts are 
rotated in opposite directions, the cylinders draw paper into the nip and 
cut or shred it into thin strips. The shafts are rotatably supported by 
the semicircular indentations located on the bearing plates of the base. 
When the top housing is joined to the base, the shafts are substantially 
enclosed by the cooperating indentations. 
In this way, metal bearing plates, distance shafts, and fasteners which are 
normally used, can be omitted. The result is that the assembly is 
simplified. Furthermore, such a design results in a paper shredder that 
has a low cost. 
Alternatively, the bearing plates are a separate formed structure. In this 
case, a pair of bearing plates are located opposite each other. The 
bearing plates are formed such that they are held in place when the top 
housing is joined to the bottom base. 
In another embodiment, the debris plates rotatably carry the shafts of the 
cutting cylinders. Thus, separate bearing plates are not required. In this 
case, when the top housing is joined to the bottom base, the semicircular 
indentations of the top debris plate and the bottom debris plate cooperate 
to support and substantially enclose the shafts of the cutting cylinders.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS 
FIG. 1 illustrates a paper shredding machine having top housing 100 and 
bottom base 106. Paper is fed into feed opening 104 located on the top 
surface of top housing 100. The paper is shredded by cutting cylinders 
230, shown in FIG. 2, and is ejected from discharge opening 400, shown in 
FIG. 4, located on bottom base 106. 
FIG. 2 shows top housing 100 with sides 102 that are recessed at the bottom 
to provide top shoulder 200. Top shoulder 200 has fingers 202 extending 
downward. Base 106 also has a recessed edge to provide base shoulder 204 
which will positively couple with top shoulder 200 provided in top housing 
100 when top housing 100 is joined to base 106. Base shoulder 204 is 
interrupted by slits 206 which will engage fingers 202 to further provide 
a secure fit between top housing 100 and bottom base 106. 
Furthermore, base 106 has protrusions 208 located on the inside bottom of 
the base and contacting base shoulder 204. Protrusions 208 extend upward 
to guide and to contact top shoulder 200 of top housing 100 to further 
provide a secure fit when top housing 100 and base 106 are joined. 
Top housing 100 has feed opening 104 located on the top surface of top 
housing 100. Feed opening 104 is sized to allow several sheets of paper to 
be fed into it. In addition, feed opening 104 is tapered downward on 
opposite sides to assist the travel of the paper downward to and through 
cutting cylinders 230. The ends of the tapered portion are formed into a 
series of upper teeth 210 that extend downward as better seen in FIG. 3. 
Upper teeth 210 are spaced apart at regular intervals to provide space 212 
between each tooth. Also, upper teeth 210 on one side extend down while on 
the opposite side there is space 212 between the teeth. Thus, upper teeth 
210 on both sides extend downward in an alternating fashion to form 
one-half of a stripper means. As shown in FIG. 4, teeth 210 have a female 
end 402 at the distal end provided for mating purposes. 
The inside surface of top housing 100 has at opposite ends top debris plate 
222, 224 of any suitable width. At the first end, top debris plate 222 has 
semicircular indentations 226 and 228. At the second end, top debris plate 
224 has similar semicircular indentations. 
The inside surface of bottom base 106 has at opposite ends bottom debris 
plate 254, 256 of any suitable width. At the first end, bottom debris 
plate 254 has semicircular indentations 258 and 260. At the second end, 
bottom debris plate 256 has semicircular indentations 262, 264. When top 
housing 100 is joined to bottom base 106, top debris plate 222, 224 and 
bottom debris plate 254, 256 substantially cooperate such that shafts 236 
of cutting cylinder 230 are surrounded. 
In a first embodiment, the inside surface of top housing 100 has on 
opposite ends top bearing plate 214, 216 molded to the inside surface of 
top housing 100. At the first end, bearing plate 214 has semicircular 
indentations 218, 220. At the second end, bearing plate 216 has similar 
semicircular indentations. The inside surface of base 106, as shown in 
FIG. 2, has at opposite ends bottom bearing plate 242, 244 molded to the 
inside surface of base 106. On each bottom half bearing plate 242, 244 
there are semicircular indentations 246, 248, 250, 252 provided to carry 
the load of cutting cylinders 230. 
In a second embodiment, shown in FIG. 5, there is located on one end of 
bottom housing 106 bearing support plate 500 and a similar bearing support 
plate on the opposite end. As shown in FIG. 5, there is provided holes 
504, 506 in bearing plate 500, so that the shafts 236 can pass through. 
There are similar holes in the opposite bearing plate. Each hole 504, 506 
and the holes on the opposite bearing support have shoulder 508. Gears 510 
are fixably attached to each end of shafts 236 so that gears 510 are 
cooperatively meshed. Gears 510 are provided with shoulder 512 to 
rotatably engage with shoulder 508 on holes 504, 506 in bearing plate 500 
and the similar respective holes in the opposite bearing plate. Bearing 
plate 500 is formed such that when top housing 100 is joined to bottom 
base 106 bearing plate 500 is securely supported. 
In a third embodiment, the bearing plate may also serve as the debris 
plate. In this case, the bottom debris plate 254, 256 would be of suitable 
width to rotatably support shafts 236 of the cutting cylinders 230. 
As shown in FIG. 4, the inside surface of base 106 has a discharge opening 
400 to allow the cut strips of paper to fall through. In addition, there 
are a series of lower teeth 266, better seen in FIG. 2, that extend upward 
and are formed on opposite sides of the inside portion of discharge 
opening 400. Lower teeth 266 are spaced apart at regular intervals to 
provide space 268 between each tooth. Also, lower teeth 266 on one side 
extend upward while on the opposite side there is space 268 between the 
teeth. Thus, lower teeth 266 on both sides extend upward in an alternating 
fashion to form one-half of a stripper means. 
As shown in FIG. 4, lower teeth 266 have a male end 270 at the distal end 
which will mate with female end 402 in upper teeth 210 when top housing 
100 is joined with base 106. When top housing 100 is joined with base 106, 
upper teeth 210 and lower teeth 266 form a completed stripper means that 
extends downward from feed opening 104 through cutting cylinders 230 to 
discharge opening 400. 
Cutting cylinders 230 are arranged in parallel and interleave to form a 
nip. Each cutting cylinder 230 contains cutter discs 232 alternately 
spaced by spacers 234 and mounted on central shaft 236. 
An appropriate gear 240 driven by reversible motor 238 is coupled to shafts 
236 to drive cutting cylinders 230 in opposite directions. This action 
will allow cutter discs 232 to grasp and pull the paper into and through 
the cutting area so that the paper is cut into thin strips. It will be 
appreciated that a suitable switch can be used to actuate the motor so 
that the gear can turn in either a forward or a reverse direction. 
Alternatively, an electric eye can be provided in feed opening 104 to 
automatically activate motor 238. 
The interaction between cutting cylinders 230 and upper teeth 210 and lower 
teeth 266 can be seen in FIG. 4. Lower teeth 266 alternately extend upward 
in the spaces between cutter discs 232 provided by spacers 234. 
Simultaneously, upper teeth 210 alternately extend downward in the spaces 
between cutter discs 232 provided by spacers 234. Thus, when top housing 
100 and base 106 are joined, teeth 210 and 266 mate to form continuous 
strippers which are located in the void created by spacers 234. The 
strippers guide the paper to the cutting area and strip debris from the 
cutting area keeping it clean and free from jamming. 
Of course, it should be understood that a wide range of changes and 
modifications can be made to the preferred embodiment described above. It 
is therefore intended that the foregoing description illustrates rather 
than limits this invention, and that it is the following claims, including 
all equivalents, which define this invention.