Background Art Due to its ease of use, a rotary cuter is used in place of scissors for cutting material such as fabric or paper. In general, a rotary cutter includes a head part having a rotating round blade and a grip part for a user to grip and secure the head part. Such a rotary cutter facilitates curved or straight cutting of thin material. Although the blade of a rotary cutter can be as sharp as a razor, it easily becomes blunt from contact with other objects or wear and thus must be changed.

An example of the rotary cutter of the prior art is shown in Figs. 1 and 2. This rotary cutter has a holder 10 having a grip part 11 for gripping by the user, a blade-holding part 12 with an elliptical hole 12a at the center. and a blade 20. A push button 30 with a boss 31 is provided in the blade-holding part 12. Pushing the button 30 causes the boss 31 to move along the elliptical hole 12a to a blade-exposing position, shown in Fig. 2 by the dotted line. The cutter is also provided with a locking means to lock the blade in the blade-exposing position and a release button 15 to release the push button 30 from the locked position. To cut material, the cutter with its blade in the blade-exposingposition is pressed against the material.

The blade 20 is rotatably attached to the boss 31 by a pivot 50 and a nut 40. A wave spring 60 and a fan-shaped cover 70 are provided between the pivot 50 and the blade 20. The resistance against the rotation of the blade 20 can be regulated by varying the screwing force of the nut 40 on the pivot 50.

The above cutter, however, has several shortcomings. First, in order to

change a blunt blade, a user must dissemble the nut, pivot, wave spring and cover, and reassemble them once the blade has been replaced. Second, because the user must touch the blade to change it, the user is exposed to the danger of being cut by the edge of the blade. Third, the new, bare blades can be easily damaged by merely being hit against an object during changing or handling. Lastly, a used loose blade can be a safely concern after being separated from the cutter. Thus, there is a need for a rotary cutter that will meet these shortcomings of the prior art.

Disclosure of Invention It is an object of the present invention to provide a rotary cutter having a blade cartridge that facilitates the quick and easy changing of a blade.

It is another object of the invention to provide a rotary cutter having a blade cartridge that enables a blade to be safely changed.

It is yet another object of the invention to provide a rotary cutter having a blade cartridge that protects the edge of the blade from being damaged during changing.

It is a further object of the invention to provide a blade cartridge that allows a blunted blade to be safely disposed.

It is yet a further object of the invention to provide a rotary cutter with a blade cartridge that remains firmly secured despite application of any side forces, thereby preventing any undesired rotation.

The present invention meets the needs of the prior art by providing a rotary cutter with a blade cartridge and a grip coupled to the cartridge for handling the cutter. The blade cartridge includes an upper cover, a lower cover, and a biade being supported therebetween. Once the blade becomes dull, the entire cartridge is detached from the grip and replaced. Thus, there is no need for a user to come in direct contact with the blade edge in order to replace a dull blade. With the present invention, the blade can be safely and easily replaced.

Further, the lower cover of the blade cartridge of the present invention

is rotatable between a closed position and an open posit ion. In the closed position, the lower cover houses the blade, thereby protecting the edge of the blade when the cutter is not in use. The blade cartridge is removed from the grip of the cutter with the lower cover preferably in the closed position. Thus, the chances that the user will be cut by the edge of the blade or that the blade will be damaged during the changing process are reduced. Once the blade cartridge has been detached from the grip of the cutter, the blade remains housed within the cartridge. Thus, the used blade can be safely disposed.

In addition, the blade cartridge of the present invention remains firmly secured to the grip despite the application of any side forces. This is attributed to the anti-rotation means that is provided in the coupling arrangement between the blade cartridge and the grip. The blade cartridge has a locking protrusion extending from one end that mates with a locking aperture carried by the grip. To couple the cartridge with the grip, the protrusion is inserted into the aperture, thereby acting against a spring biased pusher within the aperture, and then rotated 90 °. The anti-rotation means includes a locking recess provided on the blade cartridge and a spring biased locking member that is carried by the grip. Once the cartridge is rotated with respect to the grip, the locking member with the locking recess, thereby preventing and undesired rotation between the blade cartridge and the grip.

Brief Description of Drawings The invention will now be further described, by way of example only, with references to the accompanying drawings, in which ; Fig. 1 illustrates an exploded perspective view of a prior art rotary cutter.

Fig. 2 shows the cutter of Fig. 1 with the blade exposed.

Fig. 3 illustrates an exploded perspective view of the rotary cutter with a blade cartridge made in accordance with the present invention.

Fig. 4 shows a cross sectional view of the blade cartridge.

Fig. 5a and 5b are side views of the protective cover of the cartridge in its open and closed positions.

Fig. 6a shows a cross sectional view of the blade cartridge taken along the line A-A of Fig. 5a.

Fig. 6b shows a cross sectional view of the blade cartridge taken along the line B-B of Fig. 5b.

Fig. 7 is an exploded perspective view of another embodiment of a rotary cutter with a blade cartridge made in accordance with the present invention.

Fig. 8a is a plan view of the assembled cartridge in its open position.

Fig. 8b is a plan view of the assembled cartridge in its closed position.

Figs 9a and 9b are exploded views of another embodiment of a rotary cutter with a blade cartridge made in accordance with the present invention.

Fig. 10a is a side view of the upper cover of the blade cartridge of Figs.

9a and 9b.

Fig. 10b is a detail view of the locking ribs on the upper cover of the cartridge of Fig. 10a.

Fig. lOc is a cross sectional view taken along line C-C of Fig. 10b.

Fig. 10d is a cross sectional view taken along line D-D of Fig. 10b.

Fig. 11 is a partial cross sectional view of the assembled cutter of Figs.

9a and 9b.

Fig. 12 shows an exploded perspective view of yet another embodiment of the blade cartridge and the rotary cutter made in accordance with the present invention.

Fig. 13 shows a side view of the assembled blade cartridge of the embodiment of Fig. 12.

Figs 14a and 14b show the operation of the blade cartridge of Fig. 12.

Fig. 15 is a perspective view of the coupling arrangement for the blade cartridge of Fig. 12.

Fig. 16 is a perspective view showing the inside of the locking block of

the cutter of Fig. 12.

Fig. 17 is a cross sectional view of the locking block and the grip before being coupled with the cartridge.

Figs 18a and 18b show the interaction between the locking block and the locking protrusion.

Modes for Carrying Out the Invention Referring now to the accompanying drawings a blade cartridge of the present invention is shown in Figs. 3 and 4. The cartridge 100 generally comprises a cover unit having a blade exposing section 115 ; a round blade 140 rotatably mounted in the cover unit and partly exposed through the blade exposing section 115 ; and a protective cover 130 slidably combined with the cover unit to open at close the blade exposing section 115.

The cover unit includes an upper cover 110 having a boss or shaft 111 to rotatably support the blade 140 and a lower cover 120 with a passageway 121 through which the boss 111 extends. A nut 160 is screwed onto the boss 111 to regulate the frictional resistance of the blade 140 against the upper and lower covers 110, 120. The upper and lower covers 110,120 are made of synthetic resin and thus are elastically adjustable to the screwing force of the nut 160. The rotational resistance of the rotating blade 140 can be regulated by varying the pressure imposed by the nut 160 on the upper and lower covers 110,120. A sleeve 150 is further provided between the boss 111 and the blade 140 to prevent wear of the boss 111.

Guide ribs 112,122 are formed in a circular arc shape on the outer surface of each of the upper and the lower covers 110,120. Engaging ribs 131,132 are formed on the protective cover 130 and slidably engage with the respective guide ribs 112,122. Therefore, the protective cover 130 can open or close the blade exposing section 115 without slipping away from the upper and lower covers 110, 120.

As illustrated in Figs. 6a and 6b, protrusions 130a, 130b are formed on the inner surfaces of the protective cover 130 and corresponding recesses are formed on the upper and lower covers 110, 120. The protrusions 130a, 130b can be elastically locked with the recesses 110a, 110b, 120a, 120b. As a result, the protective cover 130 can be held either in the closed position or the open posit ion of the blade exposing section 115, as shown respectively in Figs. 5a and 5b.

As shown in Fig. 3 the cover unit is detachably coupled to a grip 180 by a coupling arrangement. In the embodiment of Fig. 3 the coupling arrangement comprises a connection rib 113 formed at one end of the upper cover 110 and a groove 190 formed at one end of the grip 180 for slidably coupling with the connection rib 113.

The blade cartridge 100 of the embodiment of Fig. 3 is assembled by ultrasonic-junctioning the lower cover 120 to the upper cover 110 with the blade 140 and the sleeve 150 contained therebetween. Thereafter, the protective cover 130 is placed onto the upper and lower covers. The cartridge is then coupled to the grip 180 by mating the rib 113 and the groove 190.

To use the rotary cutter to cut materials such as fabric, a user first moves the protective cover 130 to the open position, thereby exposing the blade at the blade exposing section 115. The user then presses and moves the cutter against the fabric to be cut, thereby rotating the blade 140 against the fabric.

When the cutter is not in use, the protective cover is moved to close the blade exposing section 115 in order to protect the blade 140 and to prevent safety problems. To change a used blade 140, the whole cartridge 100 is detached from the grip 180 and replaced.

Another embodiment of a rotary cutter made in accordance with the present invention is shown in Fig. 7. The cutter of Fig. 7 includes a blade cartridge and a grip 300, the blade cartridge having an upper cover 400, a lower cover 500, and a blade 140. The upper cover 400 has a boss 402 at its center to rotatably support the blade 140. a first guiding rib 401 formed in circular arc shape along the rim of the upper cover 400, and a first blade exposing part 408 to expose a part

of the blade 140. The lower cover 500 includes a control knob 501 with a passageway at its center, a second guiding rib 502 corresponding to the first guiding rib 401, and a second blade exposing part 505 corresponding to the first blade exposing part 408. The cartridge further includes a bolt 600 extending through the control knob 501 and the boss 402 to combine the upper cover 400 to the lower cover 500, and a nut 620 that is screwed onto the bolt 600. A wave washer 610 is also provided between the nut 620 and the upper cover 400 to regulate the rotational resistance of the blade 140 by varying the screwing force of the nut 620.

As can be seen in Fig. 7, a first and second locking slot 405, 406 and a first and a second stopper 403,404 are formed at opposite ends of the first guiding rib 401 on the upper cover 400. The lower cover 500 is further provided with a locking piece 503 and a holding piece 504 formed at opposite ends of the second guiding rib 502. As described below, the locking piece 503 and the holding piece 504 interact with the stoppers 403,404 and the slots 405,406 to lock the blade cartridge in either an open position or a closed position.

As can be seen in Fig. 7, the upper cover 400 is detachably coupled with the grip 300 by a coupling arrangement. The coupling arrangement comprises a key 407 formed at one end of the upper cover 400 and a key hole 310 formed at one end of the grip 300. The key 407 is inserted into the key hole 310 and then is rotated to be locked. While the key 407 is positioned in the key hole 310, either the blade cartridge or the grip 300 is rotated 90° with respect to the remaining element to couple the blade cartridge and the grip together.

To cut material such as paper or fabric, the user presses and moves the cutter along the material with the blade 140 exposed through the first and second blade exposing parts 408,505. The rotational resistance of the blade 140 can be regulated by varying the screwing force of the nut 620. The locking piece 503 of the lower cover 500 is locked at the second locking slot 406 of the upper cover 400 to keep the blade 140 exposed. While in this open position, the holding piece 504 is engaged by the first stopper 403, thereby ensuring that the locking piece 503 does not slip out of engagement with the second locking slot 406.

When the cutter is not in use, as shown in Fig. 8b, the locking piece 503 is freed from the second locking slot 406 by rotating the control knob 501 clockwise.

The locking piece is slid along the first guiding rib 401 until it slips into engagement with the first locking slot 405. At the same time, the holding piece 504 is moved along the first blade exposing part 408 and then is stopped by the second stopper 404. In this closed position, the blade 140 in the blade exposing part 408 is placed within the second guiding rib 502 of the lower cover 500.

To change the used blade 140, the blade cartridge is rotated 90° with respect to the grip 300. The blade cartridge is then separated from the grip 300, thereby removing the key 407 from the keyhole 310. A new blade cartridge can then be placed onto the grip.

The rotary cutter of Figs. 1-8b facilitates the changing of a used blade by providing a blade cartridge that can be replaced. Thus, there is no need to disassemble the blade from the upper and lower covers in order to replace the blade.

Further, the blade is protected by the use of the protective cover of the cartridge of the second guiding rib of the lower cover. Thus, the chances that the user will be cut by the edge ofthe blade or that the bladewill be damaged during the changing process are reduced. In addition, because the blunt blade is contained within the cartridge after it is changed, the dangers associated with handling the blade are minimized.

Another embodiment of the cutter of the present invention is shown Figs.

9-11. Similar to the cartridges discussed above, the cartridge 210 of Figs. 9-11 includes a blade 212, an upper cover 214, and a lower cover 217. The upper cover 214 includes a boss or shaft 219 extending from its center for rotatably supporting the blade 212, a first guiding rib 221 formed in a circular arc shape along the peripheral edge of the upper cover 214, and a first blade exposing section 223 at which a portion of the blade 212 is exposed. The upper cover 214 further includes a groove 225 provided adjacent to the first guiding rib 221. The lower cover 217 includes a control knob 228 at its center with a passageway 230 extending therethrough, a second guiding rib 232 formed in a circular arc shape adjacent

the peripheral edge of the lower cover 217, and a second blade exposing section 234 at which a portion of the blade 212 is exposed.

To hold the elements of the cartridge 210 together, the shaft 219 of the upper cover 214 extends through the passageway 230 of the lower cover 217. A washer 236 is press-fitted onto the end of the shaft 219. It is the cross-fit between the washer 236 and the shaft 219 that holds the elements together. The washer 236 is preferably made of metal. The lower cover 217 is then provided with a cartridge cap 239 to enclose the inner workings of the cartridge 210. Once assembled, the lower cover 217 is rotated about the shaft 219 in order to move the cartridge 210 between the open and closed positions. During this rotational movement, the guiding rib 232 of the lower cover moves along the groove 225 of the upper cover.

As shown in Fig. 10a, the upper cover 214 is provided with a stopper projection 241 in the groove 225 adjacent one of the ends of the first guiding rib 221. The projection 241 engages the guiding rib 232 of the lower cover 217 to stop any further clockwise rotation of the lower cover 217 once it has been rotated to the closed position.

The upper cover 214 is further provided with two sets of locking ribs 243, 245, a set adjacent to each end of the guiding rib 221. The lower cover 217 is also provided with a further locking rib 247 adjacent to one end of its guiding rib 232. The locking rib 247 of the lower cover 217 interacts with the locking ribs 243,245 of the upper cover 214 to ensure that the cartridge remains in the desired position. As the lower cover 217 is rotated to the closed position, the locking ribs mate to lock the lower cover 217 in that position. Specifically, the single rib 247 of the lower cover 217 is placed between the locking ribs 243 of the upper body 214. As the lower cover 217 is rotated back to the open position, the locking rib 247 of the lower cover 217 engages with the ribs 245 to lock the lower cover 217 in that position.

The elements of the blade cartridge of Figs. 9-11 are injection molded, with the exception of the blade.

A further embodiment of the rotary cutter of the present invention is shown

in Figs. 12-18. The rotary cutter 300 generally comprises a blade cartridge 350 rotatably supporting a blade 351, a coupling arrangement 340,352, and a grip 330 for handling by the user.

As can be seen in Figs. 12-15, the blade cartridge 350 includes an upper cover 353 and a lower cover 354 that together rotatably support the blade 351.

The upper cover 353 has a first through hole 353a at its center and a first edge exposing portion 353c for exposing a part of the blade 351. The upper cover 353 further includes a locking body 352 extending from its one end. The lower cover 354 has a second through hole 354a and a second edge exposing portion 354c for exposing a part of the blade 351. First and second guide ribs 353b, 354b are formed respectively along each peripheral edge of the upper cover 353 and the lower cover 354. The guide ribs, however, are not formed along the first and second edge exposing portions 353c, 354c.

The upper and lower covers coupled together in the following manner.

Referring to Fig. 15. a cylindrical controlling boss 358 is formed at an outer surface of the lower cover 354. The boss 358 is coaxially aligned with the second through hole 354a. A couple of elastic strips 358a, 358b are provided in the wall of the controlling boss 358.

As shown in Figs. 13 and 15, a bolt 357 is inserted through the first and second through holes 353a, 354b. The bolt 357 has as a stopper 357a at the side of its head that can be elastically locked by elastic strips 358a and 358b. A wave spring 355 is provided between the head of the bolt 357 and the lower cover 354.

The free end of the bolt is provided with a nut 356. A sleeve 359 is further provided between the upper cover 353 and the lower cover 354, to which the blade 351 is rotatably connected. The resistance to the rotation of the blade 351 can be regulated by changing the contact force between the upper cover 353 and the lower cover 354. Adjusting the nut 356 causes the wave washer to correspondingly change the contact force between the covers.

A protective cap 360 is further provided for protecting the elastic strips 358a, 358b during the rotation of the lower cover 354. As can be seen in Fig. 13

the cap 360 is placed over the controlling boss 358. The cap 360 is provided with jaws 361, 362 that lock into locking apertures 358c, 358d, which are formed at the lower end of the outer surface of the controlling boss 358. This interaction between the jaws and the locking apertures secures the connection between the protective cap 360 and the control ling boss 358. To further ensure this connection, a longitudinal linking groove 358e is provided on the outer surface of the controlling boss 358. The groove 358e mates with a rib 363 formed on the inner surface of the protective cap 360.

The elastic strips 358a, 358b of the controlling boss 358 interact with the stopper 357a of the bolt 357 to lock the blade cartridge in either the open or closed position. This interaction ensures that the cartridge remains in the desired position. Thus, the chances of the blade cartridge being inadvertently placed in the open position are reduced.

This embodiment of the cutter further comprises an arrangement for coupling the blade cartridge to the grip, the coupling arrangement including anti-rotation means for preventing the undesired rotation of the cartridge with respect to the grip. Referring to Figs. 12 and 16-18, the blade cartridge includes a locker body 352 with a locking protrusion 352a extending therefrom and a guiding groove 352c.

The grip includes a locking block 340 having a locking aperture 341 and a guide ball 345. The anti-rotation means comprises a couple of slanted steps 341a, 341b formed at the edge of the inner surface of the locking aperture 341. As can be seen in Fig. 16, these steps are located at opposite end of the aperture 341. When the locking protrusion 352a is inserted into the locking aperture 341 and rotated, the slanted steps 341a, 341b engage the protrusion and prevent rotation beyond 90°. Also during this insertion and rotation, the guide ball 345 is guided by guiding groove 352c to assist this rotation movement.

The anti-rotation means of the coupling arrangement further comprises a locking recess 352b on the locker body 352 and a locking member 342 extending through an aperture 342b onthe grip 330. Asthe locking protrusion352a is inserted into the locking aperture 341 and rotated, the locking member 342 engages the

locking recess 352b. The engagement between the locking member 342 and the locking recess 352b prevents counterclockwise rotation of the blade cartridge 350 with respect to the grip 330.

The anti-rotation means of the coupling arrangement is further provided with a first spring 343 and a releasing knob 344. The first spring 343 is embedded in the locking block 340 to elastically bias the locking member 342 outwardly.

The releasing knob 344 is provided along the aide of the locking block 340 and is linked to the locking member 342 by a pin 342a. When pushed, the releasing knob 344 slidingly moves along the outer surface of the locking block 340 and the grip 330 and against the action of the spring 343 to move the locking member 342 out of engagement with the locking recess 352 and into the locking block 340.

As can be seem from Fig. 17, a second spring 333 and a pusher 332 are housed partially in an internal passageway 331a of the locking block 340 and in a second passageway 331b of the grip 330. The pusher 332 is elastically biased by the second spring 333. Upon insertion of the locking protrusion 352a into the locking aperture 341, the locking protrusion 352a closely contacts the inner surface of the locking aperture 341. This contract prevents any swaying of the blade cartridge 350 due to the difference between the depth of the locking aperture 341 and the length of the neck of the locking protrusion 352a. Further, because the locking protrusion 352a is always biased by the pusher 332 in the releasing direction, the locking protrusion 352a is easily detachable from the locking aperture 341.

To use the cutter, the blade cartridge 350 is locked to the grip 330 through the locking block 340. When the first and second edge exposing portions 353c, 354c of the upper cover 353 and lower cover 354 are aligne, the cartridge is in the open position and a portion of the blade 351 is exposed. To place the cartridge in the closed position, the lower cover 354 is rotated clockwise via the protective cap 360, to the position shown in Fig. 14b. In the closed position, the blade 351 is protectively positioned inside the lower cover 354 and the second guide rib 354b. The interaction of the elastic strips 358a, 358b of the controlling boss 358 with the stopper 357a of the bolt 357 ensures that the cartridge remains in

the desired position.

To secure the blade cartridge 350 to the locking block 340 the locking protrusion 352a is inserted into the locking aperture 341 as shown in Fig. 18a.

While being inserted, the locking protrusion 352a acts on the pusher 332 against the action of the second spring 333. Once the protrusion 352a is inserted, the blade cartridge 350 is rotated 90° clockwise to the position shown in Fig. 10b.

The blade cartridge 350 can rotate no more than 90° because of the presence of the slanted steps 341a, 341b. At the same time, the locking member 342 is biased into engagement with the locking recess 352b, thereby preventing counterclockwise rotation of the blade cartridge 350. As a result, the blade cartridge 350 is firmly coupled to the grip and undesired rotation is avoided.

To release the blade cartridge 350 from the lockingblock 340. an user pushes down the releasing knob 344 against the bias of spring 343 to move the locking member 342 out of engagement with the locking recess 352b and into the locking block 340. Thereafter, the blade cartridge 350 can be rotated 90° counterclockwise and detached from the grip. As a result of the force of the spring 333, the pusher 332 pushes the protrusion 352a away from the grip once the cartridge is rotated.

The embodiment of the present invention depicted in figs. 9-11 includes a simplified version of the coupling arrangement. The coupling arrangement 250 is similar to that of the embodiment of Figs. 12-18 and includes a locking protrusion 252, a locking recess (not shown), a spring biased pusher 267,270, a spring biased locking member 257,259, and a releasing knob 263. Instead of a locking block, however, the embodiment of Figs. 9-11 is provided with a locking plate 254. Although the plate 254 includes apertures to accommodate the locking protrusion and the locking member, it does not house the spring biased pusher 267, 270 or the spring biased locking member 257,259. Instead, the grip 280 houses both the spring biased pusher 267, 270or the spring biased locking member 257, 259. Instead, the grip 280 houses both the spring biased pusher 267,270 and the spring biased locking member 257,259. This can be clearly seen in Fig. 11 As can be seen from Figs. 9a and 11, the locking plate 254 is attached to the grip 280

via a screw 277. It should be understood, however, alternate equivalent means could be used to attach the plate to the grip.

The coupl ing arrangement with the anti-rotation means of the rotary cutter of Figs. 9-18 avoids any undesired rotation of the blade cartridge due to the application of force from any direction. Accordingly, defective cutting caused by the undesired movement of the blade cartridge during use can be avoided. The blade can sti 11 be changed safely and quickly by detaching and changing the whole blade cartridge.

It should be understood that various changes and modifications to the preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be covered by the appended claims.