Patent Publication Number: US-RE38354-E

Title: Circle cutter

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a circle cutter, particularly to an instrument adapted for cutting circles on objects. It includes a rotary disc assembly and a cutting tool. The rotary disc assembly is made up of an outer ring board, a rotary disc, a fixing ring cap and a plurality of beads. The rotary disc mounted to the outer ring board is movably limited in place by the fixing ring cap and are rotatably supported by the multiple beads received in a tunnel defined between the outer ring board and the rotary disc. On the rotary disc are disposed a plurality of holes marked with a numeral that is the diameter of a circle to be cut. The cutting tool has a hollow pen stick and a cutting knife attached to a knife clip that is movably engaged with a holding head. The holding head is further secured to the bottom end of the hollow pen stick and is free to rotate with respect to the pen stick so that the cutting knife can be smoothly guided in a cutting operation. 
     The circle cutter of the present invention is placed on top of an object in use, and a cutting tool is selectively engaged with a hole on the rotary disc which is made to rotate by the cutting tool so that a circle area can be cut on the object by a cutting knife mounted to the cutting tool. 
     In general, to cut circles on various kinds of paper, thin cardboard and soft thin wood board, circles of proper sizes are first drawn on them by a compass and then a pointed knife is used to cut along a drawn line a circle. Such a conventional way of cutting circle is tedious and time consuming in one aspect, and so obtained circles are not smooth and precise enough in another aspect. Besides, accidental cutting can often result in damage to the used material. 
     SUMMARY OF THE INVENTION 
     Therefore, the primary object of the present invention is to provide a circle cutting tool or a circle cutter which is operated in a more direct and faster manner to cut circles of various diameters in a smooth and ready manner. 
     Another object of the present invention is provide a circle cutting tool or a circle cutter equipped with a cutting knife which is operated in such a smooth manner that circles can be cut on material without causing damage to the material. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective diagram showing the exploded components of the circle cutter of the present invention; 
     FIG. 2 is a perspective diagram showing the exploded components of a cutting tool of the present invention; 
     FIG. 3 is a perspective diagram showing the assembly of the circle cutter of the present invention; 
     FIG. 4 is a sectional view of the present invention; 
     FIG. 4A is a partial sectional view of the cutting tool, showing the knife thereof, 
     FIG. 5 is an elevation view of the circle cutter of the present invention in operation; 
     FIG. 5A is a top view of the cutting tool of the present invention; 
     FIG. 5B is a bottom view of the cutting tool of the present invention; 
     FIG. 6 is a perspective diagram showing the second embodiment of the knife of the cutting tool of the present invention; 
     FIG. 7 is a diagram showing the sectional view of the cutting tool of the present invention; 
     FIG. 7A is a diagram showing a partial side elevation view of the second embodiment knife of the cutting tool. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1,  2  of the present invention, the circle cutter of the present invention comprises a rotary disc assembly  10  and a cutting tool  20 . The rotary disc assembly  10  is made up of an outer ring board  11 , a rotary disc  12 , fixing ring cap  13  and a plurality of beads  14 . 
     On the peripheral area of the outer ring board  11  are disposed a plurality of consecutive circular holes  111  of various diameters gradually reduced one by one for drawing circles. On the inner flange  112  of the outer ring board  11  is disposed a bead retaining groove  1121  having a semi-circular cross section. A raised peripheral rim  113  is located next to the groove  1121  and a plurality of spaced retaining lugs  114  extending radially from the rim  113 . Each lug  114  is provided with an insertion hole  1141 . 
     The diameter of the rotary disc  112  is slightly smaller than the inner diameter of the raised peripheral rim  113  of the outer ring board  11 . At the periphery of the rotary disc  12  is disposed a downwardly turned engagement flange  121  having a groove  1211  having a semi-circular cross section in conformance to the bead retaining groove  1121  of the outer ring board 11 . The roof  1212  of the engagement flange  121  has a smooth contour of a semi-circular cross section. 
     A plurality of insertion holes  122  are spirally located on the rotary disc  12  with their distances to the center of the disc  12  increasingly varied. The diameter  123  of a circle to be drawn can be marked beside each insertion hole  122 . On the outer periphery of the fixing ring cap  13  are disposed a plurality of spaced radially extended locking lugs  131  each having an engagement pin  1311 . 
     The cutting tool  20  has a hollow pen stick  21 , a top cap  22 , a knife clip  23 , a holding head  24  and a cutting knife  25 . In the hollow interior of the pen stick  21  spare cutting knives  25  are housed. At the top end of the pen stick  21  are disposed internal threads  211  and at the opposite end thereof is disposed a round ended push head  212  provided with external threads  2121  at its enlarged section. The top cap  22  having a T-shaped cross section has external threads  221  at the bottom end thereof. The knife clip  23  is a two-staged cylinder having a dome-shaped top and a reverse T-shaped retaining recess  231  for the holding of the cutting knife  25 . 
     The holding head  24  has a cylindrical top section and a conic lower section having a 3-staged hole  241 . The hole  241  is provided with internal threads  2411  at the largest hole section. The cutting knife  25  is made in an arrow shape and has a V-shaped cutting edge  251 . 
     Referring to FIGS. 3,  4 , in the assembly of the rotary disc assembly  10 , the beads  14  are first placed in the bead retaining groove  1121  of the inner flange  112  of the outer ring board  11 . And the rotary disc  12  is registered with the central void  110  of the outer ring board  11 . At the same time, the engagement flange  121  of the rotary disc  12  is registered with the inner flange  112  of the outer ring board  11 . The bottom surface of the rotary disc  12  is positioned a little higher than that the outer ring board  11  when engaged so that the rotary  12  is not in contact with the surface of a table or a working plane, as shown in FIG.  4 . 
     In such a circumstance, the beads  14  are confined in a tunnel defined by the groove  1121  of the inner flange  112  of the outer ring board  11  and the groove  1211  of the engagement flange  121  of the rotary disc  12 . Afterwards, the fixing ring cap  13  is engaged with the raised peripheral rim  113  of the outer ring board  11  by registering the engagement pins  1311  of the locking lugs  131  of the ring cap  13  with the insertion holes  1141  of the lugs  14  disposed on the peripheral rim  113  of the outer ring board  11 . Then the fixing ring cap  13  is permanently fixed in place by ultrasonic welding so as to rotatably restrain the rounded roof  1212  of the engagement flange  121  of the rotary disc  12 , preventing the rotary disc  12  from detachment to complete the assembly. 
     The cutting tool  20  is assembled by inserting the knife clip  23  into the hole  241  of the holding head  24  from the top thereof with the large cylinder section of the knife clip  23  housed in the middle section of the 3-staged hole  241  of the holding head  24 . The small section of the knife clip  23  is in registration with the smallest section of the 3-staged hole  241  of the holding head  24  with part of the small section of the knife clip  23  protruded outside. 
     Then the holding head  24  is engaged with the hollow bottom end of the pen stick  21  by way of the inner threads  2411  of the 3-staged hole  241  of the holding head  24  and the external threads  2121  of the push end  212 . So, with the round ended push head  212  can be in abutment against the dome-shaped top end of the knife clip  23 , the knife clip  23  can be freely rotated in the holding head  24 . The cutting knife  25  is forced into engagement with the reverse T-shaped retaining recess  231  with the V-shaped cutting edge  251  of the cutting knife  25  exposedly projected out of the bottom end of the retaining recess  231 . Afterwards, the top cap  22  is secured to the top end of the hollow pen stick  21  by way of the external threads  221  of the cap  22  and the internal threads  211  of the pen stick  21 . 
     As further shown in FIG. 5, the operation mode of the present invention is illustrated. The rotary disc assembly  10  is first placed in contact with a flat object to be cut, and a proper insertion hole  122  having a numeral  123  marked nearby on the rotary disc  12  is selected. Then the V-shaped cutting edge  251  of the cutting knife  25  as well as the smaller section of the knife clip  23  of the cutting tool  20  is engaged with the insertion hole  122 . Thereby the pointed V-shaped cutting edge  251  can pierce into the object to be cut and with the knife clip  23  freely movable in the holding head  24 , the pen stick  21  of the cutting tool  20  is held and driven to make the rotary disc  12  move in circle. It results in the cutting of a round circle on the object by the V-shaped cutting edge  251  of the cutting knife  25 . 
     Referring to FIG. 6, the second embodiment of the cutting knife  25  having a right triangular shaped cutting edge  251 ′ which can be more smoothly moved along a circular trajectory of cutting in synchronism with the knife clip  23  when the hollow pen stick  21  of the cutting tool  20  is forced to move circularly. 
     It can be clearly seen that the present invention has the following advantages in practical use. The operation of the circle cutter of the present invention becomes easier, and faster and the peripheral rim of a cut circular object is smooth and in good shape without causing any damage to a material used.