Abstract:
A method of forming a base ( 118 ) for a paper punch ( 154 ) is disclosed as including the steps of (a) providing a cast iron core ( 102 ) with a wall ( 104 ) and a plate ( 106 ) with a hole ( 108 ); (b) providing two generally U-shaped cast iron plates ( 110 ); (c) positioning the plates ( 110 ) spaced apart from and on opposite sides of the core ( 102 ); and (d) insert-molding the core ( 102 ) and plates ( 106 ) with a plastics material, e.g. ABS.

Description:
This invention relates to a base for a paper punch and a method of forming such a base and, in particular, such a base for a paper punch suitable for paper crafting purposes. 
     BACKGROUND OF INVENTION 
     In the field of paper crafting, pieces of paper or cardboard of various shapes are punched out from sheets of paper or cardboard by paper punches. A conventional paper punch is shown in  FIGS. 1 and 2  and generally designated as  10 . The paper punch  10  has a operating handle  12  operatively associated with a main body  14 . A generally horizontal slot  16  is provided in the main body  14 , for insertion of a sheet of paper or cardboard  18 . The operating handle  12  may then be pivoted downwardly to move a punch die (see  FIG. 4 ) to punch or cut out a piece of shaped paper or cardboard  18   a  from the piece of paper or cardboard  18 , as shown in  FIG. 3 . 
     As shown in  FIG. 4 , the operating handle  12  is pivotable about a point  20  to bear down on a metal punch die  22  to move vertically downward to pass through a slot  24  between an upper jaw  26  and a lower jaw  28  of a metal base  30  to perform the cutting action. Upon release of the downward force, a spring  32  provided between the punch die  22  and the base  30  acts to return the punch die  22  to the upper stable position as shown in  FIG. 4 . 
     In a conventional paper punch, the die and the die holder (also called a “base”) are made of metal or metal alloy (such as copper, aluminium, silver, zinc or tin) by low pressure die cast, e.g. by injection molding. Although it has been known that the cost of the product may be reduced if at least part of the die or base is made of a plastics material, it has long, been held by people in the field that such may jeopardize proper alignment between the die and the base, in particular during the course of relative movement between the die and the base in the punching action. It is also believed that the strength and rigidity of the base may be compromised if part of it is made of other materials, e.g. a plastics material. 
     It is thus an object of the present invention to provide a base for a paper punch, a paper punch with such a base, and a method of forming such a base in which at least part of the base is made of a plastics material, while minimizing the aforesaid envisaged shortcomings, or at least to provide a useful alternative to the trade and public. 
     SUMMARY OF THE INVENTION 
     According to a first embodiment of the present invention, there is provided a method of forming a base for a paper punch, including the steps of (a) providing a core part with a wall member and a plate with at least one hole; (b) providing at least two generally U-shaped plate members; and (c) insert-moulding at least said core part with a plastics material. 
     According to a second embodiment of the present invention, there is provided a base for a paper punch, including a body part fixedly engaged with a core part with a wall member and a plate with at least one hole, and two generally U-shaped plate members spaced apart from and on opposite sides of said core part; wherein said core part and plate members are made of a material different from that with which said body part is made. 
     According to a third embodiment of the present invention, there is provided a paper punch including a die and a base, said base being formed by a method including the steps of (a) providing a core part with a wall member and a plate with at least one hole; (b) providing at least two generally U-shaped plate members, and (c) insert-moulding at least said core part with a plastics material. 
     According to a fourth embodiment of the present invention, there is provided a paper punch including a die and a base, said base including a body part fixedly engaged with a core part with a wall member and a plate with at least one hole; and two generally U-shaped plate members spaced apart from and on opposite sides of said core part; wherein said core part and plate members are made of a material different from that with which said body part is made. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a side view of a conventional paper punch; 
         FIG. 2  is a top perspective of the paper punch shown in  FIG. 1 ; 
         FIG. 3  shows a shaped piece of paper cut out by the paper punch shown in  FIG. 2 ; 
         FIG. 4  is a sectional view of the paper punch shown in  FIG. 1 ; 
         FIG. 5  is an exploded view of the metal punch die and metal base of the paper punch shown in  FIG. 1 ; 
         FIG. 6  shows a core part and two side plates of a base according to a preferred embodiment of the present invention; 
         FIG. 7  shows schematically the positioning of the core part and side plates shown in  FIG. 6  for insert-moulding by a plastics material; 
         FIG. 8  is a top perspective view of the base just after insert-moulded; 
         FIG. 9  is a transverse sectional view of the base shown in  FIG. 8 ; 
         FIG. 10  is an enlarged perspective view of the encircled part in  FIG. 9 ; 
         FIGS. 11 to 12  show cutting of the base shown in  FIG. 8  to form a slot; 
         FIG. 13  is a perspective view of the base after cutting; 
         FIG. 14  is a further perspective view of the base after cutting; 
         FIG. 15  is a transverse sectional view of the base shown in  FIG. 14 ; 
         FIG. 16  is an enlarged perspective view of the encircled part in  FIG. 15 ; 
         FIG. 17  is a sectional view of a paper punch incorporating the base shown in  FIG. 14 ; and 
         FIG. 18  is an exploded perspective view of a punch die and the base shown in  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     According to a first method for forming a base according to the present invention and as shown in  FIG. 6 , there is firstly formed a cast iron core  102  with a cylindrical wall  104  and a plate  106  in which a shaped through hole  108  is formed. The plate  106  is perpendicular to the wall  104 . The shaped  108  is sized and shaped to receive the cutting edge of a corresponding punch die (not shown). The core  102  may be formed of other metals, metal alloys, or some other suitably strong materials. 
     Two generally U-shaped cast iron plates  110  are also provided. Each U-shaped plate  110  has two arms  112   a ,  112   b  which are spaced apart from each other by a gap  114 . The U-shaped plates  110  may be formed of other metals, metal alloys, or some other suitably strong materials. 
     As shown in  FIG. 7 , the core  102  and U-shaped plates  110  are positioned within a mould pair  116  formed of an upper mould  116   a  and a lower mould  116   b . The plates  110  are on opposite sides of and spaced apart from the core  102 . A plastics materials, e.g. acrylonitrile-butadiene-styrene terpolymer (ABS), may be injected into the mould in the direction of the arrow A in  FIG. 7  to insert-mould the core  102  and U-shaped plates  110 . 
     A base  118  formed of such a method is shown in  FIGS. 8 to 10 , in which the U-shaped plates  110 , shown in phantom lines, are fully embedded within a body  120 . The core  102  is also fixedly engaged with the body  120 . It should be understood that although the plates  110  are shown here as fully embedded within the body  120  of the base  118 , it is envisaged that the plates  110  may be fixedly secured to the body  120 , yet with one of its major surfaces exposed to the outside environment. 
     As shown in  FIGS. 11 to 13 , in order to allow the base  118  to function, the wall  104  of the core  102  is cut by a circular cutter  122  to form a slot  124  (see  FIGS. 14 to 16 ) which forms, with the gaps  114  of the U-shaped plates  110 , a common opening  126  allowing insertion of a piece of paper or cardboard for cutting purposes. 
     A paper punch incorporating the base  118  formed according to the method discussed above is shown in  FIG. 17  and generally designated as  150 . The paper punch  150  has an operating handle  152  which is pivotable to bear on a punch die  154  to cause the punch die  154  to pass through the common opening  126  formed of the slot  124  and the gaps  114  of the U-shaped plates  110  of the base  118 . 
     It is clear from the foregoing discussion that as part of the base  118  is formed of a plastics material, the cost of production is reduced, without compromising the strength and integrity of the base  118 . The U-shaped plates  110  provide support and strength to the base  118 , and prevent deformation of the base  118 , in particular during the punching action. 
     According to an alternative method, the core  102  and the U-shaped plates  110  are formed integrally with each other of the same material (e.g. cast iron) simultaneously. They are thus fixedly engaged with each other when formed. The core  102  and the U-shaped plates  110  are then placed within the mould pair  116  for carrying out the insert-moulding process to form the base  118 . 
     According to a further alternative method, only the core  102  is placed within the mould pair  116  for insert-moulding. After moulding, the two U-shaped plates  110  are at least partly received with a respective recess on a respective side of the base  118  and fixedly engaged therewith by interference fit (also called “press fit”). 
     It should be understood that the above only illustrates examples whereby the present invention may be carried out, and that various modifications and/or alterations may be made thereto without departing from the spirit of the invention. 
     It should also be understood that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided or separately or in any suitable sub-combination.