Variable pitch punch apparatus
A variable pitch punch apparatus ( 1 ) for punching holes in material. The apparatus comprises a rotary punch head ( 2 ) comprising at least one punch member ( 4 a - c ) to punch at least one hole in a material at least one desired location. The apparatus ( 1 ) further comprises a die head ( 6 ) comprising at least one die ( 7 ) corresponding to said punch member ( 4 a - c ). The apparatus ( 1 ) further comprises an actuator for providing a selective relative speed difference between the material and the rotary punch head ( 2 ).
1. A variable pitch punch apparatus for punching holes in material, the apparatus comprising:
a rotary punch head comprising a punch shaft having a center of rotation, and having a plurality of spaced apart punch members to punch respective holes in a material at respective desired locations, the punch shaft also having a plurality of peripheral portions extending between adjacent punch members, the peripheral portions having respective radii measured relative to the center of rotation of the punch shaft, wherein the radii vary along the length of the peripheral portions such that the respective radii of the peripheral portions decrease with distance from a nearest punch member to a minimum value located between the adjacent punch members;
a rotary die head adjacent the rotary punch head, and comprising a plurality of dies corresponding to respective punch members of the rotary punch head; and
an actuator for rotating the rotary punch head in a first direction at a first predetermined speed, and for rotating the rotary die head in a second direction opposite to the first, such that respective punch members are aligned with respective dies, the peripheral portions of the punch head configured to allow a selective relative speed difference between the rotary punch head and material located between the rotary punch head and rotary die.
2. The punch apparatus as claimed in claim 1 , in which the minimum radii of each of the peripheral portions is located centrally between respective adjacent punch members.
3. The punch apparatus as claimed in claim 1 , wherein the punch shaft has a substantially elliptical cross-section.
4. The punch apparatus as claimed in claim 1 , wherein at least one of the plurality of peripheral portions of the punch shaft comprises a coating of at least one low friction material.
5. The punch apparatus as claimed in claim 1 , wherein at least one of the plurality of the peripheral portions of the punch shaft comprises at least one rotating bearing element arranged to contact the material.
6. The punch apparatus as claimed in claim 1 , wherein at least part of at least one of the plurality of peripheral portions of the punch shaft is arranged such that it does not contact the material during use.
7. The punch apparatus as claimed in claim 6 , wherein substantially all of the plurality of peripheral portions of the punch shaft are arranged such that they do not contact the material during use.