Prior manual punches have included a handle and a pressure plate to accomplish perforating paper sheets (U.S. Patent No. 2,382,523). Extended longitudinal handles have also been proposed for hand punches (U.S. Patent No. 5,143,502). Punching machines have also included toggle arrangements (U.S. Patent No. 806,262) .

Summary Of The Invention

Broadly, the present invention comprises a cam lever arrangement for applying force to the push flap of a manual punch. The flap pivotal about an axis on the punch is acted on through cam engagement by a cam lever means also pivotally mounted on the punch to increase the mechanical forces acting on the punches while allowing a reduction in the force required by the user. The punch includes a non-scuffing sliding chip scrap slipper.

It is a feature that the cam lever means may be pivotal about an axis parallel or perpendicular to a flap pivot axis.

It is a further feature that chip scraps from the hole punching operation may be removed from the punch assembly without the need for removing the slipper.

It is still a further feature that the punch assembly has a cam feature, integral to the push flap which allows operation of the punch pins by a rolling cam action rather than flat sliding surfaces thus eliminating the squeak associated with prior art.

Brief Description Of The Drawings

Fig. 1 is a front view of a prior art punch having its flap raised;

Fig. la is a cross sectional view of the prior art showing lever distances;

Fig. 2 is a back view of a slippered punch of the present invention with the flap raised and including a cam lever arrangement in its raised position;

Fig. 3 is the same view as Fig. 2 with the cam lever arrangement and flap lowered;

Fig. 4 is an end view of the punch with a portion shown in section and with the lever and flap raised;

Fig. 5 is the same view as Fig. 4 with the lever and flap lowered;

Fig. 6 shows an alternative embodiment having a raised lever arrangement mounted at the punch ends about axes perpendicular to the length of the punch;

Fig. 7 is the same view as Fig. 6 with the lever lowered;

Fig. 8 is an enlarged area of Fig. 7 with dimensions and angles therein;

Fig. 9 is an enlarged area of Fig. 6 with dimensions and angles therein;

Fig. 10 is the same view as Fig. 7 with the lever lowered and specific lengths shown;

Fig. 11 is a perspective view of the chip slipper showing the various elements;

Fig. 12 is a view of the punch base with the slipper shown partially extended.

Fig. 13 is a perspective view of an alternative slipper; and

Fig. 13a is a sectional view taken through Fig. 13.

Description Of The Preferred Embodiments

In Fig. 1 prior art punch 10 has rectangular base 11, vertical end walls 12a, 12b and pivotal flap 13 having indentation 13a. Also shown are three (3) pin units 14a, 14, 14c and flap protrusion 13p. Turning to Fig. la, the mechanical advantage of the prior rt unit 11 is shown by the following:

d ₃ = 1 . 5 INCH Typ .

d ₂ = 1 INCH Typ .

d _x = . 5 INCH Typ .

- ₃ _ 1 . 5 = 3 : 1 RATIO . 5

Turning to Figs. 2-5, inventive paper sheet punch 20 has base 21, vertical end walls 22a, 22b, pivotal elongated flap 23 pivotal about flap axis 24, punch pin cams 41a, 41b, 41c, sliding slipper 29 and flap cam surface 32. Lever 26 includes hand-contact portion 28, neck portion 31, curved cam surface 34

(Fig. 2) makes a sliding line contact with flap cam surface 32 of flap 23 as lever 26 is operated to move pivotal elongated flap 23 (see Figs. 4 and 5) . Lever 26 is shaped and positioned for rotation so it fits within the area of rectangular base 21 as viewed from above. Lever 26 adds to the height of the punch but not its width or length. Also shown are punch unit racks 36, 37 with horizontal slots 36s, 37s and 40s for longitudinally adjustable pin units 39a, 39b, 39c which carry punch pins 39p.

With reference to Figs. 3 and 10 and lever arm distances:

MECHANICAL ADVANTAGE LEVER DESIGN

= 3.78:1 RATIO

2.33:1 RATIO

ADVANTAGE 2.33 X 3 . 1 8 = 8.807

As curved cam surface 34 of lever 26 operates on flat cam surface 32 of flap 23 remote from axis 24 the mechanical advantage is based on the following equations (Figs. 8 and 9) :

EQUATION SET 1

<BAE = COS AB ² +AE ² -BE ² 2 -AB-AE

where

<FAE = ϋ/ ^"1 A

θ = <BAE-<FAE

α = <BAE-<FAE-<OAF

AC = AB-cosθ

D£ = AF-AC = ^-ABcosθ

££> = <JBE ² -DE ² = jR ² -DE ²

b = y ₁ ^• cosβ

EQUATION SET 2 First Stage:

(t _r δ)pcosβ=(i _i +Z ₂ )F _i

(£ι-° ^" ) ^F _\ ⁼ X „ c sβ -P=G.'P

where P is Punch Force

^G ' ⁼ ^

l _ϊ ,l ₂ ,δ,β are geometric realted factor (see page 2)

Second Stage:

£ ₃ F ₂ =(£ ₃ +£ ₄ )F input

p ₂ = F input = i. f input

where F input is input force

* ₃ i *-

v Fι=F ₂ , Combined (1) and (2) , ϊe obtain

F input = G,«G.

During operation integral cam surfaces 41a, 41b, 41c of flap 23 being a radius surface rather than a flat angled surface operate upon surface 42a, 42b, 42c

of pin units 39a, 39b, 39c in a rolling action rather than a sliding action. The result being a punch in which the squeak common to current designs is eliminated.

Turning to Figs. 6 and 7 and an alternative embodiment, punch 60 has base 61, end frame pieces 62, 63, flap 64, flap pivot 66, lever 67 and lever pivot 68. Flap 64 includes cam 64g adjacent to pivot 66 and remote cam 64b. Lever 67 includes cam 69 and remote surface 67g.

Fig. 7 showing lever arm distances:

= 3 . 158 : 1 RATIO

3 . 9 : 1 RATIO

3 . 158 x 3 .9 = 12 . 316

Turning to Figs. 8 and 9 construction and operation of the slipper 29 are shown including channel area 80, closed end 81, angled sides 82, 83, notched end 84 and slots 85, 86 and bottom surface 87, Slipper 29 is made of rubber, plastic or other

material that will not scratch or mar a finished wooden desk or similar surface.

Slipper 29 may be extended to a position so the paper chips can be poured free from the slipper holding channel 80. Movement of the slipper 29 from the captive position shown in Figs. 2 and 3 to the pouring position is accomplished by sliding the slipper 29 in a direction opposite from end 84. Slipper 29's retention on base 21 is accomplished forming angled sides 82, 83 of slipper 29 to complement the angled sides 88, 89 of base 21.

Turning to Figs. 13 and 13a and the alternative embodiment of slipper 100 which includes channels 101 and 102, cavity 103, closes ends 104, 105, angled sides 106, 107, inner angled surfaces 108, 109, and bottom surface 110. Channels 101, 102 may terminate at closed end 104 or closed end 104 may be slotted like end 105 to all channels 101, 102 to continue to the outer surface of end 104.