Cutting – Means to drive or to guide tool – With simple rectilinear reciprocating motion only
Reexamination Certificate
1999-12-17
2002-04-23
Ashley, Boyer (Department: 3724)
Cutting
Means to drive or to guide tool
With simple rectilinear reciprocating motion only
C083S628000, C083S691000
Reexamination Certificate
active
06374715
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for punching a sheet by cooperation of punches and dies.
DESCRIPTION OF PRIOR ART
When sheets such as copied papers are filed, they should be provided with holes through which they are filed. According to recent development of office machines, it is required that copied papers are automatically provided with holes for filing by punching machines mounted to the office machines, thereby eliminating troublesome manual work to punch copied papers.
Japanese Patent Laid-Open No. 3-228598 discloses an apparatus for punching a sheet to make filing holes, comprising (a) a cam assembly comprising a camshaft and a plurality of cams fixed to the cam shaft at predetermined intervals; (b) a punch assembly comprising an elongated support having a U-shaped cross section, a plurality of punches slidably supported by the U-shaped support, and springs each disposed around the punch between an inner surface of the U-shaped support and a stopper of the punch for biasing the punch inward the U-shaped support, and (c) a punch die having die holes each in alignment with each punch. This conventional sheet-punching apparatus comprises punches and cams in pairs, and therefore their numbers are the same.
When driving means such as cams and punches are used in the same number as in the above conventional punching apparatus, a large number of parts are necessary, requiring more time for assembling them. In addition, because a camshaft is subjected to a bending moment due to a reaction force at the time of punching, the camshaft should be thick in a large punching apparatus for papers of A
3
or more size. A thicker camshaft leads to larger cams, resulting in increase in parts cost. Also, larger cams lead to larger height of the entire sheet-punching apparatuses, making it difficult to make the punching apparatuses smaller.
Office machines equipped with such sheet-punching apparatuses are conventionally limited to those highly expensive. However, recent demand for equipping relatively inexpensive office machines with such sheet-punching apparatuses requires drastic reduction of prices of such sheet-punching apparatuses, whereby development is strongly needed to provide less expensive sheet-punching apparatuses.
OBJECT AND SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a high-performance, inexpensive apparatus for punching sheets such as copied papers.
In view of the above object, the inventors have found that using a combination of a driving system having a small number of cams and a tie bar having cam followers in slidable contact with the cams and connected to punches serves to reduce the number of driving parts such as cams, thereby making the assembling of a sheet-punching apparatus easier, and reducing a load applied to the driving system, which makes it possible to reduce the diameter of a camshaft of the driving system. With these features, it can be achieved to make a sheet-punching apparatus inexpensive. The present invention has been completed based on this finding.
Thus, the apparatus for punching a sheet according to the present invention comprises (a) a shaft extending transversely relative to the moving direction of the sheet; (b) a plurality of cams mounted to the shaft with a longitudinal interval for rotating together with the shaft; (c) a tie bar extending along the shaft and having a plurality of cam followers at positions corresponding to those of the cams; (d) a plurality of punches connected to the tie bar in longitudinal arrangement for being movable to and from punching positions; and (e) a die frame having a plurality of die holes in alignment with the punches for cooperating with the punches to make holes in the sheet.
The cams are preferably a pair of eccentric cams mounted to the tie bar in longitudinal end portions thereof. The eccentric cams may be arranged with a phase difference, whereby the tie bar moves toward and away from the punching positions with its longitudinal center axis inclined alternately, thereby providing the punches with different punching timing.
The tie bar is preferably constituted by a bent sheet having an increased cross section coefficient.
Each punch is preferably guided by a punch guide so that the punch can move substantially vertically though an inner wall of the punch guide even when the punch is subjected to inclining force by sliding contact of the cam followers with the eccentric cams.
Each punch preferably has a V-shaped, blade-forming notch diametrically extending on a tip end surface thereof, which is oriented along the moving direction of the sheet. Thus, a hole is made in a sheet without sudden drop of a shearing force to zero.
The apparatus for punching a sheet according to a preferred embodiment of the present invention comprises (a) a shaft extending transversely relative to the moving direction of the sheet; (b) a pair of cams mounted to the shaft in both longitudinal end portions for rotating together with the shaft; (c) a tie bar extending along the shaft and having a pair of cam followers at positions corresponding to those of the cams; (d) a plurality of punches connected to the tie bar in longitudinal arrangement for being movable to and from punching positions; (e) a frame extending along the tie bar, to which a plurality of punch guides are fixed in alignment with the punches; and (f) a die frame having a plurality of die holes in alignment with the punches for cooperating with the punches to make holes in the sheet.
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Flores-Sánchez Omar
Hitachi Metals Ltd.
Sughrue & Mion, PLLC
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