Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
1999-04-05
2001-10-09
Walsh, Donald P. (Department: 3653)
Sheet feeding or delivering
Feeding
Separators
C271S003080, C271S003090, C271S008100, C271S145000, C271S147000, C271S148000
Reexamination Certificate
active
06299156
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a sheet supply system, and more particularly to a sheet supply system which feeds out sheets stacked on a sheet support table one by one from the sheet support table.
2. Description of the Related Art
For example, in a stencil printer, a number of printing papers are supplied to a printing system one by one without lost feed (referring to malfunction that no printing paper is supplied) or multiple feed (referring to malfunction that a plurality of printing paper are supplied at one time).
In the stencil printer, a number of copies are often printed from one original, and accordingly a number of printing papers are stacked on a paper support table. In such a case, it is preferred that the uppermost printing paper in the stack on the support table be constantly positioned at a predetermined level (will be referred to as “the paper feed-out level”, hereinbelow) so that a paper feed-out system can act on the uppermost printing paper constantly in an optimal manner. For this purpose, the paper support table is moved upward as the level of the uppermost printing paper in the stack remaining on the paper support table lowers.
FIG. 8
shows an example of a conventional paper supply system for a stencil printer. In
FIG. 8
, reference numeral
51
denotes a paper support table on which a stack of printing papers P is supported. The paper support table
51
is moved up and down by a table drive means (not shown). The printing papers P are fed out from the paper support table
51
one by one by a paper feed-out unit
53
. The paper feed-out unit
53
comprises a pair of paper feed rollers (a scraper roller
54
a
and a pick-up roller
54
b
) which are mounted for rotation on one bracket and are rotated in synchronization with each other. The paper feed-out unit
53
is rotatable about a shaft
53
a
and is moved upward when the paper support table
51
is moved upward and the uppermost printing paper in the stack of the printing papers P pushes upward the scraper roller
54
a
. The shaft
53
a
is urged by a spring means (not shown) so that the contact pressure between the scraper roller
54
a
and the uppermost printing paper increases as the paper feed-out unit
53
is lifted higher.
A limit switch
52
, which may be, for instance, a microswitch or a photo-interrupter, is disposed to be opened when the paper feed-out unit
53
is moved upward to a predetermined level. That is, when paper support table
51
is moved upward to push the paper feed-out unit
53
upward and the limit switch
52
is opened, the table drive means is de-energized and the paper support table
51
is stopped at the level. When the printing papers P on the support table
51
are fed out from the paper support table
51
and the level of the uppermost printing paper lowers, the limit switch
52
is closed again and the table drive means is energized to move upward the paper support table
51
. In this manner, the uppermost printing paper is constantly kept at the level at which the limit switch
52
is opened, thereby keeping constant the contact pressure between the uppermost printing paper and the scraper roller
54
a
during paper supply operation of the paper supply system. The level of the uppermost printing paper at which the limit switch
52
is opened is the aforesaid “paper feed-out level”.
However the conventional system is disadvantageous in that since the paper feed-out level is controlled by opening and closure of the limit switch
52
, the accuracy in positioning the uppermost printing paper at the paper feed-out level is governed by the sensitivity of the limit switch
52
, which fluctuates from switch to switch and changes with time. When the paper feed-out level fluctuates, the contact pressure between the uppermost printing paper and the scraper roller
54
a
fluctuates, which causes the aforesaid lost feed or the aforesaid multiple feed. Further, it takes a movement of the paper support table
51
through a certain distance to open and close the limit switch
52
. The distance is generally larger than the thickness of one printing paper and is generally equal to triple of the thickness of the printing paper. Accordingly, the level of the uppermost printing paper is adjusted only once per three printing papers, which results in fluctuation in the contact pressure during supply of the three printing papers.
There are used various types of printing papers which are different in thickness, quality and the like. The contact pressure optimal to feed the printing papers one by one differs according to the thickness, quality and the like of the printing paper. Thus there has been proposed, as disclosed in Japanese Unexamined Patent Publication No. 8(1996)-259099, a paper supply system in which the contact pressure between the uppermost printing paper and the scraper roller (i.e., the paper feed-out level) can be changed. In the paper supply system, the position of the limit switch
52
relative to the paper feed-out unit
53
is changed in two steps by operation of a lever so that the contact pressure between the uppermost printing paper and the scraper roller
54
a
at the level of the uppermost printing paper at which the limit switch
52
is opened is changed in two steps. When thick printing papers are to be supplied, the contact pressure is increased and when thin printing papers are to be supplied, the contact pressure is reduced.
Also this system cannot be free from the aforesaid drawbacks inherent to the limit switch and since the paper feed-out level is changed by changing the position of the limit switch relative to the paper feed-out unit, an additional mechanism is required, which adds to the manufacturing cost of the system.
Further printing papers of different thicknesses can be sometimes stacked on the paper support table, and accordingly there is a demand for a paper supply system which can automatically change the paper feed-out level according to the thickness of the printing paper.
SUMMARY OF THE INVENTION
In view of the foregoing observations and description, the primary object of the present invention is to provide a sheet supply system in which the sheet feed-out level can be accurately controlled and at the same time, the sheet feed-out level can be arbitrarily set without adding to the manufacturing cost of the system.
Another object of the present invention is to provide a sheet supply system in which the sheet feed-out level is automatically corrected according to the actual thickness of the printing papers.
In accordance with the present invention, there is provided a sheet supply system comprising
a sheet support table which is movable up and down and on which a stack of a plurality of sheets are supported,
a sheet feed-out means which feeds out the sheets on the sheet support table one by one from the uppermost one,
a table drive means which moves the sheet support table up and down relative to the sheet feed-out means,
a level sensor which detects the level of the uppermost sheet on the sheet support table,
a sheet feed-out level setting means for initially setting a sheet feed-out level at which the uppermost sheet is kept during sheet supply operation of the system, and
a control means which actuates the table drive means to move upward the sheet support table when the level of the uppermost sheet on the sheet support table as detected by the level sensor lowers from the sheet feed-out level as set by the sheet feed-out level setting means by a predetermined value and stops the table drive means when the level of the uppermost sheet on the sheet support table as detected by the level sensor reaches the sheet feed-out level.
In the sheet supply system with this arrangement, since the level sensor continuously detects the level of the uppermost sheet in the stack on the sheet support table and the table drive means is stopped when the level of the uppermost sheet on the sheet support table as detected by the level sensor reaches the sheet feed-out level, the sheet feed-out level can be controll
Inoue Hideaki
Kaneda Hiroshi
Suzuki Masao
Beauchaine Mark J.
Nixon & Peabody LLP
Riso Kagaku Corporation
Studebaker Donald R.
Walsh Donald P.
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