Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2002-05-01
2004-03-30
Walsh, Donald P. (Department: 3653)
Sheet feeding or delivering
Feeding
Separators
C271S137000, C271S167000
Reexamination Certificate
active
06712351
ABSTRACT:
This application incorporates by reference Taiwan application Serial No. 090110666, filed May 3, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a sheet feeding apparatus, and in particular, to a sheet feeding apparatus using an elastic device.
2. Description of the Related Art
The performance of the conventional image forming apparatus, such as a printer, copy machine, facsimile machine, or the like, is greatly affected by the quality of sheet feeding. A sheet feeding apparatus capable of separating and feeding sheets one-by-one smoothly and continuously is therefore in great demand.
Taking the printer as an example of the image forming apparatus, a conventional sheet feeding apparatus is illustrated in FIG.
1
A. The printer is typically equipped with an automatic sheet feeding apparatus, wherein sheets of papers are first positioned at a rest plate and driven one-by-one by the sheet feeding apparatus to the image forming apparatus. In
FIG. 1A
, a base
101
for supporting the sheets is at the bottom of the automatic sheet feeding apparatus. A roller
150
is installed above the base
101
to drive the sheets forward. The base
101
has a sheet-separating pad
103
, for separating sheets one-by-one, and a number of smooth ribs
102
.
The front view shown in
FIG. 1B
illustrates the movement of the sheets. The sheet separating pad
103
and the smooth ribs
102
are located on the base
101
of the automatic sheet feeding apparatus and are parallel to each other. The ribs
102
act to elevate the sheets in order to facilitate the smooth movement of the individual sheets. Materials with low friction coefficient are ideal for the manufacture of the ribs
102
; thus a smooth rubber or plastic is frequently used because of the additional advantage of low cost. The side view shown in
FIG. 1C
illustrates the movement of the sheets. The sheet
105
is driven by the roller
150
(not shown), and is moved along the direction A. The front edge
107
of the sheet
105
touches the surfaces of the ribs
102
and slides along the direction A.
Then referring to
FIG. 1D
, the friction force to the sheet is illustrated. While the sheet
105
is forwarded along the direction A, the ribs
102
generate a friction force against the movement of the sheet
105
. If the thickness of the sheet
105
reaches to a certain level, the friction force will not have much influence on the movement of the sheet. However, if the sheet
105
is thin, the lower edge
107
can bend around, instead of moving forward smoothly, as shown in FIG.
1
E.
In
FIG. 1E
, the lower edge
107
of sheet
105
is in contact with the ribs
102
. The roller (not shown) drives the sheet
105
forward along the direction A, but the friction force pushes the sheet backward along the direction B. As the roller continues to drive the sheet
105
, the sheet
105
can potentially roll up and cause a paper jam.
In addition to the ribs
102
, the sheet-separating pad
103
is also a key element of the conventional base
101
.
FIG. 2
shows the side view of the sheet-separating pad
103
and the sheets
105
. The sheet-separating pad
103
is shaped similarly to a saw in that it has a number of sawtooth-like protrusions
106
. Each protrusion
106
rises up at an angle &agr;. The friction force generated by the sheet-separating pad
103
against the sheets is large enough to separate each sheet. The sheet-separating pad
103
is typically positioned along the sheet moving direction A. Thus, as the sheet
105
moves and rises along the sawtooth-like protrusions
106
, it is separated from the other sheets. The movement of the sheet
105
depends on the angle &agr; and the friction coefficient, which is affected by the material and thickness of the sheet
105
.
The type of printing sheet can vary greatly, with the material and thickness being just two factors. The thickness, usually defined by g/m
2
, can vary within a wide range, for example, from thick postcards, envelopes, and plastic plates to thin plain papers. The conventional sheet-separating pad is designed to satisfy a certain range of printing materials. The incline angle &agr; and the material type (which affects the coefficient of friction) of the sheet separating pad
103
are determined factors, thus only printing materials within the designated range are suitable. Printing materials outside the designated range may cause paper jams or reduce the sheet feeding accuracy. Furthermore, the high precision requirement in the manufacturing of the sheet-separating pad causes difficulties in fabrication and results in higher cost. To summarize, the disadvantages of the conventional sheet feeding apparatus comprise the following:
1. paper jams;
2. limited printing materials;
3. less accuracy in sheet separation; and
4. higher cost in fabrication of the sheet-separating pad.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a sheet feeding apparatus that enhances the stability of sheet separation and reduces the potential for paper jams.
According to the object of the invention, a sheet-separating pad for use in a sheet feeding apparatus is disclosed. The sheet-separating pad comprises a pad base having a top surface and a groove. Numerous inclined protrusions are formed at one or two sides of the groove on the top surface of the base to guide the sheet(s) in a certain direction. An elastic device, such as a spiral spring or a series of connected spring leaves, is situated in the groove. The spiral spring or series of spring leaves protrudes above the top surface of the base in order to separate the sheets. Driven by rollers, the sheets rise gradually along the protrusions so that the sheets can be separated one-by-one. Moreover, the radial arrangement of the ribs and the sheet-separating pad allows the lower edge of each sheet to move forward smoothly such that a paper jam can be prevented.
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Benq Corporation
Bower Kenneth W
Rabin & Berdo P.C.
Walsh Donald P.
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