Electricity: conductors and insulators – Conduits – cables or conductors – Insulated
Reexamination Certificate
2002-01-14
2003-04-22
Nguyen, Chau N. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Insulated
Reexamination Certificate
active
06552272
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an anti-abrasive flat flexible cable (FFC), and more particularly to an anti-abrasive flat flexible cable adapted to be used with a thin image scanner.
BACKGROUND OF THE INVENTION
A flat flexible cable is a common connecting wire between electric devices. It is advantageous to be easily and reversibly bent and stretched in a narrow and crowded space. For example, in a flatbed image scanner, the moving-around carriage containing therein optical and photoelectric devices is connected with the circuit board through a flat flexible cable. Please refer to
FIGS. 1A and 1B
which are a top and a cross-sectional side views, respectively, schematically showing the connecting operation of a flat flexible cable in a flatbed image scanner. The flatbed scanner includes an upper cover (not shown) and a lower housing
10
. In the lower housing, a carriage
11
containing therein optical and photoelectric devices, a driving device
12
consisting of a motor and gear set
121
and a rail set
122
, a circuit board
13
including various electronic elements, and a flat flexible cable
14
connecting the carriage
11
with the circuit board
13
are sealed under a transparent scanning platform
15
. The carriage
11
is moved by the motor and gear set
121
along the rail set
122
to pass by and scan a document or picture placed on the transparent platform
15
so as to realize the image data of the document or picture.
Please refer to
FIG. 2
which is a schematic cross-sectional diagram showing the structure of a conventional flat flexible cable. The flat flexible cable
14
includes a flexible copper foil
141
, an insulating wrapper
142
made of a flexible plastic, and a strengthening plate
143
made of a rigid plastic. The insulating wrapper
142
surrounds the copper foil
141
with two ends of the copper foil
141
exposed for electric contact with the carriage
11
and the circuit board
13
, respectively. The strengthening plate
143
is mounted onto the end portion of the flat flexible cable
14
to facilitate the insertion of the exposed copper foil into the connecting slot (not shown) of the carriage
11
or the circuit board
13
. Further referring to
FIG. 1B
again, a portion
142
of the flat flexible cable
14
connecting to the circuit board
13
is fixed on the bottom of the lower housing
10
, and another portion
143
connecting to the carriage
11
is freely bent and stretched along with the movement of the carriage
11
.
During the movement of the carriage
11
, the flat flexible cable keeps on electrically connecting the carriage
11
with the circuit board
13
for signal transmission. The configuration of the flat flexible cable
14
changes all the time during the movement of the carriage
11
along a scanning direction indicated by an arrow C. It is understood at any moment, however, the distant end
141
of the flat flexible cable
14
from the carriage
11
, i.e. the U-turn portion, raises up to the inner surface of the platform
15
due to the flexible property thereof. Especially for an image scanner using a contact image sensor (CIS) as an image pickup device which requires close contact with the document on the platform
15
, the flat flexible cable
14
generally keeps in contact with the inner surface of the platform
15
by a part thereof. For example, at a start position where the carriage
11
is adjacent to the circuit board
13
, the flat flexible cable
14
is bent to have a U-turn point at a position relative to the position A on the platform
15
, as shown in the solid line. On the other hand, at a scanning position where the carriage
11
moves away from the circuit board
13
, the U-turn position shifts to a position B on the platform
15
along the scanning direction C, as indicated by the dotted line. As a result, abrasion is likely to occur due to the contact of the insulating wrapper
142
of the flat flexible cable
14
with the transparent platform
15
and the movement of the contact point from the position A to the position B. In general, the insulating wrapper
142
is made of a thermoplastic plastic material and the platform
15
is made of glass. As known, a general thermoplastic plastic material has a smaller hardness than the hardness of the platform
15
, and the frictional coefficient between the plastic and glass is not low enough to avoid abrasion. The plastic chips resulting from the abrasion by the glass platform may adversely affect the scanning quality.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide an anti-abrasive flat flexible cable which isolates the plastic wrapper from the glass platform to avoid abrasion.
A first aspect of the present invention relates to an anti-abrasive flat flexible cable for use with an image scanner for electrically connecting a carriage with a circuit board. The flat flexible cable is bent at different positions thereof with the movement of the carriage relative to the circuit board under a scanning platform. The anti-abrasive flat flexible cable includes a flexible conductive portion having a first end electrically connected to the circuit board and a second end electrically connected to the carriage for signal transmission between the circuit board and carriage; a flexible insulating portion wrapping around the flexible conductive portion for protecting the flexible conductive portion; and a flexible spacer portion attached onto the flexible insulating portion, and positioned between the flexible insulating portion and the scanning platform for isolating the flexible insulating portion from the scanning platform.
Preferably, the flexible conductive portion includes a copper foil.
Preferably, the flexible insulating portion is made of a thermoplastic plastic material.
Preferably, a hardness of the flexible spacer portion and a frictional coefficient between the flexible spacer portion and the scanning platform are small enough to substantially render no chip on contact.
In an embodiment, the scanning platform is made of glass, and the flexible spacer portion is made of a material selected from a group consisting of Teflon, Nylon and polyoxylated methylene (POM).
In another embodiment, the scanning platform is made of glass, and the flexible spacer portion is made of a composite material including Nylon and POM.
Preferably, the anti-abrasive flat flexible includes a rigid supporting plate mounted to each of the first and second ends of the flexible conductive portion for facilitating the exertion of an external force to insert the flexible conductive portion to a slot of the circuit board or the carriage. The flexible spacer portion is disposed between the rigid supporting plate and the flexible conductive portion, and extends along the flexible insulating portion over a half length of the flexible insulating portion.
A second aspect of the present invention relates to an anti-abrasive flat flexible cable used in a housing for signal transmission between a first and a second devices. The anti-abrasive flat flexible cable includes a flexible conducting core for conducting an electronic signal; and a flexible insulating wrapper enclosing the flexible conductive core for protecting the flexible conductive core with two opposite ends of the flexible conductive core exposed for electric connection to the first and second devices, respectively, wherein the flexible insulating wrapper includes a spacer portion possibly in contact with the housing, and a hardness of the spacer portion and a frictional coefficient between the spacer portion and the housing are small enough to substantially render no chip on contact.
Preferably, the flexible conductive core is formed of a copper foil, and the flexible insulating wrapper includes a thermoplastic layer and a spacer strip formed on the thermoplastic layer as the spacer portion.
Preferably, the spacer strip extends along the thermoplastic layer over a half length of the thermoplastic layer.
When the flat flexible cable is used in a housing including a glass plate, th
Hung Wen-Lung
Sheng Kung-Cho
Madson & Metcalf
Nguyen Chau N.
Primax Electronics Ltd.
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