Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the record
Reexamination Certificate
2001-03-27
2004-03-02
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the record
Reexamination Certificate
active
06700725
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a mode switch for a magnetic recording and reproducing apparatus such as a VTR which detects an operating position of a loading mechanism for loading or unloading tapes as well as a control method for the mode switch.
BACKGROUND ART
FIGS. 8 and 9
show a mode switch
9
used for conventional magnetic recording and reproducing apparatuses.
The mode switch
9
comprises a bearing
1
a
formed in the center of a housing
1
formed of an insulator, and a common pattern
2
and a detection pattern
3
each formed concentrically in an inner bottom portion of the housing
1
on an end surface thereof and composed of a conductive material such as copper.
Reference numeral
4
denotes a rotor formed of an insulator and having a boss portion
4
a
which is formed in the center thereof and which is rotatably engaged with the bearing
1
a
of the housing
1
. The rotor
4
has a brush
5
formed on an end surface thereof and composed of a conductive material, the brush
5
rotating integrally with the rotor
4
. The brush
5
maintains contact with the common pattern
2
and the detection pattern
3
and is rotated while being arranged in a substantially radial direction in a line.
As shown in
FIG. 9
, the detection pattern
3
is divided into four position detecting sections A to D having terminals a
1
, b
1
, c
1
, and d
1
, respectively, extended therefrom. These detection positions are electrically separated and are not electrically connected together.
FIG. 10
shows the mechanism of a magnetic recording and reproducing apparatus using the mode switch
9
. Reference numeral
6
denotes a motor operated by means of outputs from a system control circuit
20
.
Rotational outputs from the motor
6
are joined to a loading mechanism
21
via a gear
7
and a reduction gear
8
. The loading mechanism
21
loads and unloads a tape. While this mechanism is operative, the mode switch
9
, having the rotor
4
joined to the reduction gear
8
, rotates and the common pattern
2
on an inner circumferential side and each detection pattern
3
on an outer circumferential side are short-circuited by brush
5
in conjunction with the rotation to enter a conductive or open state.
A common terminal COM of the mode switch
9
is connected to an L (Low) level, while the terminals a
1
, b
1
, c
1
, and d
1
of the mode switch
9
are pulled up to an H (High) level, with these levels input to the system control circuit
20
so that the rotation of the motor
6
can be controlled by means of a microcomputer (not shown) to achieve appropriate operations.
FIG. 11
shows a signal which is input to the system control circuit
20
if the mode switch
9
is rotated, and when the brush
5
is rotated once counterclockwise from between the detection positions A and D shown in FIG.
9
.
For example, at the detection position A, the brush
5
is in contact with the common pattern
2
and with the detection pattern connected to the terminal a
1
. In
FIG. 10
, a switch for the terminal al of the mode switch
9
becomes conductive and is pulled up, so that an input from the terminal a
1
to the system control circuit
20
has the L level, while the other terminals are in the open state and thus have the H level.
Likewise, at the detection position B, the terminal b
1
has the L level, while the other terminals have the H level. At the detection position C, the terminal c
1
has the L level, while the other terminals have the H level. At the detection position D, the terminal d
1
has the L level, while the other terminals have the H level.
Since the common pattern
2
is electrically connected to no detection pattern at passed positions other than the detection position, the outputs from the terminals a
1
to d
1
all have the H level. The logic of the signal input to the system control circuit
20
varies depending on the detection position A to D, so that checking the logic of the input from the mode switch
9
enables the loading mechanism to be detected at the position A to D.
FIGS.
12
(
a
), (
b
), and (
c
) show how a tape is loaded.
Reference numerals
10
,
11
,
12
, and
13
denote a cassette, a magnetic tape, a drawing post, and a cylinder. FIG.
12
(
a
) shows an unloading state where the brush
5
of the mode switch
9
is at the detection position A. FIG.
12
(
b
) shows a half loading state where the brush
5
of the mode switch
9
is at the detection position B. FIG.
12
(
c
) shows a loading completed state where the brush
5
of the mode switch
9
is at the detection position D. The position of the brush
5
of the mode switch
9
moves in connection with the loading mechanism
21
as shown in
FIG. 10
, so that each loading position corresponds to the detection position.
Thus detecting the output from the mode switch
9
enables the position of the loading mechanism
21
to be detected, and controlling the motor
6
enables the tape loading operation to be controlled.
Since the detection positions A to D of the mode switch
9
shown in
FIG. 9
each correspond to one of the loading positions, checking the output of each terminal enables its absolute position to be determined. This type is hereafter referred to as an “absolute-position detection type”.
FIG. 13
is another type (relative-logic-based detection type) of mode switch
9
.
The detection patterns
3
connected to the terminals a
2
, b
2
, and c
2
are sequentially and concentrically formed outward from a central portion of the mode switch, with the common patterns
2
concentrically formed in an outermost periphery of the mode switch and each connected to a terminal COM. Portions J of the same concentric track which are shown by broken lines are i electrically connected together but the surfaces thereof are molded of an insulator such as a resin.
FIG. 14
shows input signals to the system control circuit
20
shown in
FIG. 10
, which are obtained if the mode switch
9
is rotated. The signals shown in
FIG. 14
are obtained when the brush
5
shown in
FIG. 13
is rotated once counterclockwise from between the detection positions A and D.
In the case of the absolute-position detection type mode switch
9
shown in
FIG. 9
, timings for the detection positions depend on the pattern length of each detection pattern
3
at the detection position A to D. In the case of the mode switch
9
shown in
FIG. 13
, however, the common pattern
2
is divided into the positions A to D and the timings for the detection positions do not depend on the length of the detection pattern
3
but generally on the length of each position A to D of the common pattern
2
. Since the closer to the outermost concentric circle the position is, the longer the circumferential length per angle is and the higher the angular precision obtained is, the common pattern
2
is disposed peripherally.
Also in the mode switch
9
shown in
FIG. 13
, the logic of the output of the terminal a
2
, b
2
, or c
2
varies depending on the detection position A to D, so that determining the logic enables the loading position to be detected. In this type of mode switch, the detection patterns
3
connected to the terminals a
2
, b
2
, and c
2
do not correspond to the different loading positions, but determining the output logic of the terminals a
2
, b
2
, and c
2
enables the loading position to be determined. This type is hereafter referred to as a “relative-logic-based detection type”.
To realize many functions of a magnetic recording and reproducing apparatus such as a VTR, inputs from many switches or sensors are connected to the microcomputer in the system control circuit
20
, so that a mode switch is required which obtains accurate outputs using as few inputs to the system control unit
20
as possible.
In the “absolute-position detection type” mode switch
9
, since each terminal corresponds to one of the loading positions, if chattering or noise occurs in the brush, the terminal may have the same logic as any of the passed positions but never has that as the other detection positions. This prevents an incorrect detection pos
Hudspeth David
Matsushita Electric - Industrial Co., Ltd.
Parkhurst & Wendel L.L.P.
Wong K.
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