Dynamic information storage or retrieval – Dynamic mechanism subsystem – Mechanism condition or storage medium responsive control
Patent
1987-03-02
1989-05-02
Levy, Stuart S.
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Mechanism condition or storage medium responsive control
369226, G11B 306, G11B 1706
Patent
active
048274674
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a switch-off device as recited in the preamble to the major claim.
A switch-off device extensively similar to the one recited in that preamble is known from German Patent No. 1 243 412. It is provided with a screen that is connected to the pickup arm and passes through a light barrier as the arm swings. Providing the screen with a series of holes in such a way that a higher number of pulses will be detected due to the higher swinging speed per unit of time in the lead-out groove is already state of the art. This solution, however, does not work very satisfactorily, and both manufacturing costs and demands on precision are high. A number of different timing components for the various speeds of the drive mechanism are accordingly connected in and can be traveled through in accordance with the aforesaid patent. Thus, when the pickup arm is swinging at a prescribed speed, the drive mechanism is switched off by means of a transistorized switching relay employing the voltage that occurs at its RC components. The level of voltage depends on how rapidly the current of light in the light barrier changes.
The data in relation to the lead-out groove pitch that have been standardized for records of different speeds (78, 33 1/3, and 45 rpm), the various values in relation to the positions of what is called the sharp range, of the last marker groove and last modulated groove, and of the final grooves with the particular permissible tolerances, and finally the demand for an extremely inexpensive way of embodying the sidetrack function, all lead to the object of employing an actual electronic solution for that purpose.
This object is attained in accordance with the invention in a device like that recited in the preamble to the major claim by means of the characteristics recited in the body of that claim.
Further details and embodiments will be evident from the subsidiary claims and from the description of one embodiment.
The sharp range is defined in accordance with the standard between the last marker groove and the last modulated groove, in which the drive mechanism is switched off and optionally the pickup arm lifted and returned.
The bar code on the screen, a pattern of parallel and very narrow light and dark fields of equal width supplies, due to scanning with the light barrier, a sine-like voltage at the output terminal of the detector even in the sharp range. Higher-frequency effects deriving from utility modulation and eccentricity are imposed on the voltage. To obtain information that is independent thereof, a square-wave former that operates by switching hysteresis is positioned in the first stage of the connected processing circuit. The output terminal of the wave former is connected to mutually parallel branches of a high- and low-level processor. The high and low thresholds of these levels are initially detected in these parallel branches to determine the limits of the existing time window. The individual acceptable high or low pulses, stored in a memory, are then compared. The information derived from the comparators, a high and a low pulse, is added in subsequent stages and compared with stored reference times in another subsequent stage. The output signal from this stage supplies the desired unambiguous and undisturbed criterion for the switching process, which is initiated in the next stage.
The use of a light barrier with very high resolution in relation to the very narrow light and dark fields of 200 .mu.m results in a practical way in a very satisfactory switching sensitivity of high reliability at low expense in that a microprocessor that is already present anyway is employed.
One embodiment of the invention will now be specified with reference to the drawings, wherein
FIG. 1 is a simplified perspective view of the pickup arm, swing sector, screen, and light barrier,
FIG. 2 is a block diagram of a processing circuit, and
FIG. 3 shows two graphs illustrating the function of the processing circuit from FIG. 2.
FIG. 1 shows a light barrier 1 that a screen 5 enters when a pickup arm
REFERENCES:
patent: 4320496 (1982-03-01), Kikuchi
patent: 4437181 (1984-03-01), Kishima
patent: 4453245 (1984-06-01), Sugiyama et al.
patent: 4712100 (1987-12-01), Tsunekuni et al.
Deutsche Thomson-Brandt GmbH
duBois Steven M.
Fogiel Max
Levy Stuart S.
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