The present invention relates to an improvement for a time switch capable of automatically setting, or selecting, the execution or the cancellation of a predetermined switching program operating with, for example, a 24 hour period and a weekly period. The improvement provides a more efficient design and a further manual interruption.
A conventional time switch is shown in FIG. 1. In FIG. 1, a 24 hour scale disk 1 is driven by a synchronous electric motor (not shown) to rotate one revolution for each 24 hour period.
A setter 2 is fixed at a position on the peripheral portion of the 24 hour scale disk 1. More than one setter 2 may be provided. The position is selected to correspond to a desired time by using suitable means such as a screw or the like. As time passes, the 24 hour scale disk 1 rotates, and a switch 3 is opened or closed at a desired time dependent upon the time-varying contact and loss of contact between the setter 2 and a mechanism such as a switch lever. Another scale disk 4 is used to measure the days in a week and is driven similarly to the 24 hour scale disk 1 except that it rotates one revolution during one week. The week scale disk 4 is rotationally positioned in a predetermined relationship with respect to a time position of the 24 hour scale disk 1.
A rotary switch 5 sequentially steps from one position to the next for each 24 hour from Sunday to Saturday to thereby advance seven steps for one week. This stepping is accomplished by the rotation of the week scale disk 4 through a suitable mechanism such as a train of cam wheels (not shown). The common terminal of the rotary switch 5 is connected to a power source 8. A single-pole triple-throw selecting switch 6 selects the execution or the cancellation of the daily program set on the 24 hour scale disk 1, according to each desired day of the week. There are a total of seven selecting switches 6 respectively corresponding to the days from Sunday to Saturday. Each selecting switch 6 can be set at one of three conditions. Namely the first condition is automatic or "AUTO" and its terminal is connected in series with the switch 3. The second condition is off or "OFF" and its terminal is opened or not connected. The third condition is "ON" and its terminal is connected in parallel with the switch 3 regardless of the program on the 24 hour scale disk 1.
The common terminal of each selecting switch 6 is connected in series to the respective contacts of the corresponding day in the rotary switch 5.
Referring to the operation of the switching apparatus, FIG. 1 shows the contact of the rotary switch 5 positioned at the Tuesday position, that is, the present time is Tuesday, and the selecting switch 6 for Tuesday is set at the condition of "AUTO".
In this condition, the rotary switch 5 has already been connected to the selecting switch 6, so that a load 7 is directly controlled by the switching operation of the switch 3. Namely the switching operation of the switch 3 is effected in accordance with the program set by the placement of the setter 2 on the 24 hour scale disk 1. In this condition, if the switch 3 is closed (namely, the load 7 is powered), the selecting switch 6 can be manually switched to "OFF" in order to unpower the load 7 for any necessary and temporary unpowered interruption. Further in the case where the switch 3 is open (namely the load 7 is unpowered), the selecting switch 6 can be manually switched to "ON" in order to power the load 7 for any necessary and temporary powered interruption. The above mentioned operation is for the example of Tuesday, and a similar operation as the above is of course made for other days of the week in accordance with the position of the rotary time switch 5.
According to the time switch thus constructed, it is possible to decide whether the program with the 24 hour period should be executed or cancelled each desired day of the week, by initially selecting either of the three conditions (i.e., "AUTO", "ON" or "OFF") of the selecting switch 6 corresponding to each day of the week. Further it is possible to control the selecting switches 6 independently and with priority from the contents of a program for any interrupting operation, by operating the selecting switch of the desired day of the week. Therefore it is easy to control devices which are not operated on holidays, and it is very convenient to check and maintain the load 7 such as radio receiver without stopping the entire time switch.
However, the conventional time switching apparatus, as shown in FIG. 1, has the following disadvantages. First, it is necessary to provide not only the switch 3 but also the rotary switch 5 and the selecting switch 6, especially since seven selecting switches 6 corresponding to respective days of the week are necessary. As a result, the number of parts required in its manufacture are increased and the fabrication thereof and the adjusting operation are complex. Of course, as a result, its cost is increased. Secondly, usually the rotary switch 5 is located internally in the time switch and should have a general switching capacity. However, physical constraints typically limit its switching capability to much less than the switching capacity of the switch 3 and the selecting switch 6 which are constructed as described. Therefore the switching capacity of the entire time switch is determined primarily by the switching capacity of the rotary switch 5 having the smallest switching capacity. As a result, the switching capacity of the time switch is unavoidably reduced. Thirdly, even if the load 7 is powered or unpowered independently of the predetermined program by the temporary interrupting operation effected by the manual operation of the proper selecting switch 6 according to the day of the week, if the day changes in the course of time (namely the week scale disk 4 is rotated by one revolution, such as from Tuesday to Wednesday) in the middle of the interrupt operation, the rotary switch 5 is therefore stepped to the next day of the week. In this case, the state of the load 7 is determined in accordance with the condition of the selecting switch 6 of the next day of the week rather than the interrupting condition set in the selecting switch 6 on the preceding day. That is, there is a problem that the contents of a desired interrupting operation is not necessarily executed sequentially unless not only the selecting switch 6 of the corresponding day but also the selecting switch 6 of the next day are initially set.