GB1253745A - Dual speed timer for electronic ovens - Google Patents

Abstract

1,253,745. Time switches. INTERNATIONAL REGISTER CO. 6 Oct., 1969 ]2 May, 1969] No. 49037/69. Heading H1N. An interval timer with two speeds, e.g. for use in microwave ovens, comprises a time interval setting shaft 23 on which switch cam assemblies 34, 35 are non-rotatably and slidably mounted for closing and opening switches 30, 31 at the beginning and end of the set time interval, a gear train interconnecting the timer motor 74 and shaft 23 and including a high speed gear 73 and a low speed gear 72, and a knob 24 for shifting the connection of the shaft 23 from the high speed gear 73 to the low speed gear 72 to change the time that the switches are closed by their respective cam assemblies. A driven gear 71 provides the connection between shaft 23 and gear 73 or 72. Shaft 23 is spring biased to normally maintain gear 71 in engagement with gear 73, so a pivoted, spring-biased latch 85 is needed to hold gear 71 against gear 72 when shaft 23 is endwise shifted to that position, the latch having a tooth 86 engaging a latch cam 40 secured to shaft 23. A shoulder 95 on latch 85 acts as a stop for limiting rotation of latch cam 40 in the " OFF " position. Latch 85 is released as cam 40 approaches the end of the set time interval, tooth 86 then registering with a notch 94 in the cam 40. If knob 24 is accidentally moved inwardly when set for low speed operation, latch 85 is released. An audible signal is given at the end of the set interval by an adjustable pivoted buzzer arm 100 approaching an extension 103 of the magnetic field structure of the synchronous motor 74, the arm 100 being held in an inoperative position until a pin 114 on driven gear 71 engages a cam surface 113 on the end 112 of a pivoted lever 107 retaining the arm 100. Arm 100 vibrates until motor 74 is de-energized. Microswitches 30, 31 open and close in predetermined sequence and control, e.g. a cooling fan for a microwave generator and the energization of the generator, as well as the energization of the motor 74, Fig. 16 (not shown). Different diameter gears may be substituted in the gear train to vary the possible time interval settings, Figs. 12-14 (not shown), a choice of openings 81, Fig. 15 (not shown), being provided in the back plate 14. Typical two-speed, time scales are 0-5 or 0-20 minutes, Fig. 2 (not shown), as set on a dial 22 rotated by knob 24.