Vacuum motor control including float switch and in-rush current restraint

• US 5,449,988 A
• Filed: 03/30/1994
• Issued: 09/12/1995
• Est. Priority Date: 03/30/1994
• Status: Expired due to Term

• Current Assignee: Nilfisk, Inc. (Japan) (Nilfisk Holding A/S)
• Original Assignee: U.S. Products, Inc.
• Inventors: Gurstein, Russell, Westlake, Richard
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US08/219,830
• Time in Patent Office: 531 Days
• Field of Search: 318/430, 318/431, 318/434, 318/482, 388/804, 388/811, 388/819, 388/829, 388/831, 388/903, 388/929, 417/40, 15/319, 15/320, 15/345, 134/21, 55/215, 55/216
• US Class Current: 318/430
• CPC Class Codes: A47L 7/0028 Security means, e.g. float valves or level switches for preventing overflow
• CPC Class Codes: A47L 7/0038 with means for emptying the tanks
• CPC Class Codes: A47L 9/2805 Parameters or conditions being sensed
• CPC Class Codes: A47L 9/2831 Motor parameters, e.g. motor load or speed
• CPC Class Codes: A47L 9/2842 Suction motors or blowers
• CPC Class Codes: A47L 9/2889 Safety or protection devices or systems, e.g. for prevention of motor over-heating or for protection of the user
• CPC Class Codes: A47L 9/2894 Details related to signal transmission in suction cleaners
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers

Abstract

A soft start power control device for a liquid vacuum motor includes a detection component for shutting off the vacuum motor when the vacuum'"'"'s recovery tank reach full capacity, and in-rush current limiting component for restraining the in-rush current to the motor when the power is switched on, whereby the motor slowly ramps up to its operating speed. The motor is switch by a triac. The device includes a component for preventing the triac from inadvertently triggering at commutation frequency. A snubber circuit is also connected in parallel with the triac to limit the dv/dt characteristic. The detection component includes a float switch to monitor the level of liquid in the recovery tank. The detection component disables the motor once the water reaches a predetermined high level, which then requires the operator to empty the recovery tank before restarting the motor.

Claims

1. A motor control device for limiting in-rush current to a motor, comprising:

a float switch means,

a triggering circuit means, and power switching means;

wherein said float switch means actuates when the water level in a liquid recovery tank rises to a predetermined height;

wherein said float switch means sends a signal to said triggering circuit means;

whereby said triggering circuit means triggers said power switching means to switch off the motor;

wherein a restart signal is sent to said power switching means after the water has been emptied from the recovery tank;

wherein upon restart, the triggering circuit means initiates a soft start of the motor through said power switching means,

wherein said power switching means is a triac,

wherein a snubber circuit is connected to said triac.

2. A device according to claim 1, wherein a series RC network is connected in parallel with said triac.

3. A device according to claim 1, wherein an optoisolator means is connected between the float switch means and the triggering circuit means.

4. A device according to claim 1, wherein said triggering circuit means comprises a full-wave trigger pulse generator.

5. A device according to claim 1, wherein said triggering circuit means receives positive feedback from the power switching means.