Over current protective circuit with time delay for a floor cleaning machine

• US 5,698,957 A
• Filed: 04/24/1995
• Issued: 12/16/1997
• Est. Priority Date: 04/24/1995
• Status: Expired due to Fees

• Current Assignee: Advance Machine Co. (Nilfisk Holding A/S)
• Original Assignee: Advance Machine Co. (Nilfisk Holding A/S)
• Inventors: Sowada, Mark J.
• Primary Examiner(s): SALATA, ANTHONY J
• Application Number:
  US08/427,200
• Time in Patent Office: 967 Days
• Field of Search: 318/434, 318/101-104, 361/23, 361/65, 361/29, 361/31, 361/42-50, 307/9, 307/41
• US Class Current: 318/434
• CPC Class Codes: A47L 9/2842 Suction motors or blowers
• CPC Class Codes: A47L 9/2857 User input or output elements for control, e.g. buttons, switches or displays
• 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: H02H 7/0857 by lowering the mechanical load of the motor

Abstract

A protective circuit controls the operation of a floor cleaning machine provided with a brush motor and a vacuum motor. The protective circuit disables the vacuum motor when an operator starts the brush motor and then restarts the vacuum motor provided it was previously running. The floor cleaning machine is also provided with provisions for adjusting the action of the brush and thus changing the load current of the brush motor. The load current of the brush motor is continuously compared to a first level overload current and an indicator alerts the operator to a first level overload condition allowing a predetermined time for the load current to be reduced by adjusting the brush. If the load current is not reduced, then the brush motor is de-energized. If a second level overload condition of the brush motor occurs at any time, the brush motor is de-energized immediately.

Claims

1. Circuit for controlling the operation of a first motor coupled to an agitating means and a second motor for creating air flow, said first motor having a first starting current value, a load current value and a load adjustment means, comprising, in combination:

first relay means for controlling the application of an electrical power source to said first motor;

first switch means coupled to said first relay means;

second relay means for controlling the application of said electrical power source to said second motor;

second switch means coupled to said second relay means;

means operatively coupled to said first switch means and to said second relay means for disabling said second motor when said first switch means is activated at a first time and to enable said second motor when a first period of time from said first time has elapsed;

means for obtaining a first signal representative of said load current value;

first means for comparing said first signal to a first reference current value;

means for operating said first relay means to disconnect said power source from said first motor if a second period of time during which said load current value has continuously exceeded said first reference current value has elapsed; and

means for operating said first relay means to disconnect said power source from said first motor if said load current value exceeds said second reference current value.

2. Circuit of claim 1 further comprising, in combination:

means for restoring operation of said second motor after said first period of time has elapsed, if said second motor was operating at said first time.

3. Circuit of claim 2 further comprising, in combination:

means for providing an overload indication to an operator when said load current exceeds said first reference current value to allow adjustment of said load adjustment means to reduce said load current value.

4. Circuit of claim 1 wherein said means for obtaining a first signal representative of said load current comprises, in combination:

a transformer having a primary and a secondary, said primary connected to said first motor, said secondary connected to a load means; and

peak detection means coupled to said load means.

5. Circuit of claim 4 wherein said first means for comparing comprises, in combination:

a comparator having a positive input terminal, a negative input terminal and an output terminal;

a reference voltage representative of said first reference current value connected to said negative input terminal;

an output of said peak detection means connected to said positive input terminal; and

said first comparator having a first output signal level when said load current value is less than said first reference current value and a second output signal level signal when said load current value is greater than said reference current value.

6. Circuit of claim 5 wherein said means for operating said first relay means comprises, in combination:

timing means including a capacitor coupled to said output of said first comparator with said output signal at a second level initiating said timing means; and

transistor means operatively coupled to an output of said timing means with said transistor means conducting to operate said first relay means to disconnect said first motor.

7. Circuit for controlling the operation of a first motor and a second motor, said first motor having a first starting current value, said second motor having a second starting current value, said second starting current value being less than said first starting current value, comprising, in combination:

first switch means operatively coupled to first relay means for energizing said first motor;

second switch means operatively coupled to second relay means for energizing said second motor;

means operatively coupled to said first switch means and to said second relay means for disabling said second motor when said first switch means is activated at a first time and for enabling said second motor when a first period of time from said first time has elapsed; and

means for restoring operation of said second motor after said first period of time has elapsed, if said second motor was operating at said first time.

8. Circuit of claim 7 wherein said first motor has a load current value and said circuit further comprises, in combination:

first means for comparing said load current value to a first reference current value;

means for denergizing said first motor if said load current value has not been reduced to below said first reference current value during a second period of time; and

means for denergizing said first motor if said load current value exceeds a second reference current value.

9. Circuit of claim 8 wherein said first motor has a load adjustment means and said circuit further comprises, in combination:

means for providing an overload indication to an operator when said load current value exceeds said first reference current value to allow adjustment of said load adjustment means to reduce said load current value.

10. Circuit of claim 9 wherein said means for obtaining a first signal representative of said load current value comprises, in combination:

a transformer having a primary and a secondary, said primary connected to said first motor, said secondary connected to a load means; and

peak detection means coupled to said load means.

11. Circuit of claim 10 wherein said first means for comparing comprises, in combination:

a comparator having a positive input terminal, a negative input terminal and an output terminal;

a reference voltage representative of said first reference current value connected to said negative input terminal;

an output of said peak detection means connected to said positive input terminal; and

said first comparator having a first output signal level when said load current value is less than said first reference current value and a second output signal level signal when said load current value is greater than said reference current value.

12. Circuit for controlling the operation of a first motor coupled to an agitating means, said first motor having a load adjustment means, a starting current value, and a load current value, comprising, in combination:

first relay means for controlling the application of an electrical power source to said first motor;

first switch means coupled to said first relay means;

means for obtaining a first signal representative of said load current value;

first means for comparing said first signal to a first reference current value;

means for operating said first relay means to disconnect said power source from said first motor if a first period of time during which said load current value has continuously exceeded said first reference current value has elapsed;

means for operating said first relay means to disconnect said power source from said first motor if said load current value exceeds a second reference current value; and

means for providing an overload indication to an operator when said load current exceeds said first reference current value to allow adjustment of said load adjustment means to reduce said load current value within the first period of time.

13. Circuit of claim 12 wherein said circuit controls a second motor for use in creating an air flow, said second motor having a starting current value less that said first motor starting current value, further comprising, in combination:

said first switch means coupled to a second relay means to disable said second motor when said first switch means is activated at a first time and to enable said second motor when a second period of time from said first time has elapsed; and

means for restoring operation of said second motor after said first period of time has elapsed, if said second motor was operating at said first time.

14. Circuit of claim 13 wherein said means for obtaining a first signal representative of said load current comprises, in combination:

a transformer having a primary and a secondary, said primary connected to said first motor, said secondary connected to a load means; and

peak detection means coupled to said load means.

15. Circuit of claim 14 wherein said first means for comparing comprises, in combination:

a comparator having a positive input terminal, a negative input terminal and an output terminal;

a reference voltage representative of said first reference current value connected to said negative input terminal;

an output of said peak detection means connected to said positive input terminal; and

said comparator having a first output signal level when said load current value is less than said first reference current value and a second output signal level signal when said load current value is greater than said first current value.

16. Circuit of claim 15, further comprising, in combination:

means for comparing a load current value of said second motor to a third reference current value; and

means for de-energizing said second motor if said load current of said second motor exceeds said third reference current value.

17. Circuit of claim 16 wherein said first motor is an induction motor having a starting winding and said second motor is a universal motor.

18. A method of operating a first motor coupled to an agitating means and a second motor for creating air flow, said first motor having a first starting current value, a load current value and a load adjustment means, said second motor having a second starting current value, said second starting current value being less than said first starting current value, comprising the following steps:

disabling operation of said second motor during a first motor start up period;

restoring operation of said second motor if said second motor was operating prior to said first motor start up

obtaining a first signal representative of said first motor load current value;

comparing said first signal to a first level overload reference signal and to a second level overload reference signal;

timing a duration of a first level overload condition;

disabling operation of said second motor if said duration exceeds a first period of time; and

disabling operation of said first motor if said first signal exceeds a second level overload reference signal.

19. A method of operating a motor coupled to an agitating means, said motor having a load current value, comprising the following steps:

obtaining a first signal representative of said motor load current value;

comparing said first signal to a first level overload reference signal and to a second level overload reference signal;

timing a duration of a first level overload condition;

disabling operation of said motor if said duration exceeds a first period of time; and

disabling operation of said motor if said first signal exceeds the second level overload reference signal, wherein said motor has a load adjustment means and said step of comparing said first signal to a first level overload reference signal and to a second level overload reference signal includes providing an overload indication to an operator when said load current value exceeds said first reference current value to allow adjustment of said lead adjustment means to reduce said load current value.

20. A method of operating a tint motor coupled to an agitating means, and a second motor for use in creating an air flow, said first motor having a starting current value greater than a starting current value of said second motor, comprising the following steps:

operating said second motor while the first motor is not operating;

disabling operation of said second motor during a first motor start up period;

starting said first motor during the first motor start up period; and

restoring operation of said second motor after the first motor start up period and while the first motor is operating.