Device for starting automatically an auxiliary unit when switching on a main unit

• US 5,120,983 A
• Filed: 09/13/1991
• Issued: 06/09/1992
• Est. Priority Date: 07/05/1988
• Status: Expired due to Fees

• Current Assignee: Bsg-Schalttechnik GmbH & Company KG
• Original Assignee: Bsg-Schalttechnik GmbH & Company KG
• Inventors: Samann, Rudolf
• Primary Examiner(s): Pellinen, A. D.
• Assistant Examiner(s): Gaffin, Jeffrey A.
• Application Number:
  US07/759,830
• Time in Patent Office: 270 Days
• Field of Search: 307/38, 307/39, 307/40, 307/41, 307/64, 323/299, 323/300, 323/357, 323/358
• US Class Current: 307/38
• CPC Class Codes: H02P 25/14 Universal motors H02P25/12 takes precedence

Abstract

In connection with an automatic starting feature for an auxiliary unit, preferably a vacuum cleaner, which is switched on simultaneously when a main unit, for example an electric hand tool, a machine tool, or the like, is started it is proposed to trigger a conventional (phase) control circuit provided for the auxiliary unit by means of a current sensor taking the form of a ring-core bushing transformer in a manner such that the electric motor of the auxiliary unit is switched on with a certain delay (smooth-starting feature). The ring-core bushing transformer is designed in such a manner that, for producing clear firing pulses for the triac of the auxiliary unit, the primary winding is formed by the one turn of the electric supply line of the main unit and passed through the central opening of the ring core. The design of the ring-core bushing transformer is such that the transformer assumes the state of saturation when a predetermined output threshold value is reached so that even very high primary currents caused by the main unit during operation will not overdrive the (phase) control circuit and, in particular, not damage the triac.

Claims

1. A device for automatically starting an auxiliary electrical unit when switching on a main electrical unit comprising a control circuit for detecting, by means of a current sensor (16), that the main unit has started and for starting the auxiliary unit, wherein the current sensor (16) is a ring-core bushing transformer (18) having its secondary winding (90) in the control circuit for the auxiliary unit (12) and having its primary winding in a supply line (20) for the main unit (11), said ring-core bushing transformer having a state of saturation without overloading and overheating when a predetermined primary current is reached, said predetermined primary current being in the low range of anticipated main unit operating currents and sufficient for generating firing pulses for a triac of said control circuit.

2. A device according to claim 1, wherein said auxiliary unit includes connection terminals, the control circuit being part of an additional circuit (10), said additional circuit including supply lines subject to connection to a supply voltage and connecting the connection terminals of the auxiliary unit across said lines for connection to said supply voltage via a triac (19,19'"'"') in series, the additional circuit comprising a socket for connection with the main unit (11), said socket being connected to said supply lines to the same supply voltage and, one said supply line is in circuit with said ring-core bushing transformer (18).

3. A device according to claim 2, further comprising a supplementary circuit (53), said supplementary circuit deactivating a portion of the control circuit under certain operating conditions of the auxiliary unit, said auxiliary unit not operating when the main unit is on.

4. A device according to claim 3, wherein said auxiliary unit is a water exhauster and further comprising water level sensors (56a,56b) for detecting the maximum admissible water level in the water exhauster, said sensors (56a,56b) being in circuit to activate the control circuit.

5. A device according to claim 4, wherein the water level sensors (56a,56b) activate said control circuit to switch off said auxiliary unit when a predetermined water level is exceeded.

6. A device according to claim 1, wherein the ring-core bushing transformer (18) comprises a secondary winding wound about a toroidal body of the ring core, said body having a central opening, the primary winding being formed by one turn of said one supply line connected to said socket for the main unit (11), said one supply line passing through the central opening of the ring core.

7. A device according to claim 6, wherein the auxiliary unit includes a motor and the control circuit includes a potentiometer (45) for regulating the speed of the motor of the auxiliary unit.

8. A device according to claim 6, wherein said auxiliary unit includes a motor and said control circuit includes a capacitor (41), for effecting smooth-starting of the motor of the auxiliary unit.

9. A device according to claim 8, wherein a discharge line is subject to connection in parallel to the smooth-starting capacitor (41), and the discharge line is connected when the current sensor (16) of the control circuit senses that the main unit (11) has started, the points in time when the two units, supplied with electrical power by the additional circuit (11), are switched on, are separated relative to each other.

10. A device according to claim 9, wherein a contact breaker (52) prevents discharging of the smooth-starting capacitor (41), normal operation of the vacuum cleaner, without the automatic starting feature, but with speed regulation by said potentiometer (45), is enabled when this contact breaker is actuated.

11. A device according to claim 9, wherein a triggering circuit for the smooth-starting capacitor (41) comprises a time-lagging element (50,51) which delays for a predetermined period of time a switching command to turn off said auxiliary unit when the main unit (11) is switched off, an after-running operation of the auxiliary unit being implemented.