SUCTION CLEANER

Abstract: A suction cleaner has a 'power boost' control, enabling the user to cause the suction motor (16) to operate at a power output in excess of its rated power output for a short period. On release of the control, the motor (16) returns to its original power. Boost timing means time the cumulative period of boosted power output, and inhibits boosted operation of the motor once the cumulative period has exceeded a limit value. The cumulative period is reset to zero if the boost control is not used during a fixed recovery period. In this way, the 'power boost' facility may be used several times in rapid succession, provided that the total boosted period does not exceed the limit value.

Description: The present invention relates to suction cleaners and in particular to suction cleaners having a "power boost" facility, that is a facility whereby the user has the option of boosting the suction power for a short period, for example in order to remove dirt from particularly heavily soiled areas of the floor, by running the main suction motor temporarily at a power level exceeding its rated power. Suction cleaners having power boost features of this type are already known, but they are rather inflexible. The user requiring additional power for a short period presses a "power boost" button, which causes the main suction motor to operate at a power in excess of its rated power level for a fixed period, say ten seconds, then reverting to its previous power level. There then follows a timed recovery period of say sixty seconds, to allow the motor to cool off, during which the power boost facility cannot be activated again. Although the known cleaners are very effective if the power boost facility is not required too often, they are not particularly suited for the fairly common situation in which the user would like a little extra power, fairly frequently but for short periods, for example to deal with a number of small, but closely spaced, heavily soiled patches on a floor. WO 87/01921 which serves the basis for the preamble of the independent claim discusses a suction cleaner having control means arranged to control the power output of a variable speed suction motor, and user-operable switch means coupled to the control means such that, on the actuation of the switch means, the control means causes the motor to operate for a limited period at a power output in excess of its rated power. It is an object of the present invention at least to alleviate the problems of the prior art. It is a further object of the invention to provide a suction cleaner with an improved power boost facility, giving the user increased control. According to the present invention there is provided a suction cleaner having control means arranged to control the power output of a variable speed suction motor, and user-operable switch means coupled to the control means such that, on the actuation of the switch means, the control means causes the motor to operate for a limited period at a power output in excess of its rated power output, characterised in that, on the release of the switch means before the end of the limited period being reached, the control means causes the motor to return to a power output not exceeding its rated power output. Preferably, the control means may cause the motor to return to the previously prevailing power output. Boost timing means may be provided which are arranged to time the period of boosted power output over a plurality of actuations of the switch means, with boost inhibit means being arranged to inhibit operation of the motor at the boosted power output for a recovery period once the cumulative period of boosted power output exceeds a limit value. The cleaner may include recovery timing means arranged to time the recovery period and means for lifting the inhibit at the end of the recovery period. The cleaner may also include reset means arranged to reset the said cumulative period of boosted power output to zero if the switch means is not actuated during the recovery period. In one specific embodiment, the recovery period is suspended if the motor is stopped during the recovery period and resumed when the motor starts again. In an alternative embodiment, the recovery period continues even when the motor is stopped. Desirably, the control means comprises a microprocessor. The various timing means, the inhibit means, and the means for lifting the inhibit may also be provided by the microprocessor. The switch means may be arranged to produce a signal on a control line when actuated, the microprocessor being arranged to read the signal on the control line, for example after a fixed number of clock cycles. Conveniently, the signal on the control line may be a voltage signal, which is applied to the microprocessor via an analogue to digital converter. The use of such a converter enables the control line to be used for several different things at once. In particular, the control line may in addition be arranged to carry other signals, at different voltages, representative of the actuation of other user operable switch means. Such switch means may include, for example, an on/off switch for the cleaner, a switch instructing the control means to increase the power output of the suction motor, and a switch instructing the control means to decrease the power output of the suction motor. The switch means may be on a hand grip, with the control line passing from the grip, along a suction hose, to the microprocessor in the main cleaner body. To enable a power-driven rotating brush to be incorporated in the suction nozzle, the hose may carry exactly three lines, the control line, a live ac power line, and a line serving the dual function of neutral power line and Ov reference for control signalling. For the purposes of this specification the rated power output of the motor means any one of the following: (a) the maximum available power output of the motor, running at a constant speed; (b) a statement to that effect made by the manufacturer. The invention may be carried into practice in a number of ways and one specific embodiment will now be described, by way of example, with reference to the drawings, in which: Figure 1 is a simplied block diagram showing the power boost circuitry; Figures 2A and 2B show a more detailed circuit diagram showing the circuit on the cleaner body; Figure 3 is a detailed circuit diagram showing the hand grip controls; Figure 4 shows how the motor supply voltage and triac control line voltage varies with motor power levels; and figures 5A and 5B show a flow diagram illustrating the microprocessor timing routine. Figure 1 is a simplified block diagram of an embodiment of the invention. The suction cleaner is illustrated very schematically by a first dotted line 10 which represents the main cleaner body, which is desirably of the canister or cylinder type, and a second dotted line 12 which represents a hand grip and control panel on the cleaner hose. The hose itself is not shown, but it will be appreciated that the control lines 14 extending between the body and the hand grip will in practice pass down the hose. Within the cleaner body 10 there is a main suction motor 16, supplied with power from external A/C mains terminals 18, and adjustable in power output by means of a triac motor control circuit 20. Control is effected by applying a variable width squarewave signal to the triac gate along a line 23 from a microprocessor 22. As may be seen in figure 4, the microprocessor 22 is arranged to produce a signal along the line 23 having one of a number of pulse widths, corresponding to 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% and 120% of the rated motor power. Examples of these may be seen respectively in the lower traces of the graphs A to D; the upper graphs show the corresponding motor supply voltages. The situation illustrated in figure 4D, with the signal on the line 23 remaining high, corresponds to the "power boost" situation in which the motor is running, for a limited period, at a power level in excess of its rated value. The microprocessor 22 determines which of the signals, A to D (or other signals for intermediate power settings), to apply to the line 23 in accordance with an input received from an analogue to digital converter 24 which, in turn, receives an input signal along a data line 26 which stretches from the cleaner body along the hose to the hand grip. The user of the cleaner can vary the voltage on the line 26, and thus the power of the motor, by pressing an "increase power" button 28, a "decrease power" button 30 or a "power boost" button 32 on the hand grip. These three buttons are switches which are connected to the line 26 at different points in a potential divider 34. Thus, pressing a particular button will result in a particular voltage on the line 26. This voltage is converted into a digital signal by the analogue to digital converter 24, and the output from this converter is scanned cyclically by the microprocessor 22, a particular value being recognised as being, for example, "boost button pressed". To ensure that the various voltage values on the line 26 are well defined, the line is attached within the cleaner body to a pull-up resistor 40 which is itself connected to the positive terminal of a D/C power supply 42. An on/off switch 36 is provided in the line 26, on the hand grip, and the microprocessor is arranged to recognise an open circuit as an instruction to switch off the main motor 16 entirely. Completing the circuit from the far end of the potential divider 34 to the neutral mains terminal is a neutral and zero volts reference line 38. The width of the squarewave signal which the microprocessor places on the control line 23 in dependence upon the power setting selected is timed in relation to a zero crossing reference 44 derived from the mains power supply. Thus, the voltage on the line goes high a specified number of milliseconds after the zero crossing of the mains voltage, depending upon the power setting selected, and is then reset to low on the next zero crossing. Motor power control is incremental by means of the "increase power" 28 and "decrease power" 30 buttons. Depression of the first of these buttons gives rise to advancement of the triac firing point to the next of a number of stored time values, whereas depression of the latter button retards the firing point. Figures 2A, 2B and 3 are more detailed circuit diagrams of the circuits shown in simplified form in figure 1. It is not proposed to discuss these figures in detail since it should be evident from the corresponding numerals shown on figure 1 which parts of the complete circuit are involved in power boost operation. It will clearly be seen that, in practice, the signal on the control line 23 is applied to the base of a control transistor TR1, which switches the triac gate voltage to plus eight volts when the signal on the line 23 goes high. In use, when the power boost button 32 is pressed the suction capability of the cleaner is increased to 120% of the rated motor power by making the triac 20 conduct over the entire mains cycle. When the button 32 is released the cleaner reverts to its previous power level. Of course, this boosted power level cannot be continued indefinitely since it would cause the motor to overheat, and the microprocessor is therefore programmed to allow the boost facility to be used for a maximum period of ten seconds at a time; after this period, use of the boost facility is inhibited for a recovery period of one minute, after which the facility can again be used for up to a further ten seconds. If the button 32 is depressed for a period of less than ten seconds, boost operation may be activated again repeatedly until an aggregate boost duration of ten seconds is reached, whereupon the one minute recovery period will be executed. Thus, a user of the cleaner is able to use the boost facility for short periods, relatively frequently, whenever a particularly soiled patch of floor is encountered. This is in contrast to the known "boost facilities" available on current cleaners, where pressing the boost button provides a boosted power output for a fixed period of, for example, ten seconds regardless of the period for which the button is depressed. After that, the facility is disabled entirely until the end of the recovery period. Accordingly, the boost facility is somewhat inflexible. The timing arrangements for the boost facility of the present invention are determined by the programming of the microprocessor 22, and can therefore be very flexible. An exemplary flow diagram of a possible timing routine is shown in figure 5. This timing routine operates on a fixed clock cycle, that is it restarts from point x every, for example, 0.1 seconds. The time required to complete the loop, that is between starting from point x and returning to that point, will of course be less than 0.1 seconds. As will be evident to the reader if the flow chart is followed through carefully, the routine shown incorporates cumulative timing of power boost periods, with the sixty seconds recovery period being commenced on reaching an aggregate power boost period of ten seconds. Cumulative power boost duration is also reset to zero if sixty seconds elapse between any two actuations of the power boost button. If the motor is stopped by actuation of the on/off switch 36, timing is continued as power is still available to the microprocessor 22. In an alternative arrangement (not shown) the recovery period could be suspended if the motor is stopped during such a period and resumed when the motor starts again. This latter arrangement may in some ways be desirable since the motor cools down only fairly slowly when it is stationary. Finally, turning back again to figure 1, it will be appreciated that the analogue to digital converter 24 could be dispensed with if the power boost button 32 were to be located on the cleaner body or, alternatively, if the control line 26 were used to carry only a signal indicative of the power boost button being depressed or otherwise. The reason that the converter 24 is used in the preferred embodiment is that it enables a single line 26 to be used for several different purposes. This enables the number of lines passing down the hose to be kept small. In particular, in the preferred embodiment there are only three lines, the dataline 26, the neutral and zero volt reference line 38, and a live line (50 in figure 2) which is used to supply mains power to a powered nozzle (not shown) at the end of the hose.

Claims: A suction cleaner (10,12) having control means (22) arranged to control the power output of a variable speed suction motor (16), and user-operable switch means (32) coupled to the control means such that, on the actuation of the switch means, the control means causes the motor to operate for a limited period at a power output in excess of its rated power output, characterised in that, on the release of the switch means before the end of the limited period being reached, the control means causes the motor to return to a power output not exceeding its rated power output. A suction cleaner as claimed in Claim 1 in which the control means is arranged to cause the motor to return to the previously prevailing power output on release of the switch means. A suction cleaner as claimed in Claim 1 or Claim 2 including boost timing means (22) arranged to time the period of boosted power output over a plurality of actuations of the switch means (32), and boost inhibit means arranged to inhibit operation of the motor at the boosted power output for a recovery period once the cumulative period of boosted power output exceeds a limit value. A suction cleaner as claimed in Claim 3 including recovery timing means (22) arranged to time the recovery period and means (22) for lifting the inhibit at the end of the recovery period. A suction cleaner as claimed in Claim 3 or Claim 4 including reset means (22) arranged to reset the cumulative period of boosted power output to zero if the switch means (32) is not actuated during the recovery period. A suction cleaner as claimed in Claim 5 in which the recovery period is suspended if the motor (16) is stopped during the recovery period and resumed when the motor starts again. A suction cleaner as claimed in any one of the preceding claims in which the control means comprises a microprocessor (22). A suction cleaner as claimed in Claim 7 in which the switch means (32) is arranged to produce a signal on a control line (26) when actuated, the microprocessor being arranged to read the signal on the control line. A suction cleaner as claimed in Claim 8 in which the signal on the control line (26) is a voltage signal which is applied to the microprocessor (22) via an analogue to digital converter (24). A suction cleaner as claimed in Claim 8 or Claim 9 in which the switch means (32) is on a hand grip (12) of the cleaner, the control line passing from the grip along a flexible suction hose to a main cleaner body (10). A suction cleaner as claimed in Claim 10 in which the flexible hose carries exactly three electrical lines, and no more: the control line (26), a live power line (50) and a neutral power line (38).

Inventors: METRAL, JEAN-CLAUDE
Applicants: HOOVER LIMITED
Application year: 1989
Main classification: A47L9
IPC codes: A47L9