WO2011088500A1

WO2011088500A1 - Equipment safety control

Info

Publication number: WO2011088500A1
Application number: PCT/AU2011/000045
Authority: WO
Inventors: Zdzislaw Bruszewski
Original assignee: Zdzislaw Bruszewski
Priority date: 2010-01-21
Filing date: 2011-01-18
Publication date: 2011-07-28
Also published as: AU2011207100A1

Abstract

A safety control method and system to activate equipment includes multiple operation of an activation device e.g. as a safety interlock, such as a manual foot or hand control (e.g. a trigger, switch, pedal or button) to initiate activation of the equipment. Activation of the device can be required within at least one predetermined time period can, such as between consecutive operations of the actuation device or the overall period between a first required operation of the actuation device and a last required operation of the actuation device to activate the equipment, or a combination of both periods. The safety interlock can require double or triple press of a switch, button, trigger or other user control before the equipment is activated. The safety interlock (10) can prevent cyclic (ON-OFF-ON) operation of the activation switching device such as relays, Mos FETs, solid state relays, RCRs, contactors or triacs. Also, the safety interlock system can include a logic system (18) co-operating with a voltage and/or amperage sensing unit (20) for the electrical device. Rotation may be detected by a sensor and the equipment slowed or stopped for safety if rotation is above or below a safe level.

Description

EQUIPMENT SAFETY CONTROL

TECHNICAL FIELD

The present invention relates to safety control for equipment such as electrical power tools and machinery.

BACKGROUND

Home, commercial, industrial and mining use of power tools and machinery can be dangerous. Many pieces of equipment have limited or no protection from accidental activation of the tool, which increases the likelihood of accidents in the home or workplace. For example, electrically powered grinders or drills create a high risk environment when the switch is accidentally pressed. Accidental or unintentional activation of such equipment can cause serious damage to the human body.

Some devices use multiple safety switch arrangement whereby the operator is required to activate a first safety switch in order to release the main activation switch for the equipment. Other safety devices utilise twin switches that must both remain operated at the same time for the equipment to remain activated. Many pieces of equipment, including various types of power tool equipment, have limited or no accidental activation safety control. The need for two switches makes initial activation of the equipment awkward to commence, especially if the operator is required to wear gloves when using the equipment, because the user's hand and fingers must reach to and depress the switches either together or one after the other, requiring at least two fingers to use. Furthermore, in the case of twin mechanical safety switches that both need to remain operated at the same time, the user's hand can become fatigued or strained.

It would therefore be desirable to provide safety control for equipment that requires only one activation control whilst maintaining activation safety. This reduces the risk to a user by introducing a safer method and device in operating the power tools.

It is further desirable of the present invention to provide electronic safety control for safe activation of equipment. It is further desirable for the present invention to replace instantaneous activation mechanical triggers with electronically controlled triggers.

SUMMARY OF THE INVENTION

With the aforementioned in mind, an aspect of the present invention provides a safety control method to activate equipment, the method including multiple operation of an actuation device to initiate activation of the equipment.

A further aspect of the present invention provides a safety control system for power equipment, the safety control system including an actuation device and an interlock that prevents activation of the equipment by the actuation device until the actuation device has been operated at least twice.

Multiple operation of the same actuation device avoids the need for a user or operator to operate multiple separate switches either together, which requires coordinated timing of operation or one switch releasing the next. Furthermore, utilizing the one control multiple times to activate the equipment reduces the number of mechanical parts and associated wear and maintenance problems otherwise required with multiple switches.

Activation of the equipment may be controlled by an electronic interlock that determines whether the actuation device has been operated at least twice, preferably within a predetermined time-span between the first operation and the second and/or each subsequent operation.

Activation may be by double or triple actuation of the actuation device, such as the press of a switch, button or other control, before the power tool is activated.

Activation may be by:

1 . Double depress and hold of the actuation device i.e. depress - release - depress and hold closed to maintain the equipment activated.

2. Double depress and automatic sensing of power tool use i.e. depress - release - depress - release, and the tool remains activated until a further depress - release action occurs.

3. Triple depress and hold of the actuation device i.e. depress - release - depress - release - depress and hold closed to maintain the equipment activated. 4. Triple depress and automatic sensing of power tool use i.e. depress - release - depress - release - depress - release, and the tool remains activated until a further depress - release action occurs.

Actuation of the actuation device (such as depressing a switch) may be required to be done within a specific time period. For example, the second, third etc depress may be required to occur within one or two seconds or fractions of a second of the previous depress.

Preferably, when the actuation device, such as a trigger, is released, to operate power tools again a user may be required to repeat the activation method above (e.g. double, triple depress).

The actuation device may be foot or hand controlled.

For additional safety, the equipment or control systems may have one or more overload switches to prevent burning of motor wires or overloading of the system.

To hold the automatic activation process a sensor and/or sensing circuit can be used, such as a current and/or voltage control unit or electronic pickup (such as a Hall effect sensor) or optical sensor in cooperation with rotation of the armature. If for some reason the motor's armature slows down to safety operation level then the safety device automatically switches off power supply to the motor.

If there is any disruption to power supply to the equipment, such as a main circuit breaker tripping or power outage, the interlock may prevent the equipment automatically switching back on when power is restored. Traditionally, when power is restored the equipment would automatically startup again, which can be dangerous and risks injury to personnel. For example, an angle grinder may suddenly startup when power is restored, which could injure someone holding or working on that equipment. Embodiments of the present invention prevent such risks by preventing the equipment from starting up until the actuation device is again actuated in the required manner. The interlock can operate to prevent the equipment turning on automatically when power is restored until the actuation device, such as the equipments ON-OFF switch, is depressed - released and either held or released in the required manner for that equipment before the equipment will again activate. This provides a major safety feature to help avoid injury to personnel. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a diagrammatic representation of an embodiment of the present invention.

Figures 2a and 2b show diagrammatic representations of embodiments of the present invention. Figure 2a shows an embodiment utilizing a MosFET and Figure 2b an embodiment utilizing a relay, solid state relay and/or contactor or one or more triacs. DESCRIPTION OF PREFERRED EMBODIMENTS

Power operated equipment, such as grinders, cutting tools or drills, typically have an activation switch. A user depresses the actuator a first time. In this embodiment the actuator is a manually (hand or foot) operated switch. If nothing else is done, the equipment does not activate. If the user depresses the actuator a second time within a predetermined period after the first depress, the equipment is activated or at least enabled to operate. According to one or more embodiments, the switch may need to be activated more than twice within a predetermined timeframe, either within an overall timeframe for all depresses or a predetermined timeframe between each depress, or a combination of both.

An electronic/electrical unit or circuit may determine that the actuator has been depressed. This relays or sends a control signal to the equipment to activate the equipment once sufficient depresses have been fulfilled. The electronics/electrical unit or circuit may include a counter or timer or may operate a counter, timer or logic module to determine the period between the first and any subsequent depresses of the switch. Activation of the actuator switch may be hard-wired and/or transmitted wirelessly to a control portion of the control system and/or the control system may be wirelessly and/or hard-wired to activate the equipment.

Figure 1 shows a diagrammatic representation of an embodiment of the present invention. In an electrical equipment activation system 10, there is provided a low voltage control 12 side and a main power/supply or operating voltage 14 side. Multiple activation of the control switch 1 6 is detected by the logic system 18. Provided the activation conditions are met i.e. the correct number of activations of the switch, within a predetermined time if applicable, and any optional hold of the switch fulfilled, the logic system will allow the power switching system 20 to activate the motor 22 of the equipment. Unless the required activation sequence is enacted, the logic system 18 will not allow the equipment to activate. A manual override may also be provided should the logic system malfunction, be inoperative or simply not be required or appropriate for a given application. A sensor 24 determines whether the motor's armature is rotating at an expected or safe rate. If the armature slows below a safe rate of rotation, due, for example, to a faulty bearing or drag due the swarf in a drill bit, a signal is sent to switch off the equipment. The sensor 24 can be an electronic or optical sensor, such as a Hall effect sensor.

Forms of the present invention provide a safety interlock system to prevent cyclic (ON-OFF-ON) operation of equipment activation switching device(s) such as relays, MosFETs, solid state relays, RCRs and/or contactors, triac(s).

The equipment may be activated by multiple actuation of the actuation device, such as a switch. Continued activation of the equipment can require the actuation device to be maintained closed in the sense that a switch can be maintained closed. Release of the actuation device thereby stopping the equipment. Alternatively, multiple operation and release of the actuation device can be sufficient for required applications to maintain the equipment in an activated state, and a further actuation of the actuation device is required to stop the equipment. For example, two or three actuations with the device held closed on the last of those actuations can activate the equipment, with release stopping the equipment. Alternatively, two or three actuations (as selected for a particular application) and release of the device can start the equipment and a fourth actuation and release stops the equipment. Other combinations of multiple actuation and release are envisaged. The number of actuations can be varied within the scope of the present invention.

Figures 2a and 2b show diagrammatic representations of embodiments of applications of the present invention. In particular, Figure 2a shows an operating switch 32 connected to a logic system 33. The logic system detects the requisite number of activation On' switching, and if correct, controls a MosFET 40 to allow a power supply 38 to power an electric motor 42. It will be appreciated that the motor could be other electrically powered equipment, such as a transformer, welding equipment, lighting etc. There is a clear conceptual separation between the low voltage control side 34 and the high voltage power side 36 of the system. The control side may be fitted as original equipment or may be retro fitted, such as between the switch 32 and the power side 36 The control side may include its own switch to replace or augment the original switch.

In Figure 2b, the logic system 33 controls a relay contactor 44 to activate- deactivate the equipment subject to the control of the logic system. The logic system 33 detects the correct number of switch events (and any required timing between switch events) and causes the contactor 44 to close the power circuit 38 to operate the motor (or other electrical equipment. Deactivation of electrical equipment can be by releasing the switch and/or a desired switch operation or other control.

The safety interlock system for electrical equipment can include a logic system 33 co-operating with a voltage and/or amperage sensing unit 46 in a circuit 48, for the electrical device. In addition, a logic system or device 33, such as a processor, can be provided to co-operate with and/or control such a voltage and/or amperage sensing unit 46 in a circuit 48 for electrical equipment. In any of the embodiments of the present invention, the logic system 33 can be a processor or device utilising a processor. Electronic rotation pickup, voltage and/or amperage sensing by the unit can form part of a feedback loop to the logic system. For example, the logic system can determine whether or not the equipment is on or off, speeding up, slowing down, drawing too much or too little load etc. Thus the logic system may pro indicate incorrect, unexpected or out of specification readings.

A sensor 50, preferably an electronic or optical sensor, is provided to determine whether the motor of the equipment is providing a drive rotation at a safe or expected rate for a given setting or demand. If an unexpected or unsafe rate of rotation is indicated by a signal from the sensor, the motor can be automatically or manually slowed to a safer rate of rotation or preferably stopped by the system cutting power to the motor as a safety precaution. For example, rotation may be slowed due to a faulty or worn motor bearing or due to clogging of a drill bit or pump. The sensor can detect this slowing for a given power demand and can initiate reduction or switch off power supply to the motor for safety. The sensor 24,50 signals to the logic system 1 8, 33 and, if a condition to switch off the equipment is indicated by the sensor, such as unexpected slowing of rotation of the motor armature or higher than expected current draw for a given rate of rotation, the logic system shuts off power to the motor and thereby deactivates the equipment.

Claims

CLAIMS:

1 . A safety control method to activate equipment, the method including multiple operation of an actuation device to initiate activation of the equipment.

2. A method according to claim 1 wherein the equipment is activated provided the multiple operations are carried out within a predetermined period.

3. A method according to claim 2, wherein the predetermined time period is between consecutive operations of the actuation device or the overall period between a first required operation of the actuation device and a last required operation of the actuation device to activate the equipment, or a combination of both periods.

4. A method according to claim 3 including transmitting one or more of the multiple operations of the actuation device to a receiver and thereafter actuating the equipment.

5. A method according to any one of claims 1 to 4, whereby, if a motor of the equipment slows rate of drive rotation below a safe operation level for the equipment then the safety device automatically switches off power supply to the motor.

6. A method according to claim 5, whereby an electronic or optical sensor detects the slowed rate of drive rotation.

7. A method according to claim 6, whereby the sensor includes a Hall effect sensor.

8. A method according to any one of claims 1 to 7, including multiple operation and hold of the actuation device to activate the equipment.

9. A method according to any one of claims 1 to 7, including multiple operation and release of the actuation device to activate the equipment.

10. A method according to claim 8, including release of the actuation device to stop the equipment.

1 1 . A method according to claim 9, including a further operation of the actuation device to stop the equipment.

12. A method according to any one of the preceding claims, including operation of an interlock by a control system to prevent activation of the equipment until a desired actuation sequence of the actuation device is carried out, the interlock allowing the equipment to operate once the desired sequence is carried out.

13. A method according to any one of the preceding claims, whereby, in the event of failure or cessation of main power supply to the equipment, an interlock prevents the equipment automatically starting up when power is restored until the actuation device is actuated a desired sequence incorporating the multiple operations.

14. A method according to claim 12 or 13, wherein the desired sequence includes multiple depress and hold closed the actuation device to maintain the equipment activated.

15. A method according to claim 12 or 13, wherein the desired sequence includes multiple depress and release to activate the equipment until a further depress and release of the actuation device occurs to deactivate the equipment.

16. A safety control system for power equipment, the safety control system including an actuation device and an interlock that prevents activation of the equipment by the actuation device until the actuation device has been operated at least twice.

17. A safety control system according to claim 16 including an actuation device, an interlock controlling actuation of the equipment determined by a required multiple operation of the actuation device.

18. A safety control system according to claim 17, the interlock requiring double or triple press of a switch, button, trigger or other user control before the equipment is activated.

19. A safety control system according to claim 16, 17 or 18 wherein the actuation device includes a foot and/or hand control.

20. A safety control system according to any one of claims 1 6 to 19, including drive rotation sensor for detecting a slowed rate of rotation of a motor of the equipment.

21 . A safety control system according to claim 20, the sensor including a Hall effect sensor.

22. A safety interlock system preventing cyclic ON-OFF-ON operation of an activation switching device such as relays, MosFETs, solid state relays, RCRs, contactors and/or one or more triacs.

23. A safety interlock system for electrical equipment, the safety interlock system including a logic system co-operating with a voltage and/or amperage sensing unit for the electrical device.

24. A safety interlock system for electrical equipment according to claim 23, with drive rotation sensor for detecting a slowed rate of rotation of a motor of the equipment.

25. A safety interlock system according to claim 24, the drive rotation sensor including a Hall effect sensor.