WO2013080233A1

WO2013080233A1 - Safety device applicable to chainsaws

Info

Publication number: WO2013080233A1
Application number: PCT/IT2011/000395
Authority: WO
Inventors: Paolo Cappellari; Michele Norgia
Original assignee: Redcap Technology S.R.L.
Priority date: 2011-12-01
Filing date: 2011-12-01
Publication date: 2013-06-06

Abstract

A safety kit is disclosed for cutting equipment such as electric or engine-operated chain saws. The kit comprises a least a pair of electrodes connected to an integrated-circuit assessment and driving unit, the unit being configured for acquiring a reference capacity value at least upon switching on said equipment and for issuing a safety signal when the capacity value measured between said two electrodes varies by a preset threshold with respect to said reference capacity value, the safety signal being sent to a de-activation actuator for the switching off of the equipment. The kit comprises a first proximal electrode (10a, 100a) which comprises a capacity sensor and consists of a conductive electrode bar applicable in a removable manner to a handle (1) of said equipment, a second distal electrode (10b, 100b) consisting of a conductive plate which may be fastened to a retaining bolt of a support blade (7, 107) of the cutting chain of the equipment, and the integrated-circuit assessment and driving unit which is arranged between said proximal electrode (10a, 100a) and a case (10, 100), and is provided with conductive connection cables (12, 14) to the electrodes and to said switching-off actuator, and said switching-off actuator is in the shape of a relay suited to close/open an electric supply circuit (3, P) of said equipment.

Description

SAFETY DEVICE APPLICABLE TO CHAINSAWS

DESCRIPTION

Field of the Invention

The present invention refers to a safety device applicable to cutting equipment; in particular it concerns a kit to be applied to already existing electric saws and engine-operated chain saws .

Background Art

As known, portable work equipment exists, such as chain saws and the like, which comprises moving cutting members and which exposes users to a high risk of injury. As a matter of fact, while on stationary equipment and machine tools it is relatively easy to arrange shields and/or accident prevention elements, so as to avoid any accidental contact with moving mem- bers, on portable equipment this is not feasible.

Safety devices for chain saws and similar tools have already been suggested, specifically dedicated to solving the safety problems connected with the use of such devices.

Among these, application PCT/IT2011/64290 in the name of the same Applicant suggests to use a touch sensor circuit, configured in an innovative way, to be able to detect when an operator's body part is too close to the cutting blade and hence to determine the interruption of the power supply.

This system has proved highly efficient and appreciated by operators; however, per se, it is suitable to be installed onboard newly-manufactured equipment, purposely designed to integrate the circuits, the sensors and the switches provided for generating the safety action. There is thus a significant limit, in the fact that all already manufactured electric saws and en- gine-operated chain saws and in use cannot enjoy the same level of safety reached according to the new technology proposed.

Summary of the Invention

The object of the present invention is hence that of providing a safety device which exploits the principles set forth in application PCT/IT2011/64290 , but which is applicable also to already existing cutting equipment, such as electric saws and engine-operated chain saws. Such object is achieved through a safety kit as defined, in essential terms, in the appended claim 1. The dependent claims describe preferred features of the invention.

In particular, according to a first aspect of the invention, a safety kit is provided for cutting equipment such as electric saws or engine-operated chain saws, comprising at least one pair of electrodes connected to an integrated assessment and driving circuit, the arrangement being configured to acquire a reference capacity value at least upon switching on said equipment and to issue a safety signal when the measured capacity value between said two electrodes varies by a preset threshold with respect to said reference capacity value, the safety signal being sent to an actuator for the switching off of the equip- ment, wherein

a first proximal electrode comprises a capacity sensor and consists of a small conductive bar applicable in a removable way to a handle of said equipment,

a second distal electrode consists of a conductive plate apt to be fastened to a retaining bolt of a blade supporting the cutting chain of the equipment, and

said integrated assessment and driving circuit is arranged between said proximal electrode and a case and is provided with conductive connection wires directed to the electrodes and to said switching-off actuator, and in that

said switching-off actuator is in the form of a relay suited to close/open an electric power supply circuit of said equipment .

According to a preferred aspect, the integrated assessment and driving circuit is incorporated on said proximal electrode.

According to another aspect, to the conductive bar a micro- switch is also applied, apt to enable/disable the operation of the measuring and assessment arrangement. The micro-switch is of the electro-mechanic type or of the capacitive type.

According to a further aspect, the conductive bar is integral with removable fastening means by which it is apt to be at- tached to a handle of said cutting equipment.

According to a variant, the cutting equipment is electricity power actuated by means of an electricity supply cable and the power supply means comprise a male plug and a female socket between which the power supply circuit intercepted by the relay actuator is coupled.

According to another variant, the cutting equipment is actuated by an internal combustion engine provided with a spark plug, the power supply means within the case include a power supply battery for said electrodes and said integrated assessment and driving circuit, said power supply circuit comprises a small power supply pipette connector of the spark plug intercepted by a conductive short-circuit element designed to short- circuit the pipette connector depending on the state of the re- lay actuator.

Brief Description of the Drawings

Further features and advantages of the invention will appear anyhow more evident from the following detailed description of a preferred embodiment, given purely by way of a non-limiting example and illustrated in the attached drawings, wherein:

fig. 1 is a perspective view of an electric saw and of the kit components according to the invention;

fig. 2 is a view similar to the one of fig. 1 with the kit mounted;

fig. 2A illustrates a variant of a power supply cable for the kit of fig. 2;

fig. 3 is a view similar to that of fig. 1 taken by a different perspective;

fig. 4A is a perspective view similar to the one of fig. 1 but in connection with a different embodiment of the invention applicable to an engine-operated chain saw; and

fig. 4B is a view similar to the one of fig. 4A taken from a different perspective.

Detailed Description of Preferred Embodiments

Fig. 1 illustrates an exemplifying electric saw, known per se. It comprises a handle portion 1, provided with at least one switching-on button 2, wherefrom an electric power supply cable 3 extends . On the main body of the electric saw there is installed electric motor 4 and a support bar 5, possibly provided with shielding or other mechanic safety elements 6. From the main body, in a direction opposite to handle 1, the actual cutting tool projects, consisting of a support blade 7 whereon a cutting chain 8 is slidably mounted.

According to a first embodiment of the invention, a safety kit to be employed on such electric saw is provided. The kit consists of a case 10 and of a pair of electrodes, a proximal one 10a and a distal one 10b. Case 10 comprises a male/female power connector (a female socket lib, on one side of the case, and a male plug 11a on the opposite part) and encloses an actuator in the shape of relay and any function control LEDs . It may furthermore enclose an additional measuring and assessing unit which monitors correct system operation.

Proximal electrode 10a encloses an integrated circuit of the type described in application PCT/IT2011/64290 which is here recomprised by reference. Such integrated assessment and driv- ing circuit, in substance, determines a capacity variation by means of the two electrodes 10a and 10b (according to criteria described in PCT/IT2011/64290 ) and is configured to control the relay actuator (not illustrated) whenever a safety threshold is exceeded (typically when support blade 7 has moved too close to the operator) . The electronic units are powered at low voltage, taking the electric supply directly from the supply means consisting of male/female connector 11a and lib and reducing the voltage thereof by any suitable means .

According to this embodiment, the (electro-mechanic) relay actuator is connected to male/female connector 11a, lib and is configured so as to close (when excited) or open (when deactivated) the transit of power supply from male plug 11a - intended to receive power supply from conventional electric mains, for example the 220-V home network - to female socket lib - whereto the plug of the power supply cable 3 is connected instead.

Proximal electrode 10a consists of a bar/plate suitable to be removably applied on the handle 1 of the electric saw: it guarantees an electric contact with the operator's hand and contains a micro-switch which is actuated when the operator grips the electric saw. Such bar 10a, as said, contains an electronic capacity sensor, suited to supply the signal necessary for the direct control of the relay and for the optional measurement and validation unit, which it is connected to by means of a first connection cable 12.

Bar 10a is preferably inserted in a support band 13 pro- vided with a half-portion of Velcro® tape to adhere to a corresponding half-portion of Velcro® tape integral with handle 1.

Distal electrode 10b is instead only an electric conductor, such as a metal washer, to be fastened to support blade 7 below a fastening bolt (not shown) .

As illustrated in fig. 1, distal electrode 10b has a conductive wire 14 which connects to the integrated circuit embedded in proximal electrode 10a, which in turn has the task of picking up the signal coming from distal electrode 10a, performing a specific assessment and driving the relay in case 10. Hence conductive wire 14 runs from support blade 7 and proximal electrode 10a, without continuing towards case 10. This solution is particularly preferred because it always keeps well separated the conductive cables directed to the two electrodes and avoids any capacitive wires which would distort the reading of the ca- pacity variation and hence the correct action of the safety system.

As seen, the two electrodes are fastened to handle 1 and to support blade 7, respectively, while conductive wires 12 and 14 are laid against the machine body and along the power supply ca- ble 3 , fastening them with suitable retaining means . The cable portion connecting proximal electrode 10a with case 10 may also be of the elastic-return type (12a shown in fig. 2A) , so that it is not perceived as an obstacle to the operator even though it has not been made integral with power supply cable 3.

Power supply cable 3 ends with an electric power supply plug which is coupled with the female socket lib of case 10: thereby, electric saw motor 4 receives supply from the power mains through case 10 and the supply circuit with the corresponding power ' flow can be opened (interrupted) or closed (restored) by controlling the relay actuator included in case 10.

The operation of the safety kit according to the invention provides to enable the power supply of the electric saw only in conditions of safety for the operator. The operations carried out are the following. Once the standard plug of cable 3 is connected to female socket lib, male plug 11a of case 10 is con- nected to the power mains; the supply circuit within case 10 generates a low voltage, which supplies the electrodes, the corresponding integrated assessment and driving circuit and any measurement and validation unit in case 10. The electric saw cannot be switched on because the relay mounted in series to the mains supply is normally open. The micro-switch on bar 10a is open, hence the sensor embedded in the bar is not supplied.

When the operator grips the saw, pushing electrode bar 10a on the handle, he closes the micro-switch, which enables the electric supply to the sensor (on proximal electrode 10a) . At this moment the integrated sensor circuit initialises and calculates the initial capacity between cutting blade 7 (where the distal electrode is located) and the electrode bar on the handle, already connected to the operator since he is gripping it, according to operating modes illustrated in application PCT/IT2011/64290. In practice, upon switching on the sensor included in electrode 10a, said sensor supplies a signal to the integrated circuit for determining the initial capacity and hence enables the control signal for closing the relay within case 10: thereby the supply means deliver current to motor 4 and the electric saw can now be operated.

When the operator pushes the ON button of the electric saw, conventionally the power supply circuit to the motor closes, which will be interrupted only in case of relay opening. During the standard use of the electric saw, the relay remains always closed (provided the sensor in electrode 10a is duly powered and connected), since the hand's grip on the handle keeps the micro- switch closed and hence the sensor powered, so that no variations to the standard use of the tool occur per se. In case instead of a sudden proximity of the blade to the operator (= detection of a hazardous situation) , through a measurement of the increase of measured capacity between the two electrodes (blade and gripped electrode bar) - according to the teaching of PCT/IT2011/64290 - the integrated circuit generates a control signal which is transmitted to the relay to cause the opening thereof, with the resulting immediate turning off of the elec- trie saw.

Figs. 4A and 4B show a different embodiment of the invention, applied to a chain saw, i.e. a cutting apparatus actuated by an internal-combustion engine. With respect to the apparatus shown in fig. 1, an engine-operated chain saw is substantially identical, except that the engine is not electric and there is hence no supply cable, nor a corresponding supply plug.

The device still comprises, in a manner fully equivalent to the first embodiment, a housing case 100 - comprising a relay actuator - wherefrom two connection cables extend directed to a first proximal electrode 100a (provided with the micro-switch and with the sensor) and a distal electrode 100b to be electrically coupled with a support blade 107 of the cutting chain.

According to this embodiment, case 100 contains also a rechargeable battery with a corresponding charge LED (not shown) . The case is configured so as to be able to be applied to the outside of the cutting equipment, for example on the fuel tank. From case 100 a control cable 103 furthermore departs, in the shape of two electric conductive cables, provided with a conductive terminal suited to be engaged between the spark plug of the internal-combustion engine and a pipette connector P for the electric supply of the spark plug. Control cable 103 has the function of establishing, upon the closing of the relay actuator (which is electrically mounted in parallel with the above-said conductive terminal) , a short-circuit which withdraws from pi- pette P the current otherwise directed to the spark plug. In the following the operation of this embodiment is described. The electrodes, the corresponding integrated assessment and driving circuit and any additional measuring and validation unit, are powered by the rechargeable battery also with the chain saw turned off.

Therefore, by gripping the handle the microswitch included in proximal electrode 100a is activated and the integrated circuit is activated, so that the initial capacity may be determined. Parallel to the spark plug, control conductive wire 103 is arranged, at the end of which the relay actuator is provided which is normally open.

In this condition the spark plug receives electric supply in a conventional way and it is possible to start the chain saw, for example by rope pull .

In case a dangerous situation is detected (due to the capacity variation between the two electrodes) , the integrated circuit in proximal electrode 100a intervenes by driving the closing of the relay actuator: this causes a short-circuit of the spark plug and the internal-combustion engine of the chain saw hence turns off.

As can be evinced from the above-reported description, with the kit according to the invention it is possible to easily transform a conventional electric saw or an engine-operated chain saw, so as to make them extremely safe for the operator. The application of the kit according to the invention does not require particular skills by the user, nor does it require to act in a structural way on the already existing components .

However, it is understood that the invention is not limited to the particular configurations described above and illus- trated, which make up only non-limiting examples of the scope of the invention, but that a number of variants are possible, all within the reach of a person skilled in the field, without departing from the scope of the invention.

For example, although not explicitly shown, the electric connection cables coming out from the housing cases may be of the rewinding type. That is, a rewinding system of the cables within the housing case may be provided, so that the cable which extends outside the electric saw or engine-operated chain saw has an essential minimum length regardless of the tool model which the kit according to the invention must be applied to.

Moreover, as mentioned above, a measuring and validation unit (which may be accomplished with a microcontroller) may be provided, which provides for monitoring of the entire system. Such unit might replace the electro-mechanic turning-on micro- switch, through a capacitive contact measurement. In such case, instead of pushing the micro-switch, the gripping action of the chain saw is revealed through a capacitive measure referred to the ground, performed on proximal electrode 10a or 100a. Moreover, the measuring and validation unit may initially verify that the detected capacities are correct, hence that the connections are not interrupted, as well as verifying the continuous operation of the integrated circuit, through known watchdog techniques .

Claims

1. Safety kit for cutting equipment such as electric or engine-operated chain saws, comprising at least a pair of electrodes connected to an integrated-circuit assessment and driving unit, the unit being configured for acquiring a reference capacity value at least upon turning on said equipment and to deliver a safety signal when the measured capacity value between said two electrodes varies by a preset threshold with respect to said reference capacity value, the safety signal being sent to a de- activation actuator of the equipment, characterised in that

a first proximal electrode (10a, 100a) comprises a capacity sensor and consists of a conductive electrode bar applicable in a removable manner to a handle (1) of said equipment,

a second distal electrode (10b, 100b) consists of a conduc- tive plate which may be fastened to a retaining bolt of a support blade (7, 107) of the cutting chain of the equipment, and said integrated-circuit assessment and driving unit is arranged between said proximal electrode (10a, 100a) and a case (10, 100), and is provided with conductive connection cables (12, 14) to the electrodes and to said deactivation actuator, and in that

said deactivation actuator is in the shape of a relay suited to close/open an electric supply circuit (3, P) of said equipment .

2. Safety kit as claimed in claim 1, wherein said integrated-circuit assessment and driving unit is incorporated on said proximal electrode (10a, 100a) .

3. Safety kit as claimed in claim 1 or 2, wherein to said conductive electrode bar (10a, 100a) there is applied also a mi- cro-switch, apt to enable/disable the operation of said integrated-circuit assessment and driving unit.

4. Safety kit as claimed in claim 3, wherein said micro- switch is of the capacitive type.

5. Safety kit as claimed in any one of the preceding claims, wherein said conductive electrode bar (10a, 100a) is integral with removable fastening means (13) with which it is apt to be joined to a handle (1) of said cutting equipment.

6. Safety kit as claimed in any one of claims 1 to 5, wherein said cutting equipment is powered by electric energy through a supply cable (3) and wherein said supply means comprise a male plug (11a) and a female socket (lib) between which there is coupled said supply circuit intercepted by said relay actuator .

7. Safety kit as claimed in any one of claims 1 to 5, wherein

said cutting equipment is actuated with an internal- combustion engine provided with spark plug,

said supply means within the case (100) include a supply battery for said electrodes (100a, 100b) and said integrated- circuit assessment and driving unit,

said supply circuit comprises a supply pipette connector (P) of said spark plug intercepted by a conductive short-circuit element (103) arranged to short-circuit said pipette connector (P) depending on the state of said relay actuator.