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Title:
SAFETY ARRANGEMENT IN A FASTENER DRIVING TOOL
Document Type and Number:
WIPO Patent Application WO/1999/042253
Kind Code:
A1
Abstract:
The invention relates to a device in fastener driving tools (1) comprising means (6, 7) for driving a fastener (2; 2') through a tool point (4) and in the direction towards a surface (12), a trigger device (11) for activation of said means (6, 7), and a safety arrangement (13, 15, 16, 17, 18) for deactivation of said means (6, 7) in the event of said tool point (4) not being positioned within a predetermined distance from said surface (12). The invention is characterized in that the safety arrangement (13, 15, 16, 17, 18) comprises a transmitting unit (16) for generation of a signal towards the surface (12), a receiving unit (17) for detection of a signal that is reflected from the surface (12), and an activation unit (18) which is adapted for said deactivation in the event of a measure of said reflected signal being below a predetermined value. By means of the invention, an improved handheld fastener driving tool is provided for a non-contact detection of whether the tool is held in close vicinity of the surface.

Inventors:
Dagman, Bengt (Vallgatan 23 Hjo, S-544 30, SE)
Application Number:
PCT/SE1999/000131
Publication Date:
August 26, 1999
Filing Date:
February 02, 1999
Export Citation:
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Assignee:
JOSEF KIHLBERG AB (P.O. Box 126 Hjo, S-544 22, SE)
Dagman, Bengt (Vallgatan 23 Hjo, S-544 30, SE)
International Classes:
B25C1/00; B25C5/06; B25C5/13; (IPC1-7): B25C1/00; B25C5/00; B27F7/02; B27F7/17
Foreign References:
US5229829A1993-07-20
US5406441A1995-04-11
EP0747176A11996-12-11
US4554834A1985-11-26
Attorney, Agent or Firm:
Graudums, Valdis (Albihns Patentbyrå Göteborg AB P.O. Box 142 Göteborg, S-401 22, SE)
Andersson, Per (Albihns Patentbyrå Göteborg AB P.O. Box 142 Göteborg, S-401 22, SE)
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Claims:
CLAIMS
1. Device in fastener driving tools (1) comprising means (6,7) for driving a fastener (2; 2') through a tool point (4) and in the direction towards a surface (12), a trigger device (11) for activation of said means (6,7), and a safety arrangement (13,15,16,17,18) for deactivation of said means (6,7) in the event of said tool point (4) not being positioned within a predetermined distance from said surface (12), c h a r a c t e r i z e d i n that the safety arrangement (13,15,16,17,18) comprises a transmitting unit (16) for generation of a signal towards the surface (12), a receiving unit (17) for detection of a signal that is reflected from the surface (12), and an activation unit (18) which is adapted for said deactivation in the event of a measure of said reflected signal being below a predetermined value.
2. Device according to claim 1, c h a r a c t e r i z e d i n that said transmitting unit (16) is constituted by a device for generation of a signal in the form of a light signal (14), and that said receiving unit (17) is constituted by a detection circuit for determination of a measure of said reflected signal.
3. Device according to claim 2, c h a r a c t e r i z e d i n that said light signal (14) is directed in the direction towards said surface (12) through an optical fibre (13) which is provided in the point (4) of the tool (1).
4. Device according to claim 1, c h a r a c t e r i z e d i n that said transmitting unit is constituted by a device for generation of a signal in the form of an ultrasound signal, and that said receiving unit is constituted by a detection circuit for ultrasound, for determination of a measure of said reflected signal.
5. Device according to claim 1, c h a r a c t e r i z e d i n that said transmitting unit is constituted by a device for feeding out a signal in the form of an air stream and that said receiving unit is constituted by a detection device for an air stream which is reflected from said surface (12).
6. Device in fastener driving tools (1) comprising means (6,7) for driving a fastener (2; 2') through a tool point (4) and in the direction towards a surface (12), a trigger device (11) for activation of said means (6,7), and a safety arrangement for deactivation of said means (6,7) in the event of said tool point (4) being positioned within a predetermined distance from said surface, c h a r a c t e r i z e d i n that the safety arrangement comprises a receiving unit for receiving a signal constituting a measure of the heat radiation from the surface, and an activation unit which is adapted for said deactivation in the event of the measure of said signal exceeding a predetermined value.
7. Device according to claim 6, c h a r a c t e r i z e d i n that said receiver is adapted in such manner that said limit value corresponds to the heat radiation from a part of a human body which is situated in close vicinity of said tool (1).
Description:
Safety Arrangement in a Fastener Driving Tool.

TECHNICALFIELD The present invention relates to a device in a fastener driving tool, according to the preamble of appended claim 1. The invention is in particular intended for use in connection with a handheld tool which is intended for driving fasteners into a surface.

BACKGROUND ART It is previously known that handheld tools can be utilized for driving various types of fasteners, for example staples, nails and the like. In connection with, for exampte, building works, compressed-air driven fastener driving tools are often utilized for driving staples, e. g. for joining of building units in the form of slabs of wood.

A previously known handheld tool of the above-mentioned type comprises a housing which is intended to be held with one hand by an operator. The tool comprises a magazine for a number of staples and a compressed-air driven, movable piston which, when being activated, is adapted to exert a substantial- force against a staple in the magazine. In this manner, the staple can be ejected out of the tool and be driven into the surface in question. For activation of the movable piston, the tool comprises a connection to a compressed-air system as well as a trigger which can be actuated manually.

For safety reasons, it is of utmost importance that no unintentional activation of the above-mentioned handheld tool occurs in such manner that a staple is ejected in the direction of, for example, a human being, which in that case could result in personal injuries. To this end, in accordance with recognized industrial standards, there is a demand for providing the tool with a safety device which is utilized in order to prevent activation of the tool in the event of its point (at which the staples are fed out) not being in close contact with the surface in question.

Therefore, in accordance with known technique, there exist handheld fastener driving tools which are provided with a safety device in the form of a particular safety yoke which is arranged in connection with the point of the tool. More precisely, the safety yoke is spring-loaded and arranged in such manner that it can be displaced in relation to the point of the tool, essentially along the same direction as the feeding out direction of the staples. The safety yoke is also arranged in such manner that it protrudes a short distance outside the point of the tool. When the operator is going to use the tool, the tool is at first positioned so that the safety yoke is in contact with the surface in question. Then, as a consequence of the safety yoke being spring- suspended, the operator must press the tool downwards against the surface with a certain predetermined contact force, by means of which the safety yoke is displaced in relation to the tool point while the spring force is exceeded. When the safety yoke has been displaced a predetermined distance, a particular activation mechanism in the tool will be actuated so that compressed air is allowed to be supplied for actuation of the piston. If the operator in this stage pulls the trigger, the piston will be actuated so that a staple is ejected out of the tool.

If the tool is lifted up from the surface, the activation mechanism will prevent the above-mentioned piston from being activated, even if the trigger is actuated. This, in turn, results in that no staple can be ejected out of the tool.

However, although the above-mentioned known system in principle functions satisfactorily, it suffers from certain drawbacks. On the one hand, the safety yoke constitutes a mechanical construction which comprises several movable parts which are exposed to wear and require a costly assembly process. Also, there is a risk that the tool breaks down as a result of the fact that the safety yoke not always can be depressed when the operator quickly sweeps the tool along the surface while staples are being fed out. This especially happens when the tool is used on an irregular surface, and may, if it comes

to the worst, resutt in that the tool breaks down. Furthermore, it is relatively easy to cancel the function of the safety yoke by locking it in a position in which the tool always can be activated for feeding out staples. Finally, there is a risk of the safety yoke getting stuck in possible edges and irregularities sticking up from the surface in question.

DISCLOSURE OF INVENTION The object of the present invention is to provide an improved handheld fastener driving tool comprising a safety device which is adapted to prevent an undesired activation of the function of the tool, by means of which the above-mentioned problems are solved.

This object is achieved by means of a device, the characterizing features of which will be apparent from appended claim 1.

The invention is intended for fastener driving tools comprising means for driving a fastener through a point of a tool and in the direction towards a surface, a trigger device for activation of said means, and a safety arrangement for deactivation of said means in the event of said tool point not being positioned within a predetermined distance from said surface. The invention is characterized in that the safety arrangement comprises a transmitting unit for generation of a signal towards the surface, a receiving unit for detection of a signal that is reflected from the surface, and an activation unit which is adapted for said deactivation in the event of a measure of said reflected signal being below a predetermined value.

By means of the invention, a completely non-contact detection is provided for determination of whether the tool is positioned at a predetermined distance to the surface or not, i. e. a detection of whether the tool shall be allowed to be able to be activated or not. Furthermore, the safety device according to the invention is not exposed to wear, since it does not contain any movable parts.

In this connection, the term"fastener driving tool"refers to a tool which is intended for feeding elements and for driving said elements into a particular surface.

In this regard, elements in the form of staples, nails etc. can be utilized in this tool. Furthermore, the term"fastener driving tool"shall be considered to refer to tools which are operated by compressed air, an electric motor or by other suitable means. Furthermore, said term refers in principle to handheld tools as well as to non-handheld tools.

Advantageous embodiments of the invention will be apparent from the appended dependent claims.

BRIEF DESCRIPTION OF DRAWINGS The invention will be further described in the following with reference to a preferred embodiment and to the annexed drawings, in which Fig. 1 shows a slightly simplified and partly broken side view of a fastener driving tool according to the invention, Fig. 2 shows a slightly enlarged, detailed front view of the point of the fastener driving tool according to Fig. 1, and Fig. 3 shows a simplified principle diagram of a transmitting and receiving system which can be utilized in connection with the invention.

PREFERREDEMBODIMENT Fig. 1 shows a slightly simplified and partly broken side view of a fastener driving tool 1 in which the present invention can be utilized. According to a preferred embodiment, the tool 1 is handheld and intended for driving

fasteners 2 in the form of staples, i. e. essentially yoke-shaped elements which preferably are constructed by bending of rolled steel wire. The tool 1 is, for example, suitable to be utilized in connection with building works, e. g. for joining of building units in the form of slabs of wood.

The tool 1 comprises a magazine 3 for a number of staples 2 which preferably are joined together in advance by means of gluing, so that they form a longitudinal packet. The magazine 3 preferably comprises a (not shown) feed mechanism having a spring member for actuation of the staple packet in the direction towards a nose or a point 4 of the tool 1 (i. e. leftwards according to Fig. 1). Furthermore, the tool 1 is arranged in such manner that the staple which is situated farthest out in the staple packet (i. e. the staple which is situated farthest to the left according to Fig. 1) can be ejected out of the point 4 by means of actuation of a driving member 5 which is movably arranged transversely to the staple packet. The driving member 5 is in turn connected with a movable piston 6 which is situated above the clriving member 5. The piston 6 is adapted for a reciprocating motion in a cylinder 7.

In a manner which is per se previously known, the piston 6, and by that the driving member 5 as well, is adapted to be actuated for displacement by means of compressed air which is supplied by connection of a compressed- air line 8 to a connecting nipple 9 on the tool 1.

When the compressed-air line 8 has been connected to the nipple 9, the tool 1 can be activated by means of an operator 10 pulling a trigger 11 which can be actuated manually. This results in that compressed air is supplied through the tool 1 and is caused to actuate the above-mentioned piston 6, which in turn presses the driving member 5 downwards with a substantial force. The driving member 5, in turn, ejects the staple 2 that is situated farthest out in the staple packet in the direction towards a surface 12, which in the drawing is represented by two plate-or sheet-formed elements which are intended to be joined. The reference numeral 2'in Fig. 1 refers in principle to a staple

which is on its way out from the tool point 4 in the direction towards the surface 12.

Fig. 2 shows a slightly enlarged cross-sectional front view of a point 4 of the tool according to the invention. A staple 2 and the driving member 5 are also apparent from the drawing, wherein the staple 2 is shown in a position in which it is situated before it is ejected out of the point 4 in the direction towards the surface 12 in question.

In accordance with the invention, the point 4 is provided with a transmitting device in the form of a first optical fibre 13 having its extension along the point 4. The optical fibre 13 comprises an end section 13a which is situated at the bottom edge of the point 4 and is angularly arranged with a predetermined direction towards the surface 12. In this manner, the optical fibre 13 is adapted to direct a ray of light 14 with an angle a towards the<BR> surface 12, wherein the angle a depends upon the orientation of the end section 13a and the inclination of the surface 12.

A certain part of the light in the ray of light 14 which incides against the surface 12 will be reflected against the surface 12 and be returned in the direction towards the point 4. Furthermore, the point 4 is also provided with a receiving device in the form of a second optical fibre 15. The second fibre 15 has a second end section 15a which preferably ends at the bottom edge of the point 4, at which edge the staple 2 is fed out. The second end section 15a is angularly arranged with a predetermined direction towards the surface 12. As is apparent from Fig. 2, the two end sections 13a, 15a are preferably arranged in such manner that the directions, along which the end sections 13a, 15 have their extension, intersect each other essentially at right angles. As will be described in more detail below, the second fibre 15 is connected to measuring equipment for determination of a measure of the amount of light that has been taken up following the reflection in the surface 12.

The amount of light that after the reflection of the ray of light 14 is taken up and directed in through the second end section 15a depends primarily upon the distance d between the bottom edge of the point 4, at which the respective end section of the optical fibres 13,15 is positioned, and the angle a between the incident ray of light 14 and the surface 12. The reflected amount of light also depends upon other factors, such as, for example, the reflectivity of the surface 12.

The invention is based upon the fact that the receiving optical fibre 15 must receive a certain smallest amount of light in order for the tool 1 to be activated for feeding out a staple 2. This smallest amount of light then constitutes an indication of the fact that the point 4 of the tool is held closely enough to the surface 12. In this manner, an unintentional activation of the tool can be prevented in the event of the point 4 not being held closely enough to the surface 12.

Fig. 3 shows schematically how the two optical fibres 13,15 are connected in an arrangement for detection of whether the tool is held within a predetermined distance from the surface 12 or not. The arrangement comprises a transmitting unit 16 which is adapted for generating a light signal which is fed out through the first optical fibre 13 and is caused to incide against the surface 12. According to what has been described above, a certain part of the emitted amount of light will reach the second optical fibre 15 in the form of reflected radiation. The received amount of light is fed to a receiving unit 17 which is adapted for determination of a measure of this amount of light and for determination of whether this measure exceeds a predetermined limit value which corresponds to the tool 1 being held closely enough to the surface 12, i. e. within a certain distance from the surface 12 which corresponds to the fact that there is no risk of an ejected staple constituting a risk of causing injuries on, for example, the operator. If that is the case, a signal is fed to an activation unit 18, which is arranged in

connection with the above-mentioned trigger 11 (cf. Fig. 1), wherein an activation of the tool is allowed. In this condition, a pulling of the trigger 11 will result in that a staple 2 is ejected out of the tool 1.

If the receiving unit 17 instead estimates that the value of the received amount of light is below the above-mentioned limit value, this is an indication of the tool 1 not being held closely enough to the surface 12, i. e. that the orifice of the point 4 through which the staples are fed out is not close enough to the surface 12. In this case, a signal is fed to the activation unit 18 which prevents the tool from being activated even if the trigger 11 is pulled. Such a prevention of the activation can be accomplished in a number of different ways. One example is to provide the trigger 11 with a mechanical blocking mechanism (not shown), wherein the activation unit 18 is adapted to actuate a movable yoke or the like to adopt a predetermined position in which the trigger 11 can not be pulled. In this condition, which thus corresponds to the tool 1 not being held closely enough to the surface 12, the yoke will prevent the tool 1 from being activated and staples from being fed out. An additional method of preventing activation of the tool 1 is to construct its compressed-air system in such manner that a certain signal from the activation unit 18 initiates an evacuation of the compressed air which is intended to be supplied to the piston 6 in order to actuate this in the direction towards a staple.

The safety arrangement which comprises the fibres 13,15, the transmitting unit 16, the receiving unit 17 and the activation unit 18 is suitably built into the tool 1 in such manner that the fibres 13,15 are built into the point of the tool and the rest of the components are built into some other suitable location in the tool 1. Preferably, the transmitting unit 16 and the receiving unit 17 are connected to a (not shown) voltage source, which can be constituted by a battery which is built into the tool or by a separate voltage supply, which in that case can be connected via an (not shown) electric wire which follows the compressed-air line 8 (cf. Fig. 1).

According to an alternative embodiment of the invention, which is not shown in the drawings, the transmitting unit can be constituted by a device for feeding out a signal in the form of an air stream through a nozzle which is situated at the point of the tool. In this case, the point is also provided with a receiving unit for detection of air which can be directed in through several small holes which have been arranged in the point of the tool. If the amount of air which has been reflected against the surface is directed in through a large number of these holes, this will be interpreted as if the tool is held close to the surface. This, in turn, results in that the receiving unit and the activation unit put the tool into an active state which allows a staple to be ejected out of the tool when the trigger is pulled.

According to an additional possible embodiment, the transmitting unit is constituted by an ultrasound generator which is adapted to transmit an ultrasound signal from the tool and in the direction towards the surface. A certain part of the transmitted ultrasound signal will then be reflected against the surface and back to the tool. Furthermore, according to this embodiment, the tool point comprises a receiver for ultrasound which is adapted to deactivate the tool in the event of a too weak reflected signal being received by the receiver.

According to an additional alternative embodiment, the tool comprises a receiving unit in the form of a sensor for detection of heat radiation from the surface in question. In this manner, a measure of the heat radiation that is received from the surface can be determined. Depending upon this measure, the function of the tool can be activated and deactivated, respectively. This later embodiment is particularly suitable to be utilized for detection of whether the tool is held close to a part of a human body or not, which of course constitutes a risk of injury in the event of the tool being activated unintentionally. If the measure of the received signal regarding the heat radiation from the surface in question exceeds a predetermined level value,

this is interpreted as if the tool is positioned too close to a part of a human body. This results in that the function of the tool is deactivated by means of an activation unit, by analogy with what has been described above.

According to this later embodiment, the tool does not comprise any separate transmitting unit.

The invention is not limited to the embodiments which are described above and shown in the drawings, but may be varied within the scope of the appended claims. For example, the invention can be utilized in tools which are intended for feeding and driving staples, nails, bushings, pins and other objects in the direction towards a surface. Furthermore, the invention is in principle not limited to handheld tools, but may also be utilized for non- handheld tools.

Furthermore, it is not necessary for the transmitting device and the receiving device, respectively, to be situated at the point of the tool, but they may be situated in other suitable positions in or in connection with the tool. Also, the end sections 13a, 15a can be arranged having other extensions than what is apparent from Fig. 2.

Furthermore, the activation unit 18 can in principle be constructed in such manner that the operator him-/herself can set a desired limit value (for example regarding the light signal which is fed through the receiving optical fibre 15) at which the tool is to be deactivated. This may, for example, be accomplished by means of a potentiometer, by means of which the limit value is adjusted, preferably within a predetermined interval. This may come into question when the tool is intended to be used in connection with various types of surfaces disclosing various degrees of reflectivity.

Finally, the embodiment comprising a receiving unit for heat radiation can be integrated in a tool together with a device according to any of the other above-mentioned embodiments.