A rivet and a tool for mounting of such a rivet BACKGROUND OF THE INVENTION AND PRIOR ART The invention relates to a rivet and a tool for mounting of such a rivet. The rivet is arranged to be provided in a hole for joining at least a first plate and a second plate in a plate joint, which com- prises a first and a second external surface, wherein the rivet comprises a first portion, which comprises a first stop surface arranged to get into contact with a first of said external surfaces in an area around the opening of the hole, a second portion, which, in a mounted state, comprises a second stop surface ar- ranged to get into contact with the second external surface in an area around the opening of the hole, a draw portion, which ex- tends through the first portion and the second portion, and an end portion, which forms a terminating end of the second por- tion, wherein the end portion is arranged to, during mounting of the rivet, be supplied with a drawing force, via the draw portion, such that a deformation of the second portion is obtained.

Such rivets are usually called blind rivets or pop rivets and are used, for example, when joining ventilation tubes. The joining is performed in two steps. In the first step, a mechanic drills holes through the ventilation tubes at the places where the rivets are to be applied. Usually, a drilling machine is here used. Thereaf- ter, the rivets are inserted into the holes and the mechanic uses blind riveting tongs or the like in order to supply a drawing force to a draw portion (the splint) of the rivet such that the rivet head is plastically deformed on the inside of the tube joint. Thereby, the rivet head provides a stop surface on the inside of the tube joint such that the plates are held together. The draw portion breaks when a determined tensile stress is achieved in an indi- cation of fracture. Consequently, the mechanic has to use two different tools in order to produce the tube joint. When blind riv- eting tongs are used, the mechanic also has to supply a large manual force in order to expand the rivet heads. Ventilation

tubes are usually joined at a roof level, which results in an un- comfortable working position for the mechanic. The work of joining ventilation tubes therefore becomes both laborious and time consuming.

Self-drilling screws exist in different kinds on the market. With self-drilling screws, two ventilation tubes may be joined in one working moment. However, the method is insufficient since no expansion of the screw takes place on the inside of the joint.

Thereby, no stop surface is obtained on the inside of the joint which guarantees that the plates are kept together. Furthermore, sharp points are formed on the inside of the joints. Dirt and dust are collected at such points. The points also constitute a risk of injury for chimney-sweepers and may destroy their tools.

SUMMARY OF THE INVENTION The object of the present invention is to provide a rivet which makes it possible to join two plates in a quick and simple man- ner.

The above-mentioned object is achieved in that the end portion comprises a cutting surface which enables the making of said hole through the first plate and the second plate when the end portion is supplied with a rotary motion. Consequently, the end portion of the second part is provided with a suitably shaped cutting surface, which drills a hole through the plates when the rivet is supplied with a rotary motion and is pressed against the plates. Consequently, with such a rivet one needs not to use a separate drill for drilling holes in the plates before the rivets may be introduced into the holes. In connection with the holes having been drilled, the rivet is also in place and may thereby undergo the required plastic expansion. The application of such rivets can thereby be performed substantially quicker and to a lower cost than the application of conventional blind rivets and pop rivets. The quality of a joint with such a rivet is still high to give

the end portion of the rivet a suitably shaped cutting surface re- quires no substantially technical manufacturing changes and therefore, the rivet may be manufactured to substantially the same cost as a conventional blind rivet.

The object of the invention also is to provide a tool for mounting of such a rivet. The tool comprises first means for receiving and holding the draw portion of the rivet, second means for supply- ing a rotary motion to the end portion of the rivet for making a hole with the cutting surface through at least a first and a sec- ond plate during a simultaneous introduction of the rivet into the hole and third means for supplying a drawing force, via the draw portion, to the end portion of the rivet for allowing deformation of the second portion of the rivet. By such first means, the draw portion of the rivet is kept in a firm grip at the same time as said second means supplies a rotary motion to the rivet. During the initial riveting work, the tool is positioned such that the cutting surface of the rivet obtains contact with an external surface of a first of two abutting plates, whereupon the rotary cutting surface of the rivet is drilled through the plates. The rivet is introduced through the hole until the stop surface of the first portion obtains contact with the plate surface around the inlet of the hole. In this position, the rivet is in the intended position for being expanded.

Hereby, said third means is activated, which supplies a drawing force, via the draw portion, to the end portion of the rivet such that it is plastically deformed on the inside of the plate joint. The draw portion breaks when a determined strain is obtained in a point of fracture.

According to a preferred embodiment of the tool, said first means comprises a chuck for receiving and holding the draw portion of the rivet when the rivet is supplied with a rotary mo- tion. Chucks are used in machine elements such as turnings and drilling machines in order to hold firmly rotary tools and work pieces. A chuck makes it possible to hold rivets of different di- mensions. Advantageously, said chuck comprises a plurality of

rolls, which are arranged to hold the draw portion of the rivet when the chuck is rotated in a first direction whereas the rolls are arranged to release the grip of the draw portion of the rivet when the chuck is stationary or is rotated in an opposite direc- tion. Consequently, such a chuck only grips the rivet when it is rotated in the first direction and is drilled through the plates.

Hereby, the chuck may comprise suitably shaped cam surfaces which guide the rolls radially inwards when the rivet is rotated in the first direction. By suitably shaped cam surfaces and a suffi- cient number of revolutions, the draw portion of the rivet is held firmly by the rolls with a clamping force which allows for said drilling operation.

According to another preferred embodiment, said first means comprises two jaw-shaped grip members, which are arranged to grip the draw portion of the rivet when said drawing force is to be supplied to the draw portion. By such jaw-shaped grip mem- bers, a sufficient clamping force guaranteed to be obtained for holding the draw portion during the supply of a required drawing force. The grip members may have a construction such that they are pressed together when the grip members are supplied with a draw motion. Said first means here comprises a chuck for grip- ping the draw portion during the drilling operation and grip members which grip the draw portion during the plastic expan- sion of the second portion of the rivet. Alternatively, said first means may comprise a common member which grips the draw portion during both the drilling operation and during the plastic deformation of the second portion of the rivet.

According to another preferred embodiment of the invention, said second means comprises a motor, which, via a transmis- sion, supplies a rotary motion to the chuck. An electric motor may, for example, here be used, which, via the transmission, supplies a rotary motion with a number of revolutions which is suitable for drilling. Such a speed may suitably be in the range of 1000-2000 rpm. Advantageously, the motor is a compressed

air operated vane motor. Such motors are suitable to use in dif- ferent kinds of motor operated tools. Usually, a vane motor has a high number of revolutions and comprises therefore with ad- vantage an integrated planetary gearing. Thereby, the outlet number of revolutions of the motor may be reduced. Preferably, the motions of the motor is transmitted to the chuck via a trans- mission comprising a belt. With a belt-transmission, a relatively silent operation of the chuck is obtained. The motions of the motor may be transmitted, via a first gear-wheel, to the belt, which in its turn drives a second gear-wheel connected to a shaft of the chuck. The second gear-wheel may here have more teeth than the first gear-wheel. Thereby, the number of revolu- tions of the motor may be reduced further and down to a suit- able number of revolutions for drilling.

According to a preferred embodiment of the present invention, said third means comprises an articulated lever mechanism, which is arranged to retract the two grip members into a sur- rounding casing such that the two grip members grip the draw portion of the rivet. With such a mechanism, a suitable clamping force is guaranteed to be provided for gripping the draw portion when said drawing force is supplied in order to expand the sec- ond portion plastically. Advantageously, said third means com- prises a compressed air operated cylinder which is arranged to supply said drawing force. Hereby, compressed air may be used both for drilling the rivet through the plates and for deforming the second portion.

According to a preferred embodiment of the present invention, the tool comprises a first switch, which controls the compressed air to the vane motor, and a second switch, which controls the compressed air to the compressed air operated cylinder. Such switches may be two separate button members having a suitable position on the tool. The button members may be connected to a suitable valve in order to connect a compressed air source al- ternatively to the vane motor and to the cylinder. Alternatively,

only one switch may be used which allows an operation of both the vane motor for the drilling process and the pressure cylinder for the expansion of the rivet.

The object of the invention is also to provide a method for appli- cation of such a rivet. The method comprises the steps of sup- plying a rotary motion to the end portion of the rivet for making a hole with the cutting surface through a first and a second plate during a simultaneous introduction of the rivet into the hole and of supplying a drawing force, via the draw portion, to the end portion of the rivet such that a deformation is allowed of the second portion of the rivet. Since no holes need to be drilled in advance, such a rivet may be applied with a considerably more simple method than a conventional blind rivet.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, a preferred embodiment of the invention is de- scribed as an example with reference to the attached drawings, in which: Fig. 1a shows a rivet according to the present invention in a non-mounted state, Fig. 1b shows a rivet according to the present invention in a mounted state, Fig. 2 shows a tool for mounting of the rivet according to the above, Fig. 3 shows a sectional-view of the tool in the plane A-A in Fig. 2 and Fig. 4 shows an exploded view of a number of included components of a tool according to the present inven- tion.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Fig 1a shows a rivet in a non-mounted state and Fig 1b shows the rivet in a mounted state. The rivet is arranged to be applied in a hole through a first plate 1 and a second plate 2 in order to join the plates 1,2 in a plate joint comprising a first external surface 1'and a second external surface 2'. The rivet comprises a first portion 3, a second portion 4 and a draw portion 5. The first portion 3 has a stop surface 3', which is arranged to get into contact with the first external surface 1'of the plate joint. The second portion 4 is arranged to extend through the hole in a mounted state and, after that it has been plastically deformed, form a second stop surface 4'against the second external sur- face 2'on the opposite side of the plate joint. The draw portion 5 extends through both the first portion 3 and the second portion 4 to an end portion 6 which forms a terminating end of the second portion 4.

The difference between the present rivet and a conventional blind rivet, it is that the end portion 6 comprises a cutting sur- face 6'which allows for making of said hole through the first plate 1 and the second plate 2 when the rivet is supplied with a rotary motion. Consequently, it is possible to drill through the plates 1,2 by means of the rivet when it is supplied with a rotary motion. Consequently, when such rivets are applied, no holes drilled in advance are required. After that the cutting surface 6' of the rivet has drilled a hole through the plates 1,2, the motion of the rivet through the drilled hole is carried on until the stop surface 3'of the first portion gets into contact with the first ex- ternal surface 1'of the plate joint. In this position, a drawing force is supplied, via the draw portion 5, such that the second portion 4 is deformed plastically and forms a stop surface 4' against the second external surface 2'. When the second portion achieves a sufficient expansion around the hole, a strain is ob- tained in an indication of fracture in the draw portion 5, which

results in that the draw portion 5 comes loose. The rivet is now applied.

Fig 2 shows a tool for mounting of a rivet according to the above. The tool comprises a chuck 7 with a holder 8 for receiv- ing and holding the draw portion 5 of the rivet when the rivet is drilled through the plates 1,2. A vane motor 9 is arranged to supply a rotary motion to the chuck 7 via a transmission. The vane motor 9 comprises an integrated planetary gearing 10 in order to reduce the outlet number of revolutions of the vane motor 9. A shaft 11 extends from the planetary gearing 10 to a first gear-wheel 12. The gear-wheel 12 is, via a belt 13, con- nected to a second gear-wheel 14 fixedly connected to the chuck 7. The first gear-wheel 12 has a fewer number of teeth than the second gear-wheel 14. Thereby, the transmitted num- ber of revolutions is further reduced such that the chuck 7 ob- tains a number of revolutions suitable for drilling. A compressed air source is, via a compressed air line 15, connected to the tool. The tool comprises a valve 16 with which the compressed air line 15 is connectable to the vane motor 9. Compressed air is supplied to the vane motor 9, via the valve 16 and a conduit 17, when a mechanic activates a first button member 18 of the tool.

The tool also comprises a second button member 19, which when activated, is arranged to control the valve 16 such that the compressed air line 15 instead is connected to a compressed air operated cylinder 20 via a conduit 21. The cylinder comprises a piston 22 which is displaced downwards when compressed air is supplied to the cylinder 20. The piston 22 is, via an articulated lever mechanism 23 extending through a passage 24 in the tool, connected to two jaw-shaped grip members 25. The jaw-shaped grip members 25 each comprises a conically shaped external surface which is arranged to co-operate with a correspondingly shaped surface in a surrounding casing 26. When the lever mechanism 23 supplies a drawing force, the grip members 25 are displaced into the casing 26 and are pressed together such that they grip the draw portion 5 of the rivet.

Fig 3 shows a holder 8 of the chuck 7. The holder 8 comprises three cam surfaces 27 located at different radial distances from an axis of rotation 28 of the chuck 7. A roll 29 is arranged along each of the cam surfaces 27. When the chuck 7 is rotated in a counter clockwise direction in Fig. 3, the three rolls 29 move in a clockwise direction along their respective cam surfaces. The cam surfaces 27 have an inclination such that the radial dis- tance to the axis of rotation 28 decreases in this direction.

When the chuck 7 is rotated in a counter clockwise direction, the rolls 29 will thus move in a clockwise direction along the cam surfaces radially inwardly until they get into contact with the draw portion 5 of the rivet, which is applied in the holder 8. Each of the rolls 29 here provides a pressure force from different di- rections acting against the draw portion. Thereby, the holder 8 provides a clamping force which is arranged to retain the draw portion 5 when the rivet is used for drilling holes through the plates 1,2. When the chuck 7 is rotated in an opposite direction or is stationary, the rolls 29 do not any longer obtain any dis- placement radially inwardly and the clamping force of the rolls 29 against the draw portion 5 ends.

Such a chuck 7 is not restricted to be used in a tool for riveting but it may be used in a substantially arbitrary tool for receiving arbitrary rotary elements 5'. For example, the chuck may be used in a drilling machine for receiving of drills of variable sizes.

Advantageously, the chuck 7 comprises means which is ar- ranged to guide the rolls 29 towards the axis of rotation 28 with a retractable force in order to retain the rotary element 5'when the chuck is stationary. Thereby, the element 5 may also be in- troduced into a correct position between the rolls 29. Said means may comprise suitably positioned springs which tend to move the rolls 29 radially inwardly. According to an alternative, the rolls 28 may be magnetical such that they are kept together with a relatively weak magnetic force when the chuck 7 is sta- tionary.

Finally, Fig 4 shows an exploded view of a number of compo- nents of a riveting tool. Furthest to the right in the figure, a rivet according to the present invention is shown. The draw portion 5 of the rivet is introduceable through a hole of a washer 30. Be- hind the washer 30, the three rolls 29 are shown, which consti- tute a part of the holder 8. A bearing 31 and a nipple 32 are ar- ranged behind the holder 8. The rotary motion is transmitted to the chuck 7 via a transmission, which comprises the first gear- wheel 12, the belt 13 and the second gear-wheel 14. The sec- ond gear-wheel 14 is attached around a shaft 33 of the chuck 7.

Two bearings 34 allow a rotation of the chuck 7 in the tool. A lock washer 35 is arranged in connection to the casing 26, which has an inner surface arranged to co-operate with the external surface of the grip members 25. From the air cylinder 20, the passage 24 extends, which encases the articulated lever mechanism 23. Compressed air is supplied to the air cylinder 20 via the air supply conduit 21. Furthermore, the tool comprises miscellaneous attachment devices 17 and a compressed air nip- ple 37 for the supply of compressed air to the vane motor 9. A vane motor casing 38 is arranged to accommodate the vane motor 9 and the planetary gearing 10.

When a mechanic is to use the tool, a rivet is initially introduced into the holder 8 of the tool. The draw portion 5 of the rivet is here introduced between the rolls 29 of the holder. Thereafter, the mechanic depresses the button member 18 of the tool.

Thereby, the valve 16 is set in a position such that compressed air is supplied from the compressed air line 15, via the conduit 17, to the vane motor 9, which thereby obtains a rotary motion.

The motion of the vane motor 9 is transmitted, via the planetary gearing 10, the driving shaft 11, the first gear-wheel 12, the belt 13 and the second gear-wheel 14 to the chuck 7. By said trans- mission elements, a suitable reduction of the number of revolu- tions of the vane motor 9 is obtained. Thereby, the chuck 7 ob- tains a counter clockwise rotary motion such that the rolls 29 are

moved radially inwards by the cam surfaces 27 such that the rolls 29 provide a clamping force gripping the draw portion 5 of the rivet. Hereby, the rotary motion of the rolls 29 is transmitted to a corresponding rotary motion of the rivet. The mechanic dis- places the tool such that the rotating rivet is brought towards an intended point of attachment of a rivet between the first plate 1 and the second plate 2. With the cutting surface 6'of the rivet, the mechanic drills a hole through the plates 1,2. The rivet is introduced through the drilled hole until the stop surface 3'of the first portion 3 gets into contact with the surface 1'of the first plate. The mechanic leaves hold of the button member 18. The connection of the vane motor 9 to the compressed air line 15 is disconnected and the vane motor 9 stops. The rotary motion of the chuck 7 is discontinued and therewith also the grip of the rolls 29 on the draw portion 5. The mechanic depresses the button member 19 and connects the air cylinder 20 to the com- pressed air line 15. The piston 22 is displaced downwards and a drawing force is transmitted, via the articulated lever mechanism 23, to the grip members 25. The grip members 25 are moved backwards and are pressed together by the surrounding casing 26 such that the grip members 25 grip the draw portion 5 with a relatively large clamping force. A continued displacement of the piston 22 results in that the grip members 25 transmit a drawing force to the draw portion 5 of the rivet. The draw portion 5, which extends through the first portion 3 and the second portion 4 of the rivet, transmits the drawing force to the end portion 6.

Thereby, the second portion 4 is deformed plastically such that it obtains a stop surface 4'against the second surface 2'of the plate joint. When the second portion 4 has reached a deter- mined deformation state, a tensile stress is obtained in the draw portion 5 such that it breaks at an indication of fracture. The rivet is now applied in a very simple manner and by means of only one tool.

The invention is not in any way restricted to the described em- bodiment but may varied freely within the scope of the claims.

The tool does not necessarily need to have separate grip mem- bers for gripping the draw portion 5 during the drilling process and during the expansion process of the second portion. The tool does not need to be driven by compressed air but may be driven by a substantially arbitrary power source such as an electric motor or a battery.