EP2029834B1

EP2029834B1 - Tool for tying metal bars

Info

Publication number: EP2029834B1
Application number: EP07790137A
Authority: EP
Inventors: Evaristo Revelin; Diego Revelin
Original assignee: Revelin Evaristo & Figli SNC
Current assignee: Revelin Evaristo & Figli SNC
Priority date: 2006-06-07
Filing date: 2007-06-07
Publication date: 2010-07-28
Anticipated expiration: 2027-06-07
Also published as: EP2029834A1; DE602007008093D1; WO2007141822A1; ATE475758T1

Abstract

The invention is a tool (1; 200) for tying bars (Ba, Bb), in particular iron rods for reinforced concrete, comprising a frame (2; 202), with which the following elements are associated: a handgrip (3; 203); a reel (4; 204) of metal wire (F) for tying said bars (Ba, Bb); a feed unit (5; 205) of the metal wire (F); wire bending means (6; 206) to shape the metal wire (F) around the bars (Ba, Bb) to form turns (S); means (7; 207) for winding the turns (S) around the bars (Ba, Bb); means (8; 208) for cutting the metal wire (Ff); power means' (9; 209); means (10; 210) for controlling the power means (9; 209). The winding means (7; 207) comprise: a spindle (40; 240) having a rotary head (41; 241) and a rotary counter-head (42; 242) provided with pliers (43; 243) housing the turns (S); elastic means (44; 244) interposed between the head (41; 241) and the counter-head (42; 242) and cam means (45; 245) present in the rotary head (41; 241) for opening and closing the pliers (43; 243).

Description

The present invention concerns a tool for tying metal bars, in particular iron bars used for making the cage-like structures that make up the reinforcement of concrete castings.
It is known that the reinforcement of concrete castings is constructed with cage-like mesh structures comprising metal bars connected to each other at their crossing points by tying them with metal wire.
According to a known technique, the tying operations are carried out manually by means of pliers with which the ironworker twists the wire around the metal bars at their crossing points and then, after twisting it, cuts the ends that protrude from the area around which the wire has been twisted.
This known technique poses a first drawback, constituted by the fact that the tying operations, being made manually, are long and complex to carry out.
A further drawback lies in that it is increasingly difficult to find expert ironworkers on the market.
In order to overcome these drawbacks, make the tying operation rapid and allow it to be carried out even by unskilled personnel, portable manual tools have been developed, which are equipped with pliers that clamp a U-shaped metal clip around the metal bars.
These tools allow the bars to be tied more quickly, even by unskilled personnel, but the clamping force of the metal clip around the bars is not sufficient and this does not guarantee the stability of the structure.
Once the tying operation has been completed, therefore, the structure tends to deform easily and therefore is difficult to transport.
Tying tools of the type described in patent US5431196 are also known, which are provided with jaws inside which the bars to be tied are inserted and with a rotary spindle that winds a metal wire around the bars at their point of intersection, after the wire has been inserted in special crossed seats created in the spindle itself.
The tool described in the patent mentioned above has the drawback of being difficult to construct, due to the need to provide the spindle with the seats for the passage of the metal wire.
A second drawback is represented by the fact that it is difficult to insert the wire in the seats each time the tool is used.
A further drawback is constituted by the fact that the tool tends to jam often during use and therefore is not sufficiently reliable.
A further and equally important drawback lies in that the cutting device, which is provided with a pair of opposite rollers for cutting the wire, is complex to construct from a kinematic point of view.
Patent US5217049 is also known, concerning a tying tool with jaws that is differentiated from the previous one due to the fact the wire is not crossed inside the spindle, but outside, by means of a conical guide.
Also this patent, like the one previously described, poses the drawback that the mechanical parts are difficult to make, since in any case it is necessary to create seats for guiding the metal wire on the profiles of the cone and of the spindle.
Furthermore, the cutting system remains difficult to construct, since it consists, also in this case, of two opposite rollers.
Another tying tool is described in the Patent EP 1 440 746 and presents the drawback to be provided with a rotary spindle and pliers for clamping the metal wire which are difficult and expensive to be constructed and sometimes not sufficiently reliable.
Embodiments of tools for tying metal bars are also known, which are equipped with jaws where the bars to be tied are inserted and with rotary pliers between whose jaws the wire is passed.
The pliers clamp the metal wire and then, rotating on their own axis, twist it around the bar crossing point. The wire is cut by a pair of blades that move one against the other.
All the known tools described above pose the drawback of having complex kinematic mechanisms for transforming the rotary motion generated by the motor into the opening and closing motion of the pliers' jaws, the rotary motion of the pliers for twisting the wire and the movement of the pair of blades that cut the wire.
Furthermore, all the said tools are provided with a single motor that generates all the necessary movements and this involves the need to provide for kinematic means suited to transform the single rotary motion produced by the single motor into more rotary and/or alternated motions to be transferred to the various moving members.
The known tying tools mentioned also pose the drawback that their wire bending means often tend to tangle the wire.
Furthermore, also the wire cutting units are not sufficiently reliable, besides being expensive and difficult to construct.
Another, equally important drawback that is common to all the mentioned tools is constituted by the fact that for the tying operation they require a special, expensive metal wire that is supplied exclusively by the individual manufacturers of the tools.
The object of the present invention is to overcome all the drawbacks described.
In particular, it is a first object of the invention to construct a portable tool for tying metal bars that is equipped with means for winding the metal wire around the bars that are easier to make than the winding means provided in the tying tools carried out according to the known art.
It is a further object of the invention to carry out a portable tool for tying metal bars that is provided with more reliable wire bending means than those present in tying tools of known type.
It is a further object of the invention to carry out a tool for tying metal bars which is provided with a wire cutting unit that is more reliable than the cutting units present in the tying tools of known type.
It is a further aim of the invention to carry out a tying tool provided with kinematic mechanisms for operating the moving parts that are simpler than those present in the tying tools carried out according to the known art.
It is another, not less important object of the invention to provide a tying tool where for tying the bars it is possible to use a common metal wire of the type available on the market.
The objects mentioned above have been achieved through the construction of a tying tool suitable for tying bars with mainly longitudinal development, in particular iron rods for reinforced concrete, according to the contents of claim 1.
Other details of the tying tool that is the subject of the invention are described in the dependent claims.
According to the description provided here below, the wire winding means comprise a rotary spindle associated with a rotary head provided with pliers with openable jaws for holding the metal wire and winding it in turns around the metal bars.
The metal wire cutting unit is set moving by the rotation of the winding means and is positioned at the level of the wire bending means.
Different embodiments of the wire cutting unit and of the wire bending means are possible.
According to the invention, the tool is provided with a main motor for rotating the winding means and an auxiliary motor for feeding the wire.
Advantageously, the simpler construction of the tool that is the subject of the invention compared to the equivalent tools of known type makes it more reliable to use and therefore less subject to jamming, so that it requires less maintenance.
Still to advantage, the use of common metal wire to tie the bars ensures savings on the purchase of the wire itself.
Still advantageously, the presence of two separate motors, one for winding the wire turns around the bars and one for feeding the wire, ensures greater reliability and longer duration of the tool.
The objects and advantages described above will be highlighted in greater detail in the description of a preferred embodiment of the invention that is supplied as an indicative, non-limiting example with reference to the enclosed drawings, wherein:

Figure 1 shows a longitudinal section of the tying tool that is the subject of the invention;
Figure 1 a shows a detail of Figure 1;
Figures 2 and 3 are two different axonometric views of the front of the tool of Figure 1;
Figure 4 shows a detail of Figure 2;
Figure 5 shows the detail shown in Figure 4 in a different operating position;
Figure 6 shows an axonometric view of another detail of the tool that is the subject of the invention;
Figure 7 is an exploded view of the detail shown in Figure 6;
Figures from 8 to 13 show six axonometric views of the tool of the invention in six different operating stages;
Figure 14 shows two bars tied using the tool of the invention;
Figure 15 shows a longitudinal section of a construction variant of the tying tool that is the subject of the invention;
Figure 15a shows a detail of Figure 15;
Figures 16 and 17 are two different axonometric views of the front of the tool of Figure 15;
Figure 18 shows a detail of Figure 16;
Figure 19 shows the detail shown in Figure 18 in a different operating position;
Figure 20 shows an axonometric view of another detail of the construction variant of the tying tool that is the subject of the invention;
Figure 21 is an exploded view of the detail shown in Figure 20;
Figures from 22 to 27 show six axonometric views of the tool of the invention in six different operating stages.

The tool 1 that is the subject of the invention can be seen in its entirety and in longitudinal section in Figure 1 and also in Figures from 2 to 5, which show details of the same in front axonometric view.
It is preferably used to tie together metal bars Ba, Bb visible in the Figures 1 and 14 to make cage-like structures for concrete reinforcements.
It is evident, however, that the tool of the invention can be used also to tie metal rods of a different nature and for different purposes.
It can be observed in particular that the tool 1 comprises a frame 2 with a handgrip 3, which supports a reel 4 on which the metal wire F for tying the bars Ba, Bb is wound.
A feed unit 5 unwinds the metal wire F from the reel 4 and makes it advance towards wire bending means 6 that shape it to form one or more turns S around the above mentioned bars and at the same time also between means 7 suited to wind the turns S around the above mentioned bars at their crossing point.
It is also possible to notice the presence of a unit 8 for cutting the metal wire F, positioned at the level of the wire bending means 6. Power means, indicated as a whole by 9, of the winding means 7 and of the feed unit 5 cooperate with control means indicated by 10.
The reel 4 on which the metal wire F is wound is supported by a pin 11 that, as can be observed, is fixed to and projects from the frame 2, the reel being free to rotate with respect to said pin according to the axis X defined by the pin 11 itself.
The feed unit 5 of the metal wire F is positioned immediately downstream of the reel 4, as shown in Figure 1, and comprises a pair of gear wheels 12, 13 that mesh with each other and between which the wire F itself is included.
In particular, Figure 1a shows that both gear wheels 12, 13 are provided with a circumferential groove 14 containing the metal wire F, whose profile, in cross section, can be conjugated with the profile of the metal wire itself. The gear wheels 12, 13 cooperate with a reduction kinematic mechanism indicated as a whole by 15 that can be observed in Figure 3 and that sets them rotating.
It comprises a bevel gear 18 that sets rotating an intermediate shaft 17, passing through the frame 2, whose end is coupled with the gear wheel 12. The bevel gear 18, as shown in Figure 3, is positioned on the side opposite the gear wheels 12, 13 and is connected to an auxiliary motor 19 belonging to the above mentioned power means 9.
It can also be observed that downstream of the pair of gear wheels 12, 13 there is a tubular element 20 for guiding the wire, provided with a hole sized in such a way as to ensure optimal guide and optimal control of the wire F while it advances.
Engaging and disengaging means 21 for the gear wheels 12, 13 are also provided, which comprise a lever 22 hinged to the central part of the frame 2 through a pin 23, wherein said lever supports at one end 22a the pin of one of the gear wheels, for example the gear wheel 13, while its opposite end 22b on one side counteracts a cam element 24 provided with a manoeuvring rod 25 and on the other cooperates with elastic means 26 fixed to the frame 2.
As regards the wire bending means 6, it can be observed in particular in Figures from 2 to 5 that they comprise a wire bending channel 27 positioned downstream of the feed unit 5 at the side of a wire bending jaw 28 suited to receive the wire F coming out of the wire bending channel 27 and to shape it to form one or more of the above mentioned turns S.
The wire bending channel 27, in particular, is positioned downstream of the feed unit 5 and is created in a wire bending plate 29 associated with the frame 2, to which the wire bending jaw 28 is fixed, against and above the wire bending channel 27.
During the bending step, the wire bending channel 27 controls the wire in such a way as to reduce the risk of tangling during use of the tool, thus increasing its reliability compared to the known tools available on the market and in particular compared to the tools described above.
The cutting unit 8 is associated with the wire bending means 6 and with the wire bending plate 29 in which the wire bending channel 27 is created.
More precisely, the cutting unit 8 comprises a cutting blade 30 that is mechanically connected to shifting kinematic means indicated as a whole by 31 and is slidingly fitted in a blade holding channel 32 that intersects the wire bending channel 27, being created at the level of the upper part of the wire bending plate 29.
In particular, the cutting blade 30 is provided at one end with a rack 33 that is coupled with the shifting kinematic means 31 visible in Figures 3, 4 and 5 that cause its longitudinal movement according to the direction Y defined by the blade holding channel 32.
Furthermore, it can be observed that the cutting blade 30 has, in intermediate position, a recess 34 that houses the wire F to be cut when it comes out of the wire bending channel 27 and defines an inclined cutting edge 35.
The shifting kinematic means 31 comprise a toothed pinion 36, supported by the frame 2, which meshes with the rack 33 of the cutting blade 30 and is coupled with rotation levers 37 cooperating with thrust means 38 associated with the means 7 for winding the turns S around the bars Ba, Bb, as will be described in detail below.
The movement of the rotation levers 37 is made yielding by elastic mean 39 constituted by a spring 39a.
The movement of the cutting blade 30 controlled by the blade holding channel 32 and by the shifting kinematic means 31, together with the special profile of the inclined cutting edge 35 and of the recess 34, make the cutting operation more reliable compared to the tying tools of known type.
The winding means 7 are visible in particular in Figures from 5 to 7 and according to the invention they comprise:

a spindle 40 belonging to the power means 9;
a rotary head 41 fixed to the spindle 40;
a rotary counter-head 42 idly connected to the end 40a of the spindle 40 and axially opposing the rotary head 41;
one pair of pliers 43 associated with the rotary counter-head 42 and suited to house the turns S of wound wire F;
elastic means 44 interposed between the rotary head 41 and the rotary counter-head 42;
cam means 45 present in the rotary head 41 for opening and closing the pliers 43 during the rotation of the spindle 40.

First of all it should be observed that the spindle 40 is the shaft of a main motor 46 belonging to the power means 9 and, as can be observed, is supported by the frame 2.
The rotary head 41 substantially comprises a cylindrical body 47 provided with the cam means 45 and a central through hole 48 which houses the spindle 40 with which it creates the fixed connection.
Each one of the cam means 45 is constituted by a shaped channel 49 with curved profile converging towards the inside of the cylindrical body 47 of the rotary head 41.
As regards the rotary counter-head 42, it can be observed that it also consists of a substantially cylindrical body 50 comprising: the above mentioned pair of pliers 43, means 38 for thrusting the rotation levers 37 and a central through hole 51 which houses the end 40a of the spindle 40 with which it creates an idle connection.
As regards the pliers 43, they comprise two opposing jaws 52, in each one of which it is possible to identify:

an intermediate body 53 hinged to a radial slot 54 made in the body 50 of the rotary counter-head 42;
a first shaped projection 55 facing towards the turns S of wound wire F;
a second shaped projection 56 facing towards the rotary head 41 to cooperate with the cam means 45 of the rotary head 41 itself.

It can also be observed that the second shaped projection 56 comprises a spherical profile 56a that is inserted in the corresponding shaped channel 49 of the cam means 45.
As already said, elastic means 44 are interposed between the rotary head 41 and the rotary counter-head 42, said elastic means comprising a spring 44a, preferably but not necessarily of the helical type, which is included between a first housing 41a obtained in the rotary head 41 and a second housing 42a obtained in the rotary counter-head 42; wherein said housings face each other in such a way as to contain the helical spring 44a.
The thrust means 38 are constituted by a projecting body 38a present at the periphery of the substantially cylindrical body 50 of the rotary counter-head 42 that, during the rotation of the rotary counter-head, thrusts against a truncated cone-shaped head 38b associated with the rotation levers 37.
Thus, it is clear that in the winding means 7 the opening and closing of the pliers 43 are carried out by kinematic mechanisms that are simple to construct and reliable to operate, unlike the winding means present in the tying tools carried out according to the known art.
As regards the main motor 46 and the auxiliary motor 19, both belong to the power means 9 respectively of the winding means 7 and of the feed unit 5 and cooperate with control means 10. These comprise an electronic programming and control unit 10a, electrically connected to both motors, and push-button means 10b provided on the tool to be used by the operator.
The electronic programming and control means 10a in turn comprise adjustable timer means that are at the disposal of the operator and allow him/her to vary the operating time of the above mentioned motors at his/her discretion.
The latter, in particular, can be of the alternate current or continuous current type and can be powered through the power mains or a battery.
Figures 1 and 2 show that, above the wire bending means 6 and before the winding means 7, there is a unit 62 suited to position the bars Ba, Bb to be tied, which serves to define their position so that their crossing point, where they are tied, is substantially at the centre of the turns S.
For this purpose, the positioning unit 62 comprises an upper plate 63 fixed to the frame 2, which supports a fork 64 provided with elastic adjusting means 65.
The elastic adjusting means 65 comprise a sleeve 66 fixed to the upper plate 63, inside which a pin 67 is fitted, said pin being connected to the fork 64 and said fork having a spring 68 positioned coaxially outside the pin 67 between the fork 64 and the sleeve 66.
On the opposite side of the sleeve 66 there is a screw 69 that is fitted into a hole 70 made in the pin 67.
By adjusting the screw 69, it is possible to move the pin 67 in the sleeve 66 and thus to modify the position of the fork 64 so that the latter defines the position of the bars Ba, Bb to be tied with respect to the winding means 7.
All the parts that make up the tool, and in particular those in contact with the wire, are not carried out with special shapes and tolerances, but according to the common knowledge regarding mechanical construction.
Therefore, the tool that is the subject of the invention can use common wire of any type available on the market.
In practice, the operator couples the reel 4 with the wire F to the pin 11 and then inserts the wire F in the tubular wire-guiding element 20 belonging to the feed unit 5.
The operator uses the adjustable timer means of the electronic programming and control unit 10a to adjust the unwinding time of the wire F from the reel 4 and thus its length and the number of turns S, and also the number of revolutions of the winding means 7.
Consequently, the operator sets the above mentioned parameters to adjust the clamping force of the turns S around the metal bars Ba, Bb.
The bars are then positioned in such a way as to rest against the fork 64 of the positioning unit 62, after adjusting the latter through the screw 69, so that the bars are arranged substantially at the centre of the turns S.
When the push-button means 10b are operated, the electronic unit 10 activates a programmed operating cycle that includes the following steps, performed through the rotation of the respective electric motors:

winding of one or more turns S of wire F around the bars Ba, Bb as shown in Figure 1 and in Figure 3;
cutting of the wire F immediately after the winding means 7 have started rotating to move the cutting blade 30 as shown in Figure 4;
several revolutions of the winding means 7, intended to obtain the twisting of the turns S that can be observed in Figures 11, 12 and the tying of the bars as shown in Figure 13;
stop of the winding means 7;
opening of the pliers 43 and separation of the tool from the tying point, as shown in Figure 12, so as to tie the bars as shown in Figure 14.

With reference to Figures from 8 to 13, it is important to notice that the bar tying cycle is carried out in successive steps, starting from the initial situation shown in Figure 8, where the pliers 43 are open, with the turns S arranged between the jaws 52 and the rotary head 41 and the rotary counter-head 42 at rest.
The rotation of the rotary head 41 takes place in the counterclockwise direction indicated by the arrow A in Figure 9, where it is possible to observe that at the beginning of the rotation the spring 44a is compressed and at the same time the pliers 43 are closed owing to the contact of the spherical profiles 56a of the jaws 52 with the corresponding shaped channels 49 of the cam means 45. The rotary counter-head 42 is set rotating by the rotary head 41 as shown in Figure 10 and this causes the turns S to be twisted around the bars Ba, Bb at the point of intersection of the latter.
Starting from the beginning of the rotation and with reference to Figures 8 and 9, it can be observed that the projecting body 38a that makes up the thrust means 38 of the rotary counter-head 42 is arranged downstream of the truncated cone-shaped head 38b associated with the rotation levers 37 which operate the blade 30 that cuts the wire F.
During the rotation which, has already said, takes place in the counterclockwise direction indicated by the arrow A, the projecting body 38a moves away from the truncated cone-shaped head 38b as shown in Figure 10, and, approximately at the end of the first revolution, reaches a position upstream of said head, as shown in Figure 11.
As it keeps rotating, the projecting body 38a counteracts the truncated cone-shaped head 38b and moves it in the direction indicated by the arrow C in Figures 11 and 12, in such a way as to operate the shifting kinematic means 31 and the cutting blade 30 connected to them, in order to cut the wire F.
The turns S are thus free starting from the cutting point at the level of the wire bending means.
As soon as the projecting body 38a has passed beyond the truncated cone-shaped head 38b, this immediately returns to the initial position due to the elastic recovery of the spring 39a associated with the rotation levers 37, which had been compressed during the shift of the latter induced by the movement of the truncated cone-shaped head 38b.
The rotation of the rotary head 41 and of the rotary counter-head 42 continues until the turns have been completely wound around the bars, as shown in Figure 13.
The rotation of the rotary head 41 stops once the set time has elapsed and at this point the rotary counter-head 42 starts counter-rotating with respect to the rotary head 41 in the clockwise direction indicated by the arrow O, due to the elastic recovery of the spring 44a, and at the same time the pliers 43 open due to the contact of the spherical profiles 56a of the jaws 52 with the cam means 45.
It can thus be understood that each revolution of the winding means 7 involves a shift of the cutting blade 30, but this does not affect the wire cutting operation, which is carried out in a single step with the first movement of the blade itself.
At the end of the cycle the tool is ready to carry out a new tying operation, repeating all the steps described above.
A construction variant of the tying tool that is the subject of the invention, indicated as a whole by 200, can be seen in longitudinal section in Figure 15 and also in Figures from 16 to 19, which show some details of the same in front axonometric view.
In said construction variant, like in the embodiment described above, the tool 200 comprises a frame 202 with a handgrip 203, which supports a reel 204 around which the metal wire F for tying the bars Ba, Bb is wound.
A feed unit 205 unwinds the metal wire F from the reel 204 and makes it advance towards wire bending means 206 that are visible in their entirety in Figures 16 and 17 and that shape it to form one or more turns S around said bars.
At the same time the turns S are also arranged between winding means 207 and around said bars Ba, Bb at the level of their crossing point.
It is also possible to notice the presence of a unit 208 for cutting the metal wire F, positioned at the level of the wire bending means 206.
Power means, indicated as a whole by 209, suited to power the winding means 207 and the feed unit 205, cooperate with control means indicated by 210.
The reel 204, around which the metal wire F is wound, is supported by a pin 211 that is fixed to and projects from the frame 202, said reel being free to rotate with respect to said pin according to the axis X defined by the pin 211 itself.
The feed unit 205 of the metal wire F is positioned immediately downstream of the reet 204, as shown in Figure 15, and comprises a pair of gear wheels 212, 213 that mesh with each other and between which the wire F is included.
Figure 15a shows that both the gear wheels 212, 213 are provided with a circumferential groove 214 containing the metal wire F, whose profile, in cross section, can be conjugated with the profile of the metal wire itself.
The gear wheels 212, 213 cooperate with a reduction kinematic mechanism, indicated as a whole by 215, that can be observed in Figure 17 and that sets them rotating.
It comprises a bevel gear 218 that sets rotating an intermediate shaft 217, passing through the frame 202, whose end is coupled with the gear wheel 212, as shown in Figure 15.
As shown in Figure 17, the bevel gear 218 is positioned on the opposite side of the gear wheel 212 and is connected to an auxiliary motor 219 belonging to the above mentioned power means 209.
Downstream of the pair of gear wheels 212, 213 there is a tubular element 220 for guiding and controlling the wire F while it advances.
The engaging and disengaging means 221 for the gear wheels 212, 213 are provided with a lever 222 hinged to the central part of the frame 202 through a pin 223, which supports at one end 222a the pin of the gear wheel 213 and whose opposite end 222b counteracts a cam element 224 provided with a manoeuvring rod 225 and cooperating with elastic means 226 fixed to the frame 202.
As regards the wire bending means 206, it can be observed in particular in Figures from 16 to 19 that they comprise a wire bending channel 227 positioned downstream of the feed unit 205, beside a wire bending jaw 228.
The wire bending channel 227 is positioned downstream of the feed unit 205 and is created in a wire bending plate 229 associated with the frame 202, to which the wire bending jaw 228 is fixed, against and .above the wire bending channel 227.
The construction variant described herein is differentiated from the others due to the fact that in opposite position above the wire bending jaw 228 and the wire bending channel 227 there is a wire bending counter-jaw 233 that, as shown in particular in Figure 15, has one end 233b hinged to the frame 202 through a pin 234 and is associated with manoeuvring means 236 that can be operated by the operator and are suited to make it rotate around the pin 234.
The manoeuvring means 236 comprise a flexible cable 237 having one end 237a connected to a manoeuvring lever 238 associated with the frame 202 and the opposite end 237b connected to the counter-jaw 233 through a lever 237c.
A sheath 239 covers the flexible cable 237 and an elastic element 235 is interposed between the counter-jaw 233 and the frame 202 for the spontaneous return of the counter-jaw 233 to the initial position when the manoeuvring lever 238 is released.
The jaw 228 and the counter-jaw 233 present curved profiles with opposing concavities 228a and 233a, suited to receive the wire F coming out of the wire bending channel 227 and to shape it to form one or more of the above mentioned turns S.
It is clear, therefore, that in the construction variant described herein the wire bending means 206, comprising the wire bending channel 227 and also the wire bending counter-jaw 233, guarantee better control and higher bending capacity of the wire, thus further reducing the risk of the wire getting entangled during use of the tool.
Increased reliability of the tool is thus obtained.
The cutting unit 208 belongs to the wire bending plate 229 and comprises a cutting blade 230 slidingly fitted in a blade holding channel 232 that intersects the wire bending channels 227 and is operatively connected to a thrust cam 231 belonging to the winding means 207 that will be described below.
The cutting blade 230 also has, at one end, a cutting profile 230a and at the opposite end a shaped profile 230b that cooperates with the thrust cam 231 belonging to the winding means 207.
The cutting blade 230 also has a projection 230c that counteracts an elastic element 270 having one end 270a in contact with the projection 230c and the opposite end 270b fixed to the frame 202.
In this way the return of the cutting blade 230 to its position after cutting the wire F at the end of the thrust action of the thrust cam 231 takes place spontaneously.
This construction variant of the cutting unit 208 is simpler than the embodiment described above.
This further facilitates the cutting of the wire and the operation of the tool is more reliable owing to the reduced number of components of the kinematic mechanisms that set the cutting blade 230 in motion.
Furthermore, the direct and axial contact between the cutting blade 230 and the thrust cam 231 favours the cutting operation, since it optimizes the axial thrust exerted by the cam 231 on the cutting blade 230 during the rotation of the winding means 207.
The winding means 207 are visible in particular in Figures from 15 to 21, where it can be observed that, as in the embodiment described above, they comprise:

a spindle 240 belonging to the power means 209;
a rotary head 241 fixed to the spindle 240;
a rotary counter-head 242 idly connected to the end 240a of the spindle 240 and axially opposing the rotary head 241;
a pair of pliers 243 associated with the rotary counter-head 242 and suited to house the turns S of wound wire F;
elastic means 244 interposed between the rotary head 241 and the rotary counter-head 242;
cam means 245 present in the rotary head 241 for opening and closing the pliers 243 during the rotation of the spindle 240.

Also in this construction variant the spindle 240 is the shaft of a main motor 246 belonging to the power means 209 and, as can be observed, is supported by the frame 202.
With particular reference to Figures 20 and 21, it is possible to observe that the rotary head 241 substantially comprises a cylindrical body 247 provided with the cam means 245 and a central through hole 248 which houses the spindle 240 with which it creates the fixed connection.
Each one of the cam means 245 is constituted by a shaped channel 249 with curved profile converging towards the inside of the cylindrical body 247 of the rotary head 241. As regards the rotary counter-head 242, it also comprises a substantially cylindrical body 250 where there are: the above mentioned pliers 243, the thrust cam 231 of the cutting blade 230 and a central through hole 251 which houses the end 240a of the spindle 240 with which it creates an idle connection.
As regards the pliers 243, they comprise two opposing jaws 252, in each one of which it is possible to identify:

an intermediate body 253 hinged to a radial slot 254 made in the body 250 of the rotary counter-head 242;
a first shaped projection 255 facing towards the turns S of wound wire F;
a second shaped projection 256 facing towards the rotary head 241 to cooperate with the cam means 245 of the rotary head 241 itself.

It can also be observed that the second shaped projection 256 comprises a spherical profile 256a that is inserted in the corresponding shaped channel 249 of the cam means 245.
As already said, elastic means 244 are interposed between the rotary head 241 and the rotary counter-head 242, said elastic means comprising as spring 244a, preferably but not necessarily of the helical type, which is included between a first housing 241a obtained in the rotary head 241 and a second housing 242a obtained in the rotary counter-head 242, which face each other in such a way as to contain the helical spring 244a.
As regards the thrust cam 231, it is positioned at the periphery of the substantially cylindrical body 250 of the rotary counter-head 242 that, during the rotation of the rotary counter-head, thrusts against a shaped profile 230b present at one end of the cutting blade 230.
As regards the main motor 246 and the auxiliary motor 219, both belong to the power means 209 respectively of the winding means 207 and of the feed unit 205, and cooperate with control means 210.
These comprise an electronic programming and control unit 210a, electrically connected to both motors, and push-button means 210b provided on the tool to be used by the operator.
The electronic programming and control means 210a in turn comprise adjustable timer means that are at the disposal of the operator and allow him/her to vary the operating time of the above mentioned motors at his/her discretion.
The motors, in particular, can be of the alternate current or continuous current type and can be powered through the power mains or a battery.
In practice, when the operator wants to use the tool, first of all he/she couples a reel 204 of wire F with the pin 11 and inserts the wire F in the tubular wire-guiding element 220 belonging to the feed unit 205.
The operator uses the adjustable timer means of the electronic programming and control unit 210a to adjust the unwinding time of the wire F from the reel 204 and thus its length as well as the number of turns S and the number of revolutions of the winding means 207.
Consequently, the operator sets the number of revolutions to adjust the clamping force of the turns S around the metal bars Ba, Bb.
The bars Ba, Bb are arranged between the wire bending jaw 228 and the wire bending counter-jaw 233 and then the operator activates a programmed operation cycle via the push-button means 210b of the electronic unit 210.
This includes the following steps, which are performed by operating the respective electric motors:

winding of one or more turns S of wire F around the bars Ba, Bb as shown in Figure 15 and in Figure 17;
cutting of the wire F immediately after the winding means 207 have started rotating to move the cutting blade 230 as shown in Figure 18;
several revolutions of the winding means 207, intended to obtain the twisting of the turns S that can be observed in Figures 25, 26 and the tying of the bars as shown in Figure 27;
stop of the winding means 207;
opening of the pliers 243 and separation of the tool from the tying point, as shown in Figure 26, so as to tie the bars as shown in Figure 28.

With reference to Figures from 22 to 27, it is important to notice that the bar tying cycle is carried out in successive steps, starting from the initial situation shown in Figure 22, where the pliers 243 are open, with the turns S arranged between the jaws 252 and the rotary head 241 as well as the rotary counter-head 242 at rest.
The rotation of the rotary head 241 takes place in the counterclockwise direction indicated by the arrow A in Figure 23, where it is possible to observe that at the beginning of the rotation the spring 244a is compressed and at the same time the pliers 243 are closed owing to the contact of the spherical profiles 256a of the jaws 252 in the corresponding shaped channels 249 of the cam means 245.
The rotary counter-head 242 is set rotating by the rotary head 241 as shown in Figure 24 and this causes the turns S to be twisted around the bars Ba, Bb at their point of intersection.
Starting from the beginning of the rotation and with reference to Figures 22 and 23, it can be observed that the thrust cam 231 is positioned downstream of the shaped profile 230b positioned at the end of the cutting blade 230 that therefore for the moment is not operated.
During the rotation of the head which, as shown in Fgure 23, takes place in the counterclockwise direction indicated by the arrow A, the thrust cam 231 moves away from the shaped profile 230b until it comes into contact with the same, approximately towards the end of the first revolution, as shown in Figure 25.
While it keeps rotating, the thrust cam 231 counteracts the shaped profile 230b and moves the cutting blade 230 in the direction indicated by the arrow C of Figure 25, in order to cut the wire F.
The turns S are thus free, starting from the cutting point at the level of the wire bending means.
As soon as the thrust cam 231 has passed beyond the shaped profile 230b, the cutting blade 230 immediately returns to its initial position due to the action of the elastic element 270 that recalls it.
The rotation of the rotary head 241 and of the rotary counter-head 242 continues until the turns have been completely wound around the bars, as shown in Figure 27.
The rotation of the rotary head 241 stops once the set time has elapsed and at this point the rotary counter-head 242 starts counter-rotating with respect to the rotary head 241 in the clockwise direction indicated by the arrow O, due to the elastic recovery of the spring 244a, and at the same time the pliers 243 open due to the contact of the spherical profiles 256a of the jaws 252 with the cam means 245. It can thus be understood that each revolution of the winding means 207 involves a shift of the cutting blade 230, but this does not affect the wire cutting operation, which is carried out in a single step with the first movement of the blade itself.
At the end of the cycle, the tool is ready to carry out a new tying operation, repeating all the steps described above.
It is important to point out that in both the construction variants described above all the parts that make up the tool and in particular those in contact with the wire are not carried out with special shapes and tolerances, but according to the common knowledge regarding mechanical construction.
Therefore, the tool that is the subject of the invention, in both construction variants, can use common wire of any type available on the market.
On the basis of the above, it is clear that the tool that is the subject of the invention, in both the construction variants described, achieves all the set objects.
In particular, the tool is simpler to construct than the known tools, especially as regards the means for winding the metal wire around the bars.
Also the kinematic elements of the moving parts that make up the tool are simpler to construct.
Furthermore, the wire bending means and the wire cutting unit are more reliable than those present in tying tools of known type.
In the construction phase, further construction variants can be made, which are neither represented nor described herein, but which must all be considered protected by the preset patent if they fall within the scope of the following claims.
In the cases where the technical characteristics illustrated in the claims are followed by references, these have been added only with the aim to facilitate the comprehension of the claims themselves and therefore said references do not have any limiting effect on the degree of protection to be granted to each element they identify only by way of example.

Claims

Tool (1; 200) for tying bars (Ba, Bb), in particular iron rods for reinforced concrete, comprising a frame (2; 202), with which the following elements are associated:
- a handgrip (3; 203);

- a reel (4; 204) on which the metal wire (F) for tying said bars (Ba, Bb) is wound;

- a feed unit (5; 205) for unwinding said reel (4; 204) and feeling said metal wire (F);

- wire bending means (6; 206) suited to shape said metal wire (F) coming out
of said feed unit (5; 205) to form one or more turns (S) around said bars (Ba, Bb) arranged between said wire bending means (6; 206);

- means (7; 207) for winding said turns (S) around said bars (Ba, Bb);

- at least one pair of pliers (43; 243) suited to house said turns (S);

- a unit (8; 208) for cutting said metal wire (F);

- means (9; 209) for powering said winding means (7; 207) and said feed unit (5; 205);

- a spindle (40; 240) belonging to said power means (9; 209);

- control means (10; 210) for said power means (9; 209);
characterized in that said winding means (7; 207) comprise:
- a rotary head (41; 241) fixed to said spindle (40; 240);

- a rotary counter-head (42; 242) idly connected to the end (40a; 240a) of said spindle (40; 240), axially opposing said rotary head (41; 241), said at least one pair of pliers (43; 243) being associated with said rotary counter-head;

- elastic means (44; 244) interposed between said rotary head (41; 241) and said rotary counter-head (42; 242); and

- cam means (45; 245) present in said rotary head (41; 241) for opening and closing said pliers (43; 243) during rotation of the spindle (40,240)
Tool (1; 200) according to claim 1), characterized in that said spindle (40; 240) is the rotating shaft of a main motor (46; 246) belonging to said power means (9; 209).
Tool (1; 200) according to claim 1), characterized in that said rotary head (41; 241) comprises a substantially cylindrical body (47; 247) provided with said cam means (45; 245) and a central through hole (48; 248) which houses said spindle (40; 240) with which it creates a fixed connection.
Tool (1; 200) according to claim 1), characterized in that said rotary counter-head (42; 242) comprises a substantially cylindrical body (50; 250) provided with at least one pair of pliers (43; 243) and a central through hole (51; 251) which houses the end (40a; 240a) of said spindle (40; 240) with which it creates an idle connection.
Tool (1; 200) according to claim 1), characterized in that said at least one pair of pliers (43; 243) comprise at least two jaws (52; 252) opposing each other, each one of which comprises:
- an intermediate body (53; 253) hinged to a radial slot (54; 254) made In said cylindrical body (50; 250) of said rotary counter-head (42; 242);

- a first shaped projection (55; 255) facing towards said turns (S);

- a second shaped projection (56; 256) facing towards said rotary head (41; 241) to cooperate with said cam means (45; 245) of said rotary head (41; 241).
Tool (1; 200) according to claim 5), characterized in that said second shaped projection (56; 256) comprises a spherical profile (56a; 256a) that cooperates with said cam means (45; 245).
Tool (1; 200) according to any of claims 1), 3), 5) or 6), characterized in that each one of said cam means (45; 245) is a shaped channel (49; 249) with curved profile converging towards the inside of said cylindrical body (47; 247) of said rotary head (41; 241).
Tool (1; 200) according to claim 1), characterized in that said elastic means (44; 244) comprise a spring (44a; 244a) included between a first housing (41 a; 241a) created in said rotary head (41; 241) and a second housing (42a; 242a) created in said rotary counter-head (42; 242), facing each other.
Tool (1) according to claim 1), characterized in that said wire bending means (6) comprise:
- a wire bending channel (27) positioned downstream of said feed unit (5) and obtained in a wire bending plate (29) which belongs to said frame (2) and with which said cutting unit (8) of said wire (F) is associated;

- a wire bending jaw (28) positioned beside said wire bending channel (27) and fixed against said wire bending plate (29), suited to receive said wire (F) coming out of said wire bending channel (27) and to shape it in one ore more turns (S).
Tool (1) according to claim 9), characterized in that said cutting unit (8) comprises a cutting blade (30) mechanically connected to shifting kinematic means (31) and slidingly fitted in a blade holding channel (32) that intersects said wire bending channel (27) and is created in said wire bending plate (29).
Tool (1) according to claim 10), characterized in that said cutting blade (30) is provided at one end with a rack (33) coupled with said shifting kinematic means (31) and in an intermediate position with a recess (34) that defines an inclined cutting edge (35) which houses the wire (F) to be cut that comes out of said wire bending channel (27).
Tool (1) according to claim 11), characterized in that said shifting kinematic means (31) comprise a toothed pinion (36) meshing with said rack (33) of said cutting blade (30) and coupled with rotation levers (37) cooperating with thrust means (38) associated with said rotary counter-head (42).
Tool (1) according to claim 1), characterized in that said feed unit (5) comprises at least one pair of gear wheels (12, 13) meshing with each other, between which there is said wire (F) and which cooperate with a reduction kinematic mechanism (15) for rotating said gear wheels (12, 13) and for advancing said wire (F) between them.
Tool (1) according to claim 1), characterized in that said power means (9) comprise a main motor (46) associated with said winding means (7) and an auxiliary motor (19) associated with said feed unit (5), both motors (46, 19) being electrically connected to said control means (10).
Tool (200) according to claim 1), characterized in that said wire bending means (206) comprise:
- a wire bending channel (227) obtained in a wire bending plate (229) which belongs to said frame (202) and with which said cutting unit (208) is associated;

- a wire bending jaw (228) fixed against said wire bending plate (229), beside said wire bending channel (227);

- a wire bending counter-jaw (233) opposing said wire bending jaw (228) and said wire bending channel (227),
said jaw (228) and said counter-jaw (233) being suited to shape said wire (F) coming out of said wire bending channel (227) in such a way as to form one or more turns (S).