The present invention relates to a method for binding elongate objects together by means of at least one wire, in particular for lashing reinforcing bars, electric cables or the like, two claws provided with guide surfaces for the wire being guided down over the objects to be bound together, after which a wire is fed along the guide surface of one claw and across to the guide surface of the other claw, so that it is shaped into a wire loop surrounding the objects on three sides, and the legs of the wire loop are twisted together on the fourth side of these objects.
The invention also relates to a machine for use in implementing such a method.
Conventionally, the lashing of reinforcing bars to form reinforcing mats is carried out with the aid of simple, manual tools, which is a very time-consuming and thus expensive and also laborious operation, which is apt to give rise to attritional injuries. The reason for this is that, when lashing reinforcing mats for concrete slabs, arches or the like using previous aids, the operator has to bend for long periods of time, which leads to great stress on the back.
In this connection, the lashing of the reinforcing bars is usually effected with the aid of tongs or a twisting tool, by means of which the ends of a wire, which is arranged by hand around the reinforcing bars at the various intersection points, are twined or twisted together for firm connection of the bars. Carrying out lashing in the conventional manner also involves risks of accident, especially in the case of work on roofs, bridges and the like, owing to the stooped working position which, inter alia, leads to risks of falling accidents.
In my International patent application PCT/SE91/00571, a machine is described for binding intersecting bars together by means of wires, in particular for lashing reinforcing bars, which machine works in accordance with the method indicated in the first paragraph above. By means of this machine, the lashing operation can be made considerably more efficient at the same time as the abovementioned risks of injury can be eliminated or considerably reduced, as this machine allows the operator to work upright.
In known lashing machines, which are provided with a rotatable twisting head arranged above the jaws so as to replace the manual twisting-together of the wire ends with the aid of tongs or the like, there is inter alia a risk of the lashing wire breaking as a result of excessive tension in it if the wire parts are secured in the twisting head. Furthermore, it can be difficult, owing to tensile forces in the wire, to make the latter surround the reinforcing bars closely at the twisting location.
The present invention is based on the knowledge that this is due to the fact that the machine cannot imitate the movement of the hand during manual twisting. When manual twisting-together of two wire ends is carried out, the wire is first stretched around the reinforcing bars. During twisting, the hand and thus the wire ends will then approach the upper reinforcing bar in the course of twisting owing to the fact that the twisting itself requires a certain wire length.
In a twisting machine with a rotatable twisting head, the wire ends are usually secured in the twisting head throughout the twisting operation, which means that the extra wire length required for the twisting itself cannot be fed down through the twisting head. This results in increased tension in the wire, which may lead to the latter breaking and those portions of the wires which are twisted together being drawn up from the reinforcing bars, so that an interspace is formed between the uppermost bar and the twisted-together portions of the wire ends.
Another disadvantage of known lashing machines is that they comprise pivotable claws which have to be closed and opened a great many times a day by hand movements of the operator, which is very tiring. Moreover, the risk of functional disorders of the machine increases.
One object of the present invention is to provide a method for binding elongate objects together in the way indicated in the first paragraph above, which can be implemented without risk of the wire breaking or the attachment of the wire loop obtained to the objects being defective.
Another object is to provide a simple, reliable machine for use in implementing the method.
The invention is based on the knowledge that the abovementioned aims can be achieved by virtue of the twisting head being made so that the wire ends are held in it in such a way that wire can be drawn out from the head when the tension in the wire exceeds a given value during a twisting operation.
According to the present invention, a method of the type indicated in the first paragraph is then particularly characterized in that the wire is fed to the said guide surface of one claw via a first guide arrangement in an arrangement which is rotatable relative to the claws, and is fed away from the second claw via a second guide arrangement in the rotatable arrangement, in that the rotatable arrangement is made to rotate for twisting-together of the two parts of the wire for binding together the objects the wire surrounds, and in that, during twisting together, the wire is held in each guide arrangement in the said rotatable arrangement such that the wire length necessary for twisting-together of the wire parts is allowed to be drawn out while a resistance is overcome.
By virtue of the fact that wire can be drawn out from the twisting head during twisting together, no detrimental tension or traction arises in the wire, which may cause the wire to break. As the drawing-out of wire takes place counter to a certain resistance, the twisting-together will take place closely adjacent to the objects to be bound together. In this way, functioning similar to that during manual twisting is achieved.
In a preferred embodiment, a retracting force is applied to the wire after it has been fed but before twisting together has started. In this way, the wire is stretched, so that it surrounds very closely the objects to be bound together, which further improves the twisting result.
The wire is suitably fed to the claws from a reel and is cut off before the rotatable arrangement is made to rotate. During the feed of the wire from the guide surface of one claw to the guide surface of the other claw, the wire is guided by a movable means which is guided by the first said claw and is carried along by the wire in its feed movement. This allows the use of fixed claws, which is a very great advantage since, inter alia, tiring hand movements are avoided, and because a machine of the type described has to be very robust and impact-resistant in order to cope with the very rough treatment to which it is usually subjected on a building site.
The particularly characteristic features of a machine for use in implementing the method emerge from the first independent claim directed to the machine.
An especially preferred embodiment of this machine is characterized in that the rotatable arrangement is in the form of a cylinder with guide ducts for the wire passing through in the axial direction and in that the said cylinder is arranged rotatably in a cylindrical guide.
Further features of the invention emerge from subsequent claims.
The invention will be described in greater detail below with reference to the embodiments shown by way of example in accompanying drawings.
The machine comprises two fixed claws 6 and 7 connected firmly to the cylindrical outer casing 5. The claws are separated from one another by a spacing which allows them to be guided down over an intersection of reinforcing bars 8 or other objects to be bound together. In this connection, the outer casing 5 is designed as a supporting body with a seat 9 adapted to the shape of the reinforcing bars 8. Before a lashing operation, the machine can then be set down on the reinforcing bars 8, so that it rests on these (see
The claws 6, 7 are made with guide grooves 10 and, respectively, 11 for a lashing wire 12 which is used for binding reinforcing bars together. This is effected by wire from a wire reel arranged in the housing 13 being fed to a twisting arrangement 14 which, after the wire has been made to surround two intersecting reinforcing bars by means of the claws 6, 7 and after cutting off the wire, twists together the two legs of the wire loop obtained, as will be described in greater detail below.
The twisting head 14 is driven by a shaft 15 from an electric motor 16 via a gear reduction device 17.
Further components of one embodiment of the machine and a work cycle for it will now be described in greater detail with reference to
The twisting head consists of an inner cylinder 14, which is mounted rotatably in the cylindrical outer casing 5. The inner cylinder 14 comprises two feed and guide ducts 23 and 24 for the lashing wire. Also mounted in the inner cylinder 14 is a scissors-like construction which comprises two legs which are pivotable relative to one another and can be pressed apart by virtue of a suitably somewhat elastic ball 25 being pressed downwards between the upper ends 26 of the legs, which results in the lower ends 27 of the legs being pressed outwards and entering into braking engagement with lashing wire fed into the ducts 23 and 24, as will be described in greater detail below. Owing to the lever action obtained, it will be possible for the leg ends 27 to be pressed outwards with great force.
The ball 25 is provided with a guide pin 29 which is inserted freely into a threaded spindle 28 and can be pressed into the spindle 28 counter to the action of a spring 30. Reference number 31 designates a bearing arrangement which prevents the guide pin 29 and the ball 25 being carried along in the rotation of the spindle 28.
The threaded spindle 28 interacts with a corresponding thread in a hole 32 in a top closure of the outer, fixed cylinder 5. The threaded spindle 28 merges with an upper, smooth part 43 with a driving pin 33 which projects out into a slot 34 in a tubular driving shaft 15 from the gear reduction device 17.
Reference number 35 designates a solenoid which is fed via slip-ring contacts 36 and actuates a locking means 37 which, when the solenoid is activated, is pressed in and fixes a lashing wire 12, which has been introduced into the duct 24, so that it cannot be retracted.
As shown in the section through the claw 6 in
At its front edge, the guide channel 38 is made with a stop surface 41, with which the front end of the lashing wire 12 will interact in order to carry the guide channel along in its feed movement. The opposite claw 7 comprises a recess 42 adapted to receive a part of the front part of the guide channel 38 in order to free the front end of the wire 12 from the stop surface 41, as will be explained in greater detail below.
In order for it to be possible to bring about reliable guidance of the wire during its feed, the guide groove 11 in the second claw 7 is closed by means of two spring-loaded, cover-like elements 44 (see
In
It can be seen from
In this position, the feed of the wire is stopped, and the solenoid 35 is activated, so that the front end of the wire is fixed in the guide duct 24 in the cylinder 14 (see
When the retraction described of the wire 12 takes place, the latter will be drawn out in the lateral direction from the outwardly open guide channel 38 in the claw 6 and will also be drawn out in the lateral direction from the guide groove 11 in the claw 7. The cover-like closing elements 44 will then be pressed apart by the wire counter to the action of associated springs. The position shown in
Before twisting together, the wire 12 is cut off by means of the knife 22, and the solenoid 35 is deactivated, so that the locking means 37 frees the wire end (see
When the spindle 28 has descended to the ball 25, the engagement of the leg ends 27 with the wire 12 in the guide ducts 23, 24 has reached such a value that the wire ends are retained securely in the guide ducts but in such a way that they can still, when a certain tensile force arises in the wire, be drawn out of the guide ducts owing to the fact that at least the surface layer of the ball 25 is elastic.
In this position, the threaded spindle 28 will make contact with the elastic ball 25 and will then carry both the ball and the scissors-like construction and thus the inner cylinder 14 as well along in its continued rotational movement (see
The embodiment described above includes separate means, the scissors-like construction, for securing the wire in the guide ducts.
However, such means can normally be dispensed with, especially when using a relatively stiff lashing wire, such as that which is used for instance in Sweden for lashing reinforcing bars in concrete constructions. Due to the stiffness of the wire, after the wire has been drawn off from the reel it tends to resume its curved shape which leads to the wire being pressed against the walls of the guide ducts at various positions. This results in an increased friction between the wire and the walls of the ducts.
Further, as the wire during a twisting operation is pulled out obliquely from the mouths of the two guide ducts the wire is bent around and pressed against the edge of each mouth. This gives rise to a substantial increase of the force required to pull out the wire from the guide ducts.
Thus, there is normally such a resistance against the pulling out of the wire that a tight twist is obtained without the use of any separate securing means in the guide ducts.
This makes it possible to design a very simple, robust and reliable lashing machine the lashing head of which in its simplest embodiment may comprise an inner rotable cylinder provided with two guide ducts for the lahing wire and an outer, fixed guiding cylinder.
Such a preferred embodiment of the present invention will now be described with reference to
In
Like the previously described embodiment the inner cylinder 14 comprises two feed and guide ducts 23 and 24 for the lashing wire 12 and solenoid 35 which actuates a locking means 37 in the guide duct 24.
As regards
Following the step illustrated in
Owing to the rotation of the inner cylinder 14, the ends of the wire 12 will be twisted together on the top side of the uppermost reinforcing bar 8 and will in this connection bring about secure binding-together of the reinforcing bars at the intersection point. To achieve tight binding-together of the reinforcing bars, there must be a certain tension in the wire during the twisting operation. This tension is created due to the resistance that must be overcome when pulling out the wire. The resistance is caused by the friction between the wire and the ducts 23 and 24 in the inner cylinder and especially the friction against the edges of the lower mouths of the ducts where the wire is bent when pulled out at an oblique angle during a twisting operation. In order to increase this friction a ring of rubber or other high friction and wear-resistant material can be arranged in the mouths.
The friction can also be increased by reducing the area of the ducts over their total length or just as one or more restrictions in the ducts. The ducts can also comprise different sections which form a small angle relatively each other.
The result of a twisting operation is shown in
As an alternative to the previously described retraction of the wire, shown in
In order to obtain a strong stretching of the wire so that it closely surrounds the reinforcing bars 8 to be twisted together the feed of the wire through the first guide duct 23 is positively locked before the pulling force is applied. This can be obtained by means of a solenoid actuated locking means arranged in the inner cylinder 14 so that it locks the wire in the first guide duct 23 in the same manner as the solenoid actuated locking means 37 of the earlier described embodiment locks the wire in the second guide duct 24.
Alternatively the locking of the wire 12 can be obtained by means of locking of the feed rollers 20 or the reel 19 for rotation or in any other manner obvious to the skilled man.
The above described alternative manner of stretching the wire around the bars to be twisted together results in an even less complicated machine as the reel 19 for lashing wire 12 does not have to be displaceable but just rotatable.
If so required, the machine can be provided with means which, after lashing has been performed, bend down the twisted-together wire ends so as to avoid risks of injury. For this purpose, the operator can alternatively use one of the impact-resistant claws. The outer surface of this can then suitably be provided with a roller for interaction with the wire ends. In order to facilitate feed of the wire 12 into the inner cylinder 14 before a work operation, the inner and outer cylinders can be made with spring-loaded position-adjusting means which cause the inner cylinder always to return to exactly the same position relative to the outer cylinder after each completed work cycle.
The invention has been described above in connection with two embodiments shown in the drawings. However, as the man of art will readily understand, these can be varied in a number of respects within the scope of the claims as far as various detailed solutions are concerned. The elastic ball of the first embodiment can for instance be replaced by an element of a different design, which can interact with the scissors-like construction or another arrangement for securing the wire in the guide ducts. It is important that the arrangement brings about the requisite retention of the wire in order to make tight lashing-together of the reinforcing bars possible but allows the necessary length of the wire to be drawn past the arrangement in order to prevent excessive tension being built up in the wire, which may, for example, lead to the wire breaking. The expert in the field can propose alternative arrangements with this function.
Alternatively, this arrangement can be made in such a way that, instead of continually braking the drawing-out of the wire, it intermittently frees the wire completely for short periods of time and locks it completely during intermediate periods. Likewise, the design of the guide channel bridging the gap between the fixed claws can be varied in different respects.
The work sequences described above can be performed automatically after starting by pressing-in the activating button 2 under the control of an electronic unit (not shown). The programming of this control unit can be performed by the skilled man and has therefore been omitted so as not to prolong this description unnecessarily.
Number | Date | Country | Kind |
---|---|---|---|
0300687 | Mar 2003 | SE | national |
0302276 | Aug 2003 | SE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/SE2004/000391 | 3/17/2004 | WO | 00 | 10/19/2005 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2004/083559 | 9/30/2004 | WO | A |
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5682927 | Takahashi et al. | Nov 1997 | A |
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0829596 | Mar 1998 | EP |
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Number | Date | Country | |
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20060157139 A1 | Jul 2006 | US |