WO2008062213A2

WO2008062213A2 - Wire tying machines

Info

Publication number: WO2008062213A2
Application number: PCT/GB2007/004493
Authority: WO
Inventors: Ian David Coles; Graham Frank Barnes; Paul Michael Goater; Matthew John Wilson; Roger Frank Duckworth
Original assignee: Tymatic Limited
Priority date: 2006-11-24
Filing date: 2007-11-23
Publication date: 2008-05-29
Also published as: WO2008062213A3; GB0623468D0

Abstract

A machine for tying wire around one or more objects such as concrete reinforcement bars comprises twisting means (44) for twisting a length of wire around the bars. The twisting means are associated with a shaft driven by a motor for effecting the twisting. Means for gripping the wire during the rotation are operatively acted upon by a solenoid coil arranged around at least part of the shaft and adapted to move parallel to the shaft when an electric current is passed through the coil. The machine also comprises wire feed means (45) for drawing wire from a spool and feeding the wire around the bars. A single motor (40) is provided for driving the wire feed means (45) and the twisting means (44).

Description

WIRE TYING MACHINES

This invention relates to machines for tying lengths of wire around objects, particularly but not exclusively to bind together reinforcing bars for concrete.

A machine for binding concrete reinforcing bars together is taught in WO 2004/083559. hi this arrangement, a binding wire is drawn from a spool via a wire feed mechanism and is passed around the reinforcing bars which are to be tied, and then retracted to pull it tight. A clamping device arrangement is used to clamp the two ends of the wire and then to rotate a twisting head in order to twist the ends of the wire together and therefore form the binding.

The Applicant has appreciated that whilst the differing torque and speed requirements of the wire feed mechanism on one hand and the twisting head on the other hand has led to two separate motors being provided for these respective functions, packaging the two motors compromises the ergonomic balance of the machine and the physical bulk of the device. The two motors also require quite different control electronics and this increases cost and complexity of the electronics package. The Applicant has further appreciated that the clamping arrangement taught in WO 2004/083559 does not allow the independent operation of the wire clamps and the twisting head.

It is an object of the present invention to improve upon the arrangement described above and when viewed from a first aspect the invention provides a machine for tying wire around one or more objects, the machine comprising twisting means for twisting a length of wire around the object(s), the twisting means being associated with a shaft driven by a motor for effecting said twisting, and means for gripping the wire during said rotation, said gripping means being operatively acted upon by a solenoid coil arranged around at least part of the shaft and adapted to move parallel to the shaft when an electric current is passed through the coil. Thus it will be seen by those skilled in the art that in accordance with the present invention the wire clamping is controlled by means of a solenoid coil. This is advantageous since it means that clamping the wire and twisting the head may be carried out independently. For example, this allows the head to be parked in a given position without having to engage/disengage the wire clamp.

Furthermore, however, it will be noted that the arrangement provided in accordance with the present invention is contrary to the conventional implementation of a solenoid actuator which would normally have the core as the moving part. By having the coil as the moving/actuating part, the drive shaft for the head can be used as the core which simplifies construction of the solenoid and, for example, does not require anything to be located inside a hollow shaft, so allowing the shaft to be solid and so stronger. The coil could be provided as part of the head so as to rotate with the head, although preferably the coil is non-rotating and co-operates with the wire clamping means to be able to operate it at any rotational position. For example, the coil is conveniently provided with a housing, the lower end of which forms an annular cam surface which acts on one or more arms associated with the wire clamping mechanism. Preferably the coil is resiliently biased towards an actuating or non- actuating position so that current need only be applied to actuate or de-actuate the wire clamping mechanism respectively, but not for both. In the preferred embodiment the gripping mechanism is self-engaging so that the solenoid is operated to disengage it. In a conventional wire tying machine of the kind described above there would normally be provided a wire feed mechanism for drawing wire from a spool and feeding it around the object to be tied e.g. concrete reinforcing bars. Indeed, this is shown and described in WO 2004/083559. In accordance with the invention described so far, such a wire feed mechanism could be driven by a separate motor to that which is used to drive the twisting head, as is conventional. However, in accordance with some preferred embodiments of the present invention, a single motor is provided for driving the wire feed mechanism and the twisting means. This is clearly advantageous in reducing the cost of the device since only a single motor is required and the associated control electronics may be simplified. Secondly, the weight of the machine can be reduced. Thirdly problems associated with balancing the machine which arise from having to have two motors are reduced; and fourthly the ergonomics and overall size of the machine can be improved by not having to accommodate the second motor.

Since the speed and torque requirements of the wire feed means and the twisting means would normally be very different a gear arrangement is preferably provided between the motor and one or both of the wire feed means and the twisting means in order to provide the appropriate speed and/or torque. In this context the term "gear" should be interpreted broadly to cover any mechanical arrangement which is capable of altering the rotation speed of a rotary drive and is not limited to toothed cogs. In preferred embodiments an epicyclic gear arrangement is employed. Preferably the gear arrangement provides an annulus gear and a planet carrier that may be selectively prevented from rotating to transfer power to the twisting means and the wire feed means respectively.

Since in most cases the twisting means and wire feed means would not be required to be driven at the same times, a clutch or other drive disengagement means could be provided in the drive train between the motor and one or both of the twisting or wire feed means. Alternatively, the wire feed means could be configured so as to be disengageable from the wire when it was not required to feed the wire - e.g. when twisting the head. However, in preferred embodiments and in recognition of the fact that in such preferred embodiments only one of the twisting heads and the wire feed means needs to be driven at any given time, there is provided a drive train arrangement in which rotary drive may be moved between the twisting means and the wire feed means. In preferred embodiments a solenoid actuator is provided to select the required drive train.

Such arrangements are novel and inventive in their own right and thus when viewed from a second aspect the invention provides a machine for tying wire around one or more objects comprising wire feed means for drawing wire from a spool and feeding said wire around said object(s) and twisting means for twisting the wire around the object(s) wherein a single motor is provided for driving said wire feed means and said twisting means. The preferred features of this aspect of the invention are as set out above.

The selection between driving the wire twisting means and the wire feed means could be made manually, but preferably it made automatically by control means for the machine which is programmed to make the selection at the appropriate stage of the operation cycle. The drive selection could, for example, be effected by means of a solenoid actuator.

The motor could be electrically driven. For example it could be operated by a battery or via a power cord. In other embodiments the motor could be driven by a pressurised fluid, e.g. pneumatically. The aforementioned aspect of the invention is particularly advantageous when applied to hydraulic or pneumatic motors since these tend to be bulkier and more expensive than electric ones and hence the elimination of one is of particular benefit. In some preferred embodiments the twisting means comprises an aperture to accommodate the tie as it is formed in use.

Certain preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings:

Fig. IA is a perspective view of a wire tying machine described for reference purposes only;

Fig. IB is a view similar to Figure IA with a mounting bracket removed;

Fig. 2 is a sectional view through the machine shown in Figures IA and IB;

Fig. 3 is a view of the machine from underneath;

Fig. 4a is another sectional view showing the wire tensioned prior to twisting;

Fig. 4b is an enlargement of the circled part of Fig. 4a;

Fig. 5 is a perspective view of part of an embodiment of the invention;

Fig. 6 is a view similar to Fig. 5 with the gearbox casing removed showing a first driving position; Fig. 7 is an exploded view of the gearbox when in the first driving position of Fig. 6;

Fig. 8 is a view similar to Fig. 6 showing a second driving position;

Fig. 9 is a view similar to Fig. 7 showing a second driving position;

Fig. 10 is a side elevation of another embodiment of the invention with its housing removed;

Fig. 11 is another side elevation of the embodiment of Fig. 10 showing only the main drive components; and Fig. 12 is a sectional view through the shaft and solenoid coil. Referring first to Figs. Ia, Ib and 2 there is shown two perspective views and a sectional view of part of a tying machine which is described for the purposes of reference only. Certain parts such as the housing, handle, battery, controls and wire spool have been removed for clarity. The apparatus is shown situated over a junction where two steel bars 2 cross over each other at right angles. The steel bars 2 are intended to form a rectangular grid to be embedded in a concrete structure in order to reinforce it.

Sitting in use above the uppermost bar 2 is the rotary head of the apparatus 4. This includes a horizontal circular base plate 6 extending up from which is a channel 8 which is approximately semi-circular in vertical section and of approximately constant width in the orthogonal direction. In the centre of base plate 6 is a part- spherical depression 9. The underneath of the base plate 6 is shown in Fig. 3 from which it will be seen that on one side there is a narrow slot 10 corresponding to one end of the semi-circular channel and on the other side of the plate 6 corresponding to the other end of the channel is a funnel region 12.

Returning to Figs. Ia, Ib and 2, attached to the semi-circular channel 8 is the upper cylindrical portion of the head 14 which is rotatably mounted in the cylindrical portion 16a of a bracket member mounted to the housing (not shown) by a flange portion 16b (omitted from Fig. Ib). The upper head portion is supported by two rotary bearings 18. A toothed gear wheel, 20 is provided fixed at the top of the head to allow it to be driven by a motor 22 via a worm gear.

Extending through the gear wheel 20 into the open upper end of the head 4 is a solenoid assembly comprising a cylindrical outer tube 26 housing the coil and an inner plunger 28 which is able to slide vertically relative to the coil 26. At the bottom end of the plunger 28 is an actuating disc 30, which is used to operate wire gripping clutch mechanisms.

The internal construction of the head 4 will now be described. On the left hand side as seen from Fig. 2, there may be seen a pivotally mounted angled clutch lever 32. A pair of compression springs 36 act on the longer, upper arm of the lever 32 so as to bias the lever in an anti-clockwise direction in which the shorter, lower arm is pressed downwardly. Of course any number of springs might be used. To the right of the clutch lever 32 are a series of roller wheels 38a,38b,38c. A similar clutch lever is provided, displaced approximately 180 degrees around the head. This is not therefore visible in the sectional view.

To the left of the upper head portion 14 connected to the main bracket flange portion 16b is a wire feed inlet guide 40 which receives the free end of wire 46 which has been unwound from the spool (not shown).

Operation of the apparatus shown in Figs Ia to 3 will now be described. The apparatus is first brought down onto the uppermost of a pair of steel reinforcing bars 2 which are crossed at right angles. The operator may then commence the tying operation. The first part of this operation is to energise the solenoid coil 26 which pushes the plunger member 28 downwardly. This causes the actuating member 30 at the end of the plunger to be pressed downwardly onto the upper arms of the clutch levers 32 to press them down against the respective compression springs 36 and therefore raise the shorter, lower arms. This is the position which is shown in Figure 2.

Thereafter the main motor 22 is, if necessary, operated just long enough to rotate head 4 via the worm drive and gear wheel 24, 20 so that a channel for receiving the wire 46 is in correct alignment with the wire feed inlet guide 40. This is called the "park" position. The correct alignment may be detected simply by respective contacts provided on upper head portion 14 and the cylindrical housing 16a or wire inlet guide 40, although of course there are many other possibilities for this position detection.

Once the head 4 is in the "park" position, a separate motor (not shown) is operated to drive a wire feed roller (also not shown) that acts on the wire 46 to feed it from the spool through the wire inlet guide 40 and into the aligned channel in the upper head portion 14. The wire is fed in horizontally and encounters the first of the passive rollers 38a. The first roller 38a causes the wire to bend downwardly slightly so that it passes between the second and third rollers 38b, 38c. The relative positions of the three passive rollers 38a,38b,38c is such that when the wire 46 emerges from them it is bent so as to have an arcuate set. As the wire 46 continues to be driven by the wire feed roller, it encounters and is guided by the inner surface of the semi-circular channel 8. When the wire 46 emerges from the channel 8, its arcuate set causes it to continue to describe an approximately circular arc, now unguided in free space, around the two reinforcing bars. As the wire 46 continues to be driven, the free end will eventually strike the mouth of the funnel region 12 in the bottom of the base plate 6 and therefore be guided back into the semi-circular channel 8. However it is not guided back precisely diametrically opposite where it was issued from but rather slightly laterally offset therefrom. This allows the receiving means in the form of a further clutch lever (not shown) to be located next to the first clutch lever 32 which enables the apparatus to be kept relatively compact. As the free end of the wire re-enters the semi-circular channel 8, it encounters the second clutch lever. This can be detected by sensing a slight displacement of the lever or by a separate sensor such as a micro switch, Hall effect sensor or other position detection means.

Once the free end of the wire 46 is detected, the motor feeding the wire is stopped and therefore the wire does not advance any further. At this point the solenoid coil 26 is then de-energised which causes the plunger 28 to be retracted by a spring (not shown) which releases the two clutch levers 32 so that their respective compression springs 36 act to press their lower arms against the two ends of the wire loop and therefore hold the wire 46 in place. The wire feed motor is driven in reverse in order to apply tension to the wire loop which draws the wire in around the reinforcing bars 2. This may be seen in Figure 4a. Figure 4b shows detail of the clutch lever 32 on the feed side clamping the end of the wire 46. A similar arrangement clamps the other end of the wire as explained above. When the wire 46 is fully tensioned it will be seen from Fig. 4a that the two ends of the loop are pulled up almost vertically from their initial circular profile.

As the head 4 tries to start rotating at the beginning of the twisting operation the torque supplied by the motor 22 is sufficient to shear the wire at the point where it crosses from the inlet guide 40 to the upper head portion 14 without the need for it to be cut. If necessary an initial surge current (e.g. boosted by a charge stored in a capacitor) can be supplied to the motor 22 to deliver an initial spike in torque but this is not essential. With the wire thus broken, the head 4 begins to twist the sides of the loop together above the reinforcing bars 2.

The first one or two turns of the head are the most important in ensuring a tight binding. As will be appreciated, these initial twists are carried out under tension and therefore a very tight binding is achieved. As twisting continues, each successive turn is less important for providing a tight binding. As twisting continues the tension in the wire will increase. However, the shape of the rounded ends 32a of the clutch levers that bear against the ends of the wire mean that as the wire is pulled past, it will tend to be pulled slightly anti-clockwise (looking at the lever shown in Fig. 4a) and so increase the friction on the wire. This arrangement acts as an effective self-regulating mechanism to ensure that the wire can be drawn out by a measured amount. Since the area of mutual contact between the clutch lever 32 and the wire 46 is relatively small, effectively a point contact, the resistance force is less dependent on the co-efficient of friction than in previous arrangements. When a satisfactorily twisted binding is achieved, which could be after just one turn or even less than a complete turn, the free ends of the wire simply need to be twisted together to reduce the risk of snagging they pose. This is achieved by releasing the ends of the wire by once again energising the solenoid 26 to push the plunger 28 down and so disengage the lower faces 32a of the clutch levers from the wire 46. The remaining turns of the head are therefore carried out with the ends of the wire no longer clamped. The friction between the wire and the channel inside the head and the fact that the wire is required to bend as it is drawn out is sufficient to allow the rotary module to twist the ends. As sides of the loop are twisted together a stiff twisted section extends upwardly towards the base plate 6 and is accommodated in the spherical depression 9 which deflects the twisted section down again. This means that when the ends of the wire emerge from the bottom of the head 4, they will be pointing generally downwardly, i.e. towards the bars 2 rather than upwardly. The risk of snagging is therefore significantly reduced to the extent that the twisted section does not need to be manually knocked over to move the ends of the wire out of the way.

Once tying is completed the solenoid 26 is de-energised, allowing the plunger 28 to retract and therefore releasing the clutch levers 32. By this time the ends of the wire will have passed through so the clutch levers no longer bear on the wire. Rotation of the head 4 is stopped except to return it to the initial "park" position. A signal is then given to the operator that the tying operation has been successfully completed. This may, for example, involve illuminating a green LED or giving a beep.

The solenoid operated arrangement of described hereinabove has several advantages over the ball and scissors arrangement of WO 2004/083559. For example it allows the wire gripping means to be operated independently of driving the head. It also allows the head to be driven with more torque and is less prone to wear and tear.

An embodiment of the invention is shown in Figs. 5 to 9. This embodiment achieves the same function as the machine described above, although with some important differences. The Figures show only the main drive components of the machine - namely the motor, gearbox and head - as well as the wire feed mechanism and the wire guides. However things like the wire spool, casing, battery, control electronics etc. are all omitted for clarity.

The main components that can be seen are a motor 40, gearbox 42, twisting head 44, wire feed mechanism 45 (indicated only very generally) and wire guide jaws 47. Although the twisting head 44 is similar to the base plate 6 of the previously described machine, it will be noted that in place of the part-spherical depression is an aperture 44a which accommodates the tie as it is formed by allowing the tie to pass through the it and so into the head.

One of the key differences between this embodiment and the machine described previously is that only one motor 40 is provided. This could be an electric motor, e.g. powered by a battery to give a cordless machine, or hydraulically or pneumatically driven. The novel drive mechanism that gives rise to this is explained below with reference to Figs. 6 to 9.

Fig. 6 shows the gearbox casing removed. The gearbox contains an epicyclic arrangement coupled to the driveshaft of the motor 42 which comprises an annulus gear 48 and a first planet carrier gear 50 carrying five first planet gears 52. The driveshaft 54 of the twisting head 44 is coupled to the central first sun gear (not visible). The annulus gear 48 has an externally toothed section 56 which meshes with a gear 58 disposed at the end of a secondary wire feed mechanism driveshaft 60. A pinion gear 62 is disposed at the other end of this driveshaft 60 and drives the wire feed rollers (not visible).

As may be seen in Fig. 7, inside the annulus gear 48 is a further epicyclic gear set comprising five second planet gears 53 each of which is mounted on a common axle 55 with a respective one of the first planet gears 52. The second planet gears 53 mesh with the toothed inner circumference of the annulus gear 48. In the centre of the second planet gears 53 is a second sun gear 57 mounted to a second planet carrier 59 (see Fig. 9) carrying four third planet gears 61 which are driven (via a third sun gear, not shown) by the driveshaft of the motor 42.

A locking plate 64 is driven by a solenoid 66 between a forward and rear position to lock one of the annulus gear 48 and the first planet carrier 50, so preventing rotation thereof. As will be explained below, locking one of these two gears allows the other to be driven. Figs. 6 and 7 show the solenoid 66 in its rearmost position locking the annulus gear 48. As can be seen from Fig. 7, locking the annulus gear 48 means that the second sun gear 57 drives the second planet gears 53 to orbit around it which in turn causes the first planet carrier 50 to rotate. Rotation of the first planet carrier 50 is transmitted to the twisting head 44 by the first planet gears 52, the first sun gear (not visible) and the driveshaft 54. Figs. 8 and 9 show the solenoid in the forward position in which it is the first planet carrier gear 50 that is locked. This means that the second planet gears 53 cannot orbit around the second sun gear 57 but instead each rotates around its stationary axle 55 which rotates the annulus gear 48 to drive the wire feed mechanism driveshaft 60 via the toothed section 56 and cooperating gear 58. It can be seen therefore that simple actuation of the solenoid 66 allows drive to be transferred between the twisting head and wire feed mechanisms respectively. It can also be seen that the epicyclic gear sets give the relatively low speed, high torque drive required for the twisting head; whilst the pinion at the end of the secondary driveshaft 60 gives the higher speed drive required for the wire feed. The tying operation carried out by the embodiment shown in Figs. 5 to 9 is fundamentally the same as previously described. As will be appreciated from that description the wire feed mechanism and twisting head must be driven at mutually exclusive points in the tying cycle and the arrangement depicted in Figs. 5 to 9 ensures that that is necessarily the case. Moreover since only one motor is required rather than the two employed in the machine described above, the cost, complexity, weight, size etc. are all improved. A further embodiment is shown in Figs. 10 to 12. This embodiment too has the same arrangement of a single motor driving the head and wire feed and thus enjoys the attendant advantages explained above. However it also has a novel mechanism for operating the wire grip clutches in the head as will be explained below. Fig. 10 shows a side elevation of the machine (minus the outer casing).

Features in common with the previous embodiment are given the same reference numerals. There may also be seen the handle 68 which is formed as an extension of the main support frame 70. At the rear end of the handle 68 is a rechargeable battery pack 72. Also extending from the frame 70 parallel to the handle 68 is a support arm 74 for the wire spool 76.

The single motor 40 and gearbox 42 may be seen vertically oriented in Fig. 8, above the twisting head 44'. In this embodiment the twisting head 44' does not have the central aperture that the head of the previous embodiment did. Between the gearbox 42 and the head 44', around the head driveshaft 54 is a solenoid coil 78 to which a flying lead 80 is attached. It will be seen from Fig. 11 that a compression coil spring 82 is also disposed around the shaft 54 between the solenoid coil 78 and the head 44'. Fig. 12 shows the internal structure of the solenoid coil 78. It comprises an annular cylindrical casing 84. The radially inner wall of the casing acts as a former for the winding 86. The driveshaft 54 therefore acts as a core to the solenoid. The shaft is typically made of steel which is sufficiently ferrous to perform this role.

Apart from being attached to the coil spring 82, the solenoid coil assembly 78 is free to move axially along the driveshaft 54. Thus when an electric current is passed in the correct directions though the winding 86, the mutual magnetic force between the solenoid coil 78 and the solenoid core formed by the driveshaft 54 causes the coil assembly 78 to move down the driveshaft 54 against the coil spring 82. In an exactly analogous manner to the actuating member described above with reference to Figs. Ia to 4, the annular lower surface of the casing 84 presses on the ends of two wire gripping clutch levers 32 to cause them to release the force applied to the wire at the other ends of the levers inside the head 44'. Thus the solenoid 78 can be used to control the gripping force applied to the wire during the tying cycle in exactly the same way as previously described. It will be immediately appreciated that the embodiment shown in Figs. 10 to 12 is advantageous over that shown in WO 2004/083559 since it has the advantages of a solenoid arrangement set out above. However it is further significantly simpler and more robust than both WO 2004/083559 and the arrangement of Figs. Ia to 4 hereinabove since it employs an ordinary driveshaft for the head and a minimum of additional moving components. The embodiments described above are merely examples of how the aspects of the invention disclosed herein can be applied and many modifications can be made within the scope of the invention. For example the single motor and concentric solenoid arrangements can be employed individually, without the other, whilst still achieving benefit. Also for example there are many other drive arrangements that will be evident to the skilled person for implementing the single motor concept.

Claims

Claims:

1. A machine for tying wire around one or more objects, the machine comprising twisting means for twisting a length of wire around the object(s), the twisting means being associated with a shaft driven by a motor for effecting said twisting, and means for gripping the wire during said rotation, said gripping means being operatively acted upon by a solenoid coil arranged around at least part of the shaft and adapted to move parallel to the shaft when an electric current is passed through the coil.

2. A machine as claimed in claim 1 wherein the coil is non-rotating and cooperates with the wire clamping means to be able to operate it at any rotational position.

3. A machine as claimed in claim 1 or 2 wherein the coil is resiliency biased towards an actuating or non-actuating position.

4. A machine as claimed in any preceding claim wherein the gripping mechanism is self-engaging so that the solenoid is operated to disengage it.

5. A machine as claimed in any preceding claim comprising a wire feed mechanism for drawing wire from a spool and a single motor for driving the wire feed mechanism and the twisting means.

6. A machine for tying wire around one or more objects comprising wire feed means for drawing wire from a spool and feeding said wire around said object(s) and twisting means for twisting the wire around the object(s) wherein a single motor is provided for driving said wire feed means and said twisting means.

7. A machine as claimed in claim 5 or 6 comprising a gear arrangement between the motor and one or both of the wire feed means and the twisting means.

8. A machine as claimed in claim 6 comprising an epicyclic gear arrangement.

9. A machine as claimed in any of claims 6 to 8 wherein said gear arrangement comprises an annulus gear and a planet carrier that may be selectively prevented from rotating to transfer power to the twisting means and the wire feed means respectively.

10. A machine as claimed in any of claims 6 to 9 comprising a drive train arrangement in which rotary drive may be moved between the twisting means and the wire feed means.

11. A machine as claimed in claim 10 comprising a solenoid actuator to select the required drive train.

12. A machine as claimed in any of claims 6 to 11 comprising control means programmed to select between driving the wire twisting means and the wire feed means depending on the stage of an operation cycle.

13. A machine as claimed in any of claims 6 to 12 wherein the motor is adapted to be driven by a pressurised fluid.

14. A machine as claimed in any preceding claim wherein the twisting means comprises an aperture to accommodate a tie as it is formed during use.