WO2024200541A1

WO2024200541A1 - Tying apparatus

Info

Publication number: WO2024200541A1
Application number: PCT/EP2024/058298
Authority: WO
Inventors: Carlos Diaz De Rada Lorente; Carlos GANCHEGUI ITURRIA; Jason CALLEAR
Original assignee: Laing O'rourke Plc
Priority date: 2023-03-31
Filing date: 2024-03-27
Publication date: 2024-10-03
Also published as: GB2628665A; GB202304873D0

Abstract

An apparatus for tying rebar, comprising: means for feeding one or more loops of wire around a rebar node; a fixed carrier frame, a twisting head housed in the fixed carrier frame; means for controlling translation of the twisting head along its longitudinal axis; means for controlling axial rotation of the twisting head; and gripping means on one end of the twisting head configured to grip the loop(s) of wire; and a microcontroller configured to initiate the means for controlling translation and the means for controlling axial rotation of the twisting head, such that when the gripping means grip the loop(s) the twisting head translates into the fixed carrier frame away from the loop(s) and rotates axially in order to pull and twist the loop(s) thereby tying the rebar.

Description

TYING APPARATUS

Background

[0001] Metal or composite reinforcement bars can be cast into concrete to alter the material properties of the resulting construction. These reinforcement bars are conventionally steel bars, and referred to as “rebar”. Many different forms of rebar are manufactured, depending on the precise mechanical and/or aesthetic requirements of the concrete structure being formed.

[0002] To keep the rebar in place while the concrete is being poured around it, the rebar can be tied to neighbouring bars. This tying can use lengths of wire, wrapped around two or more rebars at a crossing point (or “node”), and twisted to lock the bars into place. The wire loops that make up a tie are ideally all equally tensioned. Loose loops reduce the clamping force from the tie and result in inefficiency leading to wire wastage.

[0003] Manual tying of wires around rebar is time consuming for a construction worker, requires a skilled labourer to perform and is often ergonomically challenging. The worker must ensure that the wire is of sufficient tightness, while also attempting to minimise the amount of wire wasted.

Summary

[0004] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0005] A first aspect provides an apparatus for tying rebar, comprising: means for feeding one or more loops of wire around a rebar node; a fixed carrier frame; a twisting head housed in the fixed carrier frame; means for controlling translation of the twisting head along its longitudinal axis; means for controlling axial rotation of the twisting head; and gripping means on one end of the twisting head configured to grip the loop(s) of wire; and a microcontroller configured to initiate the means for controlling translation and the means for controlling axial rotation of the twisting head, such that when the gripping means grip the loop(s) the twisting head translates into the fixed carrier frame away from the loop(s) and rotates axially in order to pull and twist the loop(s) thereby tying the rebar. In at least one example, the first aspect is arranged to tie the rebar automatically. [0006] By controlling the motion of the twisting head in the manner described it is possible to tie rebar in a safe, efficient and extremely effective manner. The apparatus thus enables considerable improvement in cost effectiveness, safety and quality of rebar tying. The act of gripping a loop of wire, and pulling the wire back while twisting, results in a stronger and more effective tie than twisting alone. Alternative arrangements seek to provide a more efficient tie by pulling back on the wire being spooled out from a wire feeder, before the wire is cut and also before any twisting operation begins. In such a way, the wire which is pulled back can be used in subsequent tying operations. However, such a “pull-back” system adds an additional complexity to the apparatus, and so tool reliability may be negatively impacted. Further, since a tying apparatus must be matched to the sum of the diameters of the rebars in the node being tied, this alternative arrangement is more suited to the tying of smaller diameter rebar. The tying of smaller diameter rebar uses less wire, as a smaller length of wire is required to encircle the node. Therefore there is less wire to pull back. If there is more wire to pull back, for example in the case of a node comprising larger diameter rebars, then management of the returning wire can add significant complication to the operation of the tying arrangement mechanism.

[0007] Preferably the means for feeding comprises: a guideway with a curved guide; a receiving guideway; a wire feeder operable to feed the one or more loops of wire around the rebar node following the curved guide. By using a curved guide the wire is guided towards the receiving guideway to form the loops by the action of the wire feeder. The receiving guideway facilitates formation of the loops. Thus there is an efficient, safe and effective way to form the loops.

[0008] Preferably the apparatus comprises a trigger mechanism operable to control when one part of the apparatus (such as the twisting head) is free to move axially relative to another part of the apparatus. Moving axially is moving along a longitudinal axis of the apparatus. By using a trigger there is a compact, efficient mechanism for controlling when one part of the apparatus is free to move axially relative to another part. Alternative approaches using twisting motion rather than a combination of axial and twisting motion produce ties of inferior quality.

[0009] Preferably the means for controlling translation of the twisting head and the means for controlling rotation of the twisting head comprise: a carrier housing sprung from the fixed carrier frame, such that the carrier housing is urged parallel to an axis of rotation of a twisting head; a ratchet mechanism, a motor operable to rotate a spindle with a ball screw in a first direction and a second direction, wherein the spindle is constrained to move axially with respect to the twisting head, and the carrier housing is constrained to move axially with respect to the fixed carrier frame. [0010] The combination of the sprung carrier housing, ratchet mechanism and spindle with ball screw gives a compact arrangement which is safe and robust. The combination facilitates a light weight design so that the apparatus is usable as a handheld apparatus.

[0011] Preferably the apparatus comprises a wire cutter and a wire cutter actuation means configured such that the axial movement of the twisting head causes the wire cutter to cut the wire. This wire cutting automation mechanism is found to be particularly safe and effective and to facilitate efficient use of wire.

[0012] Preferably the gripping means comprises jaws and wherein the jaws are retractable. Using retractable jaws facilitates safety.

[0013] Preferably the or each rebar in the rebar node has a diameter of between 25-50mm. Thus the apparatus is operable even for larger diameter rebar which are particularly difficult to handle and tie due to their weight, size and the abrasive surface of the rebar. A rebar considered “large” may have a 40mm nominal diameter. Owing to the ribs on the outside surface of the rebar, the effective diameter of such a rebar may be 46mm.

[0014] Preferably the receiving guideway comprises a hinge operable to open to accept the rebar node, and then close such that the guideway and the receiving guideway at least partially enclose the rebar node. Using an enclosure in this way facilitates safety since the moving parts used to do the tying are away from an operator or other items in the environment due to the enclosure.

[0015] Preferably the wire feeder is operable to feed a predetermined length of wire. This facilitates efficient use of wire and reducing wasted wire.

[0016] Preferably the predetermined length of wire corresponds to a predetermined number of loops around the node. This facilitates efficient use of wire and reducing wasted wire.

[0017] Preferably the predetermined number of loops is determined according to a sum of rebar diameters in the rebar node. This facilitates efficient use of wire and reducing wasted wire.

[0018] Preferably the apparatus comprises a wire spool operable to provide wire to the wire feeder. This facilitates safety and robustness since moisture, dirt and dust from a building site is less likely to penetrate the wire spool.

[0019] Preferably the wire spool is on different plane from the one or more loops of wire. Such an arrangement gives compactness which aids hand held use of the apparatus. In such a case, the bend in the wire must be managed such that any natural tendency to bend is in the plane of the loop.

[0020] Preferably the wire cutter cuts the wire using a shearing action. Using a shearing action for cutting the wire is found to be safer and more effective than using compressive or other actions.

[0021] In an aspect there is a method of tying rebar using a motorised apparatus, the method comprising: feeding one or more loops of wire around a rebar node; using gripping means on one end of a twisting head housed in a fixed carrier frame to grip the loop(s) of wire; and using a microcontroller, initiating means for controlling translation of a twisting head along its longitudinal axis and triggering means for controlling axial rotation of the twisting head, such that when the gripping means grip the loop(s) the twisting head translates into the fixed carrier frame away from the loop(s) and rotates axially in order to pull and twist the loop(s) thereby tying the rebar.

[0022] The method is efficient, and gives reliable, repeatable results.

[0023] Preferably the method comprises attaching the motorized apparatus to a backpack and powering the motorized apparatus using the backpack. In this way hand held operation of the apparatus is facilitated.

[0024] The preferred features may be combined as appropriate, as would be apparent to a skilled person, and may be combined with any of the aspects of the invention.

Brief Description of the Drawings

[0025] Embodiments of the invention will be described, by way of example, with reference to the following drawings, in which:

[0026] Figure 1 shows a cross section of part of a tying apparatus, showing a wire being unspooled;

[0027] Figure 2 shows a cross section of part of the tying apparatus, showing the wire being cut;

[0028] Figure 3 shows a cross section of the tying apparatus surrounding a rebar node;

[0029] Figure 4 shows the tying apparatus including an optional operator support;

[0030] Figure 5 shows a cross section of the twisting mechanism of the tying apparatus; [0031] Figures 6A-6G show an activation process for the twisting mechanism of the tying apparatus;

[0032] Figure 7 shows a rachet mechanism for the twisting mechanism of the tying apparatus;

[0033] Figure 8 shows an external view of the rachet mechanism for the twisting mechanism of the tying apparatus;

[0034] Figures 9A-9E show an external view of the steps taken to perform a twisting operation;

[0035] Figures 10A-10E show a cross-sectional view of the steps to capture, clamp and pull back a wire loop;

[0036] Figures 11A-13B show a flow diagram demonstrating the logic process of the tying apparatus.

[0037] Common reference numerals are used throughout the figures to indicate similar features.

Detailed Description

[0038] Embodiments of the present invention are described below by way of example only. These examples represent the best ways of putting the invention into practice that are currently known to the Applicant although they are not the only ways in which this could be achieved. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[0039] Figure 1 shows a cross section of part of a tying apparatus, showing a wire 1 10 being unspooled using an automated wire feeder 115. As the wire 110 is fed out using the wire feeder 115, it is forced around a curved guideway 105. The shape of the guideway 105 may impart to the wire 1 10 a curved shape and/or adjust the two dimensional plane on which the loop is formed. Alternatively or additionally, the 110 wire coming off the spool may have a natural curve which has already been imparted. The process of giving the wire its desired shape may comprise straightening the wire as it is unspooled by bending it and then straightening it about a set of vertical and horizontal rolls, and then using rolls to impart the desired curvature.

[0040] As the wire 1 10 passes along the guideway 105, it passes through a wire cutter 120. The wire cutter 120 of this example is in the form of a ring, and the wire 110 to be cut passes through the gap in the middle of the ring. The wire 1 10 passes from wire feeder 115 through the wire cutter 120 before passing along guideway 105. Even in the use case where multiple loops are made, the wire only passes through the cutter once. A wire guide tube 140 may be provided to ensure the wire 110 passes successfully from the wire feeder 115 to the wire cutter 120. The wire cutter 120 is connected to a twisting head 125 via a linkage 130, 135. In this example, the linkage comprises two levers, a first lever 130 and a second lever 135, although other arrangements are possible.

[0041] As shown in Figure 2, the twisting head 125 is movable axially, along its longitudinal axis. As the twisting head 125 moves axially towards the wire cutter 120, a first end of the first lever 130 is also moved towards the wire cutter 120. This movement of the first end of the first lever 130 causes the first lever 130 to pivot, moving a second end of the first lever 130 to move away from the wire cutter 120. A first end of the second lever 135 is connected to the second end of the first lever 130. The movement of the second end of the first lever 130 away from the wire cutter 120 thereby pulls the entire second lever 135 away from the wire cutter 120.

[0042] As the second lever 135 is pulled away from the wire cutter 120, the wire cutter 120 cuts the wire 1 10 via a shearing action. The remaining wire stays substantially within the tying apparatus, and may be unspooled using the wire feeder 115 for subsequent tying operations.

[0043] Figure 3 shows a cross section of the tying apparatus surrounding a rebar node 315. A rebar node 315 is a point at which two or more rebars cross and/or intersect. I n this example, the rebar node 315 comprises two rebars at substantially 90 degrees to each other and visible as two ovals in Figure 3. In Figure 3 the cross sections of the rebar appear oval because of the position of the plane of the cross section with respect to the rebar node 315. The rebars are substantially cylindrical steel bars in this example, optionally with a sum of their diameters being between 50 to 95mm. Wire 110 from a spool 320 is driven round the rebar node 315 by the wire feeder 1 15. The curved guideway 105 and a receiving guideway (which may be hinged) 310 ensure the wire 1 10 forms approximately circular loops around the rebar node 315.

[0044] A gap 305 between the fixed guideway 105 and the receiving guideway 310may be present and of variable distance, according to the configuration of the guideway 105 and the receiving guideway 310. When the receiving guideway 310 is hinged and the hinge is in an “open” position, the tying apparatus can be located over or removed from a node 315. When the hinged receiving guideway 310 is in a “closed” position, a substantially continuous guide is provided around the node 315. In one or more examples, the hinged guideway 310 is permanently fixed in the “closed” position. Any means for moving the receiving guideway between an open position for accepting a rebar node and a closed position for enclosing a rebar node is usable. [0045] In one or more examples, the guideway 105 is relatively narrow in order to direct wire 1 10 across the gap 305, and the hinged receiving guideway 310 is relatively wide. The hinged receiving guideway 310 may then catch and direct the wire end 110 that has crossed the gap 305 back along the guideway 105, thereby forming a continuous loop of wire.

[0046] On its route round the node 315, the wire 110 is guided to pass through a vacant space adjacent two openable fingers (also referred to as “jaws” or “claws”), the openable fingers themselves adjacent a first end of the twisting head 125. Alternatively or additionally, the wire 110 is guided to pass through a vacant space between two or more projected lines extending from the fingers when opened.

[0047] In at least one use case, a “full loop” is considered to have been formed when the wire 110 has passed through the space adjacent the fingers for a second time. In one or more examples, the end of the wire 110, which passed first through the space adjacent the fingers, extends no less than 20mm beyond the fingers.

[0048] The length of wire 1 10 required to create a full loop may be calculated according to the sum of the effective diameters of the rebars in the rebar node 315 to be tied. Alternatively or additionally, the length of wire 110 required to create a full loop may be calculated according to the position of the guideway 105 and the receiving guideway 310. In one or more examples, a 40mm diameter rebar is used. Such a rebar has an effective diameter of approximately 46mm, owing to one or more ribs present on the surface of the rebar. If the wire length is based on the nominal diameter only, then the length would be insufficient to pass around the node 315. Further, in practice, a clearance may be required between the rebar node 315 and the wire 110, for example if the rebars are not touching. Wire length may be determined from the length of the guideway, and may be shorter if the wire is not in contact with guideway for the entirety of its length.

[0049] If only a single full loop is required, the wire feeder 115 is stopped once the correct length of wire 110 has been fed out. If multiple loops are required, for example if a stronger connection between the rebars in the rebar node 315 is required, the wire feeder 115 can continue until the length of wire necessary to form the correct number of complete loops has been fed out.

[0050] Additionally or alternatively, the wire may be fed from a utility backpack. In such an example, the wire may have been straightened at the back pack end in order to aid its passage down the connecting umbilical. The wire spool 320 may be replaced by a special spool around which wire 1 10 loops. The diameter of spool 320 may be selected to impose a permanent bend in wire 110 and in the correct plane to assist with the formation of the loop around the node 315. The special spool may incorporate one or more guides to control the wire position and to control the wire tension in the wire, such that a predetermined curvature is consistently achieved. Alternative means of providing the curvature in the wire may be used either additionally or alternatively.

[0051] Figure 4 shows an external view of the tying apparatus including an optional operator support 405. The centre of gravity of the tying apparatus may be in front of the user’s hand, hence, in use, generating a bending moment on the user’s wrist. As a result, the operator support 405 pushes up against the user’s arm, creating a force couple between the grip and the operator support 405, thereby reducing the strain on the user’s wrist. The tying apparatus may further be equipped with a protective cover 410, which provides protection for the mechanism within against environmental factors such as dust and rain.

[0052] Figure 5 shows a more detailed cross section of the twisting mechanism of the tying apparatus. The twisting head 125, comprising the first and second fingers, is mounted on a carrier housing 510. Substantially enclosed within the carrier housing 510 is a shaft 505 with a screwed thread. The screwed thread may comprise a ball screw, a lead screw, or any other screw arrangement. The shaft 505 is driven by a motor with integral gearbox 520 . In one or more examples, an output shaft of the gearbox 520 may be connected to the shaft 505 via one or more gears 525 The twisting head 125 is restrained from free rotation. Rotation of the shaft 505 then causes an axial movement of the twisting head 125 along its longitudinal axis. The motor 520 may be an electric motor, optionally a DC electric motor.

[0053] The length of the wire 110 fed from the wire feeder 1 15 is monitored and feeding is stopped when the free end of the wire is in a predefined zone relative to the fingers on the twisting head 125. As the twisting head 125 moves forward, an inner shaft connected to the fingers moves forward as well under spring pressure until the inner shaft reaches the limit of its travel. The twisting head 125 continues to move, but as the inner shaft is now stopped, the differential linear action acts to close the fingers. Further axial movement of twisting head 125 activates the wire cutter 120, and wire 110 is cut from the spool at a point before the wire passes through the fingers.

[0054] Once the wire 110 is cut, the twisting head 125 is pulled back in an axial movement. The pulling back of the twisting head 125 tightens the loops of wire 110 around the rebar node 315. This pulling back motion is enabled by the trigger mechanism pulling out a pin stopping relative axial movement between the fixed carrier frame 515 and the carrier housing 510. As well as the axial movement, the twisting head 125 also rotates to form the loops of wire into a tie by twisting. The effect of forming the tie is to reduce the distance between the fingers and the node 315. The twisting head 125 can move forwards as the tie is made, maintaining the necessary conditions for forming a high quality wire tie.

[0055] Towards the end of the process of making the tie, the torque required to twist the wire 1 10 increases. Control of the torque applied to the twisting head 125 enables the clamping force applied to the tie to be adjusted. When the required torque has been reached, the twisting head 125 may be stopped, the fingers retracted, and the tying apparatus removed from the node 315. The result is a wire tie around the rebars which form the rebar node 315, which secures the rebars to each other. The twisting head 125 may then be the moved to its forward position. In various example, the required torque is detected using sensors and the twisting head stopped automatically.

[0056] In Figure 6A, a starting stage of the tying operation is shown. The trigger 615 is engaged in the carrier housing 510 of the twisting head 125 using a spring 610. The motor 520 is rotated forward such that the cog 630 is in contact with the forward rotation preventing ratchet, thereby aligning the fingers 620’, 620” over the loop of wire to be twisted (not shown).

[0057] The trigger of at least one example is a sprung loaded pin with at least one hole passing through it. A crank 605 passes through the hole, the crank 605 arranged to move with the twisting head 125. The crank 605 has a slope on its surface, so as to lift the pin once the axial movement has reached a predetermined distance, for example a sufficient distance so as to have fully closed the fingers and cut the wire. This allows the whole of the carrier housing 510 to spring back, as required for the twisting and pulling stages of the tying operation. The crank 605 may comprise a screw mechanism at an end remote from the trigger 615, to allow adjustments to the length and operation of the crank 605 as required, for example to adjust the stroke and limit of travel.

[0058] The housing stop 640 does not rotate, and instead runs in a slot in the non-rotating twisting head housing 510, and moves axially with the twisting head 125. The non-rotating housing stop 640 may attach to the rotating twisting head 125 via a bearing. The housing stop 640 may itself be stopped using a step built in to the fixed carrier frame 515. Under reverse rotation of the motor 520, for example when opening the fingers 620 and withdrawing the twisting head 125 to a start position, this has the effect of stopping backward movement of the twisting head 125 and instead forcing forward movement of the carrier housing 510 instead. Thus, the springs are pre-compressed. In one or more examples, this functionality is instead or additionally provided via the linkage 130, 135 to the wire cutter 120 by only allowing the connected housing stop 640 to move back by a fixed amount. [0059] Figure 6B shows a second stage of the tying operation. In this stage, forward rotation of the motor 520 moves the twisting head 125 forward. The twisting head 125 cannot rotate owing to the forward rotation prevention ratchet mechanism, and hence the result is forward motion on the screw thread of the twisting head 125. The fingers 620’, 620” remain open to capture the loop of wire (not shown) which has been unspooled around the rebar node to be tied.

[0060] At the stage of Figure 6C, the finger activation rod 635 reaches end of its available free travel. This causes the fingers 620 to start to close around the loop of wire to be twisted (not shown). The twisting head 125 at this stage is still prevented from forward rotation by the ratchet arrangement in physical contact with the cog 630. The slope on trigger activator part of the crank 605 is just engaging with the trigger 615.

[0061] Figure 6D shows a stage in which the fingers 620 are fully closed around the wire loop (not shown). The anti-rotation cog 630 has just left physical contact with the forward rotation preventing ratchet, so that the twisting head 125 can now start to rotate. The carrier housing 510 of the twisting head 125 is now in a position to spring back, which is represented in the Figure as a left direction.

[0062] At the stage of Figure 6E, the carrier housing 510 of the twisting head 125 is sprung back, which is represented in the Figure as a left direction. The motor 520 continues to drive forward, rotating the twisting head 125, as the ratchet is still in the necessary position on the cog 630. The fingers 620’, 620” remain closed around the wire loop (as shown). In one or more examples, if the wire loop to be twisted requires shortening, the twisting head housing assembly can move forward (represented as a right direction on the Figure).

[0063] At the stage of Figure 6F, the wire tying process has concluded, and a twist in the wire loop (not shown) has been formed. The motor 520 is set in a reverse direction compared with the rotation of the stages of Figures 6A-6E. The twisting head 125 is prevented from rotating in reverse by the physical contact of the reverse rotation preventing ratchet on the cog 630, hence resulting in axial movement of the twisting head 125. The twisting head 125 is prevented from moving back (represented as left on the Figure) owing to a physical stop, hence the twisting head housing 510 moves forward (represented as right on the Figure). This forward movement compresses the springs that act to move the twisting head housing 510 backward when the trigger is released.

[0064] At the stage of Figure 6G, the twisting head housing 510 continues to move forward (represented as right on the Figure) under reverse motor rotation until the trigger pin 615 engages. At this point the motor 520 stops. In one or more examples a subsequent forward rotation of the motor 520 is performed in order to align the fingers 620’, 620”. At this point, the configuration of the tying apparatus is the same as the start condition of Figure 6A.

[0065] A first finger 620’ adjacent the first end of the twisting head 125 may be configured to interleave with a second finger 620” adjacent the first end of the twisting head 125. Once the wire feeder 110 has stopped feeding out the wire 110, the one or more loops formed by the wire 1 10 may be allowed to settle for a predetermined amount of time.

[0066] Once the one or more loops have been clamped by the fingers, the wire 110 may be cut by a shearing action. This is also actioned by the forward movement of the twisting head 125. The forward movement of the twisting head 125 operates the first lever 130, which via the linkage of the second lever 135 rotates the wire cutter 120 thereby causing the wire 110 to be cut according to a shear action.

[0067] Figure 7 shows a more detailed view of a rachet mechanism for the twisting mechanism of the tying apparatus. In this example, two rachet mechanisms are provided: a lower rachet 705 and an upper rachet 710.

[0068] In Figure 7A, the twisting head 125 is in a “back position”, also referred to as a “starting position”. In this position, the twisting head 125 is operable to rotate in a first direction only. Restraining the twisting head 125 from rotating in the second direction causes an axial movement of the twisting head 125. This axial movement is a forward movement if rotation of the shaft 505 is anti-clockwise and the upper rachet 710 is engaged. This axial movement is a backward movement if rotation of the shaft 505 is clockwise and the lower rachet 705 is engaged. The engagement of the upper rachet 710 or the lower rachet 705 is a function of where along the rachets the cog 630 is located.

[0069] In Figure 7B, the twisting head 125 is moving forwards. Mid-travel the twisting head cog 630 is engaging with both the lower rachet 705 and the upper rachet 710, which results in a forward axial motion but no rotational motion. In Figure 7C, the twisting head 125 is in a “front position”, and the fingers 620 are in position to perform the tying operation. The lower rachet 705 is engaged with cog 630, which allows the twisting head 125 to twist in a second direction only, where the second direction is the reverse of the first direction. In the final stage of Figure 7D, the twisting head 125 is moving backwards to reset itself to the starting position. As in Figure 7B, both the lower rachet 705 and the upper rachet 710 are engaged, limiting the twisting head 125 to axial movement only and no rotational movement. [0070] A shaft is linked directly to the motor 520 and rotates whenever the motor 520 rotates. The twisting head 125 is restrained from free rotation by the ratchet system. This causes the twisting head to move forwards as the shaft rotates. As the shaft moves forward the cog 630, also referred to as a tooth, attached to the twisting head 125 slides along the pawl of the rachet. At a predetermined position the cog 630 is no longer on the pawl, and the twisting head 125 has moved to its extreme position. The twisting head 125 is no longer prevented from rotating by the ratchet system. Three other actions happen as the twisting head 125 moves out: (i) the fingers are closed; (ii) the wire is cut; and (iii) the trigger pin holding assembly 510 out is released allowing it to spring back.

[0071] Figure 8 shows an external view of the rachet mechanism of the tying apparatus. In this view, the rachet mechanism, comprising the lower rachet 705 and the upper rachet 710, is protected by a cover 805. The motor 520 is, in use, positioned below the rachet mechanism, and provides rotational movement via the integral gearbox and one or more gears 525 and the shaft.

[0072] The tying apparatus comprises a microcontroller or other processing circuitry for controlling the tying apparatus. The tying apparatus has one or more sensors which send data to the microcontroller as now explained. Additionally or alternatively, a microprocessor is used to parse one or more packets of the data from the one or more sensors.

[0073] Figures 9A-9E show an external view of the steps taken to perform a twisting operation. In Figure 9A, as in Figure 7A, the twisting head 125 is in a “back position”, also referred to as a “starting position”. The fingers 620 are in an “open” position, which in at least one example comprises two fingers 620 pointing in the same longitudinal direction as the substantially cylindrical twisting head 125, and operable to receive a wire loop.

[0074] In Figure 9B, the twisting head 125 has moved forwards, using the mechanism as described in relation to Figure 7B. The forward axial movement of the twisting head 125 has extended the fingers 620 away from the body of the tying apparatus. The fingers 620 themselves remain in the open position of Figure 9A.

[0075] In Figure 9C, the twisting head has fully reached the “front position” of Figure 7C. The fingers 620 are moved towards a “closed” position to grasp a wire loop (not shown). In Figure 9D, the fingers 620 have moved into a fully closed position, grasping a wire loop (not shown) therebetween. In at least one example, this closed position comprises two fingers 620 being folded inwards towards each other, such that a free end of a first finger 620 is adjacent a hinged end of a second finger 620, and correspondingly a free end of the second finger 620 is adjacent a hinged end of the first finger 620. The free ends of the fingers 620 are pointed radially away from the substantially cylindrical twisting head 125.

[0076] In Figure 9E, the carrier housing 510 moves axially backwards, thereby pulling with it the twisting head 125 and the closed fingers 620. In such a way, a wire loop held by the fingers 620 would be tightened as it was twisted. Twisting head rotation continues until a predefined torque is reached. This concludes the tying operation.

[0077] Figures 10A-10E show a similar series of operations as Figures 9A-9E, but using a cross-sectional plan view of part of the apparatus. Figure 10A shows the twisting head 125 in the “back position”, and the fingers 620 in the “open” position. There is also shown a spring 625 connecting a central core of the twisting head 125 and the shaft 505.

[0078] In Figure 10B, the twisting head 125 has moved forwards. The forward axial movement of the twisting head 125 has extended the fingers 620 away from the body of the tying apparatus, and decompresses the spring 625. The fingers 620 themselves remain in the open position of Figure 10A. The de-compression of the spring 625 urges the twisting head 125 towards the carrier housing while it is held in the “front position”.

[0079] In Figure 10C, the twisting head has nearly reached the “front position”. The fingers 620 are moved towards a “closed” position operable to grasp a wire loop (not shown). In Figure 10D, the twisting head has reached the “front position” and the fingers 620 have moved into a fully closed position, grasping the wire loop (not shown) therebetween. In Figure 10E, the carrier housing 510 moves axially backwards, thereby pulling with it the twisting head 125 and the closed fingers 620. In such a way, a wire loop held by the fingers 620 would be tightened as it was twisted. Twisting head rotation until the required torque is reached concludes the tying operation.

[0080] Figures 11A-13B show a flow diagram demonstrating an example logic process implemented by the microcontroller. In one or more examples, the tying apparatus is equipped with one or more sensors, also referred as “detectors”. The sensors may include one or more of the following:

• DHpbar is a variable holding values from a position sensor in the tying apparatus which detects when the tying apparatus is in the correct position for a tying operation to begin.

• DHFeederspin is a variable holding values about use of the motor 520, and specifically its use in relation to the wire feeder 115. If the wire feeder 115 is spinning then that is a sign that the tying apparatus is working as intended. • DHCoilspin is a variable holding a value indicating whether the wire is successfully passing through the wire feeder 115 and forming a coil (also referred to as a “loop”) around the rebar node 315. Sensors in the wire feeder provide input values to the variable DHCoilspin. DHFeederspin and DHCoilspin may therefore be used in conjunction to check that wire is available on the spool 320 and also that the wire has not jammed within the mechanism of the tying apparatus.

• DHWirecover is a variable holding values from a sensor which detects that one or more of the necessary protective panels and casings 410 are closed, in order to protect the mechanism of the tying apparatus and also help ensure operator safety.

• DHGripper is a variable holding values from a sensor which indicates that the hinged receiving guideway 310 is properly closed, to guide the wire to form a loop around the node 315.

• DHBackwards and DHForwards are variables holding values from sensors that detect the position of the twisting head 125. Correct operation of the tying apparatus requires either a forward or backward position of the twisting head 125, and if the twisting head is not in the correct position for a specific operation then the tying process must be halted.

• The Button Run Cycle (PCylerun) is an electric signal given to indicate the start of a tying procedure.

• QmFeeding is a variable holding a value from a sensor which is designed to count the pulses of the wire feeder 1 15. Each pulse represents a predetermined length of wire 110 leaving the wire feeder 115. Depending on how many loops are determined to be required, the number of pulses and hence length of wire 110 can be accurately measured out.

• QmTightEnable is a variable holding a value from a sensor which detects whether the wire twisting operation is ready to be performed. When QmTightEnamble equals one, the microcontroller is used to activate one digital output to enable the controller of the motor in order to be able to spin the motor.

• QSolenoidfeederstopper is a variable holding values from a sensor which detects whether the wire 110 has been correctly cut by the wire cutter 120, and may be located in the guideway 105. The solenoid feeder stopper itself is a mechanism that prevents the spool 320 from keep spinning and unwinding in the case that the wire feeder 115 gave it too much inertia while feeding. When the wire feeder 115 stops, the solenoid is activated and pushes a lever that locks with a set of teeth of the spool 320. The solenoid remains activated until the stabilization timer reaches a predetermined time point. A timer is used to ensure that the spool 320 is stopped and that the wire which is already around the rebars stop moving so that the fingers will successfully clamp and twist all the wires of the loop.

• LED_BUILTIN on a motherboard of the microcontroller comprises an analogue output, which is ATightCCW. This signal drives the motor 520, and includes the speed as well as direction. ATightCCW can also include a “stop” signal, to stop the motor 520 from moving. When AthightCCW = zero, a microcontroller sends 0 amps through an analogue output so the controller of the motor knows that the motor has to be in a stopped position. When AthightCCW = positive, the microcontroller sends a positive current through an analogue output so the controller of the motor makes the motor turn in a first direction. This positive current may be the maximum current possible according to the controller’s configuration so the motor spins on its nominal rpm and with nominal torque. When AthightCCW = negative, the microcontroller sends a negative current through the analogue output so the controller of the motor makes the motor turn in a second, opposite, direction. As in relation to the positive current, in one or more examples the maximum negative current possible is sent according to the controller’s configuration so the motor spins on its nominal rpm and with nominal torque.

[0081] The flow chart of Figures 11 A and 11 B begins at the “start”. From stage 1 to stage 2, a series of checks are performed using one or more of the sensors referenced herein. PCycleRun refers to the operator switch, which is pressed by the operator, optionally in the form of a trigger, to begin the tying operation. If the operator switch has been pressed, i.e. if PCycleRun = one, then an instruction to proceed with the tying operation has been received by the tying apparatus, and the tying procedure can commence.

[0082] QmFeeding is then set to one. If an error is detected regarding the pulses counted out from the wire feeder 115, then a failure status is confirmed and the tying operation ceases. If the number of pulses is less than the number needed, then more wire 1 10 can be fed out until the number of pulses (corresponding to the length of wire 110) is greater than or equal to the amount of wire required for that particular tying operation. [0083] At the next stage the wire feeding is stopped, by setting the value of QmFeeding to zero, and the value of QSolenoidfeederstopper to one. This step leads to stage 3 as marked on Figure 9, which corresponds to the stage 3 as marked at the beginning of Figure 10A.

[0084] Figures 12A and 12B begins with providing some time for the wire 110 to stabilise. When a loop is formed from the wire 110 being guided around the guideway 105 and the hinged receiving guideway 310, there may be some residual movement of the wire 110. By allowing the wire 110 to settle, the fingers 620 may be able to grab the wire 110 more consistently to form a successful tie.

[0085] QMTightEnable is then set to one, and an instruction is sent to begin turning the motor 520 in the first direction. If an unexpected value occurs, for example ATightCCW is set to zero following the movement of the shaft 505 to a forward position, then a failure status is marked and the motor stops.

[0086] There is then a consideration as to whether the cycle start is equal to one, to indicate that a tying operation is to start. If the cycle start is not equal to one, then the cycle start is set to one, and the tying process continues at stage 5, shown on Figure 11. If the cycle start is already set to one, then the process continues to stage 4.

[0087] Cycle start == 1 is an IF conditional, whereas cycle start = 1 is an assignation. When the tying apparatus of one or more examples is powered on, a start cycle is performed to ensure that the mechanism is in the correct position and also to make sure that any remaining wire from a previous tying operation has been cut. This cycle is the same as a tying cycle with the exception that the tightening phase is not performed. Therefore, when the tying apparatus is powered on, it checks that the start cycle has been done already (cycle start == 1 "IF cycle start==1 THEN...."). If the start cycle has not been done, the cycle start is set to 1 , which will include performing all the predetermined steps of the tying operation except for the tightening step. If the start cycle has been done already, then the tying operation just continues performing the predetermined steps of the program.

[0088] The assignation "cycle on = 1" may be considered interchangeable with "cycle start = 1". The assignation "cycle on == 1" may be considered interchangeable with "cycle start == 1"

[0089] Between stage 4 and stage 5, the motor 520 current is monitored. The current is a constant, being limited to a predetermined value resulting in a constant torque being reachable by the motor. During the tightening cycle, for a motor speed of zero, it means that the apparatus is facing a torque greater than the maximum torque reachable. So the apparatus is in a position to follow the usual sequence as it is performing at the desirable torque. The motor continues until either it is timed out or it stops. If it does not reach the torque (motor speed = zero) in the expected time, an error is output. For the same wire diameter, which results in the same number of loops, the current and torque are predetermined constant values.

[0090] For a given number of loops and wire diameter, there is a corresponding current that will result in an acceptable tie. This current is set to a constant by the controller. For a given torque this will result in a given motor speed between 400 and 450 rpm. If motor speed exceeds 450 rpm, then a loop is not being made or the twist has broken. If the motor speed is less than 400 rpm, then the torque has exceeded its pre-set value and the tie is complete.

[0091] The TimeOutTight is a timer which will stop the motor and give a failure code if the tightening motor is rotating for above a predetermined amount of time without decreasing its rpm. This scenario may be the result of the claws failing to catch the loop of wire.

[0092] SpeedTightMotorCero is a variable holding values from a sensor which detects if the loop is being tightened by the motor at a speed of below 400 rpm. In such a case, the motor is instructed to stop. This might occur when motor is tightening a wire with too much force, or there is a mechanical failure jamming at least part of the total mechanism.

[0093] Stage 5 begins at the top of Figure 13A, and relates to reversing the direction of the motor 520, continuing through Figure 13B. This enables the fingers 620 to open, and reset the tying apparatus to begin tying new tie in due course. The process may be restarted at stage 1 , if no errors are detected. If the position of the shaft 505 is not sufficiently backward, then the movement continues until it is at a predetermined backward position. Optionally, a first trigger action forms only the loop around the rebar node 315, and a subsequent trigger activation twists the tie to fix the loop in place around the rebar node 315.

[0094] From a functional perspective, the flow charts of Figures 11A-13B demonstrate the following steps:

[0095] 1 . One or more springs positioned between the fixed carrier frame 515 and the carrier housing 510 are compressed. The carrier housing 510 is moved forward, compressing the springs between the carrier housing 510 and the fixed carrier frame 515. The motor 520 is static, and the fingers 620 adjacent the twisting head 125 are deactivated. This is the start and end state of the twisting head 125.

[0096] 2. A check is performed to ensure that the tying apparatus positioned correctly. For example, to check whether the guideway 105 and/or the hinged receiving guideway 310 is in contact with the rebars to be tied. The hinged receiving guideway 310 is in a fully forward position at this stage, so that that an approximate circle of wire of known diameter is formed, and to minimise the gap that the wire 110 must cross.

[0097] 3. The wire feeder 115 is started, and continues to run to unspool a pre-set wire length corresponding to the number of loops required. A check is performed to ensure that the spool 320 is continuing to turn, as a failure to rotate indicates that the spool 320 has run out of wire 110 and replacement wire is required if the tying operation is to continue. A further check is also performed to ensure the wire feeder 115 itself is rotating, and that the stepper motor optionally powering the wire feeder 115 has not stalled.

[0098] 4. If a correct length of wire 110 is unspooled and no error signals are detected, then the looping process is complete, and the loop is ready to be tied. The wire twist may therefore be formed.

[0099] 5. The wire twist is performed by using the fingers 620 linked to the twisting head 125 to grip the loop and rotate axially with the twisting head 125 as the carrier housing is released and springs back towards the fixed carrier frame 515 in order to tighten the tie.

[00100] Any range or device value given herein may be extended or altered without losing the effect sought, as will be apparent to the skilled person.

[00101] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages.

[00102] Any reference to 'an' item refers to one or more of those items. The term 'comprising' is used herein to mean including the method blocks or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

[00103] The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the spirit and scope of the subject matter described herein. Aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples without losing the effect sought. [00104] It will be understood that the above description of a preferred embodiment is given by way of example only and that various modifications may be made by those skilled in the art. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention.

Claims

1 . An apparatus for tying rebar, comprising: means for feeding one or more loops of wire around a rebar node; a fixed carrier frame; a twisting head housed in the fixed carrier frame; means for controlling translation of the twisting head along its longitudinal axis; means for controlling axial rotation of the twisting head; gripping means on one end of the twisting head configured to grip the loop(s) of wire; and a microcontroller configured to initiate the means for controlling translation and the means for controlling axial rotation of the twisting head, such that when the gripping means grip the loop(s) the twisting head translates into the fixed carrier frame away from the loop(s) and rotates axially in order to pull and twist the loop(s) thereby tying the rebar.

2. The apparatus of claim 1 comprising a trigger mechanism operable to control when one part of the apparatus is free to move axially relative to another part of the apparatus.

3. The apparatus of claim 1 wherein the means for feeding comprises: a guideway with a curved guide; a receiving guideway; a wire feeder operable to feed the one or more loops of wire around the rebar node following the curved guide.

4. The apparatus of claim 1 wherein the means for controlling translation of the twisting head and the means for controlling rotation of the twisting head comprise: a carrier housing sprung from the fixed carrier frame, such that the carrier housing is urged parallel to an axis of rotation of a twisting head; a ratchet mechanism; and a motor operable to rotate a spindle with a ball screw in a first direction and a second direction, wherein the spindle is constrained to move axially with respect to the twisting head, and the carrier housing is constrained to move axially with respect to the fixed carrier frame.

5. The apparatus of any preceding claim comprising a wire cutter and a wire cutter actuation means configured such that the axial movement of the twisting head causes the wire cutter to cut the wire.

6. The apparatus of claim 1 , wherein the gripping means comprises jaws and wherein the jaws are retractable

7. The apparatus of any preceding claim, wherein the or each rebar in the rebar node has a diameter of between 25-50mm.

8. The apparatus of any preceding claim, wherein the receiving guideway comprises a hinge operable to open to accept the rebar node, and then close such that the guideway and the receiving guideway at least partially enclose the rebar node.

9. The apparatus of any preceding claim, wherein the wire feeder is operable to feed a predetermined length of wire.

10. The apparatus of claim 5, wherein the predetermined length of wire corresponds to a predetermined number of loops around the node.

11 . The apparatus of any preceding claim, further comprising a wire spool operable to provide wire to the wire feeder.

12. The apparatus of claim 11 , wherein the wire spool is on different plane from the one or more loops of wire.

13. The apparatus of any preceding claim, wherein the wire cutter cuts the wire using a shearing action.

14. A method of tying rebar using a motorised apparatus, the method comprising: feeding one or more loops of wire around a rebar node; using gripping means on one end of a twisting head housed in a fixed carrier frame to grip the loop(s) of wire; and using a microcontroller, initiating means for controlling translation of a twisting head along its longitudinal axis and triggering means for controlling axial rotation of the twisting head, such that when the gripping means grip the loop(s) the twisting head translates into the fixed carrier frame away from the loop(s) and rotates axially in order to pull and twist the loop(s) thereby tying the rebar.

15. The method of claim 14 comprising attaching the motorized apparatus to a backpack and powering the motorized apparatus using the backpack.