A reverse rotational number of a binding wire feed mechanism is set such that a binding wire is completely pulled back regardless of a boldness or flexibility of the binding wire, a diameter of a reinforcing bar or the like. A driven gear 14 having a V groove of the binding wire feed mechanism is brought into elastic contact with a main drive gear 13 having a V groove by a spring and the binding wire is fed by pinching the binding wire by the main drive gear 13 having the V groove and the driven gear 14 having the V groove. After feeding out the binding wire to form a loop around the reinforcing bar and clamping a front end of the binding wire by a twist mechanism, the binding wire feed mechanism is rotated reversely and the binding wire is pulled back to be wound around the reinforcing bar. After stopping the binding wire, the main drive gear 13 having the V groove and the driven gear 14 having the V groove are slipped relative to the binding wire to rotate idly and continue to rotate reversely until a predetermined rotational number.

TECHNICAL FIELD

The present invention relates to a reinforcing bar binding machine, particularly relates to a reinforcing bar binding machine constituted to adjust a length of a binding wire by pulling back the binding wire after winding the binding wire around a reinforcing bar.

BACKGROUND ART

There is known a reinforcing bar binding machine having a binding wire feed-mechanism for feeding out a binding wire and hanging the binding wire around a reinforcing bar and a binding wire twist mechanism for twisting the binding wire wound around the reinforcing bar to bind for carrying out binding operation of 1 cycle by successively executing binding ire binding operation and binding wire twisting operation by trigger operation. Further, as disclosed in, for example, JP-A-08-034406 (claim 2, paragraph No. 0022, paragraph No. 0055), there is proposed a reinforcing bar binding machine for pulling back a binding wire after binding wire feed operation, bringing a loop of the binding wire into close contact with a reinforcing bar to start twisting operation. According to the reinforcing bar binding machine, by pulling back the binding wire, a line length thereof is adjusted in accordance with a diameter of the reinforcing bar to thereby promote finishing and also save to reduce an amount of consuming the binding wire.

In the case of constituting the reinforcing bar binding machine such that the binding wire is pulled back after the binding wire feeding operation and the twisting operation is started in a state of bringing the binding wire into close contact with the reinforcing bar, setting of a pull back tension poses a problem. When a feeding force of the binding line feed mechanism is weak, time is taken in pulling back the binding wire or the binding wire cannot be pulled back. Further, when the feeding force is conversely excessively large, there is a concern of cutting the binding line.

As a means for preventing such a drawback from being brought about, it is conceivable to provide electric control means for setting a motor torque to a degree of being sufficient for pulling back the binding wire and stopping a motor by detecting an increase in a drive current by a rapid increase in a pull back resistance in finishing to pull back the binding wire. However, a flexibility of the binding wire significantly differs by a kind of the binding wire or an environmental condition of an outside air temperature or the like and a width of varying the pull back resistance is wide and therefore, a width of changing the current is not constant, a peak value of the current in stopping the binding wire is significantly varied also by a remaining capacity of a power source battery and therefore, it is difficult to control to stop the motor stably without being influenced by these factors. Further, when there is constructed a constitution of setting a threshold value of the current of stopping the motor at each time for pertinently pulling back the binding wire, the operation becomes complicated and practical performance is deteriorated. Further, there also poses a problem that cost is increased by providing a control circuit including a current detecting circuit or the like.

DISCLOSURE OF THE INVENTION

Hence, there poses a technical problem to be resolved in order to stably pull back a binding wire regardless of a kind of the binding wire, and an external condition, a voltage of a battery or the like and it is an object of the invention to resolve the above-described problem.

The invention is proposed to achieve the above-described object. There is provided a reinforcing bar binding machine comprising a binding wire feed mechanism for feeding out a binding wire to wind around a reinforcing bar, a binding wire grasp mechanism of grasping and twisting the winding wire wound around the reinforcing bar, a binding wire pull back function of pulling back a loop of the binding wire wound around the reinforcing bar to be brought into close contact with the reinforcing bar and thereafter twisting the binding wire, control means for reversely rotating a drive system of the binding wire feed mechanism by a constant number in pulling back the binding wire, and means for permitting to slip the drive system for restricting a pull back tension exerted to the binding wire to be equal to or smaller than a limit value of cutting the binding wire.

Further, there is provided the reinforcing bar binding machine constituting the binding wire feed mechanism by bringing a driven sheave into elastic contact with a main drive sheave and constituted such that when a pull back tension exerted to the binding wire pinched between the pair of sheaves exceeds a certain value, the sheaves are idly rotated to restrict the pull back tension exerted to the binding wire.

Further, there is provided the reinforcing bar binding machine constituting the binding wire feed mechanism by bringing the driven sheave into elastic contact with the main drive sheave, interposing a torque limiter of a friction clutch or a ball clutch to a drive system of the binding wire feed mechanism and constituted such that when a pull back tension exerted to the binding wire pinched between the pair of sheaves exceeds a certain value, the main drive sheave and the driven sheave are stopped to restrict the pull back tension exerted to the binding wire.

Further, in notations in the drawings, numeral1designates a reinforcing bar binding machine, numeral3designates a binding wire clamp mechanism, numeral4designates a binding wire feed mechanism, numeral6designates a magazine, numeral7designates a nose, numeral8designates a center clamp plate, numeral9designates a right clamp plate, numeral10designates a left clamp plate, numeral11designates a cutter devise, numeral13designates a main drive gear having a V groove, numeral14designates a driven gear having a V groove, numeral15designates s feed motor, numeral16designates a reduction gear mechanism, numeral17designates a lever, numeral18designates a compression coil spring, numeral19designates a binding wire guide, numeral23designates a gear for feeding, numeral24designates a torque limiter, notation W designates a binding wire, notation S designates s reinforcing bar.

BEST MODE FOR CARRYING OUT THE INVENTION

Although an embodiment of the invention will be described in details in reference to the drawings as follows, for convenience of explanation, first, an outline of a total constitution of a reinforcing bar binding machine will be explained.FIG. 1shows a reinforcing bar binding machine1. A binding wire clamp mechanism3and A binding wire feed mechanism4are included in a casing2. A binding wire reel (not illustrated) is charged into the magazine6arranged on a front side of a grip5. A binding wire W wound on the binding wire reel is fed out to an upper side by the binding wire feed mechanism4, forms a loop along a guide groove7aat an inner periphery of a nose7and is fed into the binding wire clamp mechanism3. The binding wire clamp mechanism3is constituted by a center clamp plate8and a movable clamp plates9,10on left and right sides thereof. A front end of the binding wire W is brought to between the right clamp plate9(depth side of paper face ofFIG. 1) and the center clamp plate8to be clamped. Successively, the binding wire feed mechanism4is driven to reversely rotate to pull back the binding wire W to bring about a state of winding the binding wire W around the reinforcing bar and the left clamp plate10is closed. A rear end of the binding wire loop is clamped by the left clamp plate10and the center clamp plate8. Further, the cutter devise11cuts the rear end of the binding wire loop. The binding wire clamp mechanism3is rotated in a state of clamping both ends of the binding wire loop. By twisting together the both ends of the binding wire loop, the reinforcing bar is wound.

FIG. 2throughFIG. 4shows the binding wire feed mechanism4. A main drive gear13having a V groove and a driven gear14having a V groove are arranged on a base plate12. The two pieces of the gears13,14having the V grooves are brought in mesh with each other. A gear of the reduction gear mechanism16connected to the feed motor15is brought in mesh with the main drive gear13having the V groove. As shown byFIG. 3, the driven gear14having the V groove which is not directly brought in mesh with the feed motor15is attached to the lever17and is brought into elastic contact with the main drive gear13having the V groove by a spring force of the compression coil spring18attached to the lever17, and a contact pressure between the main drive gear13having the V groove and the driven gear14having the V groove is determined by the spring force of the compression coil spring18.

When a lower end portion of the lever17is pressed to a center side (left side ofFIG. 3), the driven gear14having the V groove attached to an upper portion thereof is moved laterally to leave from the main drive gear13having the V groove on the motor side, and the binding wire can be passed between the main drive gear13having the V groove and the driven gear14having the V groove. The binding wire guide19having a funnel shape is provided on a lower side of a middle of the two pieces of the gears13,14having the V grooves, and the binding wire is set to between the main drive gear13having the V groove and the driven gear134having the V groove by passing the binding wire through the binding wire guide19from the lower side.

As described above, in 1 cycle operation of the reinforcing bar binding machine1, respective steps of feeding the biding wire, clamping the front end of the binding wire loop, pulling back the binding wire, clamping the rear end of the binding wire loop, cutting the binding wire and twisting the binding wire are successively executed by a control of a control portion of a microprocessor or the like. The aspect of the invention resides numbers of reversely rotating the feed motor15and the main drive gear13having the V groove of the binding wire feed mechanism4, in the step of pulling back the binding wire, are set to values sufficient for completely pulling back the binding wire, in any conditions. Further, a principal point thereof resides in that the control pressure of the main drive gear13having the V groove and the driven gear14having the V groove is set in consideration of a strength of the binding wire. When two pieces of the gears13,14having the V grooves are rotated in a state of forcibly stopping the binding wire, the binding wire is prevented from being cut by slipping the gears13,14having the V grooves and the biding wire.

FIG. 5shows an initial state of the reinforcing bar binding machine1, and a front end of the binding wire W is disposed at a position the same as that of a front end of the cutter devise11. When a guide plate21hung between the nose7and a lower side guide arm20of the reinforcing bar binding machine is pressed to the reinforcing bar S and a trigger lever22shown inFIG. 1is pulled, the binding wire feed mechanism4is started to feed out the binding wire W to the upper side. As shown byFIG. 6, the binding wire W is formed in a loop shape along the nose7, the front end is brought to between the center clamp plate8and the guide clamp plate9(depth side of paper face) of the binding wire clamp mechanism3and impinges on a stopper portion9aprovided at an upper end of the right clamp plate9to stop. The right clamp plate9is closed by a cam mechanism and the front end of the binding wire is clamped by the center clamp plate8and the right clamp plate9.

Successively, the binding wire W is pulled back by reversely driving to rotate the main drive gear13having the V groove and the driven gear14having the V groove of the binding wire feed mechanism4, the feed motor15is driven to rotate reversely up to a previously set rotational number by the control portion and the binding wire W is wound around the reinforcing bar S as shown byFIG. 7. Further, after sufficiently pulling back the binging wire W to stop, the gears13,14having the V grooves are reversely rotated until reaching a predetermined rotational number, and the main drive gear13having the V groove and the driven gear14having the V groove are reversely rotated in an idly rotated state by slipping while pinching the binding wire W until the feed motor15is stopped. That is, even when there is a difference in a diameter of the reinforcing bar, a difference of an amount of pulling back the binding wire W can be absorbed by idly rotating the gears13,14having the V grooves. In this way, by setting the reverse rotational number of the gears13,14having the V grooves constant, the binding wire W can be brought into close contact with the reinforcing bar S regardless of a boldness or a number of pieces of the reinforcing bars, a kind of the binding wire, and an external condition of an outside air temperature or the like, or a voltage of a battery.

Successively, after cutting the binding wire W by driving to rotate an outer side ring portion of the cutter devise11, the left clamp plate10is closed by the cam mechanism and the rear end of the binding wire is clamped by the center clamp plate8and the left clamp plate10, a total of the biding wire clamp mechanism3is driven to rotate and the reinforcing bar S is bound by twisting an end portion of the loop of the binding wire W as shown byFIG. 8. Further, after finishing to bind the wire, the clamped end portion of the binding wire W is released to return to the initial state ofFIG. 5. Further, with regard to the control of the reverse rotational number of the main drive gear13having the V groove, various detecting means of a pulse detecting circuit of detecting the rotational number of the feed motor15, a rotational number sensor of directly detecting the rotational number of the main drive gear13having the V groove and the like are naturally applicable.

Further, in place of the constitution of setting the contact pressure of the main drive gear13having the V groove and the driven gear14having the V groove to permit to slip the binding wire W, as shown byFIG. 9, there may be constructed a constitution in which a torque limiter24of a friction clutch or a ball clutch or the like is interposed between an output shaft of the reduction gear mechanism16and the gear13for feeding, after completely pulling back the binding wire W, the main drive gear13having the V groove and the driven gear14having the V groove are stopped by friction relative to the binding wire W, and only the feed motor15and the reduction gear mechanism16are rotated up to the predetermined reverse rotational number.

Further, the invention is not limited to the above-described embodiment but can variously modified further in the technical range of the invention and the invention can naturally cover the modifications.

INDUSTRIAL APPLICABILITY

As has been explained above, according to the reinforcing bar binding machine of the invention, the binding wire feed mechanism is driven to rotate reversely by the constant rotational number in the step of pulling back the binding wire, when pulling back is finished before finishing the pulling back step, the drive system is reversely rotated by slipping relative to the binding wire and therefore, the binding wire can completely be pulled back regardless of the boldness or the number of pieces of the reinforcing bars, the kind of the binding wire, the external condition, the voltage of the battery or the like and there is not a concern of cutting the binding wire, which archives an effect in stabilizing a binding function.