BALE RUBBER HOLDING DEVICE AND METHOD FOR CUTTING BALE RUBBER

Provided is a bale rubber holding device 54 of an embodiment which is provided in a feeding device 50 which feeds a bale rubber 20, which is a lump of rubber, forward toward a cutting position, where the bale rubber holding device 54 grips a rear portion of the bale rubber 20.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese patent application 2020-170181 (filed on Oct. 7, 2020) and enjoys preferential benefits from this application. This application shall include all of the contents of Japanese Patent Application 2020-170181 by reference to Japanese Patent Application 2020-170181.

TECHNICAL FIELD

The present invention relates to a bale rubber holding device and a method for cutting a bale rubber.

BACKGROUND ART

A rubber mixture used as a material of a tire is prepared by mixing raw material rubber, a reinforcing material, a functional material, and the like in a predetermined ratio. As the raw material rubber used here, a bale rubber piece cut out from a bale rubber, which is a relatively large mass of rubber, is used.

A bale rubber is delivered to a factory in a form of being wrapped in a resin sheet which does not affect properties of the rubber mixture. The delivered bale rubber is cut by a cutter coming down from above and divided into a plurality of bale rubber pieces as described in PTL 1, and here, the bale rubber is cut together with the resin sheet while being wrapped in the resin sheet.

Normally, a bale rubber is intermittently fed toward a cutting position, and each time it is fed, it is cut by a cutter to cut out a bale rubber piece. In the related art, the bale rubber is fed to the cutting position by pushing a rear portion (a portion opposite to a feeding direction) of the bale rubber.

SUMMARY OF THE INVENTION

Problem that the Invention is to Solve

However, since a bale rubber is sticky to a cutter, in a method of the related art, a cut surface of a bale rubber and a rear potion of a bale rubber are lifted when cutting the bale rubber. As a result, a position of the bale rubber may shift. When a resin sheet covering the bale rubber is not cut even when the bale rubber is cut, the position of the bale rubber might shift due to being pulled by the resin sheet. Then, there is a problem that the bale rubber piece cannot be cut out with accurate dimensions at next cutting due to the misalignment of the bale rubber.

Therefore, an object of the invention is to provide a device and a method for facilitating cutting out a bale rubber piece with accurate dimensions.

Means for Solving the Problem

According to a bale rubber holding device of an embodiment, there is provided a bale rubber holding device which is provided in a feeding device which feeds a bale rubber, which is a lump of rubber, forward toward a cutting position, where the bale rubber holding device grips a rear portion of the bale rubber.

According to a method for cutting a bale rubber of an embodiment, there is provided a method for cutting a bale rubber which includes feeding the bale rubber forward toward a cutting position and cutting the bale rubber at the cutting position, where at least while the bale rubber is cut, a bale rubber holding device provided in a feeding device which feeds the bale rubber grips a rear portion of the bale rubber.

Advantage of the Invention

According to the embodiment, it becomes easy to cut out a bale rubber piece with accurate dimensions.

MODE FOR CARRYING OUT THE INVENTION

An embodiment will be described with reference to the drawings. The embodiment described below is merely an example and those which are appropriately modified without departing from a spirit of the present invention shall be included in a scope of the present invention.

1. Overall Configuration of Cutting Device

As illustrated inFIGS. 1 and 2, in a cutting device10, a preparation conveyor11, a first measurement conveyor12, and a constant-rate feed conveyor13are arranged in a row in this order. Next to the conveyors11,12, and13, a non-defective product box14, a non-defective product transport conveyor15, a second measurement conveyor16, and a defective product box17are arranged in a row in this order. The two rows are parallel. A cutting portion18and a discharge conveyor19are provided between the constant-rate feed conveyor13and the second measurement conveyor16. The cutting portion18is arranged on the constant-rate feed conveyor13side and the discharge conveyor19is arranged on the second measurement conveyor16side.

The preparation conveyor11is a belt conveyor. A bale rubber20is arranged on the preparation conveyor11. The bale rubber20is a mass of rubber as a raw material for a tire, is substantially rectangular parallelepiped shape, and is packaged with a resin sheet (not illustrated). The preparation conveyor11rotates in a direction of moving the bale rubber20on the preparation conveyor11toward the first measurement conveyor12. The preparation conveyor11is rotated by being driven by a motor35(seeFIG. 3).

The first measurement conveyor12is a roller conveyor composed of a plurality of rollers30. The roller30can rotate in a direction of moving the bale rubber20which has moved from the preparation conveyor11to the constant-rate feed conveyor13. The roller30is rotated by being driven by a motor36(seeFIG. 3). The plurality of rollers30are provided on a first weight sensor38(seeFIG. 3) and the weight of the bale rubber20placed on the rollers30can be measured by the first weight sensor38. The first weight sensor38may be located under the roller30while the bale rubber20is moving and may rise above the roller30when the bale rubber20is stopped to measure the weight of the bale rubber20.

The constant-rate feed conveyor13is a roller conveyor including a plurality of rollers31. The roller31is a rotatable free roller and can rotate in a direction orthogonal to the rotation direction of the roller30of the first measurement conveyor12.

A snap cover chain23which moves up and down with respect to the constant-rate feed conveyor13is provided. The snap cover chain23is an endless chain which rotates in the same direction as a transport direction of the first measurement conveyor12when driven by a motor24(seeFIG. 3). The snap cover chain23is provided at a gap between the roller31and the roller31of the constant-rate feed conveyor13. Then, the snap cover chain23rises above the roller31or descends below the roller31by a cylinder48(seeFIG. 3). The bale rubber20is transported from the first measurement conveyor12to a vicinity of a center of the constant-rate feed conveyor13by the snap cover chain23.

A feeding device50is provided on the constant-rate feed conveyor13. The feeding device50includes a cylinder51which operates with liquid or gas and a plate-shaped push plate52attached to a tip of a rod of the cylinder51. The push plate52is provided with a bale rubber holding device54(seeFIGS. 4 to 7) capable of gripping a rear end portion of the bale rubber20. When the rod of the cylinder51advances, the push plate52pushes and feeds the bale rubber20on the constant-rate feed conveyor13toward the cutting portion18. In the following description, a direction in which the feeding device50sends out the bale rubber20is referred to as “forward” and an opposite direction is referred to as “rear”. While the push plate52pushes the bale rubber20, the bale rubber holding device54grips a rear end portion of the bale rubber20. The bale rubber holding device54will be described below.

A servomotor may be used instead of the cylinder51as a device for moving the push plate52.

A length measuring sensor53is provided on the push plate52. When a first cutter40, which will be described below, of the cutting portion18is lowered, the length measuring sensor53can measure a distance from the push plate52to the first cutter40.

The cutting portion18is a portion which cuts the bale rubber20sent from the constant-rate feed conveyor13into a bale rubber piece22. As will be described below, the cutting portion18is provided with the first cutter40which descends toward the bale rubber20and a second cutter41which rises toward the bale rubber20.

The discharge conveyor19is a belt conveyor. The discharge conveyor19can rotate in the same direction as the rollers31of the constant-rate feed conveyor13. The discharge conveyor19is rotated by being driven by a motor33(seeFIG. 3). The discharge conveyor19is inclined to be high on a cutting portion18side and low on a second measurement conveyor16side. The bale rubber piece22formed by being cut by the cutting portion18is conveyed to the second measurement conveyor16by the discharge conveyor19.

The discharge conveyor19may be composed of a plurality of free rollers. Instead of the discharge conveyor19, a sliding plate inclined with respect to a horizontal plane may be used.

The second measurement conveyor16is a belt conveyor. The second measurement conveyor16can rotate in a direction parallel to the preparation conveyor11and the first measurement conveyor12. The second measurement conveyor16is rotated by being driven by a motor37(seeFIG. 3).

The defective product box17is arranged on one side of a rotation direction of the second measurement conveyor16and the non-defective product transport conveyor15and the non-defective product box14are arranged on the other side. The second measurement conveyor16is provided on a second weight sensor39(seeFIG. 3) and a weight wn(the weight of the bale rubber piece22cut out at the n-th time) of the bale rubber piece22placed on the second measurement conveyor16can be measured by the second weight sensor39. When the weight of the bale rubber piece22is within a reference value, the second measurement conveyor16rotates in a direction of the non-defective product box14, and when the weight of the bale rubber piece22exceeds the reference value, the second measurement conveyor16rotates in a direction of the defective product box17.

The non-defective product transport conveyor15is a belt conveyor. The non-defective product transport conveyor15transports the bale rubber piece22sent from the second measurement conveyor16to the non-defective product box14. The non-defective product transport conveyor15is rotated by being driven by a motor32(seeFIG. 3).

As illustrated inFIG. 3, the cutting device10is provided with a control unit25. The control unit25includes a storage unit26, a calculation unit27, and the like.

The first weight sensor38, the second weight sensor39, the length measuring sensor53, motors24,32,35,36, and37, cylinders42,46,47,48, and51, and the like are connected to the control unit25. An input device28for inputting manufacturing conditions and the like to the control unit25is also connected to the control unit25. The control unit25controls the motors24,32,35,36, and37, the cylinders42,46,47,48,51, and60, and the like based on measured values of the connected sensors and input values from the input device28.

2. Configuration of Bale Rubber Holding Device

As illustrated inFIGS. 4 to 7, the bale rubber holding device54includes plate-shaped movable portions55provided on both the left and right sides (In the description of the bale rubber holding device54, left and right are one side and the other side in a width direction of the push plate52) of the push plate52and claws56provided to project forward from a front surface of the movable portion55. A plurality of (three in the drawing) claws56are provided for one movable portion55and the claws56are arranged in a row in an up-down direction. Each claw56is curved toward the center in the width direction of the push plate52and has a sharp tip.

A horizontal plate-shaped extension portion57is provided to extend from the movable portion55toward a back side (the side opposite to the front side in a feeding direction) of the push plate52. The extension portion57is extended to a position beyond a center in the width direction of the push plate52on the back side of the push plate52. An elongated hole58is formed in a vicinity of the center of the push plate52in the width direction to penetrate the extension portion57in the up-down direction. The elongated hole58extends in an extension direction of the extension portion57.

The bale rubber holding device54further includes a cylinder60fixed by a fixing member59to the back surface of the push plate52and a rod member62provided at a tip of a rod61of the cylinder60. The rod member62is a single rod-shaped member extending in the up-down direction. The rod member62vertically penetrates the elongated holes58of the left and right extension portions57.

On the left and right sides of the back surface of the push plate52, shaft member holding portions63projecting rearward are provided. On both the left and right sides, the shaft member holding portions63respectively hold shaft members64extending in the up-down direction.

The shaft members64on both the left and right sides respectively penetrate holes66(seeFIG. 5) formed in the extension portions57on both the left and right sides in the up-down direction. The extension portion57and the movable portion55integrated with the extension portion57can be displaced by a predetermined angle in a rotation direction with the shaft member64as a rotation axis.

In such a bale rubber holding device54, when the cylinder60advances the rod61forward (lower side inFIGS. 6 and 7), while the rod member62slides in the elongated holes58of the extension portions57on both the left and right sides, portions of the elongated holes58of the extension portions57are pushed forward. The extension portion57is displaced in a rotation direction with the shaft member64as a rotation axis and the extension portion57and the movable portion55integrated with the extension portion57are parallel to the push plate52as illustrated inFIG. 6. The state here is referred to as a state in which the movable portion55is open.

When the cylinder60moves the rod61backward (upper side inFIGS. 6 and 7), while the rod member62slides in the elongated holes58of the extension portions57on both the left and right sides, the portions of the elongated holes58of the extension portions57are pulled backward. Then, the extension portion57is displaced in the rotation direction with the shaft member64as the rotation axis and the movable portion55integrated with the extension portion57comes out forward. Then, when the movable portion55moves forward, the claw56advances toward the center in the width direction of the push plate52as illustrated inFIG. 7. The state here is referred to as a state in which the movable portion55is closed.

When the bale rubber20contacts the front surface of the push plate52, if the claw56advances toward the center of the push plate52in the width direction, as illustrated inFIG. 7, the claw56bites into the bale rubber20and the claws56on both the left and right sides grip the bale rubber20.

On the back surface of the push plate52, a mounting portion65to which the rod of the above-described cylinder51is mounted is provided. The push plate52and the bale rubber holding device54are integrally sent out by the cylinder51.

3. Configuration of Cutting Portion

As illustrated inFIG. 8, the cutting portion18is provided with the first cutter40and the second cutter41adjacent to each other. The first cutter40and the second cutter41are arranged on a plane orthogonal to the feeding direction of the bale rubber20. The first cutter40is located on the constant-rate feed conveyor13side and the second cutter41is located on the discharge conveyor19side.

The first cutter40can be moved up and down by the cylinder42(seeFIGS. 1 and 3) and descends from an upper standby position toward the bale rubber20. The second cutter41can be moved up and down by the cylinder46(seeFIG. 3) and rises from a lower standby position toward the bale rubber20. A slight gap exists in a traveling direction of the bale rubber20between the first cutter40when descending and the second cutter41when ascending.

As a part of the cutting portion18, a first arrangement member43is provided between the constant-rate feed conveyor13and the first cutter40and a second arrangement member44is provided between the second cutter41and the discharge conveyor19. An upper surface of the first arrangement member43and an upper surface of the second arrangement member44are on the same surface as an upper surface of the constant-rate feed conveyor13. A portion from the upper surface of the first arrangement member43to the upper surface of the second arrangement member44is a cutting position arranged when the bale rubber20is cut.

The first arrangement member43is provided with a cutter receiving portion45to which a cutting edge of the first cutter40descending from above contacts. The cutter receiving portion45is formed as an inclined surface along the cutting edge of the first cutter40. The cutter receiving portion45can be displaced in a width direction of the first cutter40by the cylinder47(seeFIG. 3).

The first cutter40descends until it contacts the cutter receiving portion45. Therefore, the first cutter40cuts the bale rubber20from an upper end to a lower end. On the other hand, the second cutter41rises to a position slightly above the upper surface of the second arrangement member44. Then, the lowering of the first cutter40and the ascending of the second cutter41are performed in synchronization, but the second cutter41supports the bale rubber20from below while the first cutter40cuts the bale rubber20.

4. Manufacturing Method of Bale Rubber Piece by Cutting Device

First, manufacturing conditions are input from the input device28to the control unit25. The manufacturing conditions are the number of times one bale rubber20is cut, a target weight wtof the bale rubber piece22, and the like. The input may be performed manually by an operator, or may be performed by an imaging unit (not illustrated) reading a work instruction sheet or the like.

Next, the bale rubber20wrapped in a resin sheet (not illustrated) is placed on the preparation conveyor11. The control unit25, which detects that the bale rubber20is placed, drives the motor35to rotate the preparation conveyor11and drives the motor36to rotate the first: measurement conveyor12, in such a manner that the bale rubber20is transported to the center of the first measurement conveyor12.

When the control unit25detects that the bale rubber20reached the center of the first measurement conveyor12, the first weight sensor38measures a weight W of the bale rubber20. The measured weight W is stored in the storage unit in the control unit25.

The control unit25then controls the cylinder48to raise the snap cover chain23above the roller31of the constant-rate feed conveyor13. Next, the control unit25drives the motors36and24to rotate the first measurement conveyor12and the snap cover chain23. As a result, as illustrated inFIG. 8, the bale rubber20is transported to a predetermined position of the constant-rate feed conveyor13.

Next, the control unit25controls the cylinder51to move the push plate52of the feeding device50toward the bale rubber20at the predetermined position and stop the push plate52at a position where the push plate52comes into contact with the bale rubber20. Here, the movable portion55(not illustrated inFIGS. 8 to 11) of the bale rubber holding device54is open.

Next, the control unit25controls the cylinder60and closes the movable portion55. Then, as illustrated inFIG. 7, the claws56provided in the movable portion55grip the bale rubber20from two directions on the left and right. Here, the claw56bites into the rear end portion of the bale rubber20.

Next, the control unit25controls the cylinder42to lower the first cutter40until the first cutter40contacts the cutter receiving portion45(seeFIG. 9). Next, the control unit25controls the cylinder51to advance the push plate52and the bale rubber holding device54toward the first cutter40of the cutting portion18. During the advance operation, the bale rubber holding device54is still gripping the bale rubber20.

As illustrated inFIG. 9, the control unit25moves the push plate52to the position where the bale rubber20contacts the first cutter40. The bale rubber holding device54also moves together with the push plate52. When the bale rubber20contacts the first cutter40, the control unit25stops the movement of the bale rubber holding device54and the like. The stop of the bale rubber holding device54or the like may be performed when a sensor detects that the bale rubber20contacts the first cutter40, or may be performed when the bale rubber holding device54moves by a preset distance.

Next, the control unit25measures a distance L from the push plate52of the feeding device50to the first cutter40with the length measuring sensor53. The distance L measured here coincides with the length of the bale rubber20in the feeding direction to the cutting portion18. The measured distance (length of bale rubber20) L is stored in the storage unit26of the control unit25.

Next, as illustrated inFIG. 10, the control unit25raises the first cutter40. Then, as illustrated inFIG. 10, the bale rubber20is sent out by the feeding device50. During feeding, the bale rubber holding device54continues to grip the bale rubber20. The feeding puts the bale rubber20under the first cutter40. A feed distance Sn(Snmeans the n-th feed distance, and n=1 in the case of the first feeding as here) by the feeding device50here will be described below.

Next, as illustrated inFIG. 11, the control unit25lowers the first cutter40and at the same time raises the second cutter41. Here, the first cutter40descends until it contacts the cutter receiving portion45, but the second cutter41rises only slightly above the second arrangement member44. Therefore, the bale rubber20is cut by the descending first cutter40while being supported by the second cutter41from below. The second cutter41may make a notch in a lower part of the bale rubber20. Even during the cutting of the bale rubber20, the bale rubber holding device54continues to grip the bale rubber20.

At the same time that the lowered first cutter40contacts the cutter receiving portion45, or after the lowered first cutter40contacts the cutter receiving portion45, the control unit25controls the cylinder47to displace the cutter receiving portion45in the width direction (left-right direction) of the first cutter40. As a result, even when the lower end of the bale rubber20and the resin sheet wrapping the bale rubber20remain uncut, the remaining portion is torn off between the first cutter40and the cutter receiving portion45.

The second cutter41may be displaced in the width direction (left-right direction) of the second cutter41while rising or after being raised due to cutting of the bale rubber20.

The bale rubber piece22made by such cutting is transported to the second measurement conveyor16by the discharge conveyor19. When the control unit25detects that the bale rubber piece22has reached the second measurement conveyor16, the control unit25measures the weight wn(wnis the weight of the n-th bale rubber piece22, and in the case of the first one as here, n=1) of the bale rubber piece22with the second weight sensor39. The measured weight wnof the bale rubber piece22is stored in the storage unit26of the control unit25.

When the weight of the bale rubber piece22meets acceptance criteria, the control unit25controls the motor37to rotate the second measurement conveyor16and transports the bale rubber piece22to the non-defective product box14. On the other hand, when the weight of bale rubber piece22does not meet the acceptance criteria, the control unit25controls the motor37to rotate the second measurement conveyor16and transports the bale rubber piece22to the defective product box17.

The control unit25sends out the bale rubber20again by the feeding device50after the first cutting of the bale rubber20and performs the second cutting. The control unit25repeats feeding by the feeding device50and cutting by the first cutter40until the entire bale rubber20is divided into a plurality of bale rubber pieces22. The second and subsequent feed distance Snby the feeding device50will be described below.

The bale rubber holding device54continues to grip the rear end portion of the bale rubber20until the final cutting of the bale rubber20is completed. After the final cutting of the bale rubber20, the control unit25opens the movable portion55of the bale rubber holding device54to release the remaining bale rubber20(that is, the last bale rubber piece22) from the bale rubber holding device54. Then, the control unit25pushes the last bale rubber piece22to the discharge conveyor19with the push plate52.

5. Method for Determining Feed Amount of Bale Rubber

Here, a method for determining the feed distance Snof the bale rubber20by the feeding device50will be described based on a flowchart ofFIG. 12.

First, as described above, the first weight sensor38measures the weight W of the bale rubber20before cutting on the first measurement conveyor12(ST1). The measured weight W is stored in the storage unit26of the control unit25.

Next, as described above, the length measuring sensor53measures the length L of the bale rubber20before cutting pressed against the first cutter40by the feeding device50(ST2). The measured length L is stored in the storage unit26of the control unit25.

The calculation unit27of the control unit25calculates a first feed amount (feed distance) S1of the bale rubber20by the feeding device50after measuring the length L of the bale rubber20(ST3). The feed distance S1is calculated by the following equation so that when the length of the bale rubber piece22becomes S1, the weight of the bale rubber piece22becomes a target weight wt. The target weight wtof the bale rubber piece22is stored in the storage unit26in advance by an operator.

Next, the control unit25controls the feeding device50and sends the bale rubber20forward (in a direction of the first cutter40) by the obtained distance S1(ST4). Next, the control unit25controls the first cutter40and the second cutter41to cut the bale rubber20and cut out the bale rubber piece22having a length S1(ST5).

Next, as described above, the second weight sensor39provided on the second measurement conveyor16measures a weight w1of the cut-out bale rubber piece22(ST6). The measured weight w1is stored in the storage unit26of the control unit25.

Next, the control unit25determines whether the entire bale rubber20is divided into the bale rubber pieces22(ST7).

For example, a sensor detects the amount of the bale rubber20remaining further on the feeding device50side than the first cutter40. When the detected amount is equal to or more than a predetermined amount, it is determined that the division is not completed, and when the detected amount is less than the predetermined amount, it is determined that the division is completed.

Alternatively, the number of cuts required to divide the entire bale rubber20into the bale rubber piece22is set in advance in the control unit25. The control unit25determines that the division of the bale rubber20is not completed when the cutting of the set number of cuts is not completed. When the cutting of the set number of cuts is completed, it is determined that the division of the bale rubber20is completed.

Anyway, when the control unit25determines that the division of the bale rubber20is not completed (No in ST7), the control unit25proceeds to a next step (ST8, ST9). On the other hand, when the control unit25determines that the division of the bale rubber20is completed (Yes in ST7), the control unit25ends the above flow.

In the present embodiment, it is assumed that the bale rubber20is cut 10 to 15 times. Therefore, when the above-described first cutting is completed, the control unit25determines that the division of the bale rubber20is not completed (No in ST7). Therefore, the flow proceeds to the next step (ST8, ST9).

In the next step (ST8, ST9), the calculation unit27calculates a distance S2of second feeding of the bale rubber20so that a weight w2of the bale rubber piece22cut out the second time can be brought closer to the target weight wt. Specifically, the calculation unit27calculates the distance S2of the second feeding by the following equation using the weight w1of the bale rubber piece22cut out immediately before.

That is, although a cross-sectional area (area in a plane orthogonal to the feeding direction) of the bale rubber20changes depending on the location, it is assumed that the cross-sectional area is approximately the same at the location of the bale rubber piece22cut out the first time and the location of the bale rubber piece22cut out the second time. Based on the assumption, it can be said that the weight per unit length of the bale rubber piece22cut out the second time matches the weight w1/S1per unit length of the bale rubber piece22cut out the first time. Therefore, the target weight wtof the bale rubber piece22is divided by the weight w1/S1per unit length of the bale rubber piece22to determine the distance S2for the second feeding.

When the distance S2for the second feeding is determined, the process returns to a step (ST4) of feeding the bale rubber20and the feeding device50feeds the bale rubber20by the distance S2. The first cutter40cuts out the second bale rubber piece22and the weight w2of the bale rubber piece22is measured by the second weight sensor39.

After that, the control unit25repeats the routine after ST4until it is determined that the division of the bale rubber20is completed (Yes in ST7). In the routine, the (n+1)-th feed distance Sn+1of the bale rubber20is calculated by the following generalized equation using the n-th feed distance Snand the weight wnof the bale rubber piece22cut out at the n-th time.

6. Effect of Embodiment

As described above, the bale rubber holding device54of the present embodiment can grip the rear portion of the bale rubber20. Therefore, it is possible to prevent the bale rubber20from being displaced when the bale rubber20is cut, and thus it becomes easy to cut out the bale rubber piece22with accurate dimensions.

Here, since the bale rubber holding device54grips the rear portion of the bale rubber20by interposing it from two directions, the bale rubber20can be firmly gripped. Since the bale rubber holding device54includes the claw56which bites into the bale rubber20, the bale rubber20can be firmly gripped.

In the embodiment, the bale rubber holding device54continues to grip the rear portion of the bale rubber20while the bale rubber20is cut by the first cutter40(that is, during one cutting operation by the first cutter40). Therefore, it is possible to prevent the bale rubber20from being displaced during cutting.

In the embodiment, the bale rubber holding device54continues to grip the rear portion of the bale rubber20while the bale rubber20is cut by the first cutter40a plurality of times. Therefore, it is possible to prevent the bale rubber20from being displaced between the first cutting and the second cutting.

7. Modification Example

Various modifications can be made to the embodiment described above.

For example, as a bale rubber holding device, various devices capable of gripping the rear portion of the bale rubber20can be applied.

A bale rubber holding device154shown inFIG. 13is an example of a device including a claw which bites into the bale rubber20and gripping the rear portion of the bale rubber20by interposing it from two directions.

The bale rubber holding device154is provided for a push plate152corresponding to the push plate52in the embodiment described above. A rib166extending in the up-down direction is fixed to one (left side in the case ofFIG. 13) of the left and right sides of the front surface of the push plate152. The rib166is provided with three small claws167arranged in the up-down direction. The small claws167extend toward the center of the push plate152in the left-right direction and have a sharp tip.

On the other side (on the right side in the case ofFIG. 13) of the push plate152in the left-right direction, a notch168having a shape notched at a central portion in the up-down direction is formed. A movable portion155is provided at a location of the notch168. A cylinder160is provided on the rear surface of the push plate152and the movable portion155can be moved in the left-right direction by the cylinder160.

Three large claws156arranged in the up-down direction are provided on a front surface of the movable portion155. The large claws156project forward from the notch168of the push plate152. The large claws156are curved toward the center in the left-right direction (width direction) of the push plate152and the tips thereof are sharpened.

In such a bale rubber holding device154, when the cylinder160moves the movable portion155away from the small claw167, a distance from a tip of the large claw156provided in the movable portion155to a tip of the small claw167is wider than a width of the bale rubber20.

Here, the bale rubber20is arranged between the tip of the large claw156and the tip of the small claw167. Next, the cylinder160moves the movable portion155closer to the small claw167. As a result, the distance from the tip of the large claw156to the tip of the small claw167becomes narrower than the width of the bale rubber20and the large claw156and the small claw167bite into the bale rubber20. The large claw156and the small claw167can grip the rear portion of the bale rubber20from two directions.