JP2521219B2 - Full web type automatic stretch wrapping machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full-web type automatic stretch wrapping machine, and more specifically, a rotary table is used to rotate an article to be wrapped, and a stretch film is tensioned around it to wind only one layer. The present invention relates to a full-web type automatic stretch wrapping machine that can fix an object to be wrapped.

[0002]

2. Description of the Related Art Conventionally, an automatic stretching process for automatically carrying out all steps of winding a stretch film around a rotary table provided with a conveyer for loading and unloading the package, while tensioning a stretch film around the rotary table. The packaging machines are roughly classified into a spiral type as disclosed in Japanese Utility Model Laid-Open No. 57-95302 and a full web type as disclosed in Japanese Patent Laid-Open No. 53-11690. What these automatic stretch wrapping machines have in common is that the gripper attached to the rotary table (or rotating in synchronization with the rotary table) grips the end of the stretch film for at least one first rotation, and then the second rotation. It is to release the sandwiched film at an appropriate timing, that is, after the second film has pressed on the first film. Therefore, since the first roll of film is not tense at all, it does not serve the function of tightening the object to be wrapped, and the film is wasted accordingly.

Also, for example, US Pat. No. 4,413,46
The so-called "pass-through type" automatic stretch wrapping machine as disclosed in Japanese Patent No. 3 is to wrap a stretch film wider than the height of the object to be wrapped and to wrap it around the object to be wrapped only once. Can be tightened and fixed.

However, since this pass-through type automatic stretch wrapping machine also wraps the article to be wrapped while moving it, it is not possible to provide a holding apparatus for the article to be wrapped as in the type using a rotary table, and a stretch film is used. Although there is a difference depending on the method of applying tension, due to the resistance of the stretch film tensioned in the process of passing the packaged object through the machine, that is, in the stretch packaging process, it is very light, such as an empty PET bottle, and has a high load. There was a problem that expensive items would be misaligned on the pallet. In addition, if a pass-through type device is adopted instead of the rotary table type device that has been widely used in the past, the layout of the entire automatic packing line must be changed due to the difference in the size of the device. Needed capital investment.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and its problem is that a rotary table having a conveyor for loading and unloading articles to be packaged is used to wrap the articles to be packaged by a holding device. The stretch film wider than the height of the object to be wrapped can be tensioned while the object is stabilized and the object to be wrapped is rotated once, and the object to be wrapped can be wrapped around the object to be tightened and fixed. And to provide a full-web type automatic stretch wrapping machine capable of matching main dimensions in layout with a conventional rotary table type automatic stretch wrapping machine for objects to be packaged of the same size.

[0006]

In order to solve the above problems, a full web type automatic stretch wrapping machine of the present invention is
It consists of a rotary table equipped with a conveyor for loading and unloading the article to be packaged, and a gantry provided independently on the table on the base frame, and the gantry is made of a stretch film wider than the height of the article to be packaged. In a full-web type automatic stretch wrapping machine provided with a film unwinding device for unwinding and winding the film and a tension applying device for tensioning the film, the rotary table is stopped every one time and the rotary table is placed on the rotary table. Holds the tip of the stretch film in the vicinity of its periphery over the entire width (of the film), and mounts a pillar-type gripper that rotates 360 ° (at the time of start-up). Further, on the frame, between the fingers of the pillar-type gripper. A push-in blade that pushes in the tip of the stretch film and the winding start end and winding end of the film wrapped around the package are heat-bonded. A heat sealer and a knife mechanism that cuts the stretch film between the heat sealer and the fingers are provided, and a swing arm that swings toward the pillar-shaped gripper is provided immediately after the rotation table is stopped. It is a thing.

[0007]

In the apparatus of the present invention, if necessary, the object to be packaged is stabilized by the object to be packed on the rotary table, and the pillar-shaped gripper attached near the periphery of the rotary table fixes the tip of the stretch film. 3 while holding
After rotating 60 °, the tensioned stretch film is wound around the article to be wrapped by one rotation together with the turntable.

After the rotary table is stopped, the swing arm swings toward the pillar-shaped gripper, and engages with the swing-type gripper to slide the stretch film at the winding start end and the winding end with the guide roller. Release the winding start end of the stretch film held by the fingers of the pillar-shaped gripper while being held by the stop member, cut the end of the winding by the knife mechanism, and then use the heat sealer to stretch the film. While heat-sealing and connecting the winding start end and the end of the previously cut end of the winding end that is close to the object to be wrapped, the other end of the stretch film that has not been heat-sealed is heat-sealed. When the fingers are clamped as the winding start end in the next step, the swing arm returns to the original point and the entire packaging step is completed. In this way, the packaging machine of the present invention has the function of tensioning the stretch film around the article to be wrapped and winding only one layer, and tightening and fixing the article to be packaged.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the device of the present invention will be described in detail below with reference to the drawings, but the present invention is not limited to this. FIG. 1 is a schematic plan view showing an overall image of an embodiment of the device of the present invention, in which a supporting arm of a device for pressing an object to be packaged is omitted for easy understanding of the drawing. Figure 2
1 is a schematic side view of the device of FIG. 1, FIG. 3 is a schematic plan sectional view for explaining the structure of a pillar-type gripper, and FIG. 4 is a mechanism for supplying a power source to an operating device on a rotary table. In the schematic cross-sectional side view of the rotary table, some devices such as a motor and a speed reducer for rotating the table are omitted for easy viewing.

FIG. 5 is a schematic plan sectional view for explaining the structure of the swing arm, and FIG. 6 is a schematic perspective view for explaining the structure of the column-type gripper and the swing arm. The parts are cut away or omitted in the drawing. 7 and 8
9 and 9 are schematic plan views for explaining the continuous operation of the apparatus of FIG. 1, wherein A to C in FIG. 7, DF in FIG. 8 and G in FIG. Indicates. 10 to 1
6 is a schematic plan sectional view for explaining the operation of the columnar gripper and the swing arm following G in FIGS. 7 to 9, and each shows each stage of the operation. 17 is a schematic plan view of the device of FIG. 1, showing the operating state following FIG.

In the figure, reference numeral 1 is a base frame, 2 is a rotary table, 3 is a chain conveyor, 4 is a gantry, 5 is a film unwinding device, 6 is a drive roller stretching mechanism which is a tension applying device, and 7 is a cover. Package holding device, 8 is a taper cone for locking, 9 is an object to be wrapped, 10 is a column-type gripper, 11 is a receiving hole for the taper cone, 12 and 13 are fingers, 1
Reference numerals 4 and 15 are air cylinders for operating the fingers 12 and 13, respectively, 16 is an air tube, 17 and 18 are anti-slip members, 19 is a chuck holder, 20 is a swing arm, and 2 is a swing arm.
Reference numerals 1 and 22 are film guide rollers, 23 is a brake shoe, and 24 and 25 are springs.

Reference numeral 26 is an impulse heat sealer, 27 is a hot wire cutter, 28 is a pressing blade, 29 is a chuck, 30 is an air cylinder for moving up and down the device for pressing the object to be packaged, 31 is an air cylinder for rocking the rocking arm, 3
2 is an air cylinder for operating the chuck, 33 is an air cylinder for moving the heat wire cutter back and forth, 34 is an air cylinder for moving the pushing blade back and forth, 35 is an air cylinder for moving the taper cone up and down, and 36 is the pillar gripper 10 at 360 °. A geared motor with a brake for rotating, 37 is a geared motor with a brake for driving the chain conveyor 3, 38 and 39 are slip rings, 4
0 and 41 are rotary joints.

The apparatus of this embodiment shown in FIGS. 1 and 2 is equipped with a conveyor 3 for loading and unloading an article 9 to be packaged, and a rotary table 2 which stops at each rotation, and a rotary table on the base frame 1 which is independent of the rotary table. And a stanchion 4 provided on the stanchion, and a film unwinding device 5 for unwinding the winding of a stretch film having a width wider than the height of the article 9 to be wound, and a tension applying device for tensioning the film. It is composed of two rollers that are forcibly driven as follows. The downstream roller is rotated at a higher peripheral speed than the upstream roller, and it is lifted and lowered by the operation of the drive roller stretching mechanism 6 and the air cylinder 30 that stretches the film between these rollers. An object-to-be-packaged pressing device 7 is attached to stabilize the package 9 by pressing it from above. Further, a pillar-type gripper 10 is attached near the peripheral edge on the rotary table 2,
A swing arm 20 that swings toward the pillar-shaped gripper 10 and engages with the pillar-shaped gripper 10 is provided on the base frame 1.

Next, a pillar-type gripper 1 which is an essential part of the present invention
0 and the swing arm 20 will be described in detail. As shown in FIGS. 3 and 6, the pillar-shaped gripper 10 has a pair of fingers 1 for holding the tip of the stretch film F.
2, 13 and the air cylinders 14 and 15 for operating each of these fingers are combined as shown in FIG.
Multiple sets are installed at regular intervals in the downward direction.
Further, one air tube 16 extending over substantially the entire length is attached to the pillar-type gripper 10. This is a backup member when heat-sealing the winding start end and the winding end of the stretch film F. Fulfill the role of.

A receiving hole 11 for a taper cone for locking is provided on the top surface of the pillar-type gripper 10, and when the pillar-type gripper 10 and the swing arm 20 are engaged with each other, the support arm of the device 7 for pressing the object to be packaged. Attached to the lock taper cone 8 that moves up and down by the operation of the air cylinder 35.
(See FIG. 2) descends and is inserted into the receiving hole to fix the column-type gripper 10. Further, when the pillar-type gripper 10 is engaged, anti-slip members 17 and 18 are attached to the portions where the film guide rollers 21 and 22 attached to the swing arm come into contact, respectively. A chuck receiver 19 is attached to a portion of the arm 20 with which the chuck 29 is engaged.

As shown in FIG. 4, a pillar-type gripper 1
At the lower end of 0, a slip ring 39, a rotary joint 41, and a gear motor 36 with a brake for rotating the pillar gripper 10 360 ° are attached. The actuators mounted on the rotary table 2, including the pillar gripper 10, include slip rings 38 mounted on the rotary shaft of the rotary table 2 as well as other types of automatic stretch wrapping machines. Electric power and compressed air are supplied through the rotary joint 40. Electric power is supplied from the slip ring 38 to the brake geared motor 37 that drives the chain conveyor 3 and the brake geared motor 38 that rotates the pillar gripper 10. Further, the electric power for controlling the solenoid valves of the air cylinders 14 and 15 and the air tube 16 for operating the fingers 12 and 13 on the pillar gripper 10 from the slip ring 38 through a slip ring 39 attached to the lower end of the pillar gripper 10. Is supplied. Compressed air is supplied from the rotary joint 40 to the air cylinders 12 and 13 and the air tube 16 through the rotary joint 41 attached to the lower end of the pillar gripper 10.

Next, referring to FIGS. 5 and 6, the swing arm 2
The structure of 0 will be described. At the lower end of the swing arm 20, an air cylinder 31 for swinging the arm toward the pillar gripper 10, a chuck 29 for engaging the arm with the pillar gripper 10, and a chuck 29 for operating the chuck 29. An air cylinder 32 is attached. Film guide rollers 21 and 22 are attached to both left and right ends (in FIG. 5) of the swing arm 20, and when the arm is engaged with the pillar-type gripper 10, the roller 2 is attached.
The springs 24 and 25 respectively press-contact the anti-slip members 17 and 18 of the pillar-type gripper 10 with the springs 1 and 22 to sandwich the stretch film F therebetween.

The film guide roller 2 upstream of the feed path of the stretch film F (that is, the right hand in FIG. 5).
2 has a built-in ratchet (not shown),
While the stretch film F is sandwiched between the anti-slip member 18, the stretch film F is allowed to move from the upstream side to the downstream side, but is not moved in the opposite direction. In addition, the film guide roller 21 on the downstream side
Has a built-in brake shoe 23. When the swing arm 20 engages with the pillar-type gripper 10 and the film guide roller 21 presses the anti-skid member 17, the spring 2
The brake shoe 23 is pressed against the film guide roller 21 by the force of 4, and the anti-slip member 17 of the pillar-type gripper 10 is kept without rotating the film guide roller 21.
The stretch film F is sandwiched between and. Between the film guide rollers 21 and 22, the impulse heat sealer 26 from the left hand of FIG. 5, the hot wire cutter 27 operated by the air cylinder 33 on the right side thereof, and the indentation operated by the air cylinder 34 on the right side thereof. Blade 28
Is installed.

It should be noted that the swing arm 20 is a pillar-type gripper 1.
When engaged with 0, the impulse heat sealer 26
Is located at a position facing the air tube 16 of the pillar-type gripper 10. In addition, as shown in FIG.
Are placed at regular intervals in the vertical direction of the swing arm 20,
Plural sheets are attached to the pillar-shaped gripper 10 one by one at positions which are alternate with the fingers 12 and 13 and exactly different from each other.

Next, FIG. 1, FIG. 2, FIG. 7 to FIG. 9 and FIG.
The operation of the apparatus of this embodiment will be described with reference to FIG. As shown in FIGS. 1 and 2, in the apparatus of the present embodiment, the chain conveyor 3 on the rotary table 2 is started in response to the carry-out signal from the upstream equipment, and the article 9 to be packaged is received from the upstream equipment. When conveyed to the center of the rotary table 2, the chain conveyor 3 is automatically stopped by an appropriate detection device such as a beam switch (not shown). Then, the object holding device 7 is lowered by the operation of the air cylinder 30, and presses the top surface of the object 9.

At the time of starting the apparatus, the pillar gripper 10 and the swing arm 20 are in the state A of FIG. That is, the pillar-type gripper 10 is located at the position closest to the gantry 4 by sandwiching the tip of the stretch film F over the entire width of the film, and the swing arm 20 is still in the pillar-type gripper 10.
Not engaged with. Next, the pillar type gripper 10 is shown in FIG.
Driven by the geared motor 36 with a brake in the direction of the arrow indicated by B and B, it rotates 360 ° and stops in the state indicated by B in FIG.

Next, the turntable 2 is started, makes one rotation as shown in C of FIG. 7 and D to F of FIG. 8, and stops in the state of F of FIG. During this time, the pillar-shaped gripper 10 was rotated together with the rotary table 2 while holding the end of the stretch film F, unwound from the film unwinding device 5, stretched by the drive roller stretching mechanism 6, and tensioned. The stretch film F is wrapped around the article to be packaged 9. At this time, it is preferable that the speed at which the drive roller stretching mechanism 6 feeds the stretched stretched film F is set to be slightly higher than the speed at which the rotating packaged object 9 pulls the stretched film 9. (See French Patent Application Publication No. 2281275)

When the rotary table 2 thus makes one rotation and stops at the position shown in F of FIG. 8, the lock taper cone 8 is lowered by the operation of the air cylinder 35, and is provided on the top of the pillar-type gripper 10. It is inserted into the receiving hole 11 of the tapered cone, and the pillar-shaped gripper 10 is fixed. Next, the swing arm 20 swings by the operation of the air cylinder 31, and the chuck 29 causes the pillar gripper 1 to move.
Engage with 0 at its root. The state at this time is shown in FIG. That is, the tip (rolling start end) of the stretch film F is clamped by the fingers 12 and 13 of the columnar gripper 10 at the position on the left side of FIG. In addition, the end portion of the stretch film F is wound around the film guide rollers 21 and 22 of the swing arm 20 and the pillar gripper 10.
It is sandwiched between the anti-slip members 17 and 18 so as not to return. Also, the pillar type gripper 10
Since air is not yet supplied to the air tube 16 attached to the stretch film F, the stretch film F is not pressure-bonded to the impulse heat sealer 26, and the heat sealer itself is not energized. Hot wire cutter 27
Also, the pushing blade 28 stands by at the position before the operation.

Next, as shown in FIG. 11, a pillar-type gripper 1
No. 0 air cylinder 15 is actuated, the fingers 13 are retracted, the winding start end of the stretch film F is released, and then the hot wire cutter 27 is energized as shown in FIG. 12, and at the same time the air cylinder 33 is actuated. The heat wire cutter 27 is moved forward to cut the end portion of the stretch film F. When the cutting is completed, the energization is stopped, the air cylinder 33 operates again, and the hot wire cutter 27 returns to the origin. One of the cut ends is sandwiched between the film guide roller 21 and the anti-slip member 17, and the other end is sandwiched between the film guide roller 22 and the anti-slip member 18, respectively.

Next, as shown in FIG. 13, the air tube 1
6 is supplied with air, and the stretch film F is pressure-bonded to the impulse heat sealer 28, the heat sealer 28 is energized, and the winding start end portion and the winding end portion of the stretch film F are cut toward the packaged object. Heat seal. Then, as shown in FIG. 14, the air cylinder 34 is operated to move the pushing blade 28 forward, so that the stretch film F sandwiched between the film guide roller 22 and the anti-slip member 18 (that is, not yet heat-sealed). Cut one end) with fingers 12 and 13
Push in between. As already explained with reference to FIG.
Pushing blade 28 of swing arm 20 and pillar-type gripper 1
A plurality (or a plurality of groups) are attached to the fingers 12 and 13 of 0 at positions crossing each other upward and downward, and the pushing blade 28 pushes the film forward,
The film is placed on a portion extruded by the pushing blade 28,
The lower part is pushed between the fingers 12 and 13.

Next, as shown in FIG. 15, the air cylinder 14 is actuated, the fingers 12 move forward, and the cut end of the stretch film F pushed by the pushing blade 28 is moved to the finger 13 at the position on the right side of the drawing. Sandwich between. (This cut end becomes the winding start end in the next step.) Next, as shown in FIG.
4, 15 are activated at the same time, and the fingers 12, 13 are
The fingers are moved in the left direction in the drawing while holding the end portion of the stretch film F therebetween.

Next, air is evacuated from the air tube 16, the air cylinder 35 operates (for locking), the taper cone 8 rises, the air cylinder 32 operates, the chuck 29 returns to the origin, and the columnar gripper 10 is moved. The engagement with the swing arm 20 is released, and then the air cylinder 31 is operated to return the swing arm 20 to the original point, and the stretch-sealed end of the stretch film F is released. In this way, the periphery of the article to be packaged 9 is wrapped with the tensioned one-layer stretch film F. This state is shown in FIG. Next, the package pressing device 7 returns to the origin by the operation of the air cylinder 30, the chain conveyor is automatically started in response to the carry-in acceptance signal from the downstream device, and the stretch-wrapped packaged product is transferred to the downstream device. Unpack and complete one packaging cycle.

In the apparatus of the present invention, the tensioning device for tensioning the stretch film comprises at least two rollers forcibly driven at the above-mentioned different peripheral speeds, and the stretch film is stretched between these rollers. In addition to the driving roller stretching mechanism to be added, a suitable film tension detection mechanism is added to the stretching mechanism to keep the tension of the stretch film wrapped around the object to be wrapped substantially constant, and thus the speed of the stretch film delivered from the stretching mechanism. May be controlled.

Depending on the required packaging specifications, a structure having a combination of a brake roller provided with an electromagnetic brake and a guide roller for bringing a film into contact with the periphery of the brake roller may be used. The device for pressing the object to be packaged used in the device of the present invention may be of the type that can be moved up and down by the air cylinder described above, or it can be moved up and down by a chain, belt or rope driven by a motor to load the entire weight of the device to be pressed. It may be of a type that stabilizes the package.

Further, when the film from the heat-sealed portion to the cut end hangs downward on the package body stretch-wrapped by the device of the present invention and causes a trouble in cargo handling, the hung-down portion is used as the package body. It may be fixed on the stretch film on the side wall by heat-sealing a plurality of lines parallel to the pulling direction of the stretch film or at an angle of 45 °.
(See Japanese Utility Model Publication No. 63-23298)

In addition, the diameter of the rotary table and the depth dimension of the apparatus, which are required for the design of the apparatus of the present invention, are different from those of the conventional rotary table type automatic stretch wrapping machine for the objects having the same size. Absent. Therefore, it is possible to match the main size on the layout of the existing equipment, and it is possible to avoid a layout change that requires extra cost when replacing the existing equipment.

[0032]

As described above in detail, according to the present invention, the object to be packaged is stabilized by a pressing device on the rotary table equipped with a conveyor for loading and unloading the object to be packaged. While making one revolution, the stretch film wider than the height of the object to be wrapped can be tensioned, and it can be wound around the object to be wrapped only once to tighten and fix the object to be wrapped,
Further, it is possible to provide a full-web type automatic stretch wrapping machine capable of matching main dimensions in layout with a conventional rotary table type automatic stretch wrapping machine for objects to be packaged having the same size.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing an overall image of an embodiment of a device of the present invention.

2 is a schematic side view of the device of FIG.

FIG. 3 is a schematic plan sectional view of a pillar-type gripper.

FIG. 4 is a schematic side sectional view of a rotary table.

FIG. 5 is a schematic plan sectional view of a swing arm.

FIG. 6 is a schematic perspective view of a pillar gripper and a swing arm.

7A to 7C are schematic plan views for explaining the operation of the apparatus of FIG. 1, and A to C show states of respective stages from the start of operation to the middle.

8 is a schematic plan view for explaining the operation of the apparatus of FIG. 1 subsequent to FIG. 7C, and D to F show states of respective stages during the operation.

9 is a schematic plan view for explaining the operation of the apparatus of FIG. 1, showing a state following F of FIG. 8;

FIG. 10 is a schematic plan view for explaining the operation of the pillar-type gripper and the swing arm subsequent to FIG.

11 is a schematic plan view for explaining the operation of the pillar-type gripper and the swing arm following FIG.

FIG. 12 is a schematic plan view for explaining the operation of the pillar gripper and the swing arm following FIG. 11.

13 is a schematic plan view for explaining the operation of the column gripper and the swing arm following FIG.

FIG. 14 is a schematic plan view for explaining the operation of the column gripper and the swing arm following FIG.

FIG. 15 is a schematic plan view for explaining the operation of the pillar gripper and the swing arm following FIG.

16 is a schematic plan view for explaining the operation of the pillar gripper and the swing arm following FIG.

17 is a schematic plan view of the device of FIG. 1, showing the condition following FIG.

[Explanation of symbols]

 1 Base Frame 2 Rotating Table 3 Chain Conveyor 4 Frame 5 Film Unwinding Device 6 Drive Roller Stretching Mechanism (which is a Tension Providing Device) 7 Packing Material Holding Device 8 (for Locking) Tapered Cone 9 Packing Material 10 Column Type Gripper 11 Taper cone receiving hole 12, 13 Finger 14, 15 Air cylinder 16 Air tube 17, 18 Anti-slip member 19 Chuck receiver 20 Swing arm 21, 22 Film guide roller 23 Brake shoe 24, 25 Spring 26 Impulse heat sealer 27 Hot wire cutter 28 Pushing blade 29 Chuck 30, 31, 32, 33, 34, 35 Air cylinder 36, 37 (with brake) Geared motor 38, 39 Slip ring 40, 41 Rotary joint 42 Motor F Retchifirumu

Claims (5)

(57) [Claims] 1. A rotary table provided with a conveyor for loading and unloading an article to be packaged, and a gantry provided on a base frame independently of the table. The gantry has a width wider than the height of the article to be packaged. In a full-web type automatic stretch wrapping machine provided with a film unwinding device for unwinding the winding of a wide stretch film and a tension applying device for tensioning the film, the stretch is provided on the rotary table near its periphery. The tip of the film is clamped over the entire width of the film, and a pillar-type gripper that rotates 360 ° at the time of starting is attached, and a pushing blade that presses the stretch film between the fingers of the pillar-type gripper on the base frame, and a packaged object. A heat sealer that heat-bonds the winding start end and the winding end of the film wound around the object, and the stretch film in front. A full-web type automatic stretch wrapping machine including a heat sealer and a knife mechanism for cutting between the fingers, and provided with a swing arm that swings toward the pillar-shaped gripper immediately after the rotary table is stopped. . 2. The full-web type automatic stretch wrapping machine according to claim 1, further comprising: a device for pressing an object to be packaged that moves up and down along the gantry. 3. The driving roller stretching mechanism for stretching the stretch film between the rollers, wherein the tension applying device comprises at least two rollers forcibly driven at different peripheral speeds. Full web type automatic stretch wrapping machine. 4. The full-web type automatic stretch wrapping machine according to claim 3, wherein the speed of the stretch film fed from the drive roller stretching mechanism is controlled by an appropriate film tension detecting mechanism. 5. The full-web type automatic stretch wrapping machine according to claim 1, wherein the tension applying device comprises a brake roller provided with an electromagnetic brake and a guide roller for bringing a film into contact with the periphery of the brake roller.