CN110844520B

CN110844520B - Tire cylinder conveying device and method

Info

Publication number: CN110844520B
Application number: CN201911312810.XA
Authority: CN
Inventors: 赵衍刚; 莫俊飞
Original assignee: Safe Run Intelligent Equipment Co Ltd
Current assignee: Safe Run Intelligent Equipment Co Ltd
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2021-07-20
Anticipated expiration: 2039-12-18
Also published as: CN110844520A

Abstract

The invention discloses a tire tube conveying device and a method, belonging to the technical field of tire building machines, wherein the tire tube conveying device comprises a conveying belt and a turnover assembly, a tire tube can be vertically placed on the conveying belt, and the conveying belt comprises a first conveying belt and a second conveying belt which are sequentially arranged along a conveying direction; the turnover assembly is located the second conveyer belt is kept away from the one end of first conveyer belt, the turnover assembly includes the roll-over stand, the roll-over stand is including receiving the first supporting part of child section of thick bamboo and can supporting the second supporting part of child section of thick bamboo, the roll-over stand can drive child section of thick bamboo upset settlement angle. The tire tube conveying method adopts the tire tube conveying device to convey the tire tubes, so that the tire tubes are automatically turned over, a manipulator can conveniently grab the tire tubes, the labor intensity is reduced, the conveying efficiency is improved, and the time is saved.

Description

Tire cylinder conveying device and method

Technical Field

The invention relates to the technical field of tire building machines, in particular to a tire cylinder conveying device and method.

Background

In the existing tire forming equipment, when a tire cylinder is transferred, the tire cylinder is generally flatly placed on a conveying line and is easy to deform, so that the roundness of the tire cylinder is poor, and the forming quality is influenced. Along with the transport of transfer chain, take the child section of thick bamboo by the manual work and place in order to carry out the shaping operation, waste time and energy, lead to production efficiency low.

Disclosure of Invention

The invention aims to provide a tire cylinder conveying device and method, which aim to solve the technical problems that the tire cylinder is easy to deform and low in conveying efficiency in the tire cylinder conveying process in the prior art.

As the conception, the technical scheme adopted by the invention is as follows:

a tire drum delivery device comprising:

the tire drum can be vertically placed on the conveying belt, and the conveying belt comprises a first conveying belt and a second conveying belt which are sequentially arranged along the conveying direction;

the overturning assembly is located the second conveying belt is kept away from one end of the first conveying belt, the overturning assembly comprises an overturning frame, the overturning frame comprises a first supporting portion capable of receiving the tire tube and a second supporting portion capable of supporting the tire tube, and the overturning frame can drive the tire tube to overturn for a set angle.

The first supporting part comprises at least two first supporting rods arranged at intervals, the distance between the first supporting rods is smaller than the diameter of the tire tube, the second supporting part comprises at least two second supporting rods arranged at intervals, and the distance between the second supporting rods is smaller than the diameter of the tire tube.

The second conveying belt comprises a plurality of plate chains arranged at intervals, and the first supporting rods can be inserted between the adjacent plate chains.

The tyre cylinder conveying device further comprises a first detection switch, and the state of the first conveying belt is controlled according to a signal of the first detection switch.

The tire tube conveying device further comprises a second detection switch, and the state of the turnover frame is controlled according to a signal of the second detection switch.

The tire tube overturning device is characterized by further comprising a positioning assembly, wherein the positioning assembly can drive the tire tube after overturning to be positioned at a preset position.

Wherein the positioning assembly comprises:

the two rollers are arranged at intervals, the tire cylinder after being turned over can be supported between the two rollers, and the rollers can drive the tire cylinder to rotate;

an identifier capable of identifying indicia on the outer surface of the rotating tyre drum to locate the tyre drum in a preset position.

A tire drum conveying method using the tire drum conveying device as described above, comprising:

step 1: vertically placing the tyre cylinder on a conveying belt, starting a first conveying belt and a second conveying belt, detecting the position of the tyre cylinder, and stopping conveying by the first conveying belt when the nth tyre cylinder is positioned on the second conveying belt;

step 2: the second conveyer belt continues to convey, and the upset subassembly is located initial position, and when nth the child section of thick bamboo was located first supporting part, the second conveyer belt stops to carry, and the roll-over stand drives nth the child section of thick bamboo upset settlement angle for nth the child section of thick bamboo supports in order to be located the position of waiting to snatch on the second supporting part.

Wherein, child section of thick bamboo conveyor still includes the locating component, the locating component includes two rollers that the interval set up, after step 2, still includes:

and step 3: the tyre cylinder is supported between the two rollers after being turned over, and can be automatically centered under the action of self gravity;

and 4, step 4: the roller rotates to drive the tire cylinder to rotate;

the positioning assembly further comprises an identifier, and in step 4, when the tyre cylinder rotates, the identifier identifies the mark on the tyre cylinder so as to position the tyre cylinder at a preset position.

In step 1, when the first conveying belt stops conveying, if the position of the (n + 1) th tyre cylinder is detected to be changed, an alarm device is triggered.

The invention has the beneficial effects that:

according to the tire cylinder conveying device, the tire cylinder is vertically placed on the conveying belt, so that the tire cylinder can be prevented from deforming; carry a child section of thick bamboo forward by first conveyer belt, when a child section of thick bamboo reachs the second conveyer belt, first conveyer belt stops to carry, along with the transport of second conveyer belt, a child section of thick bamboo reachs the first supporting part of upset subassembly, the second conveyer belt stops to carry, a child section of thick bamboo is received to first supporting part, the roll-over stand drives a child section of thick bamboo upset settlement angle for a child section of thick bamboo supports in the second supporting part, realize the automatic upset of a child section of thick bamboo, the manipulator of being convenient for snatchs a child section of thick bamboo, labor intensity is reduced, the conveying efficiency is improved, and the time is saved.

Drawings

FIG. 1 is a schematic structural diagram of a tire drum conveying device provided by an embodiment of the invention;

FIG. 2 is a schematic view of a portion of the tire drum delivery apparatus of FIG. 1;

fig. 3 is an enlarged view at a in fig. 2;

FIG. 4 is a schematic structural view of a tire drum conveying device provided by an embodiment of the invention when conveying a tire drum;

FIG. 5 is a schematic structural view of a tire drum conveying device for inverting a tire drum according to an embodiment of the present invention;

fig. 6 is a partial structural schematic view of the tire drum transfer device in fig. 5.

In the figure:

10. a tire tube;

11. a first conveyor belt; 12. a second conveyor belt; 13. a support frame; 131. a chute;

21. a roll-over stand; 211. a first support bar; 212. a second support bar; 213. a guide wheel; 22. a turning shaft; 23. a power mechanism; 24. a crank; 241. a spacing pin;

31. a roller; 32. an identifier;

41. a first detection switch; 42. a second detection switch; 43. and a third detection switch.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

In the description of the present invention, unless expressly stated or limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.

Referring to fig. 1 to 6, an embodiment of the present invention provides a tire tube conveying device, including a conveying assembly, a turning assembly, a positioning assembly, a detection assembly, and a control system, where the conveying assembly is configured to convey a tire tube 10, the turning assembly is capable of receiving the tire tube 10 conveyed in place and driving the tire tube 10 to turn over by a set angle, and the positioning assembly is capable of driving the turned tire tube 10 to be positioned at a preset position, so as to facilitate accurate grasping by a manipulator. The detection assembly can detect the position of the tyre cylinder 10 and transmit signals to the control system, and the control system controls the conveying assembly, the overturning assembly and the positioning assembly. As described in detail below.

The conveying assembly comprises a conveying belt, a driving roller for supporting the conveying belt and a supporting frame 13 for mounting the driving roller. The tyre tube 10 can be vertically placed on the conveying belt, namely the axis of the tyre tube 10 is perpendicular to the conveying surface of the conveying belt, so that the tyre tube 10 can be prevented from being deformed, and the roundness of the tyre tube 10 is ensured. In this embodiment, the driving roller is driven by a motor, which will not be described in detail herein.

The conveyer belt includes along first conveyer belt 11 and the second conveyer belt 12 that transmission direction set gradually, and the upset subassembly is located the one end that first conveyer belt 11 was kept away from to second conveyer belt 12. A plurality of tyre cylinders 10 are arranged on the conveyor belt at intervals, so that when one tyre cylinder 10 is conveyed to the second conveyor belt 12, the adjacent tyre cylinder 10 is positioned on the first conveyor belt 11, and the first conveyor belt 11 can be stopped at the moment, and the interference between the adjacent tyre cylinders 10 is prevented. The first conveying belt 11 and the second conveying belt 12 are driven by a motor, and power transmission of the front and rear conveying belts is realized through an electromagnetic clutch.

The overturning assembly comprises an overturning frame 21, wherein the overturning frame 21 can rotate to receive the tire tube 10 and drive the tire tube 10 to overturn for a set angle. As the tire tube 10 is conveyed forward on the second conveyor belt 12, the tire tube 10 is conveyed to the turning frame 21, and when the turning frame 21 rotates, the tire tube 10 is driven to turn.

The roll-over stand 21 can drive the child section of thick bamboo 10 and overturn certain angle to waiting to snatch the position, at the child section of thick bamboo 10 of waiting to snatch the position, the manipulator of being convenient for snatchs. In the present embodiment, the flip angle is 90 degrees.

The overturning assembly further comprises an overturning shaft 22 and a power mechanism 23 for driving the overturning shaft 22 to rotate, and the overturning frame 21 is fixedly connected with the overturning shaft 22. The two power mechanisms 23 are respectively arranged at two ends of the turning shaft 22 to ensure the stress balance of the turning shaft 22.

In this embodiment, the power mechanism 23 includes a cylinder and a crank 24, one end of the cylinder is rotatably connected to the support frame 13, the other end of the cylinder is an output end, the output end of the cylinder is rotatably connected to the crank 24, and the crank 24 is connected to the turning shaft 22. The output end of the cylinder extends and retracts, and the turnover shaft 22 is driven to rotate through a crank 24.

Both ends of the turning shaft 22 penetrate through the support frame 13, the middle part of the crank 24 is fixedly connected with the turning shaft 22, and the crank 24 rotates around the axis of the turning shaft 22. Be provided with on support frame 13 and be curved spout 131, the one end of crank 24 rotates with the output of cylinder to be connected, the other end and the support frame 13 sliding connection of crank 24, is provided with spacer pin 241 on the crank 24, and spacer pin 241 is arranged in spout 131, plays limiting displacement to crank 24, and the setting of spout 131 has retrained the rotation angle of crank 24, prevents that roll-over stand 21 from rotating the excessive position.

The roll-over stand 21 is L-shaped, and comprises a first supporting part and a second supporting part which are vertically arranged, and the tire tube 10 is conveyed to the first supporting part along with the forward conveying of the tire tube 10 on the second conveying belt 12. When the roll-over stand 21 rotates, the first supporting part drives the tire tube 10 to turn over, and when the roll-over stand 21 rotates in place, the second supporting part supports the tire tube 10.

The first support portion includes at least two first support rods 211 arranged at intervals to provide support to the tire cylinder 10. In this embodiment, the first support portion includes two first support rods 211 arranged at intervals, and the distance between the two first support rods 211 is smaller than the diameter of the tire cylinder 10. The second support portion includes at least two second support rods 212 arranged at intervals. In the present embodiment, the second support portion includes two second support rods 212 arranged at intervals, and the distance between the two second support rods 212 is smaller than the diameter of the tire cylinder 10. After the tire tube 10 is turned over by the turning frame 21, the two second support bars 212 support the tire tube 10.

The two first support bars 211 are arranged so as to cooperate with the second conveyor belt 12 to receive the tyre drum 10. Specifically, the second conveyor belt 12 includes a plurality of plate chains arranged at intervals, and the first support bars 211 can be inserted between the adjacent plate chains. In order to facilitate the reception of the tyre cylinder 10 without interfering with the transport of the second conveyor belt 12, the first support bars 211, after being inserted between adjacent plate links, have a position slightly lower than the position of the upper surface of the plate link, so that the tyre cylinder 10 can be transferred to the front end of the second conveyor belt 12, so that the first support bars 211 can fully lift the tyre cylinder 10 in preparation for the turning. In this embodiment, the second conveyor belt 12 includes three plate chains arranged at intervals.

Each first support rod 211 is provided with a plurality of guide wheels 213 side by side, and the axes of the guide wheels 213 are perpendicular to the conveying direction of the conveying belt. The guide wheel 213 is arranged to reduce friction between the first support rod 211 and the tire cylinder 10, so that the tire cylinder 10 can be smoothly transported from the second conveyor belt 12 to the first support rod 211.

The detection assembly comprises a first detection switch 41, a second detection switch 42 and a third detection switch 43, wherein the first detection switch 41 and the second detection switch 42 are both arranged on one side of the second conveying belt 12, and the third detection switch 43 is arranged on one side of the first conveying belt 11. In the process of conveying the tyre tube 10, a plurality of tyre tubes 10 are arranged on the conveyor belt at intervals, when the nth tyre tube 10 is conveyed to the second conveyor belt 12 by the first conveyor belt 11, the first detection switch 41 detects a signal and transmits the signal to the control system, and the control system controls the first conveyor belt 11 to stop transmission. At this time, the second conveyor belt 12 is still in a transmission state, when the nth tire tube 10 is completely located on the first support rod 211, that is, reaches the front end of the second conveyor belt 12, the second detection switch 42 detects a signal and transmits the signal to the control system, the control system controls the turning frame 21 to rotate and controls the second conveyor belt 12 to stop transmission, and the turning frame 21 drives the nth tire tube 10 to turn. Here, the working principle of the control system is not described in detail, and reference may be made to the prior art.

After the control system controls the first conveying belt 11 to stop transmission, in the process that the nth tire drum 10 is conveyed, if the third detection switch 43 detects that the position of the (n + 1) th tire drum 10 changes, which indicates that the first conveying belt 11 is in failure, the first conveying belt 11 is still conveying, and at this time, the alarm device is triggered.

The positioning assembly is connected with the roll-over stand 21, the positioning assembly comprises two rollers 31 arranged at intervals, and the tire tube 10 can be supported between the two rollers 31. Because the two rollers 31 are spaced, the tire tube 10 is cylindrical, and the gap between the two rollers 31 is smaller than the diameter of the tire tube 10, the tire tube 10 can be supported between the two rollers 31, the tire tube 10 can be automatically centered under the action of self gravity, and the labor is saved.

One roller 31 is provided on each second support bar 212. The second support rods 212 support the roller 31, and the roller 31 is located on the opposite side of the two second support rods 212, so that the tire tube 10 is supported and driven to rotate by the tire tube 10, and interference is prevented.

The positioning assembly further comprises an identifier 32, the identifier 32 being arranged on the turning frame 21 and being capable of identifying the mark on the outer surface of the rotating tyre drum 10 so as to position the tyre drum 10 in a predetermined position. All the tyre tubes 10 rotate to preset positions and are grabbed by the manipulator, so that the automatic tube loading function of the robot is realized, and the automatic accurate distribution of the joints of the semi-finished materials in the circumferential direction of the tyre building drum is realized. The joints refer to the parts of the strip-shaped materials which are connected end to end, one joint is formed by adhering one layer of the materials, and a plurality of joints formed by multiple layers of the materials need to be uniformly distributed in the circumferential direction. In the feeding stage, when the material is located in the feeding frame, the position of the code is fixedly arranged at a certain position of the feeding frame, so that the position of the code pasting machine relative to each material is fixed, the length of each material is known and unchanged, the position of the code pasting machine from the head end of the material can be obtained, and the position of the joint can be calculated according to the position of the code pasting machine from the head end of the material. Therefore, the joint positions of the ply, the inner liner and the sidewall can be automatically determined from the position of the code when the tire tube 10 is produced. Because the roller 31 rotates to drive the tire tube 10 to rotate, in the rotating process of the tire tube 10, the identifier 32 identifies the tire tube 10, when the identifier 32 successfully identifies the mark on the tire tube 10, the roller 31 stops rotating, the positioning of the tire tube 10 is realized, and at the moment, the position of the tire tube 10 is a preset position, so that the manipulator can conveniently grab the tire tube.

In this embodiment, the identifier 32 is a scanner, and the tire drum 10 is provided with a bar code, and the scanner is used for scanning the bar code. The roller 31 rotates to drive the tire tube 10 to rotate, the scanner scans the tire tube 10 in the rotation process of the tire tube 10, when the scanner scans the bar code on the tire tube 10 successfully, the roller 31 stops rotating, positioning of the tire tube 10 is achieved, and the manipulator can grab the tire tube 10 conveniently at the position of the tire tube 10. Wherein, the roller 31 can be driven by a motor, and when the scanner successfully scans the bar code on the tire tube 10, the motor stops rotating.

When the scanner continuously scans for a set time length and does not scan successfully, the alarm device is triggered. The roller 31 drives the tire tube 10 to rotate at a preset speed, if the tire tube 10 rotates for more than a set time, scanning is still unsuccessful, the condition that bar codes are attached is judged to be abnormal, equipment is shut down to give an alarm, and manual processing is carried out. Specifically, the roller 31 drives the tire cylinder 10 to rotate at 10-40 m/min, theoretically, the time of one turn of the 24-inch tire cylinder 10 is about 5 seconds, if the tire cylinder 10 rotates for more than 10 seconds, scanning is still unsuccessful, it is judged that bar code pasting is abnormal, equipment is shut down, an alarm is given, and manual processing is carried out.

The identifier 32 is disposed on one of the second support bars 212 to facilitate detection of the outer surface of the tire cylinder 10.

The embodiment of the invention also provides a tire cylinder conveying method, which adopts the tire cylinder conveying device and comprises the following steps:

step 1: the tyre cylinder 10 is placed vertically on a conveyor belt.

Specifically, the tyre tube 10 is placed on the first conveyor belt 11, and the nth tyre tube 10 is conveyed to the second conveyor belt 12 along with the transmission of the first conveyor belt 11, at this time, the first detection switch 41 sends a signal to the control system, and the control system controls the first conveyor belt 11 to stop conveying.

When the first conveying belt 11 stops conveying, the second conveying belt 12 still conveys the nth tyre cylinder 10, and if the position of the (n + 1) th tyre cylinder 10 is detected to be changed, an alarm device is triggered.

Step 2: the second conveyer belt 12 continues to carry, and the upset subassembly is located initial position, and when the nth child section of thick bamboo 10 was carried to upset subassembly department, the upset subassembly received child section of thick bamboo 10 and drives the upset of nth child section of thick bamboo 10 setting angle to waiting to snatch the position.

Specifically, the roll-over stand 21 is in the initial position, in which the first support bar 211 is inserted between adjacent plate links. Along with the transmission of the second conveyer belt 12, when the nth tire casing 10 is completely located on the first supporting portion, that is, on the first supporting rod 211, that is, when reaching the foremost end of the second conveyer belt 12, the second detection switch 42 sends a signal to the control system, the control system controls the second conveyer belt 12 to stop conveying and controls the turning frame 21 to rotate to drive the tire casing 10 to turn over for a set angle, so that the tire casing 10 is supported on the second supporting portion to be located at a position to be grabbed, and at this time, the tire casing 10 is horizontally placed, so that the manipulator is convenient to grab.

And step 3: when the turning frame 21 is turned by 90 degrees and then stops, the tire tube 10 can be supported between the two rollers 31 after being turned over, so that the tire tube 10 can be automatically centered under the action of self gravity.

And 4, step 4: the roller 31 rotates to drive the tire tube 10 to rotate, the identifier 32 identifies the tire tube 10, and when the identifier 32 successfully identifies the mark on the tire tube 10, the roller 31 stops rotating.

During the rotation of the tire tube 10, the identifier 32 identifies the surface of the tire tube 10, and when the identifier 32 successfully identifies the mark on the tire tube 10, the roller 31 stops rotating, and the tire tube 10 is located at the position convenient for the manipulator to grasp.

If the identifier 32 continues to identify the set time length and the identification is not successful, the alarm device is triggered. The alarm device is electrically connected with the control system, and is not described herein again.

The foregoing embodiments are merely illustrative of the principles and features of this invention, which is not limited to the above-described embodiments, but rather is susceptible to various changes and modifications without departing from the spirit and scope of the invention, which changes and modifications are within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A tire drum delivery apparatus, comprising:

the tyre drum (10) can be vertically placed on the conveying belt, and the conveying belt comprises a first conveying belt (11) and a second conveying belt (12) which are sequentially arranged along the conveying direction;

the overturning assembly is positioned at one end, far away from the first conveying belt (11), of the second conveying belt (12), and comprises an overturning frame (21), the overturning frame (21) comprises a first supporting part capable of receiving the tire tube (10) and a second supporting part capable of supporting the tire tube (10), and the overturning frame (21) can drive the tire tube (10) to overturn for a set angle;

the positioning assembly can drive the turned tire cylinder (10) to be positioned at a preset position; the positioning assembly comprises two rollers (31) which are arranged at intervals, the tire tube (10) after being turned over can be supported between the two rollers (31), and the rollers (31) can drive the tire tube (10) to rotate; an identifier (32) capable of identifying markings on the outer surface of the rotating tyre drum (10) to position the tyre drum (10) in a preset position.

2. Tyre drum conveying device according to claim 1, characterized in that the first support comprises at least two first support bars (211) arranged at intervals, the distance between the two first support bars (211) being smaller than the diameter of the tyre drum (10), and the second support comprises at least two second support bars (212) arranged at intervals, the distance between the two second support bars (212) being smaller than the diameter of the tyre drum (10).

3. Tyre drum conveying device according to claim 2, characterized in that the second conveyor belt (12) comprises a plurality of plate chains arranged at intervals, the first support bar (211) being insertable between adjacent plate chains.

4. Tyre drum transfer device according to claim 1, characterized in that it further comprises a first detection switch (41), the state of the first conveyor belt (11) being controlled in dependence of the signal of the first detection switch (41).

5. Tyre drum transfer device according to claim 1, characterized in that it further comprises a second detection switch (42), the state of the turning frame (21) being controlled in dependence of the signal of the second detection switch (42).

6. A tyre drum conveying method, characterized in that the tyre drum conveying device according to any one of claims 1-5 is used, comprising:

step 1: vertically placing a tyre cylinder (10) on a conveying belt, starting a first conveying belt (11) and a second conveying belt (12), detecting the position of the tyre cylinder (10), and stopping conveying by the first conveying belt (11) when the nth tyre cylinder (10) is positioned on the second conveying belt (12);

step 2: the second conveying belt (12) continues to convey, the overturning assembly is located at an initial position, when the nth tire tube (10) is located on the first supporting portion, the second conveying belt (12) stops conveying, the overturning frame (21) drives the nth tire tube (10) to overturn for a set angle, and the nth tire tube (10) is supported on the second supporting portion to be located at a position to be grabbed.

7. The tyre drum conveying method according to claim 6, characterized in that the tyre drum conveying device further comprises a positioning assembly comprising two rollers (31) arranged at intervals, and after step 2, further comprises:

and step 3: the tyre cylinder (10) is supported between the two rollers (31) after being overturned, and the tyre cylinder (10) can be automatically centered under the action of self gravity;

and 4, step 4: the roller (31) rotates to drive the tire cylinder (10) to rotate;

the positioning assembly further comprises an identifier (32), and in the step 4, when the tyre cylinder (10) rotates, the identifier (32) identifies the mark on the tyre cylinder (10) so as to position the tyre cylinder (10) at a preset position.

8. The tyre drum conveying method according to claim 6, characterized in that in step 1, when the first conveyor belt (11) stops conveying, if the position of the (n + 1) th tyre drum (10) is detected to change, an alarm device is triggered.