EP2324199A1

EP2324199A1 - Method of cracking rock material, and breaking device

Info

Publication number: EP2324199A1
Application number: EP09812746A
Authority: EP
Inventors: Ilkka Lahdelma
Original assignee: Sandvik Mining and Construction Oy
Current assignee: Sandvik Mining and Construction Oy
Priority date: 2008-09-15
Filing date: 2009-09-10
Publication date: 2011-05-25
Also published as: FI20085864A; FI20085864A0; AU2009290782B2; ZA201102797B; AU2009290782A1; JP5396477B2; WO2010029220A1; CA2734387A1; CN102149899A; CN102149899B; EP2324199A4; CA2734387C; JP2012503114A; FI122760B

Abstract

The invention relates to a method of generating cracking and to a breaking device. With a drilling unit (12) of the breaking device (4) a drill hole (30) is drilled in a block (5), after which the drilling unit is indexed away from the drill hole, and a cracking unit (13) is moved to its place. During the indexing, a frame (24) of the breaking device is kept immovable relative to the drill hole. The indexing is performed by means of an indexing actuator (28, 59) and in the control of at least one support member (26, 59) along a predeterminedpath of movement (L, R). The breaking device is an independent supplementary device and comprises a control system of its own, which is independent from the work machine.

Description

METHOD OF CRACKING ROCK MATERIAL, AND BREAKING DEVICE

BACKGROUND OF THE INVENTION

[0001] The invention relates to a method of generating cracking in rock material, for example when splitting blocks. In splitting, a breaking device is used which comprises a drilling unit and a cracking unit. First, a drill hole is drilled in the material to be operated on by means of a rock drill machine. After the drilling, the drilling unit is moved away from the point of the drill hole, and a cracking unit is moved to its place. Subsequently, a cracking tool is inserted into the drill hole and used to generate cracks in the rock. Further, the invention relates to a breaking device comprising the above components.

[0002] The field of the invention is defined in greater detail in the preambles of the independent claims of the application.

[0003] On building sites, road construction sites and other earth- moving sites, it is from time to time necessary to break oversized blocks which are too large to be transported and crushed. Traditionally, blocks have been broken by explosion but then the problem is that the working site must be cleared of people and equipment to guarantee safety. This naturally causes inconvenient interruptions on the construction site. To solve the problem, it has become common to use a breaking hammer to make blocks smaller. However, making an oversized block smaller with a breaking hammer may be laborious and time-consuming. Further, also when using a breaking hammer, some rock material may be thrown to the surroundings, which may cause problems on road construction sites, for example. It is also known to split oversized blocks by means of wedges. In such a case, a drill hole is drilled in a block with a separate rock drill machine, after which an elongated splitting tool is inserted into the drill hole. The cross-section of the splitting tool can be widened by wedging it hydraulically, whereby the tool generates cracking in the rock and eventually causes the block to split. The problem of this solution is, however, that a separate rock drill machine and splitting equipment are required and it is slow and laborious to operate them.

[0004] Publications US 5308149, US 6347837, US 6435096, Fl 113803 and JP 139286/1995 disclose rock drilling rigs in which the breaking device is arranged fixedly on the boom of the rock drilling rig. Rock drilling devices are work machines used in production within mining industry, there being no grounds for using them for breaking oversized blocks on earth- moving sites.

BRIEF DESCRIPTION OF THE INVENTION

[0005] An object of this invention is to provide a novel and improved method of generating cracking. Further, an object is to provide a novel and improved breaking device.

[0006] The method according to the invention is characterized by using a breaking device which is an independent supplementary device detachably connected to the boom of the work machine; and performing a work cycle relating to the drilling and cracking in the control of the breaking device's own control unit independently of the work machine.

[0007] The breaking device according to the invention is characterized in that the breaking device is an independent supplementary device detachably connectable to the boom of the work machine; and the breaking device comprises at least one control unit of its own, arranged to control the steps according to the work cycle of the breaking device independently of the control system of the work machine.

[0008] An idea of the invention is that the breaking device is an independent supplementary device which may be detachably attached to the boom of the work machine. The breaking device is independent also in such a way that it comprises a control unit of its own which is independent of the control unit of the work machine. The control unit of the breaking device controls the steps required by the work cycle of the breaking device after the breaking device has been positioned, by means of the boom of the work machine, at the point to be operated on.

[0009] An advantage of the invention is that an independent breaking device constructed as a supplementary device may be attached to the boom of any work machine used at the work site when there is a need to break large rocks and blocks, for instance. In such a case, no separate, laborious drill machine or cracking device is needed and, on the other hand, no rock drilling rig intended only for cracking is needed. The breaking device according to the invention increases the usability of a basic work machine, improving thus the efficiency of the working site.

[0010] The idea of an embodiment is that indexing takes place exactly along a predetermined path of movement. Thus, it is simple to implement the indexing mechanically without measuring and complex controlling of movements. Further, the indexing may take place without the operator actually seeing the point to be operated on. In indexing, the parallel feed beams of the drilling unit and cracking unit may move simultaneously.

[0011] The idea of an embodiment is that the indexing is carried out along a linear path of movement, supported by one or more linear control surfaces. An indexing actuator provides linear displacement.

[0012] The idea of an embodiment is that the indexing is carried out along a curved path of movement, supported by the turning centre. In such a case, the indexing actuator is a turning device.

[0013] The idea of an embodiment is that the indexing is carried out in a first direction of motion and a second direction of motion, which are opposite to each other. The drilling is carried out when the drilling unit is indexed in its initial position in the first direction of motion. After the drilling, indexing is carried out in the second direction of motion, whereby the cracking unit becomes positioned in the operating centre. Subsequently, the rock drill machine is again indexed in the first direction of motion to its initial position for new drilling. Before drilling a new drill hole, the breaking device is positioned roughly at the intended new drill hole by means of a boom.

[0014] The idea of an embodiment is that the indexing is carried out against predetermined physical limits. In such a case, the extreme positions of the indexing can be predetermined accurately by means of the limits. Furthermore, it is not necessary to measure and control the indexing movement accurately.

[0015] The idea of an embodiment is that the cracking device comprises an elongated cracking tool insertable into the drill hole. The cracking device comprises means for increasing the outer dimension of the cracking tool. The cracking tool may comprise two or more parts the distance of which from each other may be increased by inserting a wedge between them. The cracking tool may alternatively be another expanding member in which a change in the outer dimension may be based on its material properties, for example.

[0016] The idea of an embodiment is that the cracking device comprises means for feeding small charges into the drill hole. The high gas pressure generated in firing a small charge causes cracking to the rock material surrounding the drill hole. [0017] The idea of an embodiment is that the breaking device is constructed as a supplementary device which may be easily and quickly attached to the boom of a work machine by means of quick-fastening means, for instance. The breaking device is an independent unit comprising all actuators as well as auxiliary and control devices required by its operation. It is sufficient to convey operating energy from the work machine to the breaking device. Thus, the breaking device may be provided with hydraulic pressure to operate the actuators and with electric current to operate the control devices.

[0018] The idea of an embodiment is that the breaking device is constructed as a supplementary device of a work machine and comprises one or more control units of its own, arranged to control the functions of the breaking device automatically. In such a case, the breaking device can be operated by any operator of an excavator or the like work machine without any prior experience of rock drilling or techniques relating to rock drilling or cracking and splitting. The parameters and work cycle stages required by the operation have been preset in the control unit of the breaking device. The minimum requirement is that the operator only needs to position the breaking device in place in the object to be operated on by means of a boom and to start the automatic work cycle.

[0019] The idea of an embodiment is that the rock drill machine being a part of the breaking device is arranged inside a noise dampening housing. In such a case, noise generated by the drilling may be significantly reduced, and splitting blocks may also take place near residential areas. In some cases, it is also feasible to surround the whole drilling unit by a noise dampening housing.

BRIEF DESCRIPTION OF THE FIGURES

[0020] Some embodiments of the invention will be explained in greater detail in the attached drawings, in which

Figure 1 shows schematically a side view of an excavator the boom of which is provided with a breaking device according to the invention as a supplementary device;

Figure 2a shows schematically a side view of a breaking device according to the invention in a situation where drilling may begin; Figure 2b shows schematically a side view of the breaking device of Figure 2a in a situation where the cracking unit has been moved, supported by a linear guide, to the point of the drill hole;

Figures 3a and 3b show schematically and in an extremely simplified manner a side view of some cracking devices and their operating principles;

Figure 4 shows schematically a side view of a breaking device and some supplementary devices in connection with it;

Figures 5 and 6 show schematically a side view of some arrangements for storing a breaking device on a working site; and

Figures 7a and 7b show a front view of a breaking device, turned into two different operating positions.

[0021] For the sake of clarity, embodiments of the invention are shown simplified in the figures. Similar parts are denoted with the same reference numerals.

DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

[0022] Figure 1 shows an excavator 1 comprising a movable boom 2, a breaking device 4 being connected to a fastening piece 3 at the outer end of the boom. The structure and operation of the breaking device 4 is described in more detail in the context of Figures 2a and 2b. The breaking device 4 may be a supplementary device which may be connected to the place of the normal bucket of the excavator 1 when there is a need to split oversized blocks of rock 5 or other rock material at the work site. It is of course feasible to connect the breaking device 4 to the boom of any basic work machine by using appropriate coupling members. The breaking device 4 may comprise all auxiliary devices, actuators and control devices required, in which case operating it does not require any changes to the actual basic machine. From a pump 6 of the basic machine, pressure medium may be conveyed to the breaking device 4 along a feed channel, and the returning pressure medium may be conveyed back to the basic machine along a return line. Normally, such pressure medium connections are standard arrangements in connection with the fastening piece 3 of an excavator, for example. Further, there may be electrical connections between the basic machine and the breaking device 4, so that an independent control unit 7 in the breaking device 4 can be provided with the energy it needs. The basic machine has a control unit 8 of its own, the control means of which may be positioned in a cabin 9. Further, the breaking device 4 may comprise a remote control device 60 by means of which the operator of the work machine can start the work cycle of the breaking device from the cabin. The control unit 7 may also inform the operator via a remote control device that the drilling and splitting have been completed at the drilling hole and that the operator may move the breaking device to the next point to be operated on. The breaking device 4 may also comprise separate independent means to provide the flushing medium required. Thus, it may comprise a compressor 10 for providing a flushing air flow. Alternatively, in connection with the breaking device 4, there may be a fluid container 11 from which flushing medium can be supplied by means of a pump during the drilling.

[0023] Figures 2a and 2b show a breaking device 4 comprising a drilling unit 12 and a cracking unit 13. The drilling unit 12 comprises a rock drill machine 14 which may be moved on a first feed beam 15 by means of a first feed device 16. The rock drill machine 14 may comprise a precussion device 17 for generating impact pulses and transmitting them to the object to be operated on by means of a drill tool 18 connected to the rock drill machine. Further, the rock drill machine 14 may comprise a rotating device 19 for turning the drill tool 18 relative to its longitudinal axis during the drilling. The rock drill machine 14 may be any drill machine suitable for drilling a relatively short drill hole needed in cracking. The cracking unit 13 comprises a cracking device 20 which is movable, by means of a second feed device 21 , on a second feed beam 22 arranged in parallel with the first feed beam 15. The cracking device 20 may be an actuator arranged to change the cross-sectional dimension of the elongated cracking tool 23 to generate splitting forces in the drill hole. Further, the breaking device 4 comprises a frame 24 provided with a fastening part 25 to which the fastening piece 3 of the boom 2 can be attached, for example by means of fastening pins, fastening bolts, fastening claws or the like. The breaking device 4 may be attached to the boom 2 by means of one or more quick-fastening members in a quick and handy manner without disassembling structures or using tools. The frame 24 may be provided with one or more linear control surfaces 26. The feed beams 15 and 22 may be attached to a slide piece 27 which can be moved by means of one or more indexing actuators 28 along a linear path of movement L, supported by control surfaces 26. In this way, the drilling unit 12 can be indexed, in a manner shown in Figure 2a, to an operating centre 29, i.e. to the centre line of a drill hole 30 to be drilled, and further, the cracking unit 13 can be indexed, in a manner shown in Figure 2b, to the operating centre 29. Since the drilling unit 12 and the cracking unit 13 are both attached to the slide piece 27, they move simultaneously in the indexing. The indexing movement may take place in a first direction of motion and in a second direction of motion, which may be opposite to each other. The indexing movement may be restricted by means of physical limits 31 in both directions of motion. The limits 31 are pre-positioned in such a way that the indexing movement may be carried out in a simple manner towards a limit, as far as to the extreme position of the movement. Depending on the direction of motion, the drilling unit 12 or alternatively the cracking unit 13 becomes positioned in the operating centre 29. Controlling such a displacement is simple and accurate and does not require any measurement or calculation of the position. Further, the breaking device 4 may comprise a rock support 32 supported to the frame 24. The rock support 32 may be a rock spike, buffer or the like support member.

[0024] When blocks 5 are split with the breaking device 4 or when cracks are generated in rock, the rock support 32 is fitted by means of the boom 2 against the surface of the object to be operated on. Thus, rough positioning is first carried out by means of the boom 2. The rock support 32 is kept in place during the whole operation, whereby it prevents the frame 24 from moving relative to the object to be operated on. Further, the basic machine and its boom 2 are kept substantially immovable during the operation. The actual steps relating to generating cracks are performed independently of the basic machine. If the block 5 to be split is particularly large, several drill holes may be drilled and cracked on the same line. The drill hole line may be determined by means of laser, for example.

[0025] The control unit 7 of the breaking device 4 may be arranged to automatically control all work stages of the drilling and cracking as well as the indexing, and it may further attend to the control of auxiliary devices. In such a case, the operator of the basic machine does not necessarily have to be at all familiar with drilling or splitting technology. Parameters used in the drilling, such as the feed force to be used, impact power, rotation and drill hole length, may be preset in the control unit 7. Further, the drilling stages, such as collaring and actual drilling, may be preset in the control unit 7. The control unit 7 may also be arranged to control the cracking unit, the indexing device and, further, auxiliary actuators in connection with the breaking device, such as a flushing actuator and dust collection system, either completely automatically or interactively with the operator. The minimum task for the operator is just to position the breaking device at the desired operating point and to start an automatic work cycle. The control unit 7 may automatically control the drilling and wedging or cracking, after which it may further move the breaking device automatically into its initial position for a new work cycle. The control unit 7 may comprise a processor, programmable logic or the like as well as a memory member in which the required parameters and the control strategy can be stored.

[0026] Figure 3a shows the principle of a cracking device 20 in an extremely simplified manner. The cracking device 20 may comprise a hydraulic cylinder 33, which may be arranged to insert a wedge 34 into the inside of the cracking tool 23. The cracking tool 23 may be formed of at least two pieces 23a and 23b, which the wedge 34 may push apart in such a way that the outer dimension of the cracking tool 23 increases in the drill hole 30, causing thus extremely great splitting forces F in the block 5, whereby the block splits, or at least significant cracking is generated in it so that it splits when drilling and cracking are repeated one or more times on the same splitting line H. It is to be noted that the structure and operation of the cracking device and the cracking tool may also be different. The breaking device 4 may be equipped with a commercially available cracking device. It is also feasible to use a cracking device whose outer dimension is changed in a way other than by means of a mechanical wedge.

[0027] Figure 3b shows the principle of a second cracking device 20. The cracking device 20 may comprise means for feeding small charges 35 into the drill hole 30. In such a case, what is called small charge blasting is utilized, in which one or more small charges or cartridges contained in a propellant charge is/are fired in the drill hole so that a high gas pressure is generated, causing cracking 36 in the rock. Small charge blasting is applicable to splitting and breaking oversized blocks on earth-moving sites because in the same way as in splitting with a wedge, the working area does not have to be cleared of people and equipment. No rock material is thrown to the surroundings in small charge blasting but the method is safe and easily controllable. Thus, the operator of an excavator or the like work machine does not need any particular training or authorizations. Figure 3b shows, in an extremely simplified manner, a cartridge feed device 37, which may be arranged in place of the wedging splitting device shown in the preceding figures. The cartridge feed device 37 may comprise a feed station 38, from which the small charge 35 can be fed to the bottom of the drill hole 30 along a feed channel 39 insertable into the drill hole 30. Subsequently, the drill hole 30 may be sealed for instance by feeding from the feed channel into the drill hole some sealing material 40, for example water, which may be stored in a container 41. Alternatively, the drill hole 30 is sealed by means of the feed channel 39 or another mechanical sealing piece. The cracking device 20 may give an impulse which fires the small charge 35.

[0028] Figure 4 shows the breaking device 4 and some supplementary devices in connection with it. The breaking device 4 may be provided with a separate dust collection system 42 that may have a suction funnel 43 which is arranged at the mouth of the drill hole 30 to be drilled and from which dust may be sucked along a suction channel 44 to a filter unit 45. In connection with the filtering unit 45, there may be a suction device 46 for generating the negative pressure required, and a container 47 for collecting the dust separated by the filters. Figure 4 further shows a compressor 10, with which the generated flushing air flow can be conveyed along a flushing channel 48 to the drilling machine 14 and further through the drill tool 18 into the drill hole 30. It is also seen from the figure that the drill machine 14 may be arranged into the inside of a noise dampening housing 49, in which case drilling may be carried out also on working sites near residential areas without significant noise problems. In some cases, it is feasible to surround the whole drilling unit 12 by a noise dampening housing.

[0029] Figure 5 shows an arrangement for storing the breaking device 4 on the working site in such a way that it is easily detachable from the boom and easily reattachable to the boom of the work machine. The breaking device 4 may be provided with one or more legs 50, by means of which the breaking device 4 can be arranged in a horizontal direction against the ground. Thus, the fastening part 25 is readily available and it is easy to connect the boom to it. The legs 50 may be arranged fixedly in the breaking device 4.

[0030] Figure 6 shows a framework 51 , against which the breaking device 4 can be arranged in a vertical position, whereby it is easy to fit the fastening parts on the boom to the fastening part 25. The framework 51 is a separate piece which can be stored on the working site. The support members 50, 51 shown in Figures 5 and 6 may also be used as auxiliary equipment in maintenance, storing and transport of the breaking device 4.

[0031] Figures 7a and 7b show an alternative arrangement for indexing the drilling unit 12 and the cracking unit 13. The frame 24 of the breaking device 4 may be supported against a block by means of a rock support 32, whereby the frame 24 remains substantially immovable during the operation. The drilling unit 12 and the cracking unit 13 are arranged on a turning piece 57, which can be turned by means of a turning device 58 in indexing along a curved path of movement R relative to the turning centre 59 functioning as the support member. The extreme positions of the indexing may be determined by the limits 31. Figure 7a shows a situation where the drilling unit 12 is indexed in the operating centre 29 for drilling. When the drilling has been completed, the cracking unit 13 is indexed, as shown in Figure 7a, to the operating centre 29, whereby splitting or cracking is carried out by means of the cracking device 20. The indexing always takes place along a predetermined accurate path of movement.

[0032] It is also feasible to arrange the indexing to be controlled by a curved guide surface, in which case the drilling unit and the cracking unit move along a predetermined path of movement.

[0033] In some cases, features presented in this application may be used as such, irrespective of other features. On the other hand, features presented in this application may be combined to form different combinations.

[0034] The drawings and the related specification are only intended to illustrate the idea of the invention. Details of the invention may vary within the scope of the claims.

Claims

1. A method of generating cracking in rock material, the method comprising: operating a breaking device (4) arranged on a boom (2) of a work machine (1 ) and comprising a drilling unit (12) and a cracking unit (13); positioning the breaking device (4) at the point of a drill hole (30) to be drilled by means of the boom (2); drilling at least one drill hole (30) in the object (5, 53) of work with a rock drill machine (14) being a part of the rock drilling unit (12) and with a drill tool (18) connected to the rock drill machine; drawing the drill tool (18) out of the drill hole (30); moving the drilling unit (12) away from the point of the drill hole (3) and correspondingly moving the cracking unit (13) to the point of the drill hole (30); inserting a cracking tool (23) being a part of the cracking unit (13) into the drill hole (30) and causing cracks (36) to the object (5, 53) to be operated on; supporting at least one rock support (32) in the breaking device (4) against the object (5, 53) to be operated on and keeping a frame (24) of the breaking device (4) substantially immovable while the drilling unit (12) and the cracking unit (13) are being moved; and moving the drilling unit (12) and the cracking unit (13) by indexing them in the control of at least one support member (26, 59) along a predetermined path of movement (L, R); c h a r a c t e r i z e d by using a breaking device (4) in generating the cracking, which is an independent supplementary device detachably connected to the boom (2) of the work machine (1 ); and performing a work cycle relating to the drilling and cracking in the control of the breaking device's (4) own control unit (7) independently of the work machine.

2. A method according to claim ^ c h a r a c t e r i z e d by performing indexing along a linear path of movement (L), supported by at least one linear control surface (26).

3. A method according to claim ^ c h a r a c t e r i z e d by performing indexing along a curved path of movement (R), supported by a turning centre (59).

4. A method according to any one of the preceding claims, characterized by performing indexing against physical limits (31); performing drilling when the drilling unit (12) is indexed in a first direction of motion against one first physical limit (31), whereby the drilling unit

(12) is in an operating centre (29) determined by the centre line of the drill hole (30) to be drilled; and performing, after the drilling, indexing in a second direction of motion against at least one other physical limit (31), whereby the cracking unit

(13) becomes positioned in the operating centre (29).

5. A method according to any one of the preceding claims, characterized by using an excavator as the work machine; attaching, by means of a quick-fastening member, the breaking device (4) in place of the bucket of the excavator; and using the breaking device (4) as a temporary supplementary device of the excavator for breaking oversized blocks.

6. A method according to any one of the preceding claims, characterized by performing the steps according to the work cycle of the breaking device (4) automatically in accordance with a predesigned control strategy set in a control unit (7) of the breaking device.

7. Breaking device comprising: a drilling unit (12) comprising a rock drill machine (14) and a first feed beam (15); a cracking unit (13) comprising a cracking device (20) and a second feed beam (22) which is parallel to the first feed beam (15); a frame (24) on which the feed beams (15, 22) are supported; a fastening part (25) by means of which the frame (24) is attachable to the boom of a work machine; a first feed device (16) for moving the rock drill machine (14) on the first feed beam (15); a second feed device (21) for moving the cracking device (20) on the second feed beam (22); means for moving the drilling unit (12) and correspondingly the cracking unit (13) to an operating centre (29) determined by the centre line of the hole to be drilled; wherein the frame (24) comprises at least one support member (26, 59) in the control of which the drilling unit (12) and the cracking unit (13) are arranged to move while they are being indexed to the operating centre (29); and at least one indexing actuator (28, 58) for indexing, characterized in that the breaking device (4) is an independent supplementary device detachably connectable to the boom (2) of the work machine (1); and the breaking device (4) comprises at least one control unit (7) of its own, arranged to control the steps according to the work cycle of the breaking device (4) independently of the control system of the work machine.

8. A breaking device according to claim 7, characterized in that the support member comprises at least one linear control surface (26); and that the indexing actuator (28) is arranged to index the drilling unit (12) and the cracking unit (13) along a linear path of movement (L) determined by the linear control surface (26).

9. A breaking device according to claim 7, characterized in that the support member is a turning centre (59); and that the indexing actuator (58) is arranged to index the rock drilling unit (12) and the cracking unit (13) along a curved path of movement (R) determined by the turning centre (59).

10. A breaking device according to any one of preceding claims 7 to

9, characterized in that the cracking device (20) of the cracking unit (13) comprises an elongated cracking tool (23) insertable into a drill hole (30); and that the cracking device (20) comprises means for increasing the outer dimension of the cracking tool (23).

11. A breaking device according to any one of preceding claims 7 to

10, characterized in that the breaking device comprises a rock support (32) by means of which the frame (24) is supportable against an object (5, 53) to be operated on for the duration of the operation.

12. A breaking device according to any one of preceding claims 7 to 11, characterized in that the breaking device (4) comprises an independent dust collection system (42) of its own.

13. A breaking device according to any one of preceding claims 7 to

12, characterized in that the breaking device (4) comprises an independent flushing system (10) of its own.

14. A breaking device according to any one of preceding claims 7 to

13, characterized in that the rock drill machine (14) is arranged inside a noise dampening housing (49).

15. A breaking device according to any one of preceding claims 7 to

14, characterized in that the breaking device (4) comprises at least one quick-fastening member with which it is attachable to the boom of the work machine; and that there is at least one connecting member in connection with the quick-fastening member to connect the breaking device to an external energy source.

16. A breaking device according to any one of preceding claims 7 to

15, characterized in that at least one predetermined control strategy is set to the control unit (7) of the breaking device (4) for performing the drilling and cracking automatically.

17. A breaking device according to any one of preceding claims 7 to

16, characterized in that the breaking device (4) comprises a remote controller (60) which enables transmitting the operator's manual control commands to the control unit (7) of the breaking device.