FIELD OF THE INVENTION

The present invention relates to a device for cutting asphalt. It particularly relates to an asphalt cutting device which is to be connected to an excavator.

BACKGROUND OF THE INVENTION

Asphalt cutters are used when there is a need to dig in the ground below an asphalted surface, or when asphalt needs edge cutting for other reasons. There are different types of asphalt cutters used today, such as handheld cutters and cutters that are connected to an excavator. The present invention relates to the latter.

Asphalt cutters that are to be connected to excavators usually comprise a housing with a rotatable cutting disk. The frame is mounted on the stick of the excavator and the cutting disk rotates as the excavator or the stick of the excavator moves, due to the friction against the ground.

Many of the excavator asphalt cutters used today are completely static and lack power. The cutting efficiency depends on the weight of the excavator, and in order for the cutting to work the stick of the excavator, or the whole vehicle, has to be moved forwards and backwards. The cutting efficiency is therefore highly dependent on the weight of the excavator, making it difficult to use the state of the art asphalt cutters with lighter vehicles. In addition to this issue, it is also time consuming to cut asphalt using the static cutters of today.

As a remedy to this, JP2003328318 discloses an asphalt cutter to be connected to an excavator, having an external vibration generator which causes the device to vibrate. The device has two semi-circular cutting blades.

A drawback of this device is that using an external vibration generator, a significant part of the vibrations disappears to the chassis of the excavator, and other adjacent parts. This has to be compensated with more forceful vibrations, which not only results in that the excavator and its components are worn out faster, but such solutions are not particularly energy efficient. SUMMARY OF THE INVENTION

It is an object of the present invention to alleviate at least some of the mentioned drawbacks of the prior art and to provide an improved asphalt cutter that is to be connected to an excavator. This and other objects, which will become apparent in the following, are accomplished by a device as defined in the accompanying independent claim.

The term exemplary should in this application be understood as serving as an example, instance or illustration.

The present invention is at least partly based on the realisation that by oscillating the rotatable cutting disk, an improved cutting efficiency can be achieved. The oscillating movement, in combination with the rotation of the cutting disk induced by friction between the cutting disk and the asphalt to be cut, causes the asphalt to break. This results in a more time efficient way of cutting the asphalt, and the device is not as dependent on the weight of the excavator as the cutting devices of the state of the art are. This allows for using smaller machines in combination with the present invention.

The term oscillation should in the present context be understood as movement back and forth in a regular rhythm.

According to a first aspect of the present invention, a device for cutting asphalt is provided. The device is connectable to a construction vehicle such as an excavator, said device comprises a circular cutting disk having a central axis, about which axis said cutting disk is rotatable. Said device further comprises an actuator having an axis of rotation, said axis of rotation being parallel to the central axis of said circular cutting disk. The device also comprises an eccentric element extending at least partly through said circular cutting disk along the axis of rotation of the actuator, said eccentric element being rotatable about said axis of rotation independently of said circular cutting disk. The circular cutting disk is rotatable about said eccentric element. The actuator is connected to said eccentric element and arranged to rotate the eccentric element about said axis of rotation, wherein said rotation of the eccentric element causes the central axis of the cutting disk to be displaced, which causes to cutting disk to oscillate radially with respect to said axis of rotation.

By eccentric element is meant an element which is rotatable about an axis, having a centre of mass which is offset from said axis. According to an exemplary embodiment of the present invention, said eccentric element has an asymmetrical geometry in relation to said axis of rotation. According to another exemplary embodiment, said eccentric element has a symmetrical geometry but an asymmetrical mass distribution in relation to said axis of rotation.

The eccentric element being rotatable about said axis of rotation independently of said circular cutting disk should be interpreted as it is possible to rotate the eccentric element about the axis of rotation, without automatically rotating the circular cutting disk. At the same time, it is possible to rotate the circular cutting disk about its central axis, without rotating the eccentric element. This is defined in this application as independent rotatability. To achieve independent rotatability for the circular cutting disk and the eccentric element, a bearing element may be arranged concentrically about said eccentric element. Said circular cutting disk may then be arranged in connection with said bearing element. This enables that the eccentric element may be rotated by said actuator, about said axis of rotation, without necessarily causing said circular cutting disk to rotate about said central axis.

The actuator may be any type of actuator capable of rotating the eccentric element about the axis of rotation. According to an exemplary embodiment of the present invention, said actuator is a hydraulic motor or an electric motor. Other types of actuators are also conceivable. A hydraulic motor is advantageous since it allows for the device to be compact. Moreover, the axis of rotation may in some exemplary embodiments extend along a different direction than the output axis of the actuator, for example it may instead be perpendicular to the output axis of the actuator (by means of e.g. suitable gearing), depending on a specific application or situation. Stated differently, the eccentric element is rotated about the axis of rotation by means of the actuator either by direct coupling to the output axis of the actuator or via a suitable gearing assembly.

According to an exemplary embodiment of the present invention, at least one bearing unit is arranged about the eccentric element between the eccentric element and the cutting disk. This is advantageous since it makes it possible to rotate the circular cutting disk about its central axis without automatically rotating the eccentric element, and vice versa.

According to an exemplary embodiment of the present invention, said actuator is coupled directly to said eccentric element. This further enables having a compact device, where the rotations from the actuator are directly transferred to the eccentric element. This also minimises energy losses and wear on the device, compared to if an external oscillation generator would be used, which for example may be arranged to oscillate or vibrate the whole device or the whole stick of the excavator. Herby, the eccentric element has a direct effect on the cutting disk, instead of oscillating the whole device or the whole stick the device is attached to.

According to an exemplary embodiment of the present invention, the oscillation of the cutting disk has an amplitude of 1 - 5 mm, preferably 2 mm. This amplitude interval is advantageous since it enhances the cutting efficiency of the device. Also, a higher amplitude may subject the material in the device and/or the excavator to unnecessary stress.

By amplitude of the oscillation is meant the maximum deviation of the central axis of the cutting disk from the rotation axis of the actuator.

According to an exemplary embodiment of the present invention, the oscillation of the cutting disk has a frequency of 1000 - 2000 rpm, preferably 1300 - 1600 rpm, most preferably 1400 - 1550 rpm, such as e.g. 1475 rpm. This frequency interval further enhances the cutting efficiency of the device. It is desirable to have an oscillation frequency which is close to the resonance frequency of the material to be cut, since this may cause the material to oscillate and thus break more easily. In some embodiments, the oscillation frequency may be 80-120%, or 90-1 10% of the resonance frequency of the material to be cut. The components in asphalt typically have a resonance frequency around 1400 Hz, but other frequencies are also conceivable. It may be advantageous if the oscillation of the cutting disk has a slightly higher frequency than the resonance frequency of the asphalt, for example 1475 rpm.

By frequency is meant the number of oscillations per minute, or in other words how many times per minute the central axis of the cutting disk completes a full cycle of motion. According to an exemplary embodiment of the present invention, the frequency of the oscillation corresponds to the number of revolutions per minute for said actuator. In other words, the frequency of the oscillation may be determined by looking at the number of revolutions per minute for said actuator.

According to an exemplary embodiment of the present invention, said device further comprises a housing, said housing being connectable to a construction vehicle, such as an excavator. The housing may partially or fully enclose said actuator, said eccentric element and/or said circular cutting disk. According to an exemplary embodiment of the present invention, said housing at least partially encloses said actuator. According to another exemplary embodiment of the present invention, said housing is connectable to a stick of a construction vehicle, such as the stick of an excavator. The housing preferably comprises a portion being connectable to a quick coupler or quick hitch of an excavator. This portion may in some embodiments be described as an adapter, and it may be described as a part of the housing or as a separate part of the device. Having an adapter/portion of the housing being connectable to a quick coupler/hitch of an excavator allows for an operator to connect the device to the vehicle without having to leave the excavator cab. The connection may take less than 5 minutes to perform. These and other features and advantages of the present invention will in the following be further clarified with reference to embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing exemplary embodiments of the present invention.

Figure 1 shows a perspective view of a device according to an exemplary embodiment of the present invention.

Figure 2 shows a different perspective view of the same device as is illustrated in Figure 1 .

Figure 3 shows a side view of the same device as is illustrated in Figure 1 and Figure 2.

Figure 4 shows an exploded view of a device according to an exemplary embodiment of the present invention.

Figure 5 shows an end view of an exemplary embodiment of an eccentric element for use in a device according to the present invention. DETAILED DESCRIPTION OF EMBODIMENTS

In the following detailed description, some embodiments of the present invention will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present invention. Figure 1 shows a perspective view of a device 1 according to an exemplary embodiment of the present invention. The device 1 comprises a circular cutting disk 2 having a central axis 21 , an actuator (not shown) having an axis of rotation 41 , an eccentric element (not shown) arranged along the axis of rotation 41 , and a housing 3. The illustrated device also comprises an adapter 31 , making the device connectable to a quick coupler or quick hitch of an excavator.

The cutting disk 2 and the eccentric element are both rotatable, independently of each other. How this may be achieved is further described in relation to Figure 4. The actuator is connected to the eccentric element, and arranged to rotate the eccentric element about the axis of rotation 41 . The rotation of the eccentric element causes the cutting disk 2 to oscillate 10 radially to the axis of rotation 41 . By oscillation is meant that the central axis 21 of the circular cutting disk 2 moves in an oscillating movement in relation to said axis of rotation 41 .

The circular cutting disk 2 may be made of a metallic material, for example a suitable alloy such as steel. The housing may also be made of a metallic material, and more specifically of a suitable steel.

When the device 1 is connected to an excavator, it may be operated by placing the circular cutting disk 2 against the asphalt to be cut and moving the stick of the excavator, or the whole vehicle, forwards or backwards. The friction between the asphalt and the cutting disk 2, together with the

movement of the stick or the vehicle, causes the cutting disk to rotate about its central axis 21 . This rotation together with the oscillation caused by the rotation of the eccentric element causes the asphalt to break.

The oscillation 10 of the cutting disk 2 has an amplitude of 1 - 5 mm, preferably 2 mm, and a frequency of 1000 - 2000 rpm, preferably 1300 - 1600 rpm, most preferably 1400 - 1550 rpm. The frequency of the oscillation 10 may correspond to the number of revolutions per minute for the actuator.

As indicated in the figure, the oscillation 10 is at least in a direction which coincides with the normal of the asphalted surface to be cut. The oscillation may take place in more directions than the indicated one, but it is the oscillation in the indicated direction which enables an improved cutting efficiency.

Figure 2 shows a different perspective view of a device according to the same exemplary embodiment of the present invention as is shown in Figure 1 . In Figure 2, the actuator 4 is shown. The actuator 4 may suitably be a hydraulic actuator or motor, or an electric actuator or motor. The actuator 4 has an axis of rotation 41 , and is coupled directly to the eccentric element (not shown). This arrangement allows for the oscillations to have a direct impact on the circular cutting disk 2, resulting in less energy loss compared to if an external oscillation generator would be used. By external oscillation generator is meant any type of oscillation generator not arranged to directly impact the cutting disk, but to oscillate/vibrate the whole device, such as the vibration generator described in the prior art.

Figure 3 shows a side view of a device according to the same exemplary embodiment of the present invention as is shown in Figure 1 and Figure 2. Here it can be seen that said housing 3 at least partially encloses the actuator 4. The housing 3 also partially encloses the cutting disk 2 and the eccentric element (not shown).

Figure 4 shows an exploded view of a device according to an exemplary embodiment of the present invention. Here both the actuator 4 and the eccentric element 5 are shown. The eccentric element 5 may be made of a metallic material. For example, structural steel S355 may be used. In this exemplary embodiment, the device further comprises a bearing assembly 6. The bearing assembly may for example comprise four bearing elements 6a - 6d, arranged around the central axis 21 and/or axis of rotation 41 . At least one bearing element 6a may be arranged between the eccentric element 5 and the circular cutting disk 2, to enable independent rotation of the eccentric element 5 and the cutting disk 2. At least one bearing element 6b, 6c may be arranged about the eccentric element 5 to prevent transmission of the rotational movement of the eccentric element 5 to any other parts of the device. A bearing element 6d may also be arranged to prevent transmission of the rotational movement of the eccentric element 5 to a plate 8. The plate 8 is further described below.

The device may further comprise at least one washer 7 made of a suitable material, such as hard-plastic. In the illustrated exemplary

embodiment, the device comprises two such washers 7, arranged on either side of the cutting disk 2. The washers 7 serve the purpose of sealing the bearings in the bearing assembly 6, to prevent dust and dirt from entering the bearings.

The device illustrated in Figure 4 further comprises a plate 8 arranged about the central axis 21 , next to the actuator 4. On the plate, two rubber heels 81 are arranged. The purpose of the plate 8 is to absorb excessive torque created by the actuator 4 and the bearing assembly 6, to concentrate the actuator's force on rotating the eccentric element 5. The rubber heels 81 serve the purpose of absorbing the rotational movement created between the plate 8 and the housing 3, by sliding slightly against the edges of the housing. The rubber in the rubber heels 81 also limits the wear and the sound from the vibrations between the plate 8 and the housing 3.

Figure 5 shows a straight end view of an exemplary embodiment of an eccentric element 5 for use in a device according to the present invention. Here the axis of rotation 41 is shown in relation to the central axis 21 of the circular cutting disk 2. In this exemplary embodiment, the eccentric element 5 has an asymmetrical shape around the axis of rotation 41 , for achieving the eccentric effect. In other words, the eccentric element 5 may be rotationally symmetric about an axis of rotation of its own, but the axis of rotation 41 of the actuator 4 may be displaced in relation to the eccentric element 5. Stated differently, as illustrated in Fig. 4, the eccentric element 5 may have a receiving portion (to which the output axis of the actuator is coupled) that is offset in reference a "symmetric rotational axis" of the eccentric element.

In another possible exemplary embodiment, the eccentric element may have a symmetrical shape in the illustrated plane, but an unsymmetrical weight distribution. In other words, the centre of mass may be displaced from the axis of rotation. This causes a moment when the eccentric element is rotated, and the created moment will cause the cutting disk to oscillate. The moment may also cause the eccentric element and the actuator to oscillate. In order to prevent the oscillations from spreading to the excavator, suitably arranged force absorbing elements may be used.

The person skilled in the art realizes that the present invention by no means is limited to the embodiments described above. The features of the described embodiments may be combined in different ways, and many modifications and variations are possible within the scope of the appended claims. For example, ... In the claims, any reference signs placed between parentheses shall not be construed as limiting to the claim. The word

"comprising" does not exclude the presence of other elements or steps than those listed in the claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.