The present invention relates to a micro trench sawing device and a method for sawing a micro trench. Such a micro trench is generally used for laying of a cable, a duct or a duct tube in such a micro trench, and the present device and method therefore also relates to such laying.

Micro trenching is a known way of laying cables or ducts into the ground, in particular below a paved surface, such as along a street. Using micro trenching, rather than removing a wide strip of the paved surface; digging a wide trench, laying the cable or duct at the bottom of the trench; refilling the trench; and repaving the resulting surface, only a very narrow trench is instead sawn, using a saw blade, and the cable or duct is placed into the trench while it is being sawn. When the trench is complete, only a small volume of refilling material is required, and the top part can be sealed using a suitable sealant, such as a flexible mastic, to restore the surface to its original quality.

It is known, in the art of such micro trenching, to use a combined stabilization device and guide means being arranged behind the saw blade, and during use guiding the cable or duct down into the trench while also preventing the trench walls from collapsing before the cable or duct has come to rest at the bottom of the trench.

Such micro trenching has turned out to be very cost-efficient and fast, as compared to making a wider trench, for laying of cables and ducts, and in particular for laying of fibre cable ducts in residential areas. In the latter case, a main micro trench is sawn along a street, and shorter access micro trenches are branched off to each of the properties to connect to the fibre network. Such access trenches generally run at an angle to the main trench, such as perpendicularly to the main trench, such as with at least one component in a cross direction of a street along which the micro trenching operation is performed.

Such a micro trenching device is previously known from Swedish patent with publication number SE 537 130. However, it has turned out that it is not as easy to achieve high working efficiency when laying such access trenches, as compared to the main trench. The reason for this is that access trenches are sawn perpendicularly to the main direction of the street. Since the saw blade and the stabilization device are quite bulky, it is typically not possible to lay the cable or duct along the entire necessary access trench length, from the intersection with the main trench and up to each property to be connected. Instead, access trenches are often sawn using a separate, smaller saw, without a stabilizing device of the above described type. Thereafter, the cable or duct is placed in the sawn access trench manually afterwards. This procedure takes considerably more time per trench meter than for the main trench. Also, two different types of machines are required, which is expensive.

The present invention solves the above described problems. Hence, the invention relates to a micro trench sawing device comprising a supporting frame; a saw blade holding means, arranged to hold a saw blade so that the saw blade is horizontally adjustable within a vertical adjustment plane, between a forward and a backward position; a saw blade driving means, arranged to drive the said saw blade held by the saw blade holding means for sawing a micro trench in the ground; a main motor, fixedly mounted in said frame and arranged to drive the saw blade driving means; and wheels, defining the corners of a polygon on said ground; which sawing device s characterised in that the vertical adjustment plane intersects the said polygon, and in that the vertical adjustment plane does not intersect the main motor. Furthermore, the invention relates to a method for sawing a micro trench using a micro trench sawing device, which micro trench sawing device comprises a supporting frame; a saw blade holding means, arranged to hold a saw blade so that the saw blade is horizontally adjustable within a vertical adjustment plane, between a forward and a backward position; a saw blade driving means, arranged to drive the said saw blade eld by the saw blade holding means for sawing a micro trench in the ground; a main motor, fixedly mounted in said frame and arranged to drive the saw blade driving means; and wheels, defining the corners of a polygon on said ground; which method is characterised in that the vertical adjustment plane intersects the said polygon, in that the vertical adjustment plane does not intersect the main motor, in that the method comprises a step in which the micro trench sawing device is driven in a forwards direction while driving the saw blade for sawing said trench and while holding the saw blade fixed in relation to the supporting frame, and in that the method also comprises a step in which the micro trench sawing device is held still while the saw blade is brought forward for sawing the said trench.

In the following, the invention will be described in detail, with reference to exemplifying embodiments of the invention and to the enclosed drawings, wherein:

Figure 1 is a perspective view of a micro trench sawing device according to the invention; Figure 2 is a side view of the device illustrated in Figure 1;

Figure 3 is a front view of the device illustrated in Figure 1;

Figure 4 is a top view of the device illustrated in Figure 1;

Figure 5 is a simplified side view of a device according to the invention;

Figure 6 is a top view of a street showing micro trenches; and

Figure 7 is a flow chart illustrating a method according to the invention. All Figures share the same reference numerals for same or corresponding parts.

Hence, Figure 1 illustrates a micro trench sawing device 100 comprising a supporting frame 110. The frame 110 is preferably open, in the sense that it preferably does not comprise covering side walls covering more than 50% of the sides of the device 100. In particular, the frame 110 is sufficiently open so as to admit direct access to the main functionality of the device 100 without having to open side wall doors or the like, with the possible exception of the openable tanks as described below. Preferably, the supporting frame 110 is manufactured from hollow metal tubes. The device 100 is associated with a forwards direction F, an upwards direction U and a cross direction C. In general, the device 100 is moved in the forwards direction F during non-sliding sawing of a main 21 or access 22 micro trenches, and the device 100 is moved in the cross direction C when being moved between parallel trenches, such as consecutive access trenches 22. Please see Figure 6.

The device 100 comprises a saw blade holding means 120, arranged to hold a saw blade 121 used to saw the micro trench into the ground 10, preferably in a street 11. The saw blade 121 is preferably a circular saw blade which preferably is at least 60 cm in diameter, more preferably between 80 and 120 cm in diameter, preferably a standard 100 cm diameter saw blade.

Moreover, the saw blade 121 is preferably a diamond saw blade, in other words comprises diamond elements on the wear surface arranged for the cutting action. The saw blade 121 is preferably operated in an up-cut fashion, rotating counter-clockwise as viewed in Figure 2 and when the device 100 and/or the saw blade 121 moves and/or slides in a forward direction F during cutting.

Preferably, the ground 10 comprises a top surface, which is preferably paved, such as an asphalt or concrete surface, as well as a lower layer, which is preferably a granular material such as gravel. The top surface is preferably between 1-10 cm thick, and the total depth of the sawn trench is preferably 20-50 cm. Furthermore, the trench is preferably at least 1 cm wide, preferably at least 2 cm wide, preferably at least 3 cm wide. Also, the trench is preferably at the most 6 cm wide, preferably at the most 5 cm wide, most preferably at the most 4 cm wide. Typically, the ground 10 may be a paved residential street.

The saw blade 121 is horizontally adjustable, preferably continuously adjustable, within a vertical adjustment plane AP (see Figures 3 and 4), between a forward (125) and a backward (126) position. This is best seen in Figure 5. In other words, the saw blade 121 is slidable in a forwards/backwards F direction in relation to the supporting frame 110 and the device 100 as a whole. Moreover, according to the invention the device 100 comprises a saw blade 121 driving means 130, arranged to drive the saw blade 121 held by the saw blade holding means 120 for sawing the micro trench in the ground 10. Since the saw blade 121 is preferably a rotary saw blade, the saw blade driving means 130 is preferably a rotary drive, causing the saw blade 121 to rotate about a saw blade axis.

The vertical adjustment plane AP lies within the saw blade 121 itself, and is parallel to a main plane of the saw blade 121.

It is realized that several saw blades 121 can be used in parallel, such as arranged on the same saw blade axis one adjacent the other. In this case, the vertical adjustment plane AP lies within the set of saw blades in question. Also, the device 100 comprises a main motor 140, which is fixedly mounted in and in relation to the frame 110, and furthermore arranged to drive the saw blade driving means 130. Hence, the main motor 140 is arranged to provide power to the saw blade driving means 130, such as via an electric or hydraulic power transfer system, such as described below. Preferably, the main motor 140 is also arranged to provide power for propulsion of the de- vice 100 as such, across the ground 10, via driven wheels 151, 152, 153 and/or 154. Furthermore, the main motor 140 is preferably also arranged to provide the device 100 with power for additional functions, such as lowering/raising the saw blade 121 and/or bringing the saw blade 121 forward/backward, and corresponding for a saw blade 121 cover 122. Additionally according to the invention, the device 100 comprises said wheels 151, 152, 153, 154, defining the corners of a polygon 155 on said ground (see Figure 1). Preferably, and as shown in the Figures, there are four wheels 151-154, such as a back pair 151, 152 sharing the same axis of rotation and a front pair 153, 154 also sharing another axis of rotation. Even though three wheeled devices 100 according to the present invention are foreseen, it is preferred that there are at least four wheels, and in particular an even number of wheels forming pairs with common rotation axes, since this provides a stable construction for a slidable saw blade 121 arrangement of the type described herein.

According to the invention, the said vertical adjustment plane AP intersects the said polygon 155. Furthermore, the vertical adjustment plane AP does not intersect the main motor 140. In other words, as the saw blade 121 moves backwards and forwards between the extreme horizontal positions 125, 126, it does so in a way so that a main plane of the saw blade 121 intersects the part of the surface beneath the device 100 which is limited by the polygon 155 rendered by the wheels 151-154. However, the said main plane of the saw blade 121 does not cross the main motor 140, but extends upwards, forwards and backwards beside the main motor 140. This is illustrated in the Figures.

Hence, the adjustable saw blade 121 is not arranged vertically beneath the main motor 140, but rather to the side of the main motor 140 (even though the saw blade 121 as such may be located at a lower height than the main motor 140, it would not bump into the main motor 140 should it be raised sufficiently). In contrast to the present invention, a solution in which a main motor 140 is arranged above the saw blade 121 does not provide the advantages described herein, in particular in that it does not offer the combination of a well- balanced and compact design for sawing micro trenches of the above described type.

Namely, such a geometry, in which the saw blade 121 is arranged within the wheel base, preferably within the supporting frame 110, but not vertically beneath the main motor 140, provides a very stable and compact, yet flexible device 100 for sawing micro trenches. The saw blade 121 can be arranged so that the vertical adjustment plane AP is relatively close to the geometric centre GC of a pair of wheels 153, 154 that drive the device 100 (see, for instance, Figures 3 and 4). This will cause the saw blade 121 to run straight in the sawn trench during sawing, minimizing unwanted problems with sideways turning and saw blade 121 wear. Furthermore the vertical adjustment plane AP can be arranged to be relatively close to the mass centre MC of the device 100, which prevents the saw blade 121 from tilting in the sawn trench, also minimizing unwanted saw blade 121 wear (see, again, Figures 3 and 4). At the same time, a compact design with desired low mass centre MC can easily be achieved, for inexpensive production and attractive road properties. These aspects will be elaborated on, and exemplified, in the following.

In addition to the said slidability, it is also preferred that the saw blade 121 holding means 120 is further arranged to hold the saw blade 121 so that the saw blade 121 is vertically adjustable, preferably continuously adjustable, in the same vertical adjustment plane AP, between a raised 127 and a lowered 128 position (see Figure 5). In the lowered position 128, the saw blade 121 is completely lowered into the ground 10 for sawing the trench, preferably for sawing a trench of the above indicated depth; in the raised position 127 at least part of the saw blade 121 is raised completely above ground 10. It is then preferred that, in the raised position 127, at least part of the saw blade 121 is positioned horizontally beside the main motor 140. In other words, were it not for the orientation and position of the vertical adjustment plane AP, the saw blade 121 would bump into the main motor 140 during raising to the raised position 127.

Moreover, it is preferred that the saw blade 121 holding means 120 comprises a saw blade 121 cover 122, for protecting the saw blade 121 and the user 200 during use. Preferably, the saw blade 121 cover 122 is vertically adjustable independently of the saw blade 121. Hence, for example the cover 122 may be raised from a position where it covers a fully lowered saw blade 121 to a higher position without the saw blade 121 being raised as a result, for instance for inspection.

In particular, it is preferred that the saw blade 121 cover 122 is arranged to be supported on the ground by at least one wheel 123, which wheel 123 is then preferably arranged so that a perpendicular projection of the wheel 123 on the main plane of the saw blade 121 falls completely within the saw blade 121 itself. In other words, the wheel 123 is, in its entirety, disposed on the side of the cover 122, rather than sticking out from the cover 122 in the forwards or backwards directions beyond the extension limits of the saw blade 121. There may be more than one such supporting wheel 123, in that case preferably none of which sticking out in said manner. It is noted that the wheel 123 illustrated in the Figures is not arranged accordingly, since it protrudes forwards in relation to the cover 122. Such a support wheel provides for stable operation, while allowing the saw blade 121 to reach a maximum distance forwards and backwards when sliding during sawing operation. This is useful when, for instance, sawing across a street 11 as described below, and when reaching a pavement, property limit or other obstacle that the access trench 22 should come as close as possible to.

The sliding of the saw blade 121 may preferably be performed using a chain drive, as illustrated in the Figures, but it is also possible to use, for instance, a belt or cog drive. The saw blade 121 holding means 120 preferably comprises two vertically distanced, such as at least 50 cm apart, fastening points between the movable parts of the holding means 120 and fixed parts of the holding means 120. Preferably, these separated fastening points are arranged along two horizontal beams along which the movable saw blade 121 holding means 120 parts are arranged to slide. It is preferred that the supporting frame 110 generally defines a volume containing the saw blade 121 holding means 120, the saw blade 121 driving means 130 and the main motor 140, providing a very compact design.

According to one embodiment, the main motor 140 is an electric motor. However, accord- ing to an alternative embodiment, the main motor 140 is an explosion motor, such as a diesel, gasoline or methane gas engine. In the latter case, it is preferred that a fuel tank 141 for the main motor 140, such as a tank 141 for diesel, gasoline or compressed methane gas, is arranged on an opposite side of the said vertical adjustment plane AP in relation to the main motor 140. Correspondingly, in case the main motor 140 an electric motor, and in case the device 100 comprises a battery, it is preferred that the battery is arranged in a corresponding position as said tank 141. This provides an advantageous layout of the components of the device 100 while still allowing the saw blade 121 from being raised and lowered without being hindered by the main motor 140, which is a relatively heavy component. Furthermore, it is preferred that the saw blade 121 driving means 131 comprises a hydraulic motor 131, and in that a hydraulic fluid tank 132 for the hydraulic motor 131 is then arranged on an opposite side of said vertical adjustment plane AP in relation to the main motor 140, hence on the same side, and preferably in front of, back of, on top of or below, the said fuel tank 141 or battery. It is specifically preferred that the main motor 140 is arranged to provide a hydraulic pressure, which in turn is exploited by said hydraulic motor 131 to rotate the saw blade 121. An arrangement with the hydraulic fluid tank 132 in this way provides similar advantages as the said positioning of the fuel tank 141 or battery. Hence, the saw blade 121 may preferably be raised to the raised position 127 between the main motor 140 and the said tanks 141, 132.

In particular, in case there is both a fuel tank or batter 141 and an hydraulic fluid tank 132, it is preferred that they are arranged beside each other, generally on the same height, as illustrated in Figure 1. In this case, they are preferably pivotally arranged, and able to open sideways, in the cross or opposite cross direction C, in a way similarly to a pair of double doors (illustrated using broken arrows in Figure 1). This provides a device layout 100 with the above described advantages in terms of general geometry and weight balance, and also provides a way to both being able to refuel/refill the tanks 141, 132 and to gain easy access to the device 100 components arranged at the centre of the device 100, behind the opena- ble tanks 141, 132. For instance, the tanks 141, 132 may be locked in their closed position, and released for opening using a quick-release mechanism of conventional type. Figure 2 does not show the tanks 141, 132, but they are more clearly shown in Figure 1. It is further realized that the hydraulic motor 131 can instead be an electric motor, for driving the saw blade 121.

According to a very preferred embodiment, the saw blade 121 driving means 130 is arranged to be fixedly arranged in relation to said saw blade holding means 120, and hence also to the saw blade 121 rotation axis. In other words, the saw blade 121 driving means 130 is preferably movable both in relation to the supporting frame 110 and the main motor 140, and moves continuously with the saw blade 121 during raising/lowering and forwards/backwards movements. In particular, this allows the use of a direct axial power transmission between the driving means 130 and the saw blade 121. This is preferred since it minimized force transfer losses, in particular when using a hydraulic motor 131 supplied with power from the main motor 140 using a hydraulic power transfer. Also, it is important to note that the principles described herein, regarding the orientation and positioning of the vertical adjustment plane AP, allow such a movable saw blade 121 driving means 130 arrangement without compromising the advantages provided by said principles. In particular, it is for this reason further preferred that the saw blade 121 driving means 130 is arranged on the same side of the said vertical adjustment plane AP as the main motor 140, in other words on the opposite side as compared to the said tanks 141, 132. Beneath the main motor 140, there is typically space for the moving driving means 130 to manoeuvre, while still maintaining an acceptable overall weight balance.

It is noted that it is in general not preferred that the saw blade 121 can be moved outside of the vertical adjustment plane AP, in other words in a direction perpendicular to said plane AP - the saw blade 121, and the driving means 130, is hence only movable in the upwards/downwards U and the forwards/backwards F directions.

The saw blade 121 slidability function is preferably arranged so that, when the saw blade 121 is positioned in at least one of said forwards 125 and backwards 126 positions, preferably both, a vertical projection of the saw blade 121 on the above described polygon 155 on the ground 10 at least partly falls outside of the polygon 155 in question. In other words, the slidability is arranged so as to allow the saw blade 121 to saw the micro trench even outside of the wheel base of the device 100 in at least one, preferably both, of the forwards/backwards F directions.

As discussed above and illustrated in Figures 3 and 4, the present invention allows for an arrangement of the vertical adjustment plane AP relatively close to said geometric centre GC and said mass centre MC. In particular, it is preferred that the vertical adjustment plane AP is at the most 50 cm from the centre of gravity MC of the micro trench sawing device 100 as a whole, when any fuel 141 or hydraulic 132 tanks are completely filled. In other words, the distance 112, perpendicularly to the vertical adjustment plane AP, between said plane AP and said centre of gravity MC, is preferably at the most 50 cm. Similarly, it is pre- ferred that the closest distance 111 between the vertical adjustment plane AP and the geometric midpoint GC between a pair 153, 154 of said wheels that are driven is 50 cm or less. When there are several driven wheel pairs 151, 152; 153, 154, it is preferred that the vertical adjustment plane AP is at the most 50 cm from each of the respective geometric midpoint between each of such driven wheel pairs. The present inventors have discovered that such arrangement of the vertical adjustment plane AP provides adequate device 100 performance when sawing micro trenches under most commercially important conditions. In particular, this is the case when sawing micro trenches of the type specified above.

Moreover, it is preferred that the vertical adjustment plane AP is arranged between 0% and 25% of the distance from said geometric midpoint GC, in a direction perpendicular to the main plane of the held saw blade 121 and away from the main motor 140, between said pair of driven wheels 153, 154.

Regarding the said wheels 151, 152, 153, 154, it is preferred that that at least four pairwise arranged wheels, preferably all of the device's 100 wheels, are steerable, and that the device 100 further comprises a control means (not shown in the Figures) for steering said wheels 151, 152, 153, 154 across a respective vertical steering axis. It is preferred that the control means is a digital control means, arranged to continuously measure wheel 151-154 steering positions, device 100 velocity, strain and resistance on the saw blade 121 and so forth, so as to be able to offer computer-guided steering for a user 200 with a remote control 170 for operating the device 100 during sawing and manoeuvring operation. The remote control 170 preferably sends control signals to the control device, in turn controlling the device 100 functions. In particular, it is preferred that the control device is arranged to implement predefined manoeuvring programs, such as to turn the device 100 90° for switching sawing direction from main trench 21 to access trench 22 or vice versa; and lateral (in the cross direction C) moving without turning the device 100, for switching from sawing one access trench 22 to a subsequent, adjacent access trench 22 (see Figure 6 and below).

In particular, it is preferred that, when the wheels 151-154 are driven so that the device 100 moves forwards or backwards, the control device is arranged to allow only one pair 151, 152 or 153, 154 of wheels to be steered, the other pair being held still and preferably straight. This is particularly the case when the saw blade 121 has been lowered to a position below the ground 10 level or even when sawing. Furthermore, the device 100 is furthermore arranged with a cable, tube or duct laying means, arranged to lay said cable, tube or duct in the sawn trench. Such a laying means may be conventional as such, for instance of the type described in Swedish patent SE 537 130, referenced above. Figure 7 illustrates a method according to the invention, using a micro trench sawing device 100 of the type described herein for sawing a micro trench or a system of micro trenches 21, 22 as exemplified in Figure 6.

Preferably, the method starts with a couple of initial steps, comprising establishing the de- vice 100 at the site of micro trench sawing; positioning the device 100 directly above the trench to be sawn; starting the saw blade 121 rotation with the saw blade 121 in a raised position above the ground 10 level; and lowering the saw blade 121 to a lowered position at least partly below ground 10 level while rotating. Thereafter, the method comprises a step in which the device 100 is driven in the forwards direction F while driving the saw blade 121 for sawing the trench and holding the saw blade 121 fixed in relation to the supporting frame 110. For an access trench 22, as shown in figure 6, this step is preferably performed until the device 100 abuts or almost abuts the far limit of the access trench 22. Thereafter, the method comprises a step in which the device 100 is held still, in other words the wheels 151-154 don't move on the ground 10, while the saw blade 10 is brought forward F, using the above described sliding action, for sawing the said trench. In case of an access trench 22, this preferably finalizes the access trench 22 up to said far end.

Further preferably, for an access trench, a sliding action in the opposite, backward, direction is preferably included before said movement of the device 100 is commenced, so as to finalize the access trench 22 up to a near end, opposite to the said far end, of said access trench 22. This way, only one sawing step is required for sawing the whole access trench 22, since the saw blade 121 is never brought upwards, out from the trench 22, before the complete access trench 22 is sawn, but moves all the time in a lowered position.

In general, it is preferred that the micro trench 22 is an access trench 22, sawn across the width of a street as illustrated in Figure 6, from a main micro trench 21 to a property. Such access trenches 22 may be sawn perpendicularly to a main trench 21, or at an angle thereto. The present machine 100 is equally suitable for all such sawing strategies.

Preferably, the method according to the invention also comprises actually sawing said main micro trench 21, using the same device 100 but then operated in a direction which may be about 90° from the direction when sawing the access trenches 22.

When the wheels 151-154 are driven to move the device 100 in the forwards direction F while sawing the said micro trench 21 or 22, it is preferred that only one pair 153, 154 of front wheels (that is, a front wheel pair 153, 154 arranged furthest in the forward direction F on the device 100) are steered, while the remaining wheels, the back wheels 151, 152, are held fixed, preferably straight. Then, the saw blade 121 is adjusted, in other words slid as described above, so that the saw blade 121 rotation axis lies in the same vertical plane as a common wheel axis of a pair of non-steered back wheels 151, 152. It is understood that the said same vertical plane is perpendicular to the vertical adjustment plane AP. In other words, the saw blade 121 is slid, such as backwards, until it reaches a position in which the saw blade 121 rotation axis is aligned, in the horizontal direction, with the back wheel 151, 152 axes. Then, it is preferred that only the steered wheels 153, 154 (the front wheels) are driven, and that the back wheels 151, 152 are only rolling along passively. This provides minimum wear on the saw blade 121 during sawing operation. It is noted that it is preferably said control means that controls what wheels 151-154 are driven and steered at any one given moment, preferably using a set of predefined operation patterns. It is further realized that the corresponding control program can be implemented for sawing in the backwards directions, whereupon the back wheels 151, 152 are steered and driven, while the saw blade 121 is moved horizontally to align with the front wheels 153, 154 axis, which front wheels 153, 154 then passively follow the back wheels 151, 152.

It is preferred that the wheels 151, 152, 153, 154 are arranged with individual suspension, such as using a spring suspension, possibly in combination with a pneumatic suspension; or by the wheels themselves being resilient, such as being air-filled or manufactured from a rubber material allowing a suspension effect. Such suspension is advantageous for absorbing bumps and the like in the ground 10, in particular in a device 100 of the present type, in which the wheel pairs 151, 152; 153, 154 are arranged relatively far from each other. It is in general preferred that the respective wheels of each wheel pair 151, 152; 153, 154 are arranged at least 100 cm, more preferably at least 150 cm, from each other.

Above, preferred embodiments have been described. However, it is apparent to the skilled person that many modifications can be made to the disclosed embodiments without departing from the basic idea of the invention.

For instance, the device 100 may look visually different from the device 100 illustrated in Figures 14 while still following the design principles described herein for achieving a stable, compact and well-balanced device 100.

The control device may have many additional functions. For instance, a four-wheel steering may be automatically inactivated when the saw blade 121 moves down to a position in which it risks coming into contact with the ground 10. The control device may further automatically disable the sliding function when the device 100 moves by the wheels being driven in any direction. This is preferably made by a button, such as a dead man's grip button, which the user 200 must press in order for the device 100 to move, which button then also inactivates the sliding functionality.

In general, all that has been said above in relation to the method according to the present invention is equally applicable to the described device according to the invention, and vice versa.

Hence, the invention is not limited to the described embodiments, but can be varied within the scope of the enclosed claims.