The present invention relates to a device for cutting a slit in a wall. In the construction or renovation of for instance a house and business premises it occurs that an opening must be made in a wall, in which for instance a window or a door can then be placed. A number of slits is made here in the relevant wall, after which the part of the wall enclosed by the slits is removed and the window or the door can be placed in the thus realized opening.

The device according to the invention comprises a handheld circular saw for cutting a slit, a guide rail which can be arranged on a wall for guiding the hand-held circular saw along the wall, and engaging means displaceable along the rail with which the hand-held circular saw can be placed into releasable engagement with the rail, wherein the handheld circular saw can be tilted in order to introduce the saw blade into the wall. The device makes it possible to attach the guide rail to the wall without the hand-held circular saw being placed into engagement therewith, to place the hand-held circular saw into engagement with the guide rail after arranging the guide rail on the wall, and to then introduce a saw blade arranged on the hand-held circular saw into the wall by means of tilting the hand-held circular saw and to cut a slit under guidance of the guide rail. This has the advantage that the required slits can be made in a wall in simple and safe manner using a hand-held circular saw in order to realize for instance an opening for a window or a door. Cutting slits in a wall using a

conventional hand-held circular saw, embodied with or without water cooling for the saw blade, has been found to be difficult and unsafe. The use of a hand-held circular saw for cutting a slit in a relatively soft and thin wall is regarded as being an inexpensive alternative to the use of large devices which are specially designed for relatively hard and thick walls and with which a saw blade can be mechanically introduced into a wall and displaced

therealong. Handling a hand-held circular saw when cutting a slit in a vertical surface is however difficult. Handling of the conventional hand-held circular saw is particularly difficult when cutting the part of a slit to be cut which lies above the shoulders of the user and when introducing the saw blade arranged on the conventional hand-held circular saw into the wall. This difficult handling can create unsafe situations, wherein the user or bystanders can be injured. With the device according to the invention the freedom of movement of the hand-held circular saw is limited after the guide rail, which can be handled in simple and safe manner, has been arranged on the wall and the

inoperative hand-held circular saw has been placed into engagement in simple and safe manner with the guide rail. Handling of the hand-held circular saw when introducing a saw blade arranged on the hand-held circular saw into the wall and when cutting the slit is hereby easier and safer than when cutting a slit in a wall using a separately held, non-guided, conventional hand-held circular saw. It is otherwise also possible with the device according to the invention to realize a slit in a floor. When making slits in a wall or a floor the processing of the wall or the floor with the saw blade is also referred to as a grinding process. As a result a hand-held circular saw as applied in the device according to the invention is also referred to as a hand-held grinder and the saw blade is also referred to as a grinding disc. When cutting or grinding slits in a wall or a floor use is generally made of a diamond saw blade or diamond grinding disc, wherein the hand-held circular saw is then also referred to as hand-held diamond saw or diamond grinder .

In a favourable embodiment of the device according to the invention the engaging means comprise a carriage displaceable along the rail and having an engaging shaft arranged thereon, and hooking means which are arranged on the hand-held circular saw and which can be placed into engagement with the engaging shaft. This measure makes it possible for the user to place the hand-held circular saw into engagement with the guide rail without taking both hands off the hand-held circular saw. This has the advantage that placing the hand-held circular saw into engagement with the guide rail is easier and safer. In a favourable

embodiment hereof the engaging means also comprise a locking for locking the hooking means once they are in engagement with the engaging shaft. This measure makes it possible to prevent undesirable release of the hand-held circular saw from the guide rail after the hand-held circular saw has been placed into engagement with the guide rail. This has the advantage that the device is safer.

In a further favourable embodiment of the device according to the invention, wherein the engaging means comprise a carriage displaceable along the rail and having an engaging shaft arranged thereon, and hooking means which are arranged on the hand-held circular saw and which can be placed into engagement with the engaging shaft, the handheld circular saw is tiltable around the axis of the engaging shaft. This measure enables a simple design of the device. This is because the engaging shaft and the hooking means serve for placing of the hand-held circular saw into engagement with the guide rail as well as for tilting of the hand-held circular saw relative to the guide rail. This has the advantage that the device is simple and reliable. In a favourable embodiment hereof the engaging shaft is connected rotatably to the displaceable carriage. This measure makes it possible to reduce a displacement of the surface of the hooking means which is in contact with the engaging shaft along the surface of the engaging shaft in contact with the hooking means. This has the advantage that wear of said surfaces can be reduced so that the decrease in the degree of engagement between the hooking means and the engaging shaft, and thereby the decrease in the limiting of movement of the hand-held circular saw relative to the guide rail, can be avoided.

A further favourable embodiment of the device according to the invention also comprises a tilting stop for limiting the tilting movement of the hand-held circular saw when it is in engagement with the rail. This measure makes it possible for instance to limit the tilting movement to the extent that the hand-held circular saw cannot be tilted so far that a saw blade arranged on the hand-held circular saw is directed toward the user. By limiting the tilting movement this measure also makes it possible to limit the maximum distance between the surface of the guide rail to be arranged against a wall and the rotation axis of a saw blade arranged on the hand-held circular saw, so that the user is for instance forced to first make a pre-slit with a saw blade with a relatively small radius and then complete the slit using a saw blade with a larger radius. This measure thereby has the advantage that the device is safer.

In a further favourable embodiment of the device according to the invention the hand-held circular saw is provided with a guard for covering a saw blade arranged on the hand-held circular saw, which guard is provided with a plastic grip. The measure makes it possible to increase the grip of the user on the guard during handling of the device. This has the advantage that the device is safer.

The present invention also relates to a kit comprising an above described device and at least a first saw blade and a second saw blade which can be arranged on the hand-held circular saw for rotation around a rotation axis, wherein the radius of the first saw blade is smaller than the radius of the second saw blade, wherein the tilting stop is designed such that, when the hand-held circular saw is in engagement with the guide rail, the distance between the surface of the guide rail to be arranged against a wall and the rotation axis is greater than the radius of the first saw blade and smaller than the radius of the second saw blade. By means of this kit the user thereof is forced to first make a pre-slit using the first saw blade with the relatively small radius and to then make the slit deeper using the second saw blade with the relatively larger radius. This kit enables simple and particularly safe cutting of a slit in for instance a wall or a floor.

The present invention also relates to an assembly for forming an above described device, comprising a guide rail which can be arranged on a wall for guiding a hand-held circular saw along the wall, and engaging means displaceable along the rail with which the hand-held circular saw can be placed into releasable engagement with the rail, wherein the hand-held circular saw can be tilted in order to introduce the saw blade into the wall. This assembly makes it possible to make a slit in for instance a wall or a floor in simple and safe manner.

The present invention will be further elucidated hereinbelow on the basis of an exemplary embodiment shown in the accompanying figures. This is a non-limitative exemplary embodiment . In the figures:

- figure 1 is a perspective view of an embodiment of the device according to the invention;

- figure 2 is a perspective view of the device of figure 1; - figure 3 is a side view of a detail of the device of figure 1;

- figure 4 is a perspective view of the device of figure 1 in a first situation of use;

- figure 5 is a perspective view of the device of figure 1 in a second situation of use.

Figure 1 shows a device 1 for cutting a slit in a wall. Device 1 is shown with a hand-held circular saw 2 which is in engagement with a guide rail 3. Guide rail 3 is provided with fixing holes 4 through which fixing bolts 5 are placed with which guide rail 3 can be arranged on a wall in which a slit must be made. Further shown is that hand-held circular saw 2 is in engagement with guide rail 3 via a carriage 6 which is displaceable along guide rail 3 in the direction of arrows A. Hand-held circular saw 2 is thus displaceable along the guide rail in the direction of arrows A. In addition, hand-held circular saw 2 can be tilted relative to guide rail 3 in the direction of arrow B in order to bring saw blade 7, which is operatively connected to hand-held circular saw 2, into contact with the wall in which a slit must be made. The manner in which hand-held circular saw 2 is in engagement with guide rail 3 in the device as shown in figure 1 is shown in detail in figures 2 and 3.

Figure 2 shows device 1 of figure 1, wherein hand-held circular saw 2 is not in engagement with guide rail 3. Guide rail 3 is provided with fixing holes 4 through which are placed fixing bolts 5 with which guide rail 3 is arranged on a wall 8 in which slits must be made. The slits to be made are shown by means of broken lines 9. After making the slits indicated by means of broken lines 9 the part 8a of wall 8 enclosed by the slits can be removed so that an opening is created in which a door can for instance be arranged.

Further shown is that hand-held circular saw 2 is provided with a hook member 10 which, by displacing hand-held circular saw 2 in the direction of arrow C, can be placed into engagement with an engaging shaft 11 arranged on the carriage 6 displaceable along guide rail 3. Hooking member 8 and carriage 6 with engaging shaft 11 thereon together form the engaging means with which hand-held circular saw 2 can be placed into engagement with guide rail 3.

Figure 3 shows a side view in detail of a part of device 1 of figure 1. Hand-held circular saw 2 is shown with a chassis 12 having a motor 13 therein with which a saw blade 7 connected operatively to hand-held circular saw 2 can be driven. The chassis is also provided with a handle 14 by which the user can grip hand-held circular saw 2 with a hand, with a connection 15 for the supply of cooling liquid, and with a guard 16 for covering the saw blade 7 operatively connected to hand-held circular saw 2. Guard 16 is provided with a plastic grip 17.

In figure 3 hand-held circular saw 2 is in engagement with a guide rail 3, this guide rail 3 being arranged against a wall 8 by means of fixing bolts 5. Hand-held circular saw 2 is in engagement with guide rail 3 by means of engaging means in the form of carriage 6 displaceable along rail 3 and having engaging shaft 11 arranged thereon, and hook member 10 arranged on hand-held circular saw 2. In figure 3 carriage 6 is shown partially cut-away so as to show that hook member 10 is in engagement with engaging shaft 11. Also shown is that hook member 10 is provided with a locking in the form of locking bolt 16. Figure 3 shows that locking bolt 16 is provided at one end with a rotatable grip 16a and at the other end with a tip 16b, which tip 16b is in contact with engaging shaft 11. As a result the handheld circular saw 2 cannot be displaced in the direction of arrow D relative to guide rail 3 and cannot therefore be released from engaging shaft 11. By rotating the rotatable grip 16a the tip 16b of locking bolt 16 can be displaced away from engaging shaft 11, so that hand-held circular saw 2 can be released from engaging shaft 11, and thereby from the guide rail, in the direction of arrow D. The situation is then realized as shown in figure 2. From the situation shown in figure 2 the hand-held circular saw 2 can then be displaced once again in the direction of arrow C for replacing thereof into releasable engagement with guide rail 3.

Figure 3 also shows that hand-held circular saw 2 is tiltable around the axis 11a of engaging shaft 11 so that hand-held circular saw 2 can be tilted in the direction of arrow B from the position shown in figure 3. Saw blade 7 is here then brought into contact with wall 8. Not shown is that engaging shaft 11 is rotatably connected to

displaceable carriage 6, for instance by means of roller bearings incorporated in carriage 6.

Figure 3 also shows that device 1 has a tilting stop in the form of a protruding leg 18 of hook member 10. In the situation shown in figure 3 this protruding leg 18 is in contact with carriage 6 so that the tilting movement of hand-held circular saw 2 is limited to the extent that handheld circular saw 2 can tilt no further in the direction of arrow E. The maximum distance F is also determined by means of this protruding leg 18. This distance F is the distance between the surface 3a of guide rail 3 arranged against wall 8 and a line 19 which intersects the rotation axis about which saw blade 7 can be rotated by means of motor 13, and which runs parallel to surface 3a of guide rail 3 arranged against wall 8 when hand-held circular saw 2 is in

engagement with guide rail 3. Because the radius of saw blade 7 shown in figure 3 is smaller than the maximum distance F, in the shown situation saw blade 7 is not in contact with wall 8. If the radius of saw blade 7 were larger than the maximum distance F, the hand-held circular saw with saw blade 7 arranged thereon could not then be placed into engagement with guide rail 3. If the user nevertheless wishes to use a saw blade 7 with a radius larger than the maximum distance F, the user must first make a pre-slit using a saw blade 7 with a radius smaller than the maximum distance F. The user can then use a saw blade 7 with a radius larger than the maximum distance F. When hand- held circular saw 2 is being placed into engagement with guide rail, saw blade 7 with the larger radius can then be placed partially into the already pre-cut slit 3 so that hand-held circular saw 2 can indeed be placed into

engagement with guide rail 3. This method of operation is shown schematically in figure 4 and figure 5. Figure 4 shows that a pre-slit 20 is made in wall 8 using a saw blade 7 with a radius Rl which is smaller than the maximum distance F. In order to make this pre-slit the hand-held circular saw 2 is tilted in the direction of arrow B relative to guide rail 3 so that saw blade 7 is introduced into wall 8, and hand-held circular saw 2 is then displaced in the direction of arrow G along guide rail 3 so that pre-slit 20 is made. By displacing hand-held circular saw 2 further in the direction of arrow G from the shown situation, pre-slit 20 is made further along the broken line 9. Figure 5 shows that a saw blade 7 with a radius R2 greater than the maximum distance F is placed in pre-slit 20, is tilted in the direction of arrow B relative to guide rail 3, and hand-held circular saw 2 is then moved in the direction of arrow G so that a part of pre-slit 20 is made into a complete slit 21. By displacing hand-held circular saw 2 further in the direction of arrow G from the shown situation the further part of pre-slit 20 is made into a full slit.