EP2560798A1

EP2560798A1 - Blade for cutting a piece of plasterboard, method for implementing said blade, and use thereof

Info

Publication number: EP2560798A1
Application number: EP11721117A
Authority: EP
Inventors: Benoît MALLET
Original assignee: Individual
Current assignee: Jbme Innovations
Priority date: 2010-04-21
Filing date: 2011-04-18
Publication date: 2013-02-27
Also published as: FR2959157B1; US20130126575A1; FR2959157A1; WO2011132134A1

Abstract

The invention relates to a solution for rapidly grooving a piece of plasterboard, enabling the creation of a plane cutting edge and a precise cut-out of the layer(s) of paper or cardboard. To this end, according to the invention, the cutting is carried out in three main steps by means of a blade having a particular shape and sharpness: a step of grooving, a step of breaking the plasterboard, and a step of levelling the cutting edge. The invention therefore relates to a blade (300) for cutting a piece of plasterboard, characterised in that it comprises at least one grooving corner (301) having a plane face and a bevelled face.

Description

CUTTING BLADE OF A CARTON-PLASTER PANEL. PROCESS

OF IMPLEMENTATION AND USE.

The invention relates to a cutting blade of a gypsum board, a method of implementation and use of the blade.

A board of plasterboard is a panel made of a layer of plaster covered, on at least one side, by a sheet of cardboard or paper. Generally, both sides of the panel are covered by a sheet of cardboard or paper.

Plasterboards are usually manufactured in the factory, and are used to make partitions, ceilings, etc. These panels therefore replace the use of powdered plaster diluted in water for coating walls, which is a tiring operation, long and requires significant expertise to obtain an optimal composition of the plaster and satisfactory flatness of the coated surface.

These panels have the advantage of being easy to handle and allow a quick job. In addition, the know-how necessary for their positioning is reduced compared to traditional plaster. Finally, manufacturing in the factory makes it possible to obtain plasters of optimal composition. However, for cost and management reasons, factory manufacturing involves the production of standard size panels.

Although there are different standard dimensions, both in length and width and thickness, it is often necessary to cut these panels to fit the widths and lengths of the walls or ceiling of the room to be equipped.

This cut, made on the site to the appropriate dimensions, must be fast and as sharp as possible to allow easy positioning of two panels contiguously.

Subsequently, a finish must be achieved by filling the gap between two adjacent plaster boards, using a product of filling such as plaster or plaster ready for use. Once deposited, this filler is smoothed with a knife to coat.

The finishing step must be as fast as possible. For that, it is necessary to limit the number of gestures to be carried out by the user. Clear cutting of the panels would not only limit the amount of filling product used, but also the number of actions to be performed to smooth the surface on and in the vicinity of the gap.

Several solutions exist for cutting a board of plasterboard.

The most common is to "mark" the panel with a cutter blade (a cutter blade, known from the state of the art and illustrated in Figure 1, is constituted by a plate having a doubly beveled edge, that is, that is, both faces of the plate are bevelled).

This operation allows the cutting of the first sheet of cardboard and the grooving of the plaster layer. Then, the operator exerts a stress on the panel so that the plaster layer breaks in two parts along the groove. Finally, the operator cuts the second sheet of cardboard with his cutter to release the two panel parts. Generally, in this last step, the second sheet of paper is torn off rather than cut, which creates an irregularity on the surface of the plaster board to be filled during the finishing.

This solution is dangerous for the operator because of the use of the cutter. Indeed, the grooving obtained is never rectilinear, even with the use of a guide, and it often happens that the speed of the grooving movement causes a sudden deviation of the blade of the cutter from the guide to the body of the user.

This solution also has a major technical disadvantage. Firstly, the use of a cutter blade generates non-rectilinear grooves so that the breakage can take such irregular shapes that a new panel must be used and cut. Then, the cutting edge, obtained after breaking the plaster layer, is still very irregular, even with long experience. It is difficult to adjust two consecutive panels whose cutting edge is irregular. In addition, when finishing, use a large amount of filling material to obtain a perfectly flat surface between the two consecutive panels.

It is for this reason that some societies forbid this practice to their workers. Some public institutions even forbid this practice in their tenders, but in practice this is the most widely used method.

To solve this problem, some operators have proposed a second cutting solution consisting of using a handsaw or jigsaw. The teeth of the blade of this saw must be carefully selected to avoid splinters of plaster and generate an irregular cutting edge. For the same reason, the speed and the cutting frequency must also be adapted, which requires an important know-how.

Well done, this second cutting solution provides a clean cutting edge. Nevertheless, this solution is longer than manual cutting with the cutter. In addition, boards plasterboard thin (less than or equal to 18 millimeters) are unsuitable for the use of a saw. This solution becomes interesting only for thicknesses greater than 18 millimeters because beyond this thickness, the stress to be exerted to break the plaster layer is too great and the breakage does not necessarily follow the groove.

The object of the present invention is therefore to provide a solution for rapid and clean grooving of a plasterboard board.

Another objective is to propose a complete cutting solution of a plasterboard plate, allowing both to obtain a plane cutting edge, that is to say without plaster projection, and a clean cut of the sheet (s) of paper or cardboard. For this, the invention proposes to perform the cutting in three main stages, using a blade having a shape and a particular sharpening: a grooving step, a step of breaking the plasterboard, and a step of leveling the cutting edge.

To this end, the invention relates to a cutting blade of a plasterboard board, comprising at least one grooving corner having a flat face and a beveled face.

The bevelled face allows the cutting of the first sheet of cardboard and the grooving of the plaster layer, and the flat face keeps the blade in the same position during the grooving of the plaster. The inventor realized that it is this maintenance of the position of the blade that allows to obtain a cutting edge much more regular than when using cutter blades. These being bevelled on each face, it is impossible, even with a guide, to maintain the blade in position, so that these blades chase and the cutting edge obtained later is irregular.

According to other embodiments:

• The grooving corner can be extended by a leveling edge with a flat face and a bevelled face identical to those of the corner.

The cutting blade may further comprise at least one cutting notch arranged between the grooving wedge and the leveling edge.

• The tapered face can make an angle with the flat face between 15 ° and 25 °, preferably 20 °.

· The or each grooving corner may have a connection facet;

• the leveling edge may have a length greater than the thickness of the board of plasterboard;

• the cutting notch can be curved;

· The cutting blade may be constituted by a rectangular plate having two faces and comprising: - four grooving corners;

four cutting notches;

- four edges of leveling,

two diametrically opposed grooving wedges being symmetrical with respect to the center of the rectangular plate, two consecutive grooving wedges having opposite flat face and beveled face; and or

The cutting blade may consist of a rectangular plate having two faces and comprising:

- four grooving corners;

- four cutting notches;

- four edges of leveling,

two diametrically opposite grooving wedges being symmetrical with respect to the center of the rectangular plate and two consecutive grooving corners having the same plane face and the same bevelled face.

The invention also relates to a method of implementing a blade according to the invention, for cutting a board of plasterboard, the method comprising the following steps:

- provide a plaster board with a layer of plaster between two sheets of cardboard or paper;

- Apply the grooving corner on the panel so that the flat face of the grooving corner is perpendicular to the panel, and move the blade thus positioned to cut the first sheet and groove the plaster layer;

According to other embodiments, the method may comprise the following subsequent steps:

folding the panel along the groove obtained in the previous step to break the plaster layer along the groove and obtain a cutting edge; - Put the cutting notch in engagement with the second sheet of cardboard and apply the edge of leveling against the cutting edge obtained in the previous step, then move the blade thus positioned to trim the cutting edge while cutting the second sheet of cardboard.

The invention also relates to the use of a blade according to the invention, comprising at least one grooving wedge, at least one cutting notch and at least one leveling edge, for cutting a panel of plasterboard.

Other features of the invention will be set forth in the detailed description below, made with reference to the appended figures which represent, respectively:

Figure 1 is a schematic sectional view of a cutter blade illustrating the state of the art;

- Figure 2, a schematic plan view of a first embodiment of a blade according to the invention;

Figure 3 is a schematic sectional view along the line III-III of the blade of Figure 2;

Figures 4 and 5 are schematic plan views of two embodiments of a blade according to the invention;

Figure 6 is a partial schematic perspective view of the blade of Figure 5;

Figures 7 to 9, schematic plan views of three other embodiments of a blade according to the invention;

- Figures 2a, 5a and 6a, schematic views of variants, respectively, of the blades of Figures 2, 5 and 6;

Figures 10 to 13, schematic perspective views of an implementation of the cutting method according to the invention;

Figure 14, a partial enlargement in perspective of Figure 13 illustrating the surface condition obtained after leveling the edge of the plasterboard board; Figure 15 is a schematic left side perspective view of an exemplary support carriage of a blade according to the invention;

Figure 16 is a partial schematic perspective view from above, with respect to the position of use, a cutting guide used with a blade according to the invention;

Figure 17 is a schematic partial perspective view of an end of a cutting guide used with a blade according to the invention; and

Figure 18 is a schematic plan view of a step of positioning a cutting guide according to the invention.

Unlike the cutter blade illustrated in FIG. 1 and comprising a doubly beveled cutting edge, a cutting blade 300 according to the invention, illustrated in FIG. 2, comprises at least one grooving wedge 301 having, in section, a planar face 300a and a bevelled face 300b (see Figure 3). The corner is defined by, on one side, a flat face, and on the other side, by a bevelled face having two bevelled edges 308. The two bevelled edges 308 are connected by at least one connecting line 309.

This particular shape of the cutting edge of the blade ensures a perfectly straight grooving by preventing the blade from oscillating during grooving, contrary to what is observed with a cutter blade.

The bevelled face allows the cutting of the first sheet of cardboard and the grooving of the plaster layer, and the flat face keeps the blade in the same position during the grooving of the plaster. The inventor has found that it is this maintenance of the position of the blade perpendicular to the plasterboard board that allows to obtain a perfectly straight groove and a cutting edge much more regular than when using cutter blades. These being bevelled on each face, it is very difficult, even impossible, even with a guide, to keep the blade in position, so that these cutter blades hunt and the cutting edge obtained later is very irregular. The best results have been obtained with an angle γ between the flat face and the beveled face between 15 and 25 degrees, and preferably an angle γ of 20 degrees. Thus, when the bevel has such an angle, the blade remains perfectly straight and does not oscillate during grooving. In addition, the grooving obtained has a depth and a shape such that when the user bends the board of plasterboard (see Figure 1 1), the edge obtained is much more regular than that obtained with a cutter blade.

To further improve the regularity and flatness of the cutting edge, the blade further comprises a leveling edge 302 also having a flat face and a bevelled face. The leveling edge 302 has a length L1 greater than or equal to the thickness of the gypsum board. If this thickness is denoted e, the length L1 of the leveling edge must be greater than or equal to: e / sinus β, where β is the angle between the blade and the plasterboard during the leveling step .

Advantageously, the grooving step and the leveling step is performed with a cutting carriage carrying the blade according to the invention, and slidably mounted on a cutting guide. A carriage particularly adapted to the implementation of the blade and a guide will be described with reference to Figures 15 to 18.

In a particularly advantageous embodiment, the blade comprises between the grooving wedge 301 and the leveling edge 302, a cutting notch 303. This notch is useful when the plasterboard board comprises a sheet of paper or cardboard on the underside of the plaster board, in the cutting position. Thus during the step of leveling the cutting edge, this sheet of paper or cardboard is engaged in the notch 303 which allows clean and clean cutting of the sheet and prevents this sheet to be simply torn. Advantageously, to facilitate this cutting, the cutting notch is curved. The concomitance of the leveling of the cutting edge and the cutting of the lower sheet of paper makes it possible to obtain a cut plasterboard board, none of the sheets of paper being torn and whose cutting edge is without any protuberance and follows perfectly the grooving line. When a guide is used, the cutting edge is parallel to the guide (so perfectly straight if the guide is a straight edge). The juxtaposition of several plasterboard panels cut with the blade according to the invention is optimized, and the amount of filling materials for finishing is greatly limited. In addition, the fact that the sheets of paper or cardboard are not torn off, avoids having to fill the irregularities on the surface of the board of plasterboard.

In general on a construction site, it is necessary to carry out many cuts of boards of plasterboard. All of these cuts wear the blade so that the blade may become dulled during cutting movements (see Figures 10-14). The grooving is no longer rectilinear and, when the user folds the cardboard panel (see Figure 8) the cutting edge may no longer be perfectly parallel to the grooving line and / or the guide, and may have a large diameter. irregularity (presence of many protuberances protruding). It is therefore necessary to change blades.

An embodiment of a particularly advantageous blade is illustrated in FIGS. 5 and 6. In this embodiment, the four corners of the plate constituting the blade are used as grooving wedges. Each of these corners is extended by a leveling edge. Between each corner and the leveling edge, the blade carries a cutting notch. In this embodiment, two diametrically opposite grooving wedges 31a-311a are symmetrical with respect to the center of the rectangular plate constituting the blade 310. On the other hand, two consecutive grooving wedges 31a-311b have a flat face and a groove. opposite beveled face. This means, as illustrated in FIG. 6, that a grooving wedge 311a has a beveled upper face and a flat lower face. On the contrary, a grooving corner 31 1b has a planar upper surface and a beveled lower face. The same goes for the other structures that are the leveling edges 312a and 312b and the notches cutouts 313a and 313b.

According to the invention, the blade has a hole 315 intended to cooperate with a bolt provided with a nut 112a (see FIG. 14) disposed in the housing 1 12 for receiving the blade of the carriage 100. The blade 310 also comprises holes 316 intended to cooperate with fixed rods disposed in the housing 1 12 to maintain the blade and prevent it from pivoting around the bolt January 12a. Of course, any other means for fixing the blade in the housing can be used, as long as this fastening means firmly holds the blade perpendicularly to the plaster board.

In this way, with a blade according to the invention, the planar face 300a of the blade 300 is held perpendicular to the plaster board during grooving and leveling.

The embodiment of FIG. 5 makes it possible to use the two groove wedges 311a by pivoting the blade and to use the two grooving wedges 31b to turn the blade. Thus, with the same blade 310, four grooving and leveling zones are obtained that can be used successively when one of these zones is worn.

Of course, as shown in Figures 7 and 8, the blade may have only two zones each comprising a grooving wedge, a leveling edge and a notch cutout.

FIG. 9 illustrates another embodiment of a blade according to the invention, suitable for both left-handed and right-handed users. This blade 320 has four grooving wedges 321, four leveling edges 322 and four cutting notches 323. In this embodiment, two diametrically opposite grooving wedges are symmetrical with respect to the center of the rectangular plate and two grooving wedges. consecutive have the same plane face and the same bevelled face. With this embodiment, it is possible to manufacture a blade can be used from left to right or from right to left.

To this end, it can be provided that the cutting carriage according to the invention is removable and can be configured for either a right-handed person or a left-handed person. Thus, the profile carrying the notches and the handle can be fixed on both sides of the frame. When there is a protective cover, it is also expected that this hood can be removed and fixed either for a right-handed person or for a left-handed person. Figures 1 to 6 illustrate an arrangement suitable for implementation by a right-handed user.

In the embodiment of Figure 9, the four corners are used to provide a right-handed and left-handed two cutting areas that can be used in succession when the first to be used is worn. Of course, it is possible to provide only one cutting area for a right-handed and only one cutting zone for a left-handed person.

The cutting method with a blade according to the invention is described below.

On a board of plasterboard, the user traces the cut that he wishes.

Then he places the blade according to the invention at a first edge of the panel.

The user positions the blade so that the grooving wedge is in sufficient contact with the panel to groove it, and the flat face of the blade is perpendicular to the panel.

The user then moves the blade, keeping it perpendicular to the panel, from the first edge of the panel 500 to a second edge of the panel. During this movement, the blade makes a groove in the plaster layer of the panel. If this layer of plaster is covered with a sheet of paper or cardboard, the blade cuts the sheet at the same time as it grooves the plaster.

Once, arrived at the second edge of the panel, the user folds the panel along the groove obtained in the previous step to break the plaster layer along the groove. This folding makes it possible to obtain a cutting edge. Due to the shape of the blade and its holding so that the flat face is perpendicular to the panel during movement, the groove obtained is regular and the resulting cutting edge is much more regular than the cutting edges obtained by the method of cutter cutting: the projections on the edge are much smaller and more regular than those obtained by the cutter cutting process.

To further improve the flatness of this cutting edge, the blade according to the invention advantageously comprises a leveling edge which allows to trim the cutting edge.

For this, the user positions the blade at the first edge 500a of the panel 500, so that the flat face of the leveling edge is applied against the cutting edge obtained at the folding step of the panel, and perpendicular to the faces of the panel. sign. The user moves the blade thus positioned again, so that the cutting edge is leveled by the blade perpendicular to the panel faces.

At the same time that the blade edges the cutting edge, it also cuts, if it is present, the sheet of paper or cardboard placed on the underside of the plaster board. For this purpose, it is advantageous to use a blade comprising a cutting notch (see FIGS. 4 to 9).

Thus, during positioning, the user puts the cutting notch in engagement with the second sheet of cardboard and applies the edge of leveling against the cutting edge obtained in the previous step, and then move the blade thus positioned to screed the cutting edge while cutting the second sheet of cardboard.

FIGS. 2a, 5a and 6a illustrate variants, respectively, of the blades of FIGS. 2, 5 and 6.

In these variants, the or each grooving wedge 301 -31 1 a-31 1b has a connecting face 307-317a-317b between the two beveled edges 308-318a-318b of the grooving wedge. The connecting face 307-317a-317b is delimited by two connecting lines 309-319a-319b, as well as by a connecting line 309c-319c with the face 300b. The connecting face 307-317a-317b forms a plane forming an angle δ with the plane face 300a. The angle δ is smaller than the angle γ of the beveled edges 308 with the flat face 300a. Advantageously, the angle δ is between 10 and 20, and preferably an angle δ of 15 degrees. The preferred embodiment is an angle γ of 20 degrees and an angle δ of 15 degrees.

The connection face 307-317a-317b facilitates the penetration of the blade in the plasterboard during grooving and limits the forces during the maneuver. In addition, the inventor has found that the effort that is exerted on the fall to break the plasterboard is also limited.

Indeed, the connecting face 307-317a-317b substantially improves the groove obtained during the grooving step (see Figure 10). When the connection face is absent, the single connecting line 309 can rub strongly against the plaster and tear off small pieces of plaster and paper or cardboard during the grooving. The groove may therefore sometimes present, especially when the grooving is very fast, abrasions that induce, when the panel is folded (see Figure 1 1), an uneven cutting edge. The connecting face 307-317a-317b limits the friction between the grooving wedge and the panel, so that the groove obtained is particularly regular. It has almost no scratch. The resulting cutting edge is very regular and has very few protrusions, and projections of small sizes. The subsequent step of leveling is thus facilitated and is only a finish to obtain a perfectly flat cutting edge, without any annoying projection for the positioning of two panels against each other.

Figures 10 to 14 illustrate the preceding cutting process, implemented with a carriage cooperating with a guide and carrying the blade according to the invention. This cutting system allows a very effective maintenance of the blade so that the flat face of the blade remains perfectly perpendicular to the faces of the plaster board during grooving and leveling.

On a plaster board 500, a cutting guide 200 is positioned along the cutting direction desired by the user. Before or after this positioning, the user slidably cooperates with the carriage 100 with the cutting guide 200.

Once the guide is positioned, the user places the carriage at a first edge 500a of the panel 500. In Figure 0, the first edge is located on the left; this provision is suitable for implementation by a right-handed user. This first edge is the one on the side of the slide of the carriage. Then, the user positions the carriage so that the grooving corner of the blade is in sufficient contact with the panel to groove it. The user then moves the carriage in the direction of the arrow F1, by pulling the carriage, from the first edge 500a of the panel 500 to the second edge 500b of the panel 500. During this movement, according to the arrow F1, the The blade makes a groove 501 in the plaster layer of the panel 500. If this layer of plaster is covered with a sheet of paper or cardboard, the blade cuts this sheet at the same time as it grooves the plaster.

During this movement, the only concern of the user is to pull the carriage between the two edges of the panel to groove and cut this panel. It does not have to worry about the inclination of the blade that is held perpendicular to the panel by the truck. Thanks to this, the groove is perfectly regular as much in its shape along the panel as in its depth.

Once, arrived at the second edge 500b of the panel, the user folds the panel along the groove obtained in the previous step to break the plaster layer along the groove. This folding in the direction of arrows F2 (see Figure 1 1) provides a cutting edge 502 shown in Figure 12. Due to the perfect straightness of the groove, the resulting cutting edge is much more regular than the songs cutting obtained by the cutter cutting process. To further improve the flatness of this cutting edge, the carriage according to the invention proposes a position of the handle, and therefore of the blade, which makes it possible to trim the cutting edge 502. For this, as illustrated in FIG. , the user moves the carriage from the second edge of the panel to the first edge of the panel, then he positions the blade so that the flat face of the leveling edge is applied against the cutting edge obtained in the step of folding the panel. The user moves the carriage again from the first edge 500a to the second edge 500b, so that the cutting edge is leveled by the blade. This step is illustrated in FIGS. 12 and 13. The latter FIG. 13 shows the unmounted cutting edge 502 on the right of the figure and a recessed cutting edge 502a on the left of the figure. Of course, the cutting edge 503 of the chute 504 of the panel 500 is not leveled during this step.

At the same time that the blade edges the cutting edge, it also cuts, if it is present, the sheet of paper or cardboard placed on the underside of the plaster board.

As when grooving, the user does not have to worry about the inclination of the flat face of the blade during the leveling.

FIG. 15 illustrates an embodiment of a cutting carriage of a plasterboard panel particularly adapted to the implementation of the blade according to the invention.

The carriage 100 comprises a frame 101 provided with means for slidingly cooperating with a cutting guide 200. The cooperation means are, in this embodiment, rollers 102 provided with a groove 102a intended to receive a portion 201 a d a rail 201 carried by the guide 200. Such a guide will be described in more detail in connection with Figures 16 to 18.

The rollers 102 make it possible to slide the frame 101 along the rail 201. The frame 101 comprises a handle 1 10 rotatably mounted relative to the frame 101. The handle comprises a gripping means 1 1 1 constituted, in this embodiment, by a profiled handle.

The handle also includes a housing 12 for a cutting blade 300.

The frame 101 also comprises a profile 120 provided with three notches A, B and C. These notches are intended to lock in rotation the handle 1 10 through the engagement of a retractable claw 1 13 carried by the handle. Advantageously, the retractable engagement claw is coupled to a trigger 1 15 connected to a tension spring 1 14 pressing the claw towards the bottom of the notches.

In this way, the user who holds the handle 1 10 by the handle 1 1 1 can retract the claw 1 13 out of the notch in which it is engaged (here the notch B) by pulling, with a finger of the placed on the handle 1 1 1, the trigger 1 15, against the tension spring 1 14. It can then rotate the handle 1 10 relative to the frame 101 until the claw 1 13 engages in another notch A or C.

Thanks to the profile 120 and the notches A, B and C, the handle can be positioned in a preset manner in three angular positions by reversible engagement of the retractable claw 1 13 in the notches.

These notches are arranged on the profile, so as to allow, in use:

for the first notch A, an arrangement of the blade 12 out of contact with the plaster board;

- For the second notch B, a provision of the blade at an angle with a board of plasterboard, in sufficient contact with the panel to groove to form a cutting edge (see Figures 10 and 1 1);

- For the third notch C, a provision of the blade 300 at an angle β with the plasterboard board, in sufficient contact with the panel to trim the cutting edge (see Figures 13 and 14) and cut a possible sheet of paper or cardboard carried by the underside of the panel (the lower face being the face opposite to that carrying the guide 200 and / or the carriage 100).

Preferably, the carriage 100 further comprises a guard 130 of the blade 300, when the claw 13 is engaged in the first notch A. In this position, the blade is out of contact with the cardboard panel. plaster. This position is, advantageously, a secure transport position in which the blade is inaccessible to the user who can not injure himself with the blade.

Thanks to the profile 120 provided with notches, the angular positions of the handle are predetermined and preset. Thus, the user does not need to pay attention to the angle α or β of the blade relative to the board of plasterboard. He just has to go from one notch to another to get the different positions of the blade. His only concern is to move the guide relative to the panel.

The angular position of the third notch C depends on the thickness of the plaster board. In the illustrated example, the third notch C is spaced from the second notch B to allow the leveling of a cutting edge of a gypsum board with a thickness e1 (see Figure 14).

Advantageously, the carriage may comprise at least one additional notch (for example notches D and E) spaced from the third notch C to allow the leveling of a cutting edge of a plasterboard board with a thickness of e2 or e3 different from the thickness e1 can be leveled when the trigger is engaged in the slot C. The skilled person can provide as many notches as necessary, depending on the number of panel thicknesses to be cut by the carriage according to the invention. For example, notch C might allow the edge of a 10mm thick plaster board to be trimmed, a D notch could be used to trim the edge of a 13mm thick panel (typically called , in France, "BA13 panel"), and a Notch E could allow the leveling of the cutting edge of a panel 15mm thick. Other notches could be provided for other thicknesses.

In this case, it is necessary to provide a length L1 of the leveling edge greater than or equal to the thickness of the gypsum board divided by the sinus of the smallest angle β of the notches C, D or E.

With such a carriage, the grooving step illustrated in FIG. 10 is carried out by actuating the retractable engagement claw to remove it from the notch A of the transport position and rotating the handle until the claw engages in the second notch B.

Similarly, the leveling step illustrated in FIG. 13 is implemented by actuating the retractable engagement claw to remove it from the second notch B and rotating the handle until the claw engages in the third notch C.

The preceding cutting carriage advantageously comprises means for slidingly cooperating with a cutting guide.

A particularly suitable cutting guide has a profiled rail like that illustrated in FIG. 16. This carriage guide has two longitudinal edges 200a and two ends 200b.

In a particularly advantageous embodiment, the guide 200 has a profiled rail 201, intended to cooperate with the wheels 102 of the carriage (see Figures 15), this rail 201 being extended laterally by flat areas 202 increasing the contact surface between the guide and the plaster board.

The rail 201 can have any type of shape. A particularly advantageous form, illustrated in Figure 16, allows better stability and better sliding support of the carriage according to the invention. Around a longitudinal groove 203, the rail 201 comprises two longitudinal protuberances 204. Each of these protuberances has a portion 201a intended to cooperate slidably with the wheels 102 of the carriage 100. Each portion 201 comprises two non-coplanar 205-206 rectilinear surfaces connected by a solid surface 207 substantially perpendicular to the contact face 208 of the guide 200 with the plasterboard board.

The flat areas 202 preferably have a width L2 adjusted so that, in use, the cutting blade 300 is in tangential contact with the longitudinal edge 200a of one of the flat areas 202. Thanks to this, the user can easily position the guide since it suffices to make coincide the edge of the solid area with the marking line of the cutout previously drawn by the user. In addition, the contact between the solid 202 and the blade prevents it from oscillating under the action of the movement of the carriage. With a blade according to the invention, it is the flat face of the blade which is applied against the solid 202, and not the beveled face. This further enhances the guiding of the blade by optimizing the contact area between the blade and the guide.

Preferably, the cutting guide according to the invention may have holding means disposed on the face 208 intended to be in contact with the gypsum board. These holding means may comprise points intended to be stuck in the plasterboard plaster board.

Thus, when the user has positioned the guide in the desired manner, it suffices to press this guide so that the tips of the holding means are planted in the panel and prevent, during the various cutting steps (see Figures 10 to 14) the guide moves from its position of use.

The tips can be worn by rods or be retractable to prevent that, when the guide is not used, the tips do not hurt the user. To this end, the tips may be carried, for example, by screws inserted in the longitudinal groove 203. When the user wants to use the guide, it removes the screws from the plane of the surface 208, with a screwdriver. When the user has finished his cuts, he unscrews the screws until they come out of the plane of the surface 208. Advantageously, these The screws have a length such that, when they are not screwed, they are held in the groove 203 and prevent the carriage from cooperating with the rail.

Any other means that can make the tips retractable can be used in the guide according to the invention.

Preferably, the holding means 209 are arranged on the face 208 of the guide so that, in use, after the cutting of the plasterboard, the holes formed by the points planted in the plasterboard board are located at a distance from one another. determined distance d of the cut, sufficient so that the holes are closed together with a junction between two panels of plasterboard.

For example, the holding means 209 are arranged at the distance d from the edge 200a of the guide.

Conventionally, the finishes are carried out using a coating knife with a width of between 150 mm and 300 mm.

Thus, the tips of the holding means will preferably be arranged at a determined distance of between 75 mm and 150 mm, preferably between 70 mm and 120 mm, advantageously between 55 mm and 80 mm, typically 65 mm.

The holes formed by the tips are arranged in an area particularly close to the cutting edge, so that the finish does not need to include a specific step of filling these holes, independent of the filling of the space between two consecutive panels .

Advantageously, the cutting guide comprises, at least at one end 200b of the rail 201, a stop 210 rotatably mounted relative to the rail 201. Advantageously, the stop is provided with holding means, in use, against the board of plasterboard. In the embodiment illustrated in FIG. 17, this holding means comprises a point 21 1 intended to be stuck in the thickness of the plasterboard board. Thus, the user has the stop 210 against an edge of the plasterboard, and maintains this stop against this panel by pressing the tip 21 1 in the thickness of the plaster board. Then, since the abutment 210 is rotatably mounted relative to the rail 201, it can angularly position at its choice the guide on the plaster board as shown in Figure 18.

The holding means can be retractable. For example, a tip 21 1 is carried by a screw.

Preferably, the rotational mounting of the abutment 210 relative to the rail 201 can be controlled using a wheel 212.

According to a non-illustrated embodiment, the stop 210 comprises two parts connected to one another by a hinge.

The two articulated parts may be provided with holding means of the plasterboard board. For example, the holding means may be spikes and / or comprise a plate arranged to allow the strength of the plaster board to be maintained between this plate and the articulated parts. This arrangement can be obtained by making the hinged parts into a profiled structure.

The abutment may advantageously comprise an end stop that allows limited rotation of the articulated parts. In practice, the end stop rotation advantageously limits the rotation between 0 and 45 degrees, and preferably between 0 and 30 degrees.

Thanks to these articulated parts, by means of holding the plasterboard board, and the end stop rotation, the user can make a single cut of a board of plasterboard large without risk that the Fall 504 (see FIG. 13) does not fall during the flush step, thus tearing the bottom sheet of paper and / or breaking.

Indeed, when the user breaks the panel along the groove (see Figure 11) and begins the leveling of the cutting edge (see Figures 13 and 14) the end of the already released fall is maintained by the articulated portion of the stop. According to other embodiments not illustrated, the rail of the guide may comprise a retractable stop means to allow in use, the coupling and decoupling of the rail with the carriage. Thus, when the carriage is coupled to the rail, the retractable stop means prevents, in the movement, the carriage from the rail. After use, for ease of transport, it is desirable to decouple the carriage and rail. The user then deactivates the retractable stop means and removes the carriage from the rail. For example, it is possible to use as retractable stop means a pin provided with a return means.

It is also possible, alternatively or in combination, to provide at least one of the ends of the rail with a damping means, in use, the sliding of the carriage at the end of the race. Thus, the truck can not violently hit the retractable stop means or, the truck can not come out of the rail violently. For example, a spring or a piston may be used as damping means.

Claims

1. Cutting blade (300, 310) of a board of plasterboard (500), characterized in that it comprises at least one grooving wedge (301, 31 1a, 311b) having a flat face (300a ) and a bevelled face (300b).

2. Cutting blade according to claim 1, wherein the grooving wedge (301, 31 1a, 311b) is extended by a leveling edge (302, 312a, 312b) having a plane face and a bevelled face identical to those of the corner.

3. Cutting blade according to one of claims 1 or 2, further comprising at least one cutting notch (303, 313a, 313b) arranged between the grooving wedge and the edge leveling.

4. Cutting blade according to any one of claims 1 to 3, wherein the beveled face makes an angle (γ) with the flat face between 15 ° and 25 °, preferably 20 °.

5. Cutting blade according to any one of claims 1 to 4, wherein the or each grooving corner (301, 31 1a, 31 1b) has a connecting facet (307, 317a, 317b).

6. Cutting blade according to any one of claims 2 to 5, wherein the leveling edge has a length (L1) greater than the thickness (e1, e2, e3) of the gypsum board (500). .

7. Cutting blade according to any one of claims 3 to 6, wherein the cutting notch is curved.

8. Cutting blade according to any one of claims 3 to 7, constituted by a rectangular plate having two faces and comprising:

four grooving wedges (31 1a, 31 1b);

four cutting notches (313a, 313b);

four alignment edges (312a, 312b), two diametrically opposed grooving wedges (311a-311a) being symmetrical with respect to the center of the rectangular plate, two consecutive grooving wedges (311a-311b) having opposite flat face and beveled face.

9. Cutting blade according to any one of claims 3 to 7, constituted by a rectangular plate having two faces and comprising:

four grooving wedges (311a);

four cutting notches (313a);

four leveling edges (312a),

two diametrically opposed grooving wedges (311a-311a) being symmetrical with respect to the center of the rectangular plate and two consecutive grooving wedges (311a-311a) having the same flat face and one bevelled face.

10. A method of implementing a blade according to any one of claims 1 to 9, for cutting a board of plasterboard, characterized in that it comprises the following steps:

- providing a gypsum board (500) comprising a layer of plaster between two sheets of cardboard or paper;

- applying the grooving wedge (301, 311a, 311b) on the panel so that the plane face (300a) of the grooving wedge is perpendicular to the panel, and moving the thus positioned blade to cut the first sheet and groove the layer of plaster;

11. Method according to the preceding claim, for the implementation of a blade according to any one of claims 3 to 9, comprises the following subsequent steps:

- folding the panel along the groove obtained in the previous step to break the plaster layer along the groove and obtain a cutting edge (502);

- putting the cutting notch (303, 313a, 313b) in engagement with the second sheet of cardboard and applying the leveling edge (302, 312a, 312b) against the cutting edge obtained in the previous step, then moving the blade thus positioned to trim the cutting edge (502a) while cutting the second sheet of cardboard.

12. Use of a blade according to any one of claims 3 to 9, comprising at least one grooving wedge (301, 311a, 311b), at least one cutting notch (303, 313a, 313b) and at least one recess edge (302, 312a, 312b) for cutting a plaster board (500).