The present invention relates to a nail plate feeding apparatus, having a frame, a feeding station for receiving a nail plate or a pair of nail plates, a discharging station for discharging the nail plate or the pair of nail plates, which discharging station is spaced from the feeding station, and moving means for moving the nail plate or the pair of nail plates from the feeding station to the discharging station. The invention also relates to a method of moving the nail plate or the pair of nail plates from the feeding station to the discharging station.

Industrially manufactured wood structures, such as nail plate trusses, structural parts are joined together by means of nail plates. In order to reach the operation and strength planned for the structures, it is important that the nail plates are precisely placed in the intended spot and position in the joining point. In the nail plate structures, the nail plates have traditionally been positioned and pre-fixed in place in the joining points of the structures by hand and then clamped fast by means of a C-clamp.

In automatic wood structure manufacturing lines, pairs of nail plates are first inserted into the mouth of a C-clamp where the nail plates are magnetically attached to the lower and upper jaws of the clamp's mouth. The clamp is then guided to the intended joining point after which the nail plates are pressed fast on both sides of the joining point. In order to have the exactly right position in the finished structure, the nail plates must be fixed to the jaws of the C-clamp with great accuracy. As there are no automatic feeding apparatuses, the pairs of nail plates must be installed into the mouth of the clamp by hand, which increases the manufacturing costs of the structure. Therefore, a feeding apparatus receiving nail plates from a conveyor and moving them exactly to the intended position in the mouth of a clamp, is needed to enable the making of a nail plate joint to be completely automated.

The objective of the invention is to provide a nail plate feeding apparatus and a method of moving a nail plate or a pair of nail plates from a feeding station to a discharging station, especially into the mouth of a C-clamp, to solve the problems associated with the prior art.

The objectives of the invention are achieved by a nail plate feeding apparatus and method which are characterized by what is set forth in the independent claims. Some preferred embodiments of the invention are disclosed in the dependent claims.

The invention relates to a nail plate feeding apparatus, having a frame, a feeding station for receiving a nail plate or a pair of nail plates, and a discharging station for discharging the nail plate or the pair of nail plates. The discharging station is spaced from the feeding station. The apparatus also includes moving means for moving the nail plate or the pair of nail plates from the feeding station to the discharging station. The feeding apparatus is characterized in that the moving means comprise a first edge guide for supporting a first edge of a nail plate or a pair of nail plates, and a second edge guide for supporting a second edge of said nail plate or pair of nail plates. The first and second edge guides have a first end extending to the feeding station and a second end extending to the discharging station. The first and second edges are opposite edges of the nail plate or pair of nail plates. Preferably, the edge guides are substantially parallel.

Preferably, the first edge guide is provided with a groove for receiving the first edge of the nail plate or pair of nail plates and the second edge guide is provided with a groove for receiving the second edge of the nail plate or pair of nail plates. The apparatus is especially adapted to move pairs of nail plates comprising two nail plates of the same size, with their toothed sides facing each other. The lower edge of the groove in the edge guide is thus positioned against the toothless face of the lower nail plate of the pair of nail plates, whereas the upper edge of the groove is positioned against the toothless face of the upper nail plate of the pair of nail plates. The bottom of the groove is positioned against the edges of the nail plate. The edges of the groove thereby prevent the nail plates of the pair of nail plates from drifting apart from each other during the moving.

In a preferred embodiment of the feeding apparatus according to the invention, the first edge guide and the second edge guide comprise a bend at a distance from the first end of the guides, whereby the groove width is substantially constant in the portion between the second end of the guide and the bend and increases from the bend towards the first end of the guides. The groove in the edge guides is therefore at its widest in the first end of the groove, i.e. in the feeding station facing end of the groove. The groove width refers herein to the distance between the upper edge and the lower edge of the groove. The edges of a single nail plate or a pair of nail plates are therefore easily inserted into the grooves as the nail plate or the pair of nail plates is fed to the feeding station from a side of the feeding station, in the longitudinal direction of the grooves.

In a second preferred embodiment of the feeding apparatus according to the in- vention, the first edge guide and the second edge guide are movable in the direction of a feeding line extending from the feeding station to the discharging station. The edge guides can be moved to a first position where their first ends extend to the feeding station and to a second position where their second ends extend to the discharging station. Therefore, the length of the edge guides does not have to be equal to the distance between the feeding station and the discharging station, i.e. as the edge guides are in the first position, their second ends can be spaced from the discharging station.

In a third preferred embodiment of the feeding apparatus according to the inven- tion, the first edge guide and/or the second edge guide are movable perpendicularly to the longitudinal direction of the edge guides, i.e. the distance between the edge guides is adjustable. This allows the distance between the edge guides to be adjusted suitable for nail plates and pairs of nail plates of different sizes. In still another preferred embodiment of the feeding apparatus according to the invention, the moving means comprise a support member movable to a first position, where at least a part of the support member lies in the plane defined by the grooves in the edge guides, and to a second position where the support member lies outside the plane defined by the grooves in the edge guides. As the support member is the first position, it lies in the travelling path of the nail plate or the pair of nail plates, thus preventing the nail plate or the pair of nail plates from crossing the support member. Correspondingly, as the support member is the second position, it does not stop or prevent the nail plate or the pair of nail plates from moving. Preferably, said support member is located between the first edge guide and the second edge guide and is movable parallel with the normal of the plane defined by the grooves in the edge guides. In the second position, the support member may lie completely below the plane defined by the grooves in the edge guides.

In still another preferred embodiment of the feeding apparatus according to the in- vention, said moving means comprise at least one discharge support movable to a first position, where at least a part of the discharge support lies in the plane defined by the grooves in the edge guides, and to a second position where the discharge support substantially entirely lies outside the plane defined by the grooves W

4 in the edge guides. As the discharge support is the first position, it lies in the travelling path of the nail plate or the pair of nail plates, thus preventing the nail plate or the pair of nail plates from crossing the discharge support. Correspondingly, as the discharge support is the second position, it does not stop or prevent the nail plate or the pair of nail plates from moving. In the second position, the discharge support member may lie completely below the plane defined by the grooves in the edge guides, allowing a single nail plate or a pair of nail plates to cross the discharge support. Preferably, said at least one discharge support is located between the first edge guide and second edge guide and is movable parallel with the normal of the plane defined by the grooves in the edge guides.

In still another preferred embodiment of the feeding apparatus according to the invention, said at least one discharge support has an edge face against which an edge of the discharging station can be fitted. The discharging station can be, for instance, the clamping face of the upper or lower jaw of a movable C-clamp, the edge of the discharging station thus being an edge of the clamping face of said C- clamp.

In the method according to the invention, a single nail plate or a pair of nail plates is moved from a feeding station to a discharging station. In the method, the nail plate or the pair of nail plates is fed to the feeding station in such a way that a first edge of the nail plate or the pair of nail plates is supported by a first end of a first edge guide and a second edge of the nail plate or the pair of nail plates is supported by a first end of a second edge guide. The nail plate or the pair of nail plates is then moved from the first end of the edge guides to the second end of the edge guides, supported by the edge guides. Finally, the nail plate or the pair of nail plates is removed from the edge guides to the discharging station.

In a preferred embodiment of the method according to the invention, the edge guides are moved to a first position where the first ends of the edge guides extend to the feeding station, and a nail plate or a pair of nail plates is arranged at the feeding station in such a way that the first edge of the nail plate or the pair of nail plates is supported by the first end of the first edge guide and the second edge of the nail plate or the pair of nail plates is supported by the first end of the second edge guide. The nail plate or the pair of nail plates is then moved from the first end of the edge guides to the second end of the edge guides, supported by the edge guides, and the edge guides are moved to a second position where the second ends of the edge guides extend to the discharging station. These steps are taken in a desired order. Finally, the nail plate or the pair of nail plates is removed from the edge guides to the discharging station.

In a second preferred embodiment of the method according to the invention, the nail plate or the pair of nail plates is moved from the first end of the edge guides to the second end of the edge guides by moving the edge guides towards the second position, whereby the nail plate or the pair of nail plates supported by the edge guides moves towards the discharging station. Thereafter, a support member extending to the plane defined by the nail plate or the pair of nail plates is arranged between the edge guides, on a first side of the nail plate or the pair of nail plates, i.e. on the side facing the feeding station thus preventing the nail plate or the pair of nail plates from crossing the support member. Finally, the edge guides are moved back towards the first position, whereby the nail plate or the pair of nail plates is pressed, forced by the support member, to the second end of the edge guides.

In a third preferred embodiment of the method according to the invention, the nail plate or the pair of nail plates is removed from the edge guides to the discharging station by arranging a discharge support between the edge guides, on a first side of the nail plate or the pair of nail plates, having an edge face bordered by the edge of the discharging station, which edge face extends to the plane defined by the nail plate or the pair of nail plates. The edge face of the discharge support thus prevents the nail plate or the pair of nail plates from crossing the edge face. Thereafter, the edge guides are moved towards the first position, whereby the nail plate or the pair of nail plates falls from the second end of the edge guides to the discharging station.

In still another preferred embodiment of the method according to the invention, the discharging station is located in the mouth of a clamp, preferably a movable C- clamp, and the nail plate or the pair of nail plates is moved into the mouth of the clamp, onto the clamping face of the lower jaw of the clamp. Preferably, the clamping face of the jaws of the clamp is provided with a magnet adhering to the nail plate or the pair of nail plates. In still another preferred embodiment of the method according to the invention, the nail plate or the pair of nail plates is fed to the feeding station from a conveyor or from a nail magazine. W 201

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An advantage of the invention is that it allows a nail plate joint to be made fully automatically without any manual steps. Thus, the invention significantly reduces the manufacturing costs of the nail plate joint. A still another advantage of the invention is that, due to the precise positioning of the nail plates, they do not have to be "over-dimensioned" to compensate for any positioning errors. Thus, the invention results in material costs savings.

In the following, the invention will be explained in detail. The description refers to the accompanying drawings wherein figure 1 is an exemplary oblique top view of a nail plate feeding apparatus according to the invention, figure 2 is an exemplary view of the second lateral support of a nail plate feeding apparatus according to the invention, as removed from the apparatus, and figures 3a to 3f are a sequence of views showing the operation of a nail plate feeding apparatus according to the invention.

Figure 1a is an exemplary oblique top view of a nail plate feeding apparatus according to the invention. The feeding apparatus has a frame comprising an upper plate 0, a lower plate 12 and four legs 14 connecting the upper and the lower plates to each other. Two adjacent, substantially parallel adjusting guides 20 are placed on a first face of the upper plate on which two elongated lateral supports, a first lateral support 16a and a second lateral support 16b, are supported through a sliding connection, substantially perpendicularly to the adjusting guides. The first and the second lateral supports are substantially parallel with each other. The sliding connection allows the lateral supports to be moved parallel with the adjusting guides to alter the distance between the lateral supports. The lateral supports can be locked to the adjusting guides to lie at a desired distance from each other.

A first edge guide 24a is placed on the lateral face of first lateral support facing the second lateral support and a second edge guide 24b is placed on the lateral face of the second lateral support facing the first lateral support, respectively. The edge guides are structurally identical and shaped as mirror images of one another. The edge guides lie on the lateral supports in a substantially parallel position to define a gap of a substantially uniform width between them. The edge guides are provid- ed with a groove 26 extending in the longitudinal direction of the edge guides and from a first end of the edge guide to a second end of the edge guide.

Between the lateral supports, at a first edge of the upper plate, a fixing plate 18 is provided, having a cylinder with a projecting rod-like support member 22, at its point farthest away from the upper plate. The cylinder is located on the lower face of the fixing plate, i.e. on its face not shown in the figure 1 , and the support member projects through a hole in the fixing plate, out of a second face of the fixing plate, out of its upper face shown in figure 1. In figure , the support member is in a first position where its upward pointing free end extends above the plane defined by the grooves 26 in the edge guides. The support member is also movable to a second position where its upward pointing free end lies below the plane defined by the grooves in the edge guides. The second ends of the lateral supports are provided with elongated discharge supports 28 which are substantially parallel with the edge guides. The discharge supports are fixed to the ends of the lateral supports by means of a moving mechanism 30 to allow the discharge supports to be lifted to a first position where the discharge support extends between the edge guides, to the plane defined by the grooves in the edge guides, and to be lowered to a second position where the discharge supports lie below the plane defined by the grooves in the edge guides. The moving of the discharge support to the above-mentioned positions takes place by means of a motor included in the moving mechanism. The free ends of the discharge supports pointing away from the upper plate have an edge face 29 against which a jaw of a tool, such as a jaw of a C-clamp, can be fitted.

The upper face of the upper plate includes a rectangular cavity 42 in the middle of which, above the cavity, runs a moving shaft 44. The moving shaft is fixed, at a first end and at a second end thereof, to a first, lateral support facing edge of the upper plate and to a second, lateral support parallel edge of the upper plate, respectively, by bearing boxes 46. The second end of the moving shaft is provided with a moving motor 48 for rotating the moving shaft.

Around the moving shaft, approximately in the middle of the moving shaft, seen in the longitudinal direction, a moving roller 45 is disposed. The outer diameter of the moving roller is bigger than the outer diameter of the moving shaft. The moving roller is dimensioned to touch, at its outer periphery, the plane defined by the lower edge of the groove 26 in the edge guides 24a, 24b. The lower face of a pair of nail plates inserted between the first ends of the edge guides, the ends of which lie against the lower face of the grooves in the edge guides, is thus, at its middle area, in contact with the outer face of the moving roller. As at least a part of the nail plate or the pair of nail plates is on the moving roller, the pair of nail plates can be moved in the longitudinal direction of the grooves by rotating the moving shaft and the moving roller fixed thereto.

Control electronics 50 for the motors and actuators of the apparatus, partly covered by a protective case 52, are provided on a first face of the lower plate which is its upward pointing face in figure . Gripping members 54 allowing the apparatus to be supported on fixing rails on the ground, movably parallel with the fixing rails (the fixing rails are not shown in the figure), are provided on a second face of the lower plate which is its downward pointing face in figure 1. The feeding apparatus also includes a motor for moving the apparatus along the fixing rails (the motor is not shown in the figure).

Figure 2 is an exemplary view showing the second lateral support 16b of a nail plate feeding apparatus according to the invention, and the parts associated therewith, as separated from the apparatus. The first lateral support of the feeding apparatus is structurally and functionally identical to the second lateral support but shaped as a mirror image thereof. The lateral support is, in cross-section, an L- shaped metal profile having a substantially flat first lateral face to be placed on the adjusting guides 20 (figure 1) on the surface of the upper plate 10 of the frame of the apparatus, and a second lateral face 32 extending in a right angle to the first lateral face. In the middle area of the second lateral face, a slide guide 34, which is substantially parallel with the longitudinal direction of the lateral support and to which the second edge guide 24b is fixed by means of a sliding carrier, is provided. Because the sliding carrier is disposed between the edge guide and the second lateral face, it does not show in the figure. The free edge of the second lateral face is provided with a gear rack 36 which substantially extends over the entire lateral face. A feeding motor 38 having a rotatable gear wheel (the gear wheel is not shown in the figure) is fixed to the first end of the edge guide. The teeth of the gear wheel are adapted to mesh with the teeth of the gear rack. The edge guide is thus movable in the longitudinal direction of the slide guide by using the moving motor.

The second edge guide 24b is provided with a groove 26 which substantially extends over the entire length of the edge guide and the first and the second ends of which open into the first end of the edge guide and into the second end of the edge guide, respectively. The groove is rectangular in cross-section, i.e. it has a lower edge, an upper edge and a bottom extending in a right angle to the lower and upper edges. The lower edge of the groove is a straight, flat surface substantially over the entire length of the groove. The upper edge of the groove, the area between the first and second ends of the edge guide, comprises a bend 40 where the upper edge changes direction. The groove width, i.e. the distance between the upper edge and the lower edge, is substantially constant between the second end of the edge guide and the bend. The width of the second end of the groove is dimensioned to be substantially equal to the height of a pair of nail plates consisting of two opposed nail plates. At the bend, the upper edge changes direction by turning to an oblique position relative to the lower edge. In the portion between the first end of the groove and the bend 40, the width of the groove changes rectilinearly to be at its greatest at the tip of the first end of the edge guide. The bottom of the groove is flat, substantially over its entire length, and parallel with the second lateral face. The tip of the first end of the groove is provided with a bevel to widen the mouth of the groove.

The second end of the lateral support comprises a moving mechanism 30 to which an elongated discharge support 28 is fixed. The moving mechanism serves to lift the discharge support to a first position where the discharge support extends between the edge guides, to the plane defined by the grooves in the edge guides, and to lower it down to a second position which is shown in figure 2 and where the discharge support lies below the plane defined by the grooves in the edge guides.

Figures 3a to 3f are a sequence of views showing the operation of a nail plate feeding apparatus according to the invention. The figures are top views of a feeding apparatus according to the invention and of a pair of nail plates being moved by it. A pair of nail plates 100 arrives at the nail plate feeding apparatus on a conveyor belt of a conveyor 200. The conveyor is stopped so as to position the pair of nail plates at the area bordered by the edge guides 24a, 24b. The pair of nail plates is moved from there, by pushing them with a pushing arm included in the conveyor, into a feeding station between the first ends of the edge guides 24a, 24b, to position the first and second edges of the pair of nail plates in the first end of the groove provided in the first edge guide 24a and in the first end of the groove provided in the second edge guide 24b, respectively. At this step, the edge guides are in their first position, i.e. in their extreme position in the direction of the first end of the lateral guides 16a, 16b. As the moving shaft is rotated by the moving motor 48, the pair of nail plates moves, forced by the moving roller, to the very edge of the uniformly tapered portion of the groove in the edge guides, to position the front edge of the pair of nail plates, lying farthest away from the conveyor 200, at the bend 40 of the groove (figure 3a). The pair of nail plates is now received into the feeding station of the feeding apparatus.

Next, the edge guides 24a, 24b are moved towards their second position, i.e. the second end of the lateral supports 16a, 16b. The pair of nail plates 100 is moved on the edge guides, carried by the edge guides, towards the second end of the lateral supports. At this step, the support member 22 is its second position, entirely below the plane defined by the lower face of the grooves in the edge guides. The pair of nail plates can cross the support member, supported by the edge guides. The edge guides are moved so far towards the second position that the pair of nail plates completely crosses the support member (figure 3b).

Then, the support member 22 is moved upwards to extend its upward pointing tip above the plane defined by the groove in the edge guides 24a, 24b, and the edge guides are moved back towards the first ends of the lateral supports. The elevated support member now prevents the pair of nail plates 00, but not the edge guides, from moving, i.e. the edge guides are moved towards the first ends of the lateral supports 16a, 16b while the pair of nail plates substantially stays in place. The edges of the pairs of nail plates project into the tips of the second ends of the grooves in the edge guides, i.e. into those groove portions where the groove width is substantially equal to the width of the pair of nail plates (figure 3c).

Next, the edge guides 24a, 24b are moved again towards the second position, the second ends of the lateral supports 16a, 16b. The discharge supports 28 are now in their second position, lying entirely below the plane defined by the lower face of the grooves in the edge guides, i.e. not in the travelling path of the pair of nail plates 100. The pair of nail plates moves, supported by the edge guides, to the discharging station bounded by the edge faces 29 of the free ends of the discharge supports 28 (figure 3e). With the edge guides in the second position, the discharge supports are lifted to their first position where their edge face extends to the plane defined by the grooves in the edge guides.

Then, a C-clamp is brought before the discharge supports 28 of the feeding apparatus to lightly support the edge of the clamping face 150 of the lower jaw of the clamp against the edge faces 29 of the discharge supports 28. The jaws of the C- clamp are moved so as to position the clamping faces of the lower and upper jaws of the clamp as close to the smooth lower face of lower nail plate of the pair of nail plates 100 as possible and as close to the smooth upper face of the upper nail plate of the pair of nail plates as possible, respectively. In practice, this means that, as the clamping faces are pressed against the walls of the second end of the edge guides 24a, 24b, there only is a narrow gap of the same width as the wall of the edge guides between the clamping face and the smooth face of the nail plate (figure 3e). Finally, the edge guides are moved towards the first position, i.e. the first ends of the lateral supports 16a, 16b. The edge of the pair of nail plates 00 now hits the edge faces 29 of the discharge supports 28 which prevent the pair of nail plates from moving along with the edge guides. The pairs of nail plates are thus removed from the edge guides, through the second ends of their grooves 26, to the dis- charging station, i.e. between the clamping faces 50 of the lower jaw and the upper jaw of the C-clamp. The clamping faces of the clamp are provided with magnets to attach the lower nail plate and the upper nail plate of the pair of nail plates to the clamping face of the lower jaw of the clamp and to the clamping face of the upper jaw of the clamp, respectively. The feeding apparatus has now accurately moved the pair of nail plates from the conveyor 200 to a desired position on the clamping faces of the C-clamp, and the clamp can be moved to a joining point in the nail plate structure to make a joint (figure 3f). The next pairs of nail plates are moved from the conveyor 200 into the mouth of the clamp in the same way. The nail plate feeding apparatus according to the invention operates fully automatically by means of the control electronics 50 included in the apparatus. The control electronics 50 control the operation of the moving motor 48 rotating the moving shaft 44 and of the feeding motor 38 moving the edge guides. Further, the control electronics 50 control the cylinder controlling the movement of the support mem- ber 22 as well as the moving mechanism 30 controlling the movement of the discharge supports (figure 1 ). The pair of nail plates thus moves from the feeding apparatus to the discharging station fully automatically by means of the control electronics and instructions input into them. The nail plate feeding apparatus and its control electronics can be integrated as part of an automatic nail plate structure assembling plant including a nail plate conveyor 200 and a C-clamp coupled to an arm of a programmable assembling robot. In this case, a common control unit of the assembling plant controls the conveyor moving the pair of nail plates, the nail plate feeding apparatus, the assembling robot and the C-clamp into the mouth of which the pairs of nail plates are fed.

The above describes preferred embodiments of the nail plate feeding apparatus and method according to the invention. The invention is not restricted to the above-described solutions but the inventive idea is applicable in many different ways within the scope of the claims.