Compressible holding member

Holding members for engaging the corners of base plates of nail plates while wooden beams are force down on the upwardly projecting nails to form a truss are made of resilient plastics material of about the same thickness as the base plate and provided with a self-adhesive surface for fixing them relatively to a preparation table. Each holding member is formed at one side so as to lie against the edge of the base plate at at least two points respectively on both sides of the the associated corner. A comparatively thin supporting layer of harder material may be secured on the upper face or between or on both faces of the resilient material.

FIELD OF THE INVENTION 
The invention relates to a self-adhesive holding member for positioning on 
a preparation table a nail plate which has at least three corners and 
which, for the purpose of producing a truss system of wood, can be pressed 
into the wood beams by means of a press at the junctions of the truss 
members. 
DESCRIPTION OF THE PRIOR ART 
For producing truss systems of wood, as are used for example for roof 
construction, it has long been known for the wood beams to be joined 
together at the junctions by means of nail plates which are pressed into 
the wood beams. Such connections may be made rapidly and inexpensively and 
comply with the requirements made, in respect of nondeformability and 
breaking strength. The nail plates are pressed into the beams in a 
substantially automatic mode of operation, using hydraulic presses. For 
this purpose, the wood beams are fitted together to form the desired truss 
structure on a preparation table, and are clamped in place. In this 
connection, it is the task of holding members always to position the nail 
plates at the same position at the junctions, so that after the pressing 
operation has been effected, it is only necessary for the fresh nail 
plates for the next operation to be laid on the preparation table. This 
mode of operation makes it possible greatly to reduce the preparation time 
required between the individual pressing operations. The holding members 
should not impede the pressing operation, and must ensure that the nail 
plates can be easily laid in place. 
To meet these requirements, it is already known to provide positioning pins 
on the preparation table, which positioning pins can be inserted into 
catch-like holes. The use of holding pins of this kind, which can also be 
screwed into the support at different positions thereon, permits fixing of 
the nail plate by arranging respective pins or pegs at those positions at 
which the nail plate has openings. 
The disadvantage of the known holding members is in particular that fitting 
the members, or setting them up for the first time, is time-consuming and 
complicated. In addition the positioning operation is imprecise as a 
threaded hole is not always available at the position at which there is an 
opening in a nail plate. 
SUMMARY OF THE INVENTION 
The invention is based on the problem of avoiding the disadvantages of the 
known method, in particular therefor providing a holding member which may 
be fitted in a very simple manner, which precisely positions the nail 
plate, and which is also cheap to produce, without requiring additional 
positioning members on the working table. According to the invention, this 
problem is primarily solved in that the holding member is adapted at one 
side to the outside configuration of the nail plate in such a way that it 
lies against the edges of the nail plate at at least two points on both 
sides of at least one corner. 
The holding members may be produced in a particularly advantageous and 
economical manner and without a severe waste of material if the holding 
members are in the form of a right angle and are produced by a process 
which is characterised in that punch lines are made on an endless 
strip-like web of material from both sides and at the same level of the 
web of material at an angle of 45 degrees and at a predetermined spacing 
which corresponds to the width of the holding members, in such a way that 
the punch lines on one side define the respective inside edge of a holding 
member and the punch lines are on the other side define the outside edge 
of the next following holding member. 
The advantages achieved with the invention are in particular that 
positioning of the nail plates on the preparation table may be effected 
more rapidly than in the conventional manner. It will be seen that just 
two holding members are sufficient for reliable positioning the nail 
plate. As the holding members embrace around the corners of the nail 
plate, precise fitting of the plate edge is relatively simple. In 
addition, holding members which are in the form of a right angle may be 
punched out of an endless foam material strip, without serious material 
wastage. 
It will be apparent that the invention may be employed both for the 
commercial rectangular nail plates and also for those of other shapes; as 
adapting the shape of the holding members for example to special nail 
plate shapes will not give rise to any problems. 
In order to ensure that the holding members are not pressed into the wood 
beams, the holding members are advantageously made from a resilient 
plastics material so that they are compressed in each pressing operation 
and return to their original position again when the truss is removed from 
the preparation table. 
The holding members which are made exclusively from resilient plastics 
material may in some cases suffer from the disadvantage that the nail 
plates slip sideways slightly or slew round slightly on the preparation 
table, when subjected to high lateral force components. The inherent 
elasticity of the soft plastics material does in fact permit the holding 
member to be upset in a lateral direction, in spite of its good adhesion 
to the preparation table. In the most disadvantageous case, this can cause 
the nail plate to be pressed into the beams at an inclined angle. 
It is therefore a further object of the invention to provide a 
self-adhesive holding member which resiliently yields to the pressure of 
the press but which has sufficient stability in a lateral direction, to 
ensure that the holding member is not upset. This is achieved in that the 
holding member has a supporting layer of harder material than the 
resilient plastics material. 
It will be seen that in this way the resiliency of the holding member in 
the direction of pressing is not substantially impaired. On the other 
hand, it is no longer possible for the holding member to be upset in a 
lateral direction as the supporting layer can be fixedly connected to the 
holding member and, if a suitable material is selected for use, can 
accommodate relatively high lateral forces, even if the supporting layer 
is only of small thickness. 
The holding member according to the invention may be embodied in a 
particularly advantageous manner if the supporting layer is arranged at 
the surface of the holding member which is opposite the self-adhesive 
contact surface. This arrangement has the advantage that a self-adhesive 
glue coating can be applied on one side of the holding member, and the 
supporting layer on the other side. 
If, in accordance with a further feature of the invention, both surfaces of 
the holding member have a supporting layer, the self-adhesive glue coating 
is applied to one of the two supporting layers. The advantage of this 
arrangement is that the holding member is also stiffened directly at its 
contact surface. 
If the supporting layer is arranged in the interior of the holding member, 
its surface remains soft and rsilient, which nonetheless lateral stability 
can be achieved. 
The holding member may be made in a particularly advantageous manner if the 
supporting layer is made from hard plastics material. Thus it is possible 
for example for the holding members to be arranged on an endless strip and 
rolled up. 
In order to provide a particularly stable holding member, the supporting 
layer is made from metal sheet. Thus, depending on the material selected 
for use, it is possible to make holding members which will remain rigid in 
respect of torsional deformation in the horizontal plane, even when 
subjected to high force components. 
The holding members may be manufactured in a particularly simple and 
rational manner if the supporting layer is made from a hard glue coating. 
In this way for example two layers of soft plastics material can be glued 
together, and the hardened glue coating forms the supporting layer. A 
supporting layer may also be produced by compacting the resilient plastics 
material on at least one side. A compacting effect of this kind may be 
achieved by means of heat or chemicals. The particular advantage of this 
is that virtually no additional materials are required to produce the 
supporting layer and to secure it to the holding member.

As shown in FIG. 1, wood beams 2 are fitted together to form a truss 
structure on a preparation table 1. Displaceable setting plates 4 which 
come to lie below the junctions of the truss structure which are to be 
connected together, are secured on guide rods 3. The wood beams 2 are held 
together by clamps 5 during the pressing operation. 
As generally a multiplicity of trusses having the same configuration are 
made in a working operation, the table 1 only has to be set up once. In 
this respect however it is extremely important for nail plates 5 which are 
disposed below the beams 2 always to lie reliably at the same position, in 
order to avoid repeated adjusting operations and in order to ensure the 
strength of the connection. For this purpose, as shown in FIG. 2, the nail 
plates 6 are positioned by means of holding members 9. The selfadhesive 
holding members 9 are secured by adhesive to the setting plates 4 by being 
simply pressed thereon. They are of approximately the same thickness of 
material as the base plate 7 of the nail plate 6 out of which base plate 
7, the nails 8 are bent upwards. The holding member thus ensure good 
lateral support for the nail plate. The thickness of material may be 
adapted to the specific requirements, according to particular conditions. 
A working operation for producing a truss is as follows, after the working 
table 1 has been prepared: 
Firstly, the nail plates 6 are laid between the holding members 9 which are 
previously positioned correctly by precise measuring. Then, the wood beams 
2 are laid on the nail plates 6 between the jaws of the clamps 5. After 
the wood beams 2 have been fixed by tightening the clamps 5 at the 
junctions, upper nail plates are laid precisely over the lower nail 
plates, as shown in FIG. 3. The working table then rolls in pre-programmed 
steps under a hydraulic surface press 10 where the respective nail plates 
6 which are in the operating region of the press are pressed into the 
beams. When the nails 8 of the nail plates are pressed into the beams, the 
clamps 5 open automatically so that the finished truss can be removed from 
the preparation table. However, the holding members 9 remain adhering to 
the table so that the table 1 is ready for a fresh working operation. 
It will be seen that setting up the table 1 requires the greatest amount of 
time for the first working operation. The precise position of the nail 
plate 6 must first be determined by measuring. The position for the nail 
plate thus established is then fixed by means of the holding members. This 
is effected with the holding members 9 in a very simple manner, insofar as 
the nail plate 6 is held firm with one hand, while with the other hand the 
holding members 9 are butted at at least two positions at the corners of 
the nail plates 6 and secured by adhesive. It will be seen that this 
operation is significantly easier and quicker than screwing in holding 
pins or sticking holding strip members at the side edges of the base plate 
7. 
As shown in FIGS. 4 to 7, the holding members according to the invention 
may be of various shapes. However, the right-angle shape shown in FIG. 4 
has been found particularly advantageous. As the holding members 9 are 
punched out of an endless foam material strip, the material waste to be 
cut off should be as small as possible. This may be achieved in a 
particularly advantageous manner if the holding members 9 are punched out 
of the endless strip in an arrangement in which they are formed like 
arrow-heads and fitted together in a row as shown in FIG. 8 with each 
(except the two end ones in the row) fitted inside one and outside the 
other one of the two adjacent members. Obviously other arrangements of the 
holding members on the web of material are also possible. The endless web 
of material 13 is covered with a protective foil 11, for protecting the 
adhesive underside. The holding members 9 are cut out of the web of 
material with a punching blade in such a way that, in a respective cut, 
the inner edge of one holding member and the outer edge of the next 
following holding member are formed. Thus there are two punch lines 
extending at 45 degree to the side edges of the web to meet on the center 
line of the web at a right angle to one another. The protective foil 11 is 
not severed during the punching operation, so that it takes on the 
function of a carrier strip for the finished holding members. It will be 
seen that the holding members may be easily released by hand from the 
carrier strip, and butted against the base plate. 
The man skilled in the art will not experience any difficulties in 
selecting a suitable material for the holding member. A foam-rubber-like 
foam material has been found particularly suitable. However, other 
materials may also be used, according to the purpose of the holding 
member. However, consideration should be given to the fact that, as shown 
in FIG. 9, the holding members may also be upset in a lateral direction by 
the nail plate 6, by virtue of the soft material used for the holding 
members. This upsetting phenomenon is avoided by a supporting layer which 
is arranged at any desired position on or in the holding member 9. 
Preferably the overall thickness of the supporting layer is less than 
one-third the distance between the parallel faces of the holding member. 
FIG. 10 shows a holding member in which a supporting layer 15 is arranged 
on the surface of the holding member which is remote from the contact 
surface. In order to achieve the greatest possible degree of lateral 
stability, the supporting layer 15 advantageously extends over the entire 
area of the holding member. In certain cases however it is also possible 
for the supporting layer only to extend over the marginal region of the 
holding member, being the region which engages around the nail plate. Each 
holding member is provided at the contact surface with an adhesive coating 
16 with which it can be firmly secured by adhesion to the preparation 
table. 
FIG. 11 shows a holding member with a supporting layer 15 on both sides. It 
is also quite possible for the supporting layer 15 to be arranged in the 
interior of the resilient plastics material 14, as shown in FIG. 12. 
As regards the nature of the supporting layer 15, there are many different 
forms thereof, which fall within the scope of the invention. Thus it is 
possible for example for the supporting layer 15 to be made from a 
relatively hard plastics material. It would also be readily possible 
however, for the supporting layer to be constructed from a suitable metal 
foil. A supporting layer in the interior of the holding member may be 
produced in a relatively simple manner, by glueing together two members of 
soft plastics material. In this specific case, the supporting layer 15 is 
formed by the hardened glue coating. It would also be possible to produce 
a supporting layer of sufficient strength by hardening or compressing the 
surface of the holding member by the action of heat or by suitable 
chemicals. It will be seen that the thickness of the supporting layer must 
be so dimensioned that the holding member can be sufficiently compressed 
in order not to impede the pressing operation.