Panel, Especially Floor Panel
The invention relates to a panel, especially a floor panel, with a core of wood product or
wood product-plastic mixture, a top and a bottom which is provided with hook elements which
correspond to one another on at least two opposite side edges, the first hook element being formed
by profiling which is essentially open to the top and the second hook element being formed by
profiling which is essentially open to the bottom and which on the first hook element forms a
projection which is pointed essentially toward the top and on the second element a projection
pointed essentially toward the bottom, and at least one of the hook elements being a spring element
which deviates in the horizontal direction in the joining motion and then for purposes of vertical
interlocking snaps in behind an interlocking edge which extends essentially in the horizontal
direction, and at least one of the hook elements being segmented and a plurality of spring elements
spaced parallel forming in this way.
This panel is known for example from DE 10 2007 020 271 A1.
In the panels known from DE 10 2007 015 048 A1 the interlocking element which has an
interlocking surface which extends in the horizontal direction is cut free relative to the core, by
which the interlocking element can execute a deviating motion in the lowering motion. At a small
panel thickness, especially for panels with a thickness of 6 or 7 mm, the stiffness of these
connections is often not sufficient. In conventional tests with steel rolls (DIN 13329) slight vertical
offsets between adjacent panels can arise due to multiple cyclic loading, especially in the region of
the transverse-side interlocking; this becomes immediately apparent with unfavorable light
incidence, by which the floor coating can engender the impression of poor quality.
DE 102 24 540 A1 discloses a floor panel which is bordered in the horizontal plane by atop

which is provided with a decorative layer and a bottom which is provided for support on a subfloor,
which panel is provided with means for detachable connection of at least two panels, on at least one
first side edge the connecting means being made such that interlocking takes place in the transverse
direction and vertical direction, on a second side edge which runs at an angle to the first side edge
interlocking elements being made for interlocking in the vertical direction with other panels. In this
floor panel the interlocking elements are made spaced apart from one another in the transverse
direction and in the vertical direction on two essentially vertically aligned walls which are spaced
apart. So that joining of two panels remains possible, the horizontally aligned interlocking surfaces
can be dimensioned to be very small. The transverse extension is in the range of roughly 0.05 to 1.0
mm. But this necessarily also makes it possible to accommodate small, vertically directed forces so
that fabrication with extremely small tolerances is necessary in order to ensure that the connection
does not snap back under normal loading with slight floor unevenness and/or soft subsurfaces.
DE 101 59 284 A1 discloses a floor panel with a core of wood product which has a groove
which forms an upper lip and a lower lip on at least one side edge over its length and on the
opposite side edge is made with a tongue which corresponds to the groove. For interlocking of
panels which are connected to one another the tongue is provided with at least one projection, and
the groove has at least one depression on the lip which is opposite at least one projection. Here the
depression is longer than the projection, and the lip provided with the depression on the side edge
has at least one recess which extends as far as the depression, the length of the recess being at least
as large as the length of the projection. Relative to the lengthwise direction the recesses and the
projection are offset to one another. The connection of two panels takes place by this configuration
in the manner of a quarter-turn fastener by first of all a joining movement which points in the

transverse direction of the panel being carried out so that the tongue is inserted into the groove and
then the interlocking of the two panels takes place in the manner of a quarter-turn fastener by a
movement pointed in the lengthwise direction.
This profiling of the side edges is mechanically very complex and installation of the panels
becomes in part more complicated since it must be ensured that the tongues are plunged into the
grooves over the full length of the side edges. If then the concluding interlocking motion is not
carried out completely parallel to the lengthwise axis of the panel, there is the danger that the panel
to be interlocked will be tilted and will swivel the tongue out of the groove so that interlocking is no
longer possible.
DE 198 23 357 A1 discloses a wall tile with an essentially flat, cuboidal base body which
has a visible surface, a fastening surface and face surfaces which connect the visible surface to the
attachment surface. On at least one of the face sides there is a spacer which is integrated with the
tile and which comprises means for compensation of the thermal elongation of the tile. These
spacers are profiled in a hook shape so that two tiles can be connected to one another by way of a
vertical lowering motion.
DE 200 08 708 U1 discloses panels with side edges which are profiled in a hook shape and
which can be connected positively to one another by a vertical lowering motion.
WO 2008/116623 A1 discloses floor panels which on at least two opposite side edges have
profiling corresponding to one another such that two identically made panels can be connected and
interlocked with one another by an essentially vertical joining movement in the horizontal and
vertical direction. The interlocking in the vertical direction is caused by a spring element which can
be moved in the horizontal direction and which snaps in behind an interlocking edge which extends

essentially in the horizontal direction in the joining motion. This spring element is formed integrally
out of the core.
Proceeding from this problem formulation, the initially described panel is to be improved
such that profiling of the hook elements is improved such that larger interlocking surfaces can be
implemented and thus reliable interlocking is ensured.
To solve the problem a generic panel is characterized in that spring elements are arranged
running obliquely at an angle to the longitudinal axis.
This interlocking is especially suited for the transverse side of the panels to be connected to
one another. The hook elements on the opposite side edges extend behind one another and thus
interlock two panels in the horizontal and in the vertical direction. The elastically deflectable
projections of the hook elements are displaced by the segmenting and in the end position of the
panels snap again into their initial position, by which vertical interlocking takes place. Because the
tongue elements run at an angle to the side edge (lengthwise axis), it becomes possible for the
respective bottom hook element to deviate down and at the same time laterally in the connection of
two panels. This yields more space in order to allow the upper hook element to pass. The
interlocking surface becomes larger due to the oblique surface; this allows the interlocking to
become more reliable.
Preferably the two projections have an undercut and each undercut has an interlocking edge
which extends essentially in the horizontal direction.
When the spring elements are made on the hook element which is open toward the top,
installation of the panels is simplified because the lowering motion of the profile which is to be
newly installed is made more uniform.

When the bottoms of the spring elements are bevelled at least in the region of the projection
on the bottom at an angle β relative to the horizontal, enough deviation space is made available for
the spring element to be able to execute a pivoting motion during interlocking.
The deviation motion of the spring elements is composed of several movements. Mainly the
spring elements are displaced by the upper projection in the direction of the longitudinal axis of the
panel. The spring elements can however also deviate in the transverse direction of the panel due to
the slots which run obliquely to the longitudinal axis. The bending stiffness of the spring elements
in the transverse direction is defined mainly by their width. The horizontal deflection of the
projection which is caused by the interlocking force in the transverse direction leads to a widening
of the groove so that the undercut of one projection extends behind the undercut of the other
projection. The deviation movements of the spring element can be superimposed by rotation around
an axis which runs in the transverse direction if the spring element has enough space downward for
deviating.
The angle β is preferably less than or equal to 10°.
The spring elements are preferably regularly spaced toward one another.
The method for connecting and interlocking two panels designed as claimed in the
invention proceeds by the panel to be joined with the hook element which is open to the bottom
being pivoted around a nearby pivoting axis which is parallel to the longitudinal side into the panel
which lies on the floor into the hook element which is open toward the top, and in doing so the
projection of the hook element which is open toward the bottom grasping the projections of the
spring elements next to one another and bending out elastically so that this deviating and each
projection of the spring element springs back [sic] when the undercut formed in it overlaps the in

the projection of the hook element which is open to the bottom [sic], the deviating motion of the
spring elements being divided into the following three movements:
a) displacement of the projection in the direction of the longitudinal axis of the panel,
b) deviation of the projection in the transverse direction of the panel,
c) widening of the groove which is open to the top and which is made between the
projection and the side edge.
The widening of the groove can be superimposed by a pivoting motion of the projection
around an axis which runs parallel to the transverse side of the panel.
Exemplary embodiments of the invention will be detailed below using the drawings.
Figure 1 shows a perspective of two panels during the connection process;
Figures 2a to 2d show individual steps of the interlocking;
Figure 3 shows a partial plan view of one panel;
Figure 4 shows a side view according to the visible arrow IV as shown in Figure 3;
Figure 5 shows the plan view of the panel in the interlocking position as shown in Figure
2c;
Figure 6 shows a view of the panel according to visible arrow VI as shown in Figure 5;
Figure 7 shows a partial perspective of another embodiment of a panel;
Figure 8 shows a perspective of two panels during the connection process in another
embodiment.
Panels 1,2 are made identically. They consist of a core 17 of wood product or a wood-
product-plastic mixture. The longitudinal side of one panel is generally longer than its transverse
side. In the drawings the panels 1,2 are shown at the connection site of their transverse side. On

their opposite side edges I, II the panels 1,2 are profiled, the side edge I having been milled from
the top 18 and the side edge II from the bottom 19. In this way two hook elements 4,6 which
correspond to one another are formed, the hook element 4 comprising a projection 5 pointed toward
the top 18 and the hook element 6 comprising a projection 7 pointed toward the bottom 19. Both
hook elements 4, 6 are provided with undercuts 8, 9. The undercut 8 is formed by an interlocking
element 3 which projects laterally from the projection 7 in the direction of the core 17. The
undercuts 8, 9 each have one interlocking edge 10,11 which extends essentially in the horizontal
direction. As can be taken from the figures, the interlocking edges 10, 11 can run at an angle to the
horizontal H. Their interlocking action is however pointed in the vertical direction V so that the
interlocking edges nevertheless run essentially in the horizontal direction.
The hook element 4 is made elastic and is segmented so that individual spring elements 4
form which are spaced regularly to one another. The elasticity of the spring elements 4 is dictated
on the other hand by the thin lower lip 12 which projects from the side edge I to the outside and on
its outer end being adjoined by the projection 5, and on the other hand by slots 13 which are made
at an angle a in the vertical direction V continuously through the hook element 4 at regular
intervals. Each spring element 4 is therefore connected to the core 17 of the panel 1 only on one
side. In the region of the projection 5 the lower lip 12 runs at an angle β relative to the horizontal.
As Figure 7 shows, the interlocking element 3 can be segmented so that a plurality of
interlocking elements 3 spaced parallel is established. In order to be able to set the vertical offset of
two panels which are connected to one another independently of the interlocking function, in the
exemplary embodiment of the panels 1,2 shown in Figure 8 there is one horizontal contact surface
20,21 each.

Figures 1 and 2a to 2d illustrate the interlocking process. On the longitudinal side which is
not shown here the panels 1,2 are provided with profiling with which it is possible to insert a panel
2 which is to be newly installed at an angle into the longitudinal side of a panel which is already
lying on the floor and then to bend it for connecting/interlocking of the longitudinal side onto the
subfloor. This profile is disclosed for example in DE 102 24 540 Al, to whose contents reference is
made in full. On the transverse side - the short side of a panel 1,2- there is the profiling as claimed
in the invention. The panel 2 which is to be newly installed is linked to the longitudinal side of a
panel which is already lying on the floor and with one side edge 2 is placed tightly against a panel 1
which is likewise already connected on its longitudinal side to an already installed panel. Upon
pivoting down, the projection 7 with its bevelled bottom 14 comes into contact with the bevelled
top 15 of the projection 5 (Figure 2a), by which the projection 5 first deviates in the transverse
direction Q so that the groove 12 which forms between the side edge I and the projection 5 is
widened. Because each individual spring element 4 is exposed by the slot which runs obliquely at
an angle a relative to the core 17 in the longitudinal direction L of the panel 1, the hook element 5
upon a further lowering motion of the panel 2 can also deviate in the longitudinal direction L of the
panel 1. At the same time a pivoting motion of the projection 5 takes place around a pivoting axis S
which runs parallel to the longitudinal direction L of the panel 1. To enable this pivoting motion,
the lower lip 12 at least in the region of the projection 5 is bevelled at an angle β. The pivoting
motion is continued until the lower lip 12 in this region rests on the subfloor, by which a further
pivoting motion is prevented (compare Figure 2c). As the panel 2 continues to be lowered the
undercuts 8, 9 overlap one another. The projection 5 springs elastically back around the pivoting
axis S and the hook elements 4, 6 hook into one another, the interlocking surfaces 10, 11 lying on

one another. The panels 1,2 which are interlocked with one another tightly adjoin one another in
the upper region of the side edges I, II. As Figure 2d shows, the surfaces 15,16 of the projection 5
do not have any contact with the panel 2.
The aforementioned described profile connection has the advantage that it is machined in
one piece out of the core material, does not require any outside parts and thus fewer production
tolerances need be maintained than otherwise. As a result of the higher stiffness, several forces can
be transferred in the vertical direction. The profiling is also suitable for thin panels and tools which
can move only on one side, preferably plunge cutters, are necessary for production. Production
takes place essentially as described in DE 10 2007 015 048 A1. For producing the undercuts 8,9
the hook elements 4, 5 are machined by means of a vertical tool which is not shown. The slots 13
which run obliquely to the longitudinal axis L of the panel are produced by cutting tools which
plunge into the core 17 in the vertical direction V while the panel 1 is moving past the machining
station (not shown). Since the plunging cutting tools are oblique to the transport direction, they
must be ground such that they cut both in the direction of plunging and also in the transport
direction of the panel 1. This yields a so-called draw-cut.

Reference Number List
1 panel
2 panel
3 interlocking element
4 hook element/spring element
5 projection
6 hook element
7 projection
8 undercut
9 undercut
10 interlocking surface
11 interlocking surface
12 lower lip
13 gap/slot
14 groove
15 surface
16 surface
17 core
18 top
19 bottom
20 joining edge
21 joining edge

I side edge
II side edge
α angle
β angle
L longitudinal direction of the panel
Q transverse direction of the panel
V vertical direction

WE CLAIM
1. Panel, especially a floor panel (1,2), with a core (17) of wood product or wood product-
plastic mixture, a top (18) and a bottom (19), which panel is provided with hook elements (4,6)
which correspond to one another on at least two opposite side edges (I, II), the first hook element
(4) being formed by profiling which is essentially open to the top (18) and the second hook element
(6) being formed by profiling which is essentially open to the bottom (19) and which on the first
hook element (4) forms a projection (5) which is pointed essentially toward the top (18) and on the
second hook element (6) a projection (7) pointed essentially toward the bottom (19),
and two identically made panels can be connected and interlocked to one another in the horizontal
(H) and vertical (V) direction by an essentially vertical joining motion, and at least one of the
projections (5, 7) deviating in the joining motion in the horizontal direction (H) and then for
purposes of vertical interlocking snapping in behind an interlocking edge (10) which extends
essentially in the horizontal direction (H), and at least one of the hook elements (4) being
segmented and a plurality of spring elements (4) spaced parallel forming in this way, characterized
in that the spring elements (4) are arranged running obliquely at an angle (a) to the longitudinal axis
(L).
2. Panel as claimed in Claim 1, wherein the two projections (5,7) have an undercut (8,9)
and each undercut (8, 9) has an interlocking edge (10,11) which extends essentially in the
horizontal direction (H).
3. Panel as claimed in Claim 1 or 2, wherein the hook element (4) which forms the tongue
elements is the hook element (4) which is open toward the top.

4. Panel as claimed in one of Claims 1 to 3, wherein the bottom of the spring element (4) is
bevelled at least in the region of the projection (5) at an angle (β) relative to the horizontal (H).
5. Panel as claimed in Claim 4, wherein the angle (β) = 10°.
6. Panel as claimed in one or more of the preceding claims, wherein the spring elements (4)
are spaced regularly to one another.
7. Method for connecting and interlocking of two panels (1,2) as claimed in one of the
preceding claims, in which the panel (2) to be joined with the hook element (6) which is open to the
bottom is pivoted around a nearby pivoting axis which is parallel to the longitudinal side and in
doing so the hook element (6) which is open toward the bottom (19) is continuously and in
succession pivoted into the hook elements (4) of the panel (1) which lies on the floor, which hook
elements are open toward the top (18), and in doing so the projection (7) grasps the projections (5)
of the spring elements (4) in succession next to one another and bends them out elastically, and
each projection (5) of each spring element (4) springs back when the undercut (9) formed in it
overlaps the one in the projection (7), the deviating motion of the spring elements (5) being divided
into the following three movements:

a) displacement of the projection (5) in the transverse direction (Q) of the panel (1),
b) deviation of the projection (5) in the longitudinal direction (L) of the panel (1),
c) widening of the groove (14) which is open to the top and which is made between the
projection (5) and the side edge (1).
8. Method as claimed in Claim 7, wherein the widening of the groove (14) is superimposed
by a pivoting motion of the projection (5) around a pivoting axis (S) which points in the
longitudinal direction (L).

A panel, especially floor panel (1,2) comprises a core (17) produced of a
wood product or a mixture of a wood product/synthetic material, a top
(18) and a bottom (19), and is provided with mating hook elements (4,6)
on at least two opposite lateral edges (I, II) thereof, the first hook
element (4) being formed by a profiled section which is essentially open
to the top and the second hook element (6) being formed by a profiled
section which is essentially open to the bottom (19). The profiled section
on the first hook element (4) forms a projection (5) which is essentially
facing the top (18) and on the second hook element (6) forms a
projection (7) which is essentially open to the bottom (19). Two identical
panels can be interconnected and interlocked by an essentially vertical
joining movement in the horizontal (H) and the vertical (V) direction.
At least one of the projections (5, 7) is deviated during the joining
movement in the horizontal direction (H) and then snaps into a locking
edge (10) which extends essentially in the horizontal direction (H) to
vertically lock the panels. At least one of the hook elements (4) has a
segmented design, thereby forming a plurality of parallel interspaced
spring elements (4). The panel according to the invention is
characterized in that the spring elements (4) are diagonally arranged at
an angle (α) to the longitudinal axis (L).