Panel, in particular a floor panel
The invention relates to a panel, in particular a floor panel, with a core of a wood material
or wood material/plastic mixture, a top side and an underside, wherein the panel has a
profile corresponding to one another on at least two side edges lying opposite one
another, such that two identically embodied panels can be joined and locked to one
another through an essentially vertical joining movement in the horizontal and vertical
direction, the locking in the horizontal direction can be effected by a hook connection
with an upper locking section having a hook element and a lower locking section having
a hook element, the locking in the vertical direction can be effected by at least one spring
element that can be moved in the horizontal direction and during the joining movement
the at least one spring element snaps in behind a locking edge extending essentially in the
horizontal direction.
A panel with a locking in the vertical direction is known, for example, from EP 1 650 375
Al. This type of locking realized with this panel is preferably provided on the transverse
side of floor panels. However, it can also be provided on the long side or on the long side
as well as on the transverse side. The spring element is composed of plastic and is placed
in a groove running horizontally on one of the side edges and chamfered on its top side.
Similar to a door latch, through the chamfer the spring element is pressed inwards into
the groove by the panel to be newly placed, when the underside thereof meets the
chamfer and is lowered further. When the panel to be newly placed is completely lowered
onto the base, the spring element snaps into a groove inserted horizontally in the opposite
side edge and locks the two panels in the vertical direction. Special injection molds are
necessary for the production of this spring element, so that the production is relatively
expensive. Furthermore, a high-quality plastic must be used in order to provide sufficient
strength values, which makes the spring element even more expensive. If plastics are
used with strength values that are too low, this leads to relatively large dimensions of the
spring elements, since only thereby is it ensured that corresponding forces can be
generated or transferred.

Additional expenses result because the locking element is embodied as a separate
component. The production of the locking element is carried out for technological
reasons spatially separately from the panels, so that an integration into the continuous
production process, in particular for floor panels, is likely to be impossible. Through the
different materials, wood material on the one hand and plastic on the other hand, the
adjustment of production tolerances from two separate production processes is complex
and cost-intensive. Since the locking in the vertical direction would be ineffective if the
locking element was missing, in addition this must be secured from falling out of the
groove inserted in the side edge in the further production process and during transport.
This securing is also complex. Alternatively thereto, the locking element could be made
available to the consumer separately.
The floor panels under consideration are being laid with increasing frequency by do-it-
yourselfers, so that, in principle, it is possible due to a lack of experience for the required
number of locking elements to be initially miscalculated and not obtained in sufficient
quantity in order to be able to lay a room completely. Furthermore, it cannot be ruled out
that the do-it-yourselfer upon placing the spring element makes a mistake that means that
precise locking is not possible and the bond separates over time, which is then wrongly
attributed by the consumer to the quality supplied by the manufacturer.
A panel is known from DE 102 24 540 Al, which is profiled on two side edges lying
opposite one another such that hook-shaped connection elements are formed for locking
in the horizontal direction. For locking in the vertical direction, positive engagement
elements spaced apart from one another horizontally and vertically are provided on the
connection elements and undercuts corresponding thereto are provided with respectively
one horizontally aligned locking surface. The transverse extension of horizontally aligned
locking surfaces of this type is approx. 0.05 to 1.0 mm. The dimensioning must be so
small in order for the joining of two panels to remain possible at all. However, this
inevitably means that only low, vertically aligned forces can be absorbed, so that
production must be carried out with extremely low tolerances, in order to ensure that the
connection does not spring open with normal stress in the case of even slight
irregularities in the floor and/or soft subfloors.

The unpublished application DE 10 2007 015 048.4 describes a panel in which the
locking is effected in the vertical direction through a spring element moveable in the
horizbntal direction. With a joining movement, the spring element snaps behind a locking
edge extending essentially in the horizontal direction. The spring element is embodied
from the core through a horizontal and vertical cut and connected to the core on at least
one of its two ends. The horizontal and vertical cut renders possible the spring movement
of the spring element necessary for the production of the locking.
However, this locking is not suitable for thinner panels with a board thickness of approx.
4 mm to 8 mm.
Based on this problem, the panel described at the outset is to be improved.
To solve the problem, a generic panel is characterized in that the at least one spring
element (6) is embodied from the core (3) in one piece and that at least one spring
element is embodied on the lower locking section.
Firstly, the production is considerably simplified through this embodiment. The
adjustment of the tolerances of different components is omitted. Production times and
costs are reduced, because it is not necessary to assemble and join different components.
For the end user, it is furthermore ensured that no components are missing and work
cannot be continued.
Another advantage lies in that due to the laying of the spring element on the lower
locking section, the horizontal slot to expose the spring element from the core is omitted.
The moveable spring element can thus have a greater vertical extension, whereby the
rigidity and strength of the panel connection is improved. Furthermore, the greater
vertical extension of the moveable spring element compared to the board thickness
renders possible a secure connection of thin panels with board thicknesses of approx. 4
mm to 8 mm.
Preferably the at least one spring element is free in the direction of the side edge lying
opposite with respect to the core and connected to the core in the direction of its side
edge on at least one of its ends, in particular at both of its ends. The spring elasticity can
be adjusted through the size of the effective connection of the spring element to the core.

The exposure of the spring element with respect to the core is preferably carried out by
means of an essentially vertical slot. Through the width of the slot the thickness of the
connection of the spring element to the core material can be determined and a stop in the
horizontal direction for the spring element can be created so that this is securely protected
from overextension.
According to the invention, it is provided that the essentially vertical slot is formed at
least in part through the lower locking section. This means that the slot does not need to
be embodied over the entire length as a cutout, but can be embodied at its ends as a gap in
particular in transition areas. The gap in the transition area is expediently opened towards
the underside of the panel and closed towards the top side of the panel. This renders
possible a simple and cost-effective production, because the panel can be moved at a
constant speed over a milling tool and only the penetration depth of the milling tool into
the panel needs to be changed. A transition area can be embodied on one or on both ends
of the spring element. The gap can have a variable depth, for example, a uniformly
increasing depth.
Preferably the essentially vertical slot is embodied in the area of the hook element of the
lower locking section. In the area of the hook element, the locking section expediently
has a maximum vertical extension, so that in this area the spring element can be
embodied with a correspondingly large vertical extension. With increasing vertical
extension of the spring element, the rigidity thereof is also increased.
When a plurality of spring elements spaced apart from one another is provided over the
length of the side edge, the stability of the connection is increased, because the free
spring deflection in the longitudinal direction of the spring element is limited. The
spacing between the individual spring elements can be selected to be larger or smaller.
The smaller the spacing, the greater the effective area with which the locking is carried
out of course, so that the transferable forces in the vertical direction are correspondingly
high.
When the outer edge of the spring element is inclined at an (acute) angle, preferably at an
angle between 40° and 50°, to the top side, the joining movement is facilitated, because
with increasing movement the spring element deflects deeper in the direction of the panel

core. Furthermore, the danger is reduced of the spring element being damaged during the
joining movement.
The hook element on the upper locking section is preferably formed by a shoulder
aligned in the direction of the underside of the panel. The hook element on the lower
locking section is preferably formed by a shoulder aligned in the direction of the top side
of the panel.
The embodiment according to the invention of the spring element is suitable in particular
for thin panels. Thin panels mean those with a board thickness of approx. 4 mm to
approx. 8 mm. Preferably a board thickness of approx. 7 mm or approx. 8 mm is selected.
Exemplary embodiments of the invention are described below with the aid of a drawing.
They show:
Fig. 1 A plan view of two panels connected to one another and
Figs. 2, 3, 4, 5 The two panels from Fig. 1 in partial section at four consecutive times
during a joining movement
Fig. 1 shows two panels 1, 2. The upper section of Fig. 1 shows a section along the line
A-A in the lower section of Fig. 1.
The panels 1, 2 are embodied identically. They comprise a core 3 of wood material or a
wood material/plastic mixture. The panels 1, 2 are profiled on their side edges I, II lying
opposite one another, wherein the side edge I of the underside 4 and the side edge II of
the top side 5 have been machined by milling.
Three spring elements 6 are embodied on the side edge 2. The spring elements 6 are
identical, so that one of the spring elements 6 is described by way of example below.
However, it is not necessary for the tongue elements 6 to be embodied identically.
The spring element 6 was produced by milling out the core 3, in that a slot 7 with ends
7a, 7b running essentially vertically was milled. The side edges I, II have the length L. In
the longitudinal direction of the side edge II, the spring element 6 is connected to the core
material with its ends 6a, 6b. The milling out of the spring element 6 from the core 3 is
carried out exclusively through the slot 7. The outer edge 6c of the spring element 6 is

inclined at an angle a with respect to the top side 5 of the panel 2. The vertical surfaces of
the side edges I, II are machined such that contact surfaces 8, 9 are formed in the area of
the top side 5.
The panel 1 is provided with a groove 10 extending essentially in the horizontal direction
H on the side edge I lying opposite the spring element 6. The groove 10 extends over the
entire length L of the side edge I. However, it would be sufficient to provide grooves 10
of sufficient length only in sections corresponding to the spring elements 6 along the side
edge I. The upper groove cheek 11 of the groove 10 forms an essentially horizontal
locking edge. From the figures it can be seen that the groove base 12 of the groove 10
runs essentially parallel to the outer edge 6c of the spring element 6, which facilitates the
production of the groove 10. However, it could also be embodied in the vertical direction
or at an angle deviating from the angle a.
The locking of the two panels 1, 2 in the horizontal direction is carried out via a step
profiling of hook elements 13, 14 produced by milling. The hook element 13 is part of an
upper locking section 15. The hook element 14 is part of a lower locking section 16.
The hook element 13 has a step-shaped shoulder 17 with two steps 18a, 18b extending in
the direction of the underside. The hook element 14 has a step-shaped shoulder 19 with
two steps 20a, 20b extending in the direction of the top side. The step 18a has an
essentially planar horizontal contact surface 21, which interacts with an essentially planar
horizontal contact surface 22 of the step 20a of the hook element 14. The contact surfaces
21, 22 form an essentially horizontal plane E (Fig. 5) so that the panels 1, 2 connected to
one another are supported on one another.
The profiling of the hook elements 13, 14 is selected such that a prestressing is generated
in the connection point and the vertical contact surfaces 8, 9 of the panels 1, 2 are pressed
onto one another so that no visible gap forms on the top side 5. In order to facilitate the
joining of the panels 1, 2, the step-shaped shoulder 13 of the upper locking section 15 and
the step-shaped shoulder 14 of the upper locking section 16 are milled or rounded on
their edges.
In Fig. 1 six transition areas 23 are discernible. Respectively two transition areas 23 are
arranged on the ends 7a, 7b of a slot 7 and based on the line A-A embodied essentially

with mirror symmetry. In the present example, the transition areas 23 are embodied as
gaps with essentially uniformly decreasing depths (not discernible in the figures). A
transition area 23 thereby has the greatest depth at the end that is facing towards the slot 7
and the smallest depth at the end that is guided in the underside of the panel 2.
A projection 24 of the panel 1 is discernible in Fig. 2. The projection 24 is aligned
essentially horizontally in the direction of the panel 2. The projection 24 has an edge 25
level in sections, which in a lower section runs at an angle  to the top side 5, in a central
section runs essentially perpendicular and in an upper section 26 runs essentially
horizontally. The upper section 26 forms a groove cheek of the groove 10. The projection
24 has in plan view beveled edges 26a (Fig. 1) in order to reduce the danger of damage
during locking of the panels 1, 2.
During the joining movement, the spring element 6 is horizontally displaced in the
direction of the slot 7 by the impact with the projection 24. During this displacement, a
tension builds up in the spring element 6 through the connection with the core 3 at the
ends. The slot width is reduced thereby. This tension allows the spring element to snap in
the last section of the joining movement (Fig. 5) into the groove 10, that means that the
spring element 6 is horizontally displaced in the direction of the groove 10. The
horizontal displacement takes place as elastic recovery into a corresponding position
under the action of an internal tension. The slot width thereby increases again. The
groove 10 is dimensioned such that the spring element 6 can adopt its original position.
The groove 10 is milled somewhat deeper in the core 3 than would be necessary to
accommodate the spring element 6. This facilitates the laying of the panels 1, 2.
The slot 7 has a height of approx. 60% of the board thickness. This makes it possible to
use the locking according to the invention in the vertical direction even with thin panels
with board thicknesses of approx. 4 mm to approx. 8 mm. The locking in the vertical
direction according to the invention, however, can also be advantageously used with
thicker panels, for example, with board thicknesses of approx. 12 mm.
Fig. 5 shows that free spaces 27a, 27b, 27c, 27d are provided with the laid panels 1, 2 in
the area of the side edges I, II. The free spaces 27a, 27b, 27c, 27d provide the freedom of

movement necessary for the laying and counteract any manufacturing tolerances
occurring.
The exposure of the spring element 6 by the vertical slot is rendered possible by a tool
that is transversely displaceable to the machining direction. The machining is thereby
preferably carried out in continuous operation, so that respectively one transition area 23
results at the beginning and at the end of the slot 7.
As tools, a milling tool, a laser tool or a water-jet tool or also upright blades or broaches
can be used. In the exemplary embodiment shown in the Figures, only a displaceable tool
is necessary. The area not exposed, which connects the spring element 6 to the core 3 in
one piece, is reduced during the machining. Locking forces of different strength can also
be adjusted thereby. The locking is releasable with the exemplary embodiment, in that the
panels 1, 2 are displaced relative to one another along the side edges I, II or in that a
release pin (not shown) is inserted laterally into the connection point.

We Claim:
1. Panel, in particular a floor panel, with a core (3) of a wood material or wood
material/plastic mixture, a top side (5) and an underside (4), wherein the panel
(1, 2) has a profile corresponding to one another on at least two side edges (I,
II) lying opposite one another, such that two identically embodied panels (1,
2) can be joined and locked to one another through an essentially vertical
joining movement in the horizontal (H) and vertical (V) direction, the locking
in the horizontal direction (H) can be effected by a hook connection with an
upper locking section (15) having a hook element (13) and a lower locking
section (16) having a hook element (14), the locking in the vertical direction
(V) can be effected by at least one spring element (6) that can be moved in the
horizontal direction (H), during the joining movement the at least one spring
element (6) snaps in behind a locking edge extending essentially in the
horizontal direction (H), characterized in that the at least one spring element
(6) is embodied from the core (3) in one piece, is embodied on the lower
locking section (16), is free in the direction of the side edge (I) lying opposite
by means of an essentially vertical slot (7) with respect to the core (3) and
connected to the core (3) in the direction of its side edge (II) on at least one of
its two ends (6a, 6b), and the essentially vertical slot (7) has transition areas
(23) on its two ends (7a, 7b), on which the essentially vertical slot (7) is not
embodied through the lower locking section (16).
2. Panel according to claim 1, characterized in that the at least one spring
element (6) is connected to the core (3) on one of its two ends (6a, 6b).
3. Panel according to claim 2, characterized in that the essentially vertical slot
(7) is formed at least in part through the lower locking section (16)
4. Panel according to one or more of the preceding claims, characterized in that
the essentially vertical slot (7) is embodied in the area of the hook element
(14) of the lower locking section (16).

5. Panel according to one or more of the preceding claims, characterized in that a
plurality of spring elements (6) spaced apart from one another is provided
over the length (L) of the side edge (II)
6. Panel according to one or more of the preceding claims, characterized in that
the outer edge (25) of the spring element (6) is inclined at an angle (a) with
respect to the top side (5).
7. Panel according to one or more of the preceding claims, characterized in that
the hook element (14) is embodied on the lower locking section (16) through a
shoulder (19) projecting in the direction of the top side (5) and the hook
element (13) is embodied on the upper locking section (15) by a shoulder (17)
aligned in the direction of the underside (4)
8. Panel according to one or more of the preceding claims, characterized in that
the panel (1,2) has a board thickness of approx. 7 mm to approx. 8 mm.

A panel, in particular a floor panel, with a core (3) of a wood material or wood
material/plastic mixture, a top side (5) and an underside (4), wherein the panel (1, 2)
has a profile corresponding to one another on at least two side edges (I, II) lying
opposite one another, such that two identically embodied panels (1,2) can be joined
and locked to one another through an essentially vertical joining movement in the
horizontal (H) and vertical (V) direction, the locking in the horizontal direction (H)
can be effected by a hook connection with an upper locking section (15) having a
hook element (13) and a lower locking section (16) having a hook element (14), the
locking in the vertical direction (V) can be effected by at least one spring element (6)
that can be moved in the horizontal direction (H), during the joining movement the at
least one spring element (6) snaps in behind a locking edge extending essentially in
the horizontal direction (H), can be embodied as a thin panel with a high strength of
the connection, when the at least one spring element (6) is embodied from the core (3)
in one piece and the at least one spring element (6) is embodied on the lower locking
section (16).