DE202012007765U1 - Dovetail joint and packing box with a dovetail joint - Google Patents

Abstract

Dovetail connection between two wooden panels (1, 2), wherein the end face (3) of a first plate (1) to form a joint line (4) perpendicular to the broad side (5) of the second plate (2) abuts, with at least one dovetail (6) on one of the plates (1) and at least one slot (7) for receiving the dovetail pin (6) on the other plate (2), characterized in that the dovetail pin (6) is tapered on the one plate (6). 1) is formed to taper pin, that the slot (7) with a Zapfeneinführloch (9) and a subsequent pin clamping hole (10) is formed, wherein the pin clamping hole (10) is formed conically corresponding to the dovetail pin (6), wherein the Dovetail connection for inserting the dovetail pin (6) perpendicular to the broad side (5) into the pin insertion hole (9) and for telescoping the dovetail pin (6) and the pin clamping hole (10) is formed parallel to the joint line (4).

Description

The invention relates to a dovetail joint between two wooden panels, wherein the end face of a first plate abuts perpendicularly to the broad side of the second plate to form a joint line, with at least one dovetail on one of the plates and at least one slot for receiving the dovetail on the other plate , according to the preamble of claim 1.

The invention furthermore relates to a cuboidal packaging box which can be assembled from individual wood panels, with a base plate, with first and second side plates perpendicularly projecting from the base plate and with a cover plate, wherein a cuboid receiving space for packaging material is formed by the base plate and the side plates, according to the preamble of claim 8.

It is the object of the present invention to improve a dovetail joint of the known type, so that a positive and thereby flush dovetail connection without protruding parts is formed, with high pull-out force on the dovetail, and this simply put together and also released again can, without the need for tools.

It is another object of the invention to improve a packaging box of the known type so that it can be easily assembled and disassembled without tools at the site of the package.

The object is achieved with respect to the dovetail connection by a dovetail connection with the features of claim 1.

The object is achieved with respect to the packaging box by a packaging box with the features of claim 8.

Thus, according to the invention, the dovetail pin is formed as a pin tapering conically onto the one plate, the slot being formed with a pin insertion hole and a pin pinch hole thereafter, the pin pinch hole being tapered corresponding to the dovetail pin, the dovetail pin connection for insertion of the dovetail pin is formed perpendicular to the broad side in the Zapfeneinführloch and for telescoping the dovetail pin and the pin clamping hole parallel to the joint line.

Thus, it is possible to produce a locally closely localized butt joint by means of a dovetail joint, without a further displacement of the dovetail pin is required. At the desired location of the butt joint, the dovetail pin can be inserted perpendicular to the broad side of the plate to be joined in the zapfeneinführloch. A shift by a short distance, perpendicular to the insertion direction, spends the dovetail pin in the area of the clamping hole. There, a negative corresponding cone shape is present, in which the conically shaped dovetail pin is pushed in and a firm clamping connection of the dovetail pin is effected in the clamping hole, which is just as easily solvable again. The dovetail connection according to the invention is not only fixed, but it also almost automatically creates a right angle between the two plates to be joined together.

A dovetail joint according to the invention is designed as a plug connection with subsequent jamming perpendicular to the plugging direction.

The inventive design of the dovetail joint opens up a number of advantageous design options. For example, the clamping hole may be dimensioned so that the dovetail pin does not project beyond the open side of the clamping hole. In this case, the dovetail connection according to the invention is characterized by a high pull-out force in the direction of impact, but a low release force in the direction of the abutting edge, so that a flush, non-positive, releasable connection is formed without protruding parts.

According to an advantageous embodiment of the invention, the dovetail pin are formed on the end face of the first plate and the slot for receiving the dovetail pin on the broad side of the second plate.

According to an advantageous embodiment of the invention, the dovetail pin is formed as a cantilever with a conical undercut on the narrow and broad sides. The advantage of a cantilever is that it prevents a mutual twisting of the two connected plates.

According to an advantageous embodiment of the invention, the dovetail pin is provided with a vertically extending from the free end side extending slot, so that two resiliently spreadable pin arms are formed. As a result, the pull-out force of the dovetail can be additionally increased. It can also after the dovetail connection has been made, a wedge is driven into the slot, which additionally drives the two arms apart, thereby further consolidating the jamming of the slot and the pin.

According to an advantageous embodiment of the invention, the slot is a through hole. The through hole may in particular be dimensioned so that the dovetail pin after insertion into the slot on the other side of the slot does not protrude, so that a flush, non-positive, releasable connection is formed without protruding parts.

According to an advantageous embodiment of the invention, the slot is a blind hole.

According to an advantageous embodiment of the invention, the slot has two peg clamping holes arranged one behind the other in the dashed line direction, between which the pin insertion hole is arranged. In this way, a dovetail joint in two displacement directions can be produced.

A packaging box according to the invention is characterized in that the first side panels form the opposite broad sides of the box and the second side panels form the opposite narrow sides of the box and that a plurality of dovetail pin connections according to the invention are formed as described above for connecting a respective second side panel to the two first side panels , Such a packaging box according to the invention can be constructed very easily, without additional tools, by a person without auxiliary persons, at the place of packaging and, if necessary, also be dismantled again because of the dovetail connections used according to the invention. Because to assemble the side plates to push only one side plate with its narrow side in the place of the dovetail connection, more precisely at the location of the pin insertion holes or be brought to the broad side of the other plate, dovetail and Schwalbenschwanzeinführloch be merged at the location of the shock, and a short displacement perpendicular to the impact direction conveys the dovetail pin in the pin clamping hole, whereby the two plates are flush, positive and connected with high pull-out force in the direction of impact. Another advantage is that the two plates are automatically connected at right angles to each other and a rotation of the plates is avoided against each other. The right angle adjusts itself automatically, since the conical profiles of the dovetail pin and the clamping hole complement each other in a negatively corresponding manner.

According to an advantageous embodiment of the invention, the second side plates are attached with their broad side to the end faces of the first side plates, and at the end faces of the first side plates are a plurality of dovetails and on the broad sides of the second side plates are in corresponding to the dovetail pin a plurality of slots for receiving the dovetail and to form a plurality of inventive dovetail connections as described above. For example, four or five dovetail connections according to the invention may be arranged at the same distance on the narrow side of the one plate. Thus, only the relatively short displacement path of the dovetail pin from the Zapfeneinführloch in the clamping hole is always required, which reduces the effort when making the connection, and yet a stable connection over the entire length of the abutting edge is guaranteed. Both plates are put together in a sense and jammed by a short displacement perpendicular to the direction of insertion.

According to an advantageous embodiment of the invention, the first side plates are attached with their broad side to corresponding end faces of the bottom plate, and at these end faces of the bottom plate are a plurality of dovetail and on the broad sides of the first side plates are in corresponding to this dovetail pin a plurality of slots for receiving the dovetail and to form a plurality of dovetail joints according to the invention as described above. Thus, the assembly of the packaging box according to the invention can be further simplified. First, the two first side plates are thus attached to the bottom plate and fastened. This can, as described above, be carried out very easily and without tools by one person. The side panels are then already stable and attached at right angles to the bottom plate. Now the second side plates are attached to the first side plates and fastened. The packaging room of the box is now ready. Subsequently, only the lid is placed. A further advantageous procedure is that first the packaged product is placed on the bottom plate and then only the side walls, so to speak around the packaged goods, are added. The packaging box according to the invention can therefore be built around a packaged goods around. This is particularly advantageous for bulky packaging goods, such as large machine parts. These then no longer have to be lifted into a prefabricated box, but they can be easily pushed onto the base plate, and only then The box is created by attaching the side walls and the lid.

A packaging box according to the invention forms a stable and high-precision unit, firmly connected by form-fitting dovetail pin connections, designed as a plug-in system without further components. A wide range of dimensions and thicknesses is possible. For example, plywood can be used in standardized material thicknesses of 12 mm for the side parts and 21 mm for the bottom plate, but also all other material thicknesses can be processed into a packaging box according to the invention.

The invention describes a universally usable transport packaging, suitable for the European and / or worldwide shipping of packaging goods, especially bulky packaging goods such as large machine parts. It ensures an uncomplicated filling and removal of the packaged goods, since the box walls can be used after insertion of the packaged goods on the bottom plate.

In a disassembled state, a packaging box according to the invention occupies a very small volume. The bottom plate, the side walls and the top plate are simply laid flat on top of each other. Since - apart from feet, see below - no perpendicular to a broadside protruding parts are present, the box is flat when disassembled and easy to transport. In the place where it is needed, then a tool-free one-man assembly is possible within a very short time. Because of the dovetail connection according to the invention, the stability of the packaging box without nails, staples or similar fasteners is given.

According to an advantageous embodiment of the invention, anti-slip devices are mounted on the cover plate in order to avoid slipping when stacked packaging boxes.

According to an advantageous embodiment of the invention projecting feet are formed with plastic glides on the bottom plate.

According to an advantageous embodiment of the invention, the anti-slip devices are designed as recesses in the cover plate which correspond negatively to the pedestals with the plastic glides.

The feet meet the transport of a ready assembled and filled transport box according to the invention the function of a pallet, without having their disadvantages. So no cross boards are available, so the box can be bundled longitudinally or transversely, and it is a trouble under driving the box with forklift or Hubwagengabeln possible, both longitudinally and transversely.

The cover plate can be fixed by means of a Kunststoffbänderbandreifung. The bands are then advantageously close and directly to the side plates and the bottom plate. This also supports the problem-free driving under the box with forklift or pallet forks.

The plastic glides under the feet ensure against slipping and protect coated industrial floors when the box is parked there.

As a further advantageous embodiment, ergonomically designed recessed grips can be introduced in the side walls, which provide a secure hold for the assembly person when handling the side parts during assembly.

Reference to the drawings, in which three embodiments of the invention are shown, the invention and further advantageous embodiments and improvements of the invention will be explained and described in detail.

Show it:

1 a dovetail joint according to the invention

2a FIG. 3: a longitudinal section through a dovetail pin according to the invention, FIG.

2 B : A plan view of a slot according to the invention, left without and right with inserted pin,

2c : a plan view of another slot according to the invention, right without and left with inserted pin,

3 : an exploded view of a packaging box according to the invention,

4 FIG. 2: a detailed view of an assembled packaging box according to the invention, FIG.

5 a packaging box according to the invention, filled and partially assembled,

6 : a packaging box according to the invention, disassembled,

7 FIG. 2: an exploded view of a packaging box according to the invention in a further embodiment, FIG.

8th : A packaging box according to the invention in a third embodiment

It will be first 1 considered. 1 shows a dovetail joint between two wooden panels 1 . 2 , The front side 3 the first plate 2 is supposed to be under formation of a joint line 4 , formed by the edge of the front side 3 , perpendicular to the broadside 5 the second plate 2 bump. On the one plate 1 is a dovetail 6 educated. At the other plate 2 is a slot 7 for receiving the dovetail pin 6 educated.

The swallowtail thong 6 is as a cantilever with conical undercut 8th (please refer 2a ) on its narrow and broad sides, so as to be conical on the plate 1 formed to taper pin. The slot 7 is with a pin insertion hole 9 and an upwardly subsequent pin clamping hole 10 educated.

Like the 2 B shows is the pin clamping hole 10 conically corresponding to the dovetail 6 educated. The dovetail joint is for inserting the dovetail pin 6 perpendicular to the broadside 5 in the pin insertion hole 9 and for telescoping the dovetail pin and the pin clamping hole 10 parallel to the joint line 4 educated. The swallowtail thong 6 gets into the pin insertion hole 9 inserted and then upwards by a short distance, such as the longitudinal extension of the dovetail pin 6 accordingly, in the pin clamping hole 10 moved in and there because of the inverse conical contour of the pin clamping hole 10 jammed.

2a shows in longitudinal section the dovetail pin 6 , This has perpendicular from the free end face 11 starting in the pin 6 in extending slot 12 , which can also be referred to as a gap or slit slot. Through the slot 12 are on the journal 6 two resiliently spreadable journal arms 13 . 14 educated.

2 B shows a plan view of a slot according to the invention 7 , left without and right with inserted pin 6 , It can be seen on the left in the area of the pin clamping hole 10 the cone contour 15 inversely corresponding to the conical undercut 8th of the pin 6 is trained. In the illustration after 2 B right is the pin 6 pushed into the pin clamping hole. The two pin arms 13 . 14 be through the inverse cone contour 15 in cooperation with the conical undercut 8th pressed together. The resulting recovering spring force of the two pin arms 13 . 14 increases the contact pressure and thus the retention force of the pin 6 in the clamping hole 10 ,

2c shows a plan view of another slot according to the invention 7 ' , left without and right with inserted pin. The slot 7 ' has two peg clamping holes arranged one behind the other in the dash line direction 10 ' . 10 '' between which the pin insertion hole 9 ' is arranged. In this way, a dovetail joint can be made in two displacement directions, either up or down, from the pin insertion hole 7 ' out.

The slot 7 . 7 ' in the 2 B and 2 B is formed as a through hole. The height of the conical undercut 8th on the dovetail pin 6 is sized so that the free end face 11 flush with the outside of the wood panel 2 completes when the dovetail joint is made. So it's nothing over. Of course, the slot could also be formed as a blind hole.

The 3 shows in an exploded view of a composite of individual wood panels, cuboid packaging box 16 , This has a bottom plate 17 , from the vertical two first side plates 1' . 1' and two second side plates 2 ' . 2 '' protrude. Completed to the top. is the packaging box 16 with a cover plate 18 , passing through the bottom plate 17 and the side plates 1' . 1'' . 2 ' . 2 '' a cuboid receiving space for packaged goods 19 (please refer 5 ) is formed. The first side plates 1' . 1'' form the opposite broad sides of the box, and the second side panels 2 ' . 2 '' form the opposite narrow sides of the box.

To connect each a second side plate 2 ' . 2 '' with the first two side plates 1' . 1'' are several dovetail connections, as described above, between the end faces 3 ' . 3 '' the first side plates 1' . 1'' and the edges of the broadsides 5 ' . 5 '' educated. These are located on the front pages 3 ' . 3 '' the first side plates 1' . 1'' four dovetail pegs each 6 ' , and at the edges of the broadsides 5 ' . 5 '' are each the pin 6 ' opposite four slots 7a ,

The first side plates 1' . 1'' are at the bottom of their broadside 23 . 23 ' to corresponding end faces 24 . 24 ' the bottom plate 17 stated. At these ends 24 . 24 ' the bottom plate 17 are several dovetails, and on the broadsides 23 . 23 ' the first side plates 1' . 1'' are in to these dovetails corresponding position a plurality of slots for receiving the dovetail and for forming a plurality of dovetail connections, as described, formed.

To assemble the packaging box so be to the bottom plate 17 the first two side plates 1' . 1'' infected and attached. This can, as described above, be carried out very easily and without tools by one person. The side plates 1' . 1'' are then already stable and at right angles to the bottom plate 17 attached. Now the second side plates 2 ' . 2 '' to the first side plates 1' . 1'' infected and attached. The packaging room of the box is now ready. The second side plates 2 ' . 2 '' do not need the bottom plate 17 to be attached, this is done indirectly via the attachment to the first side panels 1' . 1'' that yes at the bottom plate 17 are attached.

Subsequently, only the lid 18 placed. The cover plate 18 can by means of a Kunststoffbänderbreifung 25 , please refer 4 to be attached. The bands 25 lie close and directly on the side plates 1' . 2 ' and the bottom plate 17 at. This supports the trouble-free driving under the box with forklift or pallet forks.

At the bottom plate 17 are protruding feet 20 , formed as cuboid blocks with plastic glides 21 , are formed, here they are screwed.

On the outside of the cover plate 18 are slips in the form of to the feet 20 with the plastic glides 21 negative corresponding depressions 22 educated. If two packaging boxes are stacked on top of each other, the plastic gliders will fit 21 the top box in the wells 22 the lower box, which prevents slipping of the upper box on the lower box.

4 shows in a detail view obliquely from below details of a composite packaging box according to the invention. One recognizes how the first side plate 1' at the bottom plate 17 is fastened by means of a dovetail pin connection according to the invention, wherein the dovetail pin 6 ' at the front of the bottom plate 17 and the slot 7a with the pin insertion hole 9 ' at the first side plate 1' are formed. The second side plate 2 ' is at the first side plate 1' attached. by means of a dovetail pin connection according to the invention, wherein the dovetail pin 6 at the front of the first side panel 1' and the slot 7 with the pin insertion hole 9 on the second side plate 2 ' are formed. You can also see the feet 20 with plastic glides 2 , as well as the plastic strapping 25 ,

A packaging box designed in accordance with the invention also makes it possible, as it were, to build the box around the packaging material at the location of the packaging. 5 shows an intermediate step in such an approach. A bulky packaging 19 , here a large machine part, such as a shock absorber, is on the bottom plate 17 put on and there by a support structure 26 held. Now the back of the first two side plates 1'' already with a Schwalbenschwanzzapfenverbindung invention at the rear end side of the bottom plate 17 attached and fixed by moving. You can see that between the bottom plate 17 and the side wall 1'' due to the construction of the dovetail pin as a longitudinally extending cantilever a vertical angle is set almost automatically. Now, the packaging box would be further completed by successively attaching the front of the first side panels, the second side panels and the top panel.

In connection with 4 Be also on the ergonomically designed recessed grip 27 at the top of the side plate 1'' referenced, which is present in such or a similar manner on all side plates and the handling of the side plates when assembling and disassembling the packaging box much easier.

It will now be the 7 considered. This shows a further embodiment of a packaging box according to the invention 16a , Identical or equivalent parts are denoted by the same reference numerals as in the 1 to 5 used. The difference from the previously described embodiment according to the 1 to 5 is that on the feet 20a no plastic glides are attached, and that the anti-slip device on the cover plate 18a through screwed flat wooden strips 28 . 28a are formed. Every bar 28 . 28a has two comb-like webs 29 . 29 ' so that in total each bar has three recesses 30 . 30 ' . 30 '' are formed. When stacking two packaging boxes 16a grab the feet 20a the upper packaging box in these recesses of the lower packaging box, which prevents slipping of the upper box on the lower box is avoided.

The 6 shows the packaging box 7 in disassembled condition. The bottom plate 17 , the side walls 1' . 1'' . 2 ' . 2 '' and the cover plate 18a are laid flat on top of each other. This is a packaging box according to the invention in disassembled state very space efficient and easy to transport. Although the simple disassembly and transport of the packaging box is according to the embodiment of a packaging box after 7 shown. Of course, the packaging boxes according to one of the other embodiments, according to 1 to 5 or 8th , see below, just as easily disassembled and transported.

It will now be the 8th considered. This shows a further embodiment of a packaging box according to the invention 16b , Identical or equivalent parts are denoted by the same reference numerals as in the 1 to 5 used. The difference from the previously described embodiment according to the 1 to 5 is that on the bottom plate instead of feet three crossbeams 31 . 31 ' . 31 '' are formed, and that the anti-slip on the cover plate 18b through screwed flat wooden strips 32 . 32a are formed. Every bar 32 . 32a has two comb-like webs 33 . 33 ' so that in total each bar has three recesses 34 . 34 ' . 34 '' are formed. When stacking two packaging boxes 16b grab the crossbeams 31 . 31 ' . 31 '' the top packaging box in the recesses 34 . 34 ' . 34 '' the lower packaging box, which prevents slipping of the upper box on the lower box is avoided.

LIST OF REFERENCE NUMBERS

1, 1 ', 1' '

wood panel

2, 2 ', 2' '

wood panel

3, 3 ', 3' '

front

4

surge line

5, 5 ', 5' '

broadside

6, 6 '

male dovetail

7, 7a

slot

7 '

slot

8th

Conical undercut

9, 9 '

Zapfeneinführloch

10, 10 ', 10' '

Zapf clamp hole

11

Free frontage

12

slot

13

bolt arm

14

bolt arm

15

cone shape

16, 16a, 16b

packing case

17

baseplate

18, 18a, 18b

cover plate

19

packaged goods

20

stand

21

Plastic glides

22

deepening

23, 23 '

Broad side of the first plate

24, 24 '

Front side of the bottom plate

25

Plastic tape

26

support structure

27

grip

28, 28a

strip

29, 29 '

web

30, 30 ', 30' '

recess

31, 31 ', 31' '

crossbeam

32, 32a

strip

33, 33 '

web

34, 34 ', 34 "

recess

Claims (13)

Dovetail joint between two wooden panels ( 1 . 2 ), wherein the front side ( 3 ) a first plate ( 1 ) forming a joint line ( 4 ) perpendicular to the broadside ( 5 ) of the second plate ( 2 ), with at least one dovetail ( 6 ) on one of the plates ( 1 ) and at least one slot ( 7 ) for receiving the dovetail pin ( 6 ) on the other plate ( 2 ), characterized in that the dovetail ( 6 ) as a conical on the one plate ( 1 ) is formed to taper pin, that the slot ( 7 ) with a pin insertion hole ( 9 ) and a subsequent pin clamping hole ( 10 ) is formed, wherein the pin clamping hole ( 10 ) conically corresponding to the dovetail ( 6 ), wherein the dovetail connection for insertion of the dovetail pin ( 6 ) perpendicular to the broadside ( 5 ) in the Zapfeneinführloch ( 9 ) and for telescoping the dovetail pin ( 6 ) and the pin clamping hole ( 10 ) parallel to the joint line ( 4 ) is trained. Dovetail joint according to claim 1, characterized in that the dovetail ( 6 ) on the front side ( 3 ) of the first plate ( 1 ) and the slot ( 7 ) for receiving the dovetail pin ( 6 ) on the broadside ( 5 ) of the second plate ( 2 ) are formed. Dovetail joint according to claim 1, characterized in that the dovetail ( 6 ) as a cantilever with a conical undercut ( 8th ) is formed on its narrow and broad sides. Dovetail joint according to claim 3, characterized in that the dovetail ( 6 ) with a perpendicular from the free end face ( 11 ) of extending slot ( 12 ) is provided so that two resiliently spreadable pin arms ( 13 . 14 ) are formed. Dovetail joint according to claim 1, characterized in that the slot ( 7 . 7 ' ) is a through hole. Dovetail joint according to claim 1, characterized in that the slot ( 7 . 7 ' ) is a blind hole. Dovetail joint according to claim 1, characterized in that the slot ( 7 ' ) two in the dash line direction successively arranged pin clamping holes ( 10 . 10 ' ) between which the pin insertion hole ( 9 ' ) is arranged. Made of individual wood panels ( 1' . 1'' . 2 ' . 2 '' . 17 . 18 ) composable, cuboid packaging box ( 16 ), with a bottom plate ( 17 ), with from the bottom plate ( 17 ) vertically spaced first and second side plates ( 1' . 1'' . 2 ' . 2 '' ) and with a cover plate ( 18 ), whereby through the bottom plate ( 17 ) and the side plates ( 1' . 1'' . 2 ' . 2 '' ) a cuboid receiving space for packaged goods ( 19 ), characterized in that the first side plates ( 1' . 1'' ) the opposite broad sides of the box and the second side plates ( 2 ' . 2 '' ) form the opposite narrow sides of the box and that for connecting in each case a second side plate ( 1' . 1'' ) with the two first side plates ( 2 ' . 2 '' ) a plurality of dovetail pin connections are formed according to one of claims 1 to 7. Packaging box ( 16 ) according to claim 8, characterized in that the second side plates ( 2 ' . 2 '' ) with its broadside ( 5 ' . 5 '' ) to the end faces ( 3 ' . 3 '' ) of the first side plates ( 1' . 1'' ) and that at the end faces ( 23 . 23 ' ) of the first side plates ( 1' . 1'' ) several dovetails ( 6 ' ) and on the broadsides ( 5 ' . 5 '' ) of the second side plates ( 2 ' . 2 '' ) in to the dovetail ( 6 ' ) corresponding position several slots ( 7a ) for receiving the dovetail ( 6 ' ) and for forming a plurality of dovetail joints according to one of claims 1 to 7 are formed. Packaging box ( 16 ) according to claim 9, characterized in that the first side plates ( 1' . 1'' ) with its broadside ( 23 . 23 ' ) to corresponding end faces ( 24 . 24 ' ) of the bottom plate are attached, and that at these end faces ( 24 . 24 ' ) of the bottom plate ( 17 ) several dovetails and on the broadsides ( 23 . 23 ' ) of the first side plates ( 1' . 1'' ) are formed in corresponding to these dovetail pin multiple slots for receiving the dovetail and forming a plurality of dovetail connections according to one of claims 1 to 7. Packaging box ( 16 ) according to claim 8, characterized in that on the cover plate ( 18 ) Anti-slip devices are installed to prevent slipping when stacking the packaging boxes. Packaging box ( 16 ) according to claim 11, characterized in that on the bottom plate ( 17 ) standing feet ( 20 ) with plastic gliders ( 21 ) are formed. Packaging box ( 16 ) according to claim 12, characterized in that the anti-slip devices as to the feet ( 20 ) with the plastic glides ( 21 ) negative corresponding depressions ( 22 ) in the cover plate ( 18 ) are formed.

Images