SCREW CONNECTION

Abstract

The invention relates to a screw connection comprising a structural element (2) comprising a screw hole (2.1) and a metal sheet (3) comprising a through hole (3.1), the structural element (2) and the metal sheet (3) being adapted to be connected by means of a screw (4) by screwing the screw (4) through the through hole (3.1) of the metal sheet (3) into the screw hole (2.1) of the structural element (2), wherein the metal sheet (3) comprises an embossment (5), said embossment (5) at least partially surrounding the through hole (3.1) in order to increase the distance (d) between an upper surface of the metal sheet (3) and the screw hole (2.1) provided in the structural element (2).

Claims

1. Screw connection comprising a structural element comprising a screw hole and a metal sheet comprising a through hole, the structural element and the metal sheet being adapted to be connected by means of a screw by screwing the screw through the through hole of the metal sheet into the screw hole of the structural element, wherein the metal sheet comprises an embossment, said embossment at least partially surrounding the through hole in order to increase a distance between an upper surface of the metal sheet and the screw hole provided in the structural element, wherein the embossment comprises an upper portion comprising a contact surface, the screw head of the screw being adapted to rest against said contact surface and the embossment comprises a support portion protruding from the upper portion downwardly towards the structural element, the support portion at least partially resting at the structural element and at least partially radially confining the through hole.

2. Screw connection according to claim 1, wherein the embossment, is obtained by partial metal forming or deep drawing of the metal sheet.

3. Screw connection according to claim 1, wherein the support portion is formed by a ring-shaped rim.

4. Screw connection according to claim 1, wherein the support portion protrudes perpendicular from the upper portion.

5. Screw connection according to claim 1, wherein the support portion protrudes downwardly and comprises a free end that is oriented to abut essentially perpendicularly on the structural element, the support portion protruding downwardly from said upper portion.

6. Screw connection according to claim 1, wherein the embossing comprises an annular, cup-like shape.

7. Screw connection according to claim 1, wherein the metal sheet comprises a wall thickness (t) below 0.5 mm.

8. Screw connection according to claim 1, wherein the structural element is at least partially formed by a metal sheet.

9. Screw connection according to claim 1, wherein the screw is a self-tapping screw.

10. Household or kitchen appliance comprising the screw connection according to claim 1.

11. A screw connection comprising a thin metal sheet having a through hole and a structural element having a screw hole smaller than said through hole, said thin metal sheet and said structural element being disposed adjacent to one another such that said through hole and said screw hole are aligned, an embossment formed, and positioned adjacent to said through hole in said thin metal sheet, the embossment being formed by deforming said thin metal sheet, said embossment comprising an upper portion defining a contact surface adapted to support a screw head resting thereagainst and a support portion that protrudes downwardly from said upper portion and extends in an axial direction toward the structural element, a free end of the support portion abutting against said structural element thereby fixing a gap between said structural element and said contact surface of said upper portion, said gap having a length at least twice the thickness of the structural element surrounding the screw hole, said support portion at least partially radially confining the through hole and being configured to be axially stressed when a screw is inserted from above said embossment through said through hole and rotated to apply fastening torque to fasten together said thin metal sheet and said structural element, such that said support portion will resist force applied by tightening said screw and effectively avoid the screw flattening the support portion thereby maintaining said gap when said screw is tightened, said thin metal sheet having a thickness less than 0.5 mm.

12. The screw connection of claim 11, said embossment having an annular, cup-like shape that surrounds said through hole, said through hole being disposed in a central recess defined by said support portion, said contact surface having a ring shape surrounding said recess.

13. The screw connection of claim 12, said through hole having a diameter at least 30% greater than the diameter of the screw hole, said support element being a frame of a household appliance.

14. The screw connection of claim 12, further comprising said screw inserted through said through hole and tightened to fasten together said thin metal sheet and said structural element, such that an underside of the screw head rests against said contact surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The various aspects of the invention, including its particular features and advantages, will be readily understood from the following detailed description and the accompanying drawings, in which:

[0019] FIG. 1 shows an example schematic sectional view of a screw connection;

[0020] FIG. 2 shows an example schematic view of a baking oven; and

[0021] FIG. 3 shows an enlarged detail view of FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0022] The present invention will now be described more fully with reference to the accompanying drawings, in which example embodiments are shown. However, this invention should not be construed as limited to the embodiments set forth herein. Throughout the following description similar reference numerals have been used to denote similar elements, parts, items or features, when applicable.

[0023] FIG. 1 illustrates an example embodiment of a screw connection 1. The screw connection 1 comprises a structural element 2 and a metal sheet 3. The structural element 2 may be, for example, a metal sheet, too. In the following, the structural element 2 is referred to as first metal sheet 2 and the metal sheet 3 is referred to as second metal sheet 3. Said first and second metal sheets 2, 3 may form part of complex components of kitchen or household appliances. For example, the first metal sheet 2 may be, for example, a part of a household appliance, e.g. a metal cladding element, a frame element or a structural unit of a household appliance or the like. The second metal sheet 3 may be, for example, a housing element of the kitchen or household appliance or any other component, which has to be fixed to the first metal sheet 2 based on a screw connection 1.

[0024] The first metal sheet 2 comprises a screw hole 2.1 for receiving a thread portion 4.2 of a screw 4. For example, the screw 4 may be a self-tapping screw, i.e. before screwing the screw 4 into the screw hole 2.1 for the first time, there is no thread provided in the screw hole 2.1.

[0025] Especially in case that the second metal sheet 3 is made of a thin metal sheet, e.g. with a thickness t lower than 0.5 mm, the problem occurs that the strength of the screw connection 1 decreases becausedue to the low thickness of the second metal sheet 3there is only a low distance between the screw hole 2.1 and the screw head 4.1.

[0026] In order obtain a high-strength screw connection 1, the second metal sheet 3 comprises an embossment 5. The embossment 5 may be obtained by a partial metal forming, e.g. by deep drawing or the like. By means of the embossment 5, the distance d between the first metal sheet 2 and the second metal sheet 3 in the area of the screw hole 2.1 is increased. Thereby the risk that the thread run-out directly below the screw head 4.1 interacts with the screw hole 2.1 is reduced.

[0027] As shown in FIG. 1, a through hole 3.1 is provided through the second metal sheet 3, said through hole 3.1 being arranged in the area of the embossment 5. Preferably, the through hole 3.1 is provided in the centre of the embossment 5.

[0028] According to embodiments, the embossment 5 may be formed by two or more protrusions surrounding the through hole 3.1. Preferably, the embossment 5 may be formed by a single ring-shaped protrusion encompassing the through hole 3.1. The diameter of the through hole 3.1 may be dimensioned such that the thread 4.3 of the screw 4 does not engage in the side wall limiting the through hole 3.1. For example, the diameter of the through hole 3.1 may be significantly greater than the diameter of the screw hole 2.1 (e.g. at least 30%, 40% or 50% greater) in order to ensure that a conical portion 4.4 of the screw 4 being arranged at the lower side of the screw head 4.1, said conical portion 4.4 providing a transition portion between the screw head 4.1 and the thread portion 4.2, is received within the through hole 3.1.

[0029] In the following, the embossment 5 provided at the second metal sheet 3 is described in closer detail. The embossment 5 is obtained by deforming the second metal sheet 3 around the through hole 3.1 such that a three-dimensional shaping of a metal portion of the second metal sheet 3 is obtained. Due to said three-dimensional shaping, one or more protrusions are obtained which form a contact surface 5.1 which interacts with a planar, lower surface 4.1.1 of the screw head 4.1. In other words, after screwing the screw 4 through the through hole 3.1 into the screw hole 2.1, the lower surface 4.1.1 of the screw head 4.1 rests against the contact surface 5.1.

[0030] The contact surface 5.1 may be provided at an upper portion 5.5 of the embossment 5. Said upper portion 5.5 may be, for example, arranged in parallel to the first metal sheet portion in which the screw hole 2.1 is provided. Said upper portion 5.5 constituting the contact surface 5.1 may be coupled with the portion of the second metal sheet 3 surrounding the embossment 5 by means of one or more connection portions 5.3. Said connection portion 5.3 may protrude upwardly from the second metal sheet portion surrounding the embossment 5 thereby leading to a gap between the lower surface 5.4 of the embossment 5 and the first metal sheet 2. Said connection portion 5.3 may be arranged at a certain distance to the through hole 3.1, e.g. a distance which is equal or greater than the screw hole 2.1.

[0031] Furthermore, the embossment 5 comprises a support portion 5.2. Said support portion 5.2 may protrude from the upper portion 5.5 downwardly towards the first metal sheet 2. Preferably, the end face of the support portion 5.2 may rest against the upper side of the first metal sheet 2. Thereby, the support portion 5.2 forms a prop or reinforcement element which supports the upper portion 5.5 thereby avoiding a deformation of the embossment 5 in case of tightening the screw 4. As a result, the fastening torque of the screw 4 might be increased.

[0032] As shown in FIG. 1, the support portion 5.2 protrudes upwardly from the first metal sheet 2. Preferably, the support portion 5.2 vertically protrudes from the first metal sheet 2. Thereby, the support portion 5.2 forms a wall portion which confines the through hole 3.1 in radial direction.

[0033] Preferably, the embossment 5 is formed in one piece at the second metal sheet 3, e.g. by deforming the metal sheet. The embossment 5 may be, for example, a ring-shaped cup surrounding the through hole 3.1 wherein the opening of the ring-shaped cup opens towards the first metal sheet 2. Alternatively, there may be a plurality of embossments 5 provided around the through hole 3.1, said embossments 5 providing contact surfaces 5.1 for the lower surface 4.1.1 of the screw head in order to enable a distancing of the screw head 4.1 from the screw hole 2.1.

[0034] FIG. 2 shows a schematic diagram of a household or kitchen appliance 10, according to the present embodiment constituted by a baking oven. The baking oven may comprise one or more metal plates which are fixed at a structural element of the oven by means of upper-mentioned screw connection 1. According to other embodiments, the household or kitchen appliance 10 may be a dish washer, a washing machine, a dryer or the like.

[0035] FIG. 3 shows in enlarged detail of FIG. 2 the support portion 5.2 which protrudes downwardly from the upper portion 5.5 towards the structural element 2. The support portion 5.2 has a free end 5.2.1 which is oriented to abut essentially perpendicularly on the structural element 2. Due to said perpendicular orientation of its free end 5.2.1, the support portion 5.2 is axially stressed by the screw 4 and has thus a high stiffness that resists the force applied by the screw and effectively avoids that the screw flattens the support portion 5.2, thereby ensuring a screw connection that has a considerably enforced strength.

[0036] As shown in FIGS. 1 and 3, the embossment 5 is integrally formed at the second metal sheet 3. More in detail, starting from a portion of the second metal sheet 3 which directly abuts against the first metal sheet 2 (left and right lateral zones of FIGS. 1 and 3), the connection portion 5.3 protrudes upwardly from said first metal sheet 2, specifically, the connection portion 5.3 protrudes vertically from the first metal sheet 2. The connection portion 5.3 may have a length such that the distance d between the first metal sheet 2 and the second metal sheet 3 is at least twice the thickness t of the first metal sheet 2. In other words, the support portion 5.2 may have a length (measured in the axial direction of the screw 4) at least twice the thickness t of the first metal sheet 2.

[0037] At the upper portion of the connection portion 5.3 distanced from the first metal sheet 2, the upper portion 5.5 protrudes laterally from said connection portion 5.3. Said upper portion 5.5 may protrude such that the first metal sheet 2 and the upper portion 5.5 are parallel to each other. The support portion 5.2 may protrude from the upper portion 5.5 downwardly towards the first metal sheet 2 wherein the free end 5.2.1 of the support portion 5.2 rests against the upper side of the first metal sheet 2. Preferably, the support portion 5.2 protrudes vertically from the upper portion 5.5 and the support portion 5.2 runs perpendicular to the first metal sheet 2.

[0038] As mentioned before, the embossment 5 may be an annular or ring-shaped embossment running around the screw hole 2.1. Alternatively, multiple embossments 5 may be arranged around the screw hole 2.1. The embossment 5 may have a U-shaped cross section with the support portion 5.2 and the connection portion 5.3 being the legs and the upper portion 5.5 being the bottom of said U-shaped embossment.

[0039] Said embossment 5 is advantageous because the distance between the lower surface 4.1.1 of the screw head 4.1 and the first sheet metal 2 comprising the screw hole 2.1 can be significantly increased. However, the embossment 5 comprises a high stiffness because the support portion 5.2 forms a bracing element between the upper portion 5.5 and the first metal sheet 2 thereby allowing a higher torque applied to the screw 4 which clearly enhances the stability of the screw connection.

[0040] Above, embodiments of a screw connection according to the present invention as defined in the appended claims have been described. These should be seen as merely non-limiting examples. As understood by a skilled person, many modifications and alternative embodiments are possible within the scope of the invention.

LIST OF REFERENCE NUMERALS

[0041] 1 screw connection

[0042] 2 structural element

[0043] 2.1 screw hole

[0044] 3 metal sheet

[0045] 3.1 through hole

[0046] 4 screw

[0047] 4.1 screw head

[0048] 4.1.1 lower surface

[0049] 4.2 thread portion

[0050] 4.3 thread

[0051] 4.4 conical portion

[0052] 5 embossment

[0053] 5.1 contact surface

[0054] 5.2 support portion

[0055] 5.2.1 free end of support portion

[0056] 5.3 connection portion

[0057] 5.4 lower surface

[0058] 5.5 upper portion

[0059] 10 household or kitchen appliance

[0060] d distance

[0061] t thickness