WO2015043924A1

WO2015043924A1 - Casing for a household appliance

Info

Publication number: WO2015043924A1
Application number: PCT/EP2014/068922
Authority: WO
Inventors: Ramesh Mohan; Mahantesh NIMBARAGI
Original assignee: BSH Bosch und Siemens Hausgeräte GmbH; Robert Bosch Engineering And Business Solutions Limited
Priority date: 2013-09-30
Filing date: 2014-09-05
Publication date: 2015-04-02
Also published as: EP3099950A1; IN2013CH04455A

Abstract

A casing for an electrical appliance comprises at least two casing panels (1, 3) made of sheet metal and a screw for fixing said two panels (1, 2, 3) to each other and for establishing an electrically conductive junction between them. A first one (3) of said panels has a first cutout formed in a region which overlaps said second panel (1), said second panel (1) has a second cutout which overlaps said first cutout and at least one boss (21). The screw (10) extends through an overlapping portion (23) of said cutouts, and the boss (21) engages said first cutout.

Description

Casing for a household appliance

The present invention relates to a casing for a household appliance, in particular to the problem of grounding components of the casing. Conventionally a household appliance such as a refrigerator, a freezer, a kitchen stove, a dishwasher or a washing machine has a casing the outer surface of which comprises large portions made of sheet metal which must be reliably grounded. If one of these components is directly connected to a ground conductor, other components can be grounded by establishing electrical contact to said first component when the appliance is assembled. Conventionally, such a contact is achieved using a screw which extends through holes of a first and a second panel of the appliance casing and the head of which is serrated in order to scratch through a paint layer of the first panel and thus establish an electrical contact with the sheet metal underneath, and in which the hole of the second panel has serrated edges which will be bent in contact with the shank of the screw and thereby enter into conductive contact.

The area in which the screw contacts the tips of these serrated edges is rather small, and if they are permanently deformed upon insertion of the screw, there is the possibility that if the screw is removed later on, e.g. if the casing must be opened for repair or maintenance purposes, the electrical contact will not be re-established when the screw is re-installed, and one of the panels is not properly grounded.

The object of the present invention is to provide a casing for an electrical appliance in which an electrical contact between two casing panels made of sheet metal is reliably re- established if the panels are repeatedly disassembled and re-assembled.

This object is achieved by a casing for an electrical appliance, comprising at least two casing panels made of sheet metal and a screw for fixing said two panels to each other and establishing an electrically conductive junction between them, wherein a first one of said panels has a first cutout formed in a region which overlaps said second panel, and said second panel has a second cutout which overlaps said first cutout the screw extending through said cutouts, and at least one boss which engages said first cutout. By engaging the first cutout, also the boss (or bosses) of the second panel can come into mechanical contact with the screw head, so that an electrical contact can be established by the serrations of the screw head scratching into the surface of the boss(es) facing it. Further, by the boss(es) engaging the first cutout, a position in which the panels can be fixed to one another is defined, facilitating their re-assembly.

In order to establish an electrical contact between the panels, a head of said screw should be in contact with said first panel and with said boss of the second panel. It should be noted, however, that this is not the only way by which, according to the present invention, an electric contact between the screw and the second panel can be ensured, and that others will be described subsequently.

A serrated surface of said screw head may be used for scratching the first panel and the boss of the second panel alike.

The electric contact can be improved by said first and second panels being clamped between a support and said screw head.

In order to press said first and second panels alike, both should preferably have a same thickness. In that case, a surface of the support facing the screw head may be flat.

According to a preferred embodiment, the overlapping cutouts of first and second panels define a screw hole, a circumferential surface of which is formed in part by edge portions of said first panel and in part by edge portions of said second panel. A ridge of said screw may then establish an electrical connection by being in contact with edge portions of both panels.

The portion of the ridge which passes through the screw hole extends along the circumference of the screw over a length equaling the thickness of said panels, multiplied by the circumference length of the screw and divided by its pitch. If the edge portions are shorter than this, the ridge will always be in contact with edge portions of both panels, regardless of the orientation of this ridge portion. Said first cutout can comprise a central portion and a plurality of branches extending radially from said central portion. The bosses of said second panel may then engage said branches, leaving the central portion for the passage of the screw.

The first panel may then comprise a plurality of fingers extending radially towards said central portion between said branches, and the edge portions of said first panel can be provided at the tips of said fingers.

Similarly, said second cutout may comprise a central portion and plurality of branches which extend radially from said central portion between said bosses. Here, the fingers of the first panel can engage in the branches of said second cutout.

The bosses may be provided on a plurality of fingers of said second panel, the fingers extending radially towards said central portion between said branches. Again, the edge portions of said second panel can be provided at the tips of said fingers.

The fingers of the second panel may be cranked to form said bosses.

The casing of the present invention may belong to a cooling appliance. In that case, one of said panels may be part of a sidewall of said casing whereas the other is a traverse extending underneath a machinery compartment.

Further features and advantages of the present invention will become apparent from the subsequent description of embodiments thereof, referring to the appended drawings.

Fig. 1 is an exploded perspective view of panels of a refrigerator casing according to the present invention;

Fig. 2 is an enlarged view of cutouts formed in the panels of Fig. 1 ;

Fig. 3 is a perspective view of bosses of a second panel engaging the cutout of the first panel; Fig. 4 is a cross section along lines IV-IV of Fig. 3 according to a first embodiment of the invention;

Fig. 5 is a cross section along lines IV-IV of Fig. 3 according to a second

embodiment; and

Fig. 6 is a cross section along lines IV-IV of Fig. 3 according to a third embodiment.

Fig. 1 is a perspective view of sidewall panels 1 , 2 and of a traverse panel 3 of a refrigerator casing according to the present invention. The sidewall panels 1 , 2 are made from painted sheet metal. Each comprises a vertical member 4 which forms an outer side of a sidewall of the refrigerator casing, and a horizontal flange 5 which extends inwardly from a bottom edge of vertical member 4.

Next to sidewall panel 1 , a reinforcement member 6 is shown. The reinforcement member 6 comprises a plate-shaped hollow body injection-molded from plastics material. When the refrigerator casing is assembled, one of the two main sides 7 of reinforcement member 6 body is in contact with an inner side of vertical member 4, a narrow side 8 is in contact with flange 5, and the other main side 7 delimits a machinery compartment 9 which, as usual in the art, is formed in a bottom rear portion of the refrigerator casing. A similar reinforcement member, not shown, is associated to sidewall panel 2. The traverse panel 3, subsequently also referred to as traverse 3, extends underneath said machinery compartment, supporting components installed in the machinery compartment, such as a compressor and, possibly, a fan, a condenser etc., and is connected to sidewall panels 1 , 2 by means of screws 10 engaging cutouts 1 1 , 12 of flanges 5 and traverse 3 and holes 13 of reinforcement members 6.

Preferably, the screws 10 are machine screws having a constant diameter thread 24 and a head 25. An underside of head 25, i.e. the side facing flange 5 and traverse 3 in Fig. 1 is serrated so that when the screw 10 is driven into hole 13 and its head comes to abut against flange 5 and traverse 3, it will scratch through a paint layer formed thereon and provide electrically conductive metal-to-metal contact with both. Fig. 2 is an enlarged view of the cutouts 1 1 , 12 of flange 5 and traverse 3. While Fig. 1 is a perspective view of panels 1 , 2, 3 from below; showing these in the orientation they would normally have in the refrigerator casing, in Fig. 2 the flange 5 and the traverse 3 are shown in a turned-over configuration, i.e. bottom sides of flange 5 and traverse 3 are turned up and are shown as seen from above.

The cutout 1 1 of traverse 3 comprises a circular central portion 14 and four branches 15 extending radially outward from said central portion 14. Each branch 15 is shaped as a 45° circle sector, with the center of the circle sectors coinciding with the center of central portion 14. Between two branches 15, there is a finger 16 of traverse 3 extending radially inward, the tip of each finger 16 forming a circular arc 17 of 45° which delimits the central portion 14.

The cutout 12 of flange 3 is similar in shape to cutout 1 1 , having a circular central portion 18 and branches 19 extending therefrom. Fingers 20 of flange 3 extend between said branches 19 and are cranked so as to form bosses 21 . Again, the tips of fingers 20 are shaped as circular arcs 22.

As shown in Fig. 3, when the panels 1 , 3 are correctly assembled, the bosses 21 fill the branches 15 of cutout 1 1 , and the central portions 14, 18 of cutouts overlap, so as to form a circular screw hole 23 delimited by the arcs 17, 22 of fingers 16, 20.

As known in the art, the thread 24 of screw 10 comprises a cylindrical core and one or more ridges extending helicoidally around said core. The radius of screw hole 23 is larger than the radius of said core and smaller than the radius of the core plus the width of the ridge, so that when the screw 10 is driven into screw hole 23, the ridge will rub along the edge of screw hole 23 along a helicoidal path 26. The thread 24 may e.g. be a M5 thread, in which case the diameter of screw hole can be 4.9 mm. The M5 thread has a pitch of 0.8 mm, so that if the sheet metal of flange 5 and traverse 3 is e.g. 0.25 mm thick, in the portion of thread 24 received in screw hole 23, the path 26 spans an angle of

2π 0.25mm/0.8mm = 1 12.5°, which is more than twice the angle spanned by one of arcs 17, 22. Therefore, the ridge of screw 10 will be in contact with more than one of arcs 17, 22, and will establish an electrically conductive contact with both sidewall panel 1 and traverse 3. Generally, the number of arcs 17, 22 which delimit the screw hole 23 should be the higher, the thinner the panels 1 , 2, 3 are, in order to ensure that the ridge of screw 10 touches arcs of both the flange 5 and the traverse 3. If none of the arcs 17, 22 is longer than the thickness of said panels, multiplied by the circumference length of the screw and divided by its pitch, the ridge will not fit on a single one of said arcs.

Fig. 4 is a cross section of reinforcement member 6, flange 5 and traverse 3 taken along line IV-IV of Fig. 3 according to a first embodiment. In the region shown, traverse 3 is flat. Flange 5 and traverse 3 have a same thickness, and boss 21 is cranked out of the plane of flange 5 so that inner and outer sides of boss 21 are flush with those of traverse 3.

When the bosses 21 are received in the branches 15 of traverse 3, traverse 3 and flange 5 combine to form a shallow indentation which is engaged by a flat boss 27 of

reinforcement member 6, extending around hole 13. A metal nut 29 may be embedded reinforcement member 6, forming within hole 13 a female thread in which screw 10 is reliably held.

When the screw 10 is received in screw hole 23 and hole 13, and its head 25 abuts against outer sides of fingers 16, 20, inner sides thereof are supported by boss 27.

Therefore, the fingers 16, 20 cannot yield to the pressure of screw head 25 and are scratched by its serrations 28.

In the embodiment of Fig. 5, the narrow side 8 of reinforcement member 6 is flat, and so is flange 5. Instead, fingers 16 of traverse 3 are cranked, so as to form bosses which engage branches 19 of flange 5. If these bosses do not yet touch reinforcement member 6, as shown in Fig. 6, they will be pressed into contact therewith when urged by screw head 25.

Fig. 6 illustrates a case where the thickness of traverse 3 and flange 5 is not identical. As in case of Fig. 5, fingers 16 of traverse 3 are cranked and have an outer side, facing the serrations 28 of screw head 25. This outer side is closer to screw head 25 than the outer side of flange 5 is. Therefore, when screw 10 is tightened, screw head 25 will first abut against fingers 16, bend these until their tips, i.e. arcs 17, abut against reinforcement member 6, and the outer edge of screw head 25 will dig into fingers 16. When the screw 10 is turned slightly further, its serrations 28 will abut against the fingers 20 of flange 5, too, and will scratch these, whereby a further electrical contact between traverse 3 and flange 5 is established via screw head 25. In the Figs, described above, it has been assumed that the traverse 3 is screwed under the flanges 5 of sidewall panels 1 , 2 from underneath. As an alternative, traverse 3 might be clamped between the flanges 5 and the reinforcement members 6, i.e. elements designated as flange 5 in Figs. 4-6 might be part of traverse 3 and vice versa.

Reference numerals

1 sidewall panel

2 sidewall panel

3 traverse (panel)

4 vertical member

5 flange

6 reinforcement member

7 main side

8 narrow side

9 machinery compartment

10 screw

1 1 cutout

12 cutout

13 hole

14 central portion

15 branch

16 finger

17 arc

18 central portion

19 branch

20 finger

21 boss

22 arc

23 screw hole

24 thread

25 screw head

26 path

27 boss

28 serration

Claims

1 A casing for an electrical appliance, comprising at least two casing panels (1 , 2, 3) made of sheet metal and a screw (10) for fixing said two panels (1 , 2, 3) to each other and establishing an electrically conductive junction between them, wherein a first one (3) of said panels has a first cutout (1 1 ) formed in a region which overlaps said second panel (1 ), said second panel (1 ) has a second cutout (12) which overlaps said first cutout (1 1 ) and at least one boss (21 ), the screw (10) extending through said cutouts (1 1 , 12), and the boss (21 ) engaging said first cutout (1 1 ). 2 The casing of claim 1 , wherein a head (25) of said screw (10) is in contact with said first panel (3) and said boss (21 ). 3 The casing of claim 2, wherein the screw head (25) has a serrated surface (28) facing said panels (1 , 3).

4 The casing of claim 2 or 3, wherein said first and second panels (1 , 3) are clamped between a support (6) and said screw head (25). 5 The casing of claim 4, wherein said first and second panels (1 , 3) have a same thickness.

6 The casing of any of the preceding claims, wherein said overlapping cutouts (1 1 , 12) define a screw hole (23), a circumferential surface of which is formed in part by edge portions (17) of said first cutout (1 1 ) and in part by edge portions (22) of said second cutout (12), and a ridge of said screw (10) is in contact with edge portions (17, 22) of both cutouts (1 1 , 12).

7 The casing of claim 6, wherein each of said edge portions (17, 22) is shorter than the thickness of said panels (1 , 3), multiplied by the circumference length of the screw (10) and divided by its pitch. The casing of any of the preceding claims, wherein said first cutout (1 1 ) comprises a central portion (14) and a plurality of branches (15) extending radially from said central portion (14), and each branch (15) is engaged by a boss (21 ) of said second panel (1 ), and the first panel (3) comprises a plurality of fingers (16) extending radially towards said central portion (14) between said branches (15).

The casing of any of the preceding claims, wherein said second cutout (12) comprises a central portion (18) and plurality of branches (19) which extend radially from said central portion (18) between said bosses (21 ), and the second panel (1 ) comprises a plurality of fingers (20) extending radially towards said central portion (18) between said branches (19).

The casing of claim 9, wherein said fingers (20) of the second panel (1 ) are cranked to form said bosses (21 ).

The casing of claim 6 and at least one of claims 7 to 10, wherein the edge portions (17, 22) are formed at the tips of the fingers (16, 20) of said first and/or second panel (3, 1 ).

The casing of any of the preceding claims, wherein the appliance is a cooling appliance.

The casing of claim 12, wherein one of said panels (1 ) is part of a sidewall of said casing and the other is a traverse (3) extending underneath a machinery compartment (9).