TECHNICAL FIELD OF THE INVENTION

The present invention relates to a housing structure for an electrical device ac- cording to the preamble of the appended independent claim. The invention also relates to an electrical device incorporating such a housing structure.

BACKGROUND OF THE INVENTION

An electrical device is required to function safely in all circumstances, without causing any danger to its users. In the event of a malfunction, an electrical device should always break safely.

An electrical device is usually well protected to prevent users from electrical shocks during normal operation of the device and in the event of an electrical malfunction, such as a short circuit. However, if the mechanical structure of an electrical device is damaged, the risk for an electrical shock increases considerably. For example, if a housing of an electrical device is detached from the device body or is broken into pieces due to a mechanical shock, live electrical contacts and wires could be exposed within reach of a user.

A typical electrical device, which is susceptible to mechanical shocks, is a battery charger of a mobile device, such as a mobile phone, a laptop or a tablet computer. A known battery charger comprises a housing structure which has two opposing end walls and a surrounding side wall connecting the end walls. Typically the housing structure is formed of two separate housing parts which are attached together during assembly. The first housing part consists of one end wall and the surrounding side wall, which define a cavity, inside which a circuit board is ar- ranged. The second housing part consists of the other end wall, through which connector pins are arranged to pass and to be in electrical contact with the circuit board.

A problem associated with the above described housing structure is that it is not designed to break safely. In the event of a mechanical shock to the battery charger, the housing parts may be detached from each other, thus exposing the connector pins which protrude from the end wall of the second housing part. If the battery charger is still connected to a wall socket, there is a potential risk for an electrical shock from the live connector pins.

OBJECTIVES OF THE INVENTION

It is the main objective of the present invention to reduce or even eliminate prior art problems presented above.

It is an objective of the present invention to provide a housing structure for an electrical device. In more detail, it is an objective of the invention to provide a housing structure which protects from electrical shocks even in a case where the housing structure has been damaged due to an impact. It is also an objective of the inven- tion to provide a housing structure which is easy to manufacture and assemble.

It is a further objective of the present invention to provide an electrical device having a housing structure which efficiently protects users of the electrical device from electrical shocks.

In order to realise the above-mentioned objectives, the housing structure accord- ing to the invention is characterised by what is presented in the characterising part of the appended independent claim. Advantageous embodiments of the invention are described in the dependent claims.

DESCRIPTION OF THE INVENTION

A typical housing structure according to the invention for an electrical device com- prises a first housing part comprising a first end wall and a first surrounding side wall extending from the first end wall, the first end wall and the first surrounding side wall defining a first cavity, and a second housing part connected to the first housing part, the second housing part comprising a second end wall opposing the first end wall, and connector pins passing through the second end wall. In a typical housing structure according to the invention the second housing part comprises a second surrounding side wall extending from the second end wall into the first cavity, the second end wall and the second surrounding side wall defining a second cavity that is partly closed by a third end wall.

In other words, the housing structure according to the invention comprises two housing parts which both have a structure defining an internal cavity. When attached together, the housing parts are at least partly within each other in such a manner that the first surrounding side wall at least partly surrounds the second surrounding side wall. The surrounding side wall as well as the end wall can have various different shapes depending on the purpose of the electrical device for which the housing structure is designed. The surrounding side wall may have, for example, a cylindrical shape. Typically the end wall is essentially flat. The housing parts are manufactured separately and attached together during the assembly of an electrical device. The housing parts are attached together, for example by gluing or by ultrasonic welding, or by using fasteners, such as screws. The housing parts may also be provided with integral fasteners which lock the housing parts together. The housing structure according to the invention is suitable for accommodating a circuit board inside it. The circuit board comprises electronic components, the type, number and interconnection of which can vary depending on the function of an electrical device. The housing structure is especially suitable for a plug-type electrical device which is intended to be connected to a wall socket via connector pins through which electrical current is fed to a circuit board of the electrical device.

The connector pins are arranged to go through the second end wall of the second housing part in such a manner that the first ends of the connector pins extend into the second cavity. The first ends of the connector pins are enclosed by the second cavity, i.e. the first ends of the connector pins are arranged inside the second cavity. The second ends of the connector pins are intended to be inserted into holes of a wall socket. The second end wall comprises holes through which the connector pins are arranged to go through. The number of connector pins is typically two or three. The third end wall is preferably attached to a perimeter of the second surrounding side wall, opposing the second end wall. The third end wall limits the size of an opening of the second cavity, and thus makes the housing structure safer. The third end wall thus enables to dimension the size of the opening of the second cavity independently of the dimensions of the second cavity. In some cases the di- mensions of the second cavity may be quite large because of the space required by electronic components inside it.

A purpose of the second surrounding side wall and the third end wall attached to it is to protect a user from an electrical shock in a case where the housing parts are detached from each other, for example due to an impact. Because of the partly closed second cavity defined by the second end wall, the second surrounding side wall and the third end wall, the first ends of the connector pins are well protected, and thus they cannot be easily touched. When electrical current is fed to an electrical device via connector pins, the second housing part can be safely discon- nected from a wall socket even if the first housing part has been detached from the second housing part. The housing structure according to the invention enables an electrical device incorporating such a housing structure to break safely.

According to an embodiment of the invention the second cavity has an essentially rectangular opening. The opening of the second cavity is defined by the second surrounding side wall and the third end wall attached to it. A rectangular opening is suitable for receiving a portion of a circuit board through it to the second cavity so that electrical current can be fed via that portion to the circuit board.

According to an embodiment of the invention the opening of the second cavity has a width of less than 4 mm. The width of the opening of the second cavity can al- ternatively be less than 3 mm or even less than 2 mm. A narrow opening prevents a user from touching live electrical contacts and wires, for example connector pins, inside the second cavity, and thus efficiently protects the user from electrical shocks in a case where the housing parts are detached from each other. The length of the opening is typically chosen according to the dimensions of a circuit board that is arranged inside the housing structure. The length of the opening can be, for example, 10-50 mm, 10-30 mm or 20-40 mm.

According to an embodiment of the invention the first surrounding side wall extends to the second end wall. This means that the second surrounding side wall is completely surrounded by the first surrounding side wall. The first surrounding side wall may have been attached to the second end wall and/or to the second surrounding side wall. This arrangement makes the housing structure more robust against mechanical shocks.

According to an embodiment of the invention the depth of the first cavity is at least 10 mm. The depth of the first cavity can alternatively be at least 20 mm, at least 30 mm, or 10-50 mm. The depth of the first cavity is preferably chosen according to the dimensions of a circuit board that is to be arranged inside the housing structure. Typically, the depth of the first cavity is 2-10 mm less than the length of the circuit board that is arranged inside the housing structure. According to an embodiment of the invention the depth of the second cavity is at least 3 mm. The depth of the second cavity can alternatively be at least 4 mm, 3-6 mm, or 4-10 mm. Preferably, the second cavity is so deep that contact pads of a circuit board can be arranged completely inside the second cavity. The present invention also concerns an electrical device which comprises a housing structure according to the invention. The electrical device can be, for example, a battery charger of a mobile device. The electrical device is preferably a plug-type electrical device which comprises a circuit board inside the housing structure and connector pins arranged through the housing structure so that the electrical device may be connected to a wall socket.

According to an embodiment of the invention the electrical device comprises a circuit board attached to the first housing part in such a manner that a first end of the circuit board protrudes into the second cavity. The first housing part may comprise, for example, rails to which the circuit board is attached. The circuit board compris- es a plurality of electronic components, the number and type of which depends on the purpose of the electrical device.

Preferably, the portion of the circuit board which protrudes into the second cavity through its opening comprises only contact pads through which electrical current is fed to the circuit board. In other words, preferably the first end of the circuit board does not comprise electronic components. Because of this the width of the opening of the second cavity can be made very small.

An advantage of attaching the circuit board to the first housing part is that in a case where the housing parts are detached from each other, the circuit board is electrically disconnected from the second housing part. Because electrical current is fed to the electrical device through the connector pins of the second housing part, this arrangement prevents the user from getting an electrical shock from the circuit board.

According to an embodiment of the invention the connector pins are arranged to pass through the second end wall in such a manner that first ends of the connector pins extend into the second cavity and are coupled to the first end of the circuit board. The connector pins are typically arranged perpendicular to the second end wall. The first ends of the connector pins are coupled to contact pads of the circuit board. Preferably, connector pins are AC pins, which are meant to be inserted to a wall socket from which electrical current is fed to the circuit board. According to an embodiment of the invention the first ends of the connector pins comprise contact springs by means of which the connector pins are coupled to the circuit board.

According to an embodiment of the invention the distance between the first end of the connector pin and the plane defined by the opening of the second cavity is at least 2.5 mm. The farther away the first end of the connector pin is from the opening of the second cavity, the safer the housing structure is. The distance between the first end of the connector pin and the plane defined by the opening of the second cavity may alternatively be at least 4 mm or at least 6 mm. According to an embodiment of the invention the electrical device comprises a cable passing through the first end wall and coupled to the circuit board. The cable is coupled to a second end of the circuit board. The cable can be, for example, a USB cable which is intended to be connected to a device, such as a mobile phone, to be charged. The exemplary embodiments of the invention presented in this text are not interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this text as an open limitation that does not exclude the existence of also unrecited features. The features recited in the dependent claims are mutually freely combinable unless otherwise explicitly stated. BRIEF DESCRIPTION OF THE DRAWINGS

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of spe- cific embodiments when read in connection with the accompanying drawings.

Fig. 1 illustrates a housing structure according to an embodiment of the invention, fig. 2 illustrates a battery charger according to an embodiment of the invention, and fig. 3 illustrates a partial cross section of the battery charger of fig. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The same reference signs are used of the same or like components in different embodiments.

Fig. 1 illustrates a housing structure according to an embodiment of the invention. The housing structure comprises two housing parts 101 , 102 which both have a structure defining an internal cavity 103, 104. The housing parts 101 , 102 are shown as separated from each other in order to better illustrate the internal structure of the housing.

The first housing part 101 comprises a first end wall 105 and a first surrounding side wall 106 extending from the first end wall 105. The first end wall 105 and the first surrounding side wall 106 define the first cavity 103. Similarly, the second housing part 102 comprises a second end wall 107 and a second surrounding side wall 108 extending from the second end wall 107. The second end wall 107 and the second surrounding side wall 108 define the second cavity 104.

When attached together, the housing parts 101 , 102 are partly within each other in such a manner that the first surrounding side wall 106 surrounds the second surrounding side wall 108. In other words, when the housing parts 101 , 102 are connected together, the second surrounding side wall 108 protrudes into the first cavity 103.

The housing parts 101 , 102 are attached together during the assembly of an elec- trical device. In the housing structure of fig. 1 , the first surrounding side wall 106 extends to the second end wall 107 when the housing parts 101 , 102 are attached together. The first surrounding side wall 106 is attached to the second end wall 107 and/or the second surrounding side wall 108 by gluing or by ultrasonic welding. The housing structure of fig. 1 comprises two connector pins 109, i.e. AC pins, which are arranged through holes of the second end wall 107 in such a manner that first ends of the connector pins 109 protrude into the second cavity 104. Second ends of the connector pins 109 are meant to be inserted to a wall socket. The first ends of the connector pins 109 are connected to contact springs 1 10. Through the connector pins 109 and the contact springs 1 10, electrical current can be fed to a circuit board (not shown in fig. 1 ) which is accommodated within the housing structure. The first ends of the connector pins 109 and the contact springs 1 10 are arranged inside the second cavity 104 in such a manner that the distance between them and the plane defined by the opening of the second cavity 104 is a couple of millimetres.

The second cavity 104 is partly closed by a third end wall 1 1 1 . The third end wall 1 1 1 is attached to a perimeter of the second surrounding side wall 108, opposing the second end wall 107. The purpose of the third end wall 1 1 1 is to decrease the size of the opening of the second cavity 104 so much that a circuit board (not shown in fig. 1 ) just barely fits through it. The width of the opening delimited by the third end wall 1 1 1 is so small that electronic components of a circuit board cannot be arranged through the opening. However, contact pads arranged at a circuit board are so low that they fit through the opening and can thus be arranged in contact with contact springs 1 10. Internally the second cavity 104 may have been divided into portions, for example into three portions, with dividing plates.

The first end wall 105 comprises an aperture 1 12 through which a cable (not shown in fig. 1 ) can be arranged to be connected to a circuit board that has been placed inside the housing structure.

Fig. 2 illustrates a battery charger according to an embodiment of the invention. The battery charger is an example of a plug-type electrical device which comprises a circuit board inside a housing structure and connector pins arranged through the housing structure so that the electrical device may be connected to a wall socket. Fig. 2 shows the step of attaching the housing parts 101 , 102 together and the assembled battery charger. Fig. 3 illustrates a partial cross section of the battery charger of fig. 2. The battery charger of figs. 2 and 3 comprises a housing structure which is similar to that of fig. 1 .

Referring now to fig. 2 and the upper part of the figure therein, it shows the battery charger in a stage where the housing parts 101 , 102 are to be attached together. The battery charger comprises a circuit board 201 which is arranged inside the first cavity 103 of the first housing part 101 and attached to the interior of the first surrounding side wall 106. The circuit board 201 is attached to the first housing part 101 in such a manner that it partly protrudes out of the first cavity 103. When the housing parts 101 , 102 are attached together, a first end of the circuit board 201 protrudes into the second cavity 104 through the opening which is delimited by the third end wall 1 1 1 . The portion of the circuit board 201 which protrudes into the second cavity 104 comprises contact pads 202 through which electrical current is fed to the circuit board 201 . In the assembled battery charger, the contact pads 202 of the circuit board 201 are in contact with the contact springs 1 10 that are connected to the first ends of the connector pins 109. This can be seen in fig. 3.

The circuit board 201 comprises electronic components 301 . The portion of the circuit board 201 which is inside the second cavity 104 does not comprise any electronic components 301 , only the contact pads 202 and the necessary electrical connections are arranged on said portion of the circuit board 201 .

Only advantageous exemplary embodiments of the invention are described in the figures. It is clear to a person skilled in the art that the invention is not restricted only to the examples presented above, but the invention may vary within the limits of the claims presented hereafter. Some possible embodiments of the invention are described in the dependent claims, and they are not to be considered to restrict the scope of protection of the invention as such.