MXPA99001109A - Safety device for an electrical portable appliance energized by bater - Google Patents

Abstract

A safety device (10) is provided for a battery-powered portable electric device (11), the apparatus has a battery unit (12) with one or more than one of the electric batteries (13a-b) to supply power to the battery. electrical circuit (14) in the apparatus 11 the apparatus is connectable with a charging device (16) for charging the battery unit while maintaining the power supply to the apparatus. The safety device has a first fuse (20) which is connected between the electric batteries (13a-b) of the battery unit (12), and a first terminal (24) of the apparatus (11) to receive a charge current from the charging device (16), and a second fuse (21), which is connected between the electric batteries of the battery unit and a second terminal (26) of the apparatus (11), in order to supply power to the electric circuit (14) on the device. The fuses (20, 21) are operably independent of each other, particularly since the second fuse (21) maintains the electrical connection between the battery unit and the electrical circuit in the apparatus, even when or in case the first fuse (20) is released or opened in response to an undesired condition in. the car device

Description

'SAFETY DEVICE FOR A PORTABLE ELECTRIC APPLIANCE ENERGIZED BY BATTERIES " TECHNICAL FIELD The present invention relates to a safety device for a portable electric device energized by batteries, the apparatus comprising a battery unit for supplying power to the electrical circuit in the apparatus, and being connectable with a charging device for charging the battery unit while the power supply of the device is maintained.

DESCRIPTION OF THE PREVIOUS TECHNIQUE Rechargeable batteries are used in various portable applications, such as cell phones, communication radio devices, laptops per battery, video cameras, etc. Throughout this document, the discussion and description will be related to the first example cited above, that is, cell phones. However, this does not limit the invention to cell phones only, on the contrary, an expert in the art will understand, when taking - taking into account the description that will be given below, that the invention can be applied in several related technical fields. In the aforementioned applications, a rechargeable battery consists of a plurality (preferably 2 to 5) electrical cells, which are connected in series in order to provide an external supply voltage of between, for example, 3 to 6 volts, as desired. This battery unit comprises additional components, such as connection terminals, contact tabs, battery housing and fuses. Conventionally, electric NiCd (nickel-cadmium) batteries have been used frequently, but recently NiMH (nickel-metal hydride) and Li (lithium-iron, ~ lithium-polymer) batteries have become more common. Regardless of the type of battery, and for reasons of convenience, the battery can often be connected with a charging device to supply charging current to it, without having to remove the battery from e.g. cellphone. In addition, due to user demands, the battery will usually be charged without having to disconnect the cell phone or remove it from service. Figure 1 discloses a schematic functional diagram for a loading arrangement in accordance with the prior art. A number of electric batteries 13a, - 13b (in this case: two battery or electric batteries) are connected in series according to the above, and constitute a battery unit 12. The battery unit 12 is placed to supply power to a cellular telephone 11, which can be selected from any of the models available in the market, and which is therefore indicated schematically only by a dashed line. The cell phone comprises several circuits and electrical and electronic components, such as power amplifiers, microprocessor, filter circuits, local oscillators, etc. The presence of these circuits and components is evident to a person skilled in the art and therefore, the components are only represented by a common block of electronics 14. The battery unit 12 has two connections: a positive terminal and a negative terminal . To protect the battery, the electric batteries 13a, 13b are connected in series with a fuse 18, which will normally be resettable. A charging device 16 is placed to be fixed through the connections in the telephone 11 with the battery unit 12, for charging purposes. As it appears in the drawing, the battery can be charged while the mobile telephone 11 remains in operation, and according to the aforementioned, it is a demand of a common user.

A major disadvantage of the charging arrangement according to Figure 1 is that if the charging device due to some reason would supply to the battery unit 12 an excessively strong charging current, where the fuse 18 would open as consequence of this, then the voltage across the electronics block 14 in the mobile telephone would rise to a dangerously high level, where the circuits and components in block 14 would be damaged or completely destroyed. For this reason, at least, an additional fuse 19a and 19b, respectively (or some other kind of appropriate protection means), is required within the charging device 16 and the mobile telephone 11, respectively. This multiple fuse safety arrangement requires additional space and leads to an increase in manufacturing costs. Figure 2 illustrates a fuse 18 according to the prior art. A thin layer of an active material 17 is interposed between two metal contact tongues 15a, 15b. The active material 17 consists of a polymeric material and comprises thin carbon fibers, which normally conduct the electric current between the contact tongues 15a, 15b. When the magnitude of the current increases due to an electrical fault, the generation of heat in the active material 17 will increase as a consequence. The high temperature in the material causes an expansion of the material, where the carbon fibers will separate and interrupt the electrical connection between the contact tabs. The fuse is automatically resettable, since the carbon fibers will regain contact, once the material has cooled down. Previously known battery units are shown in, for example, Patent Number GB-A 2 239 567, U.S. Patent Number A-4 578 628, U.S. Patent Number A-4 916 954 and U.S. Patent Number A-4 555 451. Examples of useful fuses are found in U.S. Patent Number A-4 563 628, U.S. Patent Number A-5 367 280 and U.S. Patent Number A-5 146 150, among others.

COMPENDIUM OF THE INVENTION The object of the present invention is to provide the effective and reliable charging of the battery unit in a portable electrical apparatus, such as a cell phone, with a minimum of components and at a low material cost. The invention is particularly directed to eliminate the risk of damaging the electronics comprised in the apparatus due to an excessively high supply voltage, when the charging process deviates from the normal situation, for example, due to the release of a fuse in the battery unit. The object is achieved by a security device with features in accordance with the characterization portion of the appended independent patent claims. The preferred embodiments for the security device according to the invention are defined in the subsequent dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in greater detail below, reference being made to the accompanying drawings, in which Figure 1 is a schematic functional diagram of a known charging arrangement for a mobile telephone, Figure 2 discloses a fuse known, which is used in the arrangement according to Figure 1, Figure 3 is a schematic functional diagram of a charging arrangement for a mobile telephone, wherein the security device according to the invention is used, Figure 4 illustrates one embodiment of the security device according to the invention, as disclosed in Figure 3, and Figure 5 illustrates an alternative embodiment of the security device in Figure 3.

DETAILED EXHIBITION OF THE INVENTION As mentioned above, a known load arrangement is shown in Figures 1 and 2, as well as an example of a fuse used therein. In Figure 3, a cargo exposure is shown, wherein a security device 10 is used in accordance with a preferred embodiment of the present invention. As in Figure 1, a charging device 16 is placed to supply the charging current to a battery unit 12 fixed to a mobile telephone 11, for charging the battery unit. The charging device 16 and the mobile telephone 11, with their electronic components 14, are essentially identical to those already described with reference to Figure 1 and therefore, the exposure thereof is not repeated. The battery unit 12 comprises a plurality - here: two - electric batteries 13a, 13b of an arbitrary type (such as NiMH, of the Li or NiCd type), these batteries being connected in series in order to provide a sufficient level of an external supply voltage for driving the electronic components. A difference compared to Figure 1 is that the battery unit 12 is now provided with three terminals: a negative terminal, a first positive terminal and a second positive terminal. The first positive terminal is protected by a first fuse means 20 and is placed to connect to a first (positive) terminal 24 of the mobile telephone 11, while the second positive terminal is protected by a second fuse means 21 and is placed for connect with a second (positive) terminal 26 of the mobile phone. Finally, the negative terminal is placed to connect to a third terminal 40 (negative or connected to ground) of the mobile telephone 11. The battery unit 12 is positioned to receive the charging current from the charging device through the terminal 24. In addition, the battery unit is positioned to supply charging current to the mobile telephone 11, through the terminal 26. They are obtained the following advantages thanks to the arrangement of the invention of the terminals and fuses described above. If the charging device 16 no longer operates normally but instead supplies an excessively strong load current or is subject to short circuit, only the first fuse 20 will be released. This will abort the load, but the second fuse 21 will still be in operation, where the power supply of the mobile phone will not be affected. • The need for an additional fuse 19a in the charging device 16 or an additional fuse 19b in the mobile telephone 11 (see Figure 1) is eliminated, thus providing an advantage from an economic point of view. - The aforementioned arrangement allows two fuse means to be obtained such as an integrated security device 10, which will be described in more detail below, with reference to Figure 4. In Figure 4, a preferred embodiment of the device is shown. 10 security, in accordance with the invention. A thin layer of an active material 36 is deposited on a metal contact tab 30, which is placed to be connected in series in the electric cells 13a-b by means of welding, laser welding or knitting, etc. The active material 36 is a polymeric material, comprising thin fibers of carbon or other conductive material, these fibers normally conducting the electric current but which will separate in space and interrupt the path of the current, once the magnitude of the current increases as a result of an electrical fault (for example, the foregoing description with reference to Figure 2). Therefore, the material 36 is active since the current state thereof as an electric current conductor depends on a physical property - in this case, the magnitude of the current indirectly through the temperature of the material. The active material is known per se in the technical field, and therefore, a full disclosure will not be necessary here. Two contact plates 32 and 34, respectively, are placed on the layer of active material 36. Preferably, these are made of metal and are provided with a smooth top surface suitable for coupling with the corresponding terminals 24 and 26 in the mobile telephone 11. In the drawing, the terminals 24 and 26 are formed as spring contacts, which are positioned to resiliently press against a respective contact 32 and 34 in the security device 10. By providing the security device 10 with double security functions on the same substrate in accordance with the preferred embodiment, the aforementioned problems are solved in an efficient manner with respect to cost as well as space. Since the safety device is automatically resettable, the battery unit requires no maintenance in this regard. Figure 5 illustrates an improvement of the embodiment shown in Figure 4. Components that are identical in Figure 4 and Figure 5 have been provided with identical reference numbers in both figures. The safety device 10 according to Figure 5 has been provided with an additional contact means 42, which is placed in an electrically insulating layer 44. The layer 44 is placed on the contact tab 30, and therefore is the layer 36 of the active material. The contact means 42. it has a smooth top surface for receiving a third resilient contact means 40 in the mobile telephone 11. The contact means 42 is placed to be welded, brazed or otherwise connected to the negative side of the electric batteries 13a-b, while the contact tab 30 as above is placed to connect to the positive side of the electric batteries. Within the scope of the invention, as defined in the subsequent patent claims, the safety device can be obtained in other ways than those described above, which can be easily obtained by one skilled in the art. For example, an arrangement with bimetallic elements can be used instead of the active polymeric material. further, the security device does not necessarily have to be automatically resettable, even when this particularity is considered as being appropriate. Finally, it can be seen again that the invention can be used together with an electrical equipment other than mobile telephones.

Claims (8)

CLAIMS:

1. A safety device (10) for a portable electric device energized by batteries (11), the apparatus comprises a battery unit (12) with one or more electric batteries (13a-b) to supply power to the electric circuit (14) comprised in the apparatus, and the apparatus is positioned to connect with a charging device (16) for charging the battery unit while maintaining the power supply to the apparatus, characterized by a first fuse (20), which is placed to connect between the electric batteries (13a-b) of the battery unit (12) and a first terminal (24) of the apparatus (11), to receive charge current- from the charging device (16), and a second fuse ( 21), which is placed to connect between the battery cells (13a-b) of the battery unit (12), and a second terminal (26) of the apparatus (11) to supply power to the electric circuit (14) in the apparatus. the fuses (20, 21) being operably independent of one another, particularly since the second fuse (21) maintains the electrical connection between the battery unit and the electrical circuit in the apparatus, even when or in case the first fuse (20) is released or opened in response to an undesired condition in the loading device.

2. A safety device according to claim 1, characterized in that the fuses (20, 21) are physically integrated.

A security device according to claim 1 or 2, characterized in that the fuses (20, 21) are formed as a layer (36) of a material, which is active with respect to at least one physical property, being the layer placed between a contact tongue (30) and a first and second contact means (32, 34), respectively. wherein the contact tab (30) is placed to connect to the batteries of the battery (s) (13a-b) of the battery unit (12), wherein the first contact means (32) is placed to connect with the first terminal (24) of the apparatus (11), and wherein the second contact means (34) is positioned to connect with the second terminal (26) of the apparatus (11).

4. A safety device according to claim 3, characterized in that the electrical conductivity of the active material layer (36) in a direction between the contact tongue (30) and the first and second contact means (32, 34). ), respectively, is considerably reduced to zero, when the temperature of the material exceeds a predetermined upper threshold value and returns, when the temperature of the material decreases to less than a predetermined lower threshold value.

A safety device according to claim 3 or 4, characterized in that the first and second contact means (32, 34) have flat upper surfaces for receiving a respective resilient contact means (24, 26) of the electrical appliance ( eleven) .

A safety device according to claim 5, characterized by a third contact means (42), which is mounted on the contact tongue (30) through an intermediate layer (44) of an electrically insulating material, having a flat upper surface for receiving a third resilient contact means (40) from the electrical apparatus (11), and which is positioned to be connected to a negative side of the battery or electrical cells (13a-b) of the power unit. battery (12), while the contact tab (30) is placed to connect with a positive side of the electric batteries.

7. A security device according to any of the preceding claims, characterized in that the electrical device (11) is a mobile telephone for a cellular mobile telephone system. A rechargeable battery unit (12) with one or more than an electric battery (13a-b) for supplying power to a portable electrical device (11), characterized in that the battery unit (12) comprises a safety device ( 10) according to any of the preceding claims.