EP1085619A1

EP1085619A1 - Current conducting contact pin provided with a ball

Info

Publication number: EP1085619A1
Application number: EP99610056A
Authority: EP
Inventors: Jan-Olof Svensson; Fredrik Hermann
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 1999-09-20
Filing date: 1999-09-20
Publication date: 2001-03-21

Abstract

A current conducting contact pin (1) comprising a housing (4), at least one pin (5) and a spring element (6). The pin (5) has an external end extending beyond the housing (4) and an internal end located inside the housing (4). Means are provided for restricting the extension of the pin (5) outside the housing (4). The pin (5) is slidably located in the housing (4) and the spring element (6) forces the pin (5) to be in its outermost position. The contact pin in characterised in that the external end of the pin (5) comprises a seat (8) in which a ball (7) is rotatably mounted.

Description

The invention relates to a current conducting contact pin comprising a housing, at least one pin and a spring element, said at least one pin having an external end extending beyond the housing and an internal end located inside the housing, means being provided for restricting the extension of the pin outside the housing, said at least one pin being slidably located in the housing and the spring element forcing the pin to be in its outermost position. In particular, the invention relates to a current conducting contact pin for use in electronic equipment, such as a mobile radio station or a communicator.
Today, many electronic devices are provided with exchangeable parts, such as rechargeable batteries. Batteries for such devices are provided with terminals which are brought into contact with the electronic device via contact pins mounted on a PCB (Printed Circuit Board) of the electronic device. The contact pins extend beyond the housing of the electronic device, and the pins are often spring-biased to ensure a firm contact between the battery terminals and the pins.
Generally, a contact pin of the mentioned type comprises a housing, a pin and a spring. The pin has an external end extending beyond the housing and an internal end located inside the housing. The internal end of the pin is provided with an outwardly extending collar that cooperates with an inwardly extending flange of the housing, thereby restricting the extension of the pin outside the housing. The pin is slidably located in the housing and the spring forces the pin to be in its outermost position.
The contact pin is gold plated in order to enhance the conductivity of the contact pin and to ensure a firm contact between the external end of the pin and the battery terminal. However, due to repeated mounting and dismounting of the battery, wear occurs at the external end of the pin and at the battery terminal, since the battery terminal to some extent slides over the end of the pin. The sliding also occurs to some extent even when the battery is mounted due to the play that exists between the different parts. At worst, the gold plating is worn off and the underlying nickel element is exposed, which also means formation of nickel oxide. Eventually, this may lead to interruption of the current flow between the battery and the contact pin.
In order to overcome this problem, a relatively thick layer of gold is normally provided at the external end of the pin.
The object of the present invention is to provide a current conducting contact pin that is less exposed to wear than the known contact pins. This object is achieved by a contact pin as mentioned in the introduction wherein the external end of the pin is provided with a seat in which a ball is rotatably mounted.
Thereby, the battery terminal no longer slides over the external end of the pin but rather rolls over the external end of the pin, causing less wear to occur.
Preferably a conductive lubricant is provided between the seat and the ball which reduces the friction between the seat and the ball. In turn, this reduces the wear even further.
In case of a gold plated contact pin the ball is provided with a thin layer of gold. Due to the reduced wear the gold layer has a thickness of approximally 1.5 µm, which is the recommended thickness of gold plating and which is less than the thickness provided on the known contact pins.
Preferably, the spring element is a helical spring positioned between the bottom of the housing and the proximal end of the pin.
In a preferred embodiment the internal end of the pin has an inclined end face and a second ball is arranged between the helical spring and the internal end of the pin. This structure ensures that a firm contact is achieved between the pin and the housing when the pin is pushed downwards, since the inclined end face causes the pin to be laterally displaced in the housing. This causes the pin to be in firm contact with the housing.
The bottom of the housing can be mounted on a component carrier, such as a PCB, in different ways. In the simpliest embodiment, the bottom of the housing is configured to be surface mounted on the component carrier. The bottom may also be provided with a plug for being plugged into a complementary socket that is mounted on the component carrier, or it may be provided with a plug provided with threads for being arranged into a hole in a current conductive element, such as a PCB.
The current conducting contact pin may also be provided with two pins that extend beyond the housing in opposite directions.
The contact pin according to the invention is preferably mounted in an electronic device which may be a mobile radio station, such as a mobile telephone or a communicator.
It should be emphasized that the term "comprise/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components, but does not preclude the presence or addition of one or more other features, integers, steps components or groups thereof.
The invention will be described in detail in the following with reference to the drawings, in which
Fig. 1 shows a first embodiment of a current conducting contact pin according to the invention,
Fig. 2 shows the first embodiment of a current conducting contact pin according to the invention in contact with a terminal,
Fig. 3 shows a second embodiment of a current conducting contact pin according to the invention,
Fig. 4 shows a third embodiment of a current conducting contact pin according to the invention, and
Fig. 5 shows a fourth embodiment of a current conducting contact pin according to the invention.
In the drawings, similar parts are referred to by the same reference numeral even if these parts belong to different embodiments.
Fig. 1 shows a contact pin 1 being surface mounted on a component carrier, such as a PCB 2, via a soldering material 3. The contact pin 1 comprises a housing 4, a pin 5, a helical spring 6 and a ball 7. The pin 5 has an internal end positioned inside the housing 4 and an external end provided with a seat 8 in which the ball 7 is arranged. The pin 5 is provided with an outwardly extending collar 9 at the internal end thereof, said collar 9 cooperating with an inwardly extending flange 10 of the housing 4 preventing the pin 5 from being removed from the housing 4. The helical spring 6 is positioned between the bottom of the housing 4 and the internal end of the pin 5 and forces the pin 5 to be in its outermost position. The internal end of the pin 5 has an inclined end face 11 and a second ball 12 is arranged between the spring 6 and the inclined end face 11 of the pin 5. This structure accomplishes lateral displacement of the pin 5, whereby a firm contact is established between the collar 9 of the pin 5 and the inner wall of the housing 4 for providing good current conductivity between the two parts. A conductive lubricant is provided between the seat 8 and the ball 7 in order to facilitate the rolling movement of the ball 7 in the seat 8 and in order to ensure current conduction between the ball 7 and the pin 5.
The housing 4, the pin 5 and the ball 7 are preferably gold plated in order to ensure good conductivity of the parts. The thickness of the gold layer is approximally 1.5 µm, which is the recommended thickness.
Fig. 2 shows the current conducting contact pin 1 shown in Fig. 1 in contact with a terminal 13 which e.g. may be a part of a rechargeable battery.
When the battery is mounted on the electronic device provided with the shown contact pin 1, its terminal presses/slides over the external end of the pin 5, i.e. over the ball 7. Since the ball 7 is free to roll in the seat 8, substantially no wear will occur on the surface of the ball 7 or on the terminal 13.
The terminal 13 presses the pin 5 downwards and the helical spring 6 ensures a firm contact between the pin 5 with the ball 7 and the terminal. Thereby, a good current conductivity is ensured from the battery terminal 13 to the PCB 2. The current travels from the battery terminal through the ball 7, via the current conductive lubricant to the pin 5, further through the housing 4 and, finally, via the soldering material 3 to the PCB 2.
The contact pin 1 shown in Figs. 1 and 2 are soldered to a PCB 2 via soldering material 3. However, the contact pin 1 may be connected to the PCB 2 by other means than soldering.
A first alternative is shown in Fig. 3 which shows a contact pin 1 that corresponds to the contact pin 1 shown in Figs. 1 and 2, except for the mounting on the PCB 2. In this embodiment the housing 4 is provided with a plug 14 adapted to be mounted in a socket 15 that is soldered to the PCB 2 by means of a soldering material 3.
In a second alternative the housing 4 is provided with a plug 16 provided with threads for being arranged into a hole 17 in the PCB 2. This is shown in Fig. 4 in which the contact pin 1 corresponds to the contact pin 1 shown in Fig. 1 except for the mounting means. The plug 16 provided with threads extends through a hole 17 in the PCB 2 and a nut 18 is screwed onto the plug 16, thereby fastening the contact pin 1 to the PCB 2.
Other mounting means may also be applied.
Fig. 5 shows a double-ended current conducting contact pin 19 provided with two pins 5 that extend beyond the housing 4 in opposite directions. This contact pin 19 comprises a housing 4 with an opening in each end thereof. A pin 5 extends through each opening, said pin 5 being provided with a seat 8 with a ball 7 at the external end and with a conductive lubricant between the ball 7 and the seat 8 of the pin 5. A helical spring 6 is provided inside the housing 4 between the internal ends of the pins 5, said helical spring 6 forcing the pins 5 to their outermost positions. Each pin 5 is provided with an inclined end face 11 and a second ball 12 is provided between the helical spring 6 and the inclined end face 11 in order to ensure a firm contact between the pin 5 and the housing 4.
The double-ended contact pin 19 may be soldered to a PCB and can be used for transferring current between two exchangeable parts or it can be moulded into a carrier.
The current conducting contact pin 1, 19 according to the invention has been described in connection with exchangeable parts, such as rechargeable batteries. Advantageously, however, the contact pin 1, 19 may also be used in connection with other mounted parts, such as loudspeakers in mobile telephones, since some play always occur between different parts that are not soldered together. The small but inevitable play causes some wear on the surfaces of the terminal and on the end of traditional contact pins to occur. By using a contact pin 1, 19 according to the invention for receiving movements between parts the wear is considerably reduced.
In the embodiments shown a helical spring 6 is provided for pressing the pin 5 to its outermost position. Other spring elements are, however, applicable, e.g. leaf springs. Furthermore, the inclined internal end face 11 of the pin 5 and the second ball 12 between the spring 6 and the inclined end face 11 may be replaced by other means ensuring a good contact between the pin 5 and the housing 4.
Many other modifications may be applied without departing from the scope of the invention.

Claims

A current conducting contact pin (1; 19) comprising a housing (4), at least one pin (5) and a spring element (6), said at least one pin (5) having an external end extending beyond the housing (4) and an internal end located inside the housing (4), means being provided for restricting the extension of the pin (5) outside the housing (4), said at least one pin (5) being slidably located in the housing (4) and the spring element (6) forcing the pin (5) to be in its outermost position, characterised in that the external end of the pin (5) comprises a seat (8) in which a ball (7) is rotatably mounted.
A current conducting contact pin according to claim 1, characterised in that a conductive lubricant is provided between the seat (8) and the ball (7).
A current conducting contact pin according to claims 1 or 2, characterised in that the ball (7) is provided with a thin layer of gold.
A current conducting contact pin according to claim 3, characterised in that the gold layer has a thickness of approximally 1.5 µm.
A current conducting contact pin according to any one of claims 1-4, characterised in that the spring element (6) is a helical spring positioned between the bottom of the housing (4) and the internal end of the pin (5).
A current conducting contact pin according to claim 5, characterised in that the internal end of the pin (5) has an inclined end face (11) and that a second ball (12) is arranged between the helical spring (6) and the internal end of the pin (5).
A current conducting contact pin according to any one of claims 1-6, characterised in that the bottom of the housing (4) is configured to be surface mounted on a component carrier, such as a PCB (2).
A current conducting contact pin according to any one of claims 1-6, characterised in that the bottom of the housing (4) has a plug (14) for being plugged into a complementary socket (15) that is mounted on a on a component carrier, such as a PCB (2).
A current conducting contact pin according to any one of claims 1-6, characterised in that the bottom of the housing (4) has a plug (16) provided with threads for being arranged into a hole (17) in a current conductive element.
A current conducting contact pin according to claim 9, characterised in that the current conductive element is a component carrier, such as a PCB (2).
A current conductive contact pin according to any one of claims 1-6, characterised in that the contact pin comprises a housing (4) provided with two pins (5) that extend beyond the housing (4) in opposite directions.
An electronic device provided with at least one dismountable element, such as a battery, that is in electrical contact with the device through a contact pin (1), characterised in that the contact pin (1) is of a type according to any one of claims 1-11.
An electronic device according to claim 12, characterised in that the electronic device is a mobile radio station, such as a mobile telephone or a communicator.