Improvements relating to electrical plug terminal pins

Abstract

 The present invention relates to an electrical appliance plug pin for a plug bridge of an electrical wall plug, having annular grooves designed so as to improve material strength and reduce manufacturing costs at the same time. There are provided a conventional pin having a cylindrical shank and a short cylindrical portion for connection to a cable termination, with the two cylindrical portions separated by an annular groove milled throughout its length. The milling operation is carried out in an inclined manner, that is the milling tool is provided with a contour which lies in a projection plane that is inclined with respect to the axis of rotation of the milling machine by arranging the spindle unit of the milling tool to spatially modify the orientation of the axis of rotation of the milling tool. The bridge plate of the plug bridge is perpendicular to the axis of the pin in the region of the annular groove and is provided with an improved retention force due to the improved design of the electrical plug pin in the same region.

Description

Technical Field of the Invention

[0001] The present invention relates to an electrical appliance plug pin for a plug bridge of an electrical wall plug, having annular grooves designed so as to improve plug strength and reduce manufacturing costs at the same time. The bridge plate of the plug bridge, as proposed by the present invention, is perpendicular to the axis of the pin in the region of the annular groove and is provided with an improved retention force due to the improved design provided to electrical plug pin in that region.

Background of the Invention / Prior Art

[0002] Given the fact that electrical plug pins are quite well-known to professionals in electrical connection components industry and proved to function satisfactorily for many decades to such an extent that professional world came up to view them as no longer capable of getting improved, there yet exist deficient features to overcome in the field. Although electrical plug pins are accepted in the long run as having reached technical maturity, an approach of the above kind is inadequate in the sense that annular grooves in the electrical plug pins, which are generally relatively small and which do not incorporate appropriate knurlings to ensure stability, pose risk of the pins peeling off from the plug bridge and/or causing the same to slide or displace back and forth towards the plug bridge, which are undesired as these lead to malfunctioning and may extremely be dangerous for the users. In addition to the fact that presently available annular grooves are inadvantageous in the sense that they are yet subject to improvements, taking necessary manhour needed for equipping electrical plug pins with annular grooves and knurlings into consideration is also of great relevancy and any improvement to render manufacturing process faster and electrical contact pins more reliable is still welcome in the electrical components industry.

[0003] Among patents/patent applications present in the technical field of the present invention, the German patent DE 3840140 C2 discloses an electrical plug pin with annular grooves secured within thickness of moulded plastic bridging piece by milled edges or bed of groove.

[0004] In the technical field of the present invention, eliminating stability concerns while simultaneously enhancing manufacturing process, that is, enhancing safety of the product as well as production batches per unit time is a primary target. Another example of the above kind in the same technical field is the German patent DE 19627335 C1, which discloses an electrical plug pin having annular grooves machined in conventional position under head of pin but divided axially into three portions of unequal length. The division of the groove into three rings in succession along the axis, each with its own milled edge, is intended to increase the security of retention of the pin in the axial direction. According to the same, however, the milling operation, as a step of the machining process, is carried out in a plane lying at right angles to the axis of the plug pin, which results in the formation of relatively lower grooves along the rings due to ongoing concerns in relation to material stability. Those skilled in the art will appreciate that the depth of the grooves in the milled portions of the plug pins, as a result of perpendicular milling, will be limited to the material characteristics of the alloy and will hence be exposed to stability concerns. The present invention, however, provides a more improved plug pin equipped with a series of deeper grooves along the ring due to the unique shape given through milling operation so as to enhance material stability and at the same time to ease and speed up manufacturing process. Greatest advantage of the present disclosure over prior art thereby lies in the fact that the security of retention of the pins provided hereby is improved to the extent that the pin is free of immobilisation loss both in radial directions and in axial direction.

Objects of the Invention

[0005] One of the objects of the present invention is to modify the shape of the annular groove section in an electrical plug pin in order to increase the security of retention of the same in both axial and radial directions.

[0006] Another object of the present invention is to provide a more improved plug pin equipped with a series of deeper grooves along the ring due to the special shape given through milling operation at its groove section so as to enhance material stability and to ease and speed up manufacturing process.

[0007] Yet another object of the present invention is to provide deeper grooves, which are not extending along the lateral surface of the pins but along an inclined annular surface formed in between the outermost and the innermost diameters of the pins so as to increase immobilisation against rotation.

[0008] Still a further object of the present invention is to provide a depth vector being greater than the vertical component of the same, though the latter being not greater than those in the prior art that are applied through perpendicular milling, and thus providing the system with deeper grooves without forcing material strength limits.

[0009] Further an object of the present invention is to increase rotational force of workpiece pins by increasing the magnitude of the force exerted on the same during milling operation due to formation of two distinct contact directions on which two distinct force vectors are induced, which is ensured by indined positioning provided between the cutters and the lateral surface of the pins.

[0010] Further an object of the present invention is to increase revolutions per minute (and hence output per unit time) of the workpiece pins secured to a carriage of the milling tool, by increasing rotational force of the same due to exertion of a force at a greater magnitude by movable parts of the milling machine.

[0011] Further an object of the present invention is to increase operation life of the cutters of the milling tool due to inclined working plane producing two distinct contact directions on which two distinct force vectors are induced and a greater force hence exerted on the pins during milling operation.

[0012] Further an object of the present invention is to decrease production losses due to improved material strength provided by deeper grooves, which are cut in an inclined manner.

Summary of the Invention

[0013] According to the present invention, the objects described above are achieved through use of a conventional pin having a cylindrical shank and a short cylindrical portion for connection to a cable termination, with the two cylindrical portions separated by an annular groove milled throughout its length. The milling operation is carried out in an indined manner, that is the milling tool is provided with a contour which lies in a projection plane that is inclined with respect to the axis of rotation of the milling machine by arranging the spindle unit of the milling tool to spatially modify the orientation of the axis of rotation of the milling tool. This milling operation, as a step of the machining process, is improved so as to provide two opposite surfaces perpendicular to which are extending two contact directions on which two distinct force vectors are induced insofar as no loss of immobilisation against rotation incurs.

Brief Description of the Figures

[0014] Accompanying drawings are given solely for the purpose of exemplifying an electrical plug pin terminal whose advantages over prior art were outlined above;

Fig. 1 demonstrates a plane view of the plug pin according to the state of the art.

Fig. 2a demonstrates the view in Fig. 1 while Fig. 2b is demonstrating the annular groove portion in a more detailed manner.

Fig. 3a demonstrates the annular groove portion according to the present invention, the portion referred as "A" being shown in more details in Fig. 3b to reveal the ring details and the specific shape given to every single groove along the ring .

Fig. 4a demonstrates the annular surface provided in between the innermost and the outermost diameters of the pin.

Fig. 4b demonstrates two opposite surfaces perpendicular to which are extending two contact directions on which two distinct force vectors are induced.

Fig. 4c demonstrates an inclined edge groove provided along the rings.

Detailed Description of the Invention

[0015] In the case of a plug pin (1), which is provided with an annular groove section (9) in between a short cylindrical portion (6) and the pin (1) above and below, for a plug link of an electrical connecting plug, especially of an electrical apparatus plug, the link plate (8) of the plug link being a plastic part which is injected or extruded around the plug pin (1) or plug pins in the region of the annular groove (9), in a plane lying generally at right angles to the axis of the plug pin (1). A conventional pin (1), according to the present invention, has a cylindrical shank (2) and a short cylindrical portion (6) for connection to a cable termination (7), with the cylindrical portions (short cylindrical portion, 6 and the pin, 1) separated by an annular groove (9) milled throughout its length so as to comprise a throat (4) under and above which the rings (3, 5) are located in the manner disclosed hereafter. The invention comprises a division of the groove portion (9) into a plurality of rings (3, 5) in succession along the axis, each with its own milled edge with the edge parts being treated on a milling machine in an inclined manner. This modification increases the security of retention of the pin (1) both in radial directions and in the axial direction.

[0016] According to the present invention, the milling operation is carried out in an inclined manner, that is the milling tool is provided with a contour which lies in a projection plane that is inclined with respect to the axis of rotation of the milling machine by arranging the spindle unit of the milling tool to spatially modify the orientation of the axis of rotation of the milling tool. Accordingly, electrical plug pins (1), which are secured to a carriage of a milling machine, are treated in the manner that the movable parts of the milling machine cut the terminal pins (1) to provide them with inclined edge grooves (10) along the rings (3, 5) instead of rectangular edge ones having right angled edges. Besides, the grooves (10) along the rings (3, 5) are not designed so as to extend parallel to the longitudinal axis of the pin (1) and lye on the lateral surface of the same, but to lye on an annular surface (13) inclined in between the outermost and the innermost diameters of the pin (1). In other words, the protruding portions of the grooves (10) along the rings (3, 5) do not protrude radially and the axis on which said protruding portions extend is not juxtaposed to the longitudinal axis of the pin (1).

[0017] In this way, both the axis along which the protruding portions of every single groove (10) extends is given indination with reference to the longitudinal axis of the pin (1) and every single groove (10) has inclined opposite surfaces (11) so as to form a uniform triangle shape (Fig. 3). This unique design allows increasing immobilisation against rotation and ensuring the security of retention of the pin (1) in the plug plate (8) both in axial and radial directions due to formation of a series of deeper grooves (10). On the other hand, since this arrangement provides a depth vector being greater than the vertical component of the same, the same provides the system with deeper grooves (10) without exceeding material strength limits, which is the most restricting factor in the manufacturing process.

[0018] The indined shape given to grooves (10) in the form described above is achieved through position adjustment of the cutters in a plane that is not perpendicular to the longitudinal axis of the pin (1). In addition, the workpiece pins are treated in a bilateral way so as to form grooves with every single groove (10) along the rings (3, 5) having both of its opposite surfaces (Fig. 4a, 11) given indination at once, thus resulting in the formation of two distinct contact directions juxtaposed to the surface (11) normals of the grooves (10), on which two distinct force vectors are induced.

[0019] For the reason that the force exerted by the movable parts of the milling machine is inclined in the manner described above, the ultimate shape given to both of the opposite surfaces (11) of every single groove (10) along the rings (3, 5) is inclined with reference to the surface normal of the inclined annular surface (13) formed in between the outermost and the innermost diameters of the pins (1). Since the inclined milling operation form two distinct contact directions on which two distinct force vectors are induced, the magnitude of the force exerted on the pins (1), that is to say the rotational force, is also increased along with revolutions per minute and hence output per unit time.

[0020] The latter also increases operation life of the cutters of the milling tool due to an improved material strength allowing exertion of a greater force magnitude on the pins (1), provided by the inclined working plane producing two distinct contact directions. Furthermore, the improved material strength has also the positive effect to eliminate production losses along milling operation.

[0021] Another aspect to enhance the security of retention of the pins (1) in the plug plate (8) according to the present invention lies in the fact that the outermost parts (12) of the protruding edges of the grooves (10) goes slightly beyond the outermost diameter of the pin (1) so as to form an additional physical barrier impeding free movement of the pins (1) in both axial and radial directions.

Claims

1. An electrical plug pin provided with an annular groove portion (9) for a plug link of an electrical connecting plug, especially of an electrical apparatus plug, the link plate (8) of the plug link being a plastic part which is injected or extruded around the plug pin or plug pins in the region of the annular groove (9) characterised in that the annular groove section (9) comprises;
   at least two rings (3, 5) in succession along the longitudinal axis of the pin (1), lying on annular surfaces (13) inclined in between the outermost and the innermost diameters of the pin (1).

2. An electrical plug pin according to the Claim 1, wherein the opposite surfaces (11) of each groove (10) along said rings (3, 5) are inclined to form inclined edge grooves (10) so as to form uniform triangle shape grooves (10).

3. An electrical plug pin according to the Claim 1 or 2, wherein the outermost parts (12) of the protruding edges of the grooves (10) goes slightly beyond the outermost diameter of the pin (1) at the outermost section of the rings (3, 5) so as to form an additional physical barrier impeding free movement of the pins (1) in both axial and radial directions.

Amended claims

Amended claims in accordance with Rule 86(2) EPC.

1. An electrical plug pin provided with an annular groove portion (9) for a plug link of an electrical connecting plug, especially of an electrical apparatus plug, the link plate (8) of the plug link being a plastic part which is injected or extruded around the plug pin or plug pins in the region of the annular groove (9) characterized in that the annular groove section (9) comprises;
   at least two rings (3, 5) in succession along the longitudinal axis of the pin (1), lying on annular surfaces (13) inclined in between the outermost and the innermost diameters of the pin (1) and comprising grooves or knurlings (10) extending radially on said annular surfaces (13).

2. An electrical plug pin according to the Claim 1, wherein a plain surface is provided in between each consecutive pair of grooves (10) on said annular surfaces (13).

3. An electrical plug pin according to the Claim 1, wherein the opposite surfaces (11) of each groove (10) along said rings (3, 5) are inclined to form inclined edge grooves (10) so as to form uniform triangle shape grooves (10).

4. An electrical plug pin according to the Claims 1 or 2, wherein the outermost parts (12) of the protruding edges of the grooves (10) goes slightly beyond the outermost diameter of the pin (1) at the outermost section of the rings (3, 5) so as to form an additional physical barrier impeding free movement of the pins (1) in both axial and radial directions.

Drawing