DE112004003018B4 - Method for manufacturing plug bridges, knife contacts, plug bridges, power cords and electrical appliances - Google Patents

Abstract

Method for manufacturing connector bridges (1) for mains plugs with partially insulated metal contacts and a plastic plate (3, 7) fixing them, wherein knife contacts (2) are provided as metal contacts, a partial plastic insulation (2a) is produced on them by overmolding, and the partially insulated knife contacts (2) are arranged in the plastic plate (3; 7) and overmolded with plastic, characterized in that the plastic insulation (2a) of the partially insulated knife contacts (2) in the area of the plastic plate (3; 7) is formed with a cross-sectional expansion (2c1), namely with a structuring over the thickness (k) of the plastic plate (3; 7).

Description

The present invention relates to the claimed subject matter and thus deals with plug bridges, in particular with those having partially insulated metal contacts.

In the manufacture of power plugs and similar devices, the metal contacts that penetrate a socket or outlet—that is, plug pins, blade contacts, or the like—must be arranged with geometric precision, meaning they must have the correct alignment relative to each other and the exact projection beyond the handle body. To ensure this, the metal contacts are arranged in a plastic plate before the power cords are attached, typically by crimping, for example. The entire assembly is then encased in PVC to form the handle body. The plastic plate with the plug pins or blade contacts is called the plug bridge.

Although the safety of the power plug during use depends significantly on the quality and precision of the connector bridge, the connector bridge is a mass-produced part that is inexpensive to manufacture and must allow for easy further processing. This applies regardless of the regulations for power plugs in force in any given country.

There are many types of power plugs where the metal contacts are partially insulated. In these plugs, only the end furthest from the handle is exposed metal, while the contacts near the handle are encased in plastic. This has the advantage that, for example, children playing with a plug that is only partially inserted cannot accidentally touch live metal contacts with paper clips or other tools and suffer a fatal or life-threatening electric shock.

Until now, the production of connector bridges with partially insulated metal contacts and a plastic plate fixing them in place has been an extremely complex process, especially for box-shaped or knife-edge-shaped, i.e., non-circular, metal contacts. It is desirable to be able to simplify and/or improve this process.

From the US 2003/0 148 665 A1 A connector bridge with partially insulated knife contacts is known, wherein a region of the knife contacts to be insulated is recessed around its circumference and a through-opening is provided between the opposite sides, through which plastic material is to flow during injection molding. The previously known knife contacts are intended to be arranged in a mold and encased.

From the GB 2 337 875 A A knife contact made from folded sheet metal is known, whereby it is proposed to apply insulating material to the sheet metal before the knife contacts are folded from the sheet metal piece.

From the GB 2 186 747 A A plug contact is known which is used as a ground contact and is provided with a plastic collar, wherein the plastic collar can be inserted into a stepped hole provided in a pre-made plug body base part.

From the DE 197 30 972 C1 A housing component of an electronic valve control unit is known, comprising a plastic carrier plate, a printed circuit board, and a connector pin anchored in the carrier plate and soldered to the printed circuit board. The connector pin has a tapered section between the carrier plate and the printed circuit board, and this tapered section forms a relief loop to compensate for gravitational forces. A cavity is formed in the carrier plate around the tapered section to act as a deformation zone. The overmolding of connector pins with plastic to form a pre-molded part is described.

From the WO 2004/008587 A1 It is known to use a separately manufactured sleeve that can be slid onto sheet metal elements to insulate certain areas of a knife contact.

From the US 2003/0 027 459 A1 It is known to form insulating rings around conductive knife contacts. The knife contacts have indentations in the metal, and these indentations allow them to be anchored in a power supply housing or similar device.

From the DE 100 10 339 A1 A connector bridge with contact pins is known which can be fitted with connector pins in such a way as to comply with different standards. An insertion aid can be assigned to the connector pins.

Furthermore, in the GB 2 165 100 A and US 6 527 596 B1 Connector bridges revealed.

The object of this invention is to simplify and/or improve the manufacture of plug bridges with partially insulated metal contacts and a plastic plate fixing them.

This problem is solved by the features of claim 1 and the further independent claims. Preferred embodiments are found in the dependent claims.

The key finding is that connector bridges with partially insulated blade contacts, i.e., non-circular or flat cutting contacts, are preferably manufactured using a multi-stage process. This involves first applying an initial layer of insulation, followed by assembling the contacts in a plastic plate or overmolding them with plastic to form the plastic or connector bridge base plate. It should be noted that it is particularly preferred not to simply insert the partially insulated blade contacts into a pre-made base plate, but rather to overmold or insert the partially insulated blade contacts into a mounting plate. Surprisingly, despite the additional work required for partial blade contact insulation, the overall effort for connector bridge manufacturing does not increase, or at least not significantly. Instead, the ability to structure the partial insulation, particularly in the area of the plastic plate or connector bridge base plate to be formed or attached, and thereby improving positioning during the manufacturing process, allows for high production cycle times.

According to the invention, the formation of the partial insulation is provided separately from the arrangement of the partially insulated metal contacts in the plastic plate; in other words, a supply of partially insulated metal contacts is first created, and these partially insulated metal contacts are then separated, aligned, and fed to the actual connector-forming machine before processing. This has the advantage that manufacturing processes are staggered and, if necessary, maintenance on one machine component does not stop the entire production.

It is possible and advantageous to provide the metal contacts with crimp terminals in their upper area, i.e., on the inside of the connector body during use. The crimp terminals will typically protrude above the insulation, especially if the metal contact insulation in the area of the plastic plate is formed with a contour that allows for easier and/or more precise positioning within the plastic plate; this also applies to any uninsulated blade contacts or contact pins, such as grounding pins or grounding contact edges, that may be provided on the connector bridge in the socket area.

The crimp ends are preferably connected to the contact blades via a tapered extension, with the tapered extension typically protruding from the plastic insulation or the cross-sectional expansion within the plastic sheet area that transitions into it. Providing a tapered extension above the actual plastic sheet plane, and thus above the insulated or plastic-encapsulated area of the metal contacts, has the advantage that, even at high cycle rates (i.e., high production speeds), the high dynamic forces acting during crimping reliably prevent the insulation and/or the plastic sheet from breaking or material from chipping.

The crimp sleeves, crimp wings, or other crimp contact elements on the contact knife are preferably associated with an insertion or feeding aid that widens upwards from the connection or stop area towards the insertion side of the mains connection wire in an approximately funnel-shaped manner. This facilitates the insertion of the wire to be crimped and significantly reduces the risk of protruding wires, thus eliminating the danger of protruding wires from the handle body and potentially causing a life-threatening or fatal electric shock to the user. The insertion aid is preferably molded onto and/or attached to the actual plastic plate.

The partial plastic insulation around the blade contacts preferably serves not only to increase safety when using the power plugs, but can also be used to better position the blade contacts within the plastic plate. This involves a cross-sectional expansion, the thickness of which corresponds to that of the plastic plate or, at most, is slightly smaller and/or larger. Furthermore, a textured surface, such as grooves, ridges, protrusions, or indentations, is provided across this thickness. This textured surface prevents the partially insulated, or possibly uninsulated (grounding), blade contacts from twisting within the plastic plate and/or from axial displacement away from the plastic plate, which would otherwise result in a change in the plug contact lengths and thus a potential deviation from the standard. This particularly preferred cross-sectional expansion therefore increases the operational reliability of the plug bridge.

It is possible and preferred to use metal contacts, which are typically stamped from sheet metal and optionally obtained by bending stamped sheet metal parts, particularly in the area of plastic insulation. The insulation is provided with through-holes. This helps to create a tight and secure connection between the metal and the insulating plastic, where the metal contact is not movable against the insulation. At the same time, the weight is reduced and the material required is decreased.

In a preferred embodiment, the exposed metal contact ends are generally formed flush with the insulation. This prevents a contact spring or similar component from becoming stuck to the insulation in the socket when the plug is inserted or removed, thus preventing gradual or sudden damage to the insulation.

Protection is also claimed for partially insulated metal contacts for carrying out the method according to the present invention as particularly relevant elements of the invention, without thereby foregoing protection for other relevant elements.

Protection is also claimed for connector bridges according to the present invention itself. It can be estimated that, for example, by considering the yield strength and/or solidification zones of the plastic around the metal or knife contacts and the plastic plate fixing them, the connector bridges according to the invention are readily distinguishable from those of the prior art.

Further protection is claimed for power cords with plug bridges according to the present invention as well as for electrical devices on which corresponding power cords are provided.

• 1 eine Steckerbrücke der vorliegenden Erfindung mit zwei partiell isolierten Messerkontakten in verschiedenen Fertigungsschritten;
• 2 eine Steckerbrücke gemäß der vorliegenden Erfindung mit partiell isolierten Messerkontakten und einem nicht isolierten Erdungsmesserkontakt in verschiedenen Fertigungsschritten;
• 3 eine alternative Steckerbrücke der vorliegenden Erfindung mit einer flächenmäßig kleineren Kunststoffplatte und ohne zugehörige Einführhilfe in verschiedenen Fertigungsschritten;
• 4 eine zweipolige Steckerbrücke der vorliegenden Erfindung mit einer mehrstückigen Kunststoffplatte in verschiedenen Fertigungsschritten;
• 5 eine dreipolige Steckerbrücke gemäß der vorliegenden Erfindung in verschiedenen Fertigungsschritten;
• 6 eine zweipolige Steckerbrücke gemäß der vorliegenden Erfindung in verschiedenen Fertigungsschritten;
• 7 eine Steckerbrücke nach dem Stand der Technik.

The invention will below be described only by way of example with reference to the drawing. This drawing shows:

• 1 a connector bridge of the present invention with two partially insulated knife contacts in different manufacturing steps;
• 2 a connector bridge according to the present invention with partially insulated knife contacts and a non-insulated grounding knife contact in various manufacturing steps;
• 3 an alternative connector bridge of the present invention with a smaller plastic plate and without an associated insertion aid in various manufacturing steps;
• 4 a two-pole connector bridge of the present invention with a multi-part plastic plate in various manufacturing steps;
• 5 a three-pole connector bridge according to the present invention in various manufacturing steps;
• 6 a two-pole connector bridge according to the present invention in various manufacturing steps;
• 7 a state-of-the-art connector bridge.

After 1 includes a connector bridge generally designated 1 ( 1 (below) partially insulated knife contacts 2 and a plastic plate 3 fixing them, wherein the knife contacts 2 are provided ( 1 above) and are provided with the plastic insulation 2a before being arranged in the plastic plate 3.

The connector bridge 1 is a connector bridge 1 for a two-pole grounding pin connection for a plug, for example, according to Australian standards. The projections of the connector pins D beyond the plastic plate 3, the dimensions of the blade contacts 2 in width B and thickness d, etc., are standardized.

The knife contacts 2 are stamped from suitable copper sheet or the like and have a taper in their central, partially insulated area 2a1, as shown in 1 This is particularly evident on the right-hand knife contact 2. The knife contacts 2 are provided with through holes 2a2 and 2a3 in the area of their tapering 2a1, which are dimensioned such that the stability of the knife contacts 2 is not, or at least not significantly, impaired and that the flow of hot, not yet solidified plastic material is readily possible.

At end 2b, which is intended for insertion into a socket, the plug pins are tapered in accordance with standards.

Above the taper 2a1, a section 2c corresponding to the thickness k of the plastic plate 3 is provided in the metal of the knife contacts 2, which tapers towards a crimp end 2d via a projection 2e. The projection 2e transitions into section 2c via a shoulder 2e1; in other words, the projection 2e is thinner overall and therefore more flexible than section 2c. The chamfer of the shoulder 2e1 is particularly evident at the right knife contact 2. 1 The image above can be seen, although for the sake of clarity it has not been provided with a reference mark.

A transition designed according to the chamfer 2e1 is also provided at both ends of sections 2a1, i.e. towards section 2c and section 2b.

The crimp end 2d is designed as a crimpable sleeve 2d, which has a diameter into which the strands of a cable of sufficient thickness for the intended current flow can easily be inserted. Alternatively to crimp sleeves 2d, crimp surfaces or other connection areas could also be provided, for example, areas for riveting, soldering, or welding connections.

The knife contacts 2 of 1 The pin area at the top is now equipped with a standard-compliant plastic insulation 2a, which is in 1 The section 2a1 is shown in the center. The plastic insulation 2a is provided around section 2a1, with the plastic also penetrating through holes 2a2 and 2a3, or optionally further holes; furthermore, according to the invention, the plastic 2a is formed integrally with a molded area 2c1 around section 2c.

The shaped portion 2c1 (also referred to as projection 2c1) extends over the shoulder 2e1 towards projection 2e and is provided with a step 2f towards the socket end of the blade contact 2. This step allows projection 2c1 to rest in a precisely defined position on an injection mold used to form the plastic plate 3, sealing against the escape of injection-molded plastic material, and/or to rest on a finished plastic plate 3. The area between the lower shoulder 2f and the upper surface 2g facing the crimp sleeve 2d is provided with a circumferential groove 2h. This groove ensures that projection 2c1 snaps into a finished plastic plate 3 or allows liquid, hot injection-molded plastic material to flow into the groove, thus providing axial fixation of the blade contacts 2 relative to the plastic plate 3 in both cases.

• Zunächst werden die Messerkontakte 2 aus Metallblech gestanzt und dabei die Crimphülsen 2d in Form gebogen. Gegebenenfalls ist es möglich, die Messerkontakte 2 nicht aus Vollmaterial zu bilden, sondern als Hohlkörper durch Umbiegen von Blech während des Stanzvorganges.

The connector bridge 1 of the present invention is manufactured as follows:

• First, the knife contacts 2 are stamped from sheet metal, and the crimp sleeves 2d are bent into shape at the same time. If necessary, the knife contacts 2 can be formed not from solid material, but as hollow bodies by bending sheet metal during the stamping process.

The finished stamped or otherwise manufactured metal contacts 2 are then overmolded with plastic material in a first step, whereby the in 1 The training shown in the middle results.

The pre-produced, partially insulated metal contacts 2 are then fed into an injection molding machine, where they are held in the correct orientation and overmolded with plastic material to form the base plate 3. The connector bridge 1 is then complete and can be fed into a mains connection cable production line, where strands of a mains connection cable are crimped onto the crimp ends 2d and subsequently a handle body made of PVC or the like is molded around the connector bridge 1. Recesses provided in the connector bridge plastic plates 3 allow the PVC material to penetrate the base plate 3 and, if necessary, to pass through it, thus positioning the base plate 3 precisely at its correct height relative to the handle body.

After 2 Is it possible to also provide three-pole or multi-pole connector bridges 1 according to the invention? If individual blade contacts 2 do not need to be partially insulated, for example because they are grounding contacts, as indicated in 4, a projection 2c1 can nevertheless be provided in the area of the plastic plate 7, which facilitates overmolding of the contact pins 2 to form the plastic plate 7. The projection 2c1 is then to be structured in the same or at least a similar way as for the partially insulated blade contacts 2. In general, it should be noted that it can be advantageous to use positioning wings 100 instead of those formed from sheet metal in 7 As shown, an approach 2c1 is also provided for the plug pins or knife contacts 2 even if none of the metal contacts 2 of the plug bridge 1 are provided with partial plastic insulation 2a. This is considered inventive in itself, but is not claimed here.

2 It also shows that a bend 5 can be provided in the transition area between the prong 2e and the crimp sleeve 2d, which facilitates the feeding of the strands by slightly shifting the geometric location and/or promotes the dynamic behavior of the metal elements during the crimping process.

2 The invention further shows that it is possible to first embed the partially insulated metal contacts 2 in a plastic plate element 6, i.e., to encapsulate or overmold them, or to insert them into such an element, and then subsequently to insert this element into a larger plate 7, which may be designed, for example, in a bridge shape, with an insertion aid 8. Regarding the design of the insertion aids 8, reference is made to various embodiments as described in other applications of the present inventor.

3 shows that, if necessary, plug bridges 1 for different handle body shapes are available as marketable elements using the plastic plate element 6.

4 shows a connector bridge 1, which is largely the same as that of 2 It corresponds to, but is designed for a two-pole arrangement. If desired, an insertion aid 8 can, regardless of the use of only two terminals, nevertheless correspond to that required or preferred for three mains connection contacts.

5 Figure 1 shows the direct embedding of three knife contacts 2, two of which are partially insulated and one of which is provided with a plastic extension 2c1 in the height range of the plastic plate 3, into a plastic plate 3. It should be noted that the dividing line 9a is very clearly visible at the grounding knife contact 9, which results from folding over a metal sheet during the punching process.

6 shows another two-pole connector bridge 1 according to the present invention.

7 Figure 1 shows the state of the art, in which the height of the contact pins is determined by projections 100 that are mounted on support surfaces 101 on a plastic plate. This type of design is disadvantageous with regard to precision and manufacturing, even if partial insulation of the contact pins is not required.

Claims (13)

Method for manufacturing connector bridges (1) for mains plugs with partially insulated metal contacts and a plastic plate (3, 7) fixing them, wherein knife contacts (2) are provided as metal contacts, a partial plastic insulation (2a) is produced on them by overmolding, and the partially insulated knife contacts (2) are arranged in the plastic plate (3; 7) and overmolded with plastic, characterized in that the plastic insulation (2a) of the partially insulated knife contacts (2) in the area of the plastic plate (3; 7) is formed with a cross-sectional expansion (2c1), namely with a structuring over the thickness (k) of the plastic plate (3; 7). Method according to the preceding claim, characterized in that grooves (2h), ribbing, projections and/or indentations are formed for structuring. Method according to the preceding claim, wherein the connector bridge (1) is manufactured with knife contacts (2) having crimp ends (2d) and an insertion aid (8) is formed for the crimp ends (2d). Method according to one of the preceding claims, characterized in that the plastic plate (3; 7) is provided with an insertion aid (8) to support the insertion of the stranded wire into crimp areas of the knife contacts (2). Method according to one of the preceding claims, characterized in that plastic is injected through through holes (2a2, 2a3) present in at least some of the knife contacts (2). Knife contact (2) with a partial insulation (2a) for producing a connector bridge (1) having a plastic plate (3; 7) according to a method of the preceding claims, wherein a partial plastic insulation (2a) is produced on the knife contact (2) by overmolding, which in the area of the plastic plate (3; 7) is provided with a cross-sectional extension (2c1) which has a structure over the thickness (k) of the plastic plate (3; 7). knife contact (2) after Claim 6 , characterized in that a spring-like projection is provided at the level of the cross-sectional expansion (2c1) at the partially insulated knife contact (2). Knife contact (2) according to one of the two preceding claims, characterized in that it has a crimp end (2d). Knife contact (2) according to the preceding claim, characterized in that the crimp end is formed via a tapered projection (2e) on the knife contact (2). Procedure according to one of the Claims 1 until 5 or knife contact (2) after one of the Claims 6 until 9 , characterized in that the knife contacts (2) in the area of the plastic insulation (2a) are tapered in such a way that the plastic insulation (2a) is generally flush with the free contact ends. Connector bridge (1) with partially insulated knife contacts (2) after one of the Claims 6 - 10 , wherein in the area of the plastic plate (3; 7) for at least some of the knife contacts (2) there is a plastic area (6) that has solidified separately from the plastic plate (3; 7). Power cord with a plug that has a plug bridge (1) to Claim 11 exhibits. Electrical appliance with a mains cable to Claim 12 .