AU2004325908A1 - Connector bridge - Google Patents

Description

Hans Hatton NAATIAccredited Translator #40081 POWER PLUG BRIDGES The present invention relates to the generically claimed subject matter and thus concerns itself with power plug bridges, especially those having partially-insulated metal contacts. 5 In the manufacture of mains plugs and the like, the metal contacts that arc inserted into the power point or socket, namely plug pins, blade contacts or the like, must be arranged in a geom.etrically-precise manner, that is, they must have the correct alignment in relation to one another, and the exact required projection beyond the plug body. To achieve this, the metal contacts are arranged in a plastic plate prior to attachment of the o10 mains cables, which typically occurs, for example, by crimping, whereupon the entire arrangement is overmolded with PVC to form the plug body. The plastic plate together with the plug pins or blade contacts is known as a plug bridge. Although the safety of a mains plug in service depends significantly on the quality and 15 precision of the plug bridge, the plug bridge is a mass-produced item that must be economical to manufacture and easy to further process. This applies irrespective of a given country's regulations on mains plugs. There are a great number of mainrs plugs with partially-insulated metal contacts. These 20 plugs exhibit bare metal at the opposing end to the plug body, whilst the metal contacts are covered with plastic in the vicinity of the plug body. This has the advantage of preventing a child at play, for instance, from reaching the live metal contacts by means of papcrclips or other such instruments whilst the plug is only half inserted, and thereby suffering a fatal or life-threatening electrical shock. 25 2 Hans Hatton NAATI-Accredited Translator #40081 To date, it has been a very costly process to manufacture plug bridges with partially insulated metal contacts and a plastic plate for fixing same in place, in particular for box or blade-shaped, i.e. non-round metal contacts. It is desirable to bring about a simplification and/or an improvement in this area. 5 The object of this invention is to provide an innovative power plug bridge for commercial use. The achievement of this object is claimed in independent form. Advantageous embodiments may be found in the dependent claims. 10to The essential recognition is that power plug bridges with partially-insulated blade contacts, that is, non-round or flat blade contacts, are in preference manufactured in a multi-step process where the contacts are first provided with an initial insulation, then subsequently arranged in a plastic plate, or the pre-insulated blade contacts are overmolded with plastic to form a plastic base plate, or base plate of the power plug 15 bridge. It should be mentioned that it is particularly advantageous not simply to insert the partially-insulated blade contacts in a prefabricated base plate, but rather to arrange the blade contacts with partial insulation in a holding plate by overmnnolding or insertion. Surprisingly, despite the effort involved in partially insulating the blade contacts, this method does not, or at least not significantly, increase the overall expenditure required to 20 manufacture the power plug bridges; moreover, the possibility of structuring the partial insulation, especially in the area where the plastic plate or base plate of the power plug bridge is to be formed or attached, and by this structuring achieving better positioning in the manufacturing process, enables a higher production rate to be achieved. 3 Hans Halton NAAT-Accrmdited Translator #400e7 In a preferred embodiment, creation of the partial insulation occurs separately from the arrangement of the partially-insulated metal contacts; in other words, a stock. of partially insulated metal contacts is first produced, whereupon these partially-insulated metal contacts are individually oriented prior to processing, and then fed to the actual machine 5 producing the power plug bridges. This has the advantage of splitting up the manufacturing processes so that the entire production does not come to a halt in the event of maintenance being required on a specific machine part. It is practicable and advantageous to provide crimp connections in the top area of the 10 metal contacts, i.e. in the interior of the plug body when these contacts are in use. The crimp connections typically project above the insulation, in particular when the insulation of the metal contact in the region of the plastic plate is shaped to allow easier and/or more precise positioning in the plastic plate; this applies also in cases where the power plug bridge is provided with blade contacts or contact pins, for example earth pins or Is blade-shaped earth contacts, that are not insulated in the region of the socket. The crimp ends are in preference connected to the blade contacts via a tapered extension, whereby the tapered extension typically projects from the plastic insulation, or the widened cross-section extending theretowards in the region of the plastic plate. The 20 provision of a tapered extension above the actual plane of the plastic plate, and therefore above the insulated or plastic-overmolded area of the metal contacts, has the advantage of reliably preventing breakage of the insulation and/or the plastic plate, or splintering off of material at fast production rates, on accounrit of the large dynamic forces at play during crimping. 25 4 Hans Hatton NAATI-Accrsdited Translator #40081 The crimp sleeves, crimp wings or other such crimp contact elements on the blade contact are in preference associated with an insertion or guiding aid that expands in a funnel-shaped manner from the connection or attachment area upwards to the insertion side of the mains flex, thereby facilitating the introduction of the flex to be attached and 5 at the same time significantly reducing the risk of loose strands so that there is no danger of loose strands projecting from the plug body and subjecting the user to a life threatening or fatal electrical shock. The guiding aid is preferably formed on the plastic plate itself and/or mounted thereupon. 1o The partial plastic insulation around the blade contacts preferably serves not only to increase the safety of the mains plug in service, but at the same time can be used to better position the blade contacts in the region of the plastic plate. To this end, a widening of the cross-section can be provided, whereby this cross-sectional widening has, in particular, a thickness corresponding to that of the plastic plate, or perhaps slightly 15 smaller or larger, and is structured across the thickness, for example with grooves, ribs, shoulders, or recesses, the purpose of this structuring being especially to prevent twisting of the partially-insulated, or possibly non-insulated (earthing) blade contacts, in the plastic plate and/or an axial displacement away from the plastic plate, the result of which would be a change in the length of the plug contacts and therewith a possible deviation 20 from the standard. This especially advantageous widening of the cross-section therefore increases the operational safety of the power plug bridges. It is practicable and advantageous to provide the metal contacts, which are typically stamped from sheets of metal or otherwise obtained by bending stamped pieces of metal, 25 with through holes, in particular in the area of the plastic insulation. This contributes to 5 Hans Hatton NAATP.Accredited Transiatot #40081 tile formation of an intimate and secure connection between the metal and insulating plastic, where the metal contact is immovable relative to the insulation. Furthermore, a reduction in weight and a saving in material is achieved. 5 In a preferred variant, the free ends of the metal contacts are formed so as to all be flush with the insulation. This prevents a contact spring or the like in the socket from getting caught on the insulation while the power plug is inserted or withdrawn from the socket, thereby gradually or suddenly destroying the insulation. 10 Protection is also claimed for partially-insulated metal contacts as used in the implementation of the method according to the present invention, these being specially important elements of the invention, without thereby surrendering protection for other relevant elements. 15 Protection is also claimed for power plug bridges according to the present invention itself. It is expected that the inventive power plug bridges will be readily distinguishable from those of the state-of-the-art upon examination of the yield points and/or solidification ranges of the plastic surrounding the metal or blade contacts, and the plastic plate fixing same in place. 20 Further protection is claimed for mains cables having power plug bridges according to the present invention, along with electrical appliances provided with such mains cables. The invention will now be described by way of example in the following drawings. 6 Hans Hatton NAATI-Accredited Translator #40081 Fig. I shows a power plug bridge as per the present invention with two partially-insulated blade contacts, in various stages of manufacture; Fig. 2 shows a power plug bridge according to the present invention with partially-insulated blade contacts and a non-insulated, blade-shaped 5 earthing contact, in various stages of manufacture; Fig. 3 shows an alternative power plug bridge as per the present invention with a plastic plate of smaller surface area and without an associated insertion aid, in various stages of manufacture; Fig. 4 shows a two-pole power plug bridge as per the present invention with a 10 multi-piece plastic plate, in various stages of manufacture; Fig. 5 shows a three-pole power plug bridge according to the present invention in various stages of manufacture; Fig. 6 shows a two-pole power plug bridge according to the present invention in various stages of manufacture; 15 Fig. 7 shows a power plug bridge according to the state of the art. As shown in Fig. 1, a power plug bridge 1, generally labeled as 1 (Fig. I bottom), comprises a partially-insulated blade contact 2 and a plastic plate 3 for fixing same in place, whereby the blade contacts are separately prepared (Fig. I top) and provided with 20 a plastic insulation 2a prior to being arranged in the plastic plate 3. The power plug bridge 1 represents a power plug bridge for a plug with a two-pole earthing pin connection corresponding, for example, to Australian standards. The projection of the plug pins D beyond the plastic plate, the dimensions of the blade 25 contacts 2 with respect to width B and thickness d, etc. are determined from the standard. 7 Hans Hatton NAATI-Accredited Translator #40081 The blade contacts are stamped from suitable copper sheet or the like and exhibit a taper in the central, partially insulating area 2al, as is readily recognizable in Pig. 1 top, in particular on the right-hand blade contact. The blade contacts are provided with through 5 holes 2a2 and 2a3 in the region of the taper 2al, these through holes being dimensioned so as not to, or at least not significantly, reduce the stability of the blade contacts and to allow the hot, not yet solidified plastic material to easily flow through. The end 2b of the plug pins intended for insertion in the power point are rounded off as 1o required by the standard. Above the taper 2al, the metal of the blade contact is provided with a section the thickness k of which corresponds to that of the plastic plate and which tapers to a crimp sleeve end 2d via the extension 2e. The extension 2e transitions into the section 2c via a 15 shoulder 2el, i.e. in other words the extension 2e is as a whole thinner and therefore more flexibly formed than the section 2c. The bevel of the shoulder is particularly evident on the right-hand blade contact in Fig. 1 top but has not been labeled for the sake of clarity. 20 A transition of shape similar to the bevel 2el is also provided at both ends ofthe section 2al, that is, towards the section 2c and the section 2b. The crimp end 2d in the present example takes the form of a crimpable sleeve 2d the diameter of which allows easy insertion of the strands of the cable to be connected, such 25 cable being sufficiently rated for the intended current flow. As an alternative to crimp 8 Hans Hatton NATI-AcOreMdited Translator #40081 sleeves, crimp surfaces or other connection areas, for example areas for a rivet, solder or weld connection, can be provided. The blade contacts in Fig. 1 top are provided with a standardized plastic insulation in the s area of the pin, as shown in Fig. 1 center. Accordingly, a plastic insulation 2a is provided around section 2al and in doing so plastic also penetrates the holes 2a2 and 2a3 or other holes, if present; furthermore, according to the invention, the plastic 2a is shaped as a single piece with a molded area 2c1 surrounding the section 2c. 10 The molded area 2c1 extends all the Way to the extension 2e via the shoulder 2el and is provided with a step 2f towards the socket end of the blade contact that enables the shoulder 2c1 to be supported in a precisely defined position in the injection mold used to form the plastic plate as well as providing a seal against flashing of the polymer injection molding compound and/or enables it to be supported on an pre-manufactured plastic 15 plate. The area between the lower shoulder 2f and the upper side 2g facing towards the crimp sleeve 2d is provided with a recess 2h all the way around it that enables it to engage in a pre-inanufactured plastic plate, or enables liquid, hot plastic injection molding material to flow into it, in both cases for the purpose of axially fixing in place the blade contact relative to the plastic plate. 20 The power plug bridge as per the present invention is manufactured as follows: Firstly the blade contacts are stamped from metal sheet, and the crimp sleeves bent into shape. If desired, it is possible to create the blade contacts not from solid material, but 25 rather as a hollow part formed by bending sheet metal during the stamping operation. 9 Hans Hatton NAATI-Accedited Translator #40081 The finished stamped, or otherwise manufactured metal contacts are then overmolded with plastic material in the first processing step to produce the configuration show in Fig. 1 center. The pre-fabricated, partially-insulated metal contacts are then fed into an injection molding machine where they held in correct orientation and overmolded with plastic material to form the base plate 3. The power plug bridge I is now complete and can be fed into a production line for power cords where the strands of a power cord are attached 10 to the crimp ends 2d, and a plug body, made of PVC or the like, is then molded around the power plug bridge. The recesses in the plastic plate of the power plug bridge 3 allow the PVC material to partially, or possibly fully penetrate the base plate whereby the base plate is precisely positioned in height relative to the plug body and remains so positioned. 15 As shown in Fig. 2, it is also possible to produce three-pole or multi-pole power plug bridges in accordance with the invention. Where it is not necessary to partially insulate a particular blade contact, say in the case of an earth contact as indicated by 4, a shoulder can nevertheless be provided in the region of the plastic plate to facilitate the overmolding of the contact pin to form the plastic plate. In such case the shoulder should 20 be structured in the same manner, or at least in a similar manner, as for the partially insulated blade contacts. Generally, it may be noted that it can be advantageous to provide a shoulder around the plug pins or blade contacts rather than positioning wings 100 formed from metal sheet as shown in Fig. 7, even then when none of the metal contacts of the power plug bridge are provided with a partial plastic insulation. This is 25 considered inventive in itself 10 Hans Hatton NAATI-Accredted Trmnslator #40081 Fig. 2 also shows that an elbow 5 can be provided in the transition region between the extension 2e and the crimp sleeve 2d which facilitates the insertion of the strands by way of a small displacement in geometrical position and/or promotes the dynamic behavior of 5 the metal contacts during the crimping operation_ Fig. 2 further shows that it is possible to first embed, i.e. mold-in, overmold or insert, the partially-insulated plastic sleeves in a plastic plate element 6 and subsequently insert them in a larger plate 7 that may especially have been formed with an insertion aid 8, for 10 example in the shape of a bridge. In regard to the form of the insertion guides 8, we refer the reader to various design possibilities that can be found in other patents filed by the present inventor. Fig. 3 demonstrates that, where necessary, power plug bridges for a variety of plug s15 bodies are obtainable as commercial elements with the aid of the plastic element 6. Fig. 4 shows a power plug bridge that corresponds substantially to that in Fig. 2 but has been formed for a two-pole arrangement. If desired, the insertion aid arrangement can be similar to that required or preferred where there are three mains contacts, regardless of 20 the fact that only two connections have been used. Fig. 5 illustrates the direct embedding of three blade contacts, of which two are partially insulated and one is provided with a plastic shoulder at the height of the plastic plate, in a plastic plate. Ofparticular note is the easily discernible transition line 9a fomed by the 11 Hans Hatton NAATI-Acrite Translator #40081 folding of the metal sheet around the earthing blade contact 9 during the stamping operation. Fig. 6 shows a further two-pole power plug bridge according to the present invention. 5 Fig. 7 shows the state of the art in which the height of the contact pins is determined by the attachments 100 which rest on the bearing surfaces 101 of a plastic plate. This design is disadvantageous in respect to precision and manufacture even then when no partial insulation of the contact pins is required. 10 12

Claims (12)

1. Method for the manufacture of power plug bridges with partially-insulated metal contacts and a plastic plate for fixing same in place, characterized in that the metal contacts take the form of blade contacts that are provided with a partial 5 insulation, said partially-insulated blade contacts being arranged in a plastic plate and/or overrmolded with plastic.

2. Method according to the previous claim, characterized in that the metal contacts are provided with crimp ends.

3. Method according to the previous claim, characterized in that the crimp ends are 10 connected to the contact blade via a tapered extension.

4. Method according to the previous claim, characterized in that an insertion aid is formed for the crimp ends.

5. Method according to any of the preceding claims, characterized in that the plastic plate is provided with an insertion aid to assist the final insertion in the crimping I5 areas of the metal contacts.

6. Method according to any of the preceding claims, characterized in that the plastic insulation of the partially-insulated blade contacts is provided with a widening in cross-section in the region of the plastic plate.

7. Method according to any of the preceding claims, characterized in that the 20 partially-insulated metal contacts are provided with a recess and/or a spring-like extension at the height of the widening in cross-section.

8. Method according to any of the preceding claims, characterized in that the power plug bridge is provided with a blade contact that is non-inrsulated in the socket region, said blade contact being overmolded with plastic in the region of the 25 plastic plate so as to produce a widening in cross-section. 13 Hans Hatton NAATI-AC cr Cdited Translator #40081

9. Method according to any of the preceding claims, characterized in that at least several of the metal contacts have through holes into which plastic can be injected.

10. Method according to any of the preceding claims, characterized in that the metal 5 contacts are tapered in such a way in the region of the plastic insulation, that the insulation is always flush with the free ends of the contacts. 1 I. Blade contact with partial insulation for the manufacture of a power plug bridge according to any of the preceding claims.

12. Power plug bridge with partially-insulated metal contacts and a plastic plate for 10 fixing same in place, wherein, for at least several of the metal contacts, a solidified plastic area separate from the plastic plate is present in the region of the plastic plate.

13. Mains cable with plug possessing a power plug bridge according to any of the preceding claims. 15 14. Electrical appliance with mains cable according to the previous claim. 20 25 14