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(11) | EP 0 018 800 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Manufacture of tapered bodies and electric connector receptacles made thereby |
| (57) A tapered body with edge portions (such as channels 1,2) of uniform cross-section
united by a tapered web 3 are made from an extruded blank with a web of uniform width.
This is formed between press tools over an area 8 so asto increase its width. If the
web is planar, the press tools reduce the thickness of the area 8; if it is curved
they may instead (oralso) reduce its curvature. The width of this area 8, and/or the
reduction in thickness or curvature or both, vary along the length of the blank so
as to produce the required taper. The example is an electric connector receptacle, and is simultaneously formed with ribs 12 for engaging a locking projection provided on the corresponding wedge. |
[0001] This invention relates to the manufacture of tapered bodies of ductile material comprising two parts each of uniform cross-section extending along opposite sides of and united by at least one web that is wider at one of its ends than the other.
[0002] An important application of the invention is in making receptacles for electric tapping connectors in which the parts of uniform cross-section are channels facing inwardly to receive separate electric conductors that are secured and electrically connected by a wedge driven between them.
[0003] Such bodies can.be made by casting, but for many purposes the mechanical properties of metal (or other ductile material) that has been worked are much superior to cast material. Machining would be prohibitively expensive, and the current technique of bending an initially flat blank to form the parts of uniform cross-section restricts the cross-sectional shapes it is practicable to use (and is applicable only to shapes with a single web).
[0004] In the method of the invention, a blank comprising two parts of uniform cross-section extending along opposite sides of and united by at least one web of uniform width is first extruded; and then the web or each of the webs is formed between press tools acting on it to an extent that varies and/or over an area that tapers along the length of the blank so as to increase its width to an extent that varies along the length of the blank.
[0005] Preferably the web of the extruded blank is planar and in this case the press tools will reduce its thickness to an extent that varies and/or over an area that tapers along the length of the blank.
[0006] If however the extruded blank were formed with'a curved web, it would be possible, as an alternative (or a supplement) to reducing its thickness, for the press tools to reduce the curvature of the web to an extent that varies and/or over an area that tapers along the length of the blank; and it will be understood that when the area tapers the curvature can be completely removed over that area.
[0007] It will be apparent that a plurality of blanks may be extruded in a continuous length and subsequently sheared or sawn from one another.
[0008] Preferably the area of reduced thickness or reduced curvature (or each of the areas if there is more than one) is defined by a raised area on one of the press tools (or corresponding raised areas on both of them), which will ordinarily be approximately triangular with its base at the wider end of the finished body. When the thickness is to be reduced, the raised area is preferably flat or inclined, and preferably the edges of the.raised area are oblique.
[0009] When the product is an electric connector receptacle into which a co-operating wedge will enter to secure conductors, it is preferably also formed in the pressing operation with ribs or other formations for engaging a projection on the wedge to increase resistance to slackening of the wedge.
[0010] The invention is especially applicable to articles of heat-treatable aluminium alloys, which are extruded in nominally half-hard condition, cooled slowly (e.g. in still air) to avoid age-hardening, and heat-treated to the TF condition after forming. It can however be used effectively with other ductile materials, such as for example copper, aluminium bronze and other copper alloys; in some cases the blank could incorporate more than one material.
[0011] The invention will be further described, by way of example, with reference to the drawings in which:
Figure 1 is an enlarged end-view of an extruded blank;
Figure 2 is a perspective view of a press tool;
Figures 3 and 4 are an end view and a front view of a finished connector receptacle;
Figure 5 is a cross-section in the line V-V in figure 3; and
Figures 6 and 7 are cross-sections on the lines VI-VI and VII-VII respectively in figure 5;
Figure 8, 9 and 10 are mutually perpendicular views of a wedge for use with the receptacle of figures 3-7;
Figure 11 is a cross-section on the line XI-XI in figure 8;
Figure 12 is an enlarged cross-section on the line XII-XII in figure 10;
Figure 13 is a view, corresponding to figure 5, of a modified design of receptacle; and
Figures 14 and 15 are isometric sketches of two further designs of receptacle.
[0012] In the manufacture of the receptacle of figures 2 to 7, standard heat-treatable aluminium alloy HE30 is first extruded to the cross-section shown in figure 1 and comprising two channel portions 1, 2 of any desired cross-section and a planar connecting web 3. The channel portions can usefully be formed with splines 4 or grooves and this is advantageous for some electrical connector receptacles. The extrudate is cooled in still air and then cut into individual blanks.
[0013] Each blank is then positioned in turn, open side down, on a tool of the form shown in figure 2, with the web 3 on top of the tool, the flanges 5,5 loosely received in channels 6,6 in the tool, and an end of the blank against a stop surface 7 on the tool. The blank is now pressed onto the tool using a flat co-operating tool (not shown in the drawings) to reduce its thickness over the area 8 (figures 5-7). Both the width of the reduced area and the extent of reduction increase steadily from the line 9 to the line 10. The effect of the deformation is to introduce a taper of about eight degrees between the two channels.
[0014] Preferably the tool is formed with grooves 11, as shown in figure 2, to form ribs 12 of sawtooth or other suitable profile extending transversely across the area 8 for reasons explained below.
[0015] After forming the now-tapered receptacle is put through the standard heat-treatment to convert it to the TF condition, namely solution treating at 520-530 C followed by quenching in cold water and precipitation heat-treatment at 1800C for 5-6 hours.
[0016] At any convenient stage of the manufacturing process, exposed sharp edges and especially the edges 13 that will engage the conductors in use are desirably chamfered.
[0017] The co-operating wedge, shown in figures 8-12, is die-cast and has concave wedge faces 14 comprising a main section 15 (figure 10) with a taper angle substantially the same as the taper angle of the receptacle merging into a lead-in section 16 with a slightly larger taper angle. All corners 17 adjoining the wedge faces are generously radiussed.
[0018] The side faces 18 of the wedge are slightly convex and each bears at the wider end a ribbed projection 19, so that whichever way up the wedge is inserted in the receptacle, the ribs 12 will be engaged by one of the projections 19. In the preferred design shown, the ribs of projection 19 correspond in spacing and broadly in shape to the recesses between the ribs 12, but the ribs of 19 are of uniform height. When the wedge is driven home, the ribs interlock to increase resistance to slackening of the wedge.
[0019] The modified receptacles shown in figure 13 differs in the shape of the area 8; other, similar, variations may be made.
[0020] Figures 14 and 15 illustrate the use of an extruded blank with a curved web; the blanks are of the shape shown in dotted lines and are the same in both cases. In the receptacle of figure 14, the-press tools act on the triangular area 20 and reduce it to a planar (but oblique) shape, while the areas 21 remain curved substantially as extruded. In that of figure 15, two triangular areas 22 are flattened until they are each coplanar with the contiguous side of the channels 1, 2 respectively and a central triangular area 23 remains curved (though displaced from its original position, except at the extremity of its wide end).
1. A method of manufacturing a tapered body of ductile metal comprising two parts
each of uniform cross-section extending along opposite sides of and united by at least
one web that is wider at one of its ends than the other, the method being characterised
by the steps of
(i) extruding a blank comprising two parts of uniform cross-section extending along opposite sides of and united by at least one web of uniform width; and then
(ii) forming the web, or each of the webs, between press tools acting on it to an extent that varies and/or. over an area that tapers along the length of the blank so as to increase its width to an extent that varies along the length of the blank.
.2. A method as claimed.in.Claim 1 characterised in that the press tools reduce the
thickness of the web to an extent that varies and/or over an area that tapers along
the length of the blank.
3. A method as claimed in Claim 1 in which the extruded blank is formed with a curved
web characterised in that the press tools reduce the curvature of the web (with or
without reducing its thickness) to an extent that varies and/or over an area that
tapers along the length of the blank.
4. A method as claimed in any one of the preceding claims characterised in that the
area of reduced thickness or reduced curvature is defined by a raised area on one
of the press tools, or by corresponding raised areas on both of them.
5. A method as claimed in any one of the preceding claims in which the ductile metal
is a heat-treatable aluminium alloy, characterised in that the alloy is extruded in
a nominally half-hard condition, cooled slowly to avoid age-hardening before the forming
step, and heat-treated to the TF condition after forming.
6. An electric connector receptacle made by the method claimed in any one of Claims
1-5.
7. An electric connector receptacle as claimed in Claim 6, characterised in that the
connector receptacle is formed in the pressing operation with ribs or other formations
for engaging a projection on a co-operating wedge to increase resistance to slackening
of the wedge.