GB2244946A

GB2244946A - Die-and-punch apparatus for joining sheet metal

Info

Publication number: GB2244946A
Application number: GB9103548A
Authority: GB
Inventors: Robin Rennicks
Original assignee: FAIRACRE Ltd
Current assignee: FAIRACRE Ltd
Priority date: 1990-06-01
Filing date: 1991-02-20
Publication date: 1991-12-18
Also published as: ZA911432B; GB9103548D0; IE61054B1; IE901992A1

Abstract

The apparatus comprises a punch 2 arranged for reciprocating movement along an axis 31, the punch having two flat opposite sides 20, 21 parallel to the axis, and a die 3 mounted in axial alignment with the punch. The die 3 comprises a die body 5 also having two flat opposite sides 22, 23 parallel to the axis 31 and a pair of flat parallel spring stool leaf springs 7 each lying along a respective one of the parallel sides of the die body. The leaf springs are secured against the die body 5 at a point 8 below the free end 6 of the die body which faces the punch and extend along the parallel sides 22, 23 of the die body to terminate above the free end 6. The leaf springs 7 initially resist the deforming action of the punch but spring apart as pressure builds up. This delayed action gives the joint right angular edges which retain filler material more readily. The apparatus is a modification of that in UK Patent No. 2087284. <IMAGE>

Description

SHEET METAL JOINING APPARATUS The present invention relates generally to joining sheet metal, in particular to a sheet metal joining apparatus for use in high volume production work. The invention also relates to permanent joints made using the apparatus.

U.K. Patent No. 2087284 describes an apparatus for joining sheet metal which comprises a die mounted in a fixed aligned relationship to, and operatively associated with, a punch. The die has a cavity defined by an anvil forming the bottom surface and by opposed movable forming elements which are pivotally mounted on opposite sides of the central axis of the die. In use, two sheets of metal which are to be joined are placed between the die and the punch, the punch is then pneumatically actuated to engage the metal sheets against the initial restraining action of the pivotally mounted forming elements. As the punch continues moving in the direction of the anvil both pieces of sheet metal are drawn into the die cavity and extruded in a lateral direction. At the same time the pivotally mounted forming elements move laterally apart without restricting the lateral extrusion.The cooperative action of the moving punch, the pivotally mounted forming elements and the fixed anvil act Co deform the two metal sheets to form a secure joint between them.

Whilst the apparatus in U.#. Patent No.

2087284 forms a good interlocking joint between the two metal sheets without employing welding, screws, rivets or the like, and without fracturing any portion of the sheet metal, the recess formed by the deformation of the relevant area of the two metal sheets has the disadvantage of having rounded edges. For many uses of the joined metal sheets the recess produced by this method will require to be filled with a suitable filler material. In practice it has been found that, due to the rounded edges of the formed recess retaining the filler material in the recess can prove to be quite a problem.

It is an object of the present invention to provide an apparatus for joining together at least two metal sheets, or, for example, a metal sheet and a metal channel member, which apparatus employs a punch and an improved die which produces an interlocking joint whose recess has rectangular edges rather than the disadvantageous rounded edges.

It has been found that by providing an apparatus with a die having laterally mounted spring steel leaf springs, an interlocking joint can be formed between at least two metal sheets which has rectangular, and not rounded, edges.

According to the invention there is provided an apparatus for joining sheet metal, comprising a punch arranged for reciprocating movement along an axis, the punch having two flat opposite sides parallel to the said axis, and a die mounted in axial alignment with the punch and operatively associated therewith, the die comprising a die body also having two flat opposite sides which are parallel to those of the punch and a pair of flat parallel spring steel leaf springs each lying along a respective one of the parallel sides of the die body, the leaf springs being secured against the die body below the free end of the die body which faces the punch and extending along the said parallel sides of the die body to terminate above the said free end.

Preferably the end of the punch which engages metal sheets positioned between the punch and the die for joining, is so shaped as to provide a leading flat central area which, in use, is first to engage the metal sheets. Full engagement of the punch with the die produces a joint having a stepped appearance.

The sort of material that can be joined by the present apparatus includes such materials as aluminium, galvanized iron, brass, steel and sheet stock both coated and uncoated. The apparatus is particularly suitable for the joining of different materials which cannot be welded.

The invention will now be further described by way of example with reference to the accompanying drawings in which: Fig. 1 is a longitudinal cross-section view of an apparatus according to the present invention; Fig. 2. is a cross-sectional view of the punch taken along line 2-2 in Fig. 1; Fig. 3 is a cross-section through a joint formed between a metal sheet and a channel member using the apparatus shown in Fig. 1; Fig. 4 is a cross-sectional view through the joint along line 4-4 in Fig. 3; and Fig. 5 is a plan view of the joint of Figs.

3 and 4 Figure 1 is a diagrammatic representation of a sheet metal joining apparatus in accordance with the invention.

The apparatus 1 comprises a punch 2 of rectangular cross-section which is conventionally mounted in a punch assembly 30 for reciprocating movement along a substantially vertical axis 31. The punch 2 is of rectangular cross-section, and has two flat opposite sides 20 and 21 which are parallel to the axis of movement 31.

In operative association with the punch 2 is a die 3 mounted in axial alignment with the punch 2 in a conventional frame 4. The die 3 comprises a die body or anvil 5 whose top surface 6 is flat. The die body is also of rectangular cross-section, and also has two flat opposite sides 22 and 23 which are parallel to the sides 20 and 21 of the punch 2.

The die also includes a pair of flat parallel spring steel leaf springs 7, each of which lies along a respective one of the parallel sides 22 and 23 of the die body 5. The leaf springs 7 are secured against the die body 5 below the top surface 6 of the die body which faces the punch 2, at the point 8 where the die body 5 is mounted in the frame 4. The leaf springs 7 extend along the parable' sides 22 and 23 of the die body 5 to terminate above the top surface 6.

In operation, the apparatus 1 is initially in the position shown in solid lines in Figure 1. Two or more metal sheets (not shown) are placed in face-to-face relationship, with the lower surface of the lowest metal sheet contacting the unattached upper ends 9 of the spring steel leaf springs 7. The punch 2 is actuated by a press, or other suitable apparatus, to move downwardly to contact the sheet metal pieces. The descending punch forms an appropriate area of the metal sheets, first against the leaf springs 7 until they spring sideways (shown in dashed lines) as the punch draws the metal sheets downwardly toward the top surface 6 of the die body 5.

The drawing action results directly from the interaction of the punch 3 and the opening or cavity between the upper ends 9 of the leaf springs 7. As the punch 3 approaches the surface 6 the metal sheets become extruded and form an interlocking engagement with each other against the surface 6 of the die body 5. The lateral extrusion of sheet metal causes the leaf springs 7 to be forced laterally outwardly away from their mountings in frame 4.

The leaf springs 7 initially resist the deforming action of the punch on the metal sheets, until the build up of pressure on the leaf springs due to the continuing downward movement of the punch causes the leaf springs to spring sideways. The delay action in the sideways movement of the leaf springs contributes in a major way to the formation of a joint having right angular edges.

Once the joint between the sheet metal has been formed the punch 2 is withdrawn to the position shown in Figure 1, and the joined metal sheets removed. Upon removal the leaf springs 7 move back to their positions as shown in solid lines in Figure 1.

As seen in Figure 3, in its preferred form the surface of the punch 2 which faces the die 3 (i.e.

the surface which, in use, engages the sheet metal) has in the direction parallel to the two opposite parallel sides 20 and 21 of the punch a leading flat central region 12 which is first to engage the sheet metal.

Next to engage the sheet metal are two sharp forwardly pointed edges 13, which are provided on opposite sides of the central region 12.

Figure 3 shows a joint formed between a metal sheet 10 and a channel member 11 using the apparatus shown in Figure 1. By shading the metal sheet 10 and channel member 11 appropriately it is possible to see how the metal has become drawn or extruded, thereby forming a leakproof joint.

Figure 4 is a cross-sectional side view of Figure 3, and shows the shape of the joint formed using the punch shown in Figure 3.

Figure 5 is a plan view of the joint.

From the illustrations it can be seen that using the apparatus of the present invention a leakproof joint can be found between two metal sheets, or the like, which has right angular edges. Such recessed joints can retain filler material more readily than the prior art joints.

Claims

CLAIMS:

1. Apparatus for joining sheet metal, comprising a punch arranged for reciprocating movement along an axis, the punch having two flat opposite side parallel to the said axis, and a die mounted in axial alignment with the punch and operatively associated therewith, the die comprising a die body also having two flat opposite sides which are parallel to those of the punch and a pair of flat parallel spring steel leaf springs lying along a respective one of the parallel sides of the die body, the leaf springs being secured against the die body below the free end of the die body which faces the punch and extending along the said parallel sides of the die body to terminate above the said free end.

2. Apparatus as claimed in claim 2, wherein, in the direction parallel to the two opposite parallel sides of the punch, the surface of the punch facing the die has a leading flat central region with two forwardly pointed edges on opposite sides of the central region.

3. Apparatus as claimed in claim 1 or 2, wherein both the punch and the die body are of rectangular cross-section.

4. Apparatus for joining sheet metal substantially as described herein with reference to the accompanying drawings.