FIELD OF THE INVENTION

This invention relates to strap forming apparatus which has particular, but certainly not exclusive application to the formation of M-straps for use in the handling and transportation of metal ingots or any other packaged or unitized material mass by the unit strap lifting method (USLM) .

BACKGROUND ART

It is now common practice for metal ingots to be handled and transported in units or bundles bound by M-straps. These straps project above the unit in the form of an "M" for dual attachment to overhead cranes. The M-straps are manufactured from a metal strip having a prescribed load carrying capacity

which is formed into a closed overlapping loop and then crimped closed to form a joint. The minimum required strength of the crimped joint is governed by international standard.

It is an object of the invention to provide apparatus which may be adapted to form M-straps in a speedy and efficient manner.

SUMMARY OF THE INVENTION

The invention accordingly provides strap forming apparatus which includes track means for guiding a travelling metal strip to form a closed overlapping loop. At least one or more longitudinal segments of the track means define a groove through which the metal strip travels. A plurality of members are spaced along the track means to momentarily support and contact the metal strip in the track means. A plurality of lifting elements are spaced along the track means and are actuable when the overlapping strip has been fastened to form a strap, to lift the strap vertically from the track means.

The apparatus advantageously further includes means to shape the strap after it has been lifted from the track means. In one embodiment, the strap is shaped to form an M-strap. To this end, the track means is arranged so that the closed loop is of oval shape and the apparatus includes separate forming means for shaping one end of the strap as an "M" and for providing the other end with generally squared corners.

The apparatus preferably includes means for rotatably retaining a reel of the metal strip and means for feeding strip from this reel into the track means.

The track means is preferably formed from elongate lengths of metal plate and is preferably supported on a table.

The members spaced along the track means to momentarily contact and support the travelling metal strip may comprise respective rollers effective to maintain the strip adjacent to and above the table surface. The lifting elements are preferably lifting pins actuable to project from below the table surface. The track may be discontinuous in the region of these lifting elements.

Means is preferably provided to control the height to which the strap lifts vertically from the track means.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which:

FIGURE 1 is a plan view of strap forming apparatus according to the invention;

FIGURES 2 and 3 are fragmentary perspective views of the respective ends of the track forming part of the apparatus of Figure 1;

FIGURE 4 is a cross-section view on the line 4-4 in Figure 1;

FIGURE 5 is a fragmentary perspective view of the lifting pins; and

FIGURE 6 is a view similar to Figure 1 but showing the shaping of a strap which has been formed in the apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

The illustrated strap forming apparatus 10 is supported atop a table 12 which defines a working surface 13. The apparatus includes an oval shaped track 14 for guiding a travelling metal strip to form a closed overlapping loop, and plural roller members 16 at spaced locations along the track to momentarily contact and support the metal strip in the track 14 above surface 13. Plural lifting elements in the form of pins are spaced along the track and are actuable, when the overlapping strip has been fastened to form a strap, to lift the strap vertically from the track 14. Respective installators 20, 22 are provided at the ends of the oval track 14 for shaping the released strap in a manner to be described. The apparatus also includes a station 24 for rotatably mounting a reel of metal strip and a device 26 for gripping and feeding the strip from the reel along a branch track 28 into the oval track 14.

Track 14 is formed from elongate steel plate securely welded atop working surface 13. Two curved end portions 30a, 30b and side portions 30c, 30d, 30e are aligned to define an outer face of the track which is continuous except for short breaks for a purpose to be described. Longitudinal segments of the track adjacent the ends of the curved portions 30b and at the straight portions 30c, 30d, 30e are provided with inner segments of elongate metal plate so that the track in these longitudinal segments defines a groove 40 through which the metal strip travels. Branch track 28 is similarly defined by a pair of parallel elongate metal plates defining a

groove 40a.

It will be seen from Figure 1 that metal strip fed along branch track 28 will travel in a specific direction around track 14 and come back in behind itself between track segments 30d and 30e. The entrances to each grooved track segment 40 relative to this direction of travel have the defining metal plates flared outwardly to facilitate entry of the strip into each grooved segment. The front end of the strip strikes a microswitch 42 which stops the feed device 26 and actuates a guillotine 44 to cut the strip at the head of branch track 28.

Travel of the metal strip along the track 14 is facilitated by roller members 16. There are six of these rollers adjacent each end and approximately at the centre of each side of the track 14. The rollers 16 are freely rotatable in bearings fixed under the table 12 and act to support the strip adjacent and above the surface 13. Instead of rollers 16, wear pads of a suitable material may project slightly above table surface 13.

When the strip has been formed into its overlapping closed loop and guillotined, the overlapped segments, between the guillotine 44 and the microswitch 42, are crimp fastened by a device 50 in order to meet international standards for USLM handling. Device 50 is mounted to the table 12 by means of a multi-hinged arm 52 so that it may be moved manually from a retracted position to a working position where, on triggering by the operator, device 50 crimps closed the overlapping portions of the strip. Lifting pins 18 may now be simultaneously projected vertically by triggering pneumatic actuators 19 associated with each pin under the

table. Pins 18 are disposed in short gaps 17 in the track 14 at each end of each curved segment 30a of the track 14. The gaps 17 are necessary because the pins 18 are wider than the grooves 40 but reliable travel of the metal strip across the gaps 17 is ensured by the flared ends 46 of the grooved segments. Excessive vertical movement of the strap is prevented by four overlying stops 48 having depending legs by which they are fixed to the table surface 13.

Once the strap has been formed and released from the track, forming installators 20, 22 are operated to shape the strap as a lifting M-strap. Each forming installation has a pair of upstanding posts 60, 61 on the inside of the curved track 14 and a pair of adjacent runners 62, 63 along which the strap is pushed by formers 64, 65. Formers 64, 65 positioned at either end of the track 14 are powered by hydraulic actuators 66, 67.

Former 64 comprises a pair of forming heads 68 which travel along runners 62 to a position adjacent the posts 60 sufficient to form squared corners on the strap. Former 65 is a roller which travels mid-way between posts 61 and runners 63 to a position well past the posts and adjacent the inner ends of the runners 63. Former 65 thereby provides this end of the strap with an M-shape. Figure 6 depicts the two formers at their innermost positions and the location of the strap about the posts and formers at this point.

Reel mounting device 24 is a circular casing having multiple freely rotating rollers along its outer periphery and a central rotatable hub 72. A retaining bar 74 is hinged to the casing at one side

and may be locked in place at the other. The retaining bar 74 is hingedly retracted for positioning a reel in the casing on the hub 72 and then returned and locked in place to hold the reel in the casing. The end of the strip is fed along trap 28 to device 26. When the latter is actuated, it pulls the strip from the reel, which freely rotates on the hub 72 and against the rollers. Device 26 is of a conventional nature including a pair of gripping rollers configured to oppositely curve the strip and so remove the bend arising from its storage on the reel.

It will be appreciated that the illustrated apparatus is a particularly effective facility for the formation of M-straps. A large supply of the required metal strip may be held as a reel in device 24 and the free end of the strip permanently held by feed device 26. To form an M-strap, device 26 may be triggered to rapidly feed the strip around track 14 into a closed overlapping loop until it strikes microswitch 42. Device 26 is disabled and the guillotine 44 cuts the strip. An operator then uses crimper 50 to fasten the overlapping portions of the strip and thereafter triggers actuators 19 to lift the resultant strap from the track. He then operates formers 64, 65 to shape the strap which can be removed and suspended for subsequent use. While formers 64, 65 shape the first strap, device 26 is triggered to feed strip around track 14 to form a second strap. Feeding of the strip can be reliably carried out at high speed in as little as 1.5 seconds and the whole strap formation can be completed within 20 to 25 seconds.