US 4,050,372 A · Automatic strapping machine

Abstract

An automatic strapping machine is disclosed wherein strap is fed at a high rate of speed about a package so as to form a loop which is then tensioned and sealed. The loop is formed so that the leading end of the strap is overlapped by a trailing end of the strap and the resulting overlapped strap portions are joined together so as to form a seal which is not susceptible to snagging. The distal end of the overlapping strap end portion is urged against and is moved back and forth relative to an underlying strap portion in tension at a high rate of speed so as to generate heat therebetween and to form a friction-fused joint. During joint formation the strap loop about the package is in tension, but the strap end portion overlapping the loop is relaxed, i.e., not in tension. Sealing energy generating means is adapted to engage the distal end of the overlapping strap end portion and comprises a pivotable anvil and a rotatable - oscillatable hammer adapted to receive overlapping strap regions therebetween, and an oscillating motor means for the hammer which engages the loop-over-lapping strap end portion and rubs the overlapping end portion against the underlying strap region at a rate sufficient to melt an interface region therebetween and to form a friction-fused joint when energized by the oscillating motor means.

Claims12

Dependent claims

A strapping apparatus for providing a tensioned loop of thermoplastic strap about a package which comprises

means for automatically feeding and tensioning a thermoplastic strap segment in a loop about the package;
positioning means for locating leading and trailing portions of the looped strap segment in an overlapping relationship relative to one another;
grip means holding the overlapped portions in said positioning means so as to expose an untensioned trailing strap end portion;
force-generating means for frictionally engaging distal end of the exposed trailing strap end portion and urging an inner face region of said exposed trailing strap end portion against an inner face region of a loop strap section in tension, said force-generating means including a pivotable hammer having a strap engaging surface and a channel defining a gate through which strap forming said loop passes;
a cutter means positioned adjacent to said gate and coacting with said gate to sever the strap when said hammer is pivoted after said loop is formed but before the exposed end portion is oscillated;
and
energizing means associated with the force-generating means for longitudinally oscillating said distal end of the exposed end portion relative to said loop strap section to fuse said distal end of the exposed end portion with said strap section at an interface region thereof and to securely weld the exposed end portion to the strap section at said interface region.

4 more elements

Apparatus for sealing a loop formed of a tensioned thermoplastic strap segment about an article which comprises

positioning means for locating portions of said strap segment in an overlapping relationship relative to each other;
grip means associated with said positioning means for engaging and holding the overlapped portions in said positioning means so as to expose a free end portion;
force-generating means for frictionally engaging the free exposed end portion and urging the free exposed end portion against an overlying loop strap section in tension and comprising a pivotable and retractable anvil associated with a rotatable hammer, said hammer being provided with a convex strap-engaging surface and said anvil being provided with a complementary concave strap engaging surface;
and
energy-storing, oscillating motor means associated with the force-generating means for longitudinally oscillating the free exposed end portion relative to said overlying loop strap section to fuse the free exposed end portion to the strap section at the interface region thereof comprising a torsion bar having one end mounted in a pivotable support means and a free end keyed to said hammer at the axis of rotation of said hammer, means for locking the mounted end portion of said torsion bar against rotation, and means for twisting the torsion bar a predetermined amount and subsequently releasing the twisted torsion bar while the mounted end portion thereof is locked against rotation.

2 more elements

Dependencies are inferred from the claim text.

Automatic strapping machine

Life of this patent

Automatic strapping machine

Life of this patent

Abstract

Claims12