Apparatus for applying flexible straps around bundles of...

Presses – Binding – Binder applying

Reexamination Certificate

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C100S029000, C100S032000, C100S0330PB, C053S589000

Reexamination Certificate

active

06640700

ABSTRACT:

TECHNICAL FIELD
This invention relates to apparatus and methods for applying flexible straps around bundles of objects.
BACKGROUND OF THE INVENTION
Many high-speed, automatic strapping machines have been developed, such as those disclosed in U.S. Pat. Nos. 3,735,555; 3,884,139; 4,120,239; 4,312,266; 4,196,663; 4,201,127; 3,447,448; 4,387,631; 4,473,005; 4,724,659, 5,379,576, 5,414,980, 5,613,432, and 5,809,873. As disclosed by the devices in these patents, a conveyor belt typically conveys a bundle at high speed to a strapping station where straps are automatically applied before the conveyor belt moves the strapped bundle away from the device.
Typical strapping machines employ an initial or primary tensioning apparatus that provides an initial tensioning of the strap about the bundle. A secondary tensioning apparatus thereafter provides increased or enhanced tension of the strap. A sealing head then seals the strap, typically through the use of a heated knife mechanism, to complete the bundling operation.
FIG. 1
is a strapping machine
100
in accordance with the prior art, as shown and described in U.S. Pat. No. 5,414,980, issued to Shibazaki et al. The strapping machine
100
includes the following major components, all mounted to a housing or frame
110
: a strap dispenser
112
, an accumulator
114
, a feed and tension unit
116
, a track
118
, a sealing head
122
, and a control system
124
. In addition, some devices also have a secondary tension unit
120
(not shown), such as the type disclosed in U.S. Pat. No. 3,552,305 issued to Dorney et al. The basic operation of the machine involves a feeding cycle and a strapping cycle. In the feeding cycle, strap is pulled from a strap coil mounted on the dispenser
112
by a feed and tension motor and is fed through the accumulator
114
, the feed and tension unit
116
, the sealing head
122
, and the track
118
. After the strap has been fed around the track
118
and back into the sealing head
122
, the strapping cycle begins.
During the strapping cycle, the strapping machine performs several functions. First, the sealing head
122
of the strapping machine grips the free end of the strap, holding it securely. Next, in a primary tensioning sequence, a track guide mechanically opens and the strap is pulled from the track
118
as the strap is drawn around the bundle by a feed and tension motor.
As the primary tensioning sequence is completed, additional strap tension may be applied by the secondary tension unit
120
. As this secondary tensioning process is completed, the sealing head
122
grips the supply side of the strap. The overlapping strap sections are then heated by a heater blade, pressed together by a press platen, and severed from the supply by a strap cutter
140
.
Following the sealing process, the strap path through the sealing head
122
is once again aligned and the feeding sequence can begin. The sealing head
122
continues to rotate allowing the seal to cool while the feeding sequence continues. At the end of the strapping cycle, the sealed strap is released and the strapping machine
100
is ready to repeat the feeding cycle.
Although desirable results are achievable using the prior art strapping machines
100
, some operational drawbacks exist. For example, the prior art feed and tension unit
116
typically includes a complicated series of strap guides. The strap must be fed through the strap guides, undergoing several bends and turns between the dispenser
112
and the sealing head
122
. Existing strapping machines typically turn the strap through a total of 360 degrees or more before reaching the track. The bends and turns in the strap path may induce kinks in the strap that may subsequently lead to feeding difficulties. If the strap becomes jammed in the feed and tension unit
116
, the process of clearing the strap path from the complicated series of strap guides may be time-consuming and may require machine downtime.
Another disadvantage of the prior art strapping machines is that the drive assemblies of the sealing head
122
and the feed and tension unit
120
are typically complicated designs featuring a one or more gear boxes. Often these gear boxes are complicated and must transfer the drive forces through a 90 degree angle. Generally, the cost of fabricating the drive assembly increases with the design complexity, adding to the ultimate cost of the strapping machine.
SUMMARY OF THE INVENTION
The present invention improves upon prior strapping devices, and provides additional benefits, such as by providing variability in the apparatus that can be easily altered to fit various production and package requirements and by employing a control system that monitors operating signals and transmits control signals accordingly.
A feed and tension unit under one aspect of the invention includes three sets of wheels: (1) a feeding set including a feed drive roller and a feed pinch roller, (2) a primary tensioning set including a primary tension drive roller and a primary tension pinch roller, and (3) a secondary tensioning set including a secondary tension drive roller and a secondary tension pinch roller, and wherein at least one of the feed pinch roller, the primary tension pinch roller, or the secondary tension pinch roller is coupled to a solenoid that controllably biases the pinch roller against the respective drive roller based on a pinch signal supplied to the solenoid, the pinch signal having a first pulse width modulated stage that provides a full pinch force and a second pulse width modulated stage that provides a reduced pinch force.
During a primary tensioning operation, a control system monitors position signals from a feed pinch roller position sensor and terminates primary tensioning when a slippage condition is determined. The control system then initiates a secondary tensioning operation. The secondary tensioning operation lasts for a predetermined amount of time, then the control system initiates a joining operation that secures the strap around the bundle.
In another aspect of the invention, the three sets of wheels or rollers of the feed and tension unit are configured to provide a simplified strap path that reduces bending of the strap, thereby reducing friction and consequent feeding difficulties. Alternately, the drive wheels of the feed and tension unit may be positioned on the side of the strap opposite from the bundle to reduce adverse effects of debris from the bundle. In another aspect, the feed and tension unit includes inner and outer guides that form a strap channel through the feed and tension unit. The inner and outer guides are configured to provide easy access to the strap path for clearing the strap path in the event of a jam.
In a further aspect of the invention, a strap material accumulating compartment includes a first sidewall having a plurality of mounting posts projecting therefrom, each mounting post having a plurality of mounting holes disposed therethrough, a second sidewall having a plurality of mounting apertures alignable with and slideably engageable with the mounting posts, and a plurality of pin holders positioned proximate the mounting apertures, and a plurality of mounting pins removably and adjustably engageable with the mounting holes and the pin holders. The first and second sidewalls approximately form a chamber therebetween wherein the strap may accumulate. The width of the chamber may be adjusted easily and quickly to accommodate varying widths of strap by removal of the retaining pins, repositioning the second sidewall at the desired location, and replacement of the retaining pins within the desired holes.
In yet another aspect of the invention, the track assembly includes a plurality of sections providing modularity of construction. Each section includes a backplate attached to at least one support member, and a slotted cover pivotably attached to the at least one support member proximate the backplate and moveable between an open position spaced apart from the backplate and a closed position proximate the backplate, and a biasing member e

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