Jam-clearing and torque sensing traction wheel assembly and strap feed stopping mechanism

A combination jam-clearing and torque sensing traction wheel assembly and strap feed stopping mechanism is disclosed for use in a strapping machine which feeds strap in a chute about an article to form a loop and subsequently tensions the loop tightly about the article. The strap is fed into the chute by a rotating traction wheel which is driven through a torque sensing assembly comprising a driven plate, a spring-biased driver plate, and drive motor. Feeding of the strap is intermittently stopped and started as the driver plate is forced out of engagement with the driven plate when the torque increases beyond a predetermined amount in response to increased strap feed resistance resulting from an obstruction in the chute. In one embodiment, the strap feed stopping mechanism includes a permanent strap end abutment member located just past the strap overlap region in the strapping machine. When the strap free end hits the abutment member, the driver plate is forced out of engagement with the driven plate and feeding of the strap is terminated. In another embodiment, the strap feed stopping mechanism includes a ratchet wheel and a pawl actuated by a sensor in the strap chute and which is responsive to the strap free end location in the chute when a loop is being formed. Tripping of the sensor by the strap free end actuates a mechanism to move a pawl into engagement with the ratchet wheel to prevent further strap feed rotation of the traction wheel secured thereto. Additionally, the restraint against the traction wheel rotation causes the driver plate to disengage from the traction wheel.

BACKGROUND OF THE INVENTION 
In the recent past, Signode Corporation, the assignee of the entire 
interest of the present application, has developed several machines for 
feeding strap in a chute to form a loop around an article to be strapped 
and for tensioning the loop tight about an article. Typically, these 
machines also apply a seal to the tensioned loop and sever the tensioned 
and sealed loop from the standing, or trailing, length of strap. Typical 
of such machines is the one disclosed and claimed in the U.S. Pat. to G. 
A. Crosby et al., No. 2,915,003. 
STRAP CHUTE OBSTRUCTION PROBLEMS 
Some strapping machines, such as the machine disclosed in the Crosby et al. 
patent, U.S. Pat. No. 2,915,003, are susceptible to strap jamming as the 
strap is fed in the strap chute and encounters extraneous obstructions 
that may have lodged in the chute. With machines currently in use, the 
strap continues to be fed when such an obstruction is encountered. This 
causes the strap to buckle away from, and out of engagement with, the 
strap track in the chute. 
Some machines control the strap feeding in the chute by a cycle timer 
system and some machines just feed a predetermined length of strap. With 
either type of machine, the strap will continue to be fed, even though an 
obstruction is encountered, until the cycle is terminated. Obviously, in 
such a situation, the strap may buckle out of the chute and not form into 
a loop. Hence, the subsequent tensioning, sealing and severing actions of 
the machine, which are automatically initiated, would not produce a 
tightened loop about the package. 
Other types of strapping machines terminate the strap feed by sensing the 
location of the strap free end after the loop has been formed. If an 
obstruction is encountered by the strap in the strap chute of such a 
machine, the strap may buckle out of the chute and will not form a loop. 
The strap will continue to be fed by the machine until terminated by an 
overall shut-off cycle timing system or other means. 
It is desirable that a method and apparatus be developed which (1) will 
allow the feeding of a strap into the chute and (2) will, when an 
obstruction is encountered by the strap free end, automatically terminate 
the feeding of the strap. It would also be desirable to provide a means 
whereby the strap feeding, after being terminated when the strap free end 
hits an obstruction, can be automatically continued in an attempt to clear 
the obstruction. In fact, it would be desirable to provide a mechanism 
whereby the feeding of the strap can be readily started and stopped to 
produce a "fluttering" effect of the strap free end. This would tend to 
cause the strap free end to pass by an obstruction in the chute or knock 
such an obstruction from the chute. 
STRAP FEED TERMINATION PROBLEMS 
In strapping machines in use today, a means is provided to terminate the 
strap feeding process once a complete loop has been formed with the strap 
and after a small portion of the strap free end has overlapped a portion 
of the loop. A number of methods are currently employed to terminate the 
strap feeding process and have already been briefly described above. The 
use of these methods has certain drawbacks which will be discussed here. 
In one method, a predetermined length of strap is fed by accurately 
controlling the feeding cycle of the machine. This involves accurately 
indexing the strap feed, or traction, wheel a certain number of rotations. 
Such a method requires complicated and expensive motors and control 
systems. Further, a strap cannot be fed very rapidly with such a system. 
A second method requires feeding of the strap at a constant feed rate for a 
predetermined length of time. Such a method involves a timer control 
circuit and is inherently less reliable than the other methods that 
directly control the length of strap that is fed. 
Another method for terminating the strap feeding process upon formation of 
the loop is to provide a motor cut-off limit switch actuated by a sensing 
lever in the strap chute, the lever being impinged by the strap free end 
after formation of a complete loop. Machines that employ a strap feed 
termination system with a limit switch and sensing lever typically have 
the lever located "ahead" of the strap sealing unit. Such machines rely 
upon motor momentum to feed the strap free end beyond the sensing lever 
and adjacent the sealer unit where the strap free end hits an abutment and 
stops completely. However, the impingement of the strap free end against 
the abutment tends to cause the strap to buckle in the chute. To 
accommodate this buckling, a "drop-out gate" is employed. The drop-out 
gate is an integral part of the strap chute which is hinged on one end and 
is spring biased on the other end into alignment with the strap chute 
track. When the strap free end impinges upon the terminal abutment beyond 
the sealing unit and begins to buckle, the strap pushes the drop-out gate 
away from the strap track. Any strap portion that would tend to form a 
buckling "hump" in the strap chute is accommodated in the open drop-out 
gate. This prevents any buckling from occurring within the chute strap 
track. Typical of such drop-out gate devices is the device disclosed in 
U.S. Pat. No. 2,915,003 to Crosby et al. 
It has been found that the drop-out gate has a number of disadvantages. 
First of all, it is difficult to place the drop-out gate on a small chute 
where it will not interfere with the actual operation of the machine or 
placement of the package to be strapped. In addition, the drop-out gate 
requires a more complicated strap chute and therefore makes a strapping 
machine more expensive. It has also been found that the drop-out gate bias 
spring is quite sensitive and must be carefully adjusted. Too much biasing 
force results in the strap buckling elsewhere in the chute and too little 
biasing force results in premature opening of the drop-out gate. 
It would be desirable to provide a strapping machine wherein the drop-out 
gate can be eliminated and wherein rotation of the strap feed wheel is 
immediately terminated when the strap loop has been formed. This would 
prevent motor momentum from continuing to feed the strap and causing 
buckling. In addition, the precise amount of overlap in the loop could be 
regulated accurately if the rotation of the traction wheel were 
immediately terminated when the predetermined amount of desired overlap 
was achieved. Further, it would be desirable to also disengage the motor 
drive from the traction wheel when the loop has been formed. This would 
permit the motor to continue running at speed and be available for the 
subsequent machine operations. 
SUMMARY OF THE INVENTION 
The apparatus of the present invention utilizes a unique system for 
terminating the strap feeding process upon formation of a loop in the 
strap chute or upon the strap free end encountering an obstruction in the 
strap chute. 
The novel torque sensing assembly, which stops strap feeding when a chute 
obstruction is encountered, will first be described. A means is provided 
to disengage the motor from the traction wheel when an obstruction is 
encountered by the strap free end as it is guided around the strap chute 
during the feeding process. The traction wheel is mounted on a drive shaft 
which is in turn driven by a motor. The traction wheel is mounted so that 
it may rotate relative to the shaft. A driven member or wheel is secured 
to the traction wheel for rotating with it relative to the shaft. The 
driven wheel has a protrusion presenting a first shoulder surface parallel 
to the axis of rotation of the shaft and a second shoulder surface at an 
angle with respect to the axis of rotation of the shaft. Adjacent the 
driven wheel is a driver plate which is mounted on the shaft for sliding 
therealong and which is keyed thereto against relative rotation. The 
driver plate has a recessed wall structure or channel for engaging the 
protrusion on the driven wheel member in mating relationship with the 
first and second shoulder surfaces. The driver plate is urged along the 
shaft into engagement with the driven wheel by a helical spring disposed 
about the shaft. One end of the spring is restrained on the shaft and the 
other end of the spring abuts the driver plate and urges it from a 
position disengaged with the driven wheel to a position in engagement with 
the driven wheel. 
Since the driver plate is keyed to the shaft, the driver plate rotates with 
the shaft at all times when the drive motor is operating to rotate the 
shaft. The helical spring biases the driver plate against the driven wheel 
whereby the driven wheel can be rotated in either direction. In one 
direction of shaft rotation, the strap is fed, and in the other direction 
the strap is tensioned. 
The first shoulder surface of the driven wheel engages a portion of the 
recessed wall structure of the driver plate so that the driver plate can 
rotate the driven wheel and traction wheel in a direction to tension the 
strap. When the shaft is rotated in the other direction--the direction 
tending to rotate the traction wheel to feed the strap--the second, or 
slanting, shoulder surface of the driven wheel is engaged by a portion of 
the recessed wall structure. But for the bias spring, the slanted surface 
of the driven wheel shoulder would cause the recessed wall of the driver 
plate to slide along the slanted shoulder surface and out of engagement 
with the surface. However, the helical spring urges the driver plate 
against the driven wheel and maintains the driving relationship 
therebetween. The biasing force of the helical spring is overcome only 
when a certain amount of torque is reached. At that point, the driver 
plate becomes disengaged from the driven wheel. 
Normally, when the strap is fed into the strap chute, the strap encounters 
very little resistance in the strap track. Consequently, the traction 
wheel requires relatively very little torque to feed the strap. However, 
should the strap free end encounter an obstruction in the strap chute, the 
resistance to the forward feeding strap movement is transmitted through 
the traction wheel to the driven wheel. Additional torque is then required 
to move the strap forward. With the helical spring set to exert a 
predetermined force, the driver plate can be forced outwardly, by the 
slanted surface of the driven wheel shoulder, against the spring and will 
eventually be forced completely out of engagement with the driven wheel. 
Thus, when an obstruction is encountered, the driver plate disengages from 
the driven wheel and the feeding of the strap is terminated. However, the 
shaft is still being rotated by the motor so that as the driver plate 
rotates, the recessed wall structure in the plate is likewise rotated to 
again engage a protrusion. This allows the motor to drive the traction 
wheel to feed the strap forward again. If the obstruction is still 
present, the increased resistance is still transmitted to the traction 
wheel and driven wheel, thereby causing the driver plate to again become 
disengaged. This process is repeated as long as the obstruction is 
present. The rapid, intermittent starting and stopping of the strap feed 
process causes the strap free end to vibrate or "flutter" in the strap 
chute. This fluttering effect is valuable in causing the strap free end to 
overcome or pass by an obstruction in the chute. The fluttering may tend 
to dislodge the obstruction or may tend to cause the strap to pass under, 
around, or through the obstruction and thereby permit the strap to 
complete the loop. 
The mechanism for terminating the strap feed upon formation of the loop 
will now be described. The strap is fed, by a traction wheel, into a strap 
chute wherein it is guided to form a loop about an article placed therein. 
When the strap free end has been guided within the strap chute to form a 
complete loop, it impinges upon a sensing lever at the appropriate 
location in the strap chute. In one embodiment, the lever is connected to 
a limit switch in a control circuit for actuating an electric solenoid to 
move a pawl into engagement with a ratchet wheel secured to the traction 
wheel. In a modification of this, the lever is directly connected to the 
pawl by an appropriate mechanical linkage. In either case, this action 
stops the rotation of the traction wheel in the strap feed direction. 
In the preferred embodiment, the motor drive is disengaged from the 
traction wheel when the complete loop has been formed and when the 
traction wheel has been stopped from rotating by the pawl and ratchet 
wheel mechanism previously described. Specifically, when the loop has been 
formed and the limit switch has been actuated to engage the pawl to stop 
the ratchet rotation, the ratchet wheel causes the driving wheel to 
disengage in the same manner as it would disengage under an increased 
torque resistance resulting from an obstruction in the strap chute. 
Consequently, when the strap loop has been formed, the motor is 
immediately disengaged from the traction wheel to thereby prevent the 
motor from being "locked" with the stopped traction wheel. The motor can 
thus be kept running and could, through appropriate controls and 
transmissions, be then immediately drivably engaged with the same traction 
wheel, or with a different traction wheel, to rotate the traction wheel in 
the opposite, loop tensioning direction or could be drivably engaged to 
operate another machine function. 
In another embodiment of the present invention, a strap feed stopping 
mechanism is employed which incorporates a strap end abutment member just 
beyond the joint forming area. When the strap free end is fed completely 
around the chute to form a loop, the strap free end impinges against the 
strap end abutment member and, as in the case of an obstruction in the 
strap chute, causes the driver plate of the torque sensing clutch to 
become disengaged, thereby terminating the strap feeding. Suitable 
controls may be used to stop the motor if desired. With strap having an 
appropriate section modulus and with suitable strap feeding speeds and 
strap loop sizes, the use of such permanent strap abutment member 
eliminates the need for the more complicated pawl and ratchet wheel 
mechanism as well as eliminates the need for a drop-out gate assembly. 
Numerous other advantages and features of the present invention will become 
readily apparent from the following detailed description of the invention 
and of embodiments thereof, from the claims and from the accompanying 
drawings in which each and every detail shown is fully and completely 
disclosed as a part of this specification.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
While this invention is susceptible of embodiment in many different forms, 
there are shown in the drawings and will herein be described in detail 
preferred embodiments of the invention. It should be understood, however, 
that the present disclosure is to be considered as an exemplification of 
the principles of the invention and is not intended to limit the invention 
to the embodiments illustrated. 
For ease of description, the apparatus of this invention will be described 
in normal operating position, and terms such as upper, lower, horizontal, 
etc., will be used with reference to this normal operating position. It 
will be understood, however, that apparatus of this invention may be 
manufactured, stored, transported and sold in orientation other than the 
normal operating position described. 
The apparatus of this invention has certain conventional drive mechanisms 
and control mechanisms which, though not fully illustrated or described, 
will be apparent to those having skill in the art and an understanding of 
the necessary functions of such drive mechanisms causing proper operation 
of the apparatus in the manner as will be explained. 
A typical power strapping machine is illustrated diagrammatically in FIG. 1 
where the main controls, drive motors, transmissions, gripping, sealing, 
and severing mechanisms are located in housing 12. A chute 16 is located 
adjacent the front of the housing 12 and receives strap 20 which is fed on 
the inner periphery of the chute 16 around a package or article 22 which 
is disposed within the chute and maintained therein by appropriate support 
members (not shown). Typical of such machines are those disclosed and 
claimed in the following U.S. patents: 
Crosby et al. U.S. Pat. No. 2,915,003 
Crosby et al. U.S. Pat. No. 3,023,693 
H. t. martin U.S. Pat. No. 3,088,397 
The combination strap feed stop mechanism and jam-clearing and torque 
sensing traction wheel assembly of the present invention is 
diagrammatically illustrated in dashed box A in FIG. 1. A conventional 
strap guide 24 is located in housing 12 and receives strap 20 from a 
conventional strap supply reel (not shown). The strap 20 runs through 
guide 24 in the housing and into chute 16. 
The strap is fed (and subsequently tensioned) through housing 12 by a 
conventional traction wheel drive. The traction wheel drive typically 
consists of upper idler wheel 26 and a lower traction wheel 28 (not 
visible in FIG. 1, but illustrated in FIG. 2). The idler wheel 26 is 
typically biased against traction wheel 28 so that the strap 20 is gripped 
therebetween by the peripheral surfaces of the two wheels. The strap 20 is 
fed through strap guide 24 from right to left, as viewed in FIG. 1, and 
counterclockwise about chute 16 to form a loop with the strap free end 30 
overlapping a portion of the loop inside the chute 16. After the loop has 
been formed, feeding of the strap 20 is terminated and the strap free end 
30 is gripped or restrained from movement (by mechanisms not shown). The 
strap 20 is then drawn by the traction wheel drive in the direction to 
tension and tighten the loop about the article 22. When the loop has been 
drawn tight about the article 22, the overlapping portions of the strap 
are secured together by appropriate means, such as by friction fusion, 
application of an independent seal, or by formation of an interlocking 
slit type joint. Mechanisms for performing these operations, as well as 
the mechanism for severing the loop from the trailing portion of strap 20 
are all typically located within housing 12 and are not individually 
illustrated in FIG. 1. 
JAM-CLEARING AND TORQUE SENSING TRACTION WHEEL ASSEMBLY 
In some types of strapping machines it would be desirable to provide a 
simple mechanism for rapidly starting and stopping the traction wheel 
rotation during the feeding of a strap in a chute when an obstruction or 
area of excessive friction is encountered. Termination of the traction 
wheel rotation will initially prevent the strap from buckling when it hits 
the obstruction. Subsequent rotation of the traction wheel will tend to 
move the strap forward again into the obstruction, which may now be 
dislodged. If the obstruction is not dislodged, the feeding process would 
again be terminated and then subsequently restarted. If this procedure is 
carried out rapidly enough, the end of the strap would "flutter" and may 
then possibly pass under, around, or through the obstruction or area of 
excessive friction and then complete the path in the chute to form the 
loop. 
A novel jam-clearing and torque sensing traction wheel assembly for 
achieving the above described objective is illustrated in FIGS. 2, 3 and 
4. The assembly can also be combined in a novel manner with the strap feed 
stop mechanism (to be fully described hereinafter in a separate section). 
The unique combination provides an apparatus which not only incorporates 
the novel jam-clearing feature but also immediately terminates the 
rotation of the traction wheel upon formation of the strap loop and 
simultaneously disengages the drive motor from the stopped traction wheel 
while the motor is rotating. 
To aid in understanding the details of the jam-clearing and torque sensing 
traction wheel assembly and its combination with the strap feed stop 
mechanism, a simple overall operational description will first be 
presented. 
As is diagrammatically illustrated in FIG. 1, a sensor means 34 is provided 
to sense the location of the strap free end 30 in the chute 16 when the 
strap loop has been formed. The rotation of the traction wheel 28 is 
terminated by a latch means responsive to the sensor means 34. The latch 
means comprises an actuator means 36 and pawl 38 arranged to engage a 
ratchet wheel 40 which is secured to the traction wheel 28. 
A novel arrangement of the traction wheel 28 and ratchet wheel 40 is 
illustrated in detail in FIG. 2. A shaft 42 is journaled in the frame 
bearing 44 and is driven by a motor 46. Traction wheel 28 is mounted on 
shaft 42 for rotation relative thereto. Traction wheel 28 is located on 
the shaft 42 in alignment with, and below, strap guide 24. In the 
preferred embodiment, ratchet wheel 40 is an integral extension of 
traction wheel 28 and, as such, rotates with the traction wheel 28 
relative to shaft 42. 
The ratchet wheel 40, as well as the associated sensor means 34, actuator 
36 and pawl 38, which comprise the strap feed stop mechanism, are not 
necessary for proper functioning of the jam-clearing feature associated 
with the torque sensing traction wheel assembly. To that extent, the 
components which comprise the strap feed stop mechanism may be initially 
ignored in FIGS. 2 through 4. After the jam-clearing feature has been 
separately and fully described, a description will be presented covering 
strap feed stop mechanism in detail, as well as the novel combination of, 
and interrelationship between, the strap feed stop mechanism and 
jam-clearing and torque sensing traction wheel assembly. 
As illustrated in FIGS. 2 and 4, a torque sensing clutch means is provided 
to disengage the drive motor 46 from the traction wheel 28. To this end, a 
driven means or plate 47 is provided as an integral extension of the 
traction wheel 28. In the embodiment illustrated in FIGS. 2 through 4, the 
traction wheel 28 has a large extension piece which is formed into an 
integral driven plate 47 and ratchet wheel 40. The driven plate 47 
therefore can rotate with the traction wheel 28 and ratchet wheel 40 
relative to the shaft 42. 
A driver means or driver plate 48 is mounted for sliding along shaft 42 but 
is keyed to the shaft 42 by spline 49 against relative rotation. The 
driver plate 48 is urged between a driving position in contact with the 
driven plate 47, as illustrated in FIG. 2, and a disengaged position 
spaced away from the driven plate 47, as illustrated in FIG. 4, by a bias 
means or bias spring 50. The bias spring 50 is a helical type spring 
disposed about shaft 42 and restrained thereto on one end by flange 51 
which projects from shaft 42. The other end of bias spring 50 is 
compressively engaged against the driver plate 48. The bias spring 50 thus 
rotates with shaft 42 and the driver plate 48. 
The driven plate 47 and the driver plate 48 are adapted to be drivably 
engaged by protrusions 53 which project from the face of driven plate 47 
and mating recesses 54 formed in the face of driver plate 48. The driven 
plate 47 has three such protrusions 53 circumferentially spaced 
120.degree. apart and the driver plate 48 has three mating recesses 54. 
Each protrusion 53 has a first shoulder surface 55 parallel to the axis of 
rotation of the shaft 42 and a second shoulder surface 56 at an angle to 
the axis of rotation of the shaft 42. Each recess 54 in the driver plate 
48 is channel-shaped, the interior surface of which conforms to the 
surfaces of the protrusions 53. 
The driver plate 48 can drive the driven plate 47 and traction wheel 28 
counterclockwise, as viewed in FIG. 3, to feed the strap. In FIG. 4, the 
driver plate 48 is shown disengaged from the driven plate 47. As shaft 42 
is rotated in the direction of the arrow, the disengaged driver plate 48 
is also rotated in the direction of the arrow owing to its splined 
engagement on the shaft. After the shaft has rotated 120.degree., the 
recesses 54 again become aligned with the protrusions 53 on the driven 
plate 47. At that point, the driver plate 48 is urged by bias spring 50 
along shaft 42 towards driven plate 47 and into engagement therewith as 
shown in FIG. 2. In the engaged position, with the shaft 42 rotating in 
the direction of the arrow, the strap can be fed by the traction wheel 28 
(from right to left in FIG. 2) to form a loop in the chute. The torque 
from the motor 46 is transmitted through the shaft 42 and into the driver 
plate 48 through spline 49. The slanted wall of each recess 54 engages the 
second shoulder, or slanted, surface 56 of each mating protrusion 53. The 
torque of the motor is thus transmitted through the mating slanted 
surfaces when the strap is being fed. 
If an obstruction is encountered in the strap chute by the strap free end 
as it is fed around the chute, the additional resistance caused by the 
obstruction is transmitted along the strap to the traction wheel 28 and to 
the driven plate 47. To overcome the additional resistance, the driver 
plate 48 must be rotated with more torque by motor drive 46. By 
appropriate choice of the spring constant for bias spring 50, the force 
that the bias spring 50 exerts upon driver plate 48 can be established so 
that the driver plate 48 disengages in response to the increased torque 
required to rotate the driven plate 47 when an obstruction is encountered 
in the chute. In such a situation, the slanted surfaces of the recesses 54 
slide along the slanted second shoulder surfaces 56, compressing bias 
spring 50 to disengage the driver plate 48 from the driven plate 47 
(whereby the driver plate 48 and driven plate 47 assume the orientation as 
illustrated in FIG. 4). 
When the driver plate 48 disengages from the driven plate 47 as described 
above upon an obstruction being encountered by the leading end of the 
strap in the strap chute, the shaft 42 is still being rotated by the 
motor. Thus, the driver plate 48 continues to rotate and the recesses 54 
in the driver plate 48 are rotated back into engagement with the 
protrusions 53. This allows the motor to drive the traction wheel 28 to 
feed the strap forward again. If the obstruction is still present, the 
increasing resistance is still transmitted to the traction wheel 28 and 
the driven plate 47, thereby causing the drive plate 48 to again become 
disengaged. This process is repeated as long as the obstruction is 
present. The rapid, intermittent starting and stopping of the strap feed 
process causes the strap free end to vibrate or "flutter" in the strap 
chute. This fluttering effect is valuable in causing the strap free end to 
overcome or pass by an obstruction in the chute. The fluttering may tend 
to dislodge the obstruction or may tend to cause the strap to pass under, 
around, or through the obstruction and thereby permit the strap to 
complete the loop. 
The torque sensing clutch means also accommodates the rotation of the shaft 
42 in a direction necessary to tension and tighten the strap about the 
article. When the shaft is rotated clockwise (as viewed in FIG. 3) with 
the driven plate 47 and driver plate 48 engaged, the traction wheel 28 
draws the strap 20 from left to right (as viewed in FIG. 2) to tension the 
strap and tighten the loop about the package. In this mode, the first 
shoulder surfaces 55 of the protrusions 53 are engaged by the recesses 54. 
The jam-clearing and torque sensing traction wheel assembly can also be 
used in conjunction with the strap feed stop mechanism to terminate the 
strap feed process after the loop has been formed and to disengage the 
drive motor from the traction wheel while the drive motor is allowed to 
continue running. This feature will be described in the following section 
on the strap feed stop mechanism. 
STRAP FEED STOP MECHANISM 
As was noted in the "Summary of the Invention" above, the apparatus of the 
present invention provides a novel and unique way of terminating the 
feeding of the strap upon formation of the strap loop about an article. 
Two embodiments of a subassembly or mechanism for terminating the feeding 
of a strap upon formation of the strap loop about an article will next be 
described. The first embodiment includes a positive latching device and 
the second embodiment includes a strap end abutment means which, in 
combination with the torque sensing clutch, eliminates the need for a 
positive latching device. 
FIRST EMBODIMENT: POSITIVE LATCH 
It was briefly stated in the preceding section that the preferred 
embodiment of the strap feed stop mechanism, diagrammatically illustrated 
in FIG. 1, comprises a sensor means 34, actuator 36, pawl 38, and ratchet 
wheel 40. The novel arrangement of the traction wheel 28 and ratchet wheel 
40 is illustrated in detail in FIG. 2 and was previously described in 
detail in the preceding section. The rotation of the traction wheel 28 is 
terminated by a latch means responsive to the sensor means 34. The latch 
means comprises the actuator means 36 and pawl 38 and is best illustrated 
in FIG. 3. The ratchet wheel has teeth 60 which can be engaged by pawl 38. 
Pawl 38 is pivotally mounted to a portion of housing 12 by bolt, or pin, 
61. In a preferred embodiment, spring 62 is disposed in commpression on 
one end to pawl 38 and on the other end to support 63 for biasing the pawl 
38 away from ratchet wheel 40 against stop pin 64 (as illustrated by the 
dashed lines in FIG. 3) to disengage teeth 60 and allow rotation of 
ratchet wheel 40 in the counterclockwise direction. 
An electric solenoid actuator 66 is secured to a portion of housing 12 by 
bracket 67 with bolts 68 and is pivotally connected to pawl 38 with pin or 
bolt 69 on the end of arm 70. When the electric solenoid is de-energized, 
the arm 70 and pawl 38 assume the location shown by dashed lines in FIG. 
3. In the energized mode, the electric solenoid 66 retracts arm 70 to the 
left (as viewed in FIG. 3) to rotate pawl 38 about pivot bolt 61 until 
pawl 38 engages teeth 60. By design, the spring 62 is chosen so that its 
spring force is less than the "pulling" force exerted by the energized 
electric solenoid 66 upon pawl 38 so that the spring can be overcome to 
allow pawl 38 to engage teeth 60. 
Note that even when the solenoid 66 is energized, the ratchet wheel 40 can 
still be rotated in the clockwise direction. When rotating in the 
clockwise direction, the ratchet wheel teeth 60 overcome the energized 
holding force of the solenoid 66 and push the pawl 38 outwardly from the 
ratchet wheel 40 as they rotate past the pawl. 
The electric solenoid 66 is de-energized during the strap feeding process 
to maintain pawl 38 out of engagement with the ratchet wheel 40. To 
terminate the feeding process, the power circuit of electric solenoid 66 
is closed thereby energizing the solenoid to engage the pawl 38 with the 
ratchet wheel 40. Closure of the power circuit is effected in response to 
the sensor means 34 when the strap loop has been formed in the chute 16 as 
will hereinafter be described. 
The sensor means 34 is best illustrated in FIGS. 5 and 6. The front face 72 
of housing 12 is aligned with the inner surface of chute 16 providing a 
continuous track for the strap 20. A strap channel 74 is provided in face 
72 to receive strap 20 which forms a loop inside the strap chute 16. The 
strap free end 30 is fed around the strap chute 16 to overlap a portion of 
the strap loop at the front face 72. A sensing lever 76 is mounted in a 
T-shaped cavity 78 in support block 80. Lever 76 pivots in cavity 78 about 
pin 82. As illustrated in FIG. 6, lever 76 has an angled impingement face 
84 which projects slightly in front of the strap channel 74 and in the 
path of the strap free end 30. The vertical placement of lever 76 is 
chosen to provide the desired amount of overlap of the strap loop by the 
strap free end 30. When the strap 20 has been fed into the chute 16 to 
form a loop so that the strap free end 30 has overlapped the loop by the 
desired amount, the strap free end 30 impinges upon the impingement face 
84 of lever 76 and causes lever 76 to pivot about pin 82. The impingement 
face 84 is thus forced out of the path of the strap free end 30 to the 
position indicated by the dashed lines in FIG. 6. 
Lever 76 has an arm 86 on which is mounted an adjustment screw 88. Screw 88 
is set to contact a conventional spring-biased lever arm 90 of a limit 
switch 92. When the strap free end 30 causes lever 76 to rotate about pin 
82, screw 88 is forced against lever arm 90 to close or open, as the case 
may be, the electrical contacts in limit switch 92. The combination of the 
lever 76 and switch 92 thus comprise a sensor means for sensing the strap 
free end 30 when the loop has been formed in the chute. 
Through appropriate electrical control and power circuits, electrical 
solenoid 66 is maintained in the de-energized mode when the strap is being 
fed to form a loop and before the lever 76 is pivoted by the strap free 
end 30. When the lever 76 is tripped by the strap free end 30 upon 
formation of the loop, the electric solenoid 66 is energized against the 
action of spring 62 to pull pawl 38 into engagement with ratchet wheel 40 
to immediately lock the traction wheel 28 against further rotation, thus 
stopping the strap feeding process. 
A modification of the positive latching device of the present invention is 
illustrated in FIGS. 7 through 9. In this modification, a latch means for 
engaging the ratchet wheel is provided which does not require the use of 
an electric solenoid actuator. As illustrated in FIG. 7, a sensor means or 
sensing lever 112 is provided which is similar to the sensing lever 76 of 
the embodiment of FIG. 5 previously described. 
The sensing lever 112 is pivotally mounted about pin 114 in a T-shaped 
channel 116 in support block 117. A flexible cable assembly 118 is mounted 
adjacent a projecting arm 120 of the sensing lever 112. The cable assembly 
118 comprises a cable 122 contained in an outer shroud 124. The cable 122 
is loosely disposed within the shroud 124 for sliding therein. Shroud 124 
is secured near one end to the sensing lever 112 on block 117 by bracket 
128. The very end of cable 122 is secured in a cylindrical plug 130 which 
is disposed within a cylindrical journal 132 on lever arm 120. When the 
strap loop has been formed within the chute 16, the strap free end 30 
impinges upon the end of the sensing lever 112 and causes the sensing 
lever to rotate, or pivot, about pin 114 thereby pushing cable 122 along 
inside the shroud 124. 
As illustrated in FIGS. 8 and 9, a pawl assembly 134 and ratchet wheel 136 
are provided adjacent the housing 137 of the strapping machine. The other 
end of cable assembly 118 is connected to pawl assembly 134 for engagement 
with a ratchet wheel 136 (FIG. 8). As illustrated in FIG. 8, one end of 
the shroud 124 of cable assembly 118 is secured by a bracket 138 with 
screw or bolt 139 to a portion of the housing 137. The cable 122 is 
secured to an upper pawl member 142 which is pivotally mounted aobut pin 
144 projecting from a portion of the housing 137. Also pivotally mounted 
about the pin 144 is the lower pawl member 148 which is adapted to engage 
teeth 150 of the ratchet wheel 136 as in the manner illustrated in FIG. 9. 
A pawl bias spring 152 is disposed in compressive engagement between the 
upper pawl member 142 and the lower pawl member 148 and urges the lower 
pawl member 148 toward the ratchet wheel 136. However, a limiting screw 
154 is located on the longitudinal axis of the pawl bias spring 152 and is 
secured on one end, by threaded engagement, to lower pawl member 148. The 
other, or head end, of the limiting screw 154 passes freely through an 
aperture in the upper pawl member 142 and is not threaded thereto. The 
head of the limiting screw 154, when in contact with the upper pawl member 
142, prevents the pawl bias spring 152 from urging the lower pawl member 
148 away from the upper pawl member 142 beyond the length of the screw. 
A sensing lever return spring 156 is compressively engaged between a spring 
support 160 secured to a portion of the housing 137 and a shoulder 162 on 
the upper pawl member 142. The sensing lever return spring 156 thus 
continuously biases the upper pawl member 142 to pivot about pin 144 in a 
counterclockwise direction as viewed in FIG. 8. This, of course, causes 
cable 122 to slide through shroud 124 to maintain the sensing lever 112 in 
the position shown in FIG. 7 wherein it projects into the path of the 
strap free end 30. 
By appropriate choice of the sensing lever return spring 156, the entire 
pawl assembly 134 can be maintained in the position illustrated in FIG. 8. 
In this position, the lower pawl member 148 is disengaged from the ratchet 
wheel 136 and the cable 122 is pushed by the upper pawl member 142 to 
pivot the sensing lever 112 in the counterclockwise direction about pin 
114 so that the lever projects into the path of the strap free end 30. 
Further, the spring force of the sensing lever return spring 156 is chosen 
so that the spring will be overcome by the impingement of the strap free 
end 30 against the sensing lever 112. That is, the lever 112, when hit by 
the strap free end 30, pushes the cable 122 in the direction to cause the 
upper pawl member 142 to compress spring 156 and force the lower pawl 
member 148 into engagement with the ratchet wheel 136. When the ratchet 
wheel 136 is so engaged, the rotation of the ratchet wheel is terminated. 
The ratchet wheel 136 is an integral extension of the traction wheel (not 
shown in FIG. 8 but identical to the configuration of the traction wheel 
28 and ratchet wheel 40 illustrated in FIG. 2). Thus, the traction wheel 
rotation is terminated when the rotation of the ratchet wheel 136 is 
terminated to thereby stop the strap feeding process. 
As illustrated in FIG. 9, the ratchet wheel 136 can be also rotated in the 
direction to tension the strap loop and draw it tight about the package. 
In that case, the lower pawl member 148 is forced outwardly from the 
ratchet wheel 136 by the teeth 150 as the ratchet wheel rotates in the 
clockwise direction (as viewed in FIG. 9). The lower pawl member 148 is 
then forced toward the upper pawl member 142, compressing pawl bias spring 
152 in the process. Since the limiting screw 154 is threadingly engaged on 
one end with the lower pawl member 148 but is freely disposed on the other 
end within the upper pawl member 142, the head of the screw is moved 
outwardly away from its bearing engagement with the upper pawl member 142 
to assume the position shown by dashed lines in FIG. 9. 
In FIGS. 8 and 9, the sensing lever return spring 156 is shown 
compressively engaged with the shoulder 162 of the upper pawl member 142. 
Though not illustrated in FIG. 7, the sensing lever return spring could 
alternately be located adjacent the sensing lever 112 and secured thereto 
to directly urge the sensing lever to project into the path of the strap 
free end 30. 
It is seen that the novel strap feed stop mechanism of the present 
invention immediately terminates rotation of the strap feed traction wheel 
upon formation of a strap loop with the desired amount of free end 
overlap. Note that in the illustrated embodiments, since the traction 
wheel is mounted for rotation relative to the shaft, the drive motor and 
shaft can continue to rotate even though the traction wheel is restrained 
from rotating. The use of this novel mechanism in a strapping machine 
wherein the rotation of the traction wheel is instantly terminated while 
the drive motor is free to continue rotating prevents undesirable strap 
overfeed owing to the drive motor momentum that exists after the power to 
the motor has been switched off. 
The unique strap feed stop mechanism of the present invention can also be 
combined in a novel manner with a jam-clearing and torque sensing traction 
wheel assembly as will now be described. 
Upon formation of a strap loop, the strap sensing lever and limit switch 
illustrated in FIG. 5 will be tripped by the strap free end 30 to actuate 
the latch means (e.g., electric solenoid and pawl) as heretofore 
described. When this occurs, the ratchet wheel rotation is terminated 
immediately, thereby stopping the traction wheel feeding process. The 
restraint of the ratchet wheel against further rotation in the strap feed 
direction presents an "infinite" resistance to the driver plate 48. Thus, 
the driver plate 48 disengages from the driven plate 47 in the same manner 
as was heretofore described with respect to the disengagement resulting 
from increased strap feed resistance caused by an obstruction in the 
chute. This, of course, permits the drive shaft 42 to continue rotating 
and thus avoids locking the motor drive 46 to the stopped ratchet wheel 
40. Consequently, the drive motor 46 can continue turning at speed to 
furnish power to other mechanisms (not shown), if required. For example, 
if the strap were to be tensioned to tighten the loop by a second traction 
wheel (not shown) driven by the same drive motor 46 through an appropriate 
clutch and transmission mechanism (not shown), the tensioning process 
could then begin immediately wherein the second traction wheel would be 
driven by the still rotating motor drive 46. This would have the advantage 
of decreasing wear on the drive motor since the motor would not have to be 
stopped from rotating in the feeding direction and restarted to rotate in 
the opposite, tensioning direction. This would also decrease the total 
amount of time required to feed the strap and tension the loop since the 
drive motor would not have to be brought up to speed from a stopped 
condition at the start of the tensioning process. 
SECOND EMBODIMENT: STRAP END ABUTMENT 
When the strap free end hits an obstruction in the strap chute, the 
jam-clearing and torque sensing traction wheel assembly effects a novel 
and useful "flutter" response in the strap free end. This was previously 
described in the earlier section entitled "Jam-clearing and Torque Sensing 
Traction Wheel Assembly." It was explained that if a region of high 
friction or an obstruction is encountered in the strap chute by the strap 
free end as it is fed around the chute, the additional resistance caused 
by the obstruction is transmitted along the strap to the traction wheel 28 
and to the driven plate 47 (FIGS. 2 and 4). The driver plate 48 disengages 
from the driven plate 47 in response to the increased torque required to 
rotate the driven plate 47 when the obstruction is encountered in the 
chute. The feeding process is thus terminated, at least for an instant. 
Since the drive motor 46 is continuing to rotate, the driver plate 48 
continues to rotate until the recess 54 of the driver plate 48 re-engages 
the shoulder protrusions 53 in the driven plate 47. When this happens, the 
traction wheel 28 is again urged to rotate against the strap to move the 
strap forward. If the obstruction is still lodged within the strap chute, 
the driver wheel 48 again disengages from the driven wheel 47. As this 
process is repeated, owing to the speed of the rotation of the driver 
wheel 48, the effect is to cause a relatively rapid, on-again, off-again 
forward feeding force on the strap which causes the end of the strap to 
"flutter." The fluttering of the end of the strap can serve to knock the 
obstruction out of the strap chute or can cause the strap to pass under, 
around, or through the obstruction (or area of excessive friction) and 
then complete the path in the chute to form the loop. 
The "obstruction" discussed immediately above and in the earlier 
description of the jam-clearing and torque sensing traction assembly need 
not be restricted to any one particular area in the strap chute. For 
example, the obstruction can lie in or near the region of strap overlap, 
just ahead of, in, or beyond any joint forming mechanisms that may be 
employed to form a joint between the overlapped straps. In fact, an 
"obstruction" can be purposely designed near the region of the overlapping 
straps to provide a means for terminating the strap feeding. Such a 
specifically designed obstruction could also completely replace the 
previously described sensor means 34, including the movable sensing lever 
76, located on the front face of the strapping machine just beyond the 
region of strap overlap. 
In FIGS. 10 through 12, an abutment means 210 is illustrated. The abutment 
means 210 is positioned on the strapping machine at the same general 
location as the sensor means 34, illustrated in FIG. 1, just beyond the 
end of the strap overlap region. Specifically, with reference to FIG. 10, 
a strap abutment means or member 210 is illustrated as projecting from the 
front face 72 of the strapping machine strap chute. The strap channel 74 
is provided in the face 72 to receive the strap 20 which forms a loop in 
the strap chute with the strap free end 30 being fed around the strap 
chute to overlap a portion of the strap 20 at the front face 72 just below 
the abutment member 210. 
In operation, as the strap free end 30 is fed around the strap chute and 
overlaps a portion of the strap 20, it impinges upon the projecting 
abutment member 210. To prevent the strap free end 30 from slipping out of 
contact with the strap abutment member 210, the abutment member preferably 
has a downwardly depending lip 215. The abutment member 210 acts as an 
"infinite" resistance in the strap chute which is transmitted back through 
the strap 20 to the torque sensing clutch through the traction wheel 28 
and driven plate 47. As has been previously explained, the driver plate 48 
then disengages in response to the increased torque required to rotate the 
driven plate 47 against the abutment 210 so that the feeding of the strap 
is terminated. Until the traction wheel motor 46 (FIG. 2) is shut off and 
until the motor's rotational momentum has descreased to a negligible 
amount, the strap free end 30 would continue to be intermittently driven 
against the abutment member 210 and the strap free end 30 would "flutter" 
as was previously described. Consequently, suitable control means (not 
illustrated) can be provided to terminate the strap feed motor 46. 
Such control means may include a sensing lever, similar to sensing lever 76 
previously described and illustrated in FIGS. 1 and 5, which may be 
located in the strap chute ahead, or upstream, of the joint area. A limit 
switch associated with the sensing lever can be connected in the motor 
circuit to stop the motor when the strap free end impinges upon the 
sensing lever. The motor will continue to rotate under its momentum for a 
short period of time. The strap will thus be fed past the sensing lever 
and against the abutment member. Then, upon hitting the abutment member, 
the strap will transmit the abutment resistance, through the traction 
wheel, to the clutch assembly which will then disengage to prevent 
buckling of the strap in the manner that has been previously explained. 
With such a strap end abutment member 210, it is not necessary to provide 
for positive latching of the traction wheel. Thus, the ratchet-pawl latch 
mechanism (including actuator means 36, pawl 38, and ratchet wheel 40), 
described earlier and illustrated in FIGS. 2 through 4, need not be 
incorporated in the strapping machine, thus allowing a simpler machine 
design. Hence, it is seen that the use of a strap end abutment means 210 
in place of the movable sensing lever 76, when combined with the novel 
torque sensing clutch assembly of the present invention, eliminates the 
need for complicated and expensive drop-out gate devices (such as 
illustrated in Crosby et al. U.S. Pat. No. 2,915,003) or the ratchet/pawl 
latch mechanism. 
Of course, the effectiveness of a strap feed termination system 
incorporating the strap end abutment member 210 depends upon the 
combination of the various strap parameters, the rate of strap feed, and 
the size of the loop being formed. Obviously, with very flexible strap 
and/or with very large loops, the tendency of the strap to buckle inwardly 
when the strap free end impinges against the abutment member is greatly 
increased. However, in situations involving a suitable combination of 
strap section modulus, strap feed rate, and strap loop size, the permanent 
abutment structure of the present invention is effective for terminating 
strap feeding and eliminates the need for more complex mechanisms. 
From the foregoing, it will be observed that numerous variations and 
modifications may be effected without departing from the true spirit and 
scope of the novel concept of the invention. It is to be understood that 
no limitation with respect to the specific apparatus illustrated herein is 
intended or should be inferred. It is, of course, intended to cover by the 
appended claims all such modifications as fall within the scope of the 
claims.