Control mechanism for a feed and tension unit in a strapping apparatus

Information

  • Patent Grant
  • 6782679
  • Patent Number
    6,782,679
  • Date Filed
    Tuesday, May 14, 2002
    22 years ago
  • Date Issued
    Tuesday, August 31, 2004
    20 years ago
Abstract
Apparatus and methods for applying flexible straps around objects include a feed and tension unit a feed drive wheel and a feed pinch wheel, a primary tension drive wheel and a primary tension pinch wheel, and a secondary tension drive wheel and a secondary tension pinch wheel, wherein at least one of the pinch wheels is controllably biased against the respective drive wheel by a solenoid that is controlled in two stages: a first stage that provides a full feed or tensioning force and a second stage that provides a reduced feed or tensioning force by altering the pulse width modulation of the solenoid. In another embodiment, the three sets of wheels of the feed and tension unit are configured to provide a simplified “V-shaped” strap path that reduces bending of the strap, thereby reducing friction and consequent feeding difficulties. In another embodiment, the feed and tension unit includes inner and outer guides that form a strap channel through the feed and tension unit to provide easy access to the strap path for clearing the strap path in the event of a jam. In another embodiment, a 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. In another embodiment, a cutting assembly for severing strap material includes a press platen and a cutter having a first cutting blade along a first edge thereof and a second cutting blade along a second edge thereof, the cutter being removably and variably engaged to the press platen.
Description




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 Domey 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 engaged with the slotted cover that exerts a biasing force on the slotted cover to urge the slotted cover toward the closed position. The biasing force is small enough that a tensioning force in the strap material may overcome the biasing force and thereby actuate the slotted cover toward the open position to allow the strap material to escape from the guide passage during a tension cycle. During a feed cycle, the strap material exerts a closing force on an outer surface of the slotted cover, urging the slotted cover into the closed position. In another aspect, the slotted covers are pivotably mounted on guide pins that are approximately parallel to the path of the strap material within the guide passage.




In another aspect, a cutting assembly for severing strap material includes a press platen and a cutter having a first cutting blade along a first edge thereof and a second cutting blade along a second edge thereof, the cutter being removably and variably engaged to the press platen such that at least one of the first or second cutting blades is engageable with the strap material. In another aspect, at least one of the first and second edges is slanted at a slant angle with respect to an adjacent edge of the cutter.




These and other benefits of the present invention will become apparent to those skilled in the art based on the following detailed description.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a front elevational view and partial fragmentary view of a strapping machine under the prior art.





FIG. 2

is an isometric view of a strapping machine in accordance with an embodiment of the invention.





FIG. 3

is an isometric view of a sealing head in accordance with an embodiment of the invention.





FIG. 4

is a top elevational view of the sealing head of FIG.


3


.





FIG. 5

is a back elevational view of the sealing head of FIG.


3


.





FIG. 6

is an isometric view of a press platen and a cutter of the sealing head of FIG.


3


.





FIG. 7

is an isometric view of a main drive assembly in accordance with an embodiment of the invention.





FIG. 8

is a top elevational view of the main drive assembly of FIG.


7


.





FIG. 9

is a side elevational view of the main drive the assembly of FIG.





FIG. 10

is a first isometric view of a feed and tension unit in accordance with an embodiment of the invention.





FIG. 11

is a second isometric view of the feed and tension unit of FIG.





FIG. 12

is a partial front elevational view of a strap path of the feed and tension unit of FIG.


10


.





FIG. 13

is a partial isometric view of a primary pinch wheel and a proximity switch of the feed and tension unit of FIG.


10


.





FIG. 14

is an exploded isometric view of an accumulator in accordance with an embodiment of the invention.





FIG. 15

is a front elevational view of the accumulator of FIG.


14


.





FIG. 16

is a top elevational view of the accumulator of FIG.


14


.





FIG. 17

is an isometric view of a dispenser in accordance with an embodiment of the invention.





FIG. 18

is a top elevational view of the dispenser of FIG.


17


.





FIG. 19

is an isometric view of a track in accordance with an embodiment of the invention.





FIG. 20

is a partial sectional view of a straight section of the track of

FIG. 19

taken along line


20





20


.





FIG. 21

is an isometric view of a corner section of the track of FIG.


19


.





FIG. 22

is an exploded isometric view of the press platen and cutter of FIG.


6


.





FIG. 23

is an enlarged partially-exploded isometric view of a pair of inner and outer strap guides of the feed and tension unit of FIG.


10


.





FIG. 23A

is a cross-sectional view of the inner and outer guides of

FIG. 23

to illustrate the guide slot created by the inner and outer guides.





FIG. 24

is a cross-sectional view of the accumulator of

FIG. 15

taken along line


24





24


.





FIG. 25

is a partially exploded isometric view of a straight section of the track of FIG.


19


.




In the drawings, identical reference numbers identify identical or substantially similar elements or steps.











DETAILED DESCRIPTION OF THE INVENTION




The present disclosure is directed toward apparatus and methods for strapping bundles of objects. Specific details of certain embodiments of the invention are set forth in the following description, and in

FIGS. 2-25

, to provide a thorough understanding of such embodiments. A person of ordinary skill in the art, however, will understand that the present invention may have additional embodiments, and that the invention may be practiced without several of the details described in the following description.





FIG. 2

is an isometric view of a strapping machine


200


in accordance with an embodiment of the invention. The strapping machine


200


includes seven major subassemblies: a frame


210


, a control system


220


, a dispenser


250


, an accumulator


300


, a feed and tension unit


350


, a sealing head


400


, a drive assembly


500


, and a track


450


. The subassemblies are of modular construction, which allows them to be used in multiple frame configurations.




Throughout the following discussion and in the accompanying figures, the strap material is shown and referred to as a particular type of material, namely, a flat, two-sided, tape-shaped strip of material. This practice is adopted herein solely for the purpose of simplifying the description of the inventive methods and apparatus. It should be understood, however, that several of the methods and apparatus disclosed herein may be equally applicable to various types of strap material, and not just to the flat, two-sided, tape-shaped material shown in the figures. Thus, as used herein, the terms “strap” and “strap material” should be understood to include all types of materials used to bundle objects.




The overall operation of the strapping machine


200


will first be described with reference to various figures, and thereafter, the individual components will be described in detail. In brief, the operation of the strapping machine


200


involves paying off strap


202


from a strap coil


204


located on the dispenser


250


(FIGS.


17


-


18


), and feeding a free end


206


of the strap


202


through the accumulator


300


(FIGS.


14


-


16


), the feed and tension unit


350


(FIGS.


10


-


13


), the sealing head


400


(FIGS.


3


-


5


), and around the track


450


(FIGS.


19


-


20


). After the strap


202


is fed around the track


450


, the free end


206


is fed back into the sealing head


400


. At this point the strap


202


is in position to start a strapping cycle.




Upon the start of the strapping cycle, several sealing head cams


402


in the sealing head


400


(

FIGS. 3-5

) begin to rotate, forcing a left-hand gripper


404


to pinch the free end


206


of the strap


202


against an anvil


406


. After gripping the strap


202


in the sealing head


400


, the feed and tension unit


350


(

FIGS. 10-13

) retracts the strap


202


from the track


450


. As the strap


202


is pulled from the track


450


, the strap


202


is tensioned around a bundle of objects (not shown) located in a strapping station


208


(

FIG. 2

) by a feed and tension motor


361


(FIG.


10


). As the strap


202


becomes tight around the bundle, a primary tension pinch wheel


352


(

FIG. 10

) stops rotating. A proximity sensor


354


(

FIG. 11

) detects the lack of rotation of the primary tension pinch wheel


352


(

FIG. 12

) and starts a secondary tension process.




Preferably, the cams


402


operate as cycloidal cams allowing the sealing head


400


to operate smoothly at increased speeds and the cam follower pressure angles are minimized to extend cam life. As used herein, the term cycloidal cam means a cam with cycloidal displacement generated by taking a sinusoidal acceleration function that has a magnitude of zero at its beginning and end, and integrating the function to obtain the velocity and displacement of the follower.




Secondary tension is applied until a drive wheel clutch


356


(

FIGS. 7-8

) slips, at a predetermined set-point, and the sealing head


400


rotates far enough to grip the strap


202


with a right-hand gripper


408


. After the strap


202


is gripped by the right-hand gripper


408


, the tension on the free end


206


of the strap


202


is released and the strap


202


around the bundle is cut free from the coil


204


by a cutter


414


(FIGS.


3


and


6


). The two overlapping ends of the strap


202


are then heated by inserting a heater blade


410


(

FIG. 3

) between them and lightly pressing the straps against the blade


410


with a press platen


412


(FIG.


3


). The press platen


412


then lowers slightly and the heater blade


410


is removed from between the strap ends. Next, the press platen


412


presses both ends against the anvil


406


(

FIG. 3

) for bonding and cooling. As the sealing head cams


402


continue to rotate, the press platen


412


lowers slightly allowing the anvil


406


to open and release the sealed strap. After the strap is released, the anvil


406


is closed and the strapping cycle is completed by feeding strap


202


through the sealing head


400


, around the track


450


, back into the sealing head


400


and finally actuating a feed stop switch


416


(FIG.


3


).




Two modes of operation are available: manual and automatic. The manual mode applies single or multiple straps while an operator actuates a switch. The automatic mode applies a single strap or multiple straps when a switch is actuated by a moving bundle. The automatic mode is used in conveyor lines and in conjunction with other automated machinery.




As shown in

FIG. 2

, the frame


210


consists of a main support


212


, adjustable legs


214


, and cover plates


216


. The frame


210


provides structural support for all of the other sub-assemblies of the strapping machine


200


. In this view, the strap


202


is fed about the track


450


in a strap-feed direction


209


that is generally counter-clockwise.




The strapping machine


200


is controlled by a control system


220


that may include a programmable logic controller


222


(

FIG. 3

) that operates in conjunction with various input and output devices and controls the major subassemblies of the strapping machine


200


. Input devices may include, for example, momentary and maintained push buttons, selector switches, toggle switches, limit switches and inductive proximity sensors. Output devices may include, for example, solid state and general purpose relays, solenoids, and indicator lights. Input devices are scanned by the controller


222


, and their on/off states are updated in a controller program


224


. The controller


222


executes the controller program


224


and updates the status of the output devices accordingly. Other control functions of the controller


222


are described below in further detail.




In one embodiment, the programmable controller


222


and its associated input and output devices may be powered using a 24 VDC power supply. The controller


222


, power supply, relays, and fuses may be contained within a control panel (not shown). The momentary and maintained push buttons, selector switches, and toggle switches may be located on a control pendant or a control panel cover. The limit switches, inductive proximity sensors, and solenoids are typically located within the strapping machine


200


at their point of use. At least one indicator light may be mounted on the top of the track


450


and may light steadily to indicate an out-of-strap condition, and may flash to indicate a strap misfeed condition.




One commercially-available programmable controller


222


suitable for use with the strapping machine


200


is the T100MD1616+ PLC manufactured by Triangle Research International Pte Ltd in Singapore. This device includes sixteen NPN-type digital outputs, four of which are NPN Darlington Power Transistor types and twelve of which are N-channel power MOSFET types. Two of the outputs are capable of generating a Pulse Width Modulated (PWM) signal with a frequency and duty cycle determined in the programming software. Also included are four input channels of 10-bit analog-to-digital converters. Two of the input channels are buffered by operational amplifiers with a ×5 gain accepting analog signals of 0-1 full scale. The remaining two channels are unbuffered and accept 0-5 V full scale analog signals. The unit includes a stable 5 V (+/−1% accuracy) regulated DC power supply to be used as a voltage reference for the analog inputs. A single channel 8-bit digital-to-analog output utilizing a 0-20 mA current loop signal, also resides on the PLC.




The T100MD1616+ PLC has communication ports, including an RS232C port for program uploads, downloads and monitoring, a two-wire RS485 network port, a 14-pin LCD display port for possible future use as a diagnostic display driver, and a port for expansion. The PLC itself is controlled by a custom CPU that has both EEPROM and RAM memory backup. The controller program


224


used to program the controller


222


may, for example, include Trilogi programming software available from Triangle Research International Pte Ltd, and may include both ladder logic and Tbasic type code (described more fully at www.tri.com.sg/index.htm).





FIG. 3

is an isometric view of the sealing head


400


of the strapping machine


200


of FIG.


2


.

FIGS. 4 and 5

are top elevational and back elevational views, respectively, of the sealing head


400


of FIG.


3


.

FIG. 6

is an isometric view of the press platen


412


and the cutter


414


of the sealing head


400


of FIG.


3


. The sealing head


400


comprises a motor-driven main shaft


418


and a series of cams


402


which perform gripping, sealing and cutting functions. These cams


402


drive three sliding members


422


and three rotating arms


424


(FIG.


5


). One slide member


422


is coupled to the right-hand gripper


408


, another slide member


422


is coupled to the left-hand gripper


404


, and the third slide member


422


is coupled to the press platen


412


. The sliding members


422


perform the gripping, sealing and cutting functions, while the pivoting arms


424


move an inner slide


420


, the anvil


406


, and the heater blade


410


into and out of a strap path as required during a strapping cycle.





FIG. 22

is an exploded isometric view of the press platen


412


and cutter


414


of FIG.


6


. As shown in this view, the press platen


412


includes a pair of mounting nubs


411


, and the cutter


414


includes mounting recesses


413


. A spring


415


is disposed between the cutter


414


and the press platen


412


, one end of the spring


415


being partially disposed within a seating hole


417


disposed in the press platen


412


. The cutter


414


has cutting edges


419


at both ends, allowing the cutter


414


to be reversibly positioned on the press platen


412


for added operational life. In the embodiment shown in

FIG. 22

, the cutting edges


419


are slanted at an angle α. Although a wide variety of cutting edge angles α may be used, a cutting edge angle in the range of approximately 9 degrees or less is preferred.




During assembly, the spring


415


is compressed between the cutter


414


and the press platen


412


until the two mounting recesses


413


slideably engage two of the mounting nubs


411


. One may note that the cutter


414


has a pair of mounting recesses


413


situated near each end of the cutter


414


which allows the cutter


414


to be reversibly mounted onto the press platen


412


. The cutter


414


and the press platen


412


are then positioned securely between the left and right-hand grippers


404


,


408


with the pressure from these parts maintaining the compression of the spring


415


. The cutter


414


and press platen


412


are then engaged with the third slide member


422


. This arrangement provides the necessary scissors action to sever the strap


202


.




An advantage of the cutter


414


and press platen


412


assembly shown in

FIGS. 6 and 22

is that the cutter


414


is removably and replaceably mounted to the press platen


412


by slideably engaging onto the press platen


412


. This allows the cutter


414


to be more easily removed for replacement or maintenance than in the prior art devices. The reversibility of the cutter


414


also essentially doubles the useful life of the component.





FIG. 7

is an isometric view of a main drive assembly


500


in accordance with an embodiment of the invention.

FIGS. 8 and 9

are top and side elevational views, respectively, of the main drive assembly


500


of FIG.


7


. The main drive assembly


500


includes a main drive motor


502


that drives a sealing head drive belt


508


and a drive wheel belt


510


. The sealing head drive belt


508


and the drive wheel belt


510


are preferably “toothed” belts. The sealing head drive belt


508


is directly coupled to a spring clutch


504


. The drive wheel belt


510


is turned approximately 90 degrees on a pair of drive pulleys


512


and is coupled to the drive wheel clutch


356


. As shown in

FIG. 7

, the main drive motor


502


, the spring clutch


504


, and the drive wheel clutch


356


are operatively coupled to the controller


222


, such as, for example, by electrically conductive leads


223


.




One advantage of the main drive assembly


500


is that the drive wheel clutch


356


is driven by the drive wheel belt


510


, which is turned at an approximately 90 degree angle on the drive pulleys


512


. This arrangement, commonly referred to as a “mule drive,” eliminates a 90-degree gearbox commonly found in drive systems of prior art strapping machines. Thus, the complexity and costs of fabrication of the main drive assembly


500


are reduced, and reliability and maintainability is improved.




In the embodiments shown in the accompanying figures, the spring clutch


504


is a wrap spring clutch and the drive wheel clutch


356


is an electromagnetic clutch. Alternately, other spring clutch


504


and drive wheel clutch


356


embodiments may be used. The spring clutch


504


stops the sealing head cams


402


at the proper degree of rotation during each stage of the cycle and stops the cams


402


in their home position at the end of each cycle. As stated above, the drive wheel clutch


356


slips at a torque that is determined by the voltage supplied to a coil located within the electromagnetic drive wheel clutch


356


. The slip in the drive wheel clutch


356


determines the amount of secondary tension that is applied to the strap


202


.




The main drive motor


502


drives the sealing head


400


by means of the sealing head drive belt


508


and the spring clutch


504


(

FIGS. 7 and 8

) which is mounted over an end of the sealing head main shaft


418


(FIG.


3


). Rotation of the main shaft


418


causes the keyed cams


402


(

FIGS. 3 and 5

) to rotate and perform the necessary gripping, sealing and cutting functions. During a first period of rotation, the main shaft


418


rotates to the first of three stops on the spring clutch


504


, causing a cutter-gripper assembly


426


to grip the strap


202


and the inner slide


420


to move out of the strap path. The main drive motor


502


then tensions the strap about the bundle, as will be described more fully below. When the strap tensioning is complete, the controller


222


pulses the spring clutch


504


allowing the cams


402


to rotate in a second period of rotation.




During the second period of rotation the right-hand gripper


404


grips the tensioned strap just ahead of the feed stop switch


416


and the tension in the strap is then released. After the tension is released, the platen


412


and the cutter


414


(

FIGS. 6 and 22

) rise to cut the strap


202


and press the strap against the heater blade


410


. The cams


402


continue to rotate through a dwell section as the strap


202


melts on the heater blade


410


. After a predetermined time for melting has passed, the press platen


412


and the cutter


414


retract slightly allowing the heater blade


410


to retract.




After the heater blade


410


retracts, the press platen


412


rises again to press the two melted ends of the strap


202


together for cooling and sealing. The sealing head main shaft


418


continues to rotate during a third period of rotation until a clutch trigger


428


disengages the spring clutch


504


. The sealing head


400


maintains this position for a predetermined time until the controller


222


again energizes a spring clutch solenoid


506


(not shown) located within the spring clutch


504


. The continued rotation of the cams


402


releases the press platen


412


and drops the left and right-hand grippers


404


,


408


to their home positions. One of the cams


402


then pivots the anvil


406


out of the strap line past a pair of strippers


430


. As the anvil


406


pivots, the strippers


430


push the strap off of the anvil


406


. After the strap


202


is out of the sealing head


400


, the anvil


406


closes, and the cams


402


reach their home positions. At the home position the spring clutch


504


reaches the third and final stop as the feed stop switch


416


(

FIG. 3

) signals the controller


222


to begin another feed sequence.





FIG. 10

is a first isometric view of the feed and tension unit


350


in accordance with an embodiment of the invention.

FIGS. 11 and 12

are a second isometric view and a partial front elevational view, respectively, of the feed and tension unit


350


of FIG.


10


. As best seen in

FIG. 12

, there are three sets of wheels in the feed and tension unit


350


: (1) a primary tensioning set including a primary tension drive wheel


360


and a primary tension pinch wheel


352


, (2) a secondary tensioning set including a secondary tension drive wheel


362


and a secondary tension pinch wheel


364


, and (3) a feeding set including a feed drive wheel


366


and a feed pinch wheel


368


.




The feed and tension unit


350


pinches the strap


202


between each of the three sets of drive wheels and pinch wheels. The feed, primary tension, and secondary tension pinch wheels


366


,


360


,


362


are engaged against the strap


202


by a feed pinch solenoid


370




a


, a primary tension pinch solenoid


370




b


, and a secondary tension pinch solenoid


370




c


, respectively. The drive wheel clutch


356


is powered by a drive wheel belt


510


from the main drive motor


502


. The primary tension and feed drive wheels


360


,


366


are powered by a secondary drive belt


372


mounted on a feed and tension motor


361


. The secondary tension drive wheel


362


is powered by the drive wheel clutch


356


that is driven by the drive wheel belt


510


from the main drive motor


502


. As shown in

FIGS. 10 and 11

, the feed and tension motor


361


, and the solenoids


370




a


,


370




b


,


370




c


are operatively coupled to the controller


222


by conductive leads


223


.




Unlike prior art strapping machines which feed the strap around several bends in the feed and tension unit prior to reaching the track, the strapping machine


200


features a simplified strap path (

FIG. 12

) allowing the strap to be fed in a straighter path than previously achievable. The path begins at the supply dispenser


250


that is located on the opposite side of the strapping machine from the feed and tension unit. This position further enables the strap to travel in a less tortuous path. As shown in

FIG. 12

, the drive wheels


360


,


366


, and


362


are positioned in an approximately triangular orientation, with the strap


202


traversing an approximately “V-shaped” strap path having an included angle of in the range of approximately 20 degrees to approximately 40 degrees. Less bending of the strap reduces friction throughout the system, increasing the reliability of strap feeding. Less bending also reduces the tendency of the strap to permanently deform and cause feeding difficulties. Thus, the feed and tension unit


350


of the present invention advantageously reduces or eliminates kinks in the strap which lead to feeding difficulties. While the strapping machines of the prior art typically turned the strap through a total of 360 degrees or more prior to reaching the track, the feed and tension unit


350


greatly reduces the amount of turning of the strap. For example, in the embodiment shown in the accompanying figures, the strap is turned through between approximately 180 and approximately 220 degrees as the strap is initially fed from the dispenser


250


across the strapping machine to the sealing head


400


.




As the strap


202


passes through each set of pinch wheels, a plurality of inner guides


374


and a plurality of outer guides


376


keep the strap


202


in line with the sealing head


400


.

FIG. 23

is an enlarged partially-exploded isometric view of a pair of inner and outer strap guides


374


,


376


of the feed and tension unit


350


of FIG.


10


. As best viewed in

FIG. 23

, each “L-shaped” inner guide


374


has a roughly L-shaped cross-section and is coupled to a matching “L-shaped” outer guide


376


to form a strap channel


380


through which the strap


202


passes.

FIG. 23A

is a cross-sectional view of the inner guide


374


and outer guide


376


and illustrates the guide chamber formed by the inner and outer guides to guide the strap material


202


.




The inner and outer guides


374


,


376


are secured in position on a plurality of guide pins


378


which project from a back plate


382


(

FIG. 10

) of the feed and tension unit


350


by a plurality of retaining knobs


379


, although a variety of other securing devices may be used. In

FIG. 10

, one of the outer guides


376


is removed from the strap path adjacent to the primary tension pinch and drive wheels


352


,


360


to provide a view of one of the “L-shaped” inner guides


374


.




During a feeding sequence, the strap


202


is pinched between the feed drive and pinch wheels


366


,


368


. In one embodiment, a feed force applied by the feed drive and pinch wheels


366


,


368


is regulated by a pulse width modulated solenoid


370




a


in two stages: a first stage that provides a full feed force and a second stage that provides a reduced feed force by altering the pulse width modulation of the feed pinch solenoid


370




a


. Because the pinch force exerted by a solenoid


370




a


on the strap


202


varies with supplied voltage, supplying a pulse width modulated voltage signal to the solenoid


370




a


provides the ability to vary the force exerted by the solenoid


370




a


. As the force exerted by the solenoid


370




a


is decreased, the strap


202


is permitted to slip on the feed drive wheel


366


more easily with a decreased amount of feed drive force. Commercially-available solenoids suitable for this purpose include those solenoids available from Ledex® Actuation Products of Vandalia, Ohio.




It should be noted that the frequency of the pulses which are fed to the solenoid affects the operation and performance of the solenoid. Generally, as the frequency of the pulses is increased, the adjustability of the pinch force exerted by the solenoid is improved. For example, using the above-referenced solenoids available from Ledex® Actuation Products, a pulse frequency of 8000 Hz has been successfully used.




The feed drive and pinch wheels


366


,


368


feed the strap through the sealing head


400


, around the track


450


, and back into the sealing head


400


. When the free end


206


of the strap


202


reaches the sealing head


400


, the arrival of the free end


206


is detected by feed stop switch


416


, which transmits a feed stop signal to the controller


222


. The controller


222


then sends a feed pinch signal to the feed pinch wheel


368


to disengage the feed pinch wheel


368


from the strap


202


, and the feeding sequence is complete.




During a primary tensioning sequence, the strap


202


is pinched between the primary tension drive wheel


360


and the primary tension pinch wheel


352


. In a first primary tension stage, the primary tension solenoid


370




b


engages the primary tension pinch wheel


352


against the primary tension drive wheel


360


with full pinch force to ensure that the primary tensioning solenoid engages and the strap


202


is pulled free of the track


450


. The pinch force is then reduced during a second primary tension stage by altering the pulse width modulation of the primary tension solenoid


370




b


. As the strap


202


is pulled tightly around the bundle during the primary tensioning sequence, the primary tension pinch wheel


352


stops rotating due to the slippage of the strap on the primary tensioning drive wheel


360


.




Using pulse width modulation to control the pinch forces exerted by the solenoids


370




a


,


370




b


during feeding and primary tensioning of the strap advantageously allows the operator a larger range of adjustment than is possible with a mechanical, single force adjustment system of the prior art. The two-stage force operation provides improved controllability of the strap


202


movement, including allowing the strap


202


to be quickly accelerated and to be easily stopped as required by the operator.





FIG. 13

is an isometric view of the primary tension pinch wheel


352


and the proximity sensor


354


of the feed and tension unit


350


of FIG.


10


. The proximity sensor


354


is operatively coupled to the controller


222


. The proximity sensor


354


monitors the primary tension pinch wheel


352


during primary tensioning, such as by monitoring the passing of notches in the wheel


352


, to detect the stall of the primary tension pinch wheel


352


. The proximity sensor


354


transmits signals to the controller


222


. As the signals from the proximity sensor


354


indicate that the primary tension pinch wheel


352


is not turning due to the slippage of the strap


202


on the primary tension drive wheel


360


, the controller


222


starts a secondary tensioning sequence.




The secondary tensioning sequence begins by pinching the strap between the secondary tension pinch wheel


364


and the secondary tension drive wheel


362


. Then, the secondary tension drive wheel


362


is driven by the drive wheel clutch


356


until the drive wheel clutch


356


starts to slip. After the strap


202


is tensioned to the point that the drive wheel clutch


356


slips, the controller


222


permits a predetermined amount of time to pass to allow the strap to be cut and sealed as described above. The feeding sequence may then be repeated.




An advantage of the strapping machine


200


is that the pinch wheels


352


,


364


,


368


are actuated by the solenoids


370




a


,


370




b


,


370




c


. Using a two-stage pulse width modulated (PWM signal, the solenoids are adjustably controllable by the user during strapping machine


200


operation. During the first stage, the solenoid is given a PWM signal at a constant duty cycle. For the second stage, the solenoid is controlled using a PWM signal with a duty cycle that is user-adjustable via, for example, a potentiometer. Since the average voltage seen by the solenoid is determined by the duty cycle, varying the duty cycle will vary the amount of force the solenoid pulls. Thus, the pinch wheels


352


,


364


,


368


may be adjustably controlled during operation of the strapping machine


200


, eliminating the labor-intensive process of mechanical re-adjustment of the pinch wheels


352


,


364


,


368


and the associated downtime of the strapping machine.





FIG. 14

is an exploded isometric view of an accumulator


300


in accordance with an embodiment of the invention.

FIGS. 15 and 16

are front and top elevational views, respectively, of the accumulator


300


of FIG.


14


.

FIG. 24

is a cross-sectional view of the accumulator


300


of

FIG. 15

taken along line


24





24


. The accumulator


300


includes a first and second sidewalls


302


,


304


that substantially enclose a chamber


306


that stores strap for rapid feeding, as well as for temporarily storing of the strap


202


that is drawn back in the tensioning process. The second sidewall


304


is incrementally adjustable by placing retaining pins


308


in a series of holes


310


located in shafts


312


that protrude from the first sidewall


302


to accommodate different sizes of strap


202


. Pin holders


309


are attached to the second sidewall


304


which engage the retaining pins


308


and fix the position of the second sidewall


304


on the shafts


312


.




The chamber


306


is substantially enclosed by the first sidewall


302


and the adjustable second sidewall


304


. A pair of end walls


320


extend vertically between the first and second sidewalls


302


,


304


. A top wall


322


extends horizontally along between the first and second sidewalls


302


,


304


, the top wall


322


having the top entrance


316


where strap


202


is fed into and pulled out of the accumulator unit


300


. An “L” shaped wand


324


extends between the first and second sidewalls


302


,


304


along the bottom of the chamber


306


. The wand


324


is pivotally attached to the first sidewall


302


.




In operation, an accumulator motor


330


(

FIG. 14

) drives an accumulator drive wheel


332


to feed the strap


202


between the accumulator drive wheel


332


and an accumulator pinch wheel


334


. An accumulator feed switch


336


(

FIG. 14

) is positioned proximate the accumulator drive and pinch wheels


332


,


334


to detect the presence of the strap


202


and to transmit a control signal to the accumulator motor


330


. As the chamber


306


fills with strap


202


, the wand


324


is pushed downwardly by the weight of the strap


202


, pivoting the wand


324


into contact with an indicator switch


326


(FIG.


15


). The indicator switch


326


then transmits a signal to the controller


222


to shut off the accumulator motor


330


, as described more fully below.




Alternately, during an automatic feeding mode, a strap diverter


314


covers a top entrance


316


of the chamber


306


. When strap


202


is fed into the strapping machine


200


by the accumulator motor


330


, a diverter solenoid


318


(

FIG. 14

) pulls the strap diverter


314


over the top entrance


316


of the chamber


306


, diverting the strap


202


directly into the feed and tension unit


350


and around the track


450


.




As best seen in

FIG. 24

, the accumulator


300


advantageously allows the width w of the chamber


306


and the top entrance


316


to be adjusted easily and quickly to accommodate varying widths of strap


202


. Unlike prior art apparatus that have accumulator sidewalls that are solidly affixed to form a single chamber size, the accumulator


300


of the present invention includes shafts


312


having a plurality of holes


310


placed at increments to match various commonly used strap sizes. Thus, the position of the second sidewall


304


with respect to the first sidewall


302


may be quickly and easily varied by removal of the retaining pins


308


, repositioning the second sidewall


304


at the desired location, and replacement of the retaining pins


308


within the desired holes


310


. The pin holders


309


then engage against the retaining pins


308


and fix the position of the second sidewall


304


on the shafts


312


. This mounting configuration allows the adjustment of the accumulator without having any additional parts, such as spacers between the first and second sidewalls


302


,


304


.





FIG. 17

is an isometric view of a dispenser


250


in accordance with an embodiment of the invention.

FIG. 18

is a top elevational view of the dispenser


250


of FIG.


17


. The dispenser


250


includes a mounting shaft


252


extending outwardly from the frame


210


between an inner hub


254


and an outer hub


256


. A spring brake


258


is operatively coupled to the mounting shaft


252


and to the frame


210


. When actuated, the brake


258


allows the rotation of the mounting shaft


252


. A mandrel


260


is rotatably mounted on the mounting shaft


252


and supports the inner hub


254


and the outer hub


256


. Strap


202


is routed from the strap coil


204


around a first pulley


262


and a second pulley


264


and over a strap exhaust switch


266


.




As strap


202


is required in the accumulator


300


, the accumulator motor


330


is energized and the dispenser brake


258


released, allowing the strap coil


204


to spin freely and strap


202


to feed into the chamber


306


. In this embodiment, the brake


258


releases the strap coil


204


to spin only when power is supplied to the brake


258


. When the strap coil


204


is depleted, the strap exhaust switch


266


is no longer actuated which stops the strapping machine


200


until the strap coil


204


is replenished. A braking circuit is used to prevent the accumulator motor


330


from drawing the free end


206


of the strap into the accumulator


300


. The remaining loose tail of strap can then be pulled out of the accumulator


300


before a new strap coil is installed. The empty strap coil


204


is replaced by removing an outer hub securing nut


268


and the outer hub


256


, and then removing the strap coil core (not shown) from the mandrel


260


. Next, a fresh strap coil


204


is placed on the mandrel


260


with the strap


202


wound in a clockwise direction. Finally, the outer hub


256


and the outer hub securing nut


268


are replaced and the nut tightened securely.




To begin feeding the strap


202


, the free end


206


is removed from the strap coil


204


, threaded around the first pulley


262


, through the strap exhaust switch


266


, around the second pulley


264


and between the accumulator drive wheel


332


and the accumulator pinch wheel


334


. As the strap


202


is placed between the accumulator wheels


332


,


334


, the accumulator feed switch


336


is actuated causing the accumulator feed solenoid to actuate, thus feeding the strap over the accumulator and into the track.




When enough force is applied to the wand


324


by the weight of the strap


202


accumulating in the chamber


306


, the wand


324


moves downwardly to actuate the indicator switch


326


, indicating that the accumulator unit


300


is full. In response to this signal, the controller


222


de-energizes the accumulator motor


328


and the dispenser brake


330


to halt the accumulator filling sequence. A time delay occurs between when the dispenser brake


330


is de-energized and when the accumulator motor


328


is de-energized to take up any slack in the strap coil


204


.





FIG. 19

is an isometric view of a track


450


in accordance with an embodiment of the invention.

FIG. 20

is a partial sectional view of a straight section


452


of the track


450


of

FIG. 19

taken along line


20





20


.

FIG. 21

is an isometric view of a corner section


454


of the track


450


of FIG.


19


.

FIG. 25

is a partially exploded isometric view of a straight section


452


of the track


450


of FIG.


19


. During feeding, after the strap


202


exits from the sealing head


400


, it is pushed completely around the track


450


and then back into the sealing head


400


. The track


450


directs the strap


202


around the strapping station


208


.




The track


450


includes a plurality of straight sections


452


and a plurality of corner sections


454


. As shown in

FIGS. 19 and 20

, each straight section


454


includes a guide support


455


at each end of the straight section


454


. A straight slotted cover


456


and a straight backplate


457


are coupled to the straight supports


455


to form a portion of a guide passage


462


that retains the strap


202


during feeding. Each straight slotted cover


456


includes a straight inner surface


472


on the inner circumference of the guide passage


462


, and a straight outer surface


474


on the outer circumference of the guide passage


462


.




As best seen in

FIGS. 20 and 21

, the straight supports


455


and the corner supports


454


are keyed to fit on a raised “T” section


459


of an outer arch


458


. The outer arch


458


forms a frame for the other components of the track


450


. As the strap


200


is tensioned around the bundle, the straight and corner slotted covers


456


,


463


open, allowing the strap


202


to pull clear of the guide passage


462


.

FIG. 20

illustrates the open position of the slotted cover


456


in phantom to assist in a more complete understanding of the invention. As the strap


202


clears the guide passage


462


, each of the straight and corner slotted covers


456


,


463


is closed by the springs


461


and becomes ready for the strap


202


to be fed again. The V-shape of the guide passage


462


in the corner section


454


helps assure that the strap removal begins in the corner sections


454


rather than in the straight sections


452


of the track


450


. When the strap


202


(see

FIG. 20

) is removed from the track


450


, the V-shape of the guide passage


462


in the corner section


454


causes the track cover


463


to begin opening in the corner section


454


. As the strap


202


begins to separate from the track


450


in the corner sections


454


, the V-shaped guide passage


462


imparts a slight twist to the strap to start opening the straight slotted


456


(see

FIG. 20

) in the straight sections


452


of the track


450


.




As shown in

FIG. 21

, each corner section


454


includes a corner slotted cover


463


and a corner backplate


465


coupled to a plurality of guide supports


455


. The corner slotted cover


463


and corner backplate


465


form a portion of the guide passage


462


therebetween. Each corner slotted cover


453


includes a corner inner surface


476


on the inner circumference of the guide passage


462


, and a corner outer surface


478


on the outer circumference of the guide passage


462


. In this embodiment, the corner slotted cover


463


and the corner backplate


465


are coupled to the guide supports


455


using a four-bar linkage assembly


469


that permits the corner slotted cover


463


to pivotably open to release the strap


202


from the guide passage


462


. Although alternate embodiments for pivotably mounting the corner slotted covers


463


may be conceived, in the embodiment shown in

FIG. 21

, the inner bars


468


(one shown) of the four-bar linkage assembly


469


have an enlarged opening


470


to permit the corner slotted cover


463


to pivotably open about an axis of rotation that is oriented approximately 45 degrees from the horizontal.




As best shown in

FIG. 25

, the straight slotted cover


456


and the straight backplate


457


are spring-loaded by a plurality of springs


461


. The straight slotted covers


456


and the straight backplates


457


are hingeably engaged on pivot pins


467


that are approximately parallel to the path of the strap


202


in the guide passage


462


. The pivot pins


467


are inserted through corresponding apertures


467




a


and


467




b


in the straight slotted cover


456


and straight backplate


457


, respectively, and rotate about an axis defined by the longitudinal axis of the pivot pins


467


. The pivot pins


467


are retained in position by snap-on retainers or any other convenient retainer element.




The springs


461


are inserted through a corresponding aperture


461




a


in the straight backplate


457


and are coupled to the straight slotted cover


456


by a spring retaining pin


466


. In an exemplary embodiment, the spring retaining pins


466


are identical to the pivot pins


467


and are retained within corresponding apertures


466




a


in the straight slotted cover


456


by the snap-on retainers. The springs


461


are thus coupled on a proximal end to the straight slotted cover


456


by the spring retaining pins


466


and are retained within the aperture


461




a


by an enlarged distal end, sometimes referred to as a circle cotter. This arrangement allows the straight slotted cover


456


to pivot open and release the strap


200


(see

FIG. 20

) and automatically close due to the spring force exerted on the straight slotted cover by the springs


461


. Although various sizes of straight slotted covers


456


may be employed, in the embodiment shown in

FIGS. 20 and 25

, the guide passage


462


is sized to receive strap sizes varying from approximately 5 mm to approximately 15 mm.




One advantage of the track


450


of the present invention is the modular construction of the straight and corner sections


452


,


454


which allows the track


450


to be incrementally extended in length and height. Because the straight and corner sections


452


,


454


are keyed to fit a raised section


459


of the outer arch


458


, these components form an easily assembled slide-together arch system, enabling the size of the track


450


to be easily modified for various combinations of length and height. Thus, the size of the strapping station


208


may be quickly and efficiently modified for a variety of bundle sizes.




Another advantage of the track


450


is that by pivoting the straight slotted covers


456


parallel to the strap path, and by pivoting the corner slotted covers


463


on the four-bar linkage assemblies


469


, each individual straight and corner section


452


,


454


may open using only the forces exerted by the strap


202


as it is tightened during tensioning. During the tension cycle, the strap


202


is drawn against the straight inner surfaces


472


and the corner inner surfaces


476


, forcing the straight slotted covers


456


and corner slotted covers


463


to pivotably open in the manner described above. Thus, the track


450


does not require complex hydraulic or pneumatic actuation systems to open the track to release the strap during tensioning. This reduces costs and simplifies maintenance of the track and strapping machine.




A further advantage of the track


450


is that, in the embodiment shown in

FIGS. 19 through 22

, the forces exerted by the strap on the straight slotted covers


456


and corner slotted covers


463


during the feed cycle assist in keeping the track closed during feeding. During the feed cycle, the strap


202


pushes outwardly on the straight outer surfaces


474


and the corner outer surfaces


478


to create a moment (i.e., a force vector) that forces the straight slotted covers


456


and the corner slotted covers


463


toward the closed position. This aspect of the invention reduces misfeeds of the strap, and eliminates the need for complex hydraulic or pneumatic actuation systems to close the track and keep it closed during the feed cycle.




The detailed descriptions of the above embodiments are not exhaustive descriptions of all embodiments contemplated by the inventors to be within the scope of the invention. Indeed, persons skilled in the art will recognize that certain elements of the above-described embodiments may variously be combined or eliminated to create further embodiments, and such further embodiments fall within the scope and teachings of the invention. It will also be apparent to those of ordinary skill in the art that the above-described embodiments may be combined in whole or in part with prior art methods to create additional embodiments within the scope and teachings of the invention.




Thus, although specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. The teachings provided herein of the invention can be applied to other methods and apparatus for strapping bundles of objects, and not just to the methods and apparatus for strapping bundles of objects described above and shown in the figures. In general, in the following claims, the terms used should not be construed to limit the invention to the specific embodiments disclosed in the specification. Accordingly, the invention is not limited by the foregoing disclosure, but instead its scope is to be determined by the following claims.



Claims
  • 1. In an apparatus for bundling one or more objects with a strap material, a feed and tension unit comprising:a feed drive roller and a feed pinch roller controllably biasable toward the feed drive roller to pinchably engage the strap material therebetween; a first tension drive roller and a first tension pinch roller controllably biasable toward the first tension drive roller to pinchably engage the strap material therebetween; and a second tension drive roller and a second tension pinch roller controllably biasable toward the second tension drive roller to pinchably engage the strap material therebetween; wherein the feed drive roller, the first tension drive roller, and the second tension drive roller are positioned in an approximately triangular orientation; and wherein at least one of the first and second tension pinch rollers is coupled to a solenoid that controllably biases the first and/or second pinch roller against the corresponding first and second tension drive roller based on a tension pinch signal supplied to the solenoid, the tension pinch signal having a first stage that provides a full pinch force and a second stage that provides a reduced pinch force.
  • 2. The apparatus of claim 1 wherein the feed pinch roller is coupled to a solenoid that controllably biases the feed pinch roller against the feed drive roller based on a feed pinch signal supplied to the solenoid, the feed pinch signal being configured to controllably feed the strap material.
  • 3. The apparatus of claim 1 wherein at least one of the first and second tension pinch rollers is coupled to a solenoid that controllably biases the first and/or second pinch roller against the corresponding first and second tension drive rollers based on a tension pinch signal supplied to the solenoid, the tension pinch signal being configured to controllably tension the strap material about the one or more objects.
  • 4. In an apparatus for bundling one or more objects with a strap material, a feed and tension unit comprising:a feed drive roller and a feed pinch roller controllably biasable toward the feed drive roller to pinchably engage the strap material therebetween; a first tension drive roller and a first tension pinch roller controllably biasable toward the first tension drive roller to pinchably engage the strap material therebetween; and a second tension drive roller and a second tension pinch roller controllably biasable toward the second tension drive roller to pinchably engage the strap material therebetween; wherein the feed drive roller, the first tension drive roller, and the second tension drive roller are configured to direct the strap material along a strap path having an approximate V-shape with an included angle in the range of approximately 20 degrees to approximately 40 degrees.
  • 5. In an apparatus for bundling one or more objects with a strap material, a feed and tension unit comprising:a motor; a drive roller rotatably coupled to the motor and a pinch roller controllably biasable toward the drive roller to pinchably engage the strap material therebetween; wherein the pinch roller is coupled to a solenoid that controllably biases the pinch roller against the drive roller based on a pinch signal supplied to the solenoid, the pinch signal having a first stage that provides a full pinch force and a second stage that provides a reduced pinch force, and further comprising a plurality of inner guides positioned proximate the drive roller, and a plurality of outer guides removably and adjustably positioned proximate the inner guides to form a strap channel therebetween.
  • 6. The apparatus of claim 5, further comprising a back plate having a plurality of guide pins projecting therefrom, the inner and outer guides being removably and adjustably secured to the guide pins.
CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 09/454,912, filed Dec. 2, 1999, now U.S. Pat. No. 6,415,712.

US Referenced Citations (34)
Number Name Date Kind
3118368 Lems Jan 1964 A
3179037 Cranston, Jr. et al. Apr 1965 A
3447448 Pasic Jun 1969 A
3566778 Vilcins Mar 1971 A
3752058 Lems Aug 1973 A
3768396 Coleman Oct 1973 A
3884139 Pasic May 1975 A
4011808 Aoki et al. Mar 1977 A
4120239 Pasic et al. Oct 1978 A
4155799 Matsushita et al. May 1979 A
4244773 Siebeck et al. Jan 1981 A
4278014 Knieps Jul 1981 A
4387631 Pasic Jun 1983 A
4516488 Bartzick et al. May 1985 A
4520720 Urban et al. Jun 1985 A
4569186 Mori et al. Feb 1986 A
4605456 Annis, Jr. Aug 1986 A
4625635 Lewis Dec 1986 A
4697510 Cranston, III et al. Oct 1987 A
4712357 Crawford et al. Dec 1987 A
4724659 Mori et al. Feb 1988 A
4781110 Sakaki et al. Nov 1988 A
4867053 Kawai et al. Sep 1989 A
4955180 Sakaki et al. Sep 1990 A
5146847 Lyon et al. Sep 1992 A
5187656 Kurakake Feb 1993 A
5251544 Abrams Oct 1993 A
5287802 Pearson Feb 1994 A
5379576 Koyama Jan 1995 A
5414980 Shibazaki et al. May 1995 A
5560187 Nagashima et al. Oct 1996 A
5613432 Hoshino Mar 1997 A
5778772 Schwede Jul 1998 A
5809873 Chak et al. Sep 1998 A
Foreign Referenced Citations (9)
Number Date Country
38 41 884 Jun 1990 DE
287 152 Feb 1991 DE
44 21 661 Jan 1996 DE
0 695 687 Feb 1996 EP
2 615 480 Nov 1988 FR
2 226 427 Jun 1990 GB
8011816 Jan 1996 JP
WO 9510452 Apr 1995 WO
WO 9822348 May 1998 WO