BACKGROUND OF INVENTION U. S. Patent No. 3,059,670 to Charles E. Burford and Leonard W. Burford entitled"WIRE TWISTING TOOL"; U. S. Patent No. 3,138,904 to Earl E. Burford entitled"METHOD AND APPARATUS FOR TYING PACKAGES AND WRAPPING MATERIALS ;"U S. Patent No. 3,919,829 to Leonard W. Burford and Charles C. Burford entitled"APPARATUS FOR TYING PACKAGES AND WRAPPING MATERIALS ;" U. S. Patent No. 4,856,258 to Charles E.

Burford and Jimmy R Frazier entitled"WIRE TYING DEVICE" ; and U. S. Patent No. 5,483,134 to Jimmy R Frazier, John D. Richardson and Greg P. Coxsey entitled"RIBBON SENSING DEVICE FORBAG TYER"disclose automatic bag closing and tying machines used for closing a flexible bag by attaching and twisting a wire-like ribbon about the neck of the bag.

Bag tying devices of the type disclosed in the aforementioned patents are commercially available from Burford Corporation of Maysville, Oklahoma The tying devices are generally constructed to receive packages such as loaves of bread at speeds of for example one hundred

(100) packages per minute. A ribbon of wire, encased in a covering of paper or plastic, is pulled from a roll, wrapped around the neck of the bag, cut and twisted to form a reclosable seal.

U. S. Patent No. 4,797,313 discloses an essentially organic, non-metallic ribbon for use as a twist tie comprising polymeric material exhibiting glass/rubber transitional behavior.

Polymeric ribbons deformed under tensile stress at 25 degce (s) exhibit yield stress between about 500 and 9,000 psi. Discrete lengths of ribbon are capable of being disengagedly formed into fastly held twist ties by mtationally deforming terminal ends of said lengths about each other.

The disclosure states that the ribbons can comprise polymers, such as polyalkylene terephthalates, polyvinylchlorides, styrene-acrylonitrile copolymers and polystyrenes. Optional polymeric materials include elastomeric impact modifiers and plasticizers. The patent states that the ribbon was utilized in an automatic bag closing and tying machine (model 50-7, Burford Corporation) at packaging rate of 60 bags per minute. The machine produced tight ties having between 1 and 11/2 twists.

U. S. Patent No. 5,342,687 discloses a non-metallic coreless twist-tie formed by extruding polymeric material and then drawing the material at a rate of more than about 2.5 times. The polymer is described as being formed from polymeric resin having a degree of crystallization of about 10% to 60% at a crystallized temperature range of about 100 degree (s) C. to 250 degree (s) C. and can also include a quantity of fine glass beads.

Heretofore automatic bag closing and tying machines have been configure for use with wire tie material. Non-metallic coreless twist-tie ribbon has a different cross-sectional profile and physical characteristics that may result is slippage of the ribbon in the twister hook, loose ties and some times disengagement of the end of the ribbon from the holder.

SUMMARY OF INVENTION The bag neck tying device disclosed herein incorporates a bag neck gathering mechanism comprising motor driven gathering belts for moving a bag neck along a path in a plane into engagement with a bag stop controlled by an electric brake positioned adjacent a ribbon holder- shear assembly which holds the free end of a ribbon of tie material. A motor driven needle wraps the strand of tie material around the gathered neck of the bag, and a motor driven twister hook assembly engages the free end and the running end of the ribbon adjacent the gathered neck for twisting the ribbon.

Independently controlled bi-directional, brush type servomotors are mounted in the separate subassemblies of the tying device. Each of the servomotors is controlled by a solid state DC motor controller in a closed loop feedback system under the control of a multi-channel microcontroller which precisely starts, controls and stops each of the servomotors in a pre-assigned sequence for each cycle of the tying apparatus.

An improved holder shear assembly incorporates a V-shaped groove formed in the holder and a V-shaped rib formed on a gripper finger such that the ribbon is contacted at several different areas before the ribbon is cut. As the gripper finger is rotated it pushes the ribbon into the comer of a holder cutting area. Tension on the ribbon extrudes the ribbon and grabs to pre-hold the ribbon. As the gripper finger rotates further, the ribbon is molded and bent over a cutting edge on the holder. This causes the ribbon to be securely held between surfaces on the gripper finger and the holder before the ribbon is cut.

The V-shaped groove in the holder and the V-shaped rib on the gripper finger are not parallel to each other. Consequently, increasing the tension on the ribbon increases the gripping action.

A shuttle bar connected for moving the gripper finger is mounted in a resilient bushing such that different gauges of wire or wireless ribbon can be used with the holder shear assembly without requiring adjustment of cams and other actuating mechanisms.

A ribbon guide is mounted adjacent the twister hook and positioned such that rotation of the twister hook draws tails of a severed section of ribbon across the guide surface so that it is positioned at an angle of approximately 90° relative to the twister hook allowing the twister hook to securely engage the tails of the ribbon to prevent slippage between the ribbon and the twister hook. When the ribbon is securely gripped by the twister hook the ribbon is twisted a predetermined number of twists between the twister hook and the neck of a bag encircled by the ribbon. This gripping action draws the ribbon material tight around the gathered neck of a bag.

The following disclosure is provided to illustrate specific embodiments and aspects of this invention but does not imply any limitation of the scope of the invention.

DESCRIPTION OF THE DRAWINGS Drawings of a preferred embodiment of the invention are annexed hereto so that the invention may be better and more fully understood, in which: Figure 1 is a perspective view illustrating the front of the bag neck tying device; Figure 2 is a diagrammatic front elevational view; Figure 3 is a diagrammatic rear elevational view; Figure 4 is an end view looking generally in the direction of the arrows along line 4-4 in Figure 2; Figure 5 is a diagrammatic end view illustrating the discharge end of the bag neck tying device, looking in the direction of the arrows along line 5-5 in Figure 2; Figure 6 is a top plan view, looking in the direction of the arrows along line 6-6 in Figure 2, parts being broken away to more clearly illustrate the details of construction; Figure 7 is a wiring diagram of the closed loop microcomputer controlled control system; Figure 8 is a graphic representation of the sequence of operation of the needle, hook and shear assemblies during a complete cycle of operation; Figure 9 is a fragmentary perspective view of a twister hook and ribbon guide plate; Figure 10 is a fragmentary perspective view of the twister hook assembly and the holder shear assembly; Figure 11 is a diagrammatic perspective view of the holder shear assembly in an inverted position; Figure 12 is a diagrammatic view indicating the angular relationship of surfaces on the holder; and Figure 13 is a diagrammatic view illustrating a pinch angle between a gripper finger and holder.

Numeral references are employed to designate like parts throughout the various Figures of the drawing.

DESCRIPTION OF A PREFERRED EMBODIMENT The wire tying device, generally designated by the numeral 10, in FIGS. 1 and 2 of the drawing is preferably of the type disclosed in U. S. Patent No. 5,483,134, that issued January 9, 1996, to Frazier, et aL the disclosure of which is incorporated herein by reference for all purposes.

As will be hereinafter more fully explained, improvements in the twister hook assembly 50 and a

holder-shear assembly 60 are incorporated into the device to provide improved performance when different types of ribbon or ribbon constructed of different materials are used to tie bags.

The wire tying device is mounted adjacent the side of a conveyor 300 of the type disclosed in Burford U. S. Pat. No. 3,138,904 and Burford U. S. Pat. No. 3,919,829, the disclosures of which are incorporated herein by reference in their entirety for all purposes. Conveyor 300 carries for example, loaves 125 of bread to, through and out of wire tying device 10 in rapid succession.

Conveyor 300 is well known to persons skilled in the art and further description thereof is not deemed necessary except in connection with the drive mechanism as will be hereinafter more fully explained. It should be appreciated that other and further structures may form the conveyor.

Referring to Figure 1 of the drawing, the numeral 20 generally designates a bag gathering apparatus for moving a bag 125 along a path 12 to a position adjacent a needle assembly 40, a twister hook assembly 50 and a holder-shear assembly 60. As will be hereinafter more fully explained, the free end of a ribbon 15 is gripped in a holder-shear assembly 60. The neck of the bag moves through a slot 122 between upper face plate 16 and lower face plate 17 for drawing the bag 125 to a controlled tension about the contents. Needle assembly 40 wraps the ribbon 15 about the gathered neck of the bag and twister hook 50 is actuated for twisting a portion of the ribbon 15 about the neck of the bag 125. It should be noted that the ribbon 15 may be constructed of wire enclosed in paper or plastic or it may comprise a ribbon of plastic or any other material. The strand of ribbon 15 extends around one or more pulleys 41,41a and 41b, mounted on shafts 41 a', from a spool 41c of tie material.

The mounting for spool 41c is similar to that disclosed in U. S. Patent No. 3,919,829 entitled"APPARATUS FOR TYING PACKAGES AND WRAPPING MATERIALS", the disclosure of which is incorporated herein by reference in its entirety for all purposes. However, it will be noted that spool 41c of tie material is mounted on a shaft and the ribbon 15 is fed from spool 14c, routed armd rollers 41b, 41a and 41, around needle roller 44 and the end of the ribbon 15 is gripped in the holder-shear assembly 60, as best illustrated in Figure 1 of the drawing. Spool 41c is mounted on a shaft engaged by a brake (not shown). As needle 42 forms a loop of tie material around the gathered neck of a bag, the force of inertia and force exerted by the brake cause the spool 41c to remain stationary momentarily as a crank arm, on which roller 41a is mounted, is rotated.

As will be hereinafter more fully explained, one of the pulleys 41,41 a or 41b is preferably equipped with a sensor device which is capable of calculating the amount of ribbon 15 dispensed from spool 41c. The sensor apparatus determines whether or not a bag neck is present. As needle

41 moves from the full outline position illustrated in Figure 2 to the dashed outline position, if a bag neck is not positioned in the path of the ribbon, the cycle of operation will be interrupted so that the holder-shear assembly 60 will not be actuated and the twister hook assembly 50 will not rotate. This prevents actuation of the holder-shear assembly which would have resulted in the ribbon being dropped or released if a bag neck was not present.

The frame of the bag tying device may assume many configurations. In the illustrated embodiment upper and lower face plates 16 and 17 are supported on forward edges of vertically extending end plates 18 and 19 having slots formed therein to permit passage of a bag neck. A horizontal mounting plate 19a extends between lower portions of end plates 18 and 19 and a vertical mounting plate 16a extends outwardly from end plate 18.

A motor M 1, having an encoder E1 mounted the rear end of motor M 1, is mounted on an upper portion of the vertical mounting plate 16a for driving the gathering assembly 20. A motor M2, having an encoder E2 mounted the rear end and a gear box 46 mounted on the front end of motor M2, is mounted on an upper portion of the rear surface of face plate 16 for driving the needle assembly 40. A motor M3, having an encoder E3 mounted the rear end of motor M3, is mounted vertically on horizontally extending mounting plate 19a for driving the twister hook assembly 50.

A motor M4, having an encoder E4 mounted the rear end of motor M4, is mounted on a lower portion of end plate 18, and in the illustrated embodiment extends below motor M2, for driving the holder-shear assembly 60.

Referring to Figures 1-5 of the drawing, bag neck gathering apparatus 20 comprises, in a preferred embodiment of the invention, an upper gathering belt 22 routed around a driven pulley 24 and idler pulleys 26,27 and 28. The bag neck gathering mechanism 20 further comprises a lower gathering belt 32 routed around a driven pulley 34 and idler pulleys 36,37 and 38. As best illustrated in Figure 1 of the drawing, the portion 29 of the upper gathering belt 22, extending between idler pulleys 27 and 28, is substantially parallel and closely spaced relative to the portion <BR> <BR> <BR> <BR> 39 ofths lower gathering belt 32 which extends between driven pulley 34 and idler pulley 36. In the illustrated embodiment, gathering belts 22 and 32 move a bag neck along path 12 in a plane P as illustrated in Figure 2. A pressure pad 21, resiliently urged upwardly by springs 21a and 21b acting through bell cranks, maintains belts 22 and 32 in fricdonal engagement with the neck of a bag or other material to be tied.

As best illustrated in Figures 3 and 5 of the drawing, driven shaft 25, having driven pulley 24 mounted on one end, has a pulley 23 mounted on its opposite end Driven shaft 35, having driven pulley 34 mounted on one end, has a pulley 33 mounted on its opposite end. A pulley 30

mounted on the drive shaft of motor MI drives pulleys 23 and 33 through a belt 31 such that driven pulley 24 rotates in a clockwise direction while driven pulley 34 rotates in a conter- clockwise direction, as viewed in Figure 2 of the drawing. Belt guards 16a and 16b and 17a preferably extend between the gathering belts and products on the conveyor. The bag neck is moved into a slot in the belt guard by brushes (not shown) and the product in the bag engages the belt guards when the neck of the bag is drawn by gathering belts 22 and 32 around a bag stop lever 80. It should be appreciated that other and further gathering structures may be used to form a gathered neck on a bag.

Terms such as"left,""right,""clockwise,""counter-clockwise,""horizontal ,""vertical," "up,"and"down"when used in reference to the drawings, generally refer to orientation of the parts in the illustrated embodiment and not necessarily during use. These-temis used herein are meant only to refer to relative positions and/or orientations, for convenience, and are not to be understood to be in any manner otherwise limiting.

As illustrated in Figure 7 of the drawing, motor M1 is driven by a solid state DC motor controller 91 which is capable of varying the speed of motor M1 to substantially synchronize movement of upper gathering belt 22 and lowering gathering belt 33 with the speed of a conveyor 300 moving packages 125 adjacent the bag gathering mechanism 20. For example, if the tier 10 is to gather and de the necks of 100 bags per minute, the conveyer 300 would preferably bring bags to and through the tier at a speed of approximately 300 feet per minute and the gathering belts 22 and 32 would preferably be driven at a speed of, for example 305 feet per minute, so that the neck of the bag would be accelerated for gathering the neck, stopped momentarily while it is being tied with a ribbon and then discharged in a substantially continuous operation.

As will hereinafter be more fully explained, the gathering assembly 20 also includes a bag stop lever 80, illustrated in Figures 2 and 3, mounted on shaft 85 for rotary movement about a horizontal axis, in the illustrated embodiment. Shaft 85 extends through an electric brake 82, which momentarily locks lever 80 in a lowered position extending across path 12 such that gathering belts 22 and 32 move the bag neck into engagement with lever 80. After the bag neck has been gathered and tied, the electric brake 82 is released and the gathered neck, carried between belts 22 and 32, urges the lever 80 upwardly such that it does not obstruct movement of the gathered neck After the gathered neck passes lever 80, the lever 80 moves back to the illustrated position extending across path 12.

A needle assembly 40, best illustrated in Figures 1-4 and 7, is positioned for wrapping a strand 15 of ribbon material around a gathered neck of a bag. The needle assembly 40 comprises

a needle 42 carrying idler rollers 44,44a and 44b. The needle 42 is mounted on the output shaft 45 of a gear box 46 driven by motor M2. Needle 42 is shown in its home position in Figures 1 and 2 of the drawing. Motor M2 moves needle 42 from the full outline position to the dashed outline position, illustrated in Figure 2 of the drawing, and then reverses for moving the needle 42 back to the position illustrated in full outline in Figure 2.

Referring to Figures 1,3 and 7 of the drawing, a twister hook assembly 50 comprises a twister shaft 52 rotatably mounted in a bearing 53 having a hook 54 on one end thereof and a pulley 55 on the other end. A drive pulley 56 is mounted on the drive shaft of motor M3 and drives pulley 55 through a belt 58.

A ribbon guide plate 58 is mounted on the upper end of a support plate 57 secured to bearing block 53 and extending generally parallel to shaft 52. The ribbon guide plate 58 has an opening which encircles shaft 52 to provide an upper surface extending generally transversely of twister hook 54. Tails of ribbon 15 extend upwardly from holder shear assembly 66 and are engaged by hook 54 when shaft 52 is rotated.

The tails of the severed section of ribbon are drawn across guide surface 58 and deflected relative to twister hook 54 at an angle of approximately 90 °. This reduces the tendency of the tails of the severed ribbon to slip relative to the twister hook.

As best illustrated in Figure 9 of the drawing, the loop portion of ribbon 15 extends above hook 54 mounted on shaft 52. Ribbon guide plate 58, mounted immediately below twister hook 54 pulls the tails 15a and 15b across the upper surface of ribbon guide 58 which forms a"kink" where hook 54 engages tails 15a and 15b to at least partially wrap the ribbon around the surface of hook 54 and pull it into a groove between hook portion 54 and shaft 52. Rotation of shaft 52 and hook 54 causes the ribbon material above hook 54 to be twisted.

As best illustrated in Figure 10 of the drawing, ribbon guide plate 58 is positioned between twister hook 54 and the holder shear assembly 60.

As best illustrated in Figures 1,2,5 and 7 of the drawing, a ribbon holder-shear assembly, generally designated by the numeral 60, comprises a holder and shear assembly of the type disclosed in U. S. Design Patent No. 307,281 to Charles E. Burford and U. S. Patent No.

4,856,258 entitled WIRE TYING DEVICE, which issued August 15,1989, to Charles E. Burford and Jimmy R Frazier. The holder-shear assembly 60 comprises a gripper arm 62 having a gripper finger 64 on one end thereof rotatably secured to a mounting plate 66 by bolt 65. A pair of anvils 68 and 69 are formed on the end of mounting plate 66, each being associated with shear surfaces 68a and 69a to grip and cut a strand of ribbon as will be hereinafter more fully explained.

Referring to Figures 11 and 12, as the gripper finger 64 is rotated it pushes the ribbon into the comer 69d between the inclined surfaces 69c and 69e which form a holding area. Because the ribbon is under tension, this"V"point extrudes the ribbon and grabs to pre-hold the ribbon. As the gripper finger rotates further, the ribbon is molded around point 69b and bent over the cutting edge 69a of anvil 69.

The gripper finger has ribs 64a and 64b having surfaces that are angularly disposed at the same angle as surfaces 69c and 69d on anvil 69. However, the edge of the rib 64a and the inner section 69d between surfaces 69c and 69e are not parallel. As illustrated in Figure 13, the surface of the rib forms a tapered slot 67 of diverging cross-section to make a pinch angle. As the ribbon 15 is pulled out of the cutting area, this causes the ribbon to be pinched tighter as tension increases.

It should be readily apparent that as needle 40 moves from the full outline position illustrated in Figure 2 to the dashed outline position the tension in ribbon 15 increases as the ribbon is wrapped around the gathered neck of the bag.

Gripper finger 62 is oscillated between anvils 68 and 69 by a shuttle rod 75 having a cylindrical end 75a with a resilient bushing 75b through which a bolt 75c extends. The device operates effectively with wire or wireless ribbon 15 and also different gauges of wire or wireless ribbon because resilient bushing 75b is compressed and deforms to accommodate different size ribbon in slot 67.

Profile of cam 75 is shaped to permit rotation of the cam through an angle of a few degrees when the cam and shuttle bar are in home positions without changing the cam follower position.

This is done so that the cam may be rotated quickly and if the motor over-shoots the home position it can back the cams to the desired home position.

Because wire and wireless ribbon are not all of the same profile and vary in thickness, compression of the resilient bushing 75b can accommodate different dimensions. As the ribbon 15 is trapped in the holding area in slot 67, the resilient bushing 75b flexes and holds constant pressure on ribbon 15. This allows a change of ribbon types or ribbon thickness without requiring adjustment of cam 70 and cam followers 71 and 73.

Referring to Figures 5 and 7 of the drawing, a cam 70 is mounted on the shaft of motor M4 and is configured to engage cam-followers 72 and 74 on spaced arms 71 and 73 secured to a shuttle rod 75 mounted for reciprocating movement in bearings 76. A link 75a secures the end of gripper arm 62 to shuttle rod 75.

It should be readily apparent when the shaft of motor M4 rotates one-half revolution, cam 70 will exert force through cam-followers 72 and 74 for moving shuttle rod 75 for pivoting the

actuating arm 62 about bolt 65. The free end of the ribbon is gripped between the end of gripper finger 64 and anvil 68 or 69, depending on which direction the gripper finger 64 is shifted. As will be hereinafter more fully explained, when needle 42 wraps the intermediate section of the ribbon 15 around the gathered neck of a bag, the ribbon will be positioned between gripper finger 64 and the other anvil 68 or 69. When gripper finger 64 is shifted to its opposite position, the ribbon will be cut and the free end of the strand of ribbon will be gripped between gripper finger 64 and anvil 68 or 69.

Referring to Figure 2 of the drawing, roller 41 has a plurality of index points 4 six. In the illustrated embodiment, the index points are formed by steel dowel pins circumferendally spaced around the axis about which roller 41 rotates.

A proximity switch, not shown, is positioned near index pointers 41x for making an electrical circuit when the presence of an indexing pin 41x is sensed. The proximity switch is of conventional design and is connected through a suitable power supply and amplifier to the CPU 96.

Thus, the CPU monitors the proximity output and counts the pulses produced by index pins 41x in roller 41. The CPU 96 calculates the amount of ribbon dispensed to determine whether or not a bag neck is present as needle 42 moves from the full outline position illustrated in Figure 2 of the drawing toward the dashed outline position illustrated in Figure 2 of the drawing. If needle 42 did not wrap ribbon around a bag neck, the CPU will terminate a portion of the remainder of the cycle of operation so that holder-shear 65 will not be actuated to prevent releasing the end of ribbon 15 which is gripped between gripper finger 64 and anvil 68 or 69.

Referring to Figures 1,2 and 3 of the drawing, a bag stop lever 80 is mounted on a shaft 85 for rotary movement about a horizontal axis. Shaft 85 extends through an electric brake 82 and has a crank arm 85a secured thereto which is resiliently urged in a clockwise direction, as viewed in Figure 3, by a spring 83.

A switch 86 is actuated by switch arm 88, which actuates a timer for cnergizing electric brake 82 which momentarily locks bag stop 80 in a fixed position for a predetermined period of time, for example 0.25 seconds for restraining the leading edge of a bag neck, such that gathering belts 22 and 32 will gather the neck adjacent bag stop 80. At the expiration of the predetermined period of time, electric brake 82 will be de-energized so that linear movement of the bag neck will rotate bag stop 80 upwardly to release the bag so that it will be moved away by the conveyor. Bag stop 80 is biased toward the position illustrated in Figure 3 of the drawing by a spring 83. It

should be readily apparent that the spring 83 may be replace by a counter-weight, air cylinder or other suitable biasing mechanism to resiliently urge bag stop 80 toward its home position.

Motors M1, M2, M3 and M4 are bi-directional, permanent magnet, DC brush-type servomotors having outputs proportional to the voltage applied across the armatures. Such motors are commercially available from Groschopp, Inc. of Sioux Center, Iowa as a"Power Master 8304" 24 volt DC continuous power motor. At 1500 rpm the motor generates 16 oz-in torque and has an output of. 090 horsepower at 4.2 amps. At 2450 rpm the torque is 47 oz-in and the output is . 113 horsepower at 5 amps. At 5400 rpm the torque is 37 oz-in and the output is. 197 horsepower at 8.2 amps.

It is noted that other motors and motors of other sizes may be provided to facilitate driving the various assemblies. For example, it is contemplated that smaller motors would be used in a counter top model used for gathering and fastening materials such as coils of electrical cord, water hose, tubing, or yarn, and bundles of cable, rods, or carrots and other produce.

One side of the armature winding of each motor M1, M2, M3 and M4 is connected to ground such that reversing the polarity of current through the armature winding reverses the direction of rotation of the motor.

Each of the motors M 1, M2, M3 and M4 has an encoder E 1, E2, E3 or E4 mounted on its drive shaft which delivers an electrical signal to a decoder D1, D2, D3 or D4 which is representative of the position of the motor shaft.

Referring to Figure 7 of the drawing, the numeral 90 generally designates a power supply for delivering electric current to motor controller 91 and to motor M1 in the bag neck gathering mechanism 20; motor controller 92 and motor M2 in the needle assembly 40; motor controller 93 and motor M3 in the twister assembly 50; and motor controller 94 and motor M4 in the holder- shear assembly 60.

The system is controlled by a computer 95, diagrammatically illustrated in Figure 7, which receives and stores a set of instructions and then acts upon the instructions in a predetermined and predictable fashion. A microprocessor 96 is attache to a printed circuit board into which a thin layer of metal has been applied and then etched away to form traces. The electronic components of the central processing unit are attache to the board with solder so that they can change electronic signals through the etched traces on the board.

A suitable 32-bit integrated microcontroller 96 is the MC68332 which is commercially available from Motorola, Inc. of Schaumburg, Illinois as a product referred to as"MC68332 SIM" System Integrated Module.

The MC68332 microcontroller 96 contains intelligent peripheral modules such as the time processor unit (TPU) which provides 16 microcoded channels for performing time-related activities for simple input capture or output capture to complicated motor control or pulse width modulation.

High-speed serial communications are provided by the queued serial module (QSM) with synchronous and asynchronous protocols available. Two kilobytes of fully static standby RAM allow fast two-cycle access for system and data stacks and variable storage with provision for battery backup. Twelve chip selects enhance system integration for fast external memory or peripheral access. These modules are connected on-chip via an intermodule bus (IS3).

The CPU board is connected to an auxiliary board 98 through a connector header which carries data signals and address signals. Driver circuits C1-C4, which generate pulse width modulated (PWM) signals, are mounted on the auxiliary board along with the decoders D1-D4.

The pulse width modulated signals from driver circuits C 1-C4 are sent to the motor drivers 91-94 selectively delivering positive or negative DC power to control the operation of motors M1-M4.

The circuits carrying input signals from the encoders E1-E4 to decoders D 1-D4; the circuit carrying pulse width modulated signals from driver circuits C1-C4 to motor drivers 91-94; and the cicuits carrying power from the motor drivers 91-94 to motors M1-M4 form a closed loop control system. The closed loop control system depends upon the feedback concept for operation and the output PWM signals are forced to a pre-assigned function of the reference input of the microcontroller of the central processing unit. The microcontroller 96 sends control PWM signals determined by the programme movements stored in RAM memory in a pre-assigned order as a function of time after switch arm 88 returns to its home position illustrated in Figure 3. The control PWM signals are delivered to the control circuit. Each encoder E1-E4, connected to the shaft of motors M1-M4, send quadrature signals to the decoders D1-D4 that indicate the position of the shaft of each motor. The control PWM signals delivered to each control circuit C 1-C4 are delivered to motor drivers 91-94. The quadrature signals from decoders D1-D4 are read to adjust the control PWM signals.

Drivers 92,93 and 94, which control the delivery of power to motors M2, M3 and M4, respectively, for controlling the needle assembly 40, twister hook assembly 50 and holder-shear mechanism 60 are substantially identical. One side of the winding of each of the motors M2, M3 and M4 is connected to ground Drivers 92,93 and 94 deliver either positive or negative power to the other side of the motor winding for driving motors M2, M3 and M4 in opposite directions.

For example, when positive 34 volt direct current is delivered to the winding of motor M2, its shaft

is driven in a clockwise direction. If negative 34 volt direct current is delivered to the winding of motor M2, its shaft will be driven in a counter-clockwise direction.

The driver 91 for motor M1 connected to the bag gathering assembly 20, is similar to drivers 92,93 and 94 cxccpt that driver 91 is not provided with the capability of delivering negative direct current because it is not necessary for motor M1 to be driven in reverse.

Software is stored in FEEPROM memory on the CPU board for controlling the acceleration, speed and position of the shaft of each motor M1-M4. Figure 11 is a graphic representation of the sequence of operation of the needle, hook and shear assemblies during a complete cycle of operation. The microcontroller 96 is initially programme by a computer through a serial port RS for storing a program which will initiate movement of needle 42 from its home position illustrated in Figure 3 and the speed of movement toward the dashed outline position illustrated in Figure 3 controlled by signals delivered through control circuit C2 to motor M2.

While needle 42 is moving from the position illustrated in full outline toward the position illustrated in dashed outline, the program causes a signal to be sent from control circuit C3 to motor M3 to begin rotating twister hook 54 and continue rotation of twister 54 a predetermined number of revolutions controlled by the motion profile in RAM memory. Similarly, when needle 42 and twister hook 54 are in predetermined positions, a signal will be sent from driver circuit C4 which will energize motor M4 for rotating cam 70 to move the gripper finger 64 to release the free end of the ribbon and shear a segment from the end of the strand of ribbon. At a time controlled by the software, a signal will be delivered to motor M2 for moving needle 42 from the position shown in dashed outline in Figure 3 back to its home position. A signal will be delivered to motor M3 for rotating twister hook 54 two revolutions in the reverse direction for slinging the tie, which has been twisted around the neck of a bag, out of the twister hook 54 for completing a tying cycle.

It should be readily apparent that when the neck of a bag moves between gathering belts 22 and 32, switch arm 88 will be moved downwardly from the position illustrated in Figure 3 which will energize electric brake 82 so that belts 22 and 32 will move the neck of the bag into engagement with bag stop 80 causing the neck to be gathered. As the trailing edge of the neck of the bag passes over the end of switch arm 88, switch arm 88 will move back to the position illustrated in Figure 3 causing switch 86 to send a signal to the microcontroller for starting a new tying cycle.

It is to be understood that while detailed descriptions of a preferred embodiment has been illustrated and described, the invention is not to be limited to the specific arrangement of parts and specific feu= herein described and illustrated in the drawing. Rather, the descriptions are merely of an exemplary embodiment of the invention, which may be embodied in various forms.