CA1097204A - Strapping machine and method - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A strapping machine and method for applying flexible, heat sealable straps around objects in which the supply coil of strap and the feed rollers for a strap accummulating compartment are driven by a common rotatable drive for synchronous feeding. A strap feeding unit for feeding flexible strap in which a feed and pinch roller extend through opposed slots which intersect a strap carrying groove which totally, confines the strap. A strap tensioning mechanism in which rough tensioning and final tensioning are achieved by the movement of a single mechanical plate. A cutting and sealing head in which feeding of a new strap around the object can occur simultaneously with the sealing of the previous strap. A track opening mechanism which is operated by components of the sealing and cutting head.

Description

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BACKGF~O~IND CIF T~IE INVENTION
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This invention pertains to methods and apparatus for wrapping objects with flexible, fusible strap.

The principal object of the invention is to provide a high speed strapping machine capable of strapping ao straps a minute as compared to typical known strapping rates of 3~ straps a minute. This is accomplished through simple mechanical movements, each combining several functions.
It is another object of this invention to provide an improved Flexible strap supply and accummulating device. Basically, this object is obtained by driving the reel or coil of strap for discharginy strap synchronously with feed rolls for feeding the discharged strap into an accummulating compartment.
Another object of this invention is to provide an improved strap feeding unit for feeding flexible strap in a strapping machine. Basically, this object is obtained by confining the strap in an elongated transverse slot and bringing the powered and pinch rollers together through opposed grooves at right angles to the slot for driving the strap through the slot~
It is another object of this invention to provide an improved strap tensioning mechanism. Basically, this object is obtained by providing first ~ i means for pulling the strap around the object with a first tension, providing ~;
second means for drawing the strap tightly around the object at a second, greater tension, and actuating both of these means by a simple mechanical movement of a common plate. In the preferred embodiment the strap is anchored from the supply end until the first predetermined tension is reached, and then the anchor is overcome by the tension in the strap to provide removal of additional strap f rom the accummu l ator .
Still another object of the invention is to provide a cutting and sealing head for a strapping apparatus in which a first strap can be sealed while a second strap is simultaneously being positioned arouncl the object in the same plane. Basically, this object is obtained by providing strap carrying slots in a platen and grippers which are acting on the first strap so that the strap can pass in a parallel path in the same plane into the track.
Still another object of this invention is to provide an improved track ~ g7~4 opening device For a strapping apparatus. PreFerably this object is obta7necl by using a rigid track and coupling the tracl~ at one location directly to move-ments of the members in the cutting and sealing heads so that a simple, single operation accomplishes opening oF the track.
A principal object is to provide a machine For wrapping straps around objects, comprising: a strapping compartment; a track encircling the compartment; a cutting and sealing unit positioned along said track for cutting and joining the cut ends of the strap together, the improvement comprising:
said track having an open rigid strap guide mernber Formins a partial loop 10 having an upper portion, a lower portion and opposed end portions, a closure member having upper, lower and end portions confronting said corresponding portion of the open strap guide for closing the opening to form a closed path for guiding movement of the strap around an object in the cornpartment, and means for engaging only one oF said track guide or closure member portions for moving the entire closure member or track guide as a unit away from its confronting closure member or guide to release the strap from the guide.
BR!EF DESCRIPTI~N OF THE DRA INGS
Figure l is a front elevatlon of a strapping machine embodying the principles of the invention;
Figure 2 is an isometric of a preferred strap supply and accumulator;
Figure 3 is a fragmentary enlarged side elevation oF a strap tension-ing mechanism;
Figure 4 is a fragmentary plan oF the tensioning mechanism shown in Figure 3;
Figure 5 is a side elevation of a strap feeding unit;
Figure 6 is an end elevation of the strap feeding unit shown in Figure 5;
Figure 7 is a Fragmentary detail of the strap feeding unit shown ;~
in Figure 6;
Figure a iS an enlarged Fragmentary front elevation of a cutting and sealing head;

Figure 9 is an end elevation of the sealing and cutting head and illustrating a common cam shaft control For operating the elements of the cutting and sealing head;

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Figure 10 is a plan of the sealing and cutting head with elements removed for clarity;
Figure 11 is an enlarged detail of the sealing and cuttlng head taken in a plane parallel to the direction oF strap movement;
Figure 12 is a section of the track taken along line 17.-12 of Figure 1;
Figure 13 is a section oF the track taken along line 13-13 of Figure 1;
Figure 14 is a section of the track taken along line 1~ of Figure l;
Figure 15 is a fragmentary perspective of part of the cutting and sealing head;
Figure 16 is a schematic cam timing sequence; and Figure 17 is a schematic isometric of a modified form of strap supply.
D E TAI LE
As best shown in Fi~3ure 1 the strapping machine includes a strap track 10, a cutting and sealing head 12, a strap feed mechanism 14~ a strap supply 16, a strap accumulator 18, a strap tensioning unit 20 and a cam control device 22. Basically, strap is fed through the strap Feed mechanism 14 From the accumulator 18 through the tensioning unit 20. The strap feeds throush the ~ ~
cutting and sealing head 12 around the track 10 and the free end of the strap ~ ~ ;
hits an obstruction in the cutting and sealing head to stop its travel. Strap 20 then builds up in the strap feed mechanism signalling to the cam control drive 22 io begin a cycie of sealing, cutting and tension7ng. During this cycle the free end of the strap is held while the strap is first roughly tensioned b~y ~he tensioning unit 20 to pull the strap out of the track snugly around the object belng wrapped. Secondly7 the strap is then tightly tensioned around the~object and the continuous end oF the strap is clamped in the tensioned condition. Next the continuous end which underlies the free end, and the free end are pressed against a heating bar until the strap is melted and then the strap is pressed tightly together with the continuous end severed. After cooling the cutting and sealing head opens so that the strap can be removed with the object and a new 30 cycle of feeding the strap around the track is begun. The machine and the method of strapping objects offer advantages over known prior art machines and methods which advantages will be discussed in more detail during the description of each c>f the sub-assemblies of the machine. ~ ~;
- STRA~ SUPP~LY AN ACCUMULATOR
The strap supply is best shown in Figures 1 and 2 and includes a coil ,~ .. . . .

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24 containing strap S. The coil rests on a pair of shafts 25 and 26. 5haft 26is provided with a rubber friction cover beneath the coil and is provlded with a larger diameter roller 26a at its end. ShaFt 26 thus serves as a powered Feed roll to pull the strap from the coil via guide rollers 2~a and 24b and push it into the accumulator 1~. ShaFt 26 is driven by a belt and pulley drive 27. A pinch roller 28 is spring-mounted to press against the powered roller 26a.
The accumulator 18 includes a back plate 30 and a closely spaced clear plastic front plate 31 which forms a housing for the strap. The strap is pushed upwardly into the housing in accordion Folds as best shown in Figure 1.
10 A paddle 32 is pivotally mounted and protrudes down into the top oF the housing.
The paddle has a low switch operator surface 321 and a full switch operator surface 32f. As the accordion folds build up in the housing the paddle is raised until surface 32f closes a full switch FS to stop the feed. ~s strap leaves the accumulator the level of the folds drops deactivating the fulI switch and when the level drops sufficiently so that surfac 321 energizes low switch LS the feed roller 26a is again put into motion to increase the supply of strap within the accumulator. An empty switch ES will stop the machine iF strap no longer is available due to an empty coil 24.
In known plastic strap supplies and accumulators the feed rolls for 20 the accumulator pull the strap From the coil by pulling directly on the strap. A
brake is then used to stop the freely rotating coil. Using this technique the payoff speed is limited because the snap in the strap accelerates the coil and the coast of the coil reel at the end of feeding makes the braking action very critical.
In the instant application the feed rolls for driving the coil and Feeding the strap are advantageously very simple and require no separate brake for the coil.
The drive on the powered shaft 26 operates through a clutch which brings the coil up to speed slowly and the coast at the end of Feeding is not a concern since it merely adds a slight amount of additional strap to the accumulator. Using this unique technique the strapping machine is able to be run at higher speeds 30 than in the known strapping machines. A ~urther advantage is that with known strap supplies a separate reel is needed to hold the coil whereas in the supply and accumulator of this invention the coil is merely set directly on the supporting shafts 25 and 26. Still further, the strap leaves the coil at a constant linear _i speed regardless of changes in diameter of the roll.

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~ s best shown in Figure 17 a modified strap supply is shown. In this embodiment a reel 30V oF strap 5 is rotatably mounted on an axle 30~
which is lifted up into support brackets 303. A belt 304 is pushed by sprlng 306 against the sur~ace of the strap on the reel holding the reel into the brackets.
The belt is driven by the shaft 26 which is coupled to feed roller 26a. Thus the belt and feed roller are rotated synchronously and the linear speed of the strap leaving the reel and passing throwgh the Feed pinch rollers in the same, or as in the embodiment of Figure 2, slightly greater at the pinch rollers, regardless of diameter changes in the strap on the reel.
STRAP FEED M~CHANISM
The strap feed mechanism 14 is best shown in Figures 1 and 8. The feed mechanism includes a continuousty rotating powered roller 34 which rotates in a counterclockwise direction. A spring biased pinch roller 35 actuated by solenoid 192 presses the strap against the powered roller. The rollers 34 and 35 push the strap along a guide channel 36. As best shown in Figure 7 the guide ;
channel is provided with a siot 36a and the peripheral surfaces oF the rolls 34 and 35 are of reduced thickness which is less than the width of the slot 36a. ~ ~;
The strap is thus contained at all times and is supported against buckling as it ~ ;
is driven by the rollers through the channel 36. This is an advantageous feature 20 as buckling of the strap has been a problem with known strap-feeding mechanisms.
Known strap-feeding mechanisms generally interrupt the strap guide or channel by breaking the channel upstream and downstream of the feed rollers. This necessitates chamfering the inlet to the downstream end of the track as the strap is fed from the Feed rollers. It is in this area of the chamfer, however, where resistance to the movement of the strap causes the tendency to buckle. As is readily apparent in the instant invention of this application there is no chamfer nor interription of the channel so that the buckling does not occur.
The strap feed mechanism 14 also includes a compartment 38 having a paddle 39 that forms a portion of the channel 36 as it passes over the compart-30 ment. The paddle is pivotally mounted and held by a light spring 40 in the raised position. The paddle is provicled with a cam 41 that engages a stop switch S. ~ ;~
~s strap is Fed by the rollers 34 and 35 through the channel 36 the free end of the strap passes through the cutting and sealing head 12 around the track 10 and comes to rest again in the c utting and sealing head. When ~he free end of .
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the strap is blocked the continuous end in the channel 36 begins to back up pushing the paddle 39 downwardly and activating the stop swîtch S. Th7s de-energizes the solenoicl 192 and allows a spring to move the pinch roller 35 away from the powered roller 3~ to discontinue Feeding of the strap and energizes a trigger solenoid ~3 ~Fi~ure 1) which pulls a trigger 4~ away From a single revolution clutch ~5:which is the basic drive component for the cam control drive 2~ to begin the rest of the cycling of the machine.
TENS!ONING UNIT
The tensioning unit 20 is best shown in Figures 1, 3 and ~ and 1~ includes a plurality oF freely rotating stationary take-up rolls 48 alternated with Freely rotating movable take-up rolls~49. The strap Feeds up and down the rolls 48 and ~9 as shown in Figure 3 and when the movable rolls ~9 are shifted to the phantom line position in Figure 3 it can be seen that a considerable amount of strap can be pulled back from the track 10 at the downstream end of the strap. The take-up rolls provide a rough or large retraction of the strap to pull it out of the track 10 and snugly around the object being wrapped. At this time, of course, the free end of the strap is clamped at the cutting and sealing head so that only the continuous end is retracted by the take-up rolls.
The strap between the take-up rolls and the accummulator passes over a pair of flanged rollers 50 in between which is fastened an anvil 510 The anvil has a smooth end surface 51a. A pair of spaed anchor arms 52 are pivoted on a plate 53 by pivot post 5~. Pivotally mounted between the anchor arms is an anchor block 56 having a protruding wedge 56a. The anchor block has a surface 56b that rides against a pin 57. A spring 58 connects to the anchor arms at a point ~8a and pulls the arms toward the anvil to pull the wedge 56a against the strap and press it against the smooth end surface 51a of the anvil. The strap is thus trapped and unable to move from the accummulator during rough tension-ing. ~s the strap is drawn tight on the package, however, the tension increases so that the anchor block begins to rotate relative to the anchor arms and over comes the force of the spring 58a. When the tension reaches a preset desired amount the anchor block swings over-center relative to the spring away from the strap and anvil. This frees the s~rap for movement From the accummulator as the rollers ~9 continue to move toward the right. The anchor arms are fixed to a lever 59 that is engaged by a shoulder 60 that forms part of a T-shaped 9~2V~ ~
frame 61. The T-shaped -Frame is attached to a movable front plate 62 which carries the movable rollers 49 and reciprocates From left to right as shown in Figures 1 and 3. When the front plate 62 is to the left the lever 59 is rocked counterclockwise so that the anchor block is freed from the tape. As the front plate moves to the right however the spring 58 pulis the anchor arms 52 toward the anvil to bring the anchor block into engagement wlth the strap.
The front plate 62 slides on ways 6'~ and is pulled to the left by a spring 65 (Figure l)c The upper end of the plate is supported by a roller 63 running in a slot in a fixed bar 63a. The front plate is coupled to a tension 10 arm 70 that is coupled to a bell crank 71. The free end of the bell crank is provided with a cam follower 72 that follows a cam 73 which is fixed to a cam shaft 76 that is coupled to the single revolution clutch 45. Thus the tension arm begins to swing the front plate 62 to the right when the single revolution clutch is energized after the free end of the strap has completely encircled the object and has come to rest within the cutting and sealing head.
Spaced just above the front plate 62 is a knurled tension roller 80 that is coupled to a slip clutch 82 (Figure 4) such that the roller 80 is free in ~;
the counterclockwise direction as shown in Figure l~but will engage the clutch -~
8~ when rotated clockwise and provide a drag to a predetermined desired amount. ;-20 The strap is pinched against the tension roller 80 by an eccentrically mounted pinch roller 84. The pinch roller is connected to a tension lever 86 having a cam follower roller 87. The lever is pulied down by a spring 88. As the front plate 62 moves to the right during a tensioning cycle the cam roller 87 riding on the top o-F the plate keeps the pinch roller 8~ away from the flanged tension roller 80 so that the strap can be freely drawn back by the rollers 49.
The top surface of the plate 62 has a downward ramp 92 and an upward ramp 94. ~;~
When the front plate moves to the right a distance suFFlcient to alloW the roller 87 to move past the downward ramp 92 the tension lever 86 swings counterclock-wise to engage the pinch roller 84 against the tension roller 80. The strap is 30 also pushed to the right (Figure 3) by a roller which ro~ates on the movable frame 61 until the tension reaches the desired load on the slip clutch 82 and aliows the strap to rotate the roller 80. Continued movement of the front plate 62 to the right draws the roller up the up ramp 94 allowing the clog 89 to seat beneath the notch at the end of the tension lever to hold the tension lever up and . . . ~ ,, ~

in an inactive position away from ramp 92 as the Front plate is returned. When the front plate is returned to the le-Ft a pin 96 engages the dog 89 to release the tension levers so that the roller 87 returns to the top surFace oF the front plate 62. An adiustment bar 67 is connected to plate 62 by screws and can be moved to the le~t to overlap ramp 92 with a second ramp 92a thus changing the startingtime of the final tensioning.
Known strapping machines usually employ two tensioning devices.
The first draws the strap around the package more or less loosely. The second comes into actioni and draws the strap up to its final tension. In the instant 10 application the invention perForms both of these operations by a single mechanism requiring only a single timing sequence. This advantageously results in simplicity of manufacture and operation and greater strapping and tensioning speeds.
CUTTING AND SEALIN~; HEAD
As best shown in Figures 1 and 8-14 the cutting and sealing head 12 is provided approximately centrally in the lower run of track 10 and forms a part thereof. The track includes a rectangular plastic straip 100 having a groove 1û2 for receiving the strap. The track is abutted against a oover 104 by springs 105. The track is mounted on a pad 106 which slides on posts 107.
20 Stripper pins 108 pass through the track and pass into the groove 102 as the track and pads are moved away from the cover. Thus the stripper pins eject the strap From the track groove to prevent binding. The track pads are con- ~ -nected to track bars 110 which are engaged by paddles 182 and 18~ to be described to open the track during the desired timing sequence of the strapping ;~
cyc I e.
The sections of $rack immediately adjacent the cutting and sealing head 12 are best shown in Figures 12-14. Figure 12 which is taken along the line 12-12 of Figure 1 shows the groove 102. Figure 12 also shows groove 36a below the groove 102. This second groove is to allow the continuous strap ~o 30 move in beneath the captured free end oF the strap and for beginning the threading of a new strap during the sealing cycle. Figure 13 illustrates only the groove 102 since at this location along the track there is only a single groove as the free end of the strap is stopped in the cutting and sealing head.
The cutting and sealing head 12 is provided with a cover plate 116 21~ ~

that is movable transversely of the direction of strap movement. For clarity movements described as being transverse hereinafter will means transverse to the path of the strap. Also in Figure 10 which is a plan view oF the cutting and sealing head it should be understoocl that the cover plate 116 has been removed for clarity. The cover plate Forms an anvil for grippin~ and sealing the strap as will be descr7bed. The cover plate 116 is reciprocated by a ~ -cam Follower 118 which rides on a cover plate cam 119. A left hand gripper 120 pivotally mounted in a left hand yoke 120a which is pivotally mounted For vertical movement hétween an upper position as shown in Figure 11 where it 10 can clamp the continuous end of the strap to the cover plate. The left hand gripper is movable into a lower position as shown in phantom lines in which the free end of the strap engages a stop surface 121 to stop the strap as it makes a loop around the tracK 10. The leFt hand gripper is provided with a track groove 122 which allows feeding of new strap while the gripper 120 is raised holding the previous loop of strap. The left hand gripper is free to move downwardly and is held in its raised position by a cam follower 124 that rides on a left hand cam 125. A spring 123 buffers the force between the gripper . ~,; .
and the gripper yoke.
A right hand gripper 128 is vertically reciprocally mounted and is 20 moved down by a cam follower 130 that rides on a right hand gripper cam 131.
The cam follower 130 pulls the right hand gripper down against the force of a set of Belleville springs 13~. These springs when allowed to push the right hand gripper up press the gripper teeth of the right hand gripper against the `~
strap to anchor the free end of the strap against the cover plate 116. The ;
right hand gripper is provided with a track groove 136 which provides a lower path for the strap as the Free end of the strap passes between the cover plate and the upper surface of the r7ght hand gripper on its way to the stop surface 121 on the left hand gripper.
A platen 139 is pivotally mounted on a platen yoke 138a. The platen 30 yoke is pivotally mounted for movement between the left hand and right hand grippers and between an upper position as shown in solid lines in Figure 11 in which it presses the lower continuous end of the strap agaînst the upper Free end of the strap and against the stop plate 116 to squeeze the straps together after melting. The platen is provided with a lower gro~ve 14Q for ~g_ :

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allowing the continuous end of the strap to be moved beneath the sealed loop of strap for starting a new feeding cycle. A cam follower 1~2 follows a platen cam 143 to move the platen upwardly from the phantom line lower position to the solid line position shown in Fig~lre 1 1. A spring 1~9 presses the platen with a small force during heating and Belleville springs 190 press the platen with a greater force for bonding the melted ends.
A heater bar 147 is mounted for transverse movement by a cam follower 148 that follows a heater bar cam 149. The heater bar moves between the two runs of strap and melts the strap as the platen presses the straps 10 together by spring 189 and then is removed prior to final presslng of the straps together by the platen through spring 190. The left hand gripper yoke 120a and the platen yoke 138a are pivotally mounted on an inner slide 160 that is reciprocally mounted for transverse movement. Springs 162 urge the left hand gripper and platen to seat against their respective yokes. The inner slide is reciprocated by a follower 163 that rides between cam surfaces on an inner slide cam 164 and the back of cover plate cam 11~. Thus while the platen and left hand gripper can move up and down they also are moved transversely by the inner slide. Springs 170 move the cover plate to the left and the cam follower 118 moves it transversely to the right.
OPERAT ION
The operation of the cutting and sealing head 12 is best described with a complete overall operation of the machine. In the start condition the strap S has been loaded in the machine and fed around the track 10. The main drive motor M is running. The position of all elements of the machine are shown as in the drawings. At a signal to apply a strap the trigger solenoid 43 energizes and pulls the trigger away from the single revolution clutch 45.
This releases the clutch and engages the drive with a cam shaft 180 on which all of the various cams are mounted. The cam shaft begins to rotate and releases the right hand gripper 128. The right hand gripper is driven upward 30 by the Belleville springs 134 and anchors the free end of the strap (in from its terminal edge~ against the cover p:ate 116. Continued rotation of the cam shaft causes the inner slide 160 to move transverse~y to the right away from the strap. Since the platen 138 and the left hand gripper 120 are rnounted on the inner slide they also are pulled away from the strap to clear the strap area ~ ~9~'~4 for tensioning. The retraction of the inner slicle also opens the strap guide track 10. This occurs by paddles 182 and 18~ wh7ch are on the platen and left hand gripper, respectively, and which engage the track bars 110. Motion of the track pads 106 causes the stripper pins 108 to push the strap free of thetrack groove 102. Once the platen and le Ft hand gripper are clear oF the strap and the track is open the tenslon cam 73 drives the tension arm 70 in a counterclockwise direction (as viewed in Figure 1) and pushes the front plate 6~ to the right to begin tensioning.
The first motion of the front plate allows the anchor block 56 to be swung down and clamp the strap to the anvil 51. Continued motion of the front plate 62 causes the strap to be drawn from the track down on the packa~e.
The strap is drawn by the alternate sets of moving and fixed rollers 49 and 48.
When the strap is around the package and no more strap can be drawn from the track the tension in the strap increases and trips the anchor which releases and allows the strap to be drawn from the accummulator so that the front plate can complete its stroke. Toward the end of the front plate movement the tension lever roller 86 Falls down the ramp 92 and allows the tension rolls 84 and 80 ;~
to close on the strap. The strap is then drawn to the final tension by the remainder of the front plate movement.
~t the beginning of the tensioning, after the inner slide is retracted, the left hand gripper 120 and the platen 13~3 drop downward in response to the platen and left hand gripper cams. Near the end of tensioning, the inner slide 160 moves back to its initial position. During this motion the platen and left hand gripper, now in the lower position, come back underneath the just tensioned strap. This motion also allows the track to close. Thus at this moment the continuous run of the strap is confronting the trapped Free end of the strap. The left hand gripper is then raised to the up position by its cam and clamps the continuous end of the strap against the cover plate.
At the end of the tension front plate 62 movement the tension lever 86 rolls up the ramp 9~ and separates the tension rollers 80 and 8~. Just as the leFt hand gripper comes up to the press the strap against the cover plate and thus against the underside of the free end of the strap the heater blade 1~7moves in between the straps at the seal area. Once the heater blade is in place the platen 138 rises to an intermediate position and presses against the l~t~'Z~4 strap by the spring 189. During this time a cutter 186 on the surface of the right hand gripper 128 shears the continuous end o~ the strap to separate It from the suppiy. At the intermediate position the platen presses the bottom strap, heater and top strap together so that the strap is melted for sealing.
The press force is determined by a spring and plunger between the platen and the platen lever which is pivoted on the axis 168.
~ t this time a switch 200 is actuated by cam 201~ The activation of this switch energizes a feed solenoid 192 that draws the pinch roller 35 against the powered feed roller 34 by a lever 193. Because the strap is pressed between the rolls it is fed and passes through the channel 36, the groove 112 in track 10, the groove 136 in right hand gripper 12a, the groove 140 in platen 138, the groove 122 in the left hand gripper 120, the groove 102 in the track l lO as it leaves the cutting and sealing head.
When the melting of the strap is complete the heater blade is pulled back by the heater cam l~9. When the heater bar is clear of the strap the platen cam 143 drives the platen up hard against the overlapping ends oF the straps and presses the melted sections together. The Belleville springs l90 between the platen and the platen lever overcome the spring 189 and determine the pressing force. These springs 190 do not affect the heating force from 20 spring 189, however, since they do not contact the bottom of the platen until the cam forces the platen up into its final press. After the melted plastic has hardened the left hand gripper 120, the platen 138, and the right hand gripper 128 move down to their initial positions in response to their respective cams.
After the grippers and platen have started down the cover plate 116 is retracted by its cam 119 against the force of springs 170 to allow the sealed strap to leave the seaiing head. The cover plate immediately returns to the initial position after the strap is free.
After the tensioning part of the cycle ~he front tension plate 62 is returned by its cam 73 so that at the end of the cam shaft rotation the front plate 3~) is back to its initial position and has moved the dog 89 out from under the ten-sion lever 86 and has retracted the anchor block S6~ Ready for the next cycle.
At the end of the cam shaft rotation the tripper ~4 engages the single revolution clutch 45 which then disconnects the drive from the cam shaft.
Just after the cover plate 116 closes, the end of the new feeding strap ~ ~;

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enters the sealing head and strikes the stop surface 121. Feeding then stops when the strap backs up into the compartment 38. This completes the cycle of operation.
Known strapping machines start the strap feecling part oF the cycle only after the seal has been made ancl aFter the strap has been ejected From the machine or require that the strap be shiFted sideways to clear the loop being sealed from the new strap being fed. ~s descr1bed above, in the inven- ~;
tion oF this application Feeding of the new strap occurs in a single plane and during ~he sealing operation thus shortening the total cycle time. Known 10 strapping machines also use separate actuators such as air cylinders or sole-noids to provide the opening force for the track~ In the invention of this appli-cation the motion of the gripper and platen in the sealing and cutting unit provide - ;~
this opening force and is much simpler in construc~ion and operation and far more reliable. Known strapping machines rely on the lateral stiFfness of the strap to keep the straps aligned with each other in the seal area. Since the slides and guides employed in known strapping machines and always the heater blade are moving sideways relative to the strap, there is a tendency in the known strapping machines for the straps to be moved out of alignment thus producing misaligned seals. In the invention of this application a stripper 20 bar 203 is advantageously provided to keep the two straps align~d rather than solely relying on lateral stiffness of the strap. In known strapping machines the gripper for holding the free end of the strap prior to tensioning is generally done either by separate triggering mechanisms such as cylinders or solenoid or by the technique of coupling the gripper with motion of the seal head then ;
stopping the head for tensioning and finally restarting the head to complete the seal after tensioning is complete. In the invention of this application the initial gripper is applied, tensioning and sealing are all accomplished with one revolu tion of a cam shaft giving simplicity, reliability and a very high-speed rnachine.
While the preFerred embodiment of the invention has been illustrated 30 and described and the known advantages apparent have been discussed, it should be understood that variations and other advantages will be apparent to one ~ ~
skilled in the art without departing from the principles herein. ~ccordingly, the ~ -invention is not to be limited to the specific embodiment illustrated in the drawings.

Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A machine for wrapping straps around objects, comprising:
a strapping compartment;
a track encircling the compartment;
a cutting and sealing unit positioned along said track for cutting and joining the cut ends of the strap to-gether, the improvement comprising:
said track having an open rigid strap guide member forming a partial loop having an upper portion, a lower por-tion and opposed end portions, a closure member having upper, lower and end portions confronting said corresponding portion of the open strap guide for closing the opening to form a closed path for guiding movement of the strap around an object in the compartment, and means for engaging only one of said track guide or closure member portions for moving the entire closure member or track guide as a unit away from its confron-ting closure member or guide to release the strap from the guide.

2. The machine of claim 1, wherein said track guide is moved away from said closure member.

3. The machine of claim 2, said cutting and sealing unit including a movable element for joining the cut ends, said means for engaging the track guide including link means coupled to said movable element for opening the track guide in response to movement of said movable element of said cutting and sealing unit.

4. The machine of claim 2, including stripper pins extending into said strap guide and passing into the path of the strap and against the strap when the strap guide is moved away from said closure member to push the strap clear of the strap guide.