Transverse sealer for packaging machine

A transverse sealer for a packaging machine has a pair of seal jaws for sealing a film after it is made into the shape of a bag by a former and the bag is filled with articles to be packaged. The pair of seal jaws are disposed on opposite sides of the path of the film and downstream to the former. A pair of rotary arms supporting these seal jaws is moved towards and away from each other such that the seal jaws move in straight trajectories along the path of the film and is so controlled that the compressive force between the seal jaws can be maintained at a specified level according to the thickness and material property of the film.

BACKGROUND OF THE INVENTION 
This invention relates to a transverse thermal sealer for sealing a 
packaging material used in a packaging machine for concurrently filling a 
bag with articles such as foods and making a packaged product. 
A bag-making packaging machine for concurrently forming a bag, filling it 
with articles such as foods and making it into a packaged product, such as 
a so-called pillow-type packaging machine, is adapted to seal the mutually 
superposed longitudinal side edges of a belt-like elongated packaging 
material (hereinafter referred to as a film) while this film is being 
transformed into the shape of a bag by means of a former, and to 
thereafter transversely seal the bottom of the film, while the tubularly 
formed film is being pulled, by means of a pair of transverse thermal 
sealing means disposed below the outlet of the filling cylinder used for 
filling the tubular film with articles to be packaged. Since such a 
packaging machine is capable of simultaneously and continuously forming 
bags and filling them with articles to be packaged, it is considered an 
apparatus with high workability. 
Japanese Patent Publication Tokkai 235006/87 disclosed an apparatus of the 
so-called rotary driving type adapted to cause the heating surfaces of its 
transverse sealing means to contact the film while the transverse sealing 
means are moved linearly in the direction in which the film is being 
pulled, such that a sufficiently long time can be spent for the transverse 
sealing process even if the period of cyclic packaging operation is 
shortened. For the purpose of causing the transverse sealing means to move 
in a linear trajectory, however, this apparatus makes use of D-shaped 
grooves to guide these means, while causing them to undergo a cyclic 
motion. In other words, their linear trajectory and the compressive force 
between them are uniquely determined, and the film may be subjected to an 
unreasonable force from them, depending on the thickness, material 
property and/or width of the film. As a result, the film may be damaged, 
or the apparatus may fail to reliably perform a transverse sealing 
process. 
Packaging machines of the so-called intermittent driving type are also 
known. They are structurally simpler, although disadvantageous from the 
point of view of reducing the period of cyclic motion, and are 
characterized as pulling the film intermittently and carrying out the 
transverse sealing while the film is stopped. The method of using a 
hydraulic (oil-pressure) cylinder has been known in this connection for 
compressing the transverse sealing means against each other and adjusting 
the compressive force between them by controlling this pressure cylinder. 
Such a cylinder, however, tends to make the apparatus bigger as a whole, 
and there arises the problem of keeping the oil for the cylinder away from 
the articles to be packaged. 
The present invention has been accomplished in view of these problems, and 
its first object is to provide a transverse sealer for a packaging machine 
of the rotary driving type (rotating type) capable of adjusting the 
compressive force between its transverse sealing means to a set level 
according to the thickness, material property and width of the film. 
A second object of the invention is to eliminate the hydraulic cylinder 
from a packaging machine of the intermittent driving type such that the 
packaging machine can be made compact and the contamination by oil of 
articles to be packaged can be prevented. 
SUMMARY OF THE INVENTION 
A transverse sealer according to the present invention for a packaging 
machine, with which the first object mentioned above can be accomplished, 
functions to form a belt-like film into the shape of a bag and to seal it 
transversely to the direction of motion of the film after it is filled 
with articles to be packaged, and comprises a pair of transverse sealing 
means disposed opposite to each other across the path of the film and on 
the downstream side of a bag-forming means for transforming the film into 
a specified shape for forming a bag, a pair of rotary driving means for 
causing this pair of transverse sealing means to rotate in synchronism 
with and near each other in the same direction as that of the motion of 
the film, and a trajectory-compression adjusting means for not only 
causing the pair of transverse sealing means to move in a linear 
trajectory along the aforementioned path of the film by moving the rotary 
driving means away from or towards each other, but also maintaining the 
compressive force between the transverse sealing means at a specified 
level, while the film is being sandwiched between the transverse sealing 
means by the rotary driving means. With a transverse sealer thus 
structured, the trajectory-compression adjusting means causes the pair of 
transverse sealing means to move in a linear trajectory along the path of 
the film and maintains the compressive force therebetween to a desired 
level such that the film, which is being supplied continuously, can be 
dependably sealed in the transverse direction according to the thickness, 
material property and width of the film. 
According to a preferred embodiment of the invention, there is also 
provided a stroke adjusting means for adjusting the distance of stroke by 
the transverse sealing means along the linear portion of their trajectory. 
In other words, a distance of stroke, or a sealing time, appropriate for 
the thickness, material property and width of the film can be selected for 
a suitable transverse sealing of the film. 
According to another preferred embodiment of the invention, the 
trajectory-compression adjusting means is disposed so as to be movable in 
the direction in which the pair of transverse sealing means moves away 
from or towards each other. It comprises a pair of mobile frames 
supporting individually the pair of rotary driving means for receiving the 
reaction from the force of compression, a linear-to-rotary motion 
conversion means for converting the relative motion between the mobile 
frames due to the aforementioned reaction into a rotary motion, a 
separation-controlling motor for causing the pair of mobile frames to move 
in the aforementioned direction of motion away from or towards each other 
through this motion conversion means, and a control means for driving this 
separation-controlling motor at a constant set torque such that the pair 
of transverse sealing means can move in a specified trajectory including a 
linear section. With such a structure, the compressive force can be 
maintained at a level corresponding to the torque set for the 
separation-controlling motor. Since the trajectory-compression adjusting 
means has both the function of moving the pair of transverse sealing means 
in a desired trajectory and the function of maintaining the compression 
therebetween at a constant level, the structure of the machine as a whole 
can be made simpler than if these two functions are performed by two 
separate mechanisms. Since a motor is used instead of a hydraulic 
cylinder, furthermore, the apparatus can be made more compact and the 
possibility of contamination by oil is also eliminated. 
According to still another preferred embodiment of the invention, the pair 
of mobile frames, the separation-controlling motor and the control means, 
of which the trajectory-compression adjusting means is comprised, also 
serve as parts of the stroke adjusting means. This additionally 
contributes to the reduction in size of the machine. 
The stroke adjusting means may be structured differently, with a shifting 
means for shifting the pair of rotary driving means by a set distance in 
the direction of travel of the film when the transverse sealing means 
return to their starting positions for the sealing. With a structure like 
this, the control becomes easier because the pair of transverse sealing 
means follows a simple trajectory which is a combination of a straight 
line and a semicircular arc. This shifting means may be set so as to be 
movable in the direction of motion of the film and provided with a 
shifting frame for supporting the pair of rotary driving means and a 
longitudinal shift motor for moving this shifting frame in the same 
direction of motion. With this structure, too, the apparatus can be made 
compact and contamination by oil can be prevented because use is made of a 
motor instead of a hydraulic cylinder. 
According to a further preferred embodiment of the present invention, there 
is also provided an acceleration-deceleration mode setting means for 
causing the pair of rotary driving means to gradually separate from each 
other before the transverse sealing means reach starting positions for 
sealing and to gradually move toward each other after the transverse 
sealing means reach their end positions of sealing. This contributes to a 
smooth movement of the transverse sealing mechanism because sudden motion 
of the rotary driving means at the starting and end positions for sealing 
can be eliminated. 
According to a still further preferred embodiment of the invention, each of 
the transverse sealing means has a stripping plate and the 
trajectory-compression adjusting means includes a stripping mode setting 
means for setting the trajectory of the transverse sealing means such that 
the stripping plates will stroke the surfaces of the film prior to the 
sealing process in order to prevent the articles to be packaged from 
becoming trapped inside the sealed section of the film. This embodiment 
contributes to a dependable sealing by eliminating the possibility of 
articles getting trapped between the sealing surfaces. 
According to still another preferred embodiment of the invention, at least 
one of the pair of transverse sealing means is provided with a returning 
means for pushing it towards the other of the transverse sealing means by 
an elastic restoring force proportional to displacement. With the 
returning means thus provided, the transverse sealing means, to which it 
is provided, can return to its normal position when it becomes sloped with 
respect to the other such that the distance between them changes. In this 
manner, pressure can be applied uniformly to the film from one position to 
another between the pair of transverse sealing means. 
A transverse sealer according to the present invention for a packaging 
machine, with which the second object mentioned above can be accomplished, 
comprises a pair of transverse sealing means disposed opposite to each 
other across the path of the film and on the downstream side of a 
bag-forming means for transforming the film into a specified shape for 
forming a bag, and a compression adjusting means for not only causing the 
pair of transverse sealing means to move towards or away from each other 
so as to be able to sandwich a specified sealing area of the film between 
them for sealing, but also maintaining the compressive force between the 
transverse sealing means at a specified level. The compression adjusting 
means is disposed so as to be movable in the direction in which the pair 
of transverse sealing means moves away from or towards each other, and 
comprises a pair of mobile frames for supporting individually the pair of 
transverse sealing means and receiving the reaction of the force of 
compression, a linear-to-rotary motion conversion means for converting the 
relative motion between the mobile frames due to the aforementioned 
reaction into a rotary motion, and a separation-controlling motor for 
causing the pair of mobile frames to move in the aforementioned direction 
of motion away from or towards each other through this motion conversion 
means. 
When a packaging machine of the intermittent driving type thus structured 
is used for thermal sealing while the film is stopped, the compressive 
force between the pair of transverse sealing means is maintained at a 
specified level. Thus, the machine can carry out transverse thermal 
sealing appropriately according to the thickness, material property and 
width of the film. Since a motor is used instead of a hydraulic cylinder, 
furthermore, the machine can be made compact and the problem of 
contamination of the articles to be packaged by oil can also be eliminated 
.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Embodiments of the present invention will be described next with reference 
to the accompanying drawings. 
FIG. 1 shows a pillow-type packaging machine equipped with a transverse 
sealing mechanism according to a first embodiment of the invention. This 
packaging machine is of the type without a filling cylinder and is 
structured such that after a belt-like film S is bent into a tubular form 
by means of a former 2 below a hopper 1 for making bags therefrom, a pair 
of pull-down belts 3 each disposed therebelow with a suction chamber 4 
pulls its outer surface by the suction force to maintain it in the 
cylindrical form while a longitudinal sealing is performed along its 
mutually superposed longitudinal edges a by means of a longitudinal sealer 
5. The film S is thereafter sent to a transverse sealer 10 to be described 
in detail below. 
The transverse sealer 10, disposed below the pull-down belts 3, is for 
sealing the film S in a transverse direction across the direction in which 
it is transported, and is comprised of a pair of front and back rotary 
arms 11 (serving as rotary driving means) for supporting a pair of 
transverse seal jaws 20 opposite to each other across the path of travel 
of the film S such that they always face the same directions and undergo a 
rotary motion in synchronism with respect to each other, and pairs of left 
and right outer mobile frames 30 and inner mobile frames 34 capable of 
causing the axes of rotation of the rotary arms 11 to move towards or away 
from each other. The rotary arms 11 are adapted to rotate such that the 
directions R of their rotation will match the direction of motion A of the 
film S when the pair of transverse seal jaws 20 approaches each other. 
As shown in FIG. 2, which is a sectional view for showing one of the rotary 
arms 11 in detail, each rotary arm 11 is of the form of a three-sided 
frame with left and right arms 12 connected to each other by a connecting 
shaft 13. One of the arms 12 has its end section affixed to a support 
shaft 14 protruding inwardly from the mobile frames 30 and 34 on one side 
(left-hand side in FIG. 2). The other of the arms 12 has its end section 
affixed to a power input shaft 15 protruding inwardly from the mobile 
frames 30 and 34 on the other side (right-hand side in FIG. 2). The rotary 
arms 11, thus structured, are adapted to be rotated around the shafts 14 
and 15 by driving power transmitted through the power input shaft 15. 
Numerals 17 indicate sleeves which are rotatably supported around the 
connecting shaft 13 and serve to support the seal jaw 20. The transverse 
seal jaw 20 for thermally sealing the tubularly formed film S in the 
transverse direction is affixed to these sleeves 17. One of the sleeves 17 
is formed unistructurally with a planet gear 21. 
A sun gear 24 is affixed to a fixed shaft 23 which penetrates the support 
shaft 14. The sun gear 24 and the planet gear 21 have the same number of 
gears and are coupled to each other through an idler gear 22. 
Numeral 25 indicates a Schmidt coupling mechanism comprised of three disks 
25a, 25b and 25c connected through a link 26 (shown in FIG. 1). The first 
disk 25a of each Schmidt coupling mechanism 25 is connected to a drive 
shaft 27 of an arm-rotating servo motor 29 and the third disk 25c of each 
Schmidt coupling mechanism 25 is connected to the power input shaft 15 
such that the rotary motion of the drive shaft 27 is communicated to the 
power input shaft 15 independent of variations in the angle of rotation or 
transmitted torque or any axial shift between them. In this manner, the 
pair of rotary arms 11 can be rotated in mutually opposite directions 
through mutually engaging gears 28 (shown in FIG. 1) affixed on the drive 
shafts 27 for the Schmidt coupling mechanisms 25. 
The outer and inner mobile frames 30 and 34 are for supporting the pair of 
rotary arms 11 such that the distance between them can be varied. The 
pairs of outer and inner mobile frames 30 and 34 are respectively 
connected to each other near the back ends by a connecting plate 31 and 35 
in the form of a three-sided frame surrounding the rotary arms 11. They 
are assembled such that the outer mobile frames 30 can slide in the 
forward-backward direction on a main body frame 46 and that the inner 
mobile frames 34 can each slide inside one of the outer mobile frames 30 
in the forward-backward direction. 
Numeral 38 indicates a turnbuckle for moving the outer and inner mobile 
frames 30 and 34 in the forward-backward direction in a mutually 
coordinated manner such that the transverse seal jaws 20 can be moved in a 
desired D-shaped trajectory including a linear section. As shown in FIG. 
3, this turnbuckle 38 is axially supported by a frame structure 45 
provided between the outer and inner mobile frames 30 and 34. The 
turnbuckle 38 has a part 38a with a right-handed screw and a part 38b with 
a left-handed screw engaging respectively with the connecting plates 31 
and 35 for the outer and inner mobile frames 30 and 34 through linear 
bearings 32 and 36 such that the outer and inner mobile frames 30 and 34 
can be moved in mutually opposite directions to cause the pair of rotary 
arms 11 to move towards or away from each other by turning the turnbuckle 
38 selectively in the positive or negative direction. The linear bearings 
32 and 36 may be of a currently available type having many balls which 
engage with the screw parts 38a and 38b so as to add torque to an 
arm-shifting motor 40, or to turn the turnbuckle 38 when a force is 
applied to the mobile frames 30 and 34 in the forward-backward direction X 
by the reaction to the sealing pressure. The turnbuckle 38 and the linear 
bearings 32 and 36 may together be considered to form a linear-to-rotary 
motion conversion means G for converting the relative motion between the 
pairs of mobile frames 30 and 34 due to the aforementioned reaction to the 
compressive force between the pair of seal jaws 20 into a rotary motion. 
Use as the aforementioned arm-shifting motor 40, which is connected to the 
turnbuckle 38 through a timing belt 39 as shown in FIG. 3, may be made of 
an AC servo motor capable of freely switching between torque-controlled 
and speed-controlled modes of operation. In the torque-controlled mode of 
operation, the torque of the motor 40 is kept at a specified level 
independent of its speed but this specified level can be varied suitably. 
In the speed-controlled mode of operation, its rotational speed can be 
made constant independent of the torque. As will be explained more in 
detail below, the arm-shifting motor 40 is controlled by a control circuit 
so as to be able to rotate in either direction in coordination with the 
arm-rotating servo motor 29 for rotating the rotary arms 11 such that the 
transverse seal jaws 20 will each travel in a trajectory including a 
straight portion of length L as shown in FIG. 5. In FIG. 1, numeral 47 
indicates a partition plate. 
FIG. 4 shows a circuit for controlling the arm-rotating servo motor 29 and 
the arm-shifting servo motor 40. FIGS. 5-8 show the motion of the rotary 
arm 11, as well as the operations of the arm-rotating and arm-shifting 
servo motors 29 and 40 in various modes of transverse sealing operation. 
In FIG. 4, numeral 51 indicates a detector for detecting the angle of 
rotation by the rotary arms 11 from a certain reference position I. This 
angle is detected from the angle of rotation of the arm-rotating servo 
motor 29, and a pulse signal proportional to the angle of rotation by the 
rotary arms 11 is transmitted from a pulse transmitter 52 connected to 
this detecting means 51 to a control unit 53. Numeral 48 indicates a 
mode-selecting means such as a keyboard for specifying a desired 
transverse sealing mode of operation. Numeral 49 indicates a 
film-specifying means such as a key board for specifying the material 
property, thickness, width, etc. of the film. As one of available 
transverse sealing modes, such as the "basic transverse sealing mode" 
shown in FIG. 5, the "end acceleration mode" shown in FIG. 6, the 
"transverse mode of operation with stripping" shown in FIG. 7, or the "end 
acceleration mode with stripping" shown in FIG. 8 is specified through the 
mode-selecting means 48 and the material property, width, etc. of the film 
are specified through the film-specifying means 49, an appropriate one of 
programs stored in a memory means 55 is retrieved therefrom through a 
retrieving means 54 and a program signal is outputted to the control unit 
53 and executed. These programs stored in the memory means 55 are prepared 
for different modes of operation and according to different compression 
and distance of stroke at the time of sealing to be explained below. 
As a pulse signal from the pulse transmitter 52 and a mode-dependent 
program from the memory means 55 are inputted into the control unit 53, 
mode-setting means, such as those corresponding to the basic mode (53a), 
the end acceleration mode (53b) and the stripping mode (53c), may be 
activated. The control unit 53 thereupon outputs control signals to a 
motor-driving means 56 in order to control the rotation of the 
arm-rotating servo motor 29 so as to vary the angular velocity of the 
rotary arms 11 during the transverse sealing process, and to another 
motor-driving means 57 in order to control the timing for switching the 
arm-shifting servo motor 40 so as to vary the positions of the axes of 
rotation of the rotary arms 11 during the transverse sealing process. The 
mobile frames 30 and 34, the linear-to-rotary motion conversion means G, 
the arm-shifting servo motor 40 and the control unit 53 may be regarded as 
constituting a trajectory-compression adjusting means H. Since the length 
of the transverse sealing process (that is, the stroke distance) varies as 
the centers of rotation of the rotary arms 11 are shifted, the remainders 
of the above with the linear-to-rotary motion conversion means G has been 
removed (that is, the mobile frames 30 and 34, the arm-shifting servo 
motor 40 and the control unit 53) may be regarded as constituting a stroke 
adjusting means J. 
Next, the operation of the system thus structured will be described. Let us 
assume first that the basic transverse sealing mode, as shown in FIG. 5a 
with the length of transverse sealing given by L1, has been selected 
through the mode-selecting means 48 and that material property and 
thickness of the film S have been specified through the film-specifying 
means 49. In response, a program for such a basic transverse sealing mode 
of operation and corresponding to the specified material property and 
thickness of the film S is selected out of the many programs stored in the 
memory means 55 and retrieved by the retrieving means 54. The basic mode 
setting means 53a is activated according to the retrieved program, and the 
arm-shifting servo motor 40 begins to rotate in the positive direction 
after the rotary arms 11 begin to rotate from the starting position I and 
as they reach the starting position II for the transverse sealing process 
as shown in FIG. 5a. Subsequently, the arm-shifting servo motor 40 rotates 
in the negative direction from the mid-point III until the rotary arms 11 
reach the end point IV of the transverse sealing process so as to move the 
pair of rotary arms 11 away from and towards each other through the outer 
and inner mobile frames 30 and 34 engaging the turnbuckle 38. In the 
meantime, the film S is sandwiched between the pair of transverse seal 
jaws 20 and moves at the same rate as its normal speed of travel. 
Accordingly, the seal jaws 20 supported at the tips of the rotary arms 11 
begin to travel in contact with the surface of the film S, that is, in 
straight lines. During this course of operation, the arm-shifting servo 
motor 40 is operated in the torque-controlled mode such that its torque is 
maintained at a specified constant level T.sub.0, as shown in FIG. 5b. 
Thus, the compressive force on the film S from the seal jaws 20 can be 
kept as constant as possible. In the meantime, the arm-rotating servo 
motor 29 allows the speed of rotation of the rotary arms 11 to vary 
according to the torque applied thereon, causing the seal jaws 20 to move 
along the film S to thereby effect the transverse sealing. During this 
course of operation, the centers of rotation of the rotary arms 11 
supporting the seal jaws 20 move in the forward-backward direction X, 
balancing the rotary torque of the turnbuckle 38 due to the reaction to 
the aforementioned compressive force against the constant torque T.sub.0 
of the servo motor 40 such that the compressive force is maintained at a 
constant level. This constant level of the compressive force can be 
adjusted by varying the magnitude of T.sub.0. 
If another basic transverse sealing mode with a shorter stroke distance L2 
is specified, the arm-shifting servomotor 40 starts to rotate in the 
positive direction according to the corresponding program as shown by 
broken lines in FIGS. 5a and 5b, shifting the center of rotation from O to 
O', and thereafter causes the seal jaws 20 to move on a shorter straight 
path between points II' and IV'. 
If the user specifies the end acceleration mode for causing the seal jaws 
20 to accelerate and decelerate at the beginning and end of the transverse 
sealing, the end acceleration mode setting means 53b is activated. In this 
mode of operation, the arm-shifting servo motor 40 is gradually 
accelerated to gradually shift the positions of the center of rotation of 
the rotary arms from O to O' as shown in FIG. 6 before the starting point 
II is reached. After the end point IV is reached, the motor 40 is 
gradually decelerated. In other words, the program for this mode of 
operation provides an acceleration zone from II' to II and a deceleration 
zone from IV to IV' as shown in FIG. 6b. In this mode of operation, sudden 
separation of the pair of rotary arms 11 at the starting point II of the 
transverse sealing, as well as sudden approach at the end point IV, can be 
avoided, and the transverse sealer 10 can generally operate more smoothly. 
The stripping mode setting means 53c is activated if the user specifies the 
stripping mode of operation shown in FIG. 7 wherein the articles inside 
the film S are "stripped", or caused to drop down, prior to the transverse 
sealing so as not to be caught between the seal jaws 20. In this mode of 
operation, the control unit 53 causes stripping plates 61 to be pressed 
against the film S by means of springs 60 when the rotary arms 11 are 
still separated from each other (at the starting point of stripping II') 
before reaching the starting point II of the transverse sealing. 
Thereafter, the stripping plates 61 are caused to move faster than the 
film S, thereby stripping the film S until the mid-point III (the end 
point of stripping) is reached. At the moment, the center of rotation of 
the rotary arms 11 is moved from B to C to thereby cause the seal jaws 20 
to compress each other. From this moment until the end point IV of the 
transverse sealing is reached, the arm-shifting servo motor 40 is operated 
in the torque-controlled mode such that the seal jaws 20 are moved at the 
same rate as the normal speed of travel by the film S. With the transverse 
sealer 10 operated by such a program, articles to be packaged are 
prevented from being caught between the seal jaws 20 and the sealing 
operation can be accomplished dependably. 
If the end acceleration mode of operation with stripping as shown in FIG. 8 
is specified, the sealer 10 is operated with a program providing an 
acceleration zone from II' to II before the starting point of the 
stripping and a deceleration zone from IV to IV' after the end point IV 
for the transverse sealing. 
As explained above by way of the embodiments described above with reference 
to FIGS. 1-8, transverse sealing can be performed on a continuously moving 
film S because the pair of sealing jaws 20 (serving as transverse sealing 
means) is caused to travel in a linear trajectory along the path of the 
film S by the aforementioned trajectory-compression adjusting means H. 
Since the compressive force between the pair of seal jaws 20 can be 
maintained at a constant level corresponding to a set magnitude of torque 
T.sub.0 on the arm-shifting servo motor 40, the film S can be transversely 
sealed appropriately according to its thickness, material property, etc. 
Since the stroke distance, and hence the time duration of the sealing 
operation, can be selected appropriately by the stroke adjusting means J 
according to the thickness and material property of the film S, the 
sealing operation can be performed even more appropriately according to 
the present invention. 
Since the aforementioned trajectory-compression adjusting means H has both 
the function of moving the pair of seal jaws 20 in a desired trajectory 
and the function of maintaining the compression therebetween at a constant 
level, the sealer 10 as a whole can be more simply structured than if 
these two functions are performed by two separate mechanisms. Since the 
motor 40 takes the place of a hydraulic cylinder, furthermore, the sealer 
can be made more compact and the possibility of contamination of the 
articles to be packaged by oil can be eliminated. The sealer 10 according 
to the present invention can be made compact also because the pairs of 
outer and inner mobile frames 30 and 34, the arm-shifting servo motor 40 
and its control unit 53, which constitute a portion of the aforementioned 
trajectory-compression adjusting means H, also serve as the aforementioned 
stroke adjusting means J. Instead of the aforementioned linear-to-rotary 
motion conversion means G with a turnbuckle and linear bearings, use may 
also be made of an alternative mechanism with a link mechanism or groove 
cams. 
FIG. 9 shows a second embodiment of the present invention characterized 
wherein the supporting mechanism for the seal jaws 20 is improved by 
adding a returning means. As shown in FIG. 9, wherein the same components 
as described above are indicated by the same numerals, the base ends of 
support springs 71 (serving as returning means) are attached to the inner 
edges of the pair of sleeves 17 rotatably supported by the connecting 
shaft 13 between the arms 12. These springs 71 are cantilevered and are 
for the purpose of applying a uniform compressive force to the film S over 
its entire width W. Their free ends extend inwardly toward each other and 
are attached to a seal jaw 20. 
With the returning means 71 thus provided, even if the seal jaws 20 become 
sloped like a seesaw because of the longitudinally sealed edge portions of 
the film S caught in between as the seal jaws 20 are pressed against each 
other, these support springs 71 will individually bend and supply a 
restoring force proportional to its strain to cause the seal jaw 20 
attached thereto to return towards the opposite seal jaw 20, thereby 
applying a uniform compressive force onto the film S. 
As the pair of seal jaws 20 moves in D-shaped trajectories by the rotation 
of the arms 12 of the rotary arms 11 and the motion of the mobile frames 
30 and 34 and reaches the starting point of the transverse sealing, coming 
into contact with each other with the film S sandwiched therebetween, the 
seal jaws 20 experience a force which tend to move them around the 
longitudinally sealed edges of the film S. When such a force is 
experienced by the seal jaws 20, each of the support springs 71 is bent 
according to the displacement of the seal jaw 20. At the same time, 
reactions from the support springs 71 are applied back onto the seal jaws 
20 so as to press the film S uniformly to perform the transverse sealing. 
This process will be explained more in detail with reference to FIG. 10 
which shows the pair of seal jaws 20 sandwiching therebetween a film S 
having its longitudinally sealed edges a formed in three or four layers. 
In this situation, at least one of the pair of seal jaws 20 will assume a 
sloped position like a seesaw around the longitudinally sealed edges a. 
This slope can be expressed as a function of the strains of the springs 
71. The strain .delta. is given by a formula as follows: 
EQU .delta.=pA.sup.3 /12EI=pD.sup.3 /Ebt.sup.3 (1) 
where D is the effective length of the cantilevered support spring 71, t is 
the thickness and b is the width of the plate of the spring, 2p is the 
load, and E and I are respectively the Young's modulus and the 
second-order cross-sectional moment of the spring 71. Its reaction force R 
is inversely proportional to the strain .delta. and given by 
EQU R=Ebt.sup.3 .delta./D.sup.3. (2) 
Thus, if the strain of the left-hand and right-hand support springs 71 is 
respectively .delta..sub.l and .delta..sub.r, their reaction forces 
R.sub.l and R.sub.r proportional respectively to .delta..sub.l and 
.delta..sub.r are applied to the seal jaw 20 towards the other seal jaw 20 
opposite thereto. 
Consider, for example, a load of 500 kg applied to a support spring 71 of 
effective length D=44 mm, plate thickness t=5 mm, plate width b=18 mm, and 
Young's modulus=2.1.times.10.sup.4 kg/mm.sup.2, thereby causing a strain 
of 0.5 mm and 0.4 mm to the left-hand and right-hand springs 71, 
respectively. Formula (2) then shows that the support spring 71 on the 
left-hand side exerts a reaction force of R.sub.l =278 kg to the seal jaw 
20 and that the support spring 71 on the right-hand side exerts a reaction 
force of R.sub.r =222 kg in the direction of returning to the normal 
position, providing locally uniform compression to the film S and 
restoring the strains in the springs 71. 
FIG. 11 shows a support spring of a different form. A seal jaw 20A 
according to this embodiment has an inwardly extending slit 72 formed from 
each side section thereof, and the parts which become separated by these 
slits 72 from the main part of the seal jaw 20A are formed as cantilevered 
elastic support spring parts 73. 
FIG. 12 shows a support spring of still another form. A seal jaw 20B 
according to this embodiment is formed as a hollow structure with an 
elastic hollow housing structure 200 such that the strain of the seal jaw 
20B will be made up for by a reaction force proportional to the bending of 
the housing structure 200 itself. A fluid 75 with a low melting point such 
as lead may be sealed inside the hollow interior 74 of the housing 
structure 200 for providing a uniform thermal balance to the seal jaw 20B. 
In such a situation, the housing structure 200 serves as the 
aforementioned returning means. The support springs 71 and 73 and the 
hollow elastic structure 20B may be used only as one of the pair of seal 
jaws 20. 
FIG. 13 shows still another transverse sealer according to a third 
embodiment of the invention. This sealer has both a seal jaw 20 and a 
stripping plate 61 provided at the tip of each rotary arm 11 such that the 
stripping plate 61 performs the stripping operation on the film S while 
the seal jaw 20 is on the first half of the straight line trajectory from 
I to III and the transverse sealing is carried out while the seal jaw 20 
is on the second half of this trajectory. 
Explained more in detail, means for allowing the seal jaws 20 to move in 
many different D-shaped trajectories having linear sections of different 
lengths (or many different stroke distances), or means for shifting the 
axes of rotation of the rotary arms 11 according to this embodiment of the 
invention comprises two cams 84A and 84B having different guide surfaces 
affixed to the same axis such that they rotate together and their rotary 
positions can be adjusted. At the same time, one or both of the cam axes 
85 (only the one on the right-hand side according to the embodiment shown 
in FIG. 13) are subjected to a biasing force towards the other by means of 
an air cylinder 86 such that the pair of seal jaws 20 can apply an 
appropriate pressure on the film S while they are performing transverse 
sealing between the points II and III. 
The air tube connecting the air cylinder 86 with an air supply source 87 is 
provided with an electromagnetic valve 88 which opens the air supply route 
only during the transverse sealing process between the points II and III 
and an external pilot type sequence valve 89 which is activated only when 
the contact pressure exceeds a set level such that the transverse sealing 
can be effected at a constant contact pressure. On the other hand, the 
arm-rotating servo motor is controlled so as to rotate at an increased 
speed during the stripping process between the points I and II. In this 
manner, the stripping can be completed quickly before the transverse 
sealing process is started. 
In summary, the third embodiment of the invention makes use of the 
arm-rotating servo motor and arm-shifting cams 84A and 84B in coordination 
therewith such that the rotary arms 11 are separated from each other by 
the operation of these cams 84A and 84B while the seal jaws 20 are in the 
region for stripping operation between the points I and II and the air 
cylinder 86 is not operated. In the meantime, the speed of rotation of the 
arm-rotating servo motor is increased such that the stripping plates 61 
will move in a straight trajectory faster than the normal speed of travel 
of the film S so as to effect required stripping thereon. When the seal 
jaws 20 start the transverse sealing process to be effected between the 
points II and III, the arm-rotating servo motor is rotated at a constant 
speed and the electromagnetic valve 88 is opened so as to introduce air 
into the air cylinder 86 through the external pilot type sequence valve 
89. In this manner, an appropriate compressive force according to the 
thickness and material property of the film S is applied between the seal 
jaws 20 as the arm-shifting cams 84A and 84B are pressed towards the other 
cams 84A and 84B on the opposite side. 
The stripping process between the points I and II is controlled by one of 
the pairs of cams 84B, while the transverse sealing process between the 
points II and III is controlled by the other pair of cams 84A. Thus, the 
stroke distances of these two processes I-II and II-III can be varied by 
controlling the motion of the cams 84A and 84B. These pairs of cams 84A 
and 84B, however, may be replaced by different means such as air cylinders 
for shifting the axes of rotation. 
FIG. 14 shows still another transverse sealer according to a fourth 
embodiment of the present invention characterized as having a shifting 
means K for shifting the positions of the rotary arms 11 supporting the 
seal jaws 20 in the direction of motion of the film S by a specified 
stroke distance during the transverse sealing process. A pair of side 
boards 91 and 92 is provided to hold the base parts of the rotary arms 11 
and is connected to each other by a pair of connecting boards 93 and 94 to 
form a mobile frame 90 surrounding the rotary arms 11 and adapted to slide 
vertically upward and downward, guided by four guide rods 95 provided to 
the main body frame 46. Numeral 96 indicates a driving motor (or an 
arm-raising motor) for moving the mobile frame 90 upwards and downwards 
for moving the seal jaws 20 in elliptical trajectories of a specified 
shape. An AC servo motor capable of changing the direction of rotation at 
a specified timing may be used as this driving motor 96. The 
aforementioned shifting means K may be regarded as consisting of the 
mobile frame 90, the guide rods 95 and the driving motor 96. Every time 
the seal jaws 20 come near the mutually contacting positions or the most 
distantly separated positions, a control unit to be described below causes 
the driving motor 96 to rotate in the positive or negative direction to 
thereby move the rotary arms 11 upward or downward by a specified distance 
through a bracket 98 on the mobile frame 90 engaging a screw bar 97 
serving as the drive shaft of the driving motor 96. The other components 
shown in FIG. 14 are the same as those shown in FIG. 1 and hence are 
indicated by the same numerals. 
FIG. 15 shows a circuit for controlling the arm-rotating motor 29 and the 
arm-raising motor 96, and FIG. 16 is for showing the movement of the 
rotary arms 11 by their coordinated operations. Numeral 101 in FIG. 15 
indicates a detector for detecting the angle of rotation by the rotary 
arms 11 from a certain reference position I. This angle is detected from 
the angle of rotation of the arm-rotating motor 29, and a pulse signal 
proportional to the angle of rotation by the rotary arms 11 is transmitted 
from a pulse transmitter 102 connected to this detecting means 101 to a 
control unit 103. Numeral 100 indicates a film-specifying means such as a 
key board for specifying the material property, width, thickness, etc. of 
the film. If the width of the film, etc. are specified, a retrieving means 
104 is activated and retrieves a corresponding program out of many stored 
in a memory 105, outputting it to the control unit 103 to have it carried 
out. When the pulse signal from the pulse transmitter 102 and a signal 
from the film-specifying means 100 are received, the control unit 103 
outputs a control signal to the motor-driving means 106 to control the 
rotary motion of the arm-rotating motor 29 so as to vary the angular speed 
of the rotary arms 11 during the course of transverse sealing. At the same 
time, whenever the rotary arms 11 reach the transverse sealing zone II-II' 
or the corresponding zone IV-IV' in their upward trajectory with reference 
to FIG. 16, a control signal is outputted to another motor-driving means 
107 to control the switching timing of the arm-raising motor 96 so as to 
rotate this motor 96 by an angle corresponding to a specified stroke 
distance L. The aforementioned shifting means K and the control unit 103 
together may be regarded as constituting the stroke adjusting means J. 
Next the operation of the sealer thus structured will be explained. To 
start, the material property, thickness and/or width of the film S is 
specified through the film-specifying means 104. In response, the 
arm-raising motor 96 starts to rotate in the positive direction according 
to a preliminarily retrieved program when the rotary arms 11, starting its 
motion from the preliminarily determined starting point I, reaches the 
starting points II for the transverse sealing. The mobile frame 90 is 
thereby lowered at the same speed as that of the film S in its direction 
of motion A by a distance of stroke L determined by the material property, 
etc. of the film S. As a result, the seal jaws 20 supported by the rotary 
arms 11 begin to move downward in contact with the film S over a stroke 
distance L determined by the specified width, material property or 
thickness of the film S, while the arm-rotating motor 29 increases and/or 
decreases its rotational speed according to the variation on its torque, 
so as to carry out the transverse sealing. When the transverse sealing is 
completed at the end points II', the seal jaws 20 continue to rotate 
further and when they reach the points IV where they are farthest apart on 
their trajectories, the arm-raising motor 96 begin to rotate in the 
negative direction according to the program, raising the rotary arms 11 
upwards back to their starting positions. 
The fourth embodiment of the invention is advantageous because the seal 
jaws 20 each move in a relatively simpler trajectory made of a circular 
arc and a straight line segment instead of a D-shaped trajectory as in the 
case of the third embodiment of the invention. As a result, control of the 
motion is simpler. 
Although the fourth embodiment of the invention was described above as 
using the screw bar 97 of the arm-raising motor 96 in order to raise and 
lower the mobile frame 90 and the rotary arms 11, other mechanisms for 
raising and lowering the mobile frame 90 may be substituted if capable of 
varying the stroke distance L of the mobile frame 90 according to the 
material property, etc. of the film S, such as a mechanism with a rack and 
a pinion. If necessary, furthermore, a sealer according to the fourth 
embodiment of the invention may be controlled such that there will be no 
relative motion between the seal jaws 20 and the film S throughout the 
distance between the points II and II' by stopping the arm-rotating motor 
29 while the arm-raising motor 96 is operating. 
The first through fourth embodiments of the present invention described 
above relate to transverse sealers of the type causing seal jaws to move 
in generally circular trajectories such that the transverse sealing can be 
effected while the film S is being transported. In contrast, FIG. 17 shows 
a fifth embodiment of the present invention related to a transverse sealer 
10A of the intermittent driving type characterized as stopping the 
transportation of the film S intermittently and carrying out the 
transverse sealing only while the film S is temporarily stopped. 
With reference to FIG. 17, the transverse sealer 10A according to the fifth 
embodiment of the invention supports its seal jaws 20 directly by the 
outer and inner mobile frames 30 and 34 without using any rotary arms. 
Thus, the pair of seal jaws 20 can be moved towards or away from each 
other by means of a jaw-shifting servo motor 40A such that the film S is 
sandwiched between them and the transverse sealing can be effected while 
the seal jaws 20 are in their mutually approached condition. The principle 
of mechanism for moving the seal jaws towards and away from each other is 
the same as that explained above with reference to FIG. 3. With reference 
still to FIG. 17, the linear-to-rotary motion conversion means G comprised 
of the pairs of outer and inner mobile frames 30 and 34, the turnbuckle 38 
and the linear bearings 32 and 36, and the jaw-shifting servo motor 40A 
together may be regarded as constituting a compression-adjusting means H1. 
As shown in FIG. 18, the jaw-shifting servo motor 40A according to the 
fifth embodiment of the invention rotates in the positive direction from 
time t.sub.1 when the pair of seal jaws 20 is farthest apart from each 
other until time t.sub.2 when it comes in contact with the film S to 
advance the seal jaws 20 in the positive direction. In the meantime, the 
motor 40A is operated in the speed-controlled mode such that its 
rotational speed will remain constant independent of changes in its 
torque. During the sealing process from time t.sub.2 until time t.sub.3, 
the servo motor 40A is controlled to produce a specified torque T.sub.0. 
Since the rotary torque of the turnbuckle 38 shown in FIG. 17 due to the 
reaction force to the compression between the seal jaws 20 is applied to 
the servo motor 40A in this situation, the servo motor 40A stops when the 
aforementioned rotary torque of the turnbuckle 38 is greater than the 
specified torque T.sub.0 of the servo motor 40A but the servo motor 40A 
turns in the positive or negative direction, when the rotary torque of the 
turnbuckle 38 is smaller than T.sub.0, so that the compression between the 
seal jaws 20 will be adjusted corresponding to the specified torque 
T.sub.0. 
Thus, when a thermal sealing process is carried out with a packaging 
machine of an intermittent driving type while the film S is temporarily 
stopped, the compression force between the pair of seal jaws 20 can be 
maintained at a specified level by means of the aforementioned 
compression-adjusting means H1. As a result, the transverse sealing 
process can be appropriately carried out on a film according to its 
thickness, material property, and width. Since use is made of a motor 
instead of a hydraulic cylinder, the sealer can be made compact and there 
is no possibility of contamination of the articles by oil. It now goes 
without saying that returning means of types similar to those shown at 71, 
73 and 200 as shown in FIGS. 9-12 may be provided to the seal jaws 20 of 
this fifth embodiment of the invention. 
Although the first through fifth embodiments of the present invention 
described above all relate to a transverse sealer to be used in a 
packaging machine of a vertical pillow type, it should be clear that the 
transverse sealer according to the present invention can be used also in a 
horizontal pillow type packaging machine. In addition, the transverse 
sealers of the present invention can also be used with a packaging machine 
of a three-side sealing type adapted to fold the film into two, to 
vertically seal its superposed edges longitudinally and then to 
transversely seal it at two places or of a four-side sealing type adapted 
to perform a vertical sealing at two places along the superposed edges and 
also along the opposite side and then to perform transverse sealing at two 
places. 
It also goes without saying that the present invention is applicable not 
only to machines for packaging food articles but also to packaging 
machines for industrial parts or products.