Apparatus for making bags or sacks from a preferably gusseted continuous tubular film of thermoplastic plastic

An apparatus is disclosed for making bags or sacks from a continuous tubular film of thermoplastic material. The continuous tubular film is moved intermittently in a downward direction to a welding device, a cutter below the welding device, and a turret-like rotary conveyor below the cutter. A bag length is received by grippers on the rotary conveyor before it is welded and cut. When thus received the bag length is welded and cut, and the conveyor indexed by one step to present succeeding grippers to the tube. The tube is then advanced another bag length so that the succeeding bag is received in the succeeding pair of grippers. The process is repeated with succeeding bags. The bags on the conveyor are successively delivered to a transfer station where the grippers are opened to release the bags.

BACKGROUND OF THE INVENTION 
This invention relates to an apparatus for making bags or sacks from a 
preferably gusseted continuous tubular film of thermoplastic material. The 
apparatus is of a type which comprises guide rollers and pinch rollers by 
which the leading end of a freely vertically depending continuous tubular 
film is adapted to be advanced in steps each corresponding to the length 
of one bag or sack to a position between welding jaws of a welding device, 
which are adapted to perform opening and closing movements in a horizontal 
plane to form successive weld seams in the film. The apparatus, also has a 
transverse cutter, which is disposed below the welding jaws, and pairs of 
grippers, which are disposed below the cutter. The grippers are provided 
on a conveyor by which the bags or sacks which have been successively 
severed from the film are adapted to be moved through a cooling section 
for cooling the bottom weld seam of each bag or sack to a transfer 
apparatus for conveying the bags or sacks to a filling device. 
When materials are to be filled into sacks by manufacturers and/or fillers, 
this is often performed by means of filling machines, which are preceded 
by a machine for making the sacks to be filled. In the latter machine a 
preferably gusseted continuous tubular film of thermoplastic plastics is 
intermittently withdrawn from a supply roll and sacks consisting of 
tubular film sections provided with bottom welds are severed from the 
continuous tubular film shortly before the sacks are filled. When the 
sacks have been filled, they are provided with a closing seam at their top 
end. To ensure an adequate cooling of the bottom seam weld which has been 
made shortly before the sacks are filled so that said seam will have an 
adequate strength before the sacks are filled, it is advisable to feed the 
sacks provided to the filling apparatus through a cooling section. 
German Patent Specification 24 18 228 describes an apparatus of the kind 
described hereinbefore and in which the cooling section has two mutually 
opposed chain conveyors, which are synchronously driven and have endless 
chains which are trained each around two chain sprockets on vertical axes. 
The chains carry spaced apart grippers, which while moving along the 
confronting and coplanar inner courses of the chains grip mutually 
opposite edge portions of the bags which have been provided with bottom 
welds and convey the bags to a transfer apparatus for conveying the sacks 
to the filling device. The known apparatus is rather expensive because two 
revolving endless chains and means for driving them are required. Only the 
grippers moving along the two confronting inner courses of the chains are 
utilized to convey the sacks whereas the grippers have no conveying 
function as they move around the driving and reversing sprockets and along 
the outer chain courses. 
British Patent Specification 919,392 discloses an apparatus which is used 
to make and fill sacks and comprises a turret that is rotated in angular 
steps. In this apparatus the bottom seam is welded after the continuous 
tubular film has been advanced to the extent of one sack length so that 
the time required for a step is determined by the time required for the 
welding operation and by the time which is required to advance the 
continuous tubular film to the extent of one sack length. Also, this 
apparatus cannot be adjusted in a simple manner to accommodate different 
sack sizes because the welding device for forming the bottom seam is 
spaced a constant distance below the grippers whereby the elevation of the 
welding jaws must be changed for a change of the length of the sack. 
Moreover, one of the stations associated with the turret constitutes the 
filling station so that a sufficiently long time for cooling the bottom 
seam weld is not assured. 
A similar turret-like apparatus for making and filling sacks or bag is 
known from German Patent Specification 26 08 456. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide an apparatus of the kind 
described and which comprises a conveyor that includes a cooling section 
and comprises grippers which during intermittent operation of the conveyor 
perform virtually no idle movements. 
In accordance with the invention, the conveyor comprises a hub-like 
carrier, which is mounted for rotation about a vertical axis and has 
radial arms, with the grippers arranged in pairs at the free ends of said 
arms. As a result, the cooling section in accordance with the invention is 
virtually constituted by a cooling turret, by which the sacks, which have 
been provided with a bottom weld and severed from the continuous tubular 
film are conveyed from a welding or receiving station along a circular 
path to an apparatus for transferring the sacks to a filling device. If 
the apparatus in accordance with the invention comprises four radial arms, 
as is preferred, a welding device and a cutting device will be provided 
above the first station so that one step of each cycle of operations 
performed to make a sack comprises the movement of a sack, which has 
previously been provided with a bottom weld, into the opened first pair of 
grippers from above and an advance of that sack by the length of one sack. 
Thereafter, the sack is gripped and cut off. A succeeding bottom weld is 
then formed at the leading end of the continuous tubular film while the 
cooling turret is rotated through a further step of 90.degree. and is held 
in the resulting position until another sack provided with a bottom seam 
has been fed to the next succeeding station. In a four-armed cooling 
turret, the operation is repeated until the first arm has been rotated 
through 270.degree. in three steps. At that time the bottom weld has 
sufficiently cooled and the sack is then transferred to a transfer 
apparatus, which transfers the sack to a filling device. The time required 
for that transfer does not exceed the time which is required to make a 
sack and to move it into the grippers. It is apparent that the turret in 
accordance with the invention serves effectively to cool the bottom welds. 
Owing to the use of rotary turret, a sufficiently long cooling path can be 
accommodated within a small space. 
The apparatus in accordance with the invention differs from the apparatus 
in accordance with British Patent Specification 919,392 in that a welding 
means is disposed above the grippers and the cutting device and is spaced 
a fixed distance therefrom so that the apparatus can simply be adjusted to 
a different sack size by the selection of the extent to which the 
continuous tubular film is advanced in each step. 
The grippers of each pair of grippers for retaining a bag or sack are 
suitably spaced equal radial distances from the axis of rotation of the 
carrier. This design ensures that the bags or sacks will hang tangentially 
from the turret-like conveyor so that the apparatus may be small in 
diameter. The arms which carry the grippers suitably have the same angular 
spacing. 
Each arm of the apparatus in accordance with the invention is preferably 
provided with two grippers, each of which constitutes one of a pair of 
grippers together with the adjacent gripper of an adjacent arm. With this 
arrangement it is not necessary to provide the arms at their free ends 
with brackets having a width which is substantially as large as the width 
of the sacks. 
To constitute the grippers, the arms may be provided at their free ends 
with brackets, provided on their outside with backing jaws, which 
cooperate with movable clamping jaws, which are secured to levers pivoted 
to the brackets on vertical axes. The movable clamping jaws of each pair 
of grippers are suitably linked to each other by a link to perform opening 
and closing movements in synchronism. 
Those pairs of grippers which are disposed in the welding or receiving 
station and in the transfer station at a given time are suitably adapted 
to be opened and closed by a common actuator. Said pairs of grippers 
desirably perform their opening and closing movements in synchronism 
because a sack can be delivered during the time in which the next 
successing pair of grippers in the direction of rotation take up the sack 
which has been made last. 
In accordance with a preferred feature of the invention, the pairs of 
grippers which are disposed in the welding station and in the transfer 
station at a given time are juxtaposed, the levers carrying the movable 
clamping jaws are biased toward their opening position by springs and 
carry sliders or rollers, and a wedge-shaped spreader is adapted to be 
moved between said sliders or rollers and has side faces which constitute 
tracks or cams for cooperation with the sliders or rollers. Thus a common 
device for opening two pairs of grippers is provided, which device is 
fixed to the frame, and there is no need for providing a corotating device 
for effecting the gripper opening and closing movements. 
The spreader is desirably mounted on a lever, which is pivotally movable by 
a fluid-operable piston-cylinder unit about an axis which is stationary 
with respect to the frame. 
In accordance with a preferred feature of the invention, each lever is 
provided with a cam follower roller, which during outward pivotal movement 
the lever is adapted to enter a cam slot in a plate which is fixedly 
connected to the rotary carrier. As a result that plate constitutes a 
safety plate, which will prevent damage to the apparatus when the turret 
is inadvertently advanced through an additional angular step although tee 
spreader still extends between two sliders or rollers. 
The hub-like carrier is suitably driven by means of a drive pulley and an 
endless belt trained around the drive pulley and around a driven pulley 
that is connected to a gear motor, which is disposed between the transfer 
station and the receiving station. Because no sack workpiece is conveyed 
by the grippers between the transfer station and the welding station, 
there can be no collision between such sack workpiece and the drive belt 
in that region. 
In accordance with a further feature of the invention a rake is pivoted on 
a horizontal axis which is stationary with respect to the frame, that rake 
is disposed above the welding station and at least on the inside of the 
depending continuous tubular film which is being supplied, and said rake 
is adapted to be swung out during each advancing step so that that end of 
the continuous tubular film which is provided with the bottom seam is 
separated from the welding jaws and can be moved without an obstruction 
through the succeeding cutting and clamping means. The rake is suitably 
mounted in annular grooves, which are formed in a pinch roller, and is 
pivotally movable about the axis of rotation of said roller. The pivotal 
movement of the rake may be derived from the opening movement of a 
clamping jaw which is disposed above the welding device so that the 
turning drive is simplified in structure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
An illustrative embodiment of the invention will now be explained more in 
detail with reference to the drawing. 
A frame 1 comprises side walls 2 and 3, which are indicated in FIG. 2 and 
are interconnected by a cross-beam 4, which approximately at its center 
carries a depending fixed pivot 21. A pivoted arm 5 is pivoted on said 
pivot 21 close to the cross-beam 4 and is movable between two end 
positions by a fluid-operable piston-cylinder unit 6 having a cylinder 
which is fixed to the frame by a bracket (not shown). 
It is apparent from FIG. 5 that the pivoted arm 5 is constituted by a 
bell-crank lever, which at its free end comprises a camming portion 5'. 
Adjacent to its knee, the bell-crank lever is provided with a safety 
roller 7. The functions of said parts will be described more in detail 
hereinafter. 
A vertical axle 8 is secured to the cross-beam 4 and below the pivoted arm 
5 carries a four-armed spider 9, which is adapted to be rotated by a motor 
11 and a cogged belt 10 in steps of 90.degree.. The sense of rotation of 
the spider is indicated in FIG. 2 by an arrow A. 
It is apparent from FIG. 2 that the rotary spider 9 comprises a hub-like 
carrier and four arms 9a which protrude from said hub-like carrier and 
carry brackets 12, each of which is provided with two upstanding pins 13. 
A lever 14 is pivoted on each pin 13 and at its free end constitutes a 
movable gripper jaw 15. Each of said gripper jaws 15 is biased by a spring 
16 against an abutment surface or fixed gripper jaw 17, two of which are 
provided on each bracket 12. The two confronting levers 14 of two adjacent 
arms 9a are operatively connected by a link 18 so that the two associated 
grippers 15 open and close at the same time, e.g., to grip and retain a 
sack 19. 
The gripper jaws 15 are opened by the wedge- or wedge-shaped or curved cam 
faces of the camming portion 5' of the pivoted arm 5. As the pivoted arm 5 
is pivotally moved by the extending piston rod of the fluid-operable 
piston-cylinder unit 6, the camming portion 5' forces apart 
pressure-applying rollers 20 which are mounted on the bracket 12 and 
connected to the levers 14. As a result, the grippers 15 are turned about 
the pivots 13 and are thus disengaged from the associated abutment 
surfaces 17. By means of the links 18 the grippers on adjacent brackets 12 
are disengaged at the same time. In the position shown in FIG. 2, the 
gripper units 15 which are associated with the top and right-hand edges of 
the drawing will be disengaged by an actuation of the fluid-operable 
piston-cylinder unit 6. The right-hand pair of grippers are at the 
receiving station and the top pair of grippers are at the transfer 
station. 
In order to ensure that an inadvertent starting of the motor 11 will not 
result in damage by the swung out camming portion 5', the safety roller 7 
which is mounted adjacent to the bend of the pivoted arm 5 will enter a 
cam groove 22 formed in a locking plate 23 during a pivotal movement of 
the pivoted arm in a sense to open the grippers. As that locking plate 23 
is fixed to the spider 9 by screws 24, the safety roller 7 mounted on the 
pivoted arm 5 will prevent a rotation of the spider 9 as long as the 
camming portion 5' is disposed between the rollers 20 of the bracket 12. 
When the camming portion is retracted from between the rollers 20, roller 
7 enters a central opening in plate 23 allowing spider 9 to rotate. 
It is apparent from FIG. 1 that a continuous tubular film 26 withdrawn from 
a roll 25 enters a receiving station 27 from above. The receiving station 
27 is fixedly connected to the frame 1 and is shown in more detail in FIG. 
3, from which the central axle 8 of the cooling turret is apparent as well 
as a part of the rotary spider 9. A tubular film portion 19 which has been 
provided with a bottom seam is clamped by the grippers 15 and by the 
abutment surfaces 17 of the spider but is still connected to the 
continuous tubular film 26. Above the grippers 15 and the abutment 
surfaces 17, a link 28 is provided to which a parallel motion is imparted 
by cranks and which at that end that faces the continuous tubular film 26 
carries a clamping bar 29, which cooperates with a backing bar 31 that is 
secured to a carrier 30, which is secured to the frame. In addition to the 
backing bar 31, the carrier 30 is provided with a knife-receiving groove 
32 and a welding jaw 33. To sever the sack 19 from the continuous tubular 
film 26, a knife 34 is moved into the knife-receiving groove 32. The 
welding jaw 33 cooperates with a second welding jaw 35 in order to provide 
the continuous tubular film 26 at its leading end with a bottom seam. The 
knife 34 and the welding jaw 35 are secured to a second link 36, to which 
a parallel motion is imparted by cranks. The two links 28, 36 are operated 
by fluid-operable piston-cylinder units. 
A further clamping device for clamping the continuous tubular film is 
provided above the welding jaws 33 and 35 and consists of a turning lever 
39, which carries a clamping bar 38 and is movable by a fluid-operable 
piston-cylinder unit 40. An arm which carries the roller 421 is secured to 
the turning lever 39. When the turning lever 39 is in clamping position 
the roller 41 is spaced from a camming member 43. The camming member 43 is 
connected to a lever 44, which is held against a stop 46 by a spring 45. 
The pivot of the lever lies on the axis of the pinch roller 47. The lever 
44 has a depending extension, which constitutes an abutment 48 for 
cooperation with the clamping bar 38. For unclamping the sack workpiece 
after a bottom seam has been formed and a severing cut has been performed, 
the fluid-operable piston cylinder units 37 and 40 are operated to swing 
off the links 28, 36 and 39. During that movement the roller 41 engages 
the cam surface of the camming member 43 so that the backing member 48 is 
pivotally moved in the direction indicated by the arrow C. As a result, 
the freely depending end portion of the continuous tubular film 26 is 
disengaged from the welding jaw 33 and is deflected. That deflection 
ensures that the continuous tubular film will not collide with the carrier 
when said continuous tubular film is advanced to the extent of one sack 
length by the pinch rollers 47 and 51 in the next step. 
In order to prevent also a wrapping of the continuous tubular film 26 
around the pinch rollers 47 and 51, said pinch rollers are provided with 
annular grooves 49, 50 for receiving stripping fingers 52 and 53. The 
fingers 52 are fixed to the frame. The fingers 53 are secured to the 
backing member 48 and constitute a stripping rake. 
When a sack has been gripped by the grippers in the receiving station (the 
right hand side of FIGS. 1 and 2), and has been severed from the film, the 
spider 9 is advanced by one 90.degree. step, clockwise in FIG. 2, so that 
the next pair of grippers at the right hand side can receive the 
succeeding sack which is advanced by the feed rollers then welded and 
severed from the film as described. The procedure is repeated with 
successive sacks which are released at the transfer station (the uppermost 
pair of grippers in FIG. 2) for delivering by other means to a filling 
device. It is evident that in proceeding intermittently from the receiving 
station to the transfer station, each sack passes through two cooling 
stations namely the positions of the spider at the bottom and left hand 
side of FIG. 2.