Transfer mechanism for conveyor

A conveyor system for transporting a succession of thin flexible sheets such as plastic bags from a bag forming device to a bag stacking device. The conveyor system includes a first conveyor having vacuum holes for holding the bags in place, with portions of the bags extending beyond the conveyor's edges. The system further includes bag support apparatus such as a pair of auxiliary conveyors located alongside the first conveyor and supporting the overhanginig portions of the bags. The auxiliary conveyors terminate short of the end of the first conveyor, such that for a predetermined distance the overhanging portions of the bags are unsupported, thus permitting a bag stacking device to lift the bags and deposit them onto a stack.

BACKGROUND OF THE INVENTION 
This invention relates generally to conveyor systems, and, more 
particularly, to conveyor systems for delivering a succession of this 
flexible sheets such as plastic bags to a stacking device. 
Machines have heretofore been developed for removing discrete materials 
such as bags from a conveyor onto a stack. For example, U.S. Pat. Re 
27,523 entitled "Machine For Automatically Placing Bags on a Wicket" 
issued to L. Maccherone shows a bag transfer machine. Patent Re 27,523 
illustrates a machine for forming bags from plastic materials comprising 
continuous webs. The individual bags are made by heat-sealing and 
separating their side seams from the side seams of adjacent bags. The heat 
sealing and separating are accomplished in various ways as is well known, 
and the bags are perforated to form mounting holes for stacking purposes. 
The bags are transferred from the conveyor system and are stacked on the 
legs of a wicket. 
The machine of Patent Re 27,523 comprises a revolving carriage having 
clamping means adapted to grasp the bag and to revolve the bag over to a 
position adjacent to the wicket with the mounting holes exposed and 
positioned to engage the legs of the wicket. A conveyor adjacent to the 
revolving carriage brings the bags from the output of the production line 
to the carriage. As the carriage revolves, actuating means close the 
clamping mechanism near the conveyor for grasping the bag near the 
mounting holes with these holes exposed, and as the carriage continues to 
revolve the actuating means releases the clamping means after the bags 
have been individually engaged on the wicket. 
While the transfer mechanism disclosed in Patent Re 27,523 provides 
generally satisfactory results, the machine lacks positive control of the 
flexible units and accordingly the machine is susceptible to jamming by 
the bags. Hence, an operator has to be constantly monitoring the 
operation. 
The present invention is an improvement over the machine shown in Patent Re 
27,523. More specifically, the present invention provides complete 
continuous and positive control of the flexible units during the transfer 
operation. 
SUMMARY OF THE INVENTION 
The present invention discloses a transfer mechanism for transferring 
flexible sheet type units from a conveyor system to a stacking mechanism. 
In one embodiment, three conveyor belts positioned alongside, and adjacent, 
each other carry flexible plastic material bags. The center belt is 
perforated along the length of travel and a vacuum force is exerted 
through the perforations to retain the material in a relatively fixed 
point on the conveyor belt and as the belts move the bags are maintained 
in a fixed position relative to the belt. The center belt is longer than 
the other two belts. Pairs of fixed radially extending arms on a revolving 
member rotate upwardly, with the pairs of arms straddling the longer belt. 
The ends of the arms extend to a point slightly spaced from the end of the 
two outer belts. 
As the arms move upwardly, they engage one or more bags and lift those bags 
off of the belt and against the vacuum force holding the bags on the belt. 
The arms have a surface which is perforated by a series of holes along its 
length, and vacuum force is exerted through the perforations to hold the 
bags in a secure positive position on the arms. The pair of arms thus 
contact and lift the bags off of the belt, move the bags upwardly and 
around 180.degree. and deposit the bags on associated wicket pins. As the 
arms move downwardly, the wicket pins engage mounting holes formed on a 
portion of the bag and remove the bag from the rotating arms to a stacked 
position.

DETAILED DESCRIPTION OF THE INVENTION 
Refer first to FIGS. 1 and 2. In one production-line or system 10 for 
making plastic bags 11 and utilizing the inventive transfer mechanism 30, 
the individual bags 11 are made from continuous double web 14A and 14B of 
a pliable, flexible plastic material. Plastic material is wound on two 
feed spools 16 and 18 and the webs are drawn through suitable guides and 
feed rolls, not shown, over a roller 20 of a conveyor system 39, to be in 
overlapped portion indicated as at 21, all as is well-known in the art. 
The plastic webs 14A and 14B are shown as being transparent plastic capable 
of being heat sealed as at 22, and severed, to form the individual bags 
11. A bag forming mechanism 23 of any suitable known type or design such 
as that shown in patent Re 27,523, for example is used in the system 10. 
As is known, the side seams of the individual bags 11 may be formed by 
well-known, vertically reciprocating heat sealing bars in bag forming 
mechanism 23. The action of the heater bar forms a bag 11 and severs each 
bag 11 from the adjacent bag. Each individual bag 11 is then conveyed by 
the conveyor belt system 39 into operative relationship with the inventive 
transfer mechanism 30 as will be described in detail further below. 
Each bag 11 includes a projecting portion on a side of the webs to form a 
flap 24 on the open end of each bag. 
The bag forming mechanism 23 includes suitable perforating devices for 
forming mounting apertures or holes 25 in flap portion 24 of each bag 11, 
as is well-known. The operation of the bag forming mechanism 23 and the 
rate of feed of the webs 14A and 14B are synchronized so that the mounting 
holes 25 are accurately located in the same respective positions in each 
flap portion 24 of each bag 11. Such synchronizing control is well-known 
in the bag making art. 
The conveyor belt system 39, which forms an important part of this 
invention, comprises three belts 41, 42 and 43 positioned in side-by-side 
relation, and the belts are driven in synchronism by a motor 19 and 
indexer 19A, both of which may be of any suitable known type and design. 
As more clearly seen from FIG. 2, the center belt 41 is longer and extends 
farther than the two other belts 42 and 43 which straddle belt 41. In the 
embodiment shown, belt 41 includes a pair of continuous rows of small 
holes or perforations 45 and 46. 
Refer now also to FIG. 3 which shows an elongated belt support frame 47 
which is positioned beneath and provides support to the belts 41, 42 and 
43. The belts 41, 42 and 43 move or rotate around the frame 47. The frame 
47 includes a pair of channels 49 and 51 extending lengthwise along the 
frame The channels 49 and 51 are in alignment, or accomodate, respective 
rows of holes 45 and 46 formed in belt 41. A vacuum source 36A, of any 
suitable known type, is connected through suitable conduits to channels or 
recesses 49 and 51 to provide a vacuum force thereto. As will be 
appreciated when the belt 41 is placed around frame 47, the vacuum force 
is effective via the channels 49 and 51, and through the rows of holes 45 
and 46 formed in belt 41 to the bags 11 on the surface of belt 41. It will 
further be appreciated that the flexible plastic bags 11, or similar light 
material, will be positively or securely held in its relative position on 
belt 41 by this vacuum force. Each bag is thus securely retained in its 
relative position on belt 41 as the belt travels in a continuous movement. 
As mentioned above, at least a portion of the bags 11 extend over the side 
of belt 41. This may be done conveniently by selectively positioning the 
feed rolls 16 and 18. In the embodiment, the bags 11 are dimensioned so 
that the extremities of the bags are greater than the width of belt 41. 
The flap portion 24 of each bag 11 thus extends over and rides on the 
outer belt 42, while the lower or closed end of each bag 11 may extend 
over and ride on the outer belt 43. As mentioned above, the three belts 
are driven in synchronism. 
The inventive transfer mechanism 30 of FIG. 2 comprises a revolving axle 31 
driven by an electric motor 32 of a suitable known design. Pairs of arms 
or extensions 33 positioned in axial alignment with each other, and 
circumferentially spaced from each other extend radially outwardly from 
the axle 31. In the embodiment shown six pairs of arms 33 extend outwardly 
from the axle in equal angular spacing. The arms 33 include an internal 
elongated hollow and have a plurality of apertures or holes 34 extending 
from the hollow, along the length of the arms, and outwardly on one 
surface 35 thereof (the bag engaging surface) as will be described. A 
source of vacuum force 36B is coupled through suitable conduits or 
channeled to the hollow and holes 34. 
Note that each pair of arms 33 straddle the extended end of belt 41, and 
the ends of the arms 33 extend to a point adjacent the ends (or return 
point) of belts 42 and 43. In the embodiment shown, the arms 33 transfer 
two bags at a time. It can be readily appreciated that one or more bags 
can be tranferred at a time dependent on the size and shape of the bags. 
In FIG. 2, as the trailing edge of the second bag of a pair is moved past 
the ends of belts 42 and 43, a pair of arms 33 moves upwardly to lift the 
bag upwardly and against the vacuum force effective through the holes 45 
and 46 in belt 41, and remove the bag from the belt 41. Also since the 
arms 33 have a vacuum force effective through their holes 34, the bags 11 
are now firmly held in position on the surface 35 of arms 33, as the arms 
rotate toward a stacking location 17. In the embodiment shown, the bags 11 
are on the arms 33 for approximately 180.degree.. The bags 11 are then 
automatically positioned, or stacked, on wicket pins 15 located on a 
movable stacking mechanism 16 of any suitable known type. One or more pins 
15 on each wicket stacking position enter into the holes 25 on bags 11 to 
effectively engage or grab and remove the bags from the arms 33. 
A modification of the embodiment shown in FIG. 2 is depicted in FIG. 4. In 
the embodiment of FIG. 4, the two outer belts 42A and 43A are longer than 
the center belt 41A and the transfer mechanism 30A includes arms 35A which 
extend between the inner edges of the two outer belts. The ends of the 
arms 35A terminate at a point adjacent the end of the center belt 41A. In 
this embodiment, the outer belts 43A and 42A include the rows of apertures 
for channeling the vacuum force to the bags. The operation of the 
structure of FIG. 4 is generally similar to that of the structure of FIG. 
2. 
A modification to the structure of FIG. 2 for certain applications is as 
follows. In FIG. 2, a smooth flat stationary surface is provided in lieu 
of moving belts 42 and 43. In FIG. 4, a smooth flat stationary surface is 
provided in lieu of moving belt 41A. The foregoing modification could be 
used where the bags are made of relatively stiffer, and less flexible 
material. 
While the invention has been particularly shown and described with 
reference to a preferred embodiment thereof, it will be understood by 
those skilled in the art, that various changes in form and details may be 
made therein without departing from the spirit and scope of the invention.