Web severing device and process for severing a web

A web severing device which includes a web transport means and a web lifting means so that a transported web is lifted away from the surface of the transport means for severing by a cutting means, thus, preventing damage which would occur on contact between the transport means and the cutting means.

DESCRIPTION 
TECHNICAL FIELD 
This invention relates to severing devices for webs of indefinite length 
and it is most directly related to devices for severing webs of packaging 
material when used in conjunction with package-making devices. 
BACKGROUND ART 
U.S. Pat. No. 2,665,757 discloses a severing device for cutting definite 
lengths of rubber and cord to fashion tires from a laminate of the 
materials. The device utilizes a pair of knives mounted to pierce a 
tire-building laminate and tear the laminate in opposite directions 
following the line of the tire cord in the laminate. 
U.S. Pat. No. 4,030,388 discloses a device for severing thermoplastic film 
webs in the manufacture of vacuum skin packages. That device includes a 
chain-driven pair of knives which cooperate to make initial and final cuts 
to sever a web. The web to be severed is not moved out of its plane of 
transport prior to severing and must not have elements of support or 
transport in the path of severing. 
SUMMARY OF THE INVENTION 
According to this invention, there is provided a web severing device which 
includes a web transporting means, a web lifting means, and a web cutting 
means. The web lifting means is located to move a web to be severed apart 
and away from the web transporting means and to make the web taut for 
meeting the web cutting means. The web lifting means permits severing a 
web without damage to the web transporting means. 
Additionally, there is provided a web edge clamping means which causes the 
edge of the web to be severed to be held between the clamping means and 
the top or lifting edge of the lifting means when the lifting means is in 
the lifting mode. The clamping means is mounted in a relation to the 
lifting means to interfere with and contact the lifting edge such that the 
edge of the web is firmly held.

In FIG. 1, web transport means 10 is represented by a plurality of endless 
belts 11 positioned to provide a planar transport surface and carried on 
pulleys 12 and 13 supported by bars 14 and 15. Either of bars 14 and 15 
can be driven to provide power to the belts 11 for web transport. 
Web lifting means 20 is represented by web lifter 21 slidably positioned in 
web lifter guides 22 to move in a direction generally perpendicular with 
the planer transport surface. The web lifter 21 includes a plurality of 
notches 23 of a depth to contain belts 11 and also includes a groove 24 
along the length of the lifter 21 and in the edge of the lifter nearest 
the transport surface. The edge area of web lifter 21 which remains after 
cutting notches 23 and groove 24, is defined as the lifting edge 25. 
Lifting edge 25 extends transversely across the planar transport surface 
at least as far as the extremes of the web material to be severed. The web 
lifting means usually extends across the transport surface approximately 
perpendicular with the intended direction of web travel, but the web 
lifting means can be located at some other angle with the direction of web 
travel if such is desired or required. The lifting edge is located, in the 
normal mode, below the transport surface and, in the lifting mode, above 
the transport surface. 
Web cutting means 30 is represented by web cutter 31 slidably mounted in 
web cutter guide 32. The web cutter 31 is mounted to supportively slide in 
the cutter guide 32 and blade 34 on the web cutter 31 is positioned to be 
received by and to operatively slide in groove 24 of the web lifter 21 
when the lifter is in the lifting mode. 
Web clamping means 40 is represented by fixed clamping plates 41 and 42 
positioned above web lifter 21 such that when web lifter 21 is in the 
lifting mode the edge of any web on the planar transport surface of the 
web transport means 10 is clamped between the lifter 21 and the clamping 
plates 41 and 42. The clamping plates 41 and 42 are fitted with slots 43 
and 44. Slots 43 and 44 provide access for web cutter 31 to a clamped web 
edge in operation of the device. Web cutter 31 generally has a parked 
location in slot 43 beyond the expected edge of any web to be transported. 
In operation, again referring to FIG. 1, a web W (shown here in partial 
view, schematic) is introduced to the web transport means 10 and is 
transported into the severing device. Webs severed by means of the present 
device are generally of indefinite length and are severed as one step in 
some associated process, such as in a packaging process. The web to be 
severed is transported on the planar transport surface until the intended 
severing point is directly over the groove 24 in web lifter 21. Travel of 
the web is stopped; the web lifter is raised from the normal mode to the 
lifting mode, such as by a fluid-driven cylinder 26, thus lifting the web 
apart and away from the transport surface; the edge of the web is held 
between the lifting edge 25 and the clamping plates 41 and 42; the web 
cutter 31 is moved, from its parking place in slot 43, along the groove 24 
in raised web lifter 21, severing the web from the clamped edge to the 
opposite edge. 
While the web could be severed without the clamping element of this 
invention, it is preferred that lifting the web by web lifting means 20 
should also be accompanied by clamping the web at at least one edge. Such 
clamping provides a taut edge at which to commence the cut. The cycle of 
operation is completed when the web lifter is returned to its normal mode, 
the web cutter is returned to its parking place, and the severed web is 
transported away. The web cutter 31 can be moved through the cutting and 
returning operations manually or by means of mechanical devices or 
pneumatic or hydraulic cylinders, automatically or manually controlled. 
Fluid-driven cylinder 33 is shown in FIG. 1 for operating web cutter 31. 
FIGS. 2a and 2b provide more detailed understanding of the cooperation 
among web transport means, web lifting means, web cutting means, and web 
clamping means. FIG. 2a depicts the web severing device with the web 
lifter 21 of its web lifting means in the normal mode. In that mode, 
endless belts 11 (seen here in sectioned end view) provide a planar 
transport surface for the web W. The surface and the web W are beneath the 
blade 34 of web cutting means 30 (shown here midway in its return 
operation) and are beneath the clamping plate 41 (shown here fixed to a 
web lifter guide 22). Blade 34 is above groove 24 in, this, the normal 
mode. FIG. 2b depicts the web severing device with the web lifter 21 of 
its web lifting means in the lifting mode. In that mode, lifting edge 25 
of web lifter 21 is raised above the planar transport surface of the 
endless belts 11 and, thus raises web W to be held secure by clamping 
plate 41 between the clamping plate 41 and the lifting edge 25 and to be 
placed in the cutting path of blade 34 on web cutting means 30 (shown here 
midway in its cutting operation). Blade 34 is in groove 24 in, this, the 
lifting mode. 
In a more detailed representation of the web severing device, FIG. 3 
depicts a sectioned portion of the device with web lifter 21 in the 
lifting mode holding web W between web lifter 21 and clamping plate 41, 
above endless belts 11, and taut over groove 24 in the path of blade 34. 
Best Mode and Industrial Applicability 
The severing device of this invention is useful to sever a wide variety of 
web materials including paper, plastic film, and metal foils, and it is 
presently contemplated for use in packaging devices wherein severed 
sections of thermoplastic film are used in manufacture of heat-sealed 
packages. Specifically, the severing device of this invention is 
contemplated for use in conjunction with a vacuum skin packaging device 
such as that disclosed and claimed in U.S. Pat. No. 4,077,184. The film 
most often used in such packaging operations is made from an ionomeric 
copolymer of polyethylene and an ethylenically unsaturated carboxylic acid 
.