U.S. patent number RE37,237 [Application Number 09/185,664] was granted by the patent office on 2001-06-26 for stretch wrapping with film severing.
This patent grant is currently assigned to Lantech, Inc.. Invention is credited to Yoram Gordon, Jeff Harrison, Patrick R. Lancaster, III.
United States Patent |
RE37,237 |
Lancaster, III , et
al. |
June 26, 2001 |
**Please see images for:
( Certificate of Correction ) ** |
Stretch wrapping with film severing
Abstract
A load of stretch wrap with a sheet of stretch wrap packaging
material by feeding a sheet through a stretch wrap dispenser and
stretching and dispensing from the dispenser, and providing
relative rotation between the dispenser and the load to wrap the
stretched sheet around the load. The portion of the sheet is
weakened with a sheet weakening device, and sheet is tensioned to
break the sheet at the weakened portion.
Inventors: |
Lancaster, III; Patrick R.
(Louisville, KY), Gordon; Yoram (Portland, OR), Harrison;
Jeff (Lagrange, KY) |
Assignee: |
Lantech, Inc. (Louisville,
KY)
|
Family
ID: |
22770673 |
Appl.
No.: |
09/185,664 |
Filed: |
November 4, 1998 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
207467 |
Mar 8, 1994 |
05572850 |
Nov 12, 1996 |
|
|
Current U.S.
Class: |
53/399; 53/389.3;
53/441; 53/556; 53/587 |
Current CPC
Class: |
B65B
11/045 (20130101) |
Current International
Class: |
B65B
11/02 (20060101); B65B 11/04 (20060101); B65B
013/04 (); B65B 041/12 (); B65B 053/00 () |
Field of
Search: |
;53/399,441,556,587,588,389.3 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
038622 |
|
Oct 1981 |
|
EP |
|
2097356 |
|
Nov 1982 |
|
GB |
|
WO94/22718 |
|
Oct 1994 |
|
WO |
|
Primary Examiner: Gerrity; Stephen F.
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
Claims
What is claimed is:
1. A process for stretch wrapping a load with a sheet of stretch
wrap packaging material comprising:
feeding a sheet of stretch wrap packaging material through a
stretch wrap dispenser having a prestretch portion, prestretching
the sheet of stretch wrap packaging material in the prestretching
portion, and dispensing the sheet from the dispenser;
providing relative rotation between the dispenser and the load to
wrap the stretched sheet of stretch wrap packaging material around
the load;
weakening a portion of the sheet of stretch wrap packaging material
at a predetermined location downstream of the prestretching portion
by puncturing the sheet of stretch wrap packaging material at the
predetermined location during the relative rotation between the
dispenser and the load after prestretching the sheet of stretch
wrap packaging material; and
tensioning the weakened punctured sheet of stretch wrap packaging
material during the relative rotation between the dispenser and the
load to break the sheet of stretch wrap packaging material at the
weakened punctured portion due to the relative rotation between the
dispenser and the load.
2. The process of claim 1, wherein the tensioning step includes
reducing the rate of feeding the sheet through the stretch wrap
dispenser.
3. The process of claim 1, including the step of transporting the
weakened portion to a position sufficiently downstream of the
stretch wrap dispenser to allow a graspable tail of the sheet to
extend downstream of the stretch wrap dispenser after the sheet is
broken at the weakened portion.
4. The process of claim 1, including the step of transporting the
weakened portion of the sheet to a position sufficiently downstream
of the prestretching portion to allow a graspable tail of the sheet
to extend downstream of the prestretching portion after the sheet
is broken at the weakened portion.
5. The process of claim 1, wherein the stretch wrap dispenser
includes a final dispensing roller and including the step of
transporting the weakened portion of the sheet to a position
sufficiently downstream of the final dispensing roller to allow a
graspable tail of the sheet to extend downstream of the final
dispensing roller after the sheet is broken at the weakened
portion.
6. The process of claim 1 wherein the stretch wrap dispenser
includes a final dispensing roller and the weakening step includes
weakening the film at a predetermined location upstream of the
final dispensing roller and including the step of transporting the
weakened portion of the sheet to a position sufficiently downstream
of the final dispensing roller to allow a graspable tail of the
sheet to extend downstream of the final dispensing roller after the
sheet is broken at the weakened portion.
7. The process of claim 1, wherein the weakening step includes
puncturing the sheet in a plurality of places across the sheet.
8. The process of claim 1, wherein the weakening step includes
electronically controlling the activation of a sheet weakening
tool.
9. The process of claim 1 wherein the weakening step occurs in
response to an actuation signal.
10. An apparatus for stretch wrapping a load with a sheet of
stretch wrap packaging material comprising:
a stretch wrap dispenser for feeding and dispensing a sheet of
stretch wrap packaging material from the dispenser, the stretch
wrap dispenser having a prestretching portion for prestretching the
sheet of stretch wrap packaging material;
means for providing relative rotation between the dispenser and the
load to wrap the stretched sheet of stretch wrap packaging material
around the load;
a sheet weakening device for selectively weakening a portion of the
sheet of stretch wrap packaging material at a predetermined
location downstream of the prestretching portion by puncturing the
sheet of stretch wrap packaging material at the predetermined
location during the relative rotation between the dispenser and the
load after prestretching the sheet of stretch wrap packaging
material; and
a controller for tensioning the punctured sheet of stretch wrap
packaging material during the relative rotation between the
dispenser and the load to break the sheet of stretch wrap packaging
material at the weakened punctured portion due to the relative
rotation between the dispenser and the load.
11. The apparatus of claim 10, wherein the controller tensions the
sheet by reducing the rate of feeding the sheet through the stretch
wrap dispenser.
12. The apparatus of claim 10, wherein the controller permits the
weakened portion of the sheet to be transported to a position
sufficiently downstream of the stretch wrap dispenser to allow a
graspable tail of the sheet to extend downstream of the stretch
wrap dispenser after the sheet is broken at the weakened
portion.
13. The apparatus of claim 10, wherein the controller permits the
weakened portion of the sheet to be transported to a position
sufficiently downstream of the prestretching portion to allow a
graspable tail of the sheet to extend downstream of the
prestretching portion after the sheet is broken at the weakened
portion.
14. The apparatus of claim 10, wherein the stretch wrap dispenser
includes a final dispensing roller and wherein the controller
permits the weakened portion of the sheet to be transported to a
position sufficiently downstream of the final dispensing roller to
allow a graspable tail of sheet to extend downstream of the final
dispensing roller after the sheet is broken at the weakened
portion.
15. The apparatus of claim 10, wherein the stretch wrap dispenser
includes a final dispensing roller, the sheet weakening device is
located upstream of the final dispensing roller, and the controller
permits the weakened portion of the sheet to be transported to a
position sufficiently downstream of the final dispensing roller to
allow a graspable tail of the sheet to extend downstream of the
final dispensing roller after the sheet is broken at the weakened
portion.
16. The apparatus of claim 10, wherein the sheet weakening device
includes a plurality of puncturing devices for puncturing the sheet
in a plurality of places across the sheet.
17. The apparatus of claim 10, wherein the controller
electronically controls the activation of the sheet weakening
device.
18. The apparatus of claim 10, wherein the controller
electronically controls the activation of the sheet weakening
device in response to an actuation signal.
19. A process for stretch wrapping a load and having at least one
corner with a sheet of stretch wrap packaging material
comprising:
feeding a sheet of stretch wrap packaging material through a
stretch wrap dispenser having a prestretching portion,
prestretching the sheet of stretch wrap packaging material in the
prestretching portion, and dispensing the sheet from the
dispenser;
providing relative rotation between the dispenser and the load to
wrap the stretched sheet of stretch wrap packaging material around
the load;
weakening a portion of the sheet of stretch wrap packaging material
at a predetermined location downstream of the prestretching portion
by puncturing the sheet of stretch wrap packaging material at the
predetermined location during the relative rotation between the
dispenser and the load after prestretching the sheet of stretch
wrap packaging material; and
tensioning the weakened punctured sheet of stretch wrap packaging
material during the relative rotation between the dispenser and the
load to break the sheet of stretch wrap packaging material at the
weakened punctured portion thereby creating a tail extending from
the .[.load.]. .Iadd.dispenser.Iaddend..
20. The process of claim 19, wherein the tensioning step includes
reducing the rate of feeding the sheet through the stretch wrap
dispenser.
21. The process of claim 19, including the step of transporting the
weakened portion to a position sufficiently downstream of the
stretch wrap dispenser to allow a graspable tail of the sheet to
extend downstream of the stretch wrap dispenser after the sheet is
broken at the weakened portion.
22. An apparatus for stretch wrapping a load having at least one
corner with a sheet of stretch wrap packaging material
comprising:
a stretch wrap dispenser for feeding and dispensing a sheet of
stretch wrap packaging material from the dispenser, the stretch
wrap dispenser having a prestretching portion for prestretching the
sheet of stretch wrap packaging material;
means for providing relative rotation between the dispenser and the
load to wrap the stretched sheet of stretch wrap packaging material
around the load;
a sheet weakening device for selectively weakening a portion of the
sheet of stretch wrap packaging material at a predetermined
location downstream of the prestretching portion by puncturing the
sheet of stretch wrap packaging material at the predetermined
location during the relative rotation between the dispenser and the
load after prestretching the sheet of stretch wrap packaging
material; and
a controller for tensioning the punctured sheet of stretch wrap
packaging material during the relative rotation between the
dispenser and the load to break the sheet of stretch wrap packaging
material at the weakened punctured portion thereby creating a tail
extending from the .[.load.]. .Iadd.dispenser.Iaddend., thereby
minimizing the length of the tail extending from the load.
23. The apparatus of claim 22, wherein the controller tensions the
sheet by reducing the rate of feeding the sheet through the stretch
wrap dispenser.
24. The apparatus of claim 22, wherein the controller permits the
weakened portion of the sheet to be transported to a position
sufficiently downstream of the stretch wrap dispenser to allow a
graspable tail of the sheet to extend downstream of the stretch
wrap dispenser after the sheet is broken at the weakened
portion..Iadd.
25. A rotary stretch wrapping process for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
feeding a sheet of stretch wrap packaging material through a
stretch wrap dispenser and dispensing the sheet from the
dispenser;
providing relative rotation between the dispenser and the load to
wrap the stretched sheet of stretch wrap packaging material around
the load;
prestretching the sheet of stretch wrap packaging material in a
prestretching portion of the dispenser;
weakening a portion of the sheet of stretch wrap packaging material
at a predetermined location downstream of the prestretching portion
by puncturing the sheet of stretch wrap packaging material during
the relative rotation between the dispenser and the load; and
tensioning the weakened sheet of stretch wrap packaging material to
break the sheet of stretch wrap packaging material at the weakened
portion..Iaddend..Iadd.
26. A rotary stretch wrapping process for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
feeding a sheet of stretch wrap packaging material through a
stretch wrap dispenser and dispensing the sheet from the
dispenser;
providing relative rotation between the dispenser and the load to
wrap the stretched sheet of stretch wrap packaging material around
the load;
prestretching the sheet of stretch wrap packaging material in a
prestretch portion of the dispenser;
weakening a portion of the sheet of stretch wrap packaging material
at a predetermined location downstream of the prestretching portion
by puncturing the sheet of stretch wrap packaging material during
the relative rotation between the dispenser and the load; and
tensioning the weakened sheet of stretch wrap packaging material
during relative movement between the dispenser and the load to
break the sheet of stretch wrap packaging material at the weakened
portion due to the relative movement..Iaddend..Iadd.
27. A rotary stretch wrapping process for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
initiating the wrapping of each load by feeding a sheet of stretch
wrap packaging material through a stretch wrap dispenser, attaching
a leading end of the sheet of stretch wrap packaging material to
the load to be wrapped or a support near the load to be wrapped,
and dispensing the sheet from the dispenser;
providing relative rotation between the dispenser and the load to
wrap the stretched sheet of stretch wrap packaging material around
the load;
prestretching the sheet of stretch wrap packaging material in a
prestretching portion of the dispenser;
weakening a portion of the sheet of stretch wrap packaging material
at a predetermined location downstream of the prestretching portion
by puncturing the sheet of stretch wrap packaging material during
the relative rotation; and
tensioning the weakened sheet of stretch wrap packaging material
between the dispenser and the load to break the sheet of stretch
wrap packaging material at the weakened portion..Iaddend..Iadd.
28. A rotary stretch wrapping process for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
feeding a sheet of stretch wrap packaging material through a
stretch wrap dispenser and dispensing the sheet from the
dispenser;
providing relative rotation between the dispenser and the load to
wrap the stretched sheet of stretch wrap packaging material around
the load;
prestretching the sheet of stretch wrap packaging material in a
prestretching portion of the dispenser;
weakening a portion of the sheet of stretch wrap packaging material
at a predetermined location downstream of the prestretching portion
by puncturing the sheet of stretch wrap packaging material during
the relative rotation; and
transporting the weakened portion of the sheet of stretch wrap
material downstream of the predetermined location; and
tensioning the weakened sheet of stretch wrap packaging material to
break the sheet of stretch wrap packaging material at the weakened
portion..Iaddend..Iadd.
29. A rotary stretch wrapping process for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
feeding a sheet of stretch wrap packaging material through a
stretch wrap dispenser and dispensing the sheet from the
dispenser;
providing relative rotation between the dispenser and the load to
wrap the stretched sheet of stretch wrap packaging material around
the load;
prestretching the sheet of stretch wrap packaging material in a
prestretching portion of the dispenser;
weakening a portion of the sheet of stretch wrap packaging material
at a predetermined location downstream of the prestretching portion
by puncturing the sheet of stretch wrap packaging material during
the relative rotation between the dispenser and the load; and
tensioning the weakened sheet of stretch wrap packaging material
during relative movement between the dispenser and the load to
break the sheet of stretch wrap packaging material at the weakened
portion due to the relative movement..Iaddend..Iadd.
30. A rotary stretch wrapping process for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
feeding a sheet of stretch wrap packaging material through a
stretch wrap dispenser and dispensing the sheet from the
dispenser;
providing relative rotation between the dispenser and the load to
wrap the stretched sheet of stretch wrap packaging material around
the load;
prestretching the sheet of stretch wrap packaging material in a
prestretching portion of the dispenser;
weakening a portion of the sheet of stretch wrap packaging material
at a predetermined location downstream of the prestretching portion
by puncturing the sheet of stretch wrap packaging material during
the relative rotation and after wrapping the stretched sheet of
stretch wrap packaging material around the load;
transporting the weakened portion of the sheet of stretch wrap
material downstream of the predetermined location; and
tensioning the weakened sheet of stretch wrap packaging material to
break the sheet of stretch wrap packaging material at the weakened
portion..Iaddend..Iadd.
31. A rotary stretch wrapping apparatus for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
a stretch wrap dispenser for feeding and dispensing a sheet of
stretch wrap packaging material from the dispenser;
means for providing relative rotation between the dispenser and the
load to wrap the stretched sheet of stretch wrap packaging material
around the load;
a prestretch portion of the dispenser for prestretching the sheet
of stretch wrap packaging material;
a sheet weakening device for selectively weakening a portion of the
sheet of stretch wrap packaging material at a predetermined
location downstream of the prestretching portion by puncturing the
sheet of stretch wrap packaging material during the relative
rotation; and
a controller for permitting tensioning of the sheet of stretch wrap
packaging material to break the sheet of stretch wrap packaging
material at the weakened portion..Iaddend..Iadd.
32. A rotary stretch wrapping apparatus for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
a stretch wrap dispenser for feeding and dispensing a sheet of
stretch wrap packaging material from the dispenser;
means for providing relative rotation between the dispenser and the
load to wrap the stretched sheet of stretch wrap packaging material
around the load;
a prestretch portion of the dispenser for prestretching the sheet
of stretch wrap packaging material;
a sheet weakening device for selectively weakening a portion of the
sheet of stretch wrap packaging material at a predetermined
location downstream of the prestretching portion by puncturing the
sheet of stretch wrap packaging material during the relative
rotation; and
a controller for permitting tensioning of the sheet of stretch wrap
packaging material so that the sheet of stretch wrap packaging
material can be broken at the weakened portion during relative
movement between the dispenser and the load..Iaddend..Iadd.
33. A rotary stretch wrapping apparatus for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
a stretch wrap dispenser for feeding and dispensing a sheet of
stretch wrap packaging material from the dispenser;
means for providing relative rotation between the dispenser and the
load to wrap the sheet of stretch wrap packaging material around
the load;
a prestretch portion of the dispenser for prestretching the sheet
of stretch wrap packaging material;
a sheet weakening device for selectively weakening a portion of the
sheet of stretch wrap packaging material at a predetermined
location downstream of the prestretching portion by puncturing the
sheet of stretch wrap packaging material during the relative
rotation; and
a controller for operating the rotary stretch wrapping apparatus in
a semi-automatic mode to initiate wrapping subsequent to attaching
a leading end of the sheet of stretch wrap packaging material to
the load or a support near the load prior to wrapping each load,
and for permitting tensioning of the sheet of stretch wrap
packaging material between the dispenser and the load to break the
sheet of stretch wrap packaging material at the weakened
portion..Iaddend..Iadd.
34. A rotary stretch wrapping apparatus for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
a stretch wrap dispenser for feeding and dispensing a sheet of
stretch wrap packaging material from the dispenser;
means for providing relative rotation between the dispenser and the
load to wrap the stretched sheet of stretch wrap packaging material
around the load;
a prestretch portion of the dispenser for prestretching the sheet
of stretch wrap packaging material;
a sheet weakening device for selectively weakening a portion of the
sheet of stretch wrap packaging material at a predetermined
location downstream of the prestretching portion by puncturing the
sheet of stretch wrap packaging material during the relative
rotation; and
a controller for permitting tensioning of the weakened sheet of
stretch wrap packaging material between the dispenser and the load
to break the sheet of stretch wrap packaging material at the
weakened portion thereby creating a graspable tail of packaging
material extending from the dispenser..Iaddend..Iadd.
35. A rotary stretch wrapping apparatus for stretch wrapping a load
having at least one corner with a sheet of stretch wrap packaging
material comprising:
a stretch wrap dispenser for feeding and dispensing a sheet of
stretch wrap packaging material from the dispenser;
means for providing relative rotation between the dispenser and the
load to wrap the stretched sheet of stretch wrap packaging material
around the load;
a prestretch portion of the dispenser for prestretching the sheet
of stretch wrap packaging material;
a sheet weakening device for selectively weakening a portion of the
sheet of stretch wrap packaging material at a predetermined
location downstream of the prestretching portion by puncturing the
sheet of stretch wrap packaging material during the relative
rotation; and
a controller for permitting tensioning of the weakened portion of
stretch wrap packaging material downstream of the predetermined
location and for permitting tensioning of the weakened sheet of
stretch wrap packaging material to break the sheet of stretch wrap
packaging material at the weakened portion..Iaddend..Iadd.
36. A rotary stretch wrapping apparatus for stretch wrapping a load
having at least one corner with a sheet of stretch wrap packaging
material comprising:
a stretch wrap dispenser for feeding and dispensing a sheet of
stretch wrap packaging material from the dispenser;
means for providing relative rotation between the dispenser and the
load to wrap the stretched sheet of stretch wrap packaging material
around the load;
a prestretch portion of the dispenser for prestretching the sheet
of stretch wrap packaging material;
a sheet weakening device for selectively weakening a portion of the
sheet of stretch wrap packaging material at a predetermined
location downstream of the prestretching portion by puncturing the
sheet of stretch wrap packaging material during the relative
rotation and after wrapping the stretched sheet of stretch wrap
packaging material around the load; and
a controller for permitting transporting of the weakened portion of
stretch wrap packaging material downstream of the predetermined
location and for permitting tensioning of the weakened sheet of
stretch wrap packaging material to break the sheet of stretch wrap
packaging material at the weakened portion..Iaddend..Iadd.
37. A rotary stretch wrapping process for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
feeding a sheet of stretch wrap packaging material through a
stretch wrap dispenser having a prestretch portion, prestretching
the sheet of stretch wrap packaging material in the prestretch
portion, and dispensing the sheet from the dispenser;
providing relative rotation between the dispenser and the load to
wrap the stretched sheet of stretch wrap packaging material around
the load;
weakening a portion of the sheet of stretch wrap packaging material
at a predetermined location downstream of the prestretching portion
by puncturing the sheet of stretch wrap packaging material at the
predetermined location during the relative rotation between the
dispenser and the load and after prestretching the sheet of stretch
wrap packaging material; and
tensioning the weakened punctured sheet of stretch wrap packaging
material to break the sheet of stretch wrap packaging material at
the weakened punctured portion..Iaddend..Iadd.
38. A rotary stretch wrapping process for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
feeding a sheet of stretch wrap packaging material through a
stretch wrap dispenser having a prestretch portion, prestretching
the sheet of stretch wrap packaging material in the prestretch
portion, and dispensing the sheet from the dispenser;
providing relative rotation between the dispenser and the load to
wrap the stretched sheet of stretch wrap packaging material around
the load;
weakening a portion of the sheet of stretch wrap packaging material
at a predetermined location downstream of the prestretching portion
by puncturing the sheet of stretch wrap packaging material at the
predetermined location during the relative rotation between the
dispenser and the load; and
tensioning the weakened punctured sheet of stretch wrap packaging
material to break the sheet of stretch wrap packaging material at
the weakened punctured portion..Iaddend..Iadd.
39. A rotary stretch wrapping apparatus for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
a stretch wrap dispenser for feeding and dispensing a sheet of
stretch wrap packaging material from the dispenser, the stretch
wrap dispenser having a prestretching portion for prestretching the
sheet of stretch wrap packaging material;
means for providing relative rotation between the dispenser and the
load to wrap the stretched sheet of stretch wrap packaging material
around the load;
a sheet weakening device for selectively weakening a portion of the
sheet of stretch wrap packaging material at a predetermined
location downstream of the prestretching portion by puncturing the
sheet of stretch wrap packaging material at the predetermined
location during the relative rotation between the dispenser and the
load after prestretching the sheet of stretch wrap packaging
material; and
a controller for permitting tensioning of the sheet of stretch wrap
packaging material to break the sheet of stretch wrap packaging
material can be broken at the weakened punctured
portion..Iaddend..Iadd.
40. A rotary stretch wrapping apparatus for stretch wrapping a load
with a sheet of stretch wrap packaging material comprising:
a stretch wrap dispenser for feeding the dispensing a sheet of
stretch wrap packaging material from the dispenser, the stretch
wrap dispenser having a prestretching portion for prestretching the
sheet of stretch wrap packaging material;
means for providing relative rotation between the dispenser and the
load to wrap the stretched sheet of stretch wrap packaging material
around the load;
a sheet weakening device for selectively weakening a portion of the
sheet of stretch wrap packaging material at a predetermined
location downstream of the prestretching portion by puncturing the
sheet of stretch wrap packaging material at the predetermined
location during the relative rotation between the dispenser and the
load; and
a controller for permitting tensioning of the sheet of stretch wrap
packaging material to break the sheet of stretch wrap packaging
material can be broken at the weakened punctured portion..Iaddend.
Description
BACKGROUND OF THE INVENTION
The invention relates to a stretch wrapping operation in which the
stretch wrap film is severed after a load is wrapped.
Stretch wrapping processes which are performed on a semiautomatic
basis have required an operator to sever the film and secure the
trailing end of the film onto the load after the sheet of film web
has been wrapped around the load. This generally required the
operator to dismount from a forklift truck to perform this
operation manually and then remount the forklift truck to remove
the load. In some instances, the operator would cut the film with a
knife. In other instances, the operator would stick his or her
finger through a portion of the film and grasp the film behind that
portion to sever the film.
Automated attempts to sever the film have only been effective after
the wrapping process has ended and the film is in a relatively
stationary position. Such film cutting is typically accomplished
with an exposed hot wire which is passed through the film web
across its full width. The hot wire is located well outside the
roll carriage which forms the stretch wrap dispenser. The exposed
hot wire can be hazardous to a careless operator. Also, this
approach leaves a very short tail of film web extending from the
stretch wrap dispenser which may cause difficulties in having the
operator grasp and pull the film web out of the stretch wrap
dispenser and attach it to the next load for the next wrapping
cycle.
Attempts have been made to snap the film by stopping the film drive
motor. These attempts resulted in unreliable and unpredictable
situations in which the film broke at undesirable or unpredictable
locations within the stretch wrap dispenser, thereby requiring the
film to be at least partially pre-threaded.
SUMMARY OF THE INVENTION
According to the invention, a process and apparatus is provided for
stretch wrapping a load with a sheet of stretch wrap packaging
material. The process involves feeding a sheet through a stretch
wrap dispenser and stretching and dispensing the sheet from the
dispenser. Relative rotation is provided between the dispenser and
the load to wrap the stretch sheet around the load. A portion of
the sheet is weakened and the sheet is tensioned to break the sheet
at the weakened portion. It is preferable that the weakened portion
of the sheet is transported to a position sufficiently downstream
of the dispenser to allow a graspable tail of the sheet to extend
downstream of the dispenser after the sheet has broken at the
weakened portion.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute
part of the specification, illustrate a presently preferred
embodiment of the invention and, together with the general
description given above and the detailed description of the
preferred embodiment given below, serve to explain the principles
of the invention.
FIG. 1 is a perspective view of an example of a stretch wrapping
apparatus which includes the teachings of the present
invention.
FIG. 2 is a perspective view of the stretch wrapping apparatus of
FIG. 1 showing an example of the interior of the stretch wrap
dispenser.
FIG. 3 is an enlarged view of a portion of FIG. 2.
FIG. 4 is a view of the arrangement shown in FIG. 3 at a later
point in time.
FIG. 5 is a perspective view of the arrangement shown in FIG. 2
from a different angle and at a later period of time than that
shown in FIG. 4.
FIG. 6 is a perspective view of the arrangement shown in FIG. 5 at
a period of time later than that shown in FIG. 5.
FIG. 7 is a block control diagram.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Reference will now be made in detail to the present preferred
embodiment of the invention as illustrated in the accompanying
drawings.
As shown in FIG. 1, a stretch wrapping apparatus 30 is provided for
stretch wrapping a load 32 with a sheet 34 of stretch wrap
packaging material dispensed from a stretch wrap dispenser 38. The
stretch wrap dispenser 38 includes a roll carriage having a frame
39 and rollers for feeding and dispensing sheet 34 of film web onto
load 32 from film roll 36. As shown in FIG. 2, the roll carriage
preferably includes a prestretch portion 40, a support for film
roll 36, and dispensing rollers 48 and 50 which are positioned
downstream of prestretching portion 40. The roll carriage may
include commercially available hinged subassemblies as shown in
U.S. patent application Ser. No. 07/611,114, now abandoned which is
incorporated herein by reference.
Prestretching portion 40 preferably includes prestretch rollers 42
and 46 and intermediate idler roller 44. Downstream prestretch
roller 46 is driven at a faster speed than upstream prestretch
roller 42 to prestretch film web 34 in stretch wrap dispenser 38
between prestretch rollers 42 and 46, before dispensing film web 34
from dispenser 38. The relative speed of upstream and downstream
prestretch rollers 42 and 46 is preferably provided by a chain and
sprocket drive 52 which connects the shafts of those rollers. The
surface speed of the rollers, is controlled by a controller 72
which controls the speed and/or actuation of a motor and brake
arrangement 54 which is connected to the shafts of prestretch
rollers 42 and 46 by a chain and sprocket or belts. A suitable
example of a prestretch device is shown and described in greater
detail in U.S. patent application Ser. No. 08/051,416 now U.S. Pat.
No. 5,414,979, and U.S. Pat. No. 4,302,920, which are incorporated
herein by reference. Alternatively, the controller 72 may actuate a
brake which slows and stops the rollers that feed the film.
Relative rotation is provided between stretch wrap dispenser 38 and
load 32 to wrap the stretched sheet 34 on load 32. As shown in
FIGS. 1 and 5, the relative rotation is provided by a conventional
motor driven turntable 58 which supports and rotates the load about
a vertical axis. Alternative mechanisms for providing relative
rotation between dispenser 38 and load 32 include an arm or ring
which supports and revolves stretch wrap dispenser 38 around a
stationary load 32. Examples of these alternatives may be seen U.S.
Pat. No. 5,161,349, which is incorporated herein by reference. As
shown in FIG. 1, dispenser 38 may include a mast 41 on which the
roll carriage is automatically raised and lowered in a conventional
way to spirally wrap load 32.
As shown in FIGS. 2-4, a sheet weakening device 60 is positioned
between the two dispensing rollers 48 and 50 which are downstream
of prestretch portion 40. The sheet weakening device preferably
includes a tool such as puncturing device 62 having sharp pins 64
mounted on a U-shaped support 66 that is journalled to rotate about
the axis of dispensing roller 48. Puncturing device 62 is
electrically activated by electric solenoid 68. When solenoid 68 is
activated, the puncturing device 62 moves from the non-engaged
position shown in FIG. 3 to the position to the FIG. 4 where pins
64 engage and puncture the film web 34. The puncturing device 62 is
then retracted back to the non-engaged position. Depending on the
application, the sheet weakening device may be located at other
positions. In addition, the sheet weakening device could be
mechanically activated, such that it is cocked and released through
a camming action.
While the weakening tool preferably includes pins 64 which puncture
the sheet in a plurality of places across the sheet in positions
proximate to each edge of the sheet, other alternatives for the
weakening tool include a high friction knuckle of material such a
polyurethane. It may be possible that non-mechanical weakening
devices may be employed to perforate or weaken the sheet, such as
an electric arc perforation shown in U.S. Pat. No. 4,765,120 which
is incorporated herein by reference.
The weakening step preferably includes electronically controlling
the actuation of a weakening tool. Depending on the application,
the controller 72 can be any of a number of control devices such as
a programmable micro-controller or relay logic. The controller can
actuate the weakening tool in response to input from a proximity
switch which counts revolutions of the load relative to the film
dispenser, or a timer that can be preset by the operator. An
exemplary block control diagram is shown in FIG. 7.
The operation starts by having the operator attach the leading end
of the sheet of film web 34 to the load or a support near the load.
At that starting point, the sheet of film web 34 has already been
threaded through stretch wrap dispenser 38 so that, as shown in
FIG. 6, a graspable tail 70 of sheet 34 extends downstream of the
dispenser and, more particularly, downstream of the final
dispensing roller 50 of the dispenser. The length of the tail
should be sufficient to allow an operator to grab the tail and pull
additional sheet from the dispenser 38 to initiate the wrapping of
a new load. For current machines, the tail preferably extends at
least about one-half foot and even more preferably at least about
one foot from roller 50.
Load 32 is then wrapped with a sheet 34 of stretch wrap by
providing relative rotation between dispenser 38 and load 32. The
sheet 34 of stretch wrap is fed through stretch wrap dispenser 38,
stretched in prestretching portion 40, and dispensed after having
passed over dispensing rollers 48 and 50 which are preferably idler
roller. The sheet 34 of stretch wrap material may be fed through
the dispenser merely by the drive provided by the relative rotation
between the load and dispenser. The feeding of the sheet 34 of
stretch wrap also may be assisted by a motor 54 which drives the
prestretch rollers 42 and 46. While powered and unpowered
prestretch rollers are preferred, other alternative stretching
mechanisms, such as a brake, may be used in the stretch wrapping
operation.
During the last revolution of the wrapping process, a portion of
the sheet 34 is selectively weakened preferably at a preselected
time and preferably at a preselected position. As shown in FIG. 7,
the controller 72 is informed that the load is in the last
revolution of the wrapping cycle because proximity switch 74 counts
revolutions of turntable 58. After a preset time, set by the
operator on timer 76a, controller 72 causes film delivery drive
motor 54 to decelerate, thereby decelerating turntable 58.
When this deceleration begins, another timer 76b is triggered so
that after another preset time, which is determined by the
operator, controller 72 sends signal to the relay/solenoid 68 of
the sheet weakening device 60 so that the relay/solenoid 68 is
activated, pushing on puncturing device 62, and causing rotation of
puncturing device 62 from the position shown in FIG. 3 to the
position shown in FIG. 4. As shown, this causes pins 64 to puncture
a number of small holes through the moving film. At the same time,
another time 76c is triggered.
After a predetermined time, long enough to puncture holes of a
sufficient size in the film, controller 72 deactivates
relay/solenoid 68, retracting the puncturing device 62 back to the
position shown in FIG. 3 so that puncturing device 62 no longer
contacts the film. Up until this point in the operation, the film
delivery system, powered by film delivery drive motor 54, and
turntable 58, powered by a turntable motor 80, are normally
functioning.
After a preset time, which is determined by the operator, the timer
76c triggers a signal through controller 72 to the film delivery
drive motor 54, causing the film delivery drive motor 54 to
shut-off. This procedure causes film delivery drive motor 54 to act
as a brake on the dispensing of film, which causes extra tension on
the film because turntable 58 and the load continue to rotate and
pull on the film. This stage of the operation is shown in FIG. 5,
where the load is almost in its final wrapped position and the film
delivery drive motor 54 is being locked up so that no more film is
dispensed. The weakened film stretches and the holes get
bigger.
As the load continues to rotate, it pulls on the film that is
locked upstream in the film dispenser, stretching the film until it
tears and snaps at the points where the puncturing device 62 has
punctured a few holes and weakened the film. This final stage is
shown in FIG. 6 with the load in its final wrapped position, and a
graspable tail 70 extending downstream of the final dispensing
roller 50 of stretch wrapped dispenser 38. The sheet 34 preferably
breaks at the weakened portion when the weakened portion is in a
preselected location.
The tensioning step preferably includes reducing the rate of
feeding the sheet through the stretch wrap dispenser while
continuing to provide relative rotation between the dispenser and
the load. Other alternatives for tensioning the sheet could include
increasing the rate of relative rotation between the dispenser and
the load. If the tensioning step is accomplished by reducing the
feed rate, this can be done not only by causing motor 54 to run at
a reduced speed, but by applying a brake and/or cutting power to
the motor.
It is likely that sheet 34 will continue to be dispensed from
dispenser 38 even after the tensioning step is commenced because of
a delay in reducing the speed or stopping the rotation of the
feeding of the sheet. The relative rotation between the dispenser
and the load is terminated preferably just after the sheet
breaks.
It is currently preferable to have the film break immediately after
the last corner of a load intersects the film web, leaving almost
no film tail extending from the load. To do so, it is necessary to
accommodate precisely the changes in film prestretch, wrapping
force, film characteristics, load weight and turntable speed. These
variables can be accommodated with multiple sensing devices to
eliminate the use of time functions to determine load corner
location.
In determining the position and timing of the steps of weakening a
portion of the sheet and tensioning the sheet, it is preferable to
transport the weakened portion of the sheet to a position
downstream of the prestretch portion of the dispenser before the
sheet is tensioned sufficiently to break. It is further preferable
that the weakening step occurs downstream of the prestretching
portion. It is also preferable that the weakened portion is
transported to a position sufficiently downstream of the
prestretching portion, and even more preferably to a position
sufficiently downstream of the final dispensing roller or the
dispenser itself, to allow a graspable tail of the sheet to extend
downstream that position after the sheet is broken at the weakened
portion. By providing for such a tail, the operator of the machine
can easily grasp the leading end of the sheet 34 and pull the sheet
forward to commence the next wrapping cycle while eliminating the
difficulties of partially or fully rethreading the stretch wrap
dispenser.
Additional advantages and modifications will readily occur to those
skilled in the art. The invention in its broader aspects is,
therefore, not limited to the specific details, representative
apparatus and illustrative examples shown and described.
Accordingly, departures may be made from such details without
departing from the spirit or scope of the general inventive concept
as defined by the appended claims and the equivalents.
* * * * *