Manufacturing container or tube from paper; or other manufacturi – Control means energized in response to activator stimulated... – Responsive to work material – the product or means engaging...
Reexamination Certificate
1999-11-17
2001-11-20
Vo, Peter (Department: 3721)
Manufacturing container or tube from paper; or other manufacturi
Control means energized in response to activator stimulated...
Responsive to work material, the product or means engaging...
C493S008000, C493S013000, C493S025000, C493S034000
Reexamination Certificate
active
06319182
ABSTRACT:
FIELD OF THE INVENTION
My present invention relates to a method of and to an apparatus for positioning of a plurality of devices used in the fabrication of plastic bags or line articles from a web of material such as a synthetic resin or plastic foil, along the path of the web which can be intermittently moved so that a portion of the web for making a particular article is advanced from device to device.
The invention has general application to the positioning of manufacturing devices for performing respective operations along any web of any material but is particularly applicable to bag-making machines in which the devices perform the successive operations on a plastic web which are required to fabricate bags from the plastic foil.
BACKGROUND OF THE INVENTION
In the production of bags from a synthetic resin foil web, apart from welding devices, which can be used to separate the bags from the web and simultaneously form lateral seams on the bag which are produced, frequently other devices must be provided along the path of the web to form various seams, produce various cutouts, incise openings, or to otherwise modify the shape or character of the bag which is ultimately to be separated from the web.
Typical among such devices are the devices for forming corner welds or gussets, devices for punching or incising ventilation holes and/or hanger holes, and the like. These additional devices are spaced apart by a distance equal to the increment of advance of the web or a multiple thereof and perform their respective operations in registry with the article to be produced at each location so that the openings and seams are all properly positioned in the finished bag when it is finally separated from the web. The increment of advance of the web is usually equal to the distance corresponding to a width of the bag or between successive separation seams. That distance is also referred to as a repetition length.
However, the mounting of a plurality of devices which perform independent operations on the web on a common carriage cannot solve the problem since each device must always be exactly positioned and for the most part, with the system described, only the one device which is in the immediate vicinity of the photocell may be positioned with sufficient accuracy. In the past, therefore, one had to be satisfied with a certain degree of imprecision with respect to the other devices of the bag-making line.
OBJECTS OF THE INVENTION
It is, therefore, the principal object of the present invention to provide a method of positioning individual devices of a bag-making line or other devices operating on a web which is intermittently disclosed for such operations, whereby rapid and exact repositioning of the devices is possible for all of the devices which must perform operations in registry with one another on successive regions of the web.
It is also an object of the invention to provide an improved apparatus of the type described with the ability to accurately reposition or newly position working devices in the event of a change in the repetition length over the course of operation.
Still another object of this invention is to provide a method of and an apparatus for making plastic bags whereby drawbacks of earlier bag-making machines, especially with respect to registry of successive bag-making operations, has proved to be a problem heretofore.
It is also an object of the invention to provide for improved control and positioning of welding, punching, incising or other shaping devices in a bag-making line so as to avoid drawbacks of earlier systems.
SUMMARY OF THE INVENTION
These objects are achieved, in accordance with the invention, by automatically positioning each of the devices in its correct position in the intermediate displacement region of the path of the web upon a change in the intermediate advance and in an automatic manner. This is achieved, in accordance with the invention by providing a sensor, e.g. a photocell, for determining deviations of the actual advance of the web from a setpoint advance and utilizing a computer or comparator, generating a correction value which is applied to each of the individual devices, as multiplied by a factor representing the distance of that device from a reference point, e.g. the point at which a seaming device is selected to weld a bag seam and separate the bag from the web, and then automatically to shift the particular device in accordance with the product of that factor and the correction value.
More particularly, the method of positioning a plurality of devices for carrying out successive operations upon the web of material comprises the steps of:
(a) a plurality of the devices along a stretch of a path of the web for effecting respective operations on the web in succession;
(b) intermittently advancing the web along the stretch;
(c) detecting changes in the intermittent advance of the web; and
(d) repositioning the devices automatically along the path in response to a detected change in the advance of the web.
Preferably the web of material is a synthetic resin foil web for the making of bags and the devices are welding and punching devices for producing the bags, the web being intermittently advanced in increments corresponding to a dimension of a bag to be produced and the devices are positioned along the path at locations spaced by the dimension or a multiple thereof.
The method can further comprise the steps of:
comparing an actual value of an intermittent advance of the web with a setpoint value thereof;
computer-generating a correction value upon deviation of the compared actual value and setpoint value;
multiplying the correction value by a respective magnitude representing a distance of a respective one of the devices from a fixed reference point of the path to obtain a respective correction product; and
repositioning each of the devices from a previous position by the respective correction product depending upon the distance of the respective device from the fixed reference point.
Advantageously, the sensor includes a photocell and at least one of the devices is configured to form seams between respective bags and at least one of the devices is configured to punch holes in the web.
The apparatus in its broadest terms can comprise:
a plurality of the devices positioned at respective locations along a stretch of a path of the web for effecting respective operations on the web in succession
means for intermittently moving the web along the path past the devices;
means for detecting changes in the intermittent advance of the web; and
means for repositioning the devices automatically along the path in response to a detected change in the advance of the web.
The device can have a respective drive for shifting it along the path and that drive can include an electric motor and a displacement-measuring transducer. The positive coupling between the drive and the path can be a pinion driven by the motor and engageable with a rack positioned along the path or a threaded spindle driven by the motor and engaging a nut positioned along the path.
REFERENCES:
patent: 2321647 (1943-06-01), Brougham et al.
patent: 4604083 (1986-08-01), Barny et al.
patent: 5041070 (1991-08-01), Blaser
patent: 5470300 (1995-11-01), Terranova
patent: 5733236 (1998-03-01), De Smedt
patent: 6139479 (2000-10-01), Heiliger
patent: 6149565 (2000-11-01), Meyer et al.
Dubno Herbert
Lemo Maschinenbau GmbH
Tawfik Sam
Vo Peter
LandOfFree
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