Package making – Methods – Conforming by stretching or shrinking of cover over contents
Patent
1996-01-02
1998-10-06
Moon, Daniel
Package making
Methods
Conforming by stretching or shrinking of cover over contents
53556, 53587, B65B 5300
Patent
active
058160264
DESCRIPTION:
BRIEF SUMMARY
This invention is concerned with apparatus for and a method of wrapping articles in film, and in particular for wrapping bales of silage in plastic film.
BACKGROUND TO THE INVENTION
It is common practice to wrap bales of silage in plastics film supplied in rolls. This helps to preserve the silage in the period between being cut and being used as animal fodder.
An important consideration in wrapping practice is the speed of wrapping, and it is desirable to wrap as quickly as possible while using the largest standard (i.e. readily available) width of film.
Other considerations are the ease of control and maintenance costs.
Apparatus for wrapping pallets loaded with goods are known in the art, and such apparatus commonly employs electric motors to rotate the bundle and to provide stretched plastic film via a pair of driven stretch rollers. In such apparatus it is important that the speed of rotation of the bundle relative to the speeds of rotation of the stretch rollers are accurately maintained. This prevents overrun and excessive stretching or the development of slack in the film. Excessive stretching can lead to "necking" in the film, which can result in uneven coverage of the pallet or article to be wrapped. If such apparatus were used for wrapping silage, uneven coverage could lead to spoilage.
However, electrical control systems for accurately and reliably monitoring and regulating the relative speeds of rotation of the article or bundle and the stretch rollers are expensive and difficult to maintain. These disadvantages are exacerbated when high wrapping speeds are required, when even small differences in the relative rotational speeds of the bundle and stretch rollers can lead to overrun and excessive stretching or the development of slack. In such circumstances the electrical control equipment is expensive, difficult to maintain and complicated to operate.
EP-A-0 096 635 discloses method and apparatus for wrapping palletised goods. Film from a roll is drawn around two rollers driven by two motors and prestretched by these rollers before it is applied to the load located on a turntable T driven by a third motor. Between the tensioning or stretching rollers and the load there is a resiliently-supported roller whose position is a function of the film tension. Its position is followed by a tension sensor which feeds a signal to a servo controller. The servo controller governs the speeds of one or more of the motors to ensure the film stretch is kept below the rupture elongation.
FR-A-2 639 023 discloses a film wrapping system having a turntable for the load to be wrapped, which is rotated by a motor. Film is supplied to the load from a supply roll via a roller which is driven by a second motor. For stretching the film, and instead of using a brake system, the two motors are driven such that the speed of turntable motor is always greater than film-delivery motor. The motors are electric motors, for example variable speed motors.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved apparatus for and method of wrapping articles.
It is a further object of the invention to provide a simple and reliable apparatus for and method of wrapping articles at high speeds.
The present invention provides apparatus for wrapping an article in a film (e.g. a plastics film), comprising a pair of stretch rollers for stretching the film, a film dispenser for delivering the film to the stretch rollers and means for rotating the article to take up stretched film from the stretch rollers, wherein the means for rotating the article comprises a first hydraulic motor and the stretch rollers are driven by a second hydraulic motor connected in series to the first motor to run on the exhaust from the first motor, whereby the ratio of the output of the first and second motors is fixed.
In another aspect the invention provides a method of wrapping an article in film (eg. a plastics film), comprising the stop of feeding the film from a dispenser to the article via a pair of stretch rollers while
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Engellenner Thomas J.
Grodt Thomas P.
Moon Daniel
Paradiso John
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