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.

Backσround 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.

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 step of feeding the film from a dispenser to the article via a pair of stretch rollers while rotating the article by means of a first hydraulic motor, wherein 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

f ixed .

Thus in the apparatus and method of the invention, the relative speeds of rotation of the bundle and the stretch rollers is accurately and simply maintained by employing a first hydraulic motor to drive the bundle and driving the stretch rollers with a second hydraulic motor coupled in series with the first motor to run on the exhaust of the hydraulic motor. In this way the rotation of the bundle and the stretch rollers are effectively coupled so that the ratio of the output of the first and second motors is fixed.

Brief Description of the Drawings An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which:

Fig. 1 is a diagrammatic plan view of apparatus according to the present invention for wrapping a bale of silage in plastics film, and

Fig. 2 is a circuit diagram showing the arrangement of the hydraulic motors as used in the apparatus of the present invention.

Detailed Description of the Invention Referring to Figs. 1 and 2, a bale of silage 14 is mounted on a turntable (not shown) driven by motor 20. The turntable may be driven at up to speeds of 100 r.p.m., though speeds of 60 r.p. . are normally preferred.

The turntable may have a pair of rollers rotatable about their longitudinal axes so that the bale 14 can be rotated about the turntable axis and simultaneously about its own axis on the turntable rollers.

A film dispenser 2 feeds a roll of film 4 to rollers 6,8 and 12. Rollers 6 and 8 are nipped, and roller 6 is driven by a hydraulic motor 22. Rollers 6 and 8 are geared to run at the same peripheral velocity, and together act to isolate the dispenser 2 from fluctuations in tension in the film arising from variations in the shape of the bale 14.

Rollers 8 and 12 act together as stretch rollers, roller 12 running faster than roller 8 (e.g. 55% to 70% faster) . The film 10 passing between rollers 8 and 12 is therefore stretched.

The film is taken up by the bale 14 in the stretched state, and to maintain the film in the stretched state after it leaves the roller 12 a biased jockey (not shown) may be incorporated to maintain the tension in the film 16 passing between roller 12 and bale 14.

The turntable motor 20 and the stretch roller motor 22 are coupled in series by hydraulic hosing 30. The hosing is preferably 0.5 or 0.75 inch (12.7 or 19 mm) bore. Oil is introduced under pressure at the inlet 26 and is returned via the return at 28. The hose is preferably capable of withstanding oil pressures of up to 3000 psi (207 bar) .

The coupling between the motors is regulated by a flow control valve 24, which draws off part of the exhaust oil leaving motor 20. Adjustment of the flow control valve 24 permits coupling of the outputs of motors 20 and 22 such that they are effectively coupled.

The circuit may incorporate valves. The valves may act simply as safety valves to prevent overpressure of the motors, but may also be arranged to permit operation of the motors in reverse direction. Such an arrangement may be useful where it is desired to reverse the direction of

the turntable. Such reversal may be required after wrapping is completed when the bales can be oriented in a particular way to allow removal from the turntable or automatic ejection e.g. by a turntable tilting mechanism.

Industrial Applicability

The invention is applicable to the wrapping of objects with a stretched wrapping film, more particularly to the wrapping of agricultural products. The invention is especially suited for the wrapping of bundles of silage.