Bottom unit of a stretch wrapping machine
A bottom unit (1) of a stretch-wrapping machine for rotating pallet goods comprises a turntable (11) rotatably supported, by means of support rollers (22), on a base (10) of the bottom unit (1). To a substantial part thereof the support rollers (22) are located above the lower limiting surface (11a) of the turntable (11).
The present invention relates to a bottom unit of a stretch wrapping machine for rotating pallet goods, said bottom unit resting on a ground and comprising a turntable having a lower limiting surface and an upper limiting surface and being rotatably supported, by means of support rollers, on a base of the bottom unit, said support rollers resting on the base with peripheral portions thereof.
PRIOR ARTThere are basically two different principles for bottom units of semi-automatic stretch wrapping machines for rotating pallet goods:
The most frequent type of a bottom unit comprises a base that constitutes foundation for a number of support rollers that are mounted in two circles, an inner circle and an outer circle. Above the support rollers the circular turntable is resting, said turntable being journalled radially around a shaft extension in the centre of the turntable. The height from the floor to the upper side of the turntable is usually 75-85 mm. Via an access ramp/inclined plane the pallet goods is normally pushed up manually on the turntable by means of a fork lift. With this type of bottom unit a large force is required to manually push heavy pallets up on the turntable via the ramp. Therefore, it is extremely important that the upper side of the turntable is located as close as possible to the ground since in this connection each cm is of extreme importance as regards the force that is required to push the goods up the ramp. The ramp often has an inclination of 2.5-3° and a length of about 1,3 m, which means that the ramp requires a large space.
The different type of bottom unit is a so-called “T-table” that constitutes a circular turntable having a cut out portion that enables the fork lift to enter inside the T-table without pushing the fork lift up along a ramp. The support rollers are mounted in the lower edge of the upper portion of the T-table and roll normally against a lower sheet metal plate that abuts the ground. However, the method normally requires that the fork lift is elevated to its highest position since the fork lift is not pushed up to the table top where the pallet is placed. Also this type of table normally has a height of about 75-85 mm above the ground.
A certain jamming risk exists if somebody places his/her foot adjacent a corner of the cut out portion of the table at the wrong moment. To eliminate this jamming risk it is common to add a photocell beam in front of the T-table, said photocell sensing a foot and consequently the rotation of the table is stopped. The time of retardation of the T-table may sometimes become too long due to the fact that the friction drive against the periphery of the T-table may slip in connection with retardation and heavy load. Therefore, it is usual to have a relatively low speed of rotation in connection with this type of bottom unit. It is also difficult to locate the photocell beam to render a proper jamming protection.
A further disadvantage is that dirt and splinters etc. from the pallets easily are spread on the bottom plate and hence also on the support rollers, this inducing operational vibrations and also increased wear.
OBJECTS AND FEATURES OF THE INVENTIONA primary object of the present invention is to provide a bottom unit of a stretch wrapping machine where the table is located at the lowest possible level.
A further object of the present invention is to make it possible to use a very short access ramp.
Still an object of the present invention is that the bottom unit should be structurally simple.
At least the primary object of the present invention is realised by means of a bottom unit of the type defined above that has been given the features of the appending independent claim 1. Preferred embodiments of the invention are defined in the independent claims.
BRIEF DESCRIPTION OF THE DRAWINGSBelow an embodiment of the bottom unit of a stretch wrapping machine according to the present invention will be described, where:
The stretch wrapping machine, schematically shown in
The bottom unit 1 and the access ramp 4 are shown in
When a piece of pallet goods is to be wrapped, said piece of pallet goods is normally elevated by means of a fork lift, then manually pushed up along the ramp 4 and subsequently located in the middle of the turntable 11. Then the actual wrapping starts by starting the rotation of the turntable 11 and the pallet goods is wrapped, usually by plastic film, so-called stretch film.
The above mentioned bottom unit 1 according to the present invention has a height between the ground and the upper side of the turntable 11 that generally is about 40-65 mm lower than bottom units of stretch wrapping machines of similar type. In the above described embodiment of the bottom unit according to the present invention the upper limiting surface of the turntable 11 normally is at a distance of about 20-30 mm from the ground that the base 10 rests upon, said base 10 normally having a thickness of about 5 mm. The low level of the turntable 11 is essentially achieved by placing the support rollers 22 according to the present invention substantially above the lower side of the table 11. This will be described more in detail below. A centre bearing 14 supports the load in the area around the centre of the turntable 11 in order to eliminate deflection in this area. Also the thickness of the turntable 11 has a great importance regarding the deflection and consequently the thickness has been chosen to about 12 mm which is about 50% more than the thickness of the turntables of most of the machines of similar type.
In the centre of the part of the base 10 that supports the turntable 11 a centre spigot 23 is provided, the turntable 11 being journalled on said spigot 23. The turntable 11 is supported by the support rollers 22 and the centre bearing 14 and is rotated by means of a driving wheel 12 that is driven by means of an electric motor 13. The motor 13 with the driving wheel 12 is intended to be suspended in a rigid, essentially rectangular plate that is hinged at one end and spring loaded at the other end. Thus, the force from the spring imparts a suitable pressure of the driving wheel 12 against the periphery of the turntable 11, the driving wheel 12 being equipped with a friction material.
A photocell 19 detects a reflector 18 each time the turntable passes its zero position. For instance the signal is used to stop the table in correct position. The reflector may be moved between five different positions for different stop positions of the table 11 depending on the location of the ramp 4.
The support rollers 22 are mounted in the U-profiles 20 that are screwed on top of the table 11. The U-profiles 20 are bevelled about 30° at their ends 21 in order to allow the lower edge of the stretch film to pass over while the lower turns are wrapped on the pallet goods. The lowest film level is then about 1 cm above the bottom of the pallet.
An area 36 of the base 10, located outside the periphery of the table 11, is reinforced by several welded profiles 37 and rigidly connected to the plate 25 that constitutes base for the mast.
When goods is to be entered on the turntable 11 via the ramp 4, the turntable 11 should assume the position shown in
Feasible Modifications of the Invention
The bottom unit described above is intended for the most common pallet seizes but may also be manufactured for larger pallets and hence larger weight. The diameter of the turntable may be increased as well as the distance between the U-profiles 20 which means that a larger area of the turntable 11 is void of support between the U-profiles 20. This may however be compensated by choosing a somewhat thicker turntable. Also the support rollers 22 may be increased in number or alternatively somewhat wider support rollers are chosen that hold more roller bearings.
In the embodiment described above the support rollers 22 extend through openings in the turntable 11 and the adherent U-profile 20. However, within the scope of the present invention it is also feasible that the support rollers 22 have such a compact design that they do not extend through the upper surface 11b of the turntable 11 but are arranged in recesses on the lower side of the turntable, said recesses having a depth that is smaller than the material thickness of the turntable 11.
Instead of fastening the shaft 34 of the support roller 22 in a U-profile 20 it is however also feasible within the scope of the invention to mount a sheet metal plate having a thickness of about 5 mm on each side of the support roller 22. The sheet metal plates that then have a hole for the shaft 34 are mounted first on the shaft 34 of the support roller and then mounted from below through the holes in the turntable 11. If the sheet metal plates are somewhat wider down below the wider part constitutes a stop towards the lower limiting surface 11a of the turntable 11. In that way the U-profiles 20 are not needed. The support rollers 22 should however be protected by a strong cover.
Claims
1. Bottom unit of a stretch-wrapping machine for rotating pallet goods, said bottom-unit (1) resting on a ground and comprising a turntable (11) having a lower limiting surface (11a) and an upper limiting surface (11b) and being rotatably supported, by means of support rollers (22), on a base (10) of the bottom unit (1), said support rollers (22) resting on the base (10) with peripheral portions thereof characterised in that the supporting rollers (22) to a substantial part are located above the lower limiting surface (11a) of the turntable (11).
2. A bottom unit as claimed in claim 1 characterised in that the support rollers (22) are extending through the upper limiting surface (11b) of the turntable (11).
3. A bottom unit as claimed in claim 1 or 2 characterised in that the support rollers (22) are arranged in two groups, that the support rollers (22) in each group are oriented mainly on a straight line and that the lines are essentially parallel with each other, seen in top view of the turntable (11).
4. A bottom unit as claimed in claim 1 characterised in that U-profiles (20) are mounted on the upper limiting surface (11b) of the turntable (11) and that the U-profiles (20) constitute supports for the shafts (34) of the support rollers (22).
5. A bottom unit as claimed in claim 4 characterised in that the shaft (34) of each support roller (22) is mounted in holders (32) connected to a U-profile (20).
6. A bottom unit as claimed in claim 4 or 5 characterised in that the support rollers (22) are received in holes in the U-profiles (20).
7. A bottom unit as claimed in claim 1 characterised in that spacings (15) are mounted in the turntable (11) and that the spacings (15) are projecting from the lower limiting surface (11a) of the turntable (11).
8. A bottom unit as claimed in claim 7 characterised in that the spacings consist of plastic pieces (15).
9. A bottom unit as claimed in claim 2 characterised in that U-profiles (20) are mounted on the upper limiting surface (11b) of the turntable (11) and that the U-profiles (20) constitute supports for the shafts (34) of the support rollers (22).
10. A bottom unit as claimed in claim 9 characterised in that the shaft (34) of each support roller (22) is mounted in holders (32) connected to a U-profile (20).
11. A bottom unit as claimed in claim 9 or 10 characterised in that the support rollers (22) are received in holes in the U-profiles (20).
12. A bottom unit as claimed in claim 2 characterised in that spacings (15) are mounted in the turntable (11) and that the spacings (15) are projecting from the lower limiting surface (11a) of the turntable (11).
13. A bottom unit as claimed in claim 12 characterised in that the spacings consist of plastic pieces (15).
14. A bottom unit as claimed in claim 3 characterised in that U-profiles (20) are mounted on the upper limiting surface (11b) of the turntable (11) and that the U-profiles (20) constitute supports for the shafts (34) of the support rollers (22).
15. A bottom unit as claimed in claim 14 characterised in that the shaft (34) of each support roller (22) is mounted in holders (32) connected to a U-profile (20).
Type: Application
Filed: Apr 22, 2003
Publication Date: Jan 5, 2006
Inventor: Arvid Lindstrom (Akersberga)
Application Number: 10/512,062
International Classification: B65B 11/56 (20060101);