TOOL AND METHOD OF MANUFACTURING SAME

TOOL AND METHOD OF MANUFACTURING SAME

The invention concerns a tool and a method for the manufacture of the tool.

From US Patent No. 4,655,494 there is known a type of shovel comprising a short blade manufactured in a suitable plastic material, and where the shaft itself is made of wood. A shovel of this type is not suitable for use where great demands are placed with regard to hygiene, for example within the foodstuffs industry, in that the wood will provide a basis for bacterial growth, and also in that the joint between wood and shovel blade will be an area in which many bacteria can collect. Moreover, the shaft is not ergo- nomic in shape, in that this is made completely straight.

From Danish Utility Model publication No. 94 00347, there is known a tool with a tubular shaft, and where the actual assembly between the shaft and handle is effected by means of a pin connection. Consequently, also in this case the connection between handle and shaft will give rise to bacterial collections, and for this reason such an assembly must be said to be unsuitable in areas in which great demands are placed regarding hygiene.

Finally, it is known to manufacture tools, for example shovels, made of a plastic material and where these are thus moulded. However, the disadvantage of these is firstly that it is not possible to change the geometry of the product when this has once been moulded, i.e. unless a decided change is made in the mould, and secondly that the shaft is over-dimensioned in order to provide a stiffness which is sufficient to enable the tool to be used for heavier and more unmanageable products.

It is the object of the invention to provide a tool which does not suffer the disadvantages of the existing tools, and where there is provided a type of tool which has a surface with a hygiene level which makes it possible to use the tool within the foodstuffs industry. Particularly in connection with the use of shovels, stirrers and handles within the foodstuffs industry, great demands are made regarding hygiene. Moreover, it is also desirable at the same time that the tool has a great rigidity combined with an ergonomic shape, and that the assemblies are of such a character that they are one hundred percent tight while also being smooth, so that there is no risk of bacterial collections in the relevant areas.

This object is achieved with a tool of the kind disclosed in the preamble to claim 1 , and where the shaft also comprises a metal tube, which, in the area between the handle and the tool part, comprises at least one bend and is surrounded by a plastic material of the same composition as the handle and tool part, and where assemblies respectively between the shaft and the plastic material surrounding the metal tube, and between the tool part and the plastic material surrounding the metal tube constitute a tight fusing together of plastic materials of the same composition as the remainder.

The tool configured in this manner is thus especially hygienic with regard to its surfaces, in that the whole surface is enveloped in the same plastic material, and in that the plastic material selected is one which is acceptable within the relevant industry. All assembly transitions will be tight. Moreover, as a consequence of the shaft being provided with at least one curvature, an ergonomic shape is achieved, while at the same time that the necessary stiffness is retained, in that the tube is made of a suitable metal which ensures that regardless of almost any product for which the tool is used, the tool will not be subject to any deflection.

By providing a tool according to the invention and as further disclosed in claim 2, the possibility is achieved of being able to mould the shaft of the tool with an ergonomically correct shape and also to adapt the product individually, in that the inner plastic material ensures that the metal tube does not become flat or get fractured during the moulding. Since the shape of the tool thus becomes independent of the mould, it is inexpensive to effect adjustments in the design.

By providing a tool according to the invention and as further disclosed in claim 3, a reduction in the weight of the tool is achieved, while at the same time ensuring its strength. By providing a tool according to the invention and as further disclosed in claim 4, a weldable material is achieved which is also approved for tools within the foodstuffs industry.

By providing a tool according to the invention and as further disclosed in claims 5 and 6, the possibility is provided of being able to weld the shaft together with the handle and the tool part by means of a friction welding, in that the shaft or handle and tool part can rotate, by which rotation heat will be created, and said welding is further disclosed in claim 7.

The invention also concerns a method for the manufacture of a tool, characterized in that

the shaft is straight before mounting of the handle and tool part,

the tool part and the handle are pressed down over each their end of the shaft,

the tool is secured in the tool part and the handle, and

the shaft is rotated to create friction welding between the shaft's surrounding plastic material and the handle and tool part respectively.

The invention will now be described in more detail with reference to the drawing, where

figs. 1a-c show a shovel according to the invention seen from the front, from the side and in perspective,

fig. 2 shows a section along the line ll-ll in fig. 1 , and

figs. 3a-b show a fork according to the invention seen from the front and in perspective.

Fig. 1 shows an example embodiment of a tool according to the invention, here a shovel, and the tool 1 comprises a shaft 2 with a handle 3 mounted on its one end and a working part, here a shovel blade 4, mounted on its opposite end. The handle 3 and the blade 4 are made of the same plastic material, preferably polypropylene, in that this is a weldable material. The shaft itself consists of a so-called sandwich construction, and consists in- nermost of a round rod 9 of polypropylene, said round rod being enclosed within an aluminium tube 8, which in turn is surrounded externally by a polypropylene tube 7. It is important that the shaft's outer plastic material consists of the same plastic material as the handle and tool part, thus making it possible to create a tight joint between these parts where a fric- tion weld is selected.

Fig. 2 shows a section through the shaft and the mutual relationship between the individual parts, and as mentioned above said shaft consisting innermost of a solid round rod of polypropylene 9 surrounded by the alu- minium tube 8, which in turn is surrounded by a tube of plastic material, i.e. polypropylene 7.

A suitable dimension for the tube part can be that the inner round rod is 20 mm in diameter. The aluminium tube itself has an inside diameter in the order of 20 mm and an outside diameter of 25 mm, while the outer polypropylene tube has an inside diameter of 25 mm and an outside diameter in the order of 27-28 mm.

Aluminium is chosen for the reason that this metal will give the tool a stiff shaft, and that the strength of the aluminium and its alloys is sufficiently great for use for the shovel function, while at the same time that aluminium is a light material. Since aluminium is not approved within the foodstuffs industry, it is given the outer covering of plastic as described above. The reason for providing a solid round rod of plastic material inside the tube is that the shaft, after the shovel has been assembled, shall be shaped in an expedient ergonomic design, and whereby the shaft is preferably provided with an upper and a lower bend 12 with an angle in the order of 5-15°. This is shown in fig. 1 b, where the shovel is seen from the side. The shaft can naturally be provided with several bends depending entirely on require- ments and the user's specific demands. As an alternative, the aluminium tube can be replaced by stainless steel of smaller wall thickness. The outer polypropylene tube 7 on the aluminium tube 8 does not cover the whole of the aluminium tube, in that about 75 mm at each end lies free and is thus not surrounded by the plastic, whereby the bare surface of the alu- minium tube protrudes. The connection part of the handle 3 comprises a tube with an inner diameter of a dimension which enables it to be press- fitted down in the shaft, and corresponding conditions apply at the other end, where the shovel part has a connection part 11 with dimensions which similarly allow press-fitting on the aluminium tube. When the shovel part and the handle are pressed down on the aluminium tube and are thus in place, they abut up against the shaft's outer polypropylene tube 7. The outer dimensions of these connection parts 10, 11 are such that a smooth surface transition arises between these parts and the outer polypropylene tube 7 on the shaft 2.

Fig. 1c shows the shovel seen in perspective, and also shows the ergo- nomically correct shape of the shovel.

The actual manufacture of the shovel is effected by inserting a solid round rod of polypropylene inside an aluminium tube of suitable length, so that the rod fills out the inner cavity of the aluminium tube. The outer polypropylene tube 7 is then pushed down over the aluminium, and in such a manner that approx. 75 mm of the tube at each end is exposed. The handle with its connection part 10 is now pressed down on the one end of the exposed aluminium tube, and the tool part, here a shovel blade with its connection part 11 , is pushed down on the other end of the shaft. The tool must now be set up, and here it is important that the shaft itself is completely straight. The handle 3 and the shovel blade 4 are now held fast, in that opposing pressures are applied from each end, and the shaft is now brought to rotate at a speed in the order of 900 rpm. With this rotation, a friction welding is effected between the handle's polypropylene and the shaft's 2 outer polypropylene tube 7, and a corresponding welding at the opposite end between the lower connection part 11 of the shovel blade 4 and the abutting polypropylene tube 7 which lies around the tube 8. The friction welding results in a completely tight fusion between the two assembly points 5, 6, and also ensures that these assembly points become smooth, which means that there is no basis for bacterial growth.

The shovel or tool 1 is now taken down and transferred to a work station where the shaft is provided with the necessary bends 12. As a conse- quence of the inside of the shaft being filled out with solid plastic material, for example polypropylene, it is ensured that the bends are rounded in the areas in which they are desired, and that the shaft does not flatten out or even break in the relevant areas. This bending and thus also shaping of the finished tool can be industrialised so that it is the same identical shovel or tool which emerges from the work station. Moreover, it can also be individualised in a very simple manner, unlike the known shovels where changes in the finished product necessitate a total change of the mould itself.

The points of assembly can possibly be given a subsequent surface finishing for the removal of any flash or fraze.

In addition to the fact that the relevant method provides a product which has a very hygienic surface, in that the product is completely covered with plastic and with a smooth surface, which is a surface which is accepted within the foodstuffs industry, there is also achieved a very high speed of production. However, in order for the friction welding to take place, it is an important parameter firstly that an interference fit is effected between the connection parts and the shaft itself, and secondly that the shaft and the connection parts are circular in cross-section. Finally, as will also appear from the invention, it is very important that the plastic materials which abut against each other are of the same type, hereby making a friction welding possible and enabling an optimum fusing together to be achieved.

The invention can not only be used for shovels, but naturally also for other products where demands are made regarding great stiffness and lightness combined with a smooth surface and with due consideration to an ergo- nomic shape.

In figs. 3a-b there is thus shown a second example of a tool, i.e. a fork, which similarly comprises a shaft 2, a handle part 3 and a tool part 4, here in the form of a fork part. Other tools can also fall within the scope of the invention, e.g. spades, brooms, stirrers, dustpans etc.

The handles and work parts can with advantage be injection moulded, and especially the handles will typically be the same regardless of which type of tool is involved, while the tool part can naturally be of various configurations.