The invention relates to a method of applying a surface layer of liquid or paste-like consistency to an object, a system as well as use thereof.

The prior art

Surface coating is known in numerous variations, such as application of an agent for lubrication, preservation, corrosion protection, marking, adhesive, etc.

It is common to these agents that they have either a liquid or a paste-like consistency, and that they may be applied by means suitable for the pur- pose.

An example of a system for the application of a surface material, in the form of wood impregnation agent to a piece of timber, may be seen in JP 11- 165106 A. In this, a piece of timber, which is normally square or rectangular in cross-section, is moved in between foam-coated rollers which apply wood impregnation in an even layer to the surface of the timber. Such a system, however, is not suitable for objects which are not square or rectangular, or which do not have an essentially smooth surface. Where, e.g. it is a matter of lubrication or corrosion protection, the objects will normally be applied either by dipping or application of the surface agents. This applies to adhesive agents, as well.

Where marking is involved, this frequently takes place by application of marking adhesives. This may be called a manual or partly manual application, which therefore requires handling, which is time-consuming and cum- bersome.

The object of the invention It is the object of the invention to simplify this application to an object, and this is achieved according to the invention by a method, wherein the object to which a surface layer is to be applied, is introduced into a cavity whose walls are formed by an absorbing, resilient material to which surface material is supplied, following which the absorbing material is pressed against the object to deposit surface material on its surface.

In this surprisingly simple manner, an object disposed in the cavity will have applied thereto the desired surface material in that the resilient, absorbing material with the liquid or paste-like surface material absorbed in it is pressed against the object, whereby the surface material is squeezed out and applied to the surface of the object.

With a uniform pressure force and amount of material in the resilient material, it is hereby possible to deposit a completely precise amount of material, and this may moreover be dimensioned easily so that an even distribution of the material on the object is achieved, irrespective of the shape of the object. Thus, it is possible to treat surfaces which are not uniform. Thus, the present invention is also suitable for applying a surface material to objects of an arbitrary cross-section, and the method is likewise suitable for treating the surface of objects of arbitrary cross-section, including e.g. also objects of a circular or oval cross-section. In addition, objects with non-uniform surfaces, such as, but not limited to, objects with threads or with beads or grooves in the surface extending e.g. axially or in the circumference of the object, will also be treated on the lower lying surfaces, e.g. in grooves or between beads. When, as stated in claim 2, the resilient, absorbing material is squeezed or pressed against the object by means of a pressure medium, the method may be controlled by controlling the pressure, which allows automated application.

When, as stated in claim 3, the material is supplied to the absorbing, resilient material in that it is supplied under pressure, the filling degree and thereby the application degree may be controlled by adaptation of the pressure and thereby the supply of the material on the object.

When, as stated in claim 4, using an apparatus in the form of a housing with an opening for the introduction of the object into a cavity, which is surrounded by a wall of the resilient, absorbing material which is saturated with application material, a pressure externally on the wall will press it inwards against the object and apply an accurate amount of material to the object irrespective of the shape of the surface of the object in a precise and thereby material-saving manner.

When, as stated in claim 5, a resilient, tight wall is arranged around the re- silient, absorbing material, the pressure will be distributed evenly, and the coating will thereby be deposited quite uniformly and precisely on the object.

When, as stated in claim 6, the surface material is supplied to the absorb- ing, resilient material, the surface material will be distributed easily in the absorbing, resilient material and thereby ensure that uniform application over the desired part of the surface of the object takes place.

When, as stated in claim 7, the apparatus is constructed such that it is self- sucking, i.e. the surface material also presses a piston down by means of the pressure medium for the pressure chamber, it will be possible to press the material into the resilient and absorbing material, when the pressure medium is supplied to the pressure chamber, and suck the surface material back into the chamber at the return movement of the piston. When, as stated in claim 8, pressure medium is supplied to the outer side of the flexible wall, it will be easy to control the application process when the pressure is applied and discontinued, respectively.

When, as stated in claim 9, the method and the apparatus are used for applying surface material, it is possible precisely and rapidly to apply the desired amount and thereby apply a surface layer to e.g. a bolt, optionally the threads alone just before the mounting.

Finally, as stated in claim 10, it is expedient to use the method and the apparatus for lubricating objects with grease or oil, as well as for various marking purposes, since, e.g. when using suitable demasking it will be possible to print text, codes, etc. on the object.

The drawing

An example of an embodiment of the invention will be described more fully below with reference to the drawing, in which fig. 1 shows a sectional view of an application apparatus with an object in the form of a bolt inserted, fig. 2 shows an enlarged section of the area around the threads prior to the impression, shows the area during application, impression of the material, and fig. 4 shows a sectional view of an apparatus with self-sucking pump function.

Description of the exemplary embodiments

Fig. 1 shows an example of an apparatus 1 for performing the method according to the invention.

The apparatus comprises a housing 2, which is provided with a cavity 3 extending from one end of the housing and into it.

A wall of a resilient and absorbing material 9, which extends inside the housing 2 and forms a lateral wall of the cavity 3, is arranged along the sides of the cavity 3.

An impermeable wall 4, which is made of an elastic, that is resilient material, is arranged externally on this resilient and absorbing material 9. The resilient, absorbing material 9 is preferably made of a so-called open foam, that is that the material is capable of sucking up surface material corre- sponding to a sponge and is thus also resilient and elastic in a corresponding manner.

A pressure chamber 5, which is in communication with a pressure system 17, extends inside the housing 2 around the resilient wall 4. Via a line 6 and with a control valve 7, pressure medium, e.g. compressed air, may be supplied to the pressure chamber 5 from a pump 8. When the supply of pressure medium to the pressure chamber 5 is controlled, it is possible to control the method and e.g. obtain an automated process. Instead of compressed air, other pressure media, such as hydraulic and/or other gaseous media may be supplied. A supply pipe 10 with openings 11 for surface material 15, such as grease, is shown at the bottom of the housing, said supply line ensuring that there will always be surface material 15 in the resilient, absorbing material 9. A pump 12 pressurizes the surface material 15, and this is conveyed via the valve 16 to the resilient, absorbing material 9.

An object, e.g. a bolt 13 with threads 14, is shown disposed in the cavity 3 in the housing 2.

The surface material has been supplied to the resilient, absorbing material 9, and when pressure medium is supplied, e.g. compressed air, to the pressure chamber 5 by operation of the valve 7, the elastic wall 4 and the resilient, absorbing material 9 with surface material 15 will be pressed in against the object 13, 14, as shown in fig. 3.

Hereby, a layer of the surface material 15 is deposited on the object 13, 14 in an amount which depends on the pressure in the pressure chamber 5 and on the supplied amount of surface material 15 in the resilient and ab- sorbing material 9. It is noted that surface material is deposited only at the points where there is contact between the object and the wall. For instance, an increased pressure in the pressure chamber 5 will cause the resilient, absorbing material 9 to be pressed into grooves in the surface 13, 14 of the object, e.g. into threads, as shown in fig. 3. Conversely, a lower pressure in the pressure chamber 5 will mean that it is just the surface of the object 13, 14 which is coated with the surface material 15, whereas the surface in e.g. grooves is kept free from the surface material 15.

When the pressure is removed from the pressure chamber 5, the wall 4 and the resilient, absorbing material 9 containing the surface material 15 will be returned to the starting position, as shown in fig. 2. Then, a new object may be introduced, and the method may be repeated.

Fig. 4 shows an example of an alternative embodiment, in which the supply of surface material 15 takes place by a pump incorporated in the housing 2.

A piston 18 is arranged at the bottom of the pressure chamber 5, said piston being capable of sliding in a pressure-tight manner against the inner side of the housing 2. A bellows 21 is disposed between the elastic wall 4 and the piston 18 to create tightness.

Channels 1 1 are provided in the piston 18 in order to allow surface material 15 under pressure to pass from a chamber 20 on the lower side of the piston and into the resilient and absorbing material 9. Finally, a spring 19 is shown between the lower side of the piston 18 and the bottom of the housing. The purpose of the spring is to return the piston 18 when the pressure in the chamber 5 ceases.

When the pressure medium is supplied to the pressure chamber 5, the wall 4 and the resilient, absorbing material 9 containing surface material 15 will be pressed inwards against the object 13, to whose projecting parts 14 a surface layer will be applied, at the same time as the piston 18 will be pressed against the end wall of the housing, as illustrated by the arrow 22. This will reduce the volume in the chamber 20, for which reason the surface material will be pressed via the channels 1 1 in the piston up into the resilient, absorbing material 9.

When the pressure ceases in the chamber 5, the piston 18 will be returned by means of the spring 19, whereby a portion of the surface material will be sucked back into the chamber 20, which will thus always be filled. A non-return valve 16 ensures that the supply of surface material to the absorbing, resilient material 9 via the chamber 20 takes place automatically and in accordance with the consumption which the deposition on the object involves.

The apparatus operates in this simple manner as a self-sucking apparatus, which just needs pressure medium in order to operate.

The above-mentioned apparatus and method are particularly suitable for applying grease or oil to the surface of objects, but, of course, it may be other forms of material which lend themselves for application to the surface of objects.

For instance, it may be a matter of colour application, such as printing of text or codes, it being possible to insert a mask between the object 13, 14 and the absorbing, resilient material 9 when text is printed. In addition, the method may be used for all forms of objects, just provided that the cavity and the apparatus are adapted to the dimensions. A precise application of material is achieved, which is rapid and also material-saving, since material is just deposited on the desired faces, as required.