GB2035138A - A method and apparatus for the non-contact marking of objects - Google Patents

Abstract

A mark 3 is made on an object 2 by blowing an air jet 23 controlled by a solenoid valve 7 past a fibrous ink wick, e.g. the tip 10 of a felt-tip or fibre-tip pen 5. Alternatively the nozzle for the air jet can surround the wick. The wick does not dry up and clog given reasonably regular use. If necessary it may be enclosed with a cover flap which opens under control of the compressed air supply. A stencil may be placed between the apparatus and the object. <IMAGE>

Description

SPECIFICATION A method and apparatus for the non-contact marking of objects The present invention relates to a method and apparatus for the non-contact marking of objects. The marking may take various forms, e.g. through a stencil to form a character, with relative movement between apparatus and object to draw a symbol, with selection of colour, size of mark and so on.

Methods and apparatuses of the above type have long been known. They are used for instance in the non-destructive materials testing for marking faults detected upon the surface of tested semi-finished products. In such an application, the apparatus consists for instance of an ink spray head arranged opposite the semi-finished product to be marked, a pressurized ink vessel connected to the spray head by means of a pipe-line, a compressedair line connecting the spray head to a compressed-air system, and an electrically controllable solenoid valve in the compressed-air line. In the spray head, a movable valve needle is controlled by a compressed-air cylinder and releases ink from the orifice of an ink nozzle when the compressed-air cylinder is operated. The latter in turn is operated by a compressed-air current released by the solenoid valve.One branch of the said compressed-air current causes compressed-air to be discharged through an annular gap surrounding the ink nozzle, which compressed-air entrains the released ink particles thus forming an ink jet producing the desired mark.

Devices of the type described above are commonly used, but suffer from serious drawbacks, one of which is the need for maintenance. Ink residues in the area of the orifice of the ink nozzle tend to block the orifice very soon, especially as quick-drying inks are commonly used. One has tried to prevent such blocking by causing a slight air current always to emerge from the annular gap surrounding the ink nozzle. However, this attempt has proved unsatisfactory, especially in cases where the orifice of the ink nozzle is upwardly directed. Accordingly, regular cleaning of the nozzle is necessary. Frequent difficulties are also encountered at the sprayhead in respect of the rearward sealing of the ink chamber against the movable valve needle.To ensure the easy motion of the needle i.e to minimize the braking effect, incomplete sealing is accepted which means that ink residues will accumulate here, too, and will have to be removed from time to time. Another disadvantage lies in the fact that moving the valve needle means moving quite a considerable mass, and as indicated before, frictional forces cannot be completely avoided. Thus, the marking process frequently cannot be carried out with the required rapidity. Still another disadvantage lies in the complexity of the device described.

From German Laid-Open Patent Application No. 16 21 973, a paint spray device is known, in which the paint supply consists of a paint spray can under pressure. In this arrangement, the paint nozzle is likewise released by a valve needle which in this case is however operated by a solenoid. This arrangement also exhibits a number of disadvantages.

The paint spray can can be used only in upright condition. The blocking of the nozzle orifice cannot be avoided. In addition, it is no longer possible without any difficulties to blow the nozzle orifice through by means of a constant slight air current. Thus, the nozzle orifice must be frequently cleaned. The rapid response of the paint spray device is affected by the mass of the parts to be moved and by frictional forces. Also the use of aerosols is environmentally undesirable.

Further, a marking device comprising a fibre-tip pen has been known which is seated in a movable holder and moved in response to an electrical signal by a solenoid towards the surface to be marked so that the writing tip of the fibre-tip pen comes into contact with the surface where it produces an easily visible mark. It is an advantage of the device just described that it is simple and essentially maintenance-free. On the other hand, a number of decisive disadvantages render the general use of the device impossible. An important ir---venience must be seen in the fact that the operation of the device is not of the non-contact type. Thus, its application is from the very beginning restricted to bright and clean surfaces, since rough, oily or scaled surfaces, for instance, would render the fibretip pen unserviceable within very short.

Another fact which prevents the general application of the device is to be seen in the relatively heavy mass of the parts to be moved and the slow response of the marking device resulting therefrom.

It is the object of the present invention to provide a method and an apparatus of the type described above, which guarantees quick response and maintenance-free operation by simple constructional means.

According to the present invention, there is provided, a method for the non-contact marking of objects, wherein an air jet is directed past a wick of fibrous material towards the object to be marked, the wick being connected to a supply of liquid colourant in a closed container.

The invention also provides an apparatus for carrying out the method of claim 1, comprising a compressed air jet and air valve controlling the jet, a wick of fibrous material in the path of the air jet, and a closed container supplying the wick with liquid colourant.

The air valve is the only part that necessarily has to be mechanically moved, and the user may choose for this purpose for instance extremely quick-acting solenoid valves with response times of only a few millseconds. He need not fear any odourous annoyance of explosion danger. The air pres sure of the compressed-air source is uncritical and may vary within broad limits. The same applies to the orientation of the apparatus, which with is likewise uncritical. Thus, unpwardly directed marking is possible without any in convenience. Another advantage resides in the fact that the cleanly delimited colour spot dries amost instantaneously. Still another ad vantage can be seen in the compact, space saving design permitted, as evidenced the embodiments of the invention described be low.In one advantageous embodiment of the invention, the wick is the lip of a commercial felt-tip felt-tip or fibre-tip pen. Tests have shown that when applied in accordance with the inven tion, a commercial fibre-tip pen operates com pletely maintenance-free during a safe service life of 8 to 10 hours, given a fixed timing of the marking puse of one minute. As mass produced fibre-tip pens can be obtained very cheaply and easily exchanged, such a device operates at low cost.

The invention will be described in more detail, detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows an apparatus embodying the invention; Figure 2 shows an alternative arrangement of the apparatus; and Figure 3 shows an alternative design of a detail.

Fig. 1 shows an apparatus 1 to be used for marking a tube 2 with a colour spot 3. If a definite definite symbol is to be printed, a stencil can be supported between the apparatus and the tube by a bracket for which fixing holes 4 are provided. The apparatus comprises only a few easily assembled parts, namely a fibre-tip pen 5, a centre block 6, a solenoid valve 7 and a clamping arrangement 8. The fibre-tip pen 5 used in this case is commercially available.

The writing tip 10 of the fibre-tip pen 5 is connected to an ink supply contained in a I cylindrical reservoir, namely the shaft 9 of the fibre-tip pen 5. As is commonly known, capil lary forces act to supply the writing tip 10 with ink in any orientation of the fibre-tip pen 5, even if the tip is upwardly directed. As a result, there are no restrictions for the appa ratus 1 regarding its operating position. The shaft 9 of the fibre-tip pen 5 rests in a bore 11 in the centre block 6 and abuts with its forward end against a collar 1 2. This arrange ment ment defines the position of the writing pen 10 with sufficient accuracy when exchanging the fibre-tip pen 5. The solenoid valve 7, which is likewise commercially available, is mounted in a recess 13 in the centre block 6.

The inlet opening of the solenoid valve 7 is supplied with compressed-air from a hose 1 7 via a nipple 1 6 which is sealed by a washer 1 5. The solenoid valve 7 can be operated by a current pulse supplied to the solenoid valve via a cable 18 and a plug connection 19. A nozzle 20 is directly screwed to the outlet opening of the solenoid valve 7 and sealed by means of a washer 21. The bore 22 of the nozzle determines the direction of an air blast 23 that will be generated by operation of the solenoid valve 7 in front of the orifice of the nozzle 20. The angle CL between the axes of the air blast 23 and the fibre-tip pen 5 is preferably 45 .

In its forward poSition, the fibre-tip pen 5 is held by a simple clamping arrangement 8 comprising a bolt 25 fastened in bore 26 of the centre block 6, a clamping cap 27 and a sleeve 28 firmly bonded to each other, a small tube 29 and a helical spring 30 arranged in the gap between the bolt 25 and the sleeve 28, and a circlip 31 retaining the said parts against the force of spring 30. The sleeve 28 and the clamping cap 27 can be moved in the longitudinal direction of the bolt 25 and pivoted about the latter's axis. When the clamping cap 27 has been placed upon the bottom of the fibre-tip pen 5, the latter is pressed by spring force against the collar 1 2.

The operation of the apparatus is extremely simple. Inserting the fibre-tip pen 5 and closing the clamping arrangement 8 are all the preparatory steps needed. The strongly nondivergent air blast 23 generated by operation of the solenoid valve 7 strikes the writing tip 10 and entrains ink particles therefrom. The resulting ink jet 32 produces the desired marking.

In a wide range of applications, the simple apparatus of Fig. 1 will meet all requirements.

When in certain cases the down-times between two marking operations exceed a given period of time, drying-up of the writing tip 10 can be prevented by supplying an additional operating pulse to the solenoid valve 7 at regular intervals, for instance at intervals of 10 minutes. This pulse may be emitted at a moment where no object is in front of the writing pin 10. When the device 1 is used in non-destructive testing of say rods or pipes, such intermediate operation may most conveniently take place every time a test piece has left the device. When the device 1 is to remain out of operation for some extended period of time, the protective cap that forms part of every fibre-tip pen may be applied.

The device 41 of Fig. 2 permits interruptions between two marking operations of any desired length of time, with only relatively little additional expenditure. The risk that the writing pin 10 may dry up is completely eliminated without the need of any additional measures. The fibre-tip pen 5 and the clamping arrangement 8 of device 41 are identical to the fibre-tip pen and the clamping arrange ment of the device 1 and fastened to the mounting block 42 in the above-described manner. The writing tip 10 of the fibre-tip pen 5 projects into the lower portion of a bore 43 in the mounting block 42. The upper end of the bore 43 is plugged with an insert 44 the lower portion of which ends in a nozzle 45 while a hose nipple 47 is screwed to its upper end over a washer 46.The lower opening of the bore 43, i.e. the space containing the writing tip 10, is closed by means of a lightweight flap 48 seated at the mounting block 42 to pivot about an axis 49. The bore 51 extending in parallel to the bore 43 takes the form of an air cylinder with a piston 52 sliding therein. A ram 53 mounted on the piston is guided in a bore 54 in the mounting block 42 to operate the flap 48 with its lower end. Springs 50 and 55 are provided for returning the flap 48 and the ram 53 to their initial positions. The springs 50 and 55 can be sized to ensure that their force is just sufficient to overcome the frictional forces with the required safety. It is not necessary, that the flap 48 or the ram 52 be returned quickly. A sleeve 56 closes the bore 51 and delimits simultaneously the stroke of the piston 52 at its upper end.The sleeve 56 has screwed into its bore a hose nipple 57 which is sealed by a washer 58. The hose nipples 47 and 57 are connected to a compressed-air system via short hose pieces and one common or two separate solenoid valves.

Operation of the solenoid valve or valves causes the piston 52 to slide forward and the ram 53 to open the flap 48. The air current released by the nozzle 45 impinges upon the writing pin 10 of the fibre-tip pen 5 where it releases the ink jet required for marking in the manner described above. When two solenoid valves are provided, the opening of the flap 48 and the generation of the ink jet can be spaced in time by imparting a short time lag to the control pulse supplied to the solenoid valve feeding the nipple 47. As mentioned before, no quick action is required for the return of the flap 48 and the piston 52.

Rather, a certain delay may even be desirable.

When he marking operations follow each other in quick succession, the flap 48 will thus not have to be operated each time which will have a favourable effect upon its service life. The return of the piston 52 may be easily delayed by providing only a very small venting opening for the displacement space of the piston 52.

The size of the colour spot 3 depends upon the distance between the writing tip 10 and the surface of the object to be marked and can be varied within very broad limits. For stencil operation, the size of the colour spot 3 depends upon the desired character size. As regards mraking operations in which relative movement between the apparatus and marked object is employed, the required short response times and the desired accuracy of the marking will mostly lead to very small distances being appropriate between the writing tip 10 and the object to be marked.

As an alternative to the tubular nozzles 22, 45 described above, Fig. 3 shows a nozzle arrangement 61 having its inner portion 62 provided with a suitable bore 63 for receiving the fibre-tip pen 5. The nozzle 64 as such is formed by the gap between the outer portion 65 and the inner portion 62 of the nozzle arrangement 61 so that an outlet opening 66 of the nozzle 64 is provided which surrounds the front portion of the fibre-tip pen 5 and its writing tip 10 in the form of a ring. An opening 67 in the outer portions 65 is designed to define the resulting ink jet to a certain degree without getting into direct contact with the colour particles. This is ensured by part of the compressed air flowing along the outside of the writing pin 10, thus forming a sort of jacket around the ink jet. An air space 68 feeding the nozzle 64 may be directly connected to the outlet end of a solenoid valve.

In the embodiments described above, the wick made of fibrous material and the colour supply in the closed container takes the form of a fibre-tip pen 5. Although this will be particularly advantageous in most cases there are also applications in which the fibre-tip pen is advantageously replaced by a device not primarly conceived as a writing pen. An application of this type may for instance be found in cases where the colour supply is to have a considerable volume or where several wicks are to be connected to one colour supply.

Claims (11)

1. A method for the non-contact of objects, wherein an air jet is directed past a wick of fibrous material towards the object to be marked, the wick being connected to a supply of liquid colourant in a closed container.

2. An apparatus for carrying out the method of claim 1, comprising a compressed air jet and air valve controlling the jet, a wick of fibrous material in the path of the air jet, and a closed container supplying the wick with liquid colourant.

3. An apparatus in accordance with claim 2, wherein the wick and container consist in a felt-tip or fibre-tip pen.

4. An apparatus in accordance with claim 3, comprising holding means for the felt-tip or fibre-tip pen with an opening adapted to the shape of the pen and means for fastening the pen in the opening.

5. An apparatus in accordance with any of claims 2 to 4, wherein the air jet is directed upon the tip of the wick.

6. An apparatus in accordance with claim 5, wherein the jet is directed on the wick at an angle of 45 .

7. An apparatus in accordance with any of claims 2 to 6, wherein the jet is mounted directly at the outlet of the valve.

8. An apparatus in accordance with any of claims 2 to 4, wherein the jet comprises an annular orifice with the wick extending therethrough.

9. An apparatus in accordance with any of claims 2 to 8, where the wick is surrounded by a space provided with closing means which can be opened by the valve or essentially in synchronism with its operation and which will close again automatically.

10. An apparatus in accordance with claim 9, wherein the closing means consist of a light flap.

11. An apparatus in accordance with claims 9 or 10, wherein the closing means are operated by a compressed-air cylinder.

1 2. An apparatus in accordance with any of claims 9 to 11, wherein the return of the closing means is time-lagged.

1 3. An apparatus substantially as hereinbefore described with reference to Fig. 1 or Fig. 1 as modified by Figs. 2 or 3 of the accompanying drawings.