The invention refers to a specific method and mechanical device to prevent unintentional interruption by a sensor and principally sensors used in control system. Within modern industry there are considerable and continuing problems caused by unnecesary stoppages of machine units. These stoppages are often the result of, that sensors reacting with no valid or justifiable operational reason.

To achieve high degree of effective and unhindered machine production within modern industry, one focuses on equipment efficiency and in particular a means of minimising unintentional machine stoppages. At this kind of high-effective production in modern factory's are sensors most commonly inductive sensors used in control systems, thus can be made troublefree and hence deliver considerably more effective and efficient production in the factory. The combination of high frequency and the fact that the sensor give is the last part in the operational system or a machine, demans a operational R=0.99 and only permits 5 faults per million operations hours for a sensor, while as a comparison, one can mention a part system "automatic steering system" is allowed R=0.76 and 140 faults per million operation hours. The most common type of sensor is supposed to react to metallic materials. A very big problem is that machines stop, "release out" for wrong reasons; for example metalfilings flying around, instead of normal and correct sensor-reaction on intended targets like metalfixtures and metal paletts.

The point of the machine unit "release out" and stops without any concrete physical engine problem is a very big and economical heavy problem. A major contributing factor to the problem is that the gap between the sensors contact point and the metallic feeling area, which due to necessity, must be small. This creates opportunites for "wrong metal" to cause the unnessesary stops.

The workorganization in an automated environment, with very few machine-operators, make these types of misstakes frequvent. However, althrough the solution is simple and need only a restart, in reality the task

becomes much longer, because there is no operator immediately available. With modern production technics, one is aware that these stops creates bigger loss than greater repair-works.

The existing method for solving problems caused by inductive sensors disturbed by wrong metal induction, for example filings flying around, is varius methods of extra spraying with cutting-oil, whose real purpose is to cool down the tools. This solution is ineffective an uneconomical as it can also contribute to the problem it ^' s supposed to solve. A fundamental misstake with the cutting-oil princip, is that the flushing always are directed towards the area who should be kept free of metal filings. Because no metal filings are created in and around the gap to be kept clean, no removing transport is present, and only add and continual transport, are allowed with the existing method. To achive result with existing method, the spraying liquid ^' s applied at high pressure, which has the negative effect that metal filings being forced in and get stucked in the gap between the sensor and the reactionmass. This is the reason that the problem can not be solved by machine-restart, therefor manual removal of the metal filings is required. The flush-method is uneconomical because it demands cutting-oil, which in turn needs to be cleaned after use.

This method also creates an unwanted soiling of machine area, and not only has an unpleasent effect, but adversely affects machine and repair efficiency. Repairs to machines must, due to necessity, start with a general cleaning.

There seems to be a need to find a solution for the major problems within industry with costly machine stops for no special reason. The ideal solution of the problem would be a sensor with high security, wich only reacts when a faulty item passes the sensor and where the control-system is programmed to react.

The proposed invention will solve the above mentioned problem in a simple and effective manner and can be used together with existing mounted sensors (inductor). The ivention also refer to a device who has the purpose to prevent unwanted affect on the sensor.

According to the invention it's effect to unwanted reaction on a sensor, especcially an inductive sensor. In, for example control system, by means of a protective barrier causes a repellent effect for the sensors detecting surface.

This means that all unwanted material such as metal filings and similar objects that can affect the sensor, are kept clear of the sensors detecting surface. To create the repellent effect (barrier), a media is used such as liquid or gas which create the protection barrier near and around the detecting surface and in it's axial extention.

The protective barrier is created between and around the sensor, but with a distance from it's housing, arranged organ for example a cap.

The substance that creates the barrier can be supplied in a continous way. It can be done continously or discontinously depending entirely on the area of use. The substance can recive an impuls to start at a precice time before the reactionmass is due to pass the sensor in a machine unit.

The device to prevent unintentional interuptions by sensors consist of a housing unit holding a sensor for example, inductive sensor. Between the housing unit and the sensors casing a gap is created. The housing unit also contains a tube for disturbation of medium intended to flow through the space and out by the sensors detecting area to push away unwanted material, such as metal filings.

The casing around the sensor can either be a fixed attachement or a separate unit which is independently attached. To arrange the sensor and housing unit as separate items, once can simply detach them for use in machine units where a sensor is already present. Fixing the housing unit to an existing mounted unit may be done in several different ways. One way is if the housing unit is mounted (fixed) and connedcted to a device wich distributes applies to the barrier medium, in this case the sensor can simply be attached. Another way to use existing mounted sensors on the machine unit is to dismantle the sensor and the housing unit is mounted on the sensor while one makes use of the tapping which normaly exists on sensors. After the housing unit is mounted on the sensor, the sensor is put back into the place. While one only needs a small space for the barrier medium, between the sensor housing and the inner wall of the housing unit and the housing unit has thin walls, so there is sufficient space to mount the housing unit on the sensors already exist, where problems caused stops. As the invention can be used in this way, where the sensors already in use can be attached to proposed housing unit there is little need for large investment to reduce unscheduled stops caused by sensor release out.

The invention will now be described with reference to enclosed figurs which only shows the device according to the invention. Figure 1 shows a sensor arranged in the housing unit and figure 2 shows the housing unit.

In figure 1 a known sensor 1 is mounted in the housing unit 2. The housing unit can be designed as a case and will future be named as case. In the back of the case part 3 the sensor 1 is mounted. How the sensor 1 and the case 2 are connected to each other with tapping or similar method, is not important for the invention, the only demand on attaching method is that it is tight to ensure the barrier medium does not leak out. Between the front 4 of the casing which is considerably larger then the rear 3 and sensor 1 is space 5. The space 5 is connected with a suitable device 6 not shown, and the device supplies space 5 with the medium to create the barriereffect on the sensor 1 detecting surface 7. The substance, gas or liquid, flows into the channel 8 and further into space 5 where it is distributed in the direction of the arrows toward the space opening 9, the substance is therefor distributed around the detecting area 7 keeping it clean and free of metal filings etc. When a, non shown mass, for example metall paletts passes the detecting area 7, unwanted material will not disturb it, and the sensor can detect the palett in the way it is meant to. The substance need not to flow continously, it can come periodic or start immedliaty before the palett is due to pass the sensor. This of course will depend on the freqvency that the palett is passing.

It must been noticed, there it not shown by the figure, that the distance between the sensor detecting area 7 and the passing palett, is so small, that only a medium, such as a gas or liquid can pass through to keep the detecting surface clean from unwanted objects.

Figure 2 the housing/ cap shown with its back 3 which is equipped with some form of connection or coupling. For example the cap part 3 can be tapped that the sensor can be fixed on. The cap 2 is described above equipped with supply tube 6 which contains a channel 8 through which the substance flows in. Where the supply tube 6 is placed on the cap or what shape it takes is not essential for the invention.

The invention is not limited of what shown or described above, it is only limited by the claims.