SAFETY SYSTEM FOR USE IN CONNECTION WITH WORKING MACHINES

Abstract: A safety system for for example a band saw (2, 3, 4) driven by a motor (5) and having a working plane (1) is lighted with UV light by a lighting means (6, 7) with modulated light. When a glove (15) with fluorescent material enters the supervised area (13, 14) an optical system (8) detects the fluorescent light excited from the glove and activates a signal means (17) and one or more blocking or cutting means (16).

Description: SAFETY SYSTEM FOR USE IN CONNECTION WITH WORKING MACHINES. The invention relates to a safety system of the kind described in the introduction to claim 1. Many machines and tools used in industry involve a great risk of body injury to the persons operating the apparatus. There are many rules and regulations for the screening of apparatus having movable tool parts such as cutting, shearing, punching tools etc. as well as for the operation of such apparatus so that injuries are avoided or minimised. It is not, however, possible to completely avoid body injuries which clearly appears from the industrial accident statistics of the Directorate of Labour Inspection. As an example thereof reference is made to the great number of personal injuries seen within the fish and meat industry where cutting and sawing tools are used for cutting fresh and frozen meat and fish. Here and in similar areas hands and arms get very close to the cutting tools, for example a high-speed saw blade, whereby inattentiveness for fractions of a second may have serious consequences for health and working capacity. It is the object of the invention to provide a safety system which will stop or block a working machine before the operator or operators are injured if some body part get too close to the actual tool. The object is furthermore to provide the design of such a safety system in such a manner that it may know the difference between the product to be worked and the operator. This is achieved by designing the system according to the invention as further disclosed in the characterising part of claim 1. There is thus obtained a system that reacts in less than a millisecond so that it is not possible to move for example a hand into the cutting tool without the system stopping or blocking the tool immediately before the hand reaches the tool. The system is highly insensitive to changes and variations in the surroundings such as changes in lighting conditions, passing of persons or material etc. in that it will only react to light with a certain wave length and which is modulated with a certain frequency. The system according to the invention can furthermore be improved by designing the optical/electrical system as disclosed in the characterising part of claim 2. It is thereby ensured that only fluorescent light of the particular frequency may pass the optical system and reach the detector. The insensitiveness of the system to light and reflections from the surroundings is substantially increased if it is designed as disclosed in the characterising part of claim 3. The visual field of the optical system is thereby reduced so that only a circular area around the tool is supervised and the effect of reflections from for example the operator is reduced by the matted working plane. A particularly simple way to secure hands and fingers against accidents when working with cutting tools is obtained by using a working glove as disclosed in the characterising part of claim 4. The operator uses a special working glove on each hand. For other types of machinery there may be designed other articles of clothing with or of fluorescent material. A particularly advantageous embodiment of the invention is disclosed in the characterising part of claim 5. There is here used light covering an area which is not unpleasant or which in any other way hampers the work. There is used a red fluorescent material so as to ensure the constant use of the detecting means for example a working glove as described above. By this embodiment there is achieved a practical system functioning at a very high degree of reliability and where the system is almost completely insensitive to changes in the lighting conditions of the surroundings. By designing the system according to the invention as further disclosed in claim 6, it is possible to supervise and secure special working machines, for example a high-speed band saw for cutting foodstuffs. The optical system will supervise a circular area around the saw blade and as scon as a flourescent material which can be detected by the optical/electrical system enters the circular area, the blade is instantaneously stopped so that injuries are avoided. Saws of this type are some of the most dangerous tools used in the food processing industry and many injuries can be avoided by using the system according to the invention. In order to avoid undesirable blocking or cutting of the blade or some other cutting tool, the system according to the invention may be designed as disclosed in the characterising part of claim 7. The system may thus be adapted so as not to initiate a blocking or cutting if for example a glove touches the supervised area so that only a quite small section of the glove enters the area. If the glove is taken further into the supervised area, blocking or cutting is instantaneously activated. This function may also be used for checking whether the system is operating correctly or not or for checking the quality of a glove with a view to safety. Furthermore the safety system according to the invention may be designed as disclosed in the characterising part of claim 8. It is thereby ensured partly that the system is always operational and partly that the operator will have to check the system prior to any start of the tool thus ensuring that the operator uses the correct detecting means for example the right gloves. An important feature of a safety system as the one described in the application is that the operators have confidence in the system and that they are all the time reminded of the presence and function of the system in that the required procedures for starting the machine must be implemented each time the machine is to be started. The invention will be further described in the following with reference to the drawing showing a preferred embodiment of the invention wherein Fig. 1 shows a band saw with a safety system according to the invention and Fig. 2 shows an electrical basic circuit diagram therefor. Fig. 1 of the drawing shows a high-speed band saw for cutting for example deep-frozen fish or meat. The invention will be further described in connection with this working machine, but it is obvious to a person skilled in the art that the safety system according to the invention may be used on almost any other working machine where there is a risk of personal injuries. The band saw consists of an endless saw blade 2 extending over two wheels or rollers 3,4 where one wheel 4 is driven by a motor, for example an electric motor 5. The saw blade 2 passes through an opening in a working plane 1 which may be a worktable which is either stationary or partly movable, the area in the vicinity of the blade being usually stationary. A lighting means 6 with fittings and suitably designed reflector and with a light source 7, such as a UV (ultraviolet) type flourescent tube having powerful radiation around 400-450 nm wave length lights the working plane around the saw blade. 1 There is moreover shown a working glove 5 covered with a flourescent material for example having the colour daylight red type Beckers no. 189 which may be excited by the ultravialet light from the 5 light source 7. By excitation of the flourescent material there is radiated light with a wave length of the approx. 630 nm. The area around the blade 2 is supervised by an Ω optical/electrical system 8 comprising one or more lens systems 9, a circular mask 10, an optical band-pass filter 11, and a detector 12 such as a 1 cιr.2 silicon solar cell of a generally known type. The optical/electrical system 8 supervises 5 a circular area 13,14 around the blade where the size and shape of the circular area is determined by the inserted circular mask 10 in the optical system. 0 The apparatus moreover has a warning horn 17 or any other type of optical or acoustic warning means and a schematically shown blocking or cutting means 16. It is obvious that it is possible to use several blocking or cutting means 16 for example a means 5 under the plane 1 (as shown) and a means (not shown) a distance over the plane so that at least the length of blade which may injure the operator may be retained if the safety system is activated. 0 The operation of the safety system shown in Fig. 1 will now be explained with reference to Fig. 2 of the drawing showing a basic diagram of the electrical circuit. The UV-lamp 7 receives current from a supply source 21 having an alternating voltage between 1-50 kHz so that the UV-light is modulated with a fixed frequency" controlled by a circuit 22 determining the modulation frequency. The working plane 1 is thus lighted with modulated UV light around 400-450 nm. The letters A-F in Figs. 1 and 2 indicate how the electrical circuit in Fig. 2 is connected to the apparatus shown in Fig. 1 where A in Fig. 2 is connected to A in Fig. 1, B in Fig. 2 is connected to B in Fig. 1 etc. The detector 12 in Fig. 1 is connected to the entry point of the circuit 18 in Fig. 2 comprising amplifier circuits and electrical filters partly so that noise is shut out and partly so that only electrical signals with a frequency substantially corresponding to the modulation frequency will reach the detecting and level determining circuit 19. In the detecting and level determining circuit 19 controlled by the synchronisation circuit 22 it is determined whether the detector 12 has received excited light from the flourescent material of the glove 15. Light having other wave lengths will already to a large extent have been filtered off by the band-pass filter 11. A logical circuit 20 receives the signals from the detecting and level determining circuit 19. The logical circuit 20 checks whether the UV-light source is on in that a signal to this effect is received from the supply current 21 and moreover checks whether the motor 5 is running or is stopped. From the logical circuit 20 signals are sent to the blocking or cutting means 16 at outlet D, signals for stopping the drive motor 5 at outlet E, and signals for the warning horn 17 at outlet F. Additionally, it is possible from the logical circuit to control a lamp signal board 23 with a lamp 24 indicating whether the UV-lamp 7 is on, with a lamp 25 indicating whether the system has been -tested or not, with a lamp 26 indicating whether the motor is running and with a lamp 27 indicating whether the entire apparatus is connected to the mains or not. When for example the working glove 15 is taken into the supervised area, which for the sake of clarity is shown as two circular areas 13 and 14, the glove will first enter the area marked 13. When for example -5-lcm.2 of the glove is within the supervised area, the safety system will immediately react thereto and activate the signal means 17 warning the operator that a very dangerous situation is about to arise. If the glove is then immediately removed from the area, it is possible to continue working with the band saw as hitherto, but if the glove is taken further into the supervised area in such a manner that for example more than 1 cm-*-*, for instance 2 cm-*--, of the glove is within the supervised area, the safety system will immediately react by instantaneously activating -the blocking or cutting means 16. The system is adapted in such a manner that the time of reaction is less than 1 msec for 2 cm.2 flourescent material in the supervised area. The logical circuit 20 is moreover adapted in such a manner that the motor 5 of the band saw cannot be started before a glove 15 with flourescent material of the correct type has been placed within the supervised area and then removed therefrom. This will ensure that it is not possible to start working with the machine without the operator having remembered to put on protective gloves. The electrical circuit shown in Fig. 2 of the drawing may be designed in many different ways using generally known techniques. The electrical circuit may be designed either by analog or digital techniques by putting together known components.

Claims: PATENT CLAIMS 1. Safety system for use in connection with working machines and apparatuses, particularly for warning signalling and for stopping or blocking of the machine or the apparatus when an object (15) enters a supervised area (13, 14), c h a r a c t e r i s e d in comprising a) a lighting means (6,7) lighting the supervised area (13,14) with modulated light with a modulation frequency of 1-50 kHz, b) a detecting means comprising fluorescent material placed on the object (15) which material can be excited by the modulated light, c) an optical/electrical system (8) directed towards the supervised area (13,14) and adapted to detect electromagnetic waves of a certain wave length and modulated with the said modulation frequency, and d) an electrial circuit (Fig. 2) giving a warning signal or stops or blocks the machine or apparatus when the optical/electrical system (8) detects an object (15) in the supervised area (13,14). 2. Safety system according to claim 1, c h a r a c t e r i s e d in that the optical/electrical system (8) comprises a detector (12) for detecting excited radiation from the flourescent material of the object (5) where in the beam path in front of the detector there is arranged an optical band-pass filter (11). 3. Safety system according to claim 1 or 2, c h a r a c t e r i s e d in that in the beam path in front of the detector (12) there is further arranged a circular mask (10) so that the supervised area (13,14) becomes circular and in that there is used a matted working plane (1) . 4. Safety system according to any one of claims 1-3, c h a r a c t e r i s e d in that the object (15) is a working glove to which there has been applied or put on a flourescent material. 5. Safety system according to any one of claims 1-4, c h a r a c t e r i s e d in that the lighting means comprises an ultraviolet lamp (7) preferably in the shape of a flourescent tube, that a fluorescent material emitting light with a wave length of 400-450 nm has been applied to the object (15), and that the band-pass filter of the optical/electrical system (8) comprises an optical filter with a pass band of 600-650 nm, preferably about 630 nm, and that the optical system comprises necessary lens systems (9) and that the detector (12) is a solar cell of 1 cm***-. 6. Safety system according to any one of claims 1-5 for supervising a high-speed band saw (2,3,4) where the blade (2) is carried through a working plane (1), c h a r a c t e r i s e d in that the saw blade (2) is situated in the centre of the supervised area (13,14) and that there are one or more means (16) for instantaneous blocking or cutting of the blade when an object (15) enters the supervised area. 7. Safety system according to claim 1 or 6, c h a r a c t e r i s e d in comprising a signal means (17) which is activated before the blocking or cutting means (16) is activated. 8. Safety system according to any one of claims 1-7, c h a r a c t e r i s e d in that the electrical circuit (Fig. 2) comprises logic circuits (20) preventing starting of the driving motor (5) of the working machine if the lighting means (6,7) is in an off position or if the object (15) has not been within the supervised area and subsequently removed therefrom.

Inventors: HOEGSHOLM ANDERS, HOEGSHOLM, ANDERS
Applicants: NORTHERN FOOD LINE MACHINES K, NORFO NORTHERN FOOD-LINE
Application year: 1986
Main classification: F16P3
IPC codes: B27B13, F16P3, G01V8, H03K17