Safety device for stopping the bale plucking operation
SUMMARY OF THE INVENTION 
     The present invention relates to a safety device for stopping the bale plucking operation of a bale plucker when metallic substances contained in a bale are detected during the operation. The term &#34;bale plucker&#34; means an apparatus for plucking fiber tufts from a fiber bale. 
     It is well known that a highly compressed block of fiber material is not suitable for processing in the opening and picking process in a spinning factory. Consequently, a bale plucker is conventionally used to pluck fiber tufts from a highly compressed fiber bale before supplying the material fibers to the opening and picking process. However, according to our experience, there is some possibility that a highly compressed fiber bale will contain hard substances such as metallic substances and these hard substances should be removed from the fiber tufts before supplying the tufts to the opening and picking process. In the conventional opening and picking process, a permanent magnet is disposed on a wall of a transportation conduit or hopper, so as to pick up the metallic substances contained in the fibers bales, by the magnetic force thereof, when the fiber tufts containing the metallic substances are carried along the wall of the transportation conduit or hopper. However, in the bale plucking operation, if the above-mentioned metallic substances meet the blades of the plucking roller of the bale plucker, the blades are often broken or the impact of the metallic substances against the blades strikes a spark so that a part of the fiber material is burned. Consequently, even though the above-mentioned magnetic device is utilized, the above-mentioned troubles still remain and should be eliminated. 
     The principal object of the present invention is to provide a safety device for stopping the bale plucking operation of the bale plucker by detecting the existence of metallic material in the fiber bale before permitting the plucking of the fiber bale by the blades of the plucking roller. 
     To attain the above-mentioned object, in the present invention the safety device for stopping the operation of the bale plucker comprises means for supplying a fiber bale to a bale plucking device, a driving mechanism for turning the bale plucking device so that it plucks fiber tufts from the fiber bale carried by the supplying means, means for detecting the existence of metallic material such as pieces of iron, aluminum, etc., contained in the fiber bale and, electrical control means for stopping the operation of the supply means and the mechanism for driving the plucking device before the fiber bale is carried to the working position of the plucking device. For the sake of simplifying the following explanation of the present invention, the safety device for stopping the plucking operation of the bale plucker is hereinafter simply referred to as &#34;safety device&#34;. 
    
    
     BRIEF EXPLANATION OF THE DRAWINGS 
     FIG. 1 is a schematic elevational view of a bale plucker equipped with a safety device according to the present invention; 
     FIG. 2 is a schematic elevational view of a part of the bale plucker shown in FIG. 1; 
     FIG. 3 is a schematic plan view of the bale plucker shown in FIG. 1, and; 
     FIGS. 4 and 5 are diagrams of electric circuits for controlling the operation of the bale plucker shown in FIG. 1. 
    
    
     DETAILED EXPLANATION OF THE INVENTION 
     The construction and function of the safety device according to the present invention are hereinafter illustrated in detail with reference to FIGS. 1, 2 and 3. The bale plucker shown in FIGS. 1, 2 and 3 comprises a pair of endless belts 1 and 2 which carry a frame 3 for supporting a fiber bale A toward a plucking roller 4 disposed in an intermediate position between the endless belts 1 and 2. The endless belt 1 is mounted on a pair of cylindrical rollers 5 and 6, and a pulley 8 is rigidly mounted on a shaft of the roller 5 while a pulley 9 is rigidly mounted on a shaft of a motor 7. The pulley 8 is connected to the pulley 9 by way of an endless belt 10 so that the cylindrical roller 5 is driven by the motor 7. At the other end of the shaft of the roller 5, there is provided a pulley 11 rigidly mounted thereon (FIG. 3). The endless belt 2 is mounted on a pair of cylindrical rollers 12 and 13, and the roller 12 is driven by power transmitted from the pulley 11 by an endless belt 14. That is, another pulley (not shown) is rigidly mounted on a shaft of the cylindrical roller 12 and the roller 12 is driven by the pulley 11 by way of the endless belt 14 (FIG. 1). The plucking roller 4 is provided with a pulley 15 rigidly mounted on the shaft of the plucking roller 4 and the pulley 15 is driven by a main motor 16 by way of a pulley 17 secured on the shaft of the motor 16 and an endless belt 18 which connects the pulleys 15 and 17. 
     An endless belt 19 for temporarily supporting a fiber bale is disposed in aligned condition to the endless belt conveyers 1 and 2 at a position adjacently outside the endless belt 1 as shown in FIGS. 2 and 3. A driving cylindrical roller 20, which drives the endless belt 19, is driven by the cylindrical roller 6 by way of a power transmission mechanism comprising a clutch 21, a pulley 22, which is capable of being driven by the clutch 21, a pulley 23 rigidly mounted on the shaft of the roller 20 and an endless belt 24 which transmits the driving power of the pulley 22 to the pulley 23. A fiber bale supply conveyer 25 is disposed in aligned condition to the endless conveyer belts 1 and 2 at a position adjacently outside the conveyer belt 2, and this supply conveyer 25 is driven by a motor 26 as shown in FIG. 1. 
     A pair of limit switches 27 and 28 are disposed to a machine frame (not shown) at terminal end positions of reciprocal carrying passage of the conveyer belts 1 and 2. These limit switches 27, 28 are conventional non-contact type limit switches which detect the arrival of the supporting frame 3 at the respective carrying terminals. These limit switches 27, 28 issue electrical signals which change the rotational direction of the motor 7, by way of a reversible relay (not shown) which connects the motor 7 to an electric source, in counterclockwise or clockwise direction, thus causing the fiber bale to reciprocate back and forth over the plucking roller 4. 
     Means for detecting the existence of a metallic material in the fiber bale A is disposed in a space between the parallel inside surfaces of the conveyer belt 1 mounted on the cylindrical rollers 5 and 6. The above-mentioned detecting means 29 comprises a plurality of detecting elements 29a (FIG. 3) so as to perform the metals-detecting function throughout the entire width of the conveyer belt 1. The conventional resonant type metal sensor or magnetic type metal sensor is preferably utilized for the above-mentioned detecting element 29a. These metal sensors operate as follows: that is, in the case of utilizing a resonant type metal sensor provided with a variable frequency oscillator, when a metallic substance such as iron comes into an electromagnetic field which is created by the variable frequency oscillator, the oscillating frequency of the oscillator changes so that the approach of the metallic substance to the sensor can be detected. On the other hand, in the case of a magnetic type metal sensor, when a metallic substance such as iron comes into a gap located in a magnetic path of the sensor, the magnetic reluctance of the magnetic path changes. Therefore, the magnetic reluctance can be used as a means for detecting the presence of the metallic substance coming into the magnetic field of the sensor. The detecting elements 29a are positioned in such a manner that they are capable of detecting the existence of the metallic substance contained in the fiber bale A within an effective thickness of 200 mm of fiber bale A as measured from the carrying surface of the conveyer belt 1. 
     When the detecting means 29 detects a metallic substance in the fiber bale A, the detecting means 29 issues a signal to stop the motors 7 and 16. The operator then puts a provisional mark on the fiber bale A at a position corresponding to the position where the detecting means 29 is actuated. Next, the operator pushes a switch PB 3 , so as to turn the motor 7 toward a direction for displacing the fiber bale to the conveyer belt 19 while the clutch 21 is also actuated by the switch PB 3  so that the fiber bale A is transferred to the supporting belt 19. When the marked portion of the fiber bale A arrives at the free space between the conveyer belt 2 and the supporting belt 19, the operator releases the PB 3  switch (refer to FIG. 4) so as to again stop the motor 7. In this condition, the operator utilizes a portable detecting means 30 to find the metallic substance detected by the above-mentioned detecting means 29. The detected metallic substance is extracted from the fiber bale A by manually plucking the fiber bale utilizing a hand plucking device. 
     When the metallic substance is removed from the fiber bale A, the operator pushes a starting button switch (PB 2 ) (refer to FIG. 4) so as to simultaneously energize an electromagnetic relay MS1 and an electromagnetic relay MS2, which respectively cause the motors 16 and 7 to commence driving in their normal running directions. With the motor 7 being driven in its normal running direction the fiber bale A is transferred to the conveyer belts 1 and 2. 
     In the above-mentioned embodiment, the detecting direction of the detecting device 29, for the metallic substances contained in the fiber bale A, is upward from the detecting device 29, however, it is capable of detecting the metallic substance contained in the fiber bale A along a horizontal direction from a detecting device which is disposed on the side of the displacing passage of the fiber bale A, instead of the above-mentioned direction of detection. 
     The construction and function of the electric control circuit utilized in the above-mentioned embodiment is hereinafter explained in detail with reference to FIGS. 4 and 5. 
     When the starting button switch PB 2  is operated, the electromagnetic relay MS1 is energized. Then the contactor MS 1-a  in FIG. 5 becomes conductive and the electric motor 16 in FIG. 5 starts to rotate in the normal direction. At the same time the relay MS1 is held in an energized condition through the contactor MS 1-b  whether the switch PB 2  is released or not. In case the limit switch LS 1  (corresponding to reference number 28 in FIG. 1) is not operated, that is the switch LS 1  is conductive, the electromagnetic relay MS2 is energized. In this case the electric motor 7 in FIG. 5 is energized to rotate in the normal direction through the contactor MS 2-a  in FIG. 5, which is now conductive by means of the relay MS2, and the motor 7 moves the bale A in the leftward direction in FIG. 1 by means of conveyer belts 1 and 2. 
     When the switch LS 1  is operated by the bale A, that is the switch LS 1  is switched to being non-conductive, the relay MS2 is not energized but the relay MS3 is energized through the contactor MS 2-b  which is now conductive by means of the relay MS2. Then the motor 7 is energized to rotate in the reverse direction through the contactor MS 3-a  in FIG. 5 and the bale A is moved in the rightward direction in FIG. 1. At the same time the relay MS3 is held in an energized condition through the contactor MS 3-c , even though the switch LS 1  is released, until the limit switch LS 2  becomes non-conductive. 
     When the switch LS 2  (corresponding to reference number 27 in FIG. 1) is operated by the bale A, that is the switch LS 2  is switched to being non-conductive, the relay MS3 is not energized but the relay MS2 is energized through MS 3-b  which is now conductive by means of said relay MS3. Consequently the motor 7 starts to rotate in the normal direction again, through the contactor MS 2-a  which is now conductive and the bale A is moved in the leftward direction in FIG. 1 again. 
     When the detecting means 29 detects metallic substance, the detecting means 29 energizes the electromagnetic relay CR1 and the contactor CR 1  becomes non-conductive, whereby the relay MS1 is not energized. Accordingly, the motor 16 stops rotating because the contactor MS 1-a  becomes non-conductive. In addition the motor 7 also stops rotating. This is because the contactor MS 1-b  is now non-conductive and, accordingly, the relay MS2 is not energized and, therefore, the contactor MS 2-a  is not conductive. 
     When the push-button switch PB 3  is operated, the electromagnetic relay CR2 is energized and the contactor CR 2-a  becomes conductive and, accordingly, the relay MS3 is energized. 
     The motor 7 is then energized to rotate in the reverse direction through the contactor MS 3-a . On the other hand, the switch PB 3  also energizes the exciting coils 31 and, accordingly, the electromagnetic clutch 21 in FIG. 3 becomes operative. Then the conveyer belt 19 in FIG. 2 is driven together with the conveyer belt 1. 
     When the switch PB 2  is operated (the bale A is now located on the conveyer belt 19), the relay MS1 is energized and the motor 16 is energized, through the contactor MS 1-a  to rotate in normal direction again. At the same time, the relay MS2 is also energized through the contactor MS 1-b , the switch LS 1  and the contactor MS 3-b  and, accordingly, the motor 7 is also energized through the contactor MS 2-a , to rotate in the normal direction. 
     The bale A is then moved from the conveyer belt 19 to the conveyer belts 1 and 2, and normal operation is begun again. In FIGS. 4 and 5, OCR1 and OCR2 are conventional over current relays. 
     As mentioned above, in the safety device according to the present invention, the metallic substances like and iron piece contained in the fiber bale A is detected by the detecting device 29 before the fiber bale A is carried to the working position of the plucking roller 4 and the connections between the electric source and the motors 7 and 16 are instantly cut by the signal issued from the detecting device 29. Consequently, the possible impact of the metallic substance contained in the fiber bale A by the blades of the plucking roller 4 can be previously prevented so that the purpose of the present invention can be satisfactorily attained.