Chapter 2 Power presses or shear machines
Section 2 Safety devices
The safety device of the press or shear machine shall have one of the following functions:
1. Interlocked guard safety device: it can prevent a body part intervening to the hazard zone while the slider in closing-action.
2. Two-hand control safety device:
(1) Safe-single-stroke safety device: It can make the slider stopped before two hands releasing from start buttons, control levers or other control devices(hereinafter referred to as the operating portion) reach the hazard zone.
(2) Two-hand start safety device: It can prevent two hands releasing from the operating portion to reach the hazard zone while the slider in closing- action.
3. Sensing safety device: it can make the slider stopped if a body part is closing to the hazard zone while the slider in closing- action .
4. Pull-back or push-out safety device: it can follow the slider moving to withdraw or push a body part out from the hazard zone.
The safety devices referred in the preceding subparagraphs shall be not easy impairment or alteration.
The safety device of the press or shear machine shall meet the following provisions:
1. Adapting to the type of the press or shear machine, the capacity, the numbers of stroke per minute, stroke and operating ways.
2. Adapting to the stop performance of each type of the press or shear machine for a two-hand control safety device or a sensing safety device respectively.
The distance between the operating portion of the slider and the hazard zone, or the distance between the sensing zone and the hazard zone, that related to the stop performance of the two-hand control safety device or the sensing safety device set in the preceding Aticle subparagraph 2, shall be over the value calculated by the following equations separately :
1. Two-hand control safety device for safe- single -stroke:
D: the safety distance, in millimeters.
Tl:the time that hands releasing from the operating portion of that device to the starting action of the protective stop mechanism, in millimeters.
Ts:the time that the protective stop mechanism starting action to the slider stopping, in milliseconds.
2. Two-hand start safety device:
D = 1.6Tm
D:the safety distance, in millimeters.
Tm:the maximum time that hands releasing from the operating portion to the slider reaching the lower dead center , in millimeters and calculated by the following formula,
Tm =(1/2 + 1 / numbers of clutch engagement) × the time required for one revolution of the crankshaft)
3. Photoelectric safety device:
D:the safety distance, in millimeters.
Tl:the time that fingers intervening the sensing zone of that device to the starting of the protective stop mechanism, in millimeters.
Ts:the time that the protective stop mechanism starting action to the slider stopping, in milliseconds.
C:an additional distance, in millimeters, and the adopted value as shown in the following table:
│continuous shading width: mm│additional distance C: mm │
│below 30 │0 │
│over 30，below 35 │200 │
│over 35，below 45 │300 │
│over 45， below50 │400 │
The interlocked guard safety device shall meet the following provisions:
1. Except in an inching state, it has a construction that the slider cannot be closed until the guard device is closed and it cannot be opened while the slider in closing- action.
2. Limit switches that enact the slider can prevent a body part, materials or others not belong to the protective device contacting.
The two-hand control safety device shall meet the following provisions:
1. It has a safe- single- stroke safety device, except the press or shear machine with single- stroke- single- stop mechanism and a two-hand start safety device.
2. It has a safe- single-stroke safety device to make the slider stopped when released hands having a risk to reach the hazard zone.
3. It has a two-hand start safety device to make the slider to reach the lower dead center before released hands intervening to the hazard zone.
4. It has a construction that the operating portion for activating the slider cannot be activated except the different of operating time between two hands is less than 0.5 second.
5. It has a construction that the press or shear machine cannot be restarted if two hands do not release from the single stroke operating portion.
6. The distance between one button outside and the other button outside is at least 300 millimeters. It can be reduced for the buttons with covers, baffles, barriers or others having the same safety function to prevent them being operated by a hand or other part of the body.
7. If the buttons are set in boxes, they cannot protrude the button-box surface.
8. If the buttons are built into the body of the press or shear machine , they cannot protrude the surface of the machine.
The sensing safety device shall be a photoelectric safety device, a photoelectric safety device with start control function, a laser-sensing safety device or others with equal or over performance.
The constructure and performances of the photoelectric safety device shall comply with the international standard IEC 61496 series or other equivalents.
The photoelectric safety device shall comply with the following provisions:
1. The photoelectric safety device for the press or shear machine can make the slider stopped when detecting the light cut off by a body part.
2. The photoelectric safety device for the press machine can effectively act to prevent hazard from the slider in required distance including adjustment length and stroke(hereinafter referred to as the protective height).
3. The optical-axis of the emitter and receiver shall be over two and can detect the minimum diameter of a shading rod( hereinafter referred to as the continuous shading width ) being below 50 millimeters when it is placed anywhere in the protective height referred in the preceding subparagraph . The continuous shading width shall be less than 30 millimeters for that has a function of start control.
4. The optical-axis height from the desktop of the shear machine shall be less than 0.67 times of the horizontal distance between the vertical plane including the optical- axis and the hazard zone. The height could be concerned as 180 millimeters when over 180 millimeters.
5. The emitter and receiver reffered in the preceding subparagraph shall have at least one another optical-axis between the former optical-axis and the cutter when the horizontal distance from the vertical plane including the former optical-axis to the hazard zone is over 270 millimeters.
6. The photoelectric safety device for the press or shear machine has a construction that the light from the emitter can only reach its corresponding receiver or reflector, and cannot be sensed by other sensors. It is unrestricted for that not affecting the slider motion even being other light sensed.
If the distance between the optical- axis of a detecting mechanism and the front edge of a bolster is enough to be intervened by a body part, the press or shear machine with a photoelectric safety device shall have a safety fence or a middle optical-axis to prevent intervening.
The photoelectric safety device for the press machine with a material feeder can make that feeder detecting invalidated without restricting by Article 12, subparagraph 2 if the emitter and receiver of that safety device complies with the provisions in subparagraph as follows:
1. The switching to make that detecting invalidated, shall be used by a key , software or others for each optical-axis.
2. When changing a material feeder device, the slider cannot be activated except the detecting invalidated in the preceding subparagraph is reset.
3. When the material feeder is taken away, it has a construction immediately to restore the effective action that the emitter and receiver within the required length can prevent the hazard of the slider motion.
The photoelectric safety device with a start control function shall have a construction to make the slider stopped when it detect a body part cutting the light.
The press or shear machine using a photoelectric safety device with start control function, shall meet the following provisions:
1. The distance of the bolster surface from the ground is above 750 millimeters but it is unrestricted for having a safety fence between the bolster surface and the lower end of the emitter and receiver.
2. The depth of the bolster is less than1,000 millimeters.
3. Stroke is less than 600 millimeters but it is unstricted for the press or shear machine having a safety fence and the protective height of the emitter and receiver being less than 600 millimeters.
4. The stop- point-setting of the over- fix-point monitor for a crankshaft press machine is within 15 degrees.
The emitter and receiver of the photoelectric safety device with a start control function shall have the construction not easily to be disassembled or to be changed its mounting place.
When using the photoelectric safety device with the start control function, it shall be able to prevent the slider moving unexpectly and meet the following provisions:
1. The photoelectric safety device with the start control function shall use a key to select the hazard-preventive function.
2. It shall have the construction to finish the necessary start preparing operation before making the slider moved.
3. It shall have the construction to finish the necessary start preparing operation related in the preceding subparagraph if the slider do not move within 30 seconds.
The photoelectric safety device with the start control function corresponds with the application of Article 8 and Article 12 provisions. However, the additional safety distance for that device set in Article 8 is reduced as following table:
│Continuous shading width: millimeters │Additional distance │
│ │C: millimeters │
│less than 14 │0 │
│more than 14 and less than 20 │80 │
│more than 20 and less than 30 │130 │
A laser-sensitive safety device for a press brake shall have the following performances:
1. A construction can make the slider stopped when it detects a body part shading the light and the slider has a risk to catch the body.
2. A construction can make the slider speed reduced to be less than 10 millimeters(hereinafter referred to as the low closing speed) when it detects a body part or a workpiece shading the light or the slider is asked to keep moving in closing action even the slider having reached a set position.
A laser-sensing safety device can be applied to a press brake compling with the following provisions:
1. A construction can adjust the slider to the low closing speed when it is in closing move.
2. A construction can make the slider not activated in the low closing speed except it is operated at the operating portion.
The detecting construction of the laser-sensitive safety device for a press brake shall have the following performances:
1. The emitter and receiver is provided at the location where a body part may be caught by the slider. If the slider of the press brake is a dropping type, the construction of the detector has the motion in conjunction with the slider motion .
2. A construction can make detecting function invalidated while the slider is in closing motion and the low closing speed.
The pull-back safety device shall meet the following provisions:
1. If it is set by traction cables, the cables is able to adjust the amount of traction and that is more than a half of the bolster depth.
2. The cable material is a synthetic fiber with the diameter more than 4 millimeters. In adjustable metal parts fitted state, the breaking load of it is over 150 kgf(1.5 kN).
3. The toggle- transfer belt is made of leather or other equivalent material and the cable connection portion can withstand more than 50kgf( 0.49kN) static load.
The push-out safety device shall meet the following provisions:
1. It has a construction that the length and the amplitude of a push-out arm are adjustable.
2. The push-out arm sets a hand- guard plate to ensure the hand safety when the slider moving.
3. Sizes of the hand- guard plate in the preceding subparagraph are as follows:
(1) the width: more than one half width of a die but it being concerned as 100 millimeters for that less than 200 milimeters.
(2) the height: more than the stroke but it being concerned as 300 milimeters for the stroke more than 300 milimeters.
(3) the amplitude of the push-out arm: more than the die width.
4. The push-out arm and the hand- guard plate have the performance mitigating the impact when they contact with hands or a body part.
The press machine cannot provide the push-out safety device except that complies with the following provisions:
1. The construction is a positive clutch type and the operating portion to start the slider shall be controlled by two hands.
2. The stroke must be more than 40 millimeters and less than the protect-plate width.
3. Strokes per minute must be less than 120.
The press machine with the protective stop mechanism operated by a foot type cannot use a push-out safety device except it use one of safety devices set in Article 6 subparagraph 1 through 3.
Mechanical parts, electrical parts, wires, switches or other parts for the safety device of the press or shear machine shall meet the following provisions:
1. The body, the linkage material, the lever and other major mechanical parts have sufficient strength.
2. Linking parts:
(1) Their materials comply with the national standard CNS 3828 “mechanical-structure-usage carbon-steel material” S45C or others having equivalent or more mechanical properties.
(2) The surface of linking parts is treated by quenching and tempering, and their hardness must be above 45 to 50 in Rockwell C scale.
3. Wire cables:
(1) They comply with the national standard CNS 10000 “machinery-control-usage cable” or thers having equivalent or more mechanical properties.
(2) They are tightly fixed on the slider, levers and others with clips, clamps and so forth.
4. Preventing loosing shall be applied to bolts, nuts and others on the safety deice that may lead the device being malfunction or fitting parts falling off. Preventing falling off shall be applied to pins on the hinge portion too.
5. Relays, limit switches or other major electrical parts shall have sufficient strength and durability to ensure safety device performances.
6. The safety device with electrical circuits shall have indicators to display its actuated states, relay malfunction or failure of other circuits.
7. Mounting portions for relays, transistors, capacitors, resistors or other electrical parts have vibration-proof performance.
8. Circuits in safety device have the performance to prevent the slider accidental action when relays, limit switches or others are failure or power-failure.
9. Operating voltage for the electrical circuit shall be less than 160 volts.
10. External wires shall meet the national standard CNS 6556 “600V PVC insulated and coated light weight cables” or have equivalent or more insulation, oil-resistance, strength and durability.
(1) For a button-switching type of the safety device, it shall have a construction to let buttons selecting switching positions respectively.
(2) It can exactly keep holding at each switching position.
(3) It is clearly to mark the state of the safety device related to each switch position.