Patent Publication Number: US-2021189774-A1

Title: Safety door device and safety door locking method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-229022 filed on Dec. 19, 2019, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a safety door device used to ensure the safety of work and a method of locking the safety door. 
     Description of the Related Art 
     A machine may be equipped with a safety door in order to ensure the safety of work (for example, refer to Japanese Lad-Open Patent Publication No. 2010-005759). Machines such as machine tools, injection molding machines, press machines, etc. have work areas in which cutting tools or molds operate, and it would be dangerous, for example if a worker puts his or her hand into such an area. The safety door closes the work area while the machine is in operation, so as to ensure the safety of work. That is, a locking mechanism operates to lock the safety door when the safety door is closed, and the operation of the machine is started after that. 
     SUMMARY OF THE INVENTION 
     However, if a safety door is closed rapidly, the locking mechanism etc. will be subjected to an impact as the safety door bounces and may be damaged. An object of the present invention is to provide a safety door device and safety door locking method that prevents damage when the safety door is closed rapidly. 
     A safety door device according to an aspect includes: a full closing detector configured to detect that a safety door has fully closed from an opened state; a locking mechanism configured to lock the safety door so that the safety door does not open; a measurement unit configured to measure a travel acceleration, a travel speed, or a travel time when the safety door closes; and a control unit configured to, when the safety door is detected to be closed, control the locking mechanism to lock the safety door, the control unit being further configured not to cause the safety door to be locked if the travel acceleration or the travel speed is greater than a first threshold, or if the travel time is shorter than a second threshold. 
     The present invention thus provides a safety door device and safety door locking method that prevents damage when the safety door is closed rapidly. 
     The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which a preferred embodiment of the present invention is shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a machine configuration of a safety-door-equipped machine device according to an embodiment; 
         FIG. 2  is a block diagram illustrating a control configuration of the safety-door-equipped machine device; 
         FIGS. 3A, 3B and 30  are schematic diagrams illustrating a key switch in detail; and 
         FIG. 4  is a flowchart showing an example of an operation procedure of the safety-door-equipped machine device. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A safety-door-equipped machine device  10  and a method of locking a safety door  30  according to an embodiment will be described below.  FIGS. 1 and 2  respectively illustrate a machine configuration and a control configuration of the safety-door-equipped machine device  10  of the embodiment. As shown in  FIG. 1 , the safety-door-equipped machine device  10  has a machine device body (not shown) that is installed within a cover  20 , and an opening  22  thereof is opened and closed by the safety door  30 . The safety-door-equipped machine device  10  is further provided with a safety door device  12  (see  FIG. 2 ), which opens, closes, and locks the safety door  30  and controls these operations. The safety door device  12  includes a full opening detector  26 , a key  34 , an acceleration sensor  36 , a key switch  40  (a full closing detector  44 , a locking mechanism  46 ), a control unit  50 , and a notification unit  52 . 
     The full opening detector  26  is a switch of contact type or proximity type that is provided on the cover  20 , for example, and is situated in proximity to or contact with the safety door  30  when the safety door  30  is fully open and detects that the safety door  30  is fully open. When the state of detection by the full opening detector  26  changes from detection of full opening to non-detection thereof, it means that the safety door  3 C has started moving (detection of the beginning of movement). 
     The key  34  is held so as to protrude from the safety door  30  (see  FIG. 1 ). When the safety door  30  is closed, the key  34  is inserted into a key insertion hole  42  of the key switch  40 , and the key  34  is pulled out from the key insertion hole  42  when the safety door  30  is opened. 
     The acceleration sensor  36  (measurement unit) is provided on the safety door  20  and detects a travel acceleration α that is applied to the safety door  30 . 
     The key switch  40  (the full closing detector  44 , locking mechanism  46 ) detects full closing of the safety door  30  and locks the safety door  30  by using the key  34 . 
       FIGS. 3A to 3C  illustrate an internal configuration of the key switch  40 .  FIGS. 3A to 3C  respectively illustrate the states of the key switch  40  (1) before the key  34  is inserted (after the key  34  is pulled out), (2) after the key  34  is inserted, (3) after the key  34  is inserted and locked. 
     The full closing detector  44  is a switch of contact type or proximity type, for example, and is situated in proximity to or contact with the key  34  when the safety door  30  is fully closed (when the key  34  is completely inserted in the key insertion hole  42 : see  FIG. 3B ) and detects that the safety door  30  is fully closed. 
     The locking mechanism  46  is an electromagnetic solenoid, for example, which displaces a locking member  46   a  downward when supplied with electricity, and displaces the locking member  46   a  upward with a biasing member such as a spring, when not supplied with electricity. When the safety, door  30  is fully closed (see  FIG. 3B ), the locking mechanism  46  is supplied with electricity and then the locking member  46   a  engages with an engagement portion  341  of the key  34  (see  FIG. 3C ). In this way, the locking mechanism  46  can switch the safety door  30  between a locked state (the safety door  30  cannot be opened) and an unlocked state (the safety door  30  can be opened) depending on whether it is supplied with electricity or not. 
     The control unit  50  controls the key switch  40  to protect the safety door device  12  if the safety door  30  closes rapidly. This operation will be described later in detail. The control unit  50  is formed of hardware (CPU: Central Processing Unit) and software, for example, where a control unit of the machine device body may serve also as the control unit  50 . 
     The notification unit  52  is a display unit (e.g., a liquid crystal display), for example, which displays a warning message if the safety door  30  closes rapidly. The notification unit  52  may include an audio output device for outputting sound (e.g., a speaker) in place of, or in addition to, the display unit, in which case the audio output device may output a warning message with sound. 
     (Details of Control Unit  50 ) 
     The details of the control unit  50  will be described below. 
     When full closing of the safety door  30  is detected, the control unit  50  controls the locking mechanism  46  to lock the safety door  30 . 
     However, even if full closing of the safety door  30  is detected, if the travel acceleration α is greater than a threshold α1 (first threshold), then the, control unit  50  does not cause the safety door  30  to be locked. In this case, the control unit  50  generates a warning signal. On the basis of this warning signal, the notification unit  52  generates a warning message with an image or sound. 
     On the other hand, if the travel acceleration α is equal to or less than the threshold α1 (first threshold), then the control unit  50  controls the locking mechanism  46  to lock the safety door  30  when full closing of the safety door  30  is detected. 
       FIG. 4  is a flowchart showing an example of the operation procedure of the safety-door-equipped machine device  10 . The operation procedure of the safety-door-equipped machine device  10  will be described referring to  FIG. 4 . 
     An operation of closing the safety door  30  is started (step S 1 ). For example, the safety door  30  is moved manually in the closing direction (to the right in  FIG. 1  herein). Alternatively, the control unit  50  may move the safety door  30  by controlling a motor. 
     The acceleration sensor  36  (measurement unit) measures the travel acceleration α (step S 2 ), and the control unit  50  determines whether the travel acceleration α is greater than the threshold α1 (step S 3 ). If the travel acceleration α is greater than the threshold α1, the control unit  50  generates a warning signal (step S 4 ). 
     Subsequently, the key  34  is inserted in the key insertion hole  42  as the safety door  30  moves in the closing direction. As a result, the full closing detector  44  comes in an ON state and detects full closing of the safety door  30 . 
     If the travel acceleration α is equal to or less than the threshold α1, the control unit  50  supplies the locking mechanism  46  with electricity upon detection of full closing to thereby lock the safety door  30  (step S 5 ). On the other hand, if the travel acceleration α is greater than the threshold α1, the control unit  50  does not cause the safety door  30  to be locked even if full closing is detected. For the sake of safety, even if the travel acceleration α is equal to or less than the threshold α1, the control unit  50  may lock the safety door  30  not immediately after the detection of full closing of the safety door  30  but. after a given time (e.g., 0.1 to 1 second) has passed after the detection of full closing. 
     As has been described above, if the travel acceleration α of the safety door  30  is equal to or less than the threshold α1, the safety-door-equipped machine device  10  locks the safety door  30  when the safety door  30  is fully closed. However, the safety-door-equipped machine device  10  does not lock the safety door  30  if the travel acceleration α is greater than the threshold α1. This reduces the possibility of damage to the safety door device  12  which might be caused by an impact when the safety door  30  is rapidly closed and bounces. 
     If the travel acceleration α is greater than the threshold α1, the safety door device  12  may be damaged by an impact of bouncing of the safety door  30 . That is, locking the safety door  30  when the safety door  30  is fully closed may damage the key  34  or the locking mechanism  46  irrespective of the travel acceleration α. 
     (First Modification) 
     A first modification will now be described. The embodiment above controls the locking of the safety door  30  by using the travel acceleration α. The first modification controls the locking of the safety door  30  using a travel time T of the safety door  30 . 
     The travel time T can be measured as a time T from the beginning of movement of the safety door  30  to when full closing of the safety door  30  is detected (detection of full closing). This time measurement can be performed by the control unit  50 . That is, part of the control unit  50  can function as a time measuring unit for measuring the time T to when full closing of the safety door  30  is detected (detection of full closing). 
     The beginning of movement of the safety door  30  can be determined by the following methods 1) and 2), for example. 
     1) Detection of Acceleration 
     The beginning of movement of the safety door  30  can be determined by the acceleration sensor  36  detecting a value of the acceleration α that exceeds a detection error (threshold α2). That is, the control unit  50  compares the acceleration α detected by the acceleration sensor  36  with the threshold α2, and determines that the safety door  30  has started moving if the acceleration α exceeds the threshold α2. The threshold α2 that is used to determine whether the safety door  30  has started moving is smaller than the threshold α1 that is used to determine whether to lock the safety door  30 . 
     2) Non-detection of Full Opening 
     The beginning of movement of the safety door  30  can be determined also by the full opening detector  26  losing detection of full opening of the safety door  30  (non-detection of full opening). That is, the control unit  50  determines that the state of the full opening detector  26  has changed from detection of full opening to non-detection thereof. 
     For example, the control unit  50  can obtain the travel time T as a difference between a time t0 of the beginning of movement of the safety door  30  and a time t1 of detection of full closing of the safety door  30 . 
         T=t 1 −t 0   equation (1)
 
     Alternatively, the control unit  50  may directly obtain the travel time T without obtaining the individual times t0and t1, for example by starting a timer when a beginning of movement is detected and stopping the timer when full closing is detected. 
     Now, an operation procedure of the safety-door-equipped machine device  10  of the first modification will be described. The safety-door-equipped machine device  10  of the first modification operates similarly to the safety-door-equipped machine device  10  of the embodiment, except that it uses the travel time T in place of the travel acceleration α to make the determination as to whether to lock. Accordingly, the difference will mainly be described referring to  FIG. 4 . 
     The first modification differs from the embodiment at steps S 2 , S 3 , where detection and determination are made with the travel time T instead of the travel acceleration α. 
     As has been explained above, the control unit  50  obtains the travel time T as the time T from the beginning of movement of the safety doer  30  to when full closing of the safety door  30  is detected (detection of full closing (step S 2 )). 
     The control unit  50  determines whether the travel time T is smaller than a threshold T1 (second threshold: T&lt;T1? (step S 3 )). If the travel time T is smaller than the threshold T1 (second threshold), the control unit  50  generates a warning signal (step S 4 ), and does not cause the safety door  30  to be locked even if full closing is detected. If the travel time T is equal to or greater than the threshold T1 (second threshold), then the control unit  50  causes the safety door  30  to be locked when full closing is detected (or when a given time has passed after the detection (step S 5 )). 
     (Second Modification) 
     Now, a second modification will be described. The implementations above have used the travel acceleration α or travel time T to control the locking of the safety door  30 . The second modification uses a travel speed V of the safety door  30  to control the locking of the safety door  30 . 
     The travel speed V can be obtained by the following methods 1) and 2), for example. 
     1) Integration of Acceleration 
     The control unit  50  can calculate the travel speed V(t) of the safety door  30  by integrating the travel acceleration α(t) detected by the acceleration sensor  36  with respect to time (integration with respect to time t). 
       V( t )=∫α( t )* dt    equation (2)
 
     In this case, the control unit  50  can calculate variation of the travel speed V(t) over time. 
     2) Calculation from Travel Time T 
     The control unit  50  can obtain the travel speed V by dividing a travel distance L of the safety door  30  by the travel time T obtained by the method 1) or 2) of the first modification. 
       V= L/T    equation (3)
 
     The travel distance L can be an appropriate fixed value corresponding to the safety-door-equipped machine device  10 . 
     The second modification does not differ considerably from the embodiment except that the travel speed V is used in place of the travel acceleration α to determine whether to lock. That is, a determination is made as to whether the travel speed V is greater than a threshold V 1  (first threshold: V&gt;V 1 ? (step S 3 )). If the travel speed V is greater than the threshold V1 (first threshold), the control unit  50  generates a warning signal (step S 4 ), and does not cause the safety door  30  to be locked even. when full closing is detected. If the travel speed V is equal to or less than the threshold V1 (first threshold), then the control unit  50  causes the safety door  30  to be locked when full closing is detected (step S 5 ). 
     As has been described above, the control unit  50  causes the safety door  30  to be locked based on the travel acceleration α, travel time T, or travel speed V of the safety door  30 . This reduces the possibility of damage to the locking mechanism etc. due to an impact of bouncing of the safety door  30 . That is, the travel acceleration α, travel time T, and travel speed V can all be utilized as physical quantities that correspond to the magnitude of the impact of the bouncing of the safety door  30 . 
     The invention grasped from the above-described embodiments and modifications can be summarized as follows. 
     [1] A safety door device ( 12 ) includes: a full closing detector ( 44 ) configured to detect that a safety door ( 30 ) has fully closed from an opened state; a locking mechanism ( 46 ) configured to lock the safety door so that the safety door does not open; a measurement unit (acceleration sensor  36 , control unit  50 ) configured to measure a travel acceleration (α), a travel speed (V), or a travel time (T) when the safety door closes; and a control unit ( 50 ) configured to, when the safety door is detected to be fully closed, control the locking mechanism to lock the safety door, the control unit being further configured not to cause the safety door to be locked if the travel acceleration or the travel speed is greater than a first threshold (α1, V1), or if the travel time is shorter than a second threshold (T1). 
     Thus, the safety door is not locked if the travel acceleration or the travel speed is greater than the first threshold or if the travel time is shorter than the second threshold, whereby the possibility of damage to the safety door device can be reduced. 
     [2] The control unit generates a warning signal if the travel acceleration α or the travel speed is greater than the first threshold or if the travel time is shorter than the second threshold. 
     It is thus possible to give a warning that the safety door device may be damaged. A warning message with an image or sound may be generated on the basis of this warning signal. 
     [3] The measurement unit may adopt the following configurations. 
     (1) Measurement of Travel Acceleration 
     The measurement unit includes an acceleration sensor configured to detect a travel acceleration that is applied to the safety door. 
     (2) Measurement of Travel Time 
     The measurement unit includes: a full opening detector ( 26 ) configured to detect that the safety door is fully open; and a time measuring unit configured to measure, as the travel time, a time from when the full opening of the safety door became undetected to when the full closing of the safety door is detected. The safety door device can thus be protected without using an acceleration sensor. 
     b) The measurement unit includes: an acceleration sensor configured to detect a travel acceleration that is applied to the safety door; and a time measuring unit configured to measure, as the travel time, a time from when the acceleration sensor detected the travel acceleration to when the full closing detector detects the full closing of the safety door. The safety door device can thus be protected on the basis of the travel time without using a full opening detector. 
     (3) Measurement of Travel Speed 
     a) Calculation of Speed Based on Travel Acceleration 
     The measurement unit includes an integrator configured to calculate the travel speed by integrating the travel acceleration detected by the acceleration sensor. 
     b) Calculation of Speed Based on Travel Time 
     The measurement unit may further include a divider configured to calculate the speed (V) by dividing a travel distance (L) of closing of the safety door by the travel time (T). 
     [4] The control unit causes the safety door to be locked when a given time has passed after the full closing of the safety door is detected, if the travel acceleration or the travel speed is equal to or less than the first threshold or if the travel time is equal to or longer than the second threshold. 
     Thus, a safer locking operation is possible by locking the safety door after a given time has passed after the detection of full closing. 
     [5] A safety door locking method uses a safety door device including a full closing detector configured to detect that a safety door has fully closed from an opened state, and a locking mechanism configured to lock the safety door so that the safety door does not open. The safety door locking method includes the steps of: measuring a travel acceleration, a travel speed, or a travel time when the safety door closes; and controlling the locking mechanism to lock the safety door when the safety door is detected to be fully closed, and not to lock the safety door if the travel acceleration or the travel speed is greater than a first threshold, or if the travel time is shorter than a second threshold. 
     Thus, the safety door is not locked if the travel acceleration or the travel speed is greater than the first threshold or if the travel time is shorter than the second threshold, whereby the possibility of damage to the safety door device can be reduced. 
     [6] The safety door locking method further includes the step of generating a warning signal if the travel acceleration or the travel speed is greater than the first threshold or if the travel time is shorter than the second threshold. It is thus possible to give a warning that the safety door device may be damaged. A warning message with an image or sound may be generated on the basis of this warning signal. 
     [7] The safety door device further includes a full opening detector ( 6 ) configured to detect that the safety door is fully open, and in the measuring step of the safety door locking method, a time from when the full opening of the safety door became undetected to when the full closing of the safety door is detected is measured as the travel time. The safety door device can thus be protected without using an acceleration sensor. 
     [8] The safety door locking method includes the step of locking the safety door when a given time has passed after the full closing of the safety door is detected, if the travel acceleration or the travel speed is equal to or less than the first threshold or if the travel time is equal to or longer than the second threshold. Thus, a safer locking operation is possible by locking the safety door after a given time has passed after the detection of full closing. 
     The safety door device and the safety door locking method according to the present invention are not limited to the above-described embodiments, but can adopt various configurations without departing from the scope of the present invention.