國際安全標準　ISO14119:2013 | 台灣

ISO14119 是一項名為「機械安全性—與防護裝置配合使用的互鎖裝置（註1）—設計與選擇的原則」的國際標準（B類標準）。該標準主要包含以下內容：
　・互鎖裝置的種類及其分類
　・在防護裝置開啟時使機械停止運作
　・根據機械停止所需的時間，在危險機械功能仍運作期間鎖定防護裝置
　・採取措施將合理可預見的互鎖裝置無效化行為（註2）降至最低
　・基於上述條件，對防護裝置與互鎖裝置的設計及選擇提出的要求

另外，以下內容引用自 JIS B9710:2019 的部分條文，並基於 IDEC 的理解進行解釋。如對內容有疑問或需進一步了解，請參考 ISO 或 JIS 原文檔案。

基於促動器動原理的互鎖裝置分類

如【圖1】與表1所示，安裝在防護裝置上的互鎖裝置，依其作動原理是否為機械式或非接觸式，以及促動器是否為專門設計，可分為Type 1至Type 4共四種類型。 每種類型在無效化的難易程度上有所不同，因此與防護裝置組合時，其要求事項也會有所差異。

 

 

表 1 中所述的「編碼化」是指為了啟動特定的互鎖裝置，促動器是否經過專門設計。 例如，對於Type 3 的磁性互鎖裝置，如果是對磁性有反應的金屬，無論是哪種金屬，都可以取代原本的促動器來啟動互鎖裝置。在這種情況下，Type 3 的磁性互鎖裝置的促動器被視為未編碼。
另外，Type 2 的舌狀動作位置開關（在 IDEC 中稱為「安全開關」）的促動器是專門設計的。這樣設計的目的是避免使用定規或螺絲起子等工廠現場容易取得的工具來啟動互鎖裝置（即無法輕易使其無效化）。在這種情況下，舌狀動作位置開關的促動器被視為已編碼。

此外，如表 2 所示，已編碼的促動器根據編碼數量分為未編碼、低（Low）、中（Medium）、高（High）等不同級別。編碼數量越多，越不容易被無效化。

　

帶鎖互鎖防護裝置的必要條件

通常為了防止人員因運轉中的危險機械功能發生事故，會使用防護裝置將危險機械功能圍起來。雖然將所有機械完全用固定式防護裝置圍住是安全的，但考量到工件的進出、清潔維護以及更換生產設定等使用便利性，此做法並不切實際。因此，通常會將防護裝置的一部分設計成門（可動式防護裝置），並配備互鎖裝置來檢測門的開閉狀態，這樣的設計就稱為帶有互鎖功能的防護裝置（互鎖防護裝置）。 互鎖防護裝置的功能是：當門處於關閉狀態時，允許危險機械功能運作；而當門處於開啟狀態時，危險機械功能則保持停止狀態，以在生產效率與安全性之間取得平衡。

針對這樣的互鎖防護裝置，首要考量的問題是是否需要帶鎖功能。

在這個情況下，需要考慮以下兩個時間之間的關係：
　・人員從打開門到接觸到危險機械功能所需的接近時間

如【圖2】所示，根據這兩個時間的關係，可以判斷互鎖防護裝置是否需要帶鎖功能：

互鎖裝置的功能圖示

如前所述，當總系統停止性能 < 接近時間時，在人員打開門並接近之前，危險的機械功能已經完全終止，因此互鎖防護裝置上並不需要安全鎖。
如【圖3】所示，無帶鎖互鎖裝置在防護裝置關閉時，危險的機械功能可以運轉。而且，防護裝置可以隨時開啟；當防護裝置開啟時，危險的機械功能將無法運轉。


此外，如前述，若總系統停止性能 ≧ 接近時間，為了防止人在危險的機械功能停止之前靠近，需要為互鎖防護裝置加裝鎖定功能。在鎖定式互鎖防護裝置中，如【圖 4 】所示，解鎖的條件分為兩種類型：一是「a) 無條件解鎖」，另一是「b) 條件式解鎖」。

這裡所說的「a) 無條件解鎖」是指操作者可以在任何時候解除鎖定的方式。然而，仍有一些條件需要滿足。例如，從操作者按下解鎖按鈕發出停止訊號，到危險的機械功能終止為止的時間，必須長於鎖定被解除所需的時間。
另一種「b) 條件式解鎖」是指只有在危險的機械功能終止之後，操作者才可以解除鎖定的方式。為了滿足此條件，需要採用某些方法來檢測危險的機械功能是否已經終止。

施錠式インターロック付きガードのロック方式

総合システム停止性能≧接近時間であり、施錠式インターロック付きガードが必要となった場合、ロックの方式は図5、図6のどちらかである必要があります。

スプリングロック方式：スプリングでロック、動力オンで解錠

図5はソレノイド端子に電圧が印加されていない状態を示しています。この時、スプリングの力でロッドが図中の左に移動し、カムにロックがかかっています。
なお、ソレノイドに電圧が印加されると、ソレノイドが励磁されることでロッドが図中の右方向に移動し、カムのロックが解除されます。

動力ロック／ロック解除方式：動力オンでロック、動力オンで解錠

図6はソレノイド端子にある方向に電圧が印加されている状態を示しています。この時、ソレノイドの励磁で発生した力によりロッドが図中の左に移動し、カムにロックがかかっています。
なお、ソレノイドに逆方向の電圧が印加されると、ソレノイドの励磁で発生する力が逆方向になることでロッドが図中の右方向に移動し、カムのロックが解除されます。

なお、図6のロック／ロック解除方式：動力オンでロック、バネで解錠については、安全上ロックは必要ないが、生産プロセスを保護するためにロックを行ないたい場合（例えば、生産中に勝手に扉を開けられたくないなど）においてのみ、使用することができます。

ソレノイドロック方式：動力オンでロック、バネで解錠

図6はソレノイド端子に電圧が印加されている状態を示しています。この時、ソレノイドが励磁されることでロッドが図中の左に移動し、カムにロックがかかっています。
なお、ソレノイドへの電圧印加を停止すると、圧縮バネの力でロッドが図中の右方向に移動し、カムのロックが解除されます。

なお、「スプリングでロック、動力オンで解錠」「動力オンでロック、バネで解錠」のより詳しい説明は以下のリンク先にてご確認ください。

Erroneous positioning of an interlocking device main body or an actuator as well as positional shifts due to vibration/impact during use could have negative effects such as inability to properly detect the opening and closing of doors, and damage to the interlocking device. To address this, the requirements for the installation of interlocking devices are  specified as below.

Requirements for the installation of interlocking device main bodies

In order to maintain the position of the device properly installed in accordance with manufacturer’s instructions, the following requirements need to be met:
・  To ensure reliable installation, and to require tools (Note 4) to loosen the device.
Note 4) Makeshifts, including a coin or a nail file, cannot be regarded as tools.
・  For the Type 1 interlocking devices, to have a method for fixing the position permanently after adjustment (e.g., pins, dowels).
・  To have access to the interlocking device for maintenance and operation checks. However, the prevention of  defeat attempted in a reasonably foreseeable manner must be considered.
・  To prevent the device from spontaneously loosening.
・  To prevent  defeat of the interlocking device attempted in a reasonably foreseeable manner.
・  To be located and, if necessary, protected so that damage from foreseeable external causes is avoided.
・  To follow manufacturer’s instructions regarding the positional relationship between the actuator and the interlocking device main body.
・  Not to use the device as a mechanical stopper ( Unless the manufacturer permits).
・  Not to create a gap of the guard where a part of human body could enter inside and cause an accident, by misalignment of the installation.
・  To install the device firmly so that its correct movements can be maintained.
・  For the Type 2 interlocking devices, to have a dust protection cover or alternative means at an opening through which the actuator is inserted, or by installing the device in an orientation that can prevent dust from entering through the opening, in order to avoid the contamination and deterioration of machine parts due to dust.

Requirements for the installation of actuators 

In order to minimize the possibility of a device loosening or shifting from its proper installation position during the expected life, the following requirements need to be met:
・  To ensure reliable installation, and to require tools (Note 4) to loosen  fasteners of the actuators.
Note 4)  An improvised implement such as a coin or a nail file cannot be considered as a tool.
・  To prevent the  actuator from spontaneously loosening.
・  To be located and, if necessary, protected so that damage from foreseeable external causes is avoided.
・  Not to use the  actuator as a mechanical stopper ( Unless the manufacturer permits).
・  To install the  actuator firmly so that its correct movements can be maintained.


If the overall system stopping performance ≥ access time, and an interlocked guard with guard locking is required, specified conditions need to be satisfied to start a hazardous machine function. That is, both the conditions that the door is closed and locked need to be satisfied.
For example, as shown in Figure 5,  the contact to detect the state of the door (open/closed) and the contact to detect the state of the lock (locked/unlocked) connected in series can satisfy these conditions.
Alternatively, realizing the NC contact, which works only while the door is closed and locked, in the structure of an interlock switch will also be able to satisfy these conditions.
This type of circuit, which can start a hazardous machine function only while the door is closed and locked, has the locking monitoring mark shown in Figure 8.

As stipulated in ISO12100, when safety measures were taken as a result of risk assessments, it is important to confirm that they will not create a new hazard. This also applies in cases where an interlocked guard with guard locking is required for safety purposes. When the overall system stopping performance ≥ access time, and an interlocked guard with guard locking is installed to prevent people from approaching it until a hazardous machine function terminates, it is necessary to confirm that the installation has not created a new hazard. There are a variety of machines, large and small, and those requiring particular attention are large ones that have an interlocked guard with guard locking that is large enough to accommodate a whole human body. For these large machines, it is necessary to confirm that locking the interlocked guard with guard locking will not create a new hazard by trapping a worker or maintenance worker in the machine.

If such a new hazard can be created, the machine needs to be equipped with the “emergency release function” to release the guard locking from outside in case of an emergency and the “escape release function (Figure 9)” to release the guard locking from inside. In addition, to address a situation in which an interlocked guard with guard locking fails and needs to be released from outside, the “auxiliary release function (Figure 10)” may be required.
 

IDEC offers various interlock switches with these unlocking functions. Please select products that meet your needs.

Locking strength against a static force and Locking strength against a dynamic force

When an interlocked guard requires guard locking, the locking strength of the interlocking device needs to be checked. This is because if the force that exceeds the locking strength specification value causes damage to the locking mechanism, a person will be exposed to an operating hazardous machine function.

To avoid such a situation, it is necessary to select a lock type interlock switch with specifications that meet the required locking strength by taking into account matters such as the weight of the door and the power used to move the door (moved by human power, or motor, etc.).

It should be noted that the specifications of interlock switches generally state the locking strength against a static force. The locking strength specification value represents a value that indicates the maximum force it can withstand when a force is slowly applied in the door opening direction in the locked condition.

For example, when a door is forcefully closed, the bouncing back or the machine vibration can apply dynamic forces to the locking mechanism, but these dynamic forces are not considered in locking strength specification values. Therefore, if the bouncing back or the machine vibration occurs repeatedly in the actual operation of the machine as a result of forcefully closing the door, those dynamic forces could lead to unexpected malfunctions or damage to the locking mechanism, even if the dynamic forces are below the locking strength specification value.

To address this, a machine design is required that minimizes the bouncing back or the machine vibration that occurs when the door is forcefully closed. It is also important in terms of safety to examine how the locking mechanism is damaged in case it is damaged. It is recommended to examine, before designing the machine, whether the machine stops (a safe failure), or does not stop (a dangerous failure), or both can happen according to time and circumstances.

IDEC offers various locking type interlock switches that take into consideration failure modes  in case of the damage of a locking mechanism. Please select products that are suited for your applications.

Interlocking devices may be  defeated for a variety of reasons. For example, people may want to  defeat an interlocking device in order to operate the machine for adjustment work while leaving the door open, in order to work while leaving the door open to avoid the troublesome task of opening and closing the door frequently, and in order to improve work efficiency as troubles/failures of an interlocking device cause the machine to stop frequently. However,  defeating an interlocking device can compromise the safety of the worker and lead to a significantly higher possibility of unexpected accidents.
This is why preventing  defeat of interlocking devices is important.

One is to improve the design and working processes of the machine, for example by making it easier to operate, so that the incentive to defeat is fundamentally less likely to arise.
Secondly, if it is difficult to eliminate the incentive to defeat, then the measures specified for each type of interlock device, as shown in Table 3, will prevent defeating in a reasonably foreseeable manner.
Note)  Defeat of interlocking devices that is attempted manually or using  readily available objects. It includes removing an interlocking device main body or an actuator using tools necessary for the intended use of the machine, or  readily available tools (i.e., a screwdriver, wrench, hexagonal wrench, pliers). The  readily available objects include things that are used in our daily lives, such as a screw, needle, a piece of metal, key, coin, adhesive tape, string, and wire, as well as a spare actuator.

 

Prevention of accessibility to the elements of the interlocking device

Defeat prevention by the control system

Non-detachable fixing

 Interlocking devices are safety-related parts of the control system(SRP/CS) of a machine, or a subsystem or a subsystem element of a safety-related
electrical control system (SRECS). They may have the required performance levels (PLr) or necessary categories that are  specified in a machine-specific individual safety standard in order to prevent the actuation of hazardous machine functions while the door is open. Please confirm the relevant machine-specific individual safety standard.
For further information  on the required performance levels and categories, please click on the link below: