Technical Field of the Invention

The present invention relates to RFID (radio frequency identification) interlocking switches with guard locking.

Background to the Invention

Safety switches enable machinery to be used when guards are in place and cut power when the guards are opened. Thus only enabling access by personnel to a guarded work area when the machinery has powered down, thus preventing injury to workers who operate and maintain hazardous machinery.

Actuator operated interlock switches require an actuator to be removed and inserted from a main switch housing. The switch is usually mounted between an access point such as a door in the machine guarding and a frame of the guarding around the door with the actuator mounted to one of the door and frame, and the swich housing mounted to the other of the frame and door. The switch is designed such that a power supply cannot be enabled until the door is closed, and the actuator correctly inserted in the main switch housing. In a switch with machine guard locking, the actuator cannot be removed from the switch housing and the door opened until the machine has come to a stop or is in a safe condition for access thereto. It is also known to provide uniquely coded RFID door sensors to detect the position of the door and potential breakages or separation of the actuator from the switch housing. This provides a further safety feature to ensure that the door is correctly closed and locked before power is enabled to run the machinery, together with an anti-tamper feature to ensure that the correct actuator is used to enable the power and keep the guard locked when the machinery is running. It is known from EP2645393A (Idem Safety Switch Limited) to mount the RFID antenna on the outside surface of the switch housing and the associated RFID read tag on the actuator. The actuator has a main body part adapted to be attached to, for example a guard door, and a actuator bolt depending from the main body, which in use is inserted into the head of the switch housing. The RFID read tag is placed on the main body part. One of the drawbacks of this RFID arrangement is that mounting position for the actuator and switch housing are limited, this is because actuator entry is limited to one direction of approach of the actuator into the switch housing, because the RFID antenna on the exterior of the switch housing needs to face the direction of the RFID read tag on the actuator, usually at close proximity range. The only solution is to fabricate and employ brackets to change the physical mounting direction of the switch or to rotate the switch head to provide a more favourable approach direction to enable the actuator and switch housing to the mounted in multiple positions with respect to each other.

A further disadvantage is the risk of tampering in that the mounting bolts for the switch are accessible and therefore can be removed whilst the machine is running; with the potential for example that the actuator could be removed from its mounting and remain in the switch housing. This would enable the door to be opened without the power being disabled since the actuator would remain in place in the switch housing.

A further drawback is that during use it is difficult to maintain alignment of the actuator read tag to the antenna in the switch housing. This is because the guard door position can change due to misalignment or dropping when in use.

Also, the RFID read tag is not an integral part of the direct locking abutment component (actuator) which abuts directly against the locking components in the switch. This means that the mechanical lock abutment and RFID tag can be manipulated if the components are separated, or in excessive circumstances the RFID tag can become misaligned from the switch antenna and cause nuisance tripping.

Yet a further disadvantage is that back forces from hanging guards can prevent the solenoid system in the safety switch from moving the unlock mechanism after energising the solenoid. Also, after unlocking this back force can cause nuisance opening of the guard.

A further disadvantage of the guarding is that a third-party can close the door enabling power to the machinery, when a worker is still inside the guarding, thus trapping the worker inside the hazardous area. It is an object of the present invention to provide an RFID interlock switch with guard locking which overcomes or alleviates the above described draw backs.

Statement of Invention

In accordance with a first aspect of the present invention, there is provided an RFID safety switch with guard locking comprising an interlock switch with a switch head and an actuator, wherein the actuator comprises a main body constructed to be fixedly mounted to a surface and a dependent elongated actuator bolt adapted to be insertable and selectively held in the switch head of the interlock switch, wherein an RFID read tag is embedded in the actuator bolt of the actuator.

The switch head may have a plurality of apertures each adapted to receive said adapter actuator bolt in the switch head and a plurality of RFID antennae each antenna located inside the switch head adjacent a respective aperture. In a preferred embodiment, there are three apertures and three RFID antennae.

The switch head may be cuboid and three of the four sides of the switch head each have a respective aperture and RFID sensor.

In accordance with a second aspect of the invention, the actuator has or may comprise a handle with an automatic latching system. The handle may have mounting means to fixedly mount it to a surface and further mounting means forming a mounting platform to fixedly mount the main body of the actuator thereto. The further mounting means may extend outwardly from the handle.

The automatic latching system may comprise a pivotal latch biased to a latching position and a thumb catch which automatically locks the latch in the latched position. The latch may be mounted to the mounting platform and at its free end may have a rubber like tip.

In accordance with a third aspect of the invention, the interlock switch has or may have a plurality of mounting apertures used to fix the interlock switch housing to a surface, at least one of the mounting apertures is located inside the switch head. The switch head mounting aperture may be accessible through one of said apertures in the switch head. In accordance with a fourth aspect of the invention, the actuator main body and actuator bolt have or may have a dynamic mounting with respect to each other. The dynamic mounting may include at least one of a rotational movement and linear movement between the main body and actuator bolt. The mounting may be provided by a ball and socket, which may also be biased to hold and move the actuator bolt outwardly from the main body.

In accordance with a fifth aspect of the invention, the actuator bolt has or may have a specific profile which enables it to be selectively locked in the switch head. The profile may provide a locking abutment and the swich head has a complementary internal engaging abutment. The engaging abutment may be a ball catch which may be biased into the interior of the switch head. Adjustment means may be provided to adjust the degree of bias. The locking abutment may be a groove in the surface of the actuator bolt. The actuator bolt profile may have a chamfered head at its free end.

The actuator bolt profile may be adapted to selectively and operatively engage a switch locking plunger of the interlock switch, which switch locking plunger is biased into the switch head, the locking abutment on the profile also being adapted to lock and hold the switch locking plunger in a selective position, the selective position being one in which safety contacts of the interlock switch can close and for power to be enabled.

In accordance with a sixth aspect of the invention, the interlock switch may have or have on a rear portion, a manual release attachment means comprising an openable aperture in the switch body. This may be provided on a side of the switch housing which additionally comprises mounting means for connection of the switch body to a surface.

The manual release attachment means may comprise a pre-tapped hole and a corresponding removeable screw. The switch may further comprise a manual release comprising a release shaft and operating button, the release shaft having means to securely mount in the aperture and connection means to operative connect and operate a release mechanism provided in the interlock switch.

Summary of the Invention By having the RFID tag embedded in the actuator bolt, it is not possible to access the RFID tag when the actuator bolt is engaged inside the switch head. This makes it inaccessible to a third party that may wish to tamper with the correct functioning of the switch. Also, by providing it embedded, even when the actuator is not inserted, it cannot be removed.

By providing the RFID antennae inside the switch housing, this not only compliments the location of the RFID tag on the actuator bolt, but additionally also makes them less accessible and thereby further reduces the possibility of tampering. By providing several locations for entry for the actuator bolt with corresponding antenna, this provides more flexibility in the manner in which the switch and adapter can be mounted and orientated with respect to each other. Therefore reducing the need to build complex structures to enable their complementary mounting or the need to remove the switch head to re-orientate it.

By providing a handle, this has the advantage not only that it makes it easier to open the door when the system is powered down and the actuator bolt of the actuator unlatched, but also enable the presence of a latch which is engaged to prevent the door closing without a positive and intentional action. This therefore reduces the incident of accidental re-closing until the latch is lifted. The handle also allows the option of locating the actuator remotely from the guarding which enables it easy placement over the switch by providing bolt holes in the rear of the housing, which is attached to a surface, this makes the bolts used to attach the switch to a surface inaccessible when the actuator is in place and the switch is locked. This prevents bypassing the lock by virtue of removing the switch whilst in the locked condition.

The so-called dynamic possible mounting of the actuator main body and actuator bolt housing provides a flexible movement feature which can accept some misalignment of the guard door (and actuator fixing) during use without affecting the RFID sensing. This is because the RFID sensing tag is encapsulated in the actuator bolt which is held in the switch head and therefore does not move even if the actuator main body moves during use. This can prevent nuisance tripping due to misalignment. The profile of the actuator bolt provides a captive lock position after its insertion via its positional profile with the switch locking plunger. This is the only position that can cause the safety outputs of the interlock switch to close and for power to engage. Without this profile and the captive locked position, the switch locking plunger would expel, and the safety outputs remain open. The providing of the locking plunger or ball catch placed inside the switch head and its engagement in the profile of the actuator bolt prevents pull back forces from a leaning guard affecting the solenoid unlock feature of the interlock switch. Also, preventing nuisance door openings after unlocking. Adjusting the amount of latch force has the advantage being able to adjust the force to match the requirements of a particular mounting and to adjust the force if conditions change over time.

The release shaft mechanism can be screwed in a pre-tapped hole in the switch without disassembly of the switch or removal of its lid. This enables a manual release button to be fitted before or after installation of the switch.

Detailed Description of the Invention

In order that the invention may be more clearly understood one or more embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

Fig. 1 is a view of an RFID interlock switch with guard locking constructed in accordance with a first embodiment of the present invention;

Fig. 2 is a partial view inside the switch head of the switch of Fig. 1 which shows the positioning of the RFID antennas;

Fig. 3 is a side view of the switch head showing a view through one of the apertures in the switch head and an actuator about to enter an adjacent aperture of the switch head; is similar to Fig. 3 but with the actuator now fully inserted and capture of a locking plunger and positing of a switch locking plunger in an aperture of a actuator bolt of the actuator; is similar to Fig. 4 showing respectively the actuator inserted and subject to relative movement when the mounting moves; shows a detailed view of the position shown in Fig. 3; show a sectional views showing the progressive entry of the actuator bolt into the switch housing; shows a detailed view of a locking plunger of the switch head; is a perspective view of the switch housing with a manual release; are views respectively showing the actuator bolt locked in the switch housing, the actuator bolt entering the switch housing, RFID not sensing and the switch locking plunger depressed by a head of the actuator of the actuator bolt, and the actuator pulled out of the switch housing; is a perspective view to show the rear mounting surface of the switch housing; is a perspective view of the switch head, actuator inserted and locked, and showing flexibility of the mounting of the actuator body to its captive actuator bolt; are each schematic views showing the switch housing mounted to a surface and a handle attached to the actuator to show respectively locking of the guard, switch unlocked, guard door opened and progressive steps in closing the door.

The interlock switch, as best illustrated in Fig. 1 comprises a switch housing 2 and an actuator 4. The switch housing 2 comprises a switch body 6 with a switch head 8. The switch body 6 is of the type which comprises several normally closed and normally open safety contacts, and in a known manner the normally closed contacts enables power when the actuator is inserted and locked in the switch head 8.

The switch housing 2 is cuboid in shape, and has four longitudinal sides 10, a first of which 10a, as best illustrated in Fig. 15 forms a substantially linear surface with means 12, 14, 16, 18 to mount it to a door or frame of guarding. Mounting means 12, 14 comprises a shoulder 18 which depends from one end of the switch housing 2 and which is provided with mounting holes 12, 14. A further mounting hole 16 is provided in the switch head 8.

The switch head 8 has an inner chamber 19 bounded by the four longitudinal sides 10a, 10b, 10c, lOd of the switch housing 2 and by a top surface lOe which closes the end of the switch housing 2.

The switch head 8 also has three apertures 20, each on a respective one of the other three longitudinal sides 10b, 10c, lOd, which apertures 20 lead into the inner chamber 19 in the switch head 8.

The switch housing 2 can be mounted to a surface by placing and bolting it using mounting holes 12, 14 and 16 with mounting hole 16 being accessible via the aperture 20 in the switch housing side 10c, which aperture 20 is located opposite its mounting side 10a.

Two of the three apertures 20b, 20d are in alignment on opposite sides 10b, lOd of the housing 2, i.e., have a common central axis.

The third aperture 20, in the third side 10c of the housing 2 has a central axis which extends in an orthogonal manner to said common central axis of the apertures 20. In this respect adjacent apertures 20 are positioned around the switch head 8 at 90° to each other. Each aperture 20 is adapted to receive the actuator bolt 22 of the actuator 4.

The actuator 4 comprises, as best illustrated in Figs 3, 12, 13 and 16, a main body 24 into which the actuator bolt 22 is mounted. The main body 24 has mounting holes 26 which enable the main body 24 to be fastened to a surface using bolts. The surface can be a door on a guarding or handle described further hereinunder. The actuator bolt 22 and main housing 24 have a dynamic mounting relative to each other to provide a flexible adjustment. This is provided by a rocker style mounting of the main body 24 to the actuator bolt 22, this can be provided by, for example, a ball and socket joint which enables a full range of movement so that the actuator body 24, as best illustrated in Fig. 16, can be flexed in a circular manner about the longitudinal axis of the actuator bolt 22. The mounting of the actuator bolt 22 into the main body 24 is also spring loaded to provide movement of the actuator bolt 22 in and out of the actuator main body 24. The actuator bolt 22 is biased out of the main body 24. A bellows 28 is provided as a flexible seal around the entry of the actuator bolt 22 into the main body 24, which seal 28 prevents ingress of dirt into the joint between the actuator bolt 22 and main body 24, thus preventing the dynamic fit between them from jamming or ceasing to operate during use.

In Fig. 16, the switch housing 2 is shown with an actuator 4 inserted and locked therein, for the ease of illustration and to show an example of the flexible movement possible, the switch housing 2 and actuator 4 are not mounted to surfaces; the actuator main body 24 is shown being flexible relative to the actuator bolt 22 which is held in the switch head 8 to demonstrate the range of movement between the actuator head 24 and actuator bolt 22.

It is to be understood that the actuator main body 24 cannot only flex in the position shown, but also in a full circular manner around the longitudinal axis of the actuator bolt 22. This range of movement will be described further hereinunder.

The locking of the actuator bolt 22 in the switch head 8 also prevents access and therefore removal of the mounting 16 of the switch housing whilst the machine is running and discourages tampering.

As best illustrated in Fig. 3 the actuator bolt 22 also has an RFID tag 30 encapsulated integrally therein. The actuator bolt 22 further has an annular groove 32 which is located between the portion of the actuator bolt 22 encapsulating the RFID tag 30 and a head 34 of the actuator bolt 22.

With the RFID tag being located in the actuator bolt when locked, the RFID tag 30 does not alter position when the actuator 4 moves. This means that during use there is no possibility of nuisance tripping if the actuator position changes about its flexible position.

As best illustrated in Figs. 1 to 7, the switch main body 6 carries a switch locking plunger 36 which activates the switching mechanism in a known manner. The switch locking plunger 36 is spring loaded and is biased out of the switch body 6 and extends into the internal chamber 19 of the switch head 8.

The switch locking plunger 36 is actuated by the actuator bolt 22 of the actuator 4, when the actuator bolt 22 is inserted into the switch head 8. The profile of the actuator bolt 22 provides a captive lock position after insertion through one of the apertures 20 into the inner chamber 19 of the switch head 8.

As best illustrated in Figs. 7 to 10, when the actuator bolt 22 is not inserted into the switch head 8, the switch locking plunger 36 is in an expelled position extending into the inner chamber 19 of the switch head 8. In this position the switch safety outputs are OFF and power is disabled to any attendant machinery.

As best illustrated in Figs. 13 when the actuator bolt 22 enters the switch head 8 via an aperture 20, the actuator bolt 22 starts to extend into the inner chamber 19 and the actuator bolt head 34 which has a curved outermost surface 38, glides over the switch locking plunger 36 to press it into the switch body 6. In this position the actuator bolt 22 is not locked, the switch locking plunger 36 is depressed and the safety switch outputs are still OFF. The RFID is not aligned and sensing as the actuator bolt 22 moves further in, the actuator bolt groove 32 moves over the switch locking plunger 36, as best illustrated in Fig. 9 and 12, and the switch locking plunger 36 is able to partially expel into the groove 32 of the actuator bolt 22 and is then held captive in the actuator bolt 22 via its engagement in the groove 32. In this position the safety switch outputs are ON, and power can be enabled to attendant machinery. The RFID is aligned and sensing. In this position the actuator bolt 22 is locked in the switch 2 by a locking plunger, in the illustrated example in the form of a ball catch 40. The ball catch 40 is mounted inside the switch head 8 on the top surface lOe of the switch head 8 and is spring loaded and biased into the inner chamber 19. The ball catch 40 is in line with the switch locking plunger 36 i.e., they share a common longitudinal axis, when the actuator bolt 22 enters the aperture 20, the contour of the actuator bolt head 34 additionally moves and depresses the ball catch 40 into the top surface, as best illustrated in Fig. 8 and 13. As the actuator bolt 22 moves in further into the switch head 8, the ball catch 40 is released and returns to extend into the inner chamber 19, but is captured in the actuator bolt groove 32, as best illustrated in Figs. 9 and 12. In this position both the switch locking plunger 36 and the ball catch 40 are held captive in the groove 32 of the actuator bolt 22 and the actuator 4 is held captive in the switch head 8 by both the locking plunger and the switch locking plunger 36. The actuator bolt groove 32 is wider than the heads of each of the ball catch 40 and the switch locking plunger 36, which provides a degree of lateral play, enabling a small range of movement of the actuator bolt 22 within the switch head 8. As mentioned above the actuator bolt 22 has a dynamic mounting to the main body 24 of the actuator 4. This enables a tolerance to misalignment of the actuator or possible guard drop during use.

This is the only position that can cause the safety outputs of the switch to close and enable power, that is with the switch locking plunger 36 engaged and held in the actuator bolt groove 32 and with the ball catch 40, the ball catch 40 also engaged in the actuator bolt groove 32 in its locked position. If the switch locking plunger 36 is not in this captive locked position, the safety outputs will open and the machine power cannot be switched on.

The actuator bolt 22 is held captive and latched via the locking plunger or ballcatch 40 inside the head of the switch housing 2 and aligned via its engagement to prevent: a) Pull back forces from, for example, a leaning guard which could otherwise affect the solenoid unlock feature; and b) Prevent nuisance door opening after unlocking

A grub screw is provided through the top surface lOe of the switch head 8, which grub screw 42 is used to adjust the amount of latch force applied by the locking -plunger or ball-catch 40 to the actuator bolt 22 of the actuator 4. This enables the force applied by the ball catch 40 to be adjusted in situ to ensure that the force applied is sufficient to hold the actuator bolt 22 in the switch head 8, dependent on the mounting of the door. It also allows readjustment if the door conditions change, for example, slips or is subject to additional vibrational forces.

As best illustrated in Figs. 2 and 7 to 10, the switch head 8 additionally has three RFID antennas 44, each positioned inside the switch head 8 and adjacent a respective aperture 20. The actuator 4 can be inserted in any of these apertures 20 and the RFID tag 30 on the actuator bolt 22 can transmit and receive date, via the antenna 44 located adjacent that aperture 20. In this respect the code of the tag can be identified and checked and transmitted to the switch operating system in the usual manner to provide a second anti-tamper function and prevent the power being enabled if the RFID arrangement is not also satisfactory identified. The RFID antennas are positioned, like the apertures 20 around the head of the switch at approximately 90° to each other.

In this manner, the actuator 4 can be mounted in a number of orientations without having to move the switch housing 2 on its mounting or utilise brackets to realign it to accept the actuator bolt of the actuator, with a convenient aperture 20 selected for entry of the actuator 4 into the switch housing 2.

As best illustrated in Figs. 11 and 15 the mounting surface 10a can be provided with a manual escape release 46. The switch housing 2 has a pre-tapped mounting hole on its rear mounting surface 10a which can be closed by a screw fitting 48, if the manual escape release 46 is not fitted; the manual escape release 46 can be fitted by removing this screw and fitting it to the rear of the switch housing 2, without disassembly of the switch or removal of the back of the switch housing. This enables the optional provision of an escape release and it can be fitted either before or after installation of the switch housing 2 to a guarding.

The manual escape release 46 comprises a shank 50 and a button 52. Depressing the button moves a shaft (inside the shank 50) into the switch housing 2 to activate a release mechanism (not illustrated) which enables the door of the guarding to be unlocked and enable escape from inside the guarding, instances that a user has been trapped inside the guarding. The opening of the door leads to the disabling of power to the machinery rendering the work area safe. In a further embodiment shown in Figs. 17 to 22, the interlock switch can be provided with a handle 54 to facilitate the opening and closing of the door 56 provided in guarding 58.

The handle 54 has a substantially rectangular profile with a hand grasp 60. The hand grasp 60 is attached at either end to struts 62 which connect the hand grasp to a mounting bracket 64. The mounting bracket 64 has means (not illustrated) to bolt it to a door 56 in the guarding. The handle 54 has a second mounting bracket 66 which extends orthogonally from the hand grasp 60 and strut 62 and mounts the handle grasp 60 to the strut 62. The second mounting bracket 66 has mounting means which enables its connection to the actuator body 24 via its mounting holes 26, such that the actuator 4 is held proud from the handle grasp 60. This enables the actuator 4 to extend beyond its mounting to the door 56 and over the switch housing 2 mounted to the guard frame 58.

The latching mechanism can further include a latch 68 and thumb catch 70.

As best illustrated in Fig. 17, which illustrates the guard door closed and locked. The spring plunger 36 and locking plunger 40 are biased into the annular groove 32 in the actuator bolt 22 of the actuator 4. In this position the latch 68 rests on the outside of the switch head 8 formed by side lOe.

Fig. 18 shows the unlocking of the door in that the switch locking plunger 36 has been drawn into the switch body 6 and the power switched OFF. The guard door 56 is now free to be opened.

In Fig. 19 the opened door is illustrated in which the hand grasp 60 has been pulled to remove the actuator bolt from its mounting in the switch head 8. Actuator head 38 pushes the ball catch 40 into the top surface lOe of the switch housing 8 out of the groove 32 in the actuator bolt 22 to enable the actuator bolt 11 to move out of the switch head and for the door to open. As shown by the arrow A in Fig. 19, the pivotally mounted latch, which is biased towards the second mounting bracket 66 and automatically moves from its engagement with the outside of surface lOe of the switch head 8 and is free to rotate automatically inwardly towards the actuator bolt 22. Thumb catch 70 is also activated and moved in direction B to ensure that the latch remains 68 in this position.

Referring to Fig. 20, if an attempt is made to close the door, that is movement in a direction C, a rubber end face 72 on the tip on the free end of the latch 68 comes into contact with the switch head 8 surface lOe and prevents the further movement of the actuator bolt 22 into the switch head 8. This prevents the door 56 from being unintentionally closed.

In Fig. 21 the thumb catch 70 of the latching mechanism has been positively actuated in direction D and the latch 68 is no longer immobilised enabling it to move out in direction E, enabling the door 56 to be closed and returning the actuator bolt 22 into its position in switch head 8, and latch 68 over the outside of surface lOe of the switch head, as best illustrated in Fig. 22. The latching handle design prevents accidental re-closing and locking. The re-closing and locking is a positive action only possible after the latch is lifted.

Although a substantially rectangular cuboid shape has been described for the switch housing and with linear or smooth surfaces, the shape could be adapted to fit the profile of a surface to which it is mounted. Whilst the actuator has been described as being fitted to a door and the switch body to a guard into which the door is fitted, their mounting positions could be reversed.

The one or more embodiments are described above by way of example only. Many variations are possible without departing from the scope of protection afforded by the appended claims.