GB2051207A - Door Lock Safety System - Google Patents

Abstract

An access door to a vessel fed by one or more pipelines is provided with a safety lock. The or each pipeline is equipped with a valve operated by a spindle 5 and the vessel is equipped with a lock bolt operated by fluid pressure by means of which the access door is kept closed, the or each valve being lockable in a particular condition (closed as shown) by a cylinder lock 14 having a movable detent 16 (shown unlocked), the locking of the valve or the locking of the last valve in a sequence causing the detent 16 to operate a switch enabling fluid pressure to unlock the door lock and said key then being used to prevent the door lock from being re-applied other than through the permissive agency of said key. <IMAGE>

Description

SPECIFICATION Safety System for Production of Comestible Substances This invention relates to a safety system for the production of comestible substances.

The term "fluid-flow control valve" as employed herein is intended to mean a structure or device which is operable to regulate flow of a fluid (gas or liquid) along a pipeline in which said structure or device is connected or to permit flow of a fluid in only one direction along said pipeline, said structure or device including a spindle to which is connected to an obturator housed within the valve body and which is capable of being turned through an angle of less than 3600 to bring said obturator from its fully open position to its fully closed position, and vice versa. By way of example, such a "fluid-flow control valve" may be a butterfly valve or a ball valve, in each of which there is a movement of an ungeared operating handle of 900 of arc.Moreover, the term "comestible substance(s)" as employed herein intended to be interpreted to include straightforward food(s) such for example as jams and sauces; drinkable products such for example as alcoholic beverages and soft drinks; pharmaceutical preparations, and dairy products; said aforementioned products being generally but not exclusively for consumption by or administration to human beings.

A safety system would be useful in the manufacturing activities of many industrial companies producing comestible substances (as defined above) but, in the following description, reference will only be made to one sector of the industry in which drinks are made; this has been done by way of example only and in order to simplify the description.

In order to ensure the hygienic production of a beverage (for example beer) and in order to eliminate any possibility of infection as far as is humanly possible, proper cleaning of the vessels in which production takes place must be carried out. This can be done by built-in spray devices (sprayballs) connected to a central CIP (cleaning in place) unit but it is still necessary to inspect the vessels to see that the CIP programme has been adequate. This often requires personnel entering into the vessels through lockable access doors in order to take the "swabs" for later examination in the laboratory. In addition to personnel entering into vessels for purposes of quality control, they may also need to enter to inspect and service equipment such as agitators and the sprayballs.

The tendency on the part of manufacturers is aiways to install larger vessels, coupled with increasing use of automatic, or remote handoperated, control systems. Thus, for example with a large brewhouse vessel in a brewery, a person inside the vessel may be subjected to the following hazards:- (1) Drowning as a resuit of the remote operation of a fluid-flow control valve which is operated to supply a liquid to the vessel; (2) Burning by heat applied by the built-in wall heating of the vessel (steam at 1800 C); (3) Suffocation by solids fed into the vessel, such as hops; and (4) Chemical burning due to being sprayed with caustic soda or acids which are used for CIP.

A need exists, therefore, for simple equipment and a simple method of use thereof which can guard a person entering into a vessel, and whilst within the vessel, against accidents which can be caused, for example, by the erroneous operation of external fluid-flow control valve or by a buildup of carbon dioxide gas or by welding fumes, and the principal object of the present invention is to satisfy this stated need.

Accordingly the present invention consists in a safety system incorporating a fluid-flow control valve (as defined above) and a door lock; said valve having a lever, which is secured to the valve spindle, and a cylinder lock which includes a detent which is positionable, upon operation of the lock by a key, to engage a portion of fixed means to maintain the lever in that position thereof which corresponds with the fully open or the fully closed condition of the valve; said door lock having a bolt displaced in a first direction of movement thereof by a fluid under superatmospheric pressure against the influence of a return spring from a "door locked" position thereof to a "door unlocked" position thereof, or vice versa; said detent, when positioned to engage said portion of said fixed means, also actuating a switching device operable to permit said pressurised fluid to displace said bolt in said first direction of movement thereof.

In one embodiment of said safety system, said fixed means comprises a plate which is secured directly to the valve body and which has an elongate arcuate channel along which a barrel of said cylinder lock is moved whenever the lever is actuated to bring the valve into its fully open or fully closed condition.

The cylinder lock may be securely connected to the lever for movement thereby and may also extend from the lever into said channel, the detent of said lock being movable, when the barrel of the lock is at a unique end of said channel, in an arc through approximately 1800 from a first attitude thereof in which further movement of the lever is not prevented to a second attitude thereof in which further movement of the lever is prevented by said detent engaging said portion of said fixed means.

In accordance with known techniques, when the fluid-flow control valve is a butterfly valve, an arcuate toothed rack may be provided, preferably as an integral part of said plate, which rack is engaged by one end of an arm which is secured to the lever, said one end of the arm being disengageable from said rack against spring influence to permit movement of the lever and engaging the rack again under said spring influence in order to prevent unintended adjustment of the disc under the action of a pressurised fluid.

In a generally preferred embodiment of said safety system, the door lock is provided with a key-operated member which is positionable to prevent unauthorised displacement of the bolt from the "door unlocked" position therefore to the "door locked" position thereof, or vice versa.

This may be achieved in a simple manner by fitting another cylinder lock with a detent, similar to the lock which is associated with the valve lever, adjacent to the door lock bolt which is provided with a step or shoulder, the arrangement being such that after displacement of said bolt from the "door unlocked" position thereof to the "door locked" position thereof or vice versa the cylinder lock is operated by a key to position its detent in the path which would be travelled by said step or shoulder if any attempt were to be made subsequently to displace said bolt.

Said bolt preferably consists of two cylindrical coaxial portions of which one has a much smaller diameter than the other, the portion of larger diameter being formed with a circumferential groove which is so positioned as to provide two full-diameter lands which are separated from one another axially of the bolt, two roller-actuated switches being included in the door lock whose rollers are supported by said portion of larger diameter, said switches being operated in dependence upon the bolt position to indicate the condition of the mechanism. Thus, for example, with the bolt withdrawn and the door unlocked, the roller of one switch is in said circumferential groove and the roller of the other switch is on one of the full diameter lands; in this state, there will be an indication, activated by said one switch, that the door is unlocked.Continuing the example, with the bolt engaging the bolt plate which is carried by the door and therefore with the door being locked, the roller of said one switch is on the other of the full-diameter lands and the roller of said other switch is in the circumferential groove; in this state, there will be an indication, activated by said other switch, that the door is locked.

Preferably, in association with the arrangement described in the preceding paragraph, the cylinder lock of the door lock will be provided with an extension spindle such as will actuate yet another switch when said cylinder lock has been keyoperated to move the detent into the position thereof in which displacement of the bolt is prevented by said detent. By appropriately wiring this additional spindle-actuated switch and said one switch, the indication given can, for example, be a visible sign stating "Door unlocked. Safe to enter".

Displacement of the bolt in said first direction of movement thereof (for example, to unlock the door) is effected by pressurised fluid acting against the force of a spring upon one face of the piston in a cylinder, and displacement of the bolt in the opposite direction of movement thereof (in the same example, to lock the door) is effected by venting the pressure chamber of the cylinder and thereby permitting the spring to push the piston along the cylinder. This arrangement is, therefore, a fail-safe arrangement. Moreover, as an additional refinement of such fail-safe arrangement, there can be an additional visible and/or audible indication that the door is not shut and locked.This can be achieved quite simply by providing a limit switch connected to a visible sign and for example a Klaxon and by making the cylinder of such a length that the limit switch will only be actuated when the bolt has been displaced by the spring towards its door-locking position when the door and its bolt plate are not in the required position. In this state, the rollers of both of the roller-actuated switches will be on the other of the full-diameter lands, with the result that there will be no indication from those sources that the door is locked or unlocked.The additional visible and/or audible indication described in this paragraph is desirable because (a) the bolt could become accidentally "shot home" without engaging the bolt plate on the door as a result of failure in the supply of pressurised fluid whilst, for example, personnel were still in the vessel; or (b) the bolt could become intentionally "shot home" without engaging the bolt plate on the door as a result of personnel forgetting to close the door and operating the valve lever.

According to another aspect, the present invention consists in a safety system which comprises a fluid-flow control valve (as defined above) having a lever which is secured to the valve spindle and which carries a cylinder lock which includes a detent which is positionable, upon operation of the lock by a key, to engage a portion of fixed means to maintain the lever in that position thereof which corresponds with the fully open or the fully closed condition of the valve.

Preferabiy, said valve of the other aspect of the safety system incorporates a switching device which is operated by said detent, when said detent engages said portion of said fixed means.

Said switching device may be, for example, pneumatic or electrical and may be provided either to activate an informing device (e.g. a flashing red light, a Klaxon, a legible indicator board) or operate another mechanism (e.g. a door bolt).

The fixed means of the valve of the other aspect of the safety system may comprise a plate which is secured directly to the valve body and which has an elongate arcuate channel along which a barrel of said cylinder lock is moved whenever the lever is actuated to bring the valve into its fully open or fully closed condition.

The detent of the cylinder lock of the valve of the other aspect of the safety system is preferably movable by said key, when the barrel of the lock is at a unique end of said channel, in an arc through approximately 1 800 from a first attitude thereof in which further movement of the lever is not prevented to a second attitude thereof in which further movement of the lever is prevented by the detent engaging said portion of the fixed means.

The present invention further consists in a safety system which is constructed, arranged and operable substantially as hereinafter described with reference to and as illustrated in the accompanying diagrammatic drawings, in which: Figure 1 is a plan view of a fluid-flow control valve forming part of said safety system, and which constitutes said other aspect of the present invention; Figure 2 is a sectional elevation taken on the section line Il-Il in Figure 1; and Figures 3 to 5 illustrate a door lock which forms part of said safety system, said door lock being in three different conditions.

Referring to Figures 1 and 2, there is illustrated a butterfly valve 1 having a valve body 2 which is flanged at 3 and which accommodates a disc 4, said disc being connected to the inner end of a spindle 5 whose outer end projects from the valve body. Secured to the flange 3 by nuts and bolts 6 is a plate 7 which is of quadrant shape in plan configuration and which is apertured to permit the free end portion of the spindle 5 to extend therethrough. Secured to said free end portion of the spindle 5 by a taper pin 8 is a lever 9.

The plate 7 is formed to provide a box-like element 10 which is arcuate in plan configuration and of which one wall is interrupted by a continuous arcuate slot 11. It will be seen from Figures 1 and 2 that the hollow element 10 provides an elongate arcuate channel which is of L-shaped cross-section over its entire length, and that a portion of said channel is extended by an enlargement 12. Said enlargement 12 is illustrated in Figure 1 and can be seen to be of semi-annular shape in plan configuration, and it can also be seen that said enlargement 12 constitutes an extension of the portion 1 3 of the channel.

The lever 9 carries a cylinder lock 14 whose barrel 1 5 extends through the slot 11, and the inner end of the lock terminates in a detent 16. It will be appreciated that, when the lever 9 is swung through an arc of 900 from the position illustrated in Figure 1 (i.e. in order to open the valve), the barrel 1 5 will move along the arcuate slot 11 and the detent 16 will move along the portion 13 of the channel.

When the lock 14 is operated by a key (not illustrated), the detent 1 6 is moved from the position thereof illustrated in Figures 1 and 2 through an arc of approximately 1 800 in order to engage a portion of said plate 7 of which the element 10 forms a part. In such condition, the lever 9 cannot be moved in an arc from the "valve closed" condition thereof because the detent 1 6 is unable to move past the portion of the plate 7.

Associated with the plate 7 is a switching device 1 7 which, in the embodiment illustrated, is a three port pneumatic relay which is operated by said detent 1 6 to allow compressed air to flow therethrough when the lever 9 is in the "valve closed" condition. Said compressed air operates, for example, a visible and/or audible indicator at a console at a location which is remote from the valve or another piece of mechanism such as a door lock. When the valve is opened as a result of unlocking the lock 14 and moving the lever 9 through a 900 arc from its Figure 1 position, the relay 17 will be vented to atmosphere and the visible and/or audible indicator will therefore indicate the "valve open" condition, or the door lock will be caused to assume a changed condition. The switching device may be, for example, electrical instead of pneumatic.

The lever 9 also carries a ratchet arm 18 whose free end is adapted to engage the teeth of a toothed arcuate rack 19 which is formed in said plate 9 or is attached to said plate, said free end being kept in engagement with said teeth by a compression spring 20. In order to rotate the lever 9 about the axis of the spindle 5, the operator must firstly squeeze the arm 1 8 upwardly (as seen in Figure 2) against the spring influence with his fingers in order to disengage the free end of the arm from the rack 19 and, secondly, move the lever as far as is desired. As soon as the operator releases the squeeze applied to the arm 1 8 the spring influence will cause re-engagement of said arm with the teeth of the rack. This known arrangement is to prevent pressurised fluid which is flowing through the partially opened valve 1 from altering the setting of the disc 4.

Referring now to Figures 3 to 5, there is diagrammatically illustrated a part of a door 30 of a vessel, said door carrying a bolt plate 31 which consists essentially of U-shaped element fixed to the door by screws extending through the base of the U, one limb of the U acting as an end stop and the other limb thereof having a passageway 32 of circular section therein.

Adjacent said door 30 and in alignment with the bolt plate 31 is an assembly comprising a box 33 upon which is mounted a cylinder 34 whose piston 35 is connected to one end of a piston rod 36 which extends through one wall of the box into the box 33, the other end of said piston rod being connected to one portion 37 of a bolt 38. The bolt 38 is formed to provide a part of large diameter (namely, the portion 37) and a conjoined part of small diameter (namely, a portion 39). Said portion 39 extends through another wall of the box 33 out of the box.

The portion 37 has a circumferential groove 40 which, therefore, subdivides the cylindrical surface of the portion 37 into two axially separated lands 41,42.

The box 33 houses two switches 43, 44 of socalled roller-actuated type, the rollers 45, 46 of said switches 43, 44, respectively, being in contact with the portion 37 at all times.

A cylinder lock 47 having a detent 48 is positioned near the portion 37 and is operable by a key (not shown) to move the detent 48 in an arc through approximately 1 800 to bring it from the Figure 3 position thereof to the Figure 4 position thereof or vice versa.

The air cylinder 34 has a compression spring 49 which at all times urges the piston 35 to move from left to right as seen in Figures 3 to 5. Said air cylinder has its pressure chamber 50 connected by a suitable pipe 51 to a source of fluid at superatmospheric pressure (e.g. compressed air) by way of the switching device 1 7 shown in Figures 1 and 2.

The operation of the door lock illustrated in Figures 3 to 5 is briefly as follows Assuming that the door 30 of the vessel is locked to begin with (Figure 4), the bolt 38 is displaced from right to left by admitting pressurised fluid into the chamber 50, This forces the piston 35 along the cylinder 34 against the influence of the spring 49 and, simultaneously therefore, the free end portion of the portion 39 is moved out of engagement with the bolt plate 31.

In this state, which is illustrated in Figure 3, the door 30 is unlocked and the unlocked condition of the door is indicated (locally and/or remotely) by an indication which is activated by the roller 45 moving off the land 41 into the groove 40, thereby operating the switch 43. Conversely, the roller 46 has moved out of the groove 40 onto the land 42, thereby turning the switch 44 off.

After the job has been done which necessitated opening the door 30, the pressurised fluid is vented to atmosphere from the chamber 50, with the result that the piston 35 is pushed along the cylinder by the spring 49, this simultaneously causing the free end portion of the bolt 38 to enter the passageway 32 and eventually to make contact with the end stop at 'A'. In so doing, the roller 45 has moved out of the groove 40 onto the land 41 and the roller 46 has moved off the land 42 into the groove 40. This causes an indication to be given that the door is locked, the switch 44 being turned on for that purpose and the switch 43 being turned off.

If, either as a result of failure of the pressurised fluid supply or as a result of incorrect (i.e.

premature) operation of the valve of Figures 1 and 2, the piston 35 were to be moved by the spring 49 from left to right without the door having been closed, the path of travel of said piston 35 along the cylinder 34 will be longer (see Figure 5) because the free end of the bolt 38 never comes into contact with the end stop. Consequently, both the roller 45 and the roller 46 will be on the land 41 and this will mean that both switches will be turned off. It would be a simple matter to arrange a limit switch in, for example, the box 33 so that said limit switch (not illustrated) is actuated by an end face 52 of the portion 37 when said end face 52 reaches the position thereof which is illustrated in Figure 5; said limit switch could actuate visible and/or audible signals disposed locally and/or remotely which would warn everyone that the vessel door 30 is open.

The cylinder lock 47 is keyoperated, when the bolt 38 has been withdrawn from the bolt plate 31, to cause its detent 48 to move from its Figure 4 position to its Figure 3 position. In this state, the bolt 38 is positively held withdrawn and it will not matter if there is a failure in the supply of pressurised fluid because the detent 48 will hold the bolt 38 even though the spring 49 will be urging the bolt to move from left to right as seen in the drawing. Thus, in the Figure 3 condition, personnel in a vessel will not be in any danger of becoming trapped in the vessel because, apart from other safeguards, the vessel door 30 cannot become accidentally locked because the door lock is disabled by the detent 48.

It is an important feature of the safety system according to the present invention that any person intending, for example, to open a vessel for the purpose of getting inside the vessel to make repairs or adjustments or to carry out servicing operations will have a key which, for all practical purposes, will be the only key (for example a key of the so-called "Kaba" trade mark, type). With that key, the person must operate and lock the or each fluid-flow control valve in the desired condition; most valves will probably need to be closed, in which case they will all be locked in their closed conditions. One or more other valves might, however, need to be opened (for exampe, to vent to atmosphere any possible accumulations of fumes or gases) and in that case the or each valve will be locked in its open condition.In an installation comprising at least one vessel, it could easily be arranged that the various valves would need to be locked closed and locked open in a particular sequence, thereby ensuring that all valves have been correctly operated before entry into the vessel is facilitated; for example, it might be made necessary to close (1) valve in cip pipeline (2) valve in process pipeline A (3) valve in process pipeline B (4) valve in pipeline for steam input in that precise order, only the valve in the steam pipeline being equipped with the switching device 17 (Figures 1 and 2) and the valve in the steam pipeline only being operable when all of the other valves have been closed.

The safety system could be further extended to ensure that all other potentially dangerous equipment is disabled before any indication is given to the person that it is "Safe to enter" the vessel. Frequently vessels are fitted with motordriven agitators and internal ciosed-circuit pumps and these must not be operable under any circumstances by anyone whilst the person is in the vessel. Normally, electric motors are used for apparatus like agitators and pumps and they are normally controlled by a starter control unit, and the wire to the or each starter control unit can be broken by a key-operated electrical switch; for example, such a switch could be connected to the cylinder lock 47 so that the control unit circuit is broken whenever the lock 47 is operated to move the detent 48 from the Figure 4 position thereof to the Figure 3 position thereof.

It needs to be pointed out that the single key used by the person to lock all valves and to lock the bolt 38 of the door lock open is of the type which can be inserted and withdrawn only when the respective lock has been properly operated; in other words, it would not be possible to turn the locks 14, 47 through only 900 and to withdraw the key. It would be necessary to turn the key through a full 1800 in each lock in order to be able to withdraw it. Thus, it is ensured that the person goes through the entire essential disabling sequence with the single key before he receives the "Safe to enter" signal. He then enters the vessel with the key on his person so that it is substantially impossible for anyone to lock him inside the vessel and/or to supply any product ingredient or steam to the vessel or to spray him with any cip liquid or to actuate any machinery whch would injure him. The person inside the vessel is the only person who is able to put the installation back into a working condition by using his single key to operate the various locks in the reverse sequence.

Claims (19)

Claims

1. A safety system incorporating a fluid-flow control valve (as defined above) and a door lock; said valve having a lever, which is secured to the valve spindle, and a cylinder lock which includes a detent which is positionable, upon operation of the lock by a key, to engage a portion of fixed means to maintain the lever in that position thereof which corresponds with the fully open or the fully closed condition of the valve; said door lock having a bolt displaced in a first direction of movement thereof by a fluid under superatmospheric pressure against the influence of a return spring from a "door locked" position thereof to a "door unlocked" position thereof, or vice versa; said detent, when positioned to engage said portion of said fixed means, also actuating a switching device operable to permit said pressurised fluid to displace said bolt in said first direction of movement thereof.

2. A safety system as claimed in Claim 1, wherein said fixed means comprises a plate which is secured directly to the valve body and which has an elongate arcuate channel along which a barrel of said cylinder lock is moved whenever the lever is actuated to bring the valve into its fully open or fully closed condition.

3. A safety system as claimed in Claim 2, wherein the cylindar lock is securely connected to the lever for movement thereby and extends from the lever into said channel, the detent of said lock being movable, when the barrel of the lock is at a unique end of said channel, in an arc through approximately 1 800 from a first attitude thereof in which further movement of the lever is not prevented to a second attitude thereof in which further movement of the lever is prevented by said detent engaging said portion of said fixed means.

4. A safety system as claimed in Claim 2 or Claim 3, wherein, when the fluid-flow control valve is a butterfly valve, an arcuate toothed rack is provided which is engaged by one end of an arm which is secured to the lever, said one end of the arm being disengageable from said rack against spring influence to permit movement of the lever and engaging the rack again under sadi spring influence in order to prevent unintended adjustment of the disc under the action of a pressurised fluid.

5. A safety system as claimed in Claim 4, wherein said rack is integral with or attached to said plate.

6. A safety system as claimed in any one of the preceding Claims, wherein the door lock is provided with a key-operated member which is positionable to prevent unauthorised displacement of the bolt from the "door unlocked" position thereof to the "door locked" position thereof, or vice versa.

7. A safety system as claimed in Claim 6, wherein said key-operated member is another cylinder lock with a detent, similar to the firstmentioned lock which is associated with the valve lever, said other cylinder lock being fitted adjacent to the door lock bolt which is provided with a step or shoulder, the arrangement being such that after displacement of said bolt from the "door unlocked" position thereof to the "door locked" position thereof or vice versa said other cylinder lock is operated by a key to position its detent in the path which would be travelled by said step or shoulder if any attempt were to be made subsequently to displace said bolt.

8. A safety system as claimed in Claim 6 or Claim 7, wherein said bolt consists of two cylindrical coaxial portions of which one has a much smaller diameter than the other, the portion of larger diameter being formed with a circumferential groove which is so positioned as to provide two full-diameter lands which are separated from one another axially of the bolt, two roller-actuated switches being included in the door lock whose rollers are supported by said portion of larger diameter, said switches being operated in dependence upon the bolt position to indicate the condition of the mechanism.

9. A safety system as claimed in Claim 8, wherein said other cylinder lock is provided with an extension spindle such as will actuate yet another switch when said other cylinder lock has been key-operated to move the detent into the position thereof in which displacement of the bolt is prevented by said detent.

10. A safety system as claimed in any one of the preceding Claims, wherein displacement of the bolt in said first direction of movement thereof is effected by pressurised fluid acting against the force of a spring upon one face of the piston in a cylinder, and displacement of the bolt in the opposite direction of movement thereof is effected by venting the pressure chamber of the cylinder and thereby permitting the spring to push the piston back along the cylinder.

11. A safety system as claimed in Claim 10, wherein means are provided for the purpose of creating additional visible and/or audible indication(s) that the door is not shut and locked.

1 2. A safety system as claimed in Claim 11, wherein a limit switch is provided which is connected to a visible sign and/or to a device operable to produce an audible signal, the cylinder being of such a length that the limit switch will only be actuated when the bolt has been displaced by the spring towards its doorlocking position when the door and its bolt plate are not in their required relative positions.

1 3. A safety system which comprises a fluidflow control valve (as defined above) having a lever which is secured to the valve spindle and which carries a cylinder lock which includes a detent which is positionable, upon operation of the lock by a key, to engage a portion of fixed means to maintain the lever in that position thereof which corresponds with the fully open or the fully closed condition of the valve.

14. A safety system as claimed in Claim 13, wherein said valve incorporates a switching device which is operated by said detent when said detent engages said portion of said fixed means.

1 5. A safety system as claimed in Claim 14, wherein said switching device is pneumatic or electrical and is provided either to activate an informing device (e.g. a flashing red light, a Klaxon, a legible indicator board) or to operate another mechanism (e.g. a door bolt).

1 6. A safety system as claimed in any one of the preceding Claims 13 to 1 5, wherein the fixed means comprises a plate which is secured directly to the valve body and which has an elongate arcuate channel along with a barrel of said cylinder lock is moved whenever the lever is actuated to bring the valve into its fully open or fully closed condition.

17. A safety system as claimed in Claim 16, wherein the detent of the cylinder lock is movable by said key, when the barrel of the lock is at a unique end of said channel, in an arc through approximately 1 800 from a first attitude thereof in which further movement of the lever is not prevented to a second attitude thereof in which further movement of the lever is prevented by the detent engaging said portion of the fixed means.

1 8. A safety system constructed, arranged and operable substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

19. Any features of novelty, taken singly or in combination, of the embodiments of the invention hereinbefore described with reference to the accompanying drawings.