GB2206662A - A safety system for machinery having exposed moving parts - Google Patents

Abstract

A safety system for machinery, such as an agricultural baler or tractor, having exposed moving parts, comprises a mechanism (67), for deactivating the drive means and/or (66) for decoupling the machinery from the drive means, at least one sensor device (55, 56) at an exposed location in the vicinity of the moving parts of the machinery and a detector circuit (61, 62, 63, 70, 85) operable to trigger the said deactivation or decoupling means (67, 66) upon actuation of the sensor device (55, 56), the sensor device comprising an exposed housing which can be triggered simply by striking or pressing with the hand or any part of the body. Means (70) may be provided for discriminating between deliberate emergency operation of a sensor (55, 56) and an accidental impact such as may occur during normal use of the machinery. <IMAGE>

Description

A SAFETY SYSTEM FOR MACHINERY HAVING EXPOSED MOVING PARTS The present invention relates to a safety system for machinery having exposed moving parts and is particularly, although not exclusively, directed to agricultural machinery.

Farming is widely recognised to be the most dangerous occupation and although many attempts have been made to reduce the frequency of serious accidents very little impact has been made. A primary reason for the large number of accidents lies in the structure of the farming industry: although this is an industry which employs a very large number of people it is fragmented into a considerable number of individual relatively small enterprises. Because of this agricultural workers very often perform their duties alone and, by the very nature of farming, in locations remote from transport and communications. Added to these factors is the fact that agricultural machinery almost inevitably has exposed moving parts because of the nature of the operations which the machinery performs on crop or other agricultural products which must be gathered from the field.There are many regulations governing the protection of industrial workers in factory environments, which require stringent safety measures to be taken to prevent contact between operators and the moving parts of industrial machinery. Strong guards and protective enclosures are required by these regulations in almost all industrial environments except that of agriculture and this has lead to a number of quite horrific accidents occuring leading to terrible injuries which have maimed and mutilated unwary agricultural workers and has lead all to often to fatal accidents.

of all the accidents which can happen with moving machinery the most terrifying for agricultural workers must be the prospect of becomng trapped in the machinery by, for example, clothing or a limb, and repeatedly ir.,lred upon successive strokes of the machinery. Recent reports have highlighted the plight of lone workers trapped in moving agricultural machinery the drive power for which is extremely high so that the entrapment of a human limb in the machinery will not lead to stalling of the drive motor but rather to repeated injury.Although the prime mover or drive means is provided with a cut out switch this can only be reached from a small range of positions and the nature of agricultural machinery, particularly that drawn behind and driven by an agricultural tractor, is such that it is impossible to reach the cut out switch from most positions where a worker may be caught in the machinery itself. A typical example of this situation, which will be used, without limitation, to illustrate the present invention, is the conventional baling machine used to pick up dried grass from a windrow and to compact this into square bales, tying the bales with twine to maintain their shape and subsequently ejecting the compacted and tied bale from the machine.The pick up of dried grass from the windrow is effected by using a rotary mechanism having a large number of projecting sharp spring loaded tines which are driven so as to rake the ground lifting the windrow and carrying it to a transverse conveyor comprising a number of projecting spikes driven in a recirculating elongate orbit in such a way as to displace the grass into a compacting station where it is successively rammed into a bale chamber by a massive ram driven with considerable inertia by a fly-wheel and carrying at one edge a shear blade which engages a stationary shear blade at the entrance to the bale chamber for the purpose of shearing each charge of grass as it is gathered by the transverse conveyor into the entrance to the bale chamber. Because the windrow is gathered from an open location on the field this machinery is exposed and has no guard over it.

In normal working conditions the operator is safely located on the seat of the tractor and the moving parts of the machinery are of no danger. However, there are many operating conditions when the baling machine fails to wcrk properly: for example, if the grass is inadequately dried before being gathered it can rid to clog in the machinery. The farm worker may nevertheless wish to continue with the baling operation because imminent bad weather may be threatening to spoil the whole crop and it has been known for the tractor driver to leave his seat and seek to clear a blockage at the entrance to the machinery whilst the machine is still in operation.Although this is clearly a highly dangerous thing to do the pressures on the operator to complete the task in hand as quickly as possible frequently override prudence, and the time taken for the baler to be disengaged from the tractor drive, and for the mechanism to slow down, particularly in view of the rotational inertia of the fly-wheel, involves a not inconsiderable loss of operating time. Incidents have been reported where an operator has been caught at the entrance to a baler and dragged into the machinery to have a limb amputated by the bale ram. Onoe trapped by the machinery there is nothing that an operator can do to prevent its continued operation and the present invention seeks to provide a safety system by means of which such accidents can be avoided or at least their worst effects be mitigated.

According to one aspect of the present invention a safety system for machinery having exposed moving parts, comprising a mechanism for deactivating the drive means and/or decoupling the machinery from the drive means, at least one sensor device at an exposed location in the vicinity of the moving parts of the machinery, and a detector circuit operable to trigger the said deactivation or decoupling means upon actuation of the sensor device.

According to another aspect of the present invention a safety system for machinery having exposed moving parts comprises a mechanism for deactivating the drive means and/or decoupling the machinery from the drive means, at least one sensor device at an exposed location in the vicinity of the moving parts of the machinery, and a detector circuit operable to trigger the said deactivation or decoupling means upon actuation of the sensor device, and including means for discriminating between deliberate emergency operation of the sensor and operation due to an accidental impact.

There are some machines which, by their very nature, are exposed to many different impacts. For example, a baling machine may be struck by a bale during use since there is very often other machinery in the field at the same time as the baler. For example, a hay wagon and operators picking up completed bales for transport to a storage location may shed a bale to fall on the baler or in its path. Likewise, in normal transport, the baler may be inadvertently caught against overhanging trees, a gateway or any other obstruction and it is important that the safety system should not operate in such circumstances to deactivate the engine since the very act of deactivating the engine in such circumstances may itself cause risk of injury to the operator.

Various different systems for discriminating between operation of the sensors in a real emergency and spurious or accidental operation of the sensors may be employed.

In one embodiment the discrimination means may comprise a delay circuit operable to detect the duration of operation of the or a sensor device and to transmit an energising signal therefrom only if the sensor device is maintained in its operative state for a predetermined time period. This predetermined time period could be extremely short, for example a fraction of a second, but it will be appreciated that an impact occuring accidentally may be very much shorter than, for example, half a second, and in the event of an accident an operator would know that the sensor had to be maintained in its energised state rather than merely being triggered by a brief contact. This would be a matter of training and practice undertaken as a prudent preliminary to use of the machine.

The discrimination means may alternatively include a coincidence detector and a delay circuit operable to detect repeat operation and/or maintained operation of the or a sensor within a predetermined period of time commencing with the first instant of actuation, and to transmit an energising signal therefrom only if the sensor device is operated a second time within the said predetermined time period or maintained in its operated state for the said predetermined period of time. This alternative system would overcome the risk of the engine being switched off as a result of accidental energisation by impact since the second impact is unlikely to occur.

Again, training of operators to strike a sensor pad twice could be undertaken in order to ensure that all operators know how to use the safety system fitted to the machinery.

Alternatively, or in addition to the other measures the or each sensor may be provided with a shroud or guard the shape of which is such as to inhibit accidental operation of the sensor but which permits deliberate operation thereof. Such a guard may, for example, comprise an upstanding rib or ridge surrounding the sensor which necessitates the operator placing a hand or finger into the space protected by the guard.This guard need not extend to a great extent around the sensor since, obviously, it must be highly accessible to the operator, but it is envisaged that a ridge protecting, for example, one half to one inch in advance of the or a sensor could act to prevent operation by, for example, overhanging branches or the occasional impact by bales or other relatively large objects whereas the hand or a finger of the operator could nevertheless gain access to the sensor without difficulty and without requiring any precise coordination in locating it bearing in mind that in an emergency the operator may well be trapped by one or other of his or her limbs, or by an item of clothing, and may not necessarily be able to view the safety sensor clearly or at all.

A further alternative means for discriminating between accidental and deliberate actuation of the sensor device may include the provision of two or more closely spaced sensor actuator devices and a detector circuit operable to deactivate the drive means or decouple the machinery from the drive means only when two or more sensor devices are actuated simultaneously or in close temporal coincidence.

In another embodiment the or each sensor device is so shaped as to require displacement of a part thereof remote from an exposed face in order to effect actuation.

Such sensors may be considered as grip-type" sensors, namely those which require an operator's hand to pass at least partly around the sensor to operate it. A grab handle in the form of an elongate element housed in a recess, or a ccrd in a form similar to the communication cord in a railway train may be employed in such an arrangement. Again, such an embodiment may be formed with a configuration such as to require actuation by the approach of relatively spaced parts thereof, such as by gripping or pulling a movable part. One such embodiment, which will be described in more detail below, is formed as a generally tubular resilient support member with electrical contact on the interior thereof which can be brought together to close an electrical circuit by pulling or squeezing the tubular support at any point along its length.Such an embodiment opens the possibility of the provision of a single sensor over an extended area since an elongate tubular resilient support member of the form outlined above may be shaped so as to pass along the whole of the region of an exposed section of machinery so as to be operable from any point along its length. This could be of particular convenience for static machinery such as that including conveyor belts for egg packing stations and other working environments where an operator may "patrol" a relatively extensive region where there are a number of different pieces of machinery working.

In a more sophisticated embodiment the sensor device is a photoelectric detector in a location such as to be triggerable, in the event of an emergency, merely by the presence of an obstruction between itself and a light source. Such a photoelectric detector could readily be housed in a cavity or recess in the casing of a machine the size of which is sufficiently narrow to make it unlikely that any object would enter accidentally, but into which an operator's hand or finger could be introduced quickly and easily if an emergency should occur requiring the machinery to be switched off. Again, such a cavity could be made elongate so that the deactivation of the machinery could be triggered from any point along its length thereby avoiding the necessity for a large number of closely spaced individual sensors.

The present invention also comprehends a safety system for machinery attachable to an agricultural tractor, comprising one or a plurality of sensors in a circuit operable to deactivate the tractor engine and/or to decouple it from the machinery in the event of actuation of any one or more of the sensors, and including a further safety device enabling the sensor located in the tractor cab and operable to enable the safety device when an operator is not in the tractor cab and to disable the safety device upon entry of an operator into the cab.

Such a disabling sensor may be in the form of a switch mounted to detect the operator's weight on the seat and to open an electrical circuit of the safety device when the operator is seated thereon. A safety system of this type would only protect an individual operator, however, and a different system would be required if the tractor driver were to work in cooperation with other operators who may themselves be subject to risk.

The means for deactivating the drive may comprise a latching solenoid operated stop mechanism attachable to a diesel engine fuel pump and operable, when energised, to displace the fuel pump control lever to turn off the supply of fuel to the engine. Diesel engines are particularly sensitive to the supply of fuel and cease to function almost immediately, without any substantial "fly-wheel effect" when the fuel supply is cut off, due to the high compression ratio employed for such engines.

Many diesel engines, particularly those on agricultural tractors, have an engine stop mechanism in the form of a control rod linked to the fuel control lever and selectively positionable in one of first and second end positions corresponding to positions of the fuel control lever for turning the fuel supply on and off respectively.In order to overcome the fact that the fuel control lever is in such a system effectively fixed in the fuel valve open position the fuel control lever may be formed in two parts pivotally connected together end to end and resiliently biased to a configuration in which the two parts are at least substantially aligned with one another for movement together, the first of the said two parts being connected at its free end to the said control rod and the second of the said two parts being fixed for rotation with the fuel control valve and having engagement means contactable by the movable member of the said stop mechanism whereby to turn this, against the action of the resilient biasing means, to cause the fuel valve to close whilst the first part of the fuel control lever is maintained by the control rod in the position adopted when the valve is open.

The said stop mechanism may comprise a plunger resiliently biased towards a first, projecting, position and held in a second, retracted, position by a solenoid operated latch mechanism actuated to release the plunger upon energisation of the solenoid.

Machinery driven by a separate motor may, however, have considerable inertia, and merely switching off the engine may not be sufficient to cause immediate cessation of motion. In such a case additional means for stopping the motion may be incorporated, including brakes actuated in response to energisation of the sensor and/or physical stop means for the machinery. Since it is practically impossible to stop the roation of a fly-wheel instantaneously it is proposed that in machines having such an energy store the safety system incorporates means for uncoupling the driven machinery from the fly-wheel, and one arrangement for effecting this may include a solenoid operated latch mechanism operable to introduce an abutment stop into the path of a movable member of the machinery whereby to cause fracture of a frangible link in the drive train to the machinery.It is known to provide such a frangible link in the form of a shear pin in the drive to the fly-wheel in order to protect the drive train itself in the event of jamming of the machinery, for example if the mechanism should get out of phase.

In another aspect the present invention provides a safety system for machinery having exposed moving parts, comprising a mechanism for deactivating the drive means and/or decoupling the machinery from the drive means, at least one sensor device at an exposed location in the vicinity of the moving parts of the machinery, and a detector circuit operable to trigger the said deactivation or decoupling means upon actuation of the sensor device, in which the or each sensor device has a torch pad the contact surface of which extends over an area having two transverse dimensions of substantially similar extent. The or each sensor may comprise a microswitch in a housing having a hinged cover constituting the contact surface of the sensor.

The present invention also comprehends a safety system attachable to a diesel engine fuel pump operable to turn off the supply of fuel on arrival of a triggering signal such as from a detector, switch or the like, comprising a resiliently displaceable actuator rod urged in a first direction, and electrically releasable latching means connectable to a machine safety circuit to receive triggering signals, the actuator rod being guided in a guide housing attachable to a fuel pump such that its projecting end engages a fuel pump lever to turn off the fuel supply upon displacement of the actuator rod by the resilient biasing means upon release by the electrically energised trigger means.

Various embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an agricultural baler, in simplified form, illustrating the provision of sensors forming part of a safety sytem at strategic locations; Figure 2 is a schematic perspective view of a first type of sensor usable with the safety sytem of the present invention; Figure 3 is a schematic perspective view of a second form of sensor; Figure 4 is a schematic view of a third form of sensor; Figure 5 is a cross-section through a further type of sensor; Figure 6 is a circuit diagram illustrating the electrical components of a safety system formed as an embodiment of the invention;; Figure 7 is a schematic view of a fuel valve control mechanism formed as part of the system of Figure 6 shown in a first operating position; Figure 8 is a view similar to that of Figure 7, showing the mechanism in a second operating state; Figure 9 is an enlarged sectional view of the valve control mechanism of Figures 7 and 8, taken on the line IX-IX of Figure 8; Figure 10 is a schematic side view of a baler illustrating the provision of a safety link forming part of the system of the present invention; Figure 11 is an enlarged partly sectional view of a part of the linkage illustrated in Figure 10; and Figure 12 is a schematic circuit diagram illustrating one way in which the system of the present invention may be made fail-safe.

Referring now to the drawings, the baler illustrated is generally identified with the reference numeral 30 and comprises a main ram body 31 having an input drive shaft 32 driving a fly-wheel 33 which via a bevel gear mechanism (not shown) drives a crank within the ram body causing a bale ram to reciprocate back and forth in the direction cf the longitudinal axis of the ram body 31.

Hay is delivered into the bale chamber within the ram body 31 by a pick up and feed system housed in a laterally extending section 34 which carries a rotary pick up 35 having a plurality of radially extending spring tines rotated in an anti-clockwise direction as viewed in Figure 1 so as to pick up hay from a windrow and deliver it into the opening 36 within which operate a plurality of transfer spikes (not visible in the drawing). As will be appreciated the entrance to the bale chamber is exposed and unprotected, and the moving pick up tines are likewise unguarded so that if, in the event of malfunction of the machine, an operator should try to release the crop from this region there is a serious risk that he may be caught up by the tines and/or by the transfer spike and injured not only by these, but more seriously by the ram and/or its shear blade. In order to prevent this the safety system of the present invention provides for the fitting of a number of sensors in positions where are readily accessible to an operator, and sensors 37, 38, 39 and 40 have been illustrated in Figure 1. It will be appreciated, however, that a greater number of individual sensors may be provided distributed over different parts of the machinery wherever a potential risk of injury and a need to be able to switch off the machine quickly is foreseen.

The sensors 37 and 38 are provided on either side of the entrance to the crop opening 36 for operation in the event of an accident occuring whilst the operator is standing in this area. The sensor 39 is provided for use in the event of an accident occuring in the vicinity of the fly-wheel 33 and the sensor 40 is provided for operation in the event of an accident occuring in the vicinity of the drive shaft 32.In this latter respect it is appreciated that the drive shaft should be provided with a stationary cover, but in practice the stationary cover is held stationary only by a light chain and, after a number of years of service, this chain may become rusted and weak and may fail in service as, indeed, may the cover itself and the intention in providing the safety system of the present invention is to provide a last ditch emergency measure which can save life and/or limb in circumstances where other factors, including the exercise of reasonable prudence, have failed.

The precise nature of the sensor pads 37, 38, 39 and 40 may vary in dependence on the nature of the environment into which they are intended to be fitted. For an agricultural baler as illustrated in Figure 1 it is appropriate for the sensors 37-40 to be as large as possible and to present a wide area for contact by a user. For this purpose, as illustrated in Figure 2, the sensor may be in the form of a microswitch housed in a casing having a base 41 over which extends a cover 42 pivotally connected at 43 along one edge of the base 41 so that, upon depression of the cover 42, the microswitch (not shown) can be actuated. Figure 2 also illustrates the provision of a plurality of such sensors closely adjacent one another and the detector circuit may require the simultaneous depression of two or more of the touch pads.

Figure 3 illustrates an alternative arrangement in which a casing 44 has a cavity 45 spanned by an elongate handle 46. To operate the sensor it is necessary to insert the hand into the cavity 45 and grip the sensor handle 46 to exert a force on this. The handle 46 is mounted resiliently in the casing 44 spaced from electrical contact (not shown) so that a downward or outward force on the handle 46 will cause the contacts to close completing an electrical circuit to energise the safety system.

A similar sensor is shown in Figure 4 where, instead of physical movement of the handle 46 there is provided a number of displaceable elements 47, 48 carried on a transverse rigidly mounted handle 49 in a cavity 50 in a casing 51 similar to the casing 44. Such an arrangement prevents unwanted or accidental actuation since the movement which triggers energisation of the safety system is displacement of the movable members 47, 48 which can only be effected by contact with the fingers of an operator's hand as these pass round the handle 49 to grip it. The movable members 47, 48 can be coupled to highly sensitive microswitches so that the slightest movement of the movable member triggers actuation of the safety system.

A similar grab handle type of sensor is illustrated in Figure 5 where, instead of a rigid handle 49 as in the embodiment of Figure 4, there is a flexible tubular handle 52 having a plurality of electrical contacts 53 spaced around its interior and held from a central electrical conductor 54 by the resilinece of the tube.

Any deflection of the tube by bending, or by squeezing, will cause one of the contacts 53 to touch the central contact 54 thereby closing the sensor circuit. Although a relatively large space has been illustrated in Figure 5 it will be appreciated that the gap between the central contact 54 and the contacts 53 on the inside face of the tubular handle 52 may be made extremely small so that the degree of movement necessary to achieve electrical contact is ver fine.

Figure 6 illustrates a safety circuit comprising two sensors 55, 56 which may be of any type such as those described in relation to Figures 2 to 5 or any other type suitable for the system. One contact of each of the sensors 55, 56 is connected to a negative line 57 by a branch line 58 which also leads to a socket 59 by which the safety equipment can be connected to other machinery, for example a trailer if the safety circuit is mounted on a tractor or, conversely, a tractor if the safety system is mounted on the trailer or other trailed machinery.

A positive line 60 connected to a source of electricity has a branch line 61 feeding a relay 62 in the primary circuit of which the sensors 55 and 56 are connected in parallel, and the secondary circuit of which is connected between the negative line 57 by a branch line 63 and a plurality of electrical operating circuits, namely a brake operating circuit 64 a horn energising circuit 65 a pump switching circuit 66 and an auxiliary circuit 67.

These four circuits are connected in parallel between the positive line 60 and the secondary circuit of the relay 62, in parallel with a light emitting diode 68. The positive line 0 has a controlling or enabling switch 69 between itself and the positive pole of the power supply so that it can be selectively enabled or disabled depending on circumstances. As foreshadowed hereinbefore the enabling switch 69 may be fitted as a normally closed switch on a tractor seat, which is opened when the weight of the operator is resting on the seat thereby disabling the circuit, and which closes when the operator leaves his seat thereby automatically enabling the safety circuit whenever the tractor driver is not in position.

The circuit may also include a delay line generally indicated 70 and shown in broken outline in Figure 6 operative to perform a discriminatory function as will be described below.

When a sensor pad 55 or 56 is closed the circuit through the line 61 and the primary circuit of the relay 62 is completed to the negative line 57 thereby causing the secondary circuit of the relay to close allowing current to flow from the line 60 through the control circuits 64, 65, 66 and 67 to the negative line 57. The light emitting diode 68 is similarly energised. The brake circuit 64 may act, in a manner which is not described in greater detail herein, but which will be apparent to those skilled in the art, to apply the vehicle brakes in response to the arrival of an electrical signal: this can be achieved by use of an appropriate relay and solenoid actuator system. Likewise, the horn circuit 65 acts, when current flows through it, to energise the vehicle horn. The pump circuit 66, on the other hand, acts in a manner which will be described in more detail with reference to Figures 7, 8 and 9, to turn off the supply of fuel to the engine thereby causing immediate cessation of movement. The auxiliary circuit 67 may be used for any additional purpose in systems requiring a secondary line of action, for example in complex machinery where cessation of movement may require closing of an inlet gate to prevent the arrival of further raw material the auxiliary circuit 67 may be used for this purpose.

The delay line 70 in the circuit between the sensor pads 55, 56 and the relay 62 acts, if provided, to ensure that the operation of the sensors 55, 56 is deliberate and not accidental by introducing a limited delay, for a period in the region of, for example, half a second, between arrival of an initiating signal from the sensor 55 or 56 and connection of this signal to the primary circuit of the relay 62. After the predetermined delay if the signal is still present from the pad 55 or 56, or if it appears again within a predetermined minimum time period, the relay 62 will be energised.

Turning now to Figures 7, 8 and 9, the former two illustrate a diesel engine fuel pump 71 having a fuel control lever 72 which is a rocker lever mounted on a spindle 73 which controls operation of a fuel valve closure of which starves the pump 71. The lever 72 has two arms 72a and 72b the latter of which is connected by a control rod 74 to a knob 75 passing through a panel 76 in the casing. The panel 76 is provided with any known form of locking means, for example a keyhole slot, which allows the knob 75 to be held in the position illustrated in Figure 7 in which the fuel valve is open. In normal operation the knob 75 is pulled to turn off the diesel engine, after having first lifted the knob 75 out of the narrow part of the keyhole slot to permit longitudinal displacement of the control rod 74.Since, when the engine is running normally, the knob 75 is held fixed in position the lever 72 cannot be turned about the axis of the spindle 73 and for the purpose the parts 72a, 72b are formed separately with the part 72a being mounted on the spindle 73 and the part 72b being pivotally mounted on the part 72a and resiliently biased by a spring 77 into the aligned configuration illustrated in Figure 7.

Mounted on the fuel pump 71 is an emergency stop mechanism generally indicated 78 having a push rod 5 passing through a main body 18 thereof and aligned with an abutment stop 79 of the first part 72a of the lever 72. Vpon arrival of an energising signal from the relay 62 the stop mechanism 78 acts to cause the actuating arm 5 to be displaced from the position illustrated in Figure 7 towards the left to the position illustrated in Figure 8. Here it will be seen that the end off the rod 5 has contacted the abutment stop 79 and caused the first part 72a of the lever 72 to rotate in a clockwise direction about the axis of the spindle 73 turning this latter to the position corresponding to closure of the fuel supply valve controlled thereby.In effecting this movement the second part 72b of the lever 72 remains in the position in which it is held by the control rod 74 and the lever 72 effectively "breaks" by turning about the pivot 80 between the first and second parts of the lever 72. The rod 55 has a knob 13 at its end remote from that which contacts the abutment 79 of the first part 72a of the lever 72 to enable resetting in a manner which will be described in relation to Figure 9 hereinbelow. The same mechanism may be used unchanged on engines in which a cable is used in place of the control rod 74.

Turning now to Figure 9 the stop mechanism illustrated comprises, as has been mentioned above, an actuating rod 5 which passes entirely through the body 18 from end to end and projects out of each end with an operating tip 5a at one end and a knob 13 at the other. The body 18 is generally cylindrical and has two brackets 6, 11 secured by screws 7, 12 respectively by means of which it can be attached to a fuel pump such as the pump 71 illustrated in Figures 7 and 8. Mounted over the body 18 by means of a bracket 23 is a solenoid 2 having a winding 20 and an armature 1 with a transverse pin 19 which engages one end of a rocker lever 17 pivoted at 15 in an opening in the body 18 and resiliently biased by a spring 16 to turn in the anti-clockwise direction as viewed in Figure 9.

The end of the rocker lever 17 has a nose 82 which engages a shoulder 22 of the rod 5 defined by a conically tapered section 21.

The interior bore of the housing 18 has an enlarged chamber closed at one end by a plug 4 through which the rod 5 projects and within this chamber the rod 5 is provided with a collar 8 secured in place by a transverse pin 9 and engaged by a compresison spring 10 compressed between the collar 8 and the shoulder 83 at the inner end of the chamber remote from the plug 4.

The solenoid 2 is connected to a terminal block 3 by two wires 84 and the terminal block 3 is itself connected in the circuit illustrated in Figure 6. Thus, when the relay 62 of Figure 6 is energised to allow current to flow through the circuit from the positive supply line 60 the solenoid winding 20 is energised attracting the armature I inwardly and causing the pin 19 to turn the lever 17 clockwise about the pivot 15 until the nose 82 is lifted out of engagement with the shoulder 22 whereupon the spring 10 can expand, no longer being restrained by the engagement of the shoulder 22 by the nose 82 of the lever 17, and the rod 5 is thereby thrust axially causing the tip 5a to engage the abutment plate 79 of the rocker lever 72 turning this in a clockwise direction as viewed in Figures 7 and 8 to close the valve controlled by the spindle 73.

The relay 62 is a latching relay which is reset upon depression of a reset button 85 so that any attempt to withdraw the rod 5 by pulling on the knob 13 whilst the signal fro the sensor pad 55 or 56 is still present will result in immediate triggering of the stop mechanism again so that the device is effectively fail safe. When the relay is de-energised, however, the traction applied to the knob 13 will alloy the nose 82 to drop back into the recess defined by the tapered portion 21 of the rod5, re-engaging the shoulder 22 by the action of the spring 16, this latter also resetting the armature 1 of the solenoid 2.

Turning now to Figures 10 and 11 there is shown an adaptation of a baler safety mechanism for incorporation into the safety system of the presnt invention. As is known, the needles which feed twine into the knotting mechanism of a baler are maintained in accurate and close synchronism with the bale ram in order to ensure that the ram does not advance into contact with the needles during normal operation thereof since this would cause catastrophic damage to the knotting mechanism. In order to guard against any possible mis-timing of the mechanism, particularly immediately after the knotting mechanism has performed its operating cycle, there is provided a linkage between the needle mechanism and the ram in the form of a latch which is displaced into a position obstructing the ram when the needles are in the elevated knotting position.

In Figure 10 the needles of a baler are identified with the reference numeral 86 and the latch with the numeral 87, these normally being interlinked by a tie rod 88 driven by its connection to a lever 89 rotation of which about its pivot 90 causes the needles 86 to be raised for a knotting operation. In this embodiment the tie rod 88, instead of being connected by the usual bell crank to the latch 87, is connected to a pivoted link 91 turnable about an axis 92 and joined by a connection mechanism 93 to the latch bell crank (not illustrated). The whole assembly is biased by a spring 94 towards the latch-engaged position and maintained in the latch-disengaged position by the tension in the tie rod 88 when the needles are in their lowered inoperative position as illustrated in Figure 10.

The link mechanism 93 is illustrated in greater detail in Figure 11. This comprises a body 95 having an internal cavity receiving a link 96 connected to the latch 87 and retained in place in the body 95 by a pin 97 which passes through aligned apertures (not illustrated) in the body 95 and the link 96.

The pin 97 is housed within a casing 98 having a cylindrical bore 99 within which slides a plunger 100 connected rigidly to the pin 97 and resiliently urged by a spring 101 away from the connector body 95. The plunger 100 has a triangular section groove 102 defining a shoulder 103 engaged by a solenoid armature 104 of a solenoid 105. The armature 104 has an inclined end face 1Q6 the inclination of which matches that of the triangular groove 103 in the plunger 100.The solenoid 105 is connected, for example as the auxiliary circuit 67 in the circuit of Figure 6 so that, upon energisation of the circuit by triggering a sensor pad 55 or 56, current flows through the auxiliary circuit 67, namely through the solenoid 105 causing the armature 104 thereof to retract allowing the plunger 100 to be urged by the spring 101 away from the link connector body 95 withdrawing the pin 97 from the aperture in the link 96.

The spring 94 can then displace the latch 87, via its conventional bell crank (not shown) into the path of the bale ram despite the fact that the needles 86 may be in their lowered positon as illustrated in Figure 10.

Before the ram can advance to a position where it may cause damage, for example to a trapped operator, it strikes the latch 87 which stops its movement immediately The energy stored in the fly-wheel is not dissipated by this, however, and this results in shearing of the safety shear bolt with which the fly-wheel is provided. The whole of the baler mechanism is brought to an immediate halt whilst the fly-wheel is allowed to continue rotating without transmitting energy thereto.

In the event of a potentially damaging event, therefore, the operator may strike or pull any of the nearby sensors, such as the sensors 37 or 38 illustrated in Figure 1, and this will result in the baler machiner being brought to a dead stop by decoupling it from the tractor engine whilst, at the same time, the tractor engine is also immediately stopped as discussed in relation to Figures 7 to 9.

After an extended period of service, particularly in a robust agricultural environment the machinery to which the system of the present invention has been fitted may be subjected to stresses and shocks and/or the deteriorating effect of wind and water which may result in loosening of connections or fracture or rupture of component parts resulting in a discontinuity in the circuit. Since the system of the present invention is intended only to be used in an absolute emergency it is quite probable that long periods of time will elapse without the system being actuated at all and any small fault in the circuit or in any component of the system may therefore go unnoticed until it is discovered, perhaps too late, that the system is inoperative.

Agricultural and industrial machinery, unlike road going motor vehicles, is not subjected to periodic testing to establish its fitness for the task it has to perform. It is envisaged, therefore, that the system of the present invention will preferably include monitoring circuitry which will provide an indication that the system is in an operable state (that is, has suffered no event leading to open circuits or potential failure of components) and at least some of the system is provided with fail-safe detector means operable to trigger the circuit in the event of a failure in crucial parts thereof.

Figure 12 illustrates a typical such circuit shown applied to the wiring associated with the solenoid 20 of Figure 9. Extension of this circuit to cover the wiring and components at other points of the system will be well within the scope of those skilled in the art. In the circuit diagram illustrated in Figure 12 the solenoid winding 20 of the solenoid 2 of Figure 9, which, as will be recalled, acts, when energised, effectively to trigger closure of the fuel supply valve to starve the associated diesel engine, is connected between the emitter 105 of a transistor 106 and the negative line 57. The collector 107 of the transistor 106 is connected to the positive line 60.The base 108 of the transistor 106 is connected between two pairs of terminals 109, 110 of a socket which is connected in series between two base biasing resistors 111 and 112 which are connected in series between the positive line 60 and the negative line 57 with the interposition of a microswitch 113 and a light emitting diode 114.

The microswitch 113 is the switch of one of the sensor pads such as the pads 55, 56 in the circuit of Figure 6, but whereas in the embodiment of Figure 6 a normally-open microswitch is described, the microswitch 113 is of normally closed type. The two socket terminals 109, 110 are closed by a plug 115 which is inserted to bring the sensor 113 into operation and can, from time to time, be removed if it is desired to isolate the sensor 113 such that it is not operative to produce triggering of the circuit. Such a situation may arise, for example, for testing purposes or when operation of the sensor in a non-emergency situation is likely.For safety reasons the plug 115 is made as inaccessible as possible and, preferably, requires the use of specialist tools for its insertion and removal so that the sensor switch 113 cannot be isolated, and therefore rendered inactive, casually or carelessly.

When the plug 115 is in position the base 108 of the transistor 106 is biased to a value, determined by the relative values of the two resistors 111, 112 such that the transistor 106 is non-conducting although a small current flows through the circuit comprising the two resistors 111, 112, the microswitch 113 and the light emitting diode 114. This latter thus emits light to indicate that the part of the circuit including the wiring and the sensor switch is complete and unbroken and therefore serves to reassure the operator that the safety circuit is in place.Should any incident occur causing rupture of the wires leading between the socket 110 and the microswitch 113, or this latter and the light emitting diode 114 the voltage at the base 108 of the transistor 106 will rise towards the positive value causing the transistor 106 to turn on and allowing current to flow from its collector 107 to its emitter 105 and from there through the coil 20 thereby switching off the engine. This effect is identical to the deliberate action of opening the microswitch contacts such as by striking one of the sensor pads 37, 38, 39 in Figure 1.

Other, less critical parts of the circuit may simply be provided with light emitting diodes in series therewith (the circuit being designed such that it is pervaded by a low current, not sufficient to trigger the security response, but adequate to cause illumination of the light emitting diode) these diodes being mounted on a panel clearly visible to the machine user so that the continuity of the safety circuit can be monitored regularly to ensure that it is available for use in an emergency.

Although the present invention has been described with specific reference to its application to agricultural machinery where the problems involved with exposed moving parts are perceived to be particularly severe, it is to be understood that the present invention is not to be considered as limited thereby, and can be applied to any industrial or other environment where immediate safety from moving machinery is required.

Claims (20)

1. A safety system for machinery having exposed moving parts, comprising a mechanism for deactivating the drive means and/or decoupling the machinery from the drive means, at least one sensor device at an exposed location in the vicinity of the moving parts of the machinery, and a detector circuit operable to trigger the said deactivation or decoupling means upon actuation of the sensor device.

2. A safety system for machinery having exposed moving parts, comprising a mechanism for deactivating the drive means and/or decoupling the machinery from the drive means, at least one sensor device at an exposed location in the vicinity of the moving parts of the machinery, and a detector circuit operable to trigger the said deactivatior or decoupling means upon actuation of the sensor device, and including means for discriminating between deliberate emergency operation of the sensor and operation due to an accidental impact.

3. A safety system as claimed in Claim 2, in which the discrimination means comprise a delay circuit operable to detect the duration of operation of the or a sensor device and to transmit an energising signal therefrom only if the sensor device is maintained in its operative state for a predetermined time period.

4. A safety system as claimed in Claim 1 or Claim 2, in which the discrimination means includes a coincidence detector and a delay circuit operable to detect repeat operation and/or maintained operation of the or a sensor within a predetermined period of time commencing with the first instant of actuation and to transmit an energising signal therefrom only if the sensor device is operated a second time within the said predetermined time period or maintained in its operated state for the said predetermined period of time.

5. A safety system as claimed in Claim 1, in which the or each sensor is provided with a shroud or guard the shape of which is such as to inhibit accidental operation of the sensor but which permits deliberate operation thereof.

6. A safety system as claimed in Claim 1 or Claim 4, in which the means for discriminating between accidental and deliberate actuation of the sensor device includes the provision of two or more closely spaced sensor actuator devices and a detector circuit operable to deactivate the drive means or decouple the machinery from the drive means only when two (or more) sensor devices are actuated.

7. A safety system as claimed in any preceding Claim, in which the or each sensor device is so shaped as to require displacement of a part thereof remote from an exposed face in order to effect actuation (e.g. grip-type sensors).

8. A safety system as claimed in Claim 6, in which the or each or at least some of the sensor device or devices have a configuration such as to require actuation by the approach of relatively spaced parts thereof, such as by gripping or pulling a movable part thereof.

9. A safety system as claimed in Claim 7, in which the sensor device has a generally tubular resilient support member with electrical contacts on the interior thereof which can be contacted together to close an electrical circuit by pulling or squeezing the tubular support at any point along its length.

10. A safety system as claimed in any of Claims 1 to 5, in which the sensor device is a photoelectric detector in a location such as to be triggerable, in the event of an emergency, by the presence of an obstruction between itself and a light source.

11. A safety system for machinery attachable to an agricultural tractor, comprising one or a plurality of sensors in a circuit operable to deactivate the tractor engine and/or to decouple it from the machinery in the event of actuation of any one or more of the sensors, and including a further safety device enabling sensor located in the tractor cab and operable to enable the safety device when an operator is not in the tractor cab and to disable the safety device upon entry of an operator into the cab.

12. A safety system as claimed in Claim 10, in which the disabling switch is mounted to detect the operator's weight on the seat and to open an electrical circuit of the safety device when the operator is seated thereon.

13. A safety system as claimed in any preceding Claim, in which the means for deactivating the drive means comprise a latching solenoid operated stop mechanism attachable to a diesel engine fuel pump and operable when energised to displace the fuel pump control lever to turn off the supply of fuel to the engine,

14.A safety system as claimed in Claim 12 for a diesel engine having an engine stop mechanism in the form of a control rod linked to the fuel control lever and selectively fixable in first and second end positions corresponding to positions of the fuel control lever for turning the fuel supply on and off respectively, in which the fuel control lever is formed in two parts pivotally connected together end to end and resiliently biased to a configuration in which the two parts are at least substantially aligned with one another for movement together, a first of the said two parts being connected at its free end to the said control rod and the second of the said two parts being fixed for rotation with a fuel control valve and having engagement means contactable by the movable member of the said stop mechanism whereby to turn this against the action of the resilient biasing means to cause the fuel valve to close whilst the first part of the fuel control lever is maintained by the control rod in the position adopted when the valve is open.

15. A safety system as claimed in Claim 12 or Claim 13, in which the said stop mechanism comprises a plunger resiliently biased towards a first, projecting, position and held in a second, retracted, position by a solenoid operated latch mechanism actuated to release the plunger upon energisation of the solenoid.

16. A safety system as claimed in any preceding Claim, in which the means for uncoupling the driven machinery from the drive means include a solenoid operated latch mechanism operable to introduce an abutment stop into the path of a movable member of the machinery whereby to cause fracture of a frangible link in the drive train to the machinery.

17. A safety system for machinery having exposed moving parts, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

18. A safety system attachable to a diesel engine fuel pump operable to turn off the supply of fuel on receipt of a triggering signal such as from a detector, switch or the like, comprising a rectilinearly displaceable actuator rod resiliently urged in a first direction, and electrically releasable latching means connectable to a machine safety circuit to receive triggering signals, the actuator rod being guided in a guide housing attachable to a fuel pump such that its projecting end engages a fuel pump lever to turn off the fuel supply upon displacement of the actuator rod by the resilient biasing means upon release by the electrically energised trigger means.

19. A safety system for machinery having exposed moving parts, comprising a mechanism for deactivating the drive means and/or decoupling the machinery from the drive means, at least one sensor device at an exposed location in the vicinity of the moving parts of the machinery, and a detector circuit operable to trigger the said deactivation or decoupling means upon actuation of the sensor device, in which the or each sensor device has a touch pad the contact surface of which extends over an area having two transverse dimensions of substantially similar extent.

20. A safety system as claimed in Claim 19, in which the or each sensor comprise a microswitch in a housing having a hinged cover constituting the contact surface of the sensor.