A magnetic switch for a working machine and a magnetic switch activation system therefor

Abstract

A magnetic switch activation system comprises a first part 12 and a second part 42 moveable relative to each other in a movement plane. The first part comprises a body having two arms 16,18 and a spac

Description

FIELD The disclosure relates to magnetic switches, particularly magnetic switches for use in working machines. BACKGROUND Magnetic switches are known and are used in a variety of industrial applications. For example, they are used in elevators in buildings to indicate that the elevator car has reached the correct position on a floor. They are also used in working machines in a variety of applications. For example, they may be used in the braking system to indicate to the machine controller that the driver has activated the parking brake so as to control the vehicle system, e.g. hydraulics in a particular way, for example to activate or deactivate particular hydraulic circuits. In one working machine application, they are used in one of the side pods in the driver cabin to indicate to the vehicle control system that a side pod is in the elevated position, allowing the driver to exit the vehicle, in which case the vehicle control system may deactivate the vehicle hydraulics in relation to, for example, an excavator arm or a shovel. That prevents the inadvertent operation of those tools when the driver is not in a position to control them. The magnetic switch also indicates when the side pod is in the lowered position, which signals to the vehicle control system that the driver is in position to control the tools on the working machine and thus may reactivate those hydraulic circuits. One such known magnetic switch is a vane switch made by Elobau GmbH &Co. KG of Leutkirch, Germany. One known form of magnetic switch activation system for the known magnetic switch is illustrated in Figs.1-4 in the context of a working machine side pod application. A known magneticswitch 10 is best illustrated in Fig.4. The switch comprises a first switch part 12, having a body 14, which is U-shaped in cross-section with two arms 16, 18 spaced apart from each other by the recess 20 of the body 14. The arms 16, 18 each have a length L so that the space between the arms is an elongate channel running in the direction from the floor of the cab of the working machine to the cab ceiling. The arm 16 contains an electrical switch 22 at the free end of the arm 16. The other arm 18 contains a permanent magnet 24, again at the free end of the arm 18. The switch 22 is arranged in electrical communication with a control system of a working machine WMCS. The magnetic switch 10 has a second part 26. The second part 26 comprises a mounting 28 and a switch operator member 30. The switch operator member 30 is formed of a ferromagnetic material, such as iron or ferromagnetic steel and is in the form of a flat plate or "flag". The electrical switch 22, for example, has an 'on' position and an 'off' position and is biased by means of a spring, into the 'on' position (i.e. it is a "normally closed" switch). The magnetic force applied by the permanent magnet 24 on the electrical switch 22 is sufficient to overcome the bias of the spring to pull the electrical switch into the 'off' position. Interposing the switch operator member 30 into the space between the arms 16, 18 has the effect of interfering with the magnetic field generated by the permanent magnet 24, which in turn weakens the effect of the magnet on the electrical switch 22 allowing the electrical switch to move to the 'on' position under the action of the spring bias. The interposition / removal of the rigid ferromagnetic flag switch operator member into / out of the space constitutes the known magnetic switch activation system. It is also known for vane switches of this configuration to be of the "normally open" or "change-over" (single pole double throw) type. Fig.l shows the magnetic switch of Fig.4 in use in a working machine side pod S. The side pods of the type shown in Figs. 1-3 are used in working machine cabs and are typically arranged one on either side of the driver / operator seat. A side pod S is hinged to the floor F of the vehicle cab and is arranged to be pivoted into an elevated position in order to allow access of the driver / operator to the seat. The pivoting movement takes place in a movement plane P-P (fig.4). The elongate channel formed by the arms is parallel with the movement plane P-P. When the driver is in place in the seat, the side pod can be pivoted down out of the elevated position into an operating position. Fig.l shows a typical side pod S in the elevated position on the right-hand side in Fig.l and in the operative position on the left-hand side of Fig.l. As shown in Fig.l, the first part 12 of the magnetic switch is mounted to the hinge base of the side pod S. The second part of the magnetic switch is mounted to the body of the side pod S itself. As shown in Fig.l, in the elevated position of the side pod, the second part of the switch, including the switch operator member, is spaced from the first part 12 of the magnetic switch. In the lowered position of the side pod, the second part 26 of the magnetic switch, and in particular, the switch operator member 30 is received within the space defined between the arms 16, 18 of the first part 12 of the switch. Figs.2 and 3, which are side sectional views of the side pod of Fig.l show the flag-like switch operator member 30 arranged in the space between the two arms 16, 18. In Figs. 1-3, the floor of the cab of the working machine / vehicle is shown with a dot dashed line F. Working machines which include side pods of the type shown in Figs. 1-3 are often used in rough working conditions. Over time, the first and second parts of the magnetic switch shown in Figs. 1-4 can become misaligned. In some cases, the flag-like switch operator member 30 becomes misaligned in the space between the arm 16, 18 which can result in impaired performance of the magnetic switch. For example, in some cases the switch operator member may have an insufficient influence on the magnetic field generated by the permanent magnet 24 so that it does not cause the switch to move between its operative positions. Also, when the vehicle is operating, vibrations can be transmitted from the body of the working machine / vehicle to the first part of the switch causing the first part to move relative to the second part and creating intermittent activations of the switch, which is undesirable. In extreme cases, the switch operator member 30 can be sufficiently misaligned to contact one or other of the arms 16, 18, potentially damaging either the electrical switch or the permanent magnet. It is an object of the present disclosure to provide a magnetic switch activation system and / or a magnetic switch which overcomes or assuages those issues. SUMMARY The present teachings provide a magnetic switch activation system and a magnetic switch of the appended claims. A first aspect of the teachings provides a magnetic switch activation system comprising a magnetic switch having a first part and a second part arranged to move with respect to each other. The first part may comprise a body having two arms, spaced apart from each other to define a space therebetween, one arm having a permanent magnet and the other part having an electrical switch. The electrical switch may have a first state and second state, and the electrical switch may be operable between the first state and the second state by a variation in the magnetic field generated by the permanent magnet. The second part may comprise, a mounting and a switch operator member mounted to the mounting. The switch operator member may be mounted to the mounting in such a way that the switch operator member may move relative to the mounting. The movement of the first and second parts with respect to each other may move the switch operator member into or out of the space between the arms of the first part. The presence of the switch operator member in the space between the arms may influence the magnetic field generated by the permanent magnet, causing the electrical switch to change from the first state to the second state. The switch operator member may be free to move relative to the mounting under the influence of the magnetic field generated by the permanent magnet. By allowing the switch operator member to move relative to the mount, the switch operator member can be influenced by the magnetic field generated by the permanent magnet to adopt a beneficial position within the space between the arms. In this way, erroneous operations of the switch due to misalignment of the switch operator member are reduced. Additionally, the magnetic field tends to inhibit the switch operator member from rattling if subjected to externally induced vibrations. The electrical switch may be biased into the second state by a biasing element and the electrical switch may be sustained in the first state by the magnetic field generated by the permanent magnet when the switch operator member is not in the space, and the switch operator member may comprise, at least in part, a ferromagnetic material, whereby positioning the switch operator member in the space may interrupt or weaken the effect of the magnetic field on the switch, causing the switch to move under the action of the biasing element to the second state. In this way, in one application, the uninterrupted magnetic field holds the switch in a "hydraulic" deactivation state and closing switch so that the switch operator member is in the space between the two arms interrupts the magnetic field allowing the switch to resile back to a hydraulic activation "state". Preferably, the operator member comprises a rod mounted to the mounting and a jacket surrounding the rod, the jacket being formed, at least in part, of ferromagnetic material. That arrangement allows the material of the rod to be selected for e.g. strength, and the material of the jacket to be selected for its magnetic performance. The jacket may be rigidly secured to the rod or the jacket may be movable relative to the rod or rotatable relative to the rod. Preferably the jacket is movable translationally and rotationally relative to the rod. The rod may be movably mounted to the mounting. The rod may be mounted for rotation relative to the mounting or translation relative to the mounting and preferably mounted for translation and rotation relative to the mounting. In this way, the switch operator member can float relative to the mounting so as to adopt an appropriate position under the influence of the magnetic field generated by the permanent magnet when the switch operator member is arranged in the space between the two arms. In a further alternative arrangement, the switch operator member comprises a unitary body formed of ferromagnetic material. In such a case, the unitary body may be movably and / or rotatably mounted to the mounting. The outer surface of the operator member and switch operator member may be circular or elliptical. By providing a switch operator member with a circular or elliptical surface, the risk of damaging either the switch operator member or either of the arms due to misalignment of the two parts of the magnetic switch is reduced. Where the switch operator member comprises a rod and jacket, the jacket is preferably a hollow cylinder. The hollow cylinder may comprise a body having a circular outer periphery and a circular bore formed therein, wherein the centre of the bore is offset from the centre of the periphery so that the jacket is arranged on the rod eccentrically. That arrangement puts the preponderance of ferromagnetic material on one side of the jacket, which when the switch operator member is arranged between the arms and, thus under the influence of the magnetic field, will tend to cause the switch operator member to adopt a more specific position in the space under the influence of the magnetic field. The space defined between the arms may be an elongate channel and the first and second parts may move relative to each other in a movement plane, the arms and the switch operator member being arranged such that the channel and switch operator member are orientated transverse to the movement plane. In a second aspect of the teachings, a magnetic switch may comprise a first part and a second part arranged to move with respect to each other in a movement plane. The first part may comprise a body having two arms, spaced apart from each other to define an elongate channel therebetween, one arm having a permanent magnet and the other part having a switch, which has a first state and a second state, the switch being operable between the first state and the second state by a variation in the magnetic field generated by the permanent magnet. The second part may comprise a mounting and a switch operator member mounted to the mounting, the switch operator member being mounted to the mounting in such a way that the switch operator may move relative to the mounting. The movement of the first and second parts with respect to each other may move the switch operator member into or out of the space between the arms of the first part. The presence of the switch operator member in the space between the arms influence the magnetic field generated by the permanent magnet, causing the switch to change from the first state to the second state. The arms and the switch operator member may be arranged such that the channel and switch operator member are orientated transverse to the movement plane. In the known magnetic switch configuration, the flag-like switch operator member moves in, or parallel with, the movement plane defined by the movement between the first part and the second part of the magnetic switch. What that means is that as the switch operator member begins to enter the space between the two arms, its effect on the magnetic field generated by the permanent magnet ramps up as the switch operator member moves into the space. That progressive increase in the influence of the switch operator member on the magnetic field makes it difficult to calibrate the point at which the interference is sufficient for the switch to be operated. By arranging the channel and the switch operator member transverse to the movement plane, the position at which the switch operator member influences the magnetic field to the extent the switch is operated can be much more closely defined. That, in turn, reduces the effect of misalignment of the switch operator member relative to the arms and makes calibration of the system more straightforward. In a third aspect of the teachings, there is provided a working machine having a magnetic switch activation system of the first above aspect and / or a magnetic switch of the second above aspect. In such a case, in the first state of the switch, at least a function of the working machine is deactivated and, in the second state of the switch, said function is activated. Preferably the function is a hydraulic function. The working machine may be one of an excavator, a mini excavator, a wheel loader, a backhoe loader, a site dumper, a tractor or a telehandler. The switch of any of the above aspects may be mounted to monitor the position of an armrest with respect to a seat or to monitor the position of a seat with respect to a working machine or to monitor the position of a side pod with respect to a floor of a cab of a working machine. BRIEF DESCRIPTION OF DRAWINGS Embodiments will now be described by way of example only with reference to the accompanying figures, in which: Figure 1 is a side elevation of a side pod of a cab of a working machine in elevated and lowered positions, Figure 2 is a side sectional view of the side pod of figure 1, Figure 3 is a side sectional view of part of the side pod of figures 1 and 2 shown to a larger scale, Figure 4 is a schematic top sectional view of the magnetic switch used in the side pod of figures 1 to 3, Figure 5 is an exploded perspective view of a magnetic switch in accordance with the teachings, Figure 6 is a side elevation of a side pod of a cab similar to that of figure 1 including the magnetic switch of figure 5, Figure 7 is a side sectional view of the side pod of figure 6 shown to a larger scale, Figure 8 is a side elevation of a working machine in the form of a backhoe loader showing the location of the side pods in that machine, and Figure 9 is a side elevation of a working machine in the form of a mini-tracked excavator showing the location of the side pods in that machine. DETAILED DESCRIPTION In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of various embodiments and the teachings. However, those skilled in the art will understand that: the present teachings may be practiced without these specific details or with known equivalents of these specific details; that the present teachings are not limited to the described embodiments; and, that the present teachings may be practiced in a variety of alternative embodiments. It will also be appreciated that well known methods, procedures, components, and systems may not have been described in detail. References to vertical and horizontal in the present disclosure should be understood to be in relation to the machine when stood on horizontal ground in a non-working condition. The term axial is generally used in relation to the longitudinal axis of the machine. The term width is generally used in relation to the longitudinal length, that is, transverse to the length. With reference to Figures 5 to 9, a magnetic switch 40 and magnetic switch activation system in accordance with the teaching is shown. In figures 5 to 7 parts of the magnetic switch 40 which correspond to parts of the known magnetic switch 10 shown in figures 1 to 4 carry the same reference numerals. In Fig.5, the magnetic switch 40 comprises first switch part 12 identical in construction to that described above with respect to figures 1 to 4, having a body 14, which is U-shaped in cross-section with two arms 16, 18 spaced apart from each other by the recess 20 of the body 14. The arm 16 contains an electrical switch 22 at the free end of the arm 16. The other arm 18 contains a permanent magnet 24, again at the free end of the arm 18. The electrical switch 22 is arranged in electrical communication with a control system of a working machine WMCS. The electrical switch and permanent magnet are not shown in figure 5 but are identical in location to that of figures 1 to 4. The first switch part 12 is mounted to the hinge base of the side pod S at 90 degrees to the orientation of the first switch part 12 in figures 1 to 4. That is to say that whilst the first switch part 12 in figures 1 to 4 is arranged so that the elongate channel runs parallel to the movement plane P-P, in the magnetic switch of figure 5, the channel runs at 90 degrees to the plane, intersecting the plane. In figure 5, the movement plane is represented approximately by two chain dotted lines, P-P and P'-P' at right angles to each other. The magnetic switch 40 further comprises a second part 42 of different construction to the second part 26 described above. The second part 42 comprises a U-shaped bracket with bracket arms 44, 46 spaced apart by a bracket mouth 48. The bracket mouth 48 is longer than the arms 16, 18 of the first part so that the bracket arms 44, 46 extend outside the longitudinal extent of the elongate channel formed by the arms at opposite end thereof. The bracket mouth 48 includes a mounting plate 50 with two apertures 52 spaced apart from each other and arranged to receive the shafts of respective mounting bolts 54. As best shown in figure 7, the second part 42 is mounted to the body of the side pod S by mounting bolts 54 and nuts 56. The bracket arms 44, 46 each have a respective hole 58, 60 at the free ends thereof. A rod 62 with a screw-threaded end portion passes through each hole 58, 60 and is secured by means of a securing nut 64. The rod 58 also passes through a hollow cylindrical jacket 66 arranged between the bracket arms. The rod 62 may be formed of a non-magnetic material, such as stainless steel. The jacket 66 is formed of a ferromagnetic material, such as iron. In the arrangement shown in figure 5, the rod 62 is an interference fit in the holes 58, 60 so that the rod 62 does not move relative to the bracket arms 44,46. The internal diameter of the bore running through the hollow cylindrical jacket 66 is larger than the outer diameter of the rod 62 so that the jacket 66 is free to rotate and to move in translation relative to the rod 62. The second part 42 is mounted to the body of the side pod in such a way that the rod 62 and jacket 66 extend parallel with the elongate channel formed between the arms 14, 18 and thus perpendicular to the movement plane P-P of the side pod S. As shown in figure 6, the first part is mounted to the hinge base of the side pod in such a way that the depth of the channel between the arms 14, 18 is oriented approximately in line with the arcuate path described by the hollow cylindrical jacket as the side pod is hinged from the elevated position (on the right in figure 6) to the lowered position (on the left in figure 6. In the elevated position, the hollow cylindrical jacket is outside the channel. That means that the magnetic field generated by the permanent magnet has an uninterrupted effect on the electrical switch so that the switch is pulled into the "off" position against the spring bias. In the lowered position, the jacket lies in the channel and the ferromagnetic material of the jacket interferes with the magnetic field of the permanent magnet. That weakens the effect of the magnetic field on the electrical switch, causing the electrical switch to move into the "on" position under the action of the spring bias. In the "off" position of the electrical switch, the working machine control system WMCS is arranged to deactivate, e.g. the hydraulic circuit powering a tool of the working machine, such as an excavator arm. In the "on" position of the electrical switch, the working machine control system WMCS is arranged to activate the hydraulic circuit. The control system may be programmed to provide a different response to the "off" and "on" positions of the electrical switch, for example to activate / deactivate an electrical system instead of a hydraulic system. Further the electrical switch 22 may be of the normally open or change-over type. Figure 7 shows, to a larger scale, the magnetic switch 40 in the lowered position of the side pod S. As mentioned above, in the lowered position, the jacket lies in the channel. Because the jacket 66 is made of ferromagnetic material and is free to move relative to the rod 62, as the jacket moves into the channel it comes under the influence of the magnetic field generated by the magnet. In this case, that has the effect of pulling the jacket towards the permanent magnet away from the electrical switch. That has two advantages. Firstly, the jacket has more of an effect on the magnetic field when closer to the magnet. Secondly, the jacket is drawn away from the electrical switch as it enters the channel, reducing the probability that the jacket will contact and potentially damage the electrical switch. As the jacket is also free to rotate relative to the rod, if the jacket contacts either arm 14, 18 as it enters the channel, either due to misalignment of the hinge due to wear or vehicle vibration, then the jacket can roll relative to the rod as it enters the channel, again reducing the likelihood of damage to either arm, magnet or electrical switch. The "floating" arrangement of the jacket on the rod allows the jacket to adopt a beneficial position within the channel under the action of the magnet. In alternative arrangements, the holes 58, 60 in the bracket arms 44, 46 may be larger in diameter than the rod 62, allowing the rod to move relative to the arms in both rotation and translation. In such a case, the jacket 66 may be as shown in figure 5 or it may be rigidly mounted to the rod 62. In a further arrangement, the rod 62 and jacket 66 may be of unitary construction and mounted for rotation and translation to the bracket arms 44, 46. In the switch of figures 5 to 7, the outer diameter of the jacket 66 is slightly smaller than the width of the elongate channel between the arms 14, 18. The diameter may be approximately 2-3mm less than the width of the channel. The outer diameter of the rod may be approximately 3-5mm less than the inner diameter of the bore through the jacket. In that way, the jacket is free to move into contact with one of the arms 14, 18 when the jacket is arranged in the channel. As can be seen most clearly in figures 6 and 7, due to the orientation of the switch parts 12, 42 relative to the movement plane P-P of the hinge of the side pod, a greater proportion of the ferromagnetic material jacket moves into the channel for the same angular movement of the side pod compared to the magnetic switch 10 of figures 1 to 4. That means that the possible range of positions of the switch 40 in which the jacket 66 interferes sufficiently with the magnetic field to cause electrical switch actuation is narrower than the range of positions of the known switch 10. That allows for more simple calibration of the system on assembly. Figures 8 and 9 illustrate, schematically, the approximate positions of the side pods S in an excavator and a tracked mini-excavator respectively. The working machine control system WMCS may comprise: control circuitry; and / or processor circuitry; and / or at least one application specific integrated circuit (ASIC); and / or at least one field programmable gate array (FPGA); and / or single or multiprocessor architectures; and / or sequential / parallel architectures; and / or at least one programmable logic controllers (PLCs); and / or at least one microprocessor; and / or at least one microcontroller; and / or a central processing unit (CPU), to perform the described methods. The controller may include an associated memory or the memory may be located locally to the controller or remotely. The memory may be a non-volatile flash memory. The one or more embodiments are described above by way of example only and it will be appreciated that the variations are possible without departing from the scope of protection afforded by the appended claims. For example, whilst the magnetic switch activation system has been described in the context of a side pod of a seat of an excavator, it will be appreciated that such activation systems are also utilised in other applications on working machines, where similar issues may arise with conventional flags - for example for seat position switches of rotating seats, presence detecting switches of seats, door switches, 5 handbrake position sensing switches, etc.

Claims

07 01 251. A magnetic switch activation system comprising a first part and a second part arranged to move with respect to each other,5 the first part comprising a body having two arms, spaced apart from each other todefine a space therebetween, one arm having a permanent magnet and the other part having an electrical switch, which has a first state and a second state, the electrical switch being operable between the first state and the second state by a variation in the magnetic field generated by the permanent magnet,10 the second part comprising a mounting and a switch operator member mounted tothe mounting,the movement of the first and second parts with respect to each other moves the switch operator member into or out of the space between the arms of the first part, the switch operator member being mounted to the mounting in such a way that the 15 switch operator member may move relative to the mounting,whereby the presence of the switch operator member in the space between the arms influences the magnetic field generated by the permanent magnet, causing the electrical switch to change from the first state to the second state, and the switch operator member is free to move relative to the mounting under the 20 influence of the magnetic field generated by the permanent magnet.

2. The magnetic switch activation system of claim 1, in which the switch is biased into the second state by a biasing element and the switch is sustained in the first state by the magnetic field generated by the permanent magnet when the switch 25 operator member is not in the space, and the switch operator member is formed,at least in part, by a ferromagnetic material, whereby positioning the switch operator member in the space interrupts or weakens the effect of the magnetic field on the switch, causing the switch to move under the action of the biasing element to the second state.

303. The magnetic switch activation system of any preceding claim, in which the operator member comprises a rod mounted to the mounting and a jacket surrounding the rod, the jacket being formed, at least in part, of ferromagnetic material.

354. The magnetic switch activation system of claim 3, in which the jacket is rigidly secured to the rod.07 01 255. The magnetic switch activation system of claim 3, in which the jacket is movable relative to the rod.

6. The magnetic switch activation system of claim 3 or 5, in which the jacket is 5 rotatable relative to the rod.

7. The magnetic switch activation system of claim 3, 5 or 6 in which the jacket is movable translationally and rotationally relative to the rod.10 8. The magnetic switch activation system of any of claims 3 to 7, in which the rod ismovably mounted to the mounting.

9. The magnetic switch activation system of claim 8, in which the rod is mounted for rotation relative to the mounting.1510. The magnetic switch activation system of claim 8 or 9, in which the rod is mounted for translation relative to the mounting.11.The magnetic switch activation system of claim 1 or 2, in which the operator 20 member comprises a unitary body formed of ferromagnetic material.12.The magnetic switch activation system of claim 11, in which the unitary body is movably mounted to the mounting.25 13. The magnetic switch activation system of claim 11 or 12, in which the unitary bodyis mounted for rotation relative to the mounting.14.The magnetic switch activation system of any preceding claim, in which the outer surface of the operator member is circular or elliptical.3015.The magnetic switch activation system of claim 3, in which the jacket is a hollow cylinder.16.The magnetic switch activation system of claim 15, in which the hollow cylinder 35 comprises a body having a circular outer periphery and a circular bore formedtherein, wherein the centre of the bore is offset from the centre of the periphery so that the jacket is arranged on the rod eccentrically.07 01 2517.The magnetic switch activation system of any preceding claim, in which the space defined between the arms is an elongate channel and in which the first and second parts move relative to each other in a movement plane, the arms and the switch operator member being arranged such that the channel and switch operator 5 member are oriented transverse to the movement plane.

18. A magnetic switch activation system as set out in any of claims 1 to 17, in which the magnetic switch is mounted to monitor the position of an arm rest with respect to a seat.1019. A magnetic switch activation system as set out in any of claims 1 to 17, in which the magnetic switch is mounted to monitor the position of a seat with respect to a working machine.15 20. A magnetic switch activation system as set out in any of claims 1 to 17, themagnetic switch being mounted to monitor the position of a side pod with respect to a floor of a cab of a working machine.

21. A working machine having a magnetic switch activation system of any of claims 1 20 to 17, in which, in the first state of the electrical switch, at least a function of theworking machine is deactivated and, in the second state of the electrical switch, said at least one function is activated, optionally wherein the function is a hydraulic function.25 22. A working machine of claim 21, in which the working machine is one of anexcavator, a mini-excavator, a wheel loader, a backhoe loader, a site dumper, a tractor or a telehandler.30

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