CA1117785A - Float operated switch assembly - Google Patents
Float operated switch assemblyInfo
- Publication number
- CA1117785A CA1117785A CA000346157A CA346157A CA1117785A CA 1117785 A CA1117785 A CA 1117785A CA 000346157 A CA000346157 A CA 000346157A CA 346157 A CA346157 A CA 346157A CA 1117785 A CA1117785 A CA 1117785A
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- magnet
- magnetic member
- tertiary
- tertiary magnetic
- secondary magnet
- Prior art date
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Abstract
FLOAT OPERATED SWITCH ASSEMBLY
ABSTRACT
A float operated switch assembly has a float (4) which follows the liquid level and a primary magnet (7) which follows the movement of the float. The magnet (7) controls the angular position of a pivoted secondary bar magnet (16) on the other side of a non-magnetic wall (9) and the angular position of the magnet (16) controls by magnetic attraction the angular position of a tertiary pivoted magnet (17). The angular position of the magnet (17) controls via a coupling (20,23) a pneumatic valve (24). In each end position the magnets (16) and (17) adopt a mutually latched position. The geometry is such that this latching of the magnet (16) is unaffected by movements of the magnet (17) resulting from pneumatic surges in the valve (24). The geometry is also such that the magnet (16) receives from the magnet (17) less torque than the magnet (l?) receives from the magnet (16).
ABSTRACT
A float operated switch assembly has a float (4) which follows the liquid level and a primary magnet (7) which follows the movement of the float. The magnet (7) controls the angular position of a pivoted secondary bar magnet (16) on the other side of a non-magnetic wall (9) and the angular position of the magnet (16) controls by magnetic attraction the angular position of a tertiary pivoted magnet (17). The angular position of the magnet (17) controls via a coupling (20,23) a pneumatic valve (24). In each end position the magnets (16) and (17) adopt a mutually latched position. The geometry is such that this latching of the magnet (16) is unaffected by movements of the magnet (17) resulting from pneumatic surges in the valve (24). The geometry is also such that the magnet (16) receives from the magnet (17) less torque than the magnet (l?) receives from the magnet (16).
Description
1~17785 FLOAT OPERATED SWITCH ASSEMBLY.
The invention is concerned with a float operated switch assembly, for use with a boiler or other liquid container. The assembly has a float which follows the liquid level and is mounted with a primary 5. magnet on the wet side of the assembly so that the primary magnet moves upon movement of the float.
The primary magnet controls the movement of a secondary switch magnet by magnetic influence through a non-magnetic wall. The secondary magnet is mounted 10. on the dry side of the assembly and its movement controls the operation of a switch. Such an assembly is hereinafter referred to as of the kind described~
In a typical example the primary magnet reciprocates in a vertical non-magnetic tube at the 15. upper end of a stem proJecting upwards from the float. As is accepted in the art, the noat assembly, that is the float body and parts such as the stem and primary magnet carried by the float body, may be provided with spring assistance to the buoyancy of the 20. float body. This is particularly useful when llqu1ds o~ low specific gravity are involved as the weight of liquid displaced by the float body when fully immersed may be less than the weight of the float assembly. The secondary magnet is a bar magnet 25. pivoted about a vertical axis adjacent to the outside of the tube. The poles of the pr~mary magnet are one above the other so that when the primary magnet rises or falls with the float, the secondary magnet pivots between two end positions with a snap action 30. depending upon which pole of the primary magnet is c~oser to the secondary magnet. It is frequently desired to provide a number of switch functions each dependent upon a different level of li~uid. For this purpose a number of the secondarymagnets are pro-~5.
. .
11~'r~85 vided at different heights along the tube for cooperationwith a common primary magnet. However, the difficulty then arises of maintaining the function of one switch when the primary magnet has moved out of the sphere of influence of the respective secondary magnet. In order to hold the secondary magnet in the latched position in which it has last been pivoted by the primary magnet, it is known, as described for e~rample in our British Specifi-cation No. 688402, to provide end to end with the second-ary magnet a pivotally mounted tertiary magnet with theadaacent ends of the secondary and tertiary magnets acting in magnetic repulsion. This has the disadvantage that, upon switch over, when the secondary magnet begins to pivot to its other end position, the repulsive force between the adjacent poles of the secondary and tertiary magnet increases, giving rise to the possibility of hover of the secondary and tertiary magnets in an inter-- mediate position in which the switching function is neither in one configuration or another. A similar problem arises with the arrangement disclosed in British Patent Specification No. 976743, in which an end o~ the secondary magnet is attracted in its end positions by one or other end of a pivoted magnetic armatu.e.
A factor in any magnetically operated switch assembly is that the forces available for providing the switch function, e.g. contact faces between electrical switch contacts or operating forces for valve actuators, are limited by the magnetic influences.
In accordance with the present invention, in a 3 float operated switch assembly of the kind described, the secondary magnet is a bar magnet pivotally mounted to swing between two limited end positions under the in~lu-ence of the primary magnet, and a tertiary magnetic member is pivotally mounted to swing between two limited end positions about an axis which is substantially parallel to 111~78~
_ ~ _ the pivotal axis of the secondary magnet such that when the secondary magnet swings to one end position, one pole of the secondary magnet attracts an adjacent pole of the tertiary magnetic member to cause the tertiary magnetic member to swing to a corresponding one end position thereby latching the secondary magnet and tertiary magnetic member in their one positions, and when the secondary magnet swings to its other end position, the other pole of the secondary magnet attracts the adjacent other pole of the tertiary magnetic member to cause the tertiary magnetic member to swing to its other end position thereby latching the secondary magnet and tertiary magnetic members in their other end positions, and the swinging of the tertiary magnetic member effecting a switching function; and the arrangement being such that at least in one or other end positions of the secondary magnet and tertiary magnetic member, the torque experienced by the secondary magnet from the tertiary magnetic member is less than the torque exper-ienced by the tertiary magnetic member from the secondarymagnet.
The tertiary magnetic member may be a member of magnetizable material, such as soft iron or mu metal in which poles are induced by the adjacent poles of the secondary magnet. However, the available forces will be greater if the tertiary magnetic member is also a permanent magnet. In any case the tertiary magnetic member may by of any appropriate shape provided that ~t presents,adjacent to the poles o~ the secondary magnet, 3 poles of opposite polarity for attraction by the ad3acent poles of the secondary magnet. It may thus be of horseshoe shape but most simply is of bar magnet shape.
The tertiary magnetic member serves the purpose o~
latching the secondary magnet in one or other of its end positions, thereby providing a switch memory when the J 1117~85 _ 4 --primary magnet has moved to a position in which it no longer effectively influences the position of the second-ary magnet. The arrangement also provides an increase in the available torque for operating the switch function.
mus, in at least one or other of its end positions, the tertiary magnetic member experiences a greater torque from the secondary magnet than the secondary magnet experiences from the tertiary magnetic member, and only the torque experienced by the secondary magnet has to be overcome by the primary magnet for switch over.
me mutual magnetic torques experienced by the secondary magnet and tertiary magnetic member will depend upon the geometry, in particular the separation of the two pivotal axes, the separation of the poles of the secondary magnet and of the tertiary magnetic member,the relative positions of the poles to the pivotal axes, and the angles to and through which the secondary magnet and tertiary magnetic member are able to swing. The geometry will be such that in a position in which the torque on the tertiary magnetic member is greater than that on the secondary magnet, the line of action between their poles which are attracting one~another to determine the end position, passes closer to the pivotal axis of the secondary magnet than to that of the tertiary magnetic member. Furthermore, in order that the secondary magnet, in swinging between its end positions can capture the other end of the tertiary magnetic member, and ensure its swinging o~er as well, it is anticipated that the limited angular movement of the tertiary magnetic member will be less than that of the secondary magnet. A lock out features may be incorporated if the secondary magnet and/
or tertiary magnetic member are able to swing so far in one sense that an adiacent pair of their poles lie so close in an end position and pro~ide such attraction that the magnetic influence of the primary magnet is insufficient to rotate the secondary magnet away from this end position. This may be use~ul for example for a low level steam boiler alarm and will require a manual reset.
A further advantage of the new assembly is that, as the secondary magnet and tertiary magnetic member are arranged side by side, rather than end to end, and that magnetic attractive rather than repulsive forces are involved, initial movement of the secondary magnet away from an end position reduces rather than initially increases the mutual force with the adjacent pole of the tertiary magnetic member. The previously discussed pro-blem of hover is thus avoided.
The switch ~unction may be an electrical fw ^tion involving electrical switch contacts which are opened or closed by the swinging movement of the tertiary magnetic member. However, we envisage the application of the new assembly for the operation of a valve, such as a pneumatic valve. Such valve might be operated for example by means of a push rod, an end of which engages the tertiary magnetic member or a part which is carried and swings with the tertiary magnetic member.
When used in this way to operate a valve, such as a pneumatic ~alve, pressure surges in the pneumatic line mi~ht, transiently, be sufficient to swing the tertiary magnetic member to its opposite end position. This could lead to the possibility of unlatching of the seconda~y magnet and the possibility of the secondary magnet being relatched in its opposite end position. The switch would then have been changed over by the transient feed back from the pneumatic circuit and could have serious con-sequences.
In order to avoid this possibility, the geometry of ~he secondary magnet and tertiary magnetic members are 3~ preferably such that when the secondary magnet is latched ( 111778 -- 6 _ in an end position with the tertiary magnetic member in a corresponding position, rotation of the tertiary magnetic member to its opp~site end position does not aIfect the latching ol the secondary magnet. In pr~ct-5. ice this will normally be achieved by limiting the angular swinging movement of the tertiary magnetic member to an angle of say up to 10 either side a central position, whilst allowing the secondary magnet to swing through a larger angle of say between 20 and 10. 60, preferably 40 , either side a central position With this arrangement when the secondary magnet is in an end position, irrespecl~ive of the angular position of the tertiary ma~netic memb~r, one pole of the secondary magnet will always be nearer to the adjacent 15. pole of the tertiary magnetic member than is the other pole of the secondary magnet to the other pole of the tertiary magnetic member. In contrast, when the secondary magnet swings over between its end position~, the other pole of the secon~ary magnet will be nearer 20. to the adjacent pole of the tertiary ma~netic member, irrespective of the angular position of the tertiary magnetic ~e~ber. The terti ry magnetic member can then never be responsible for ch~nging over the secondary m~gne~ between its end positions and the stable 25. switched position is always determined by the secondary m~gnet. This feature is also useful in reducing the effects of vibration on ~he switch.
An example o~ a switch assembly constructed in accordance with the in-~enti~n is illustrated diagramm-30. atically i~. the accompanyi~g drawings, in which:-Figure 1 is a diagr2mmatic eleva-tion7 with parts bro~en away in vertical s~ction, showing ~wo switch assemblies co~nected to a liquid container;
Fi~ure 2 is a diagr~at~c plan ViW of one ~5. switch assembly; and, 111~785 Figure 3 is a perspective view of the one switch assembly.
As shown in Figure 1, a float 4 is buoyant in a liquid 5 within a container 6 and carries a vertically 5. polarized bar magnet 7 at the top of a stem 8. The magnet 7 moves vertically, upon movement of the float 4, within a non-magnetic, e.g. stainless steel or glass, tube 9 to the outer wall of which are attached two switch units 10, all within a housing 11 having a lower 10. wall 12 which seals the container 6. The wet side of the assembly is the part within the container 6 and within the tube 9 and the dry side the part within the housing 11 outside the tube 9.
As shown in Figures 2 and 3, each switch 15. assembly is shown as having a mounting plate 13 on which are pivotally mounted about vertical axes, and between plates 14 and 15, a secondary switch bar magnet 16 and a tertiary bar magnet 17. me angular movement of the secondary magnet 16 is limited by a pair of 20. abutments 18 mounted on the plate 14, and that of the tertiary m~gnet 17 by a pair of similar although smaller abutments 19. Angular movement of the tertiary magnet 17 is followed by a rocking member 20 which is pivotally mounted about a vertical axis 21 and has at 25. one end a roller 22 which bears against the magnet 17.
At its other end the rocking member 20 is coupled to the end of an operating rod 23 of a pneumatic valve 24.
In practice air lines to and from the pneumatic valves 24 will pass out of the housing 11 through conventional 30. hoses.
As will ~e apparent from Figure 2, the tertiary magnet 17 is free to rotate through an angle a, of approxi~ately 20 whereas the secondary magnet 16 is free to rock through a larger angle ~ , of approx-35- imately 80. The adJacent poles of the two magnets 16 1~1778 and 17 are of opposite polarity, thus the poles Pl and P2 shown in Figure 2 will be one a south pole and the other a north pole. It follows that there are two stable positions, one shown in full lines and one shown 5. in chain dotted lines. In each of these positions, it will be apparent that the line of force LF between the two closer poles represents the direction of an e~ual attraction on the poles Pl and P2 of the two magnets.
However, owing to the geometry of the siz~sof the two 10. magnets and their angular freedom of movement, the line of force LF is inclined to the line joining the pivotal axes of the two magnets. Consequently the perpendicular distance Y between the pivotal axis of the magr.et 1~ and the line LF is less than the perpendi-15. cular distance X between the pivotal axis of the magnet17 and the line LF Consequently the torque experienced by the magnet 17 is greater than that experienced by the magnet 16. Although other magnetic interactions exist, owing to the inverse square law only the 20. magnetic attraction between the poles pl and p2 is significant in the full line position of the magnets.
As one or other of the north and south poles of the magnet 7 moves up or down the tube 9 closely adJacent to the secondary magnet 16, the magnet 16 is urged to 25. rotate in the same sense by the mutual attraction and repulsion between its repsective poles and the adjacent pole of the magnet 7 so that it adopts one of its end positions. In either of the end positions the pole of the magnet 16 closer to the magnet 17 attracts the 30. adjacent end of the magnet 17 and both magnets are held in their illustrated full or chain dotted line positions by their mutual attraction. This is a stable latched con~iguration which is maintained until the other pole of the magnet 7 moves into proximity with the secondary 35. magnet 16. This causes the magnet 16, and hence the g magnet 17 to change over to their other mutually latched end p~sitions. As has been explained, in each of the end positions of the two magnets, the torque experienced by the magnet 16 is less than that 5. experienced by the magnet 17 so that the magnet 7 can change over the switch by providing a smaller torque on the magnet 16, to unlatch the magnet 16 from the magnet 17,than is available from the magnet 17 to operate the pneumatic switch 24.
10. It is assumed that the operating rod 23 is resiliently urged out of the pneumatic switch 24 so that the roller 22 is maintained in engagement with the tertiary magnet 1?. Rotation of the magnet 17 between its two end positions thus rGcks the member 20 between 15. its two end positions and causes the rod 23 to recipro-cate between two end positions, in each of which a different pneumatic configuration is provided, for example by means of a spool directly connected to the rod 23, within the switch 24.
20. It is possible that transient fluctuations in the pneumatic circuit connected to the switch 24 may cause transient movements of the rod 23 outwardly of the switch 24 when the tertiary magnet 17 is in its full line position. m is could momentarily o~ercome 25. the magnetic attraction be~ween the poles P1 and P2 andforce the magnet 17 to rotate clockwise as shown in Fi~ure 2 to its other end position. However the geo-metry of the magnets 16 and 17, and particularly the greater angular movement of the magnet 16 than that of 30. the magnet 17, pre~ents this movement of the magnet 17 ~rom affecting the latching between the two magnets.
Consequently the secondary magnet is maintained by the proxim}ty of the pole Pl in its illustrated full line position and when the pressure in the pneumatic circuit 35. has equalised again, the tertiary magnet 17 will readopt its full line position.
The particular geometric arrangement of the primary, secondary and tertiary magnets 7, 16 and 17, as illustrated, optimizes the transmission of energy from the float to the rocking member 20 and hence to the switch 24. The torque provided by the tertiary magnet 17 over its smaller angular movement compared to that of the secondary magnet 16 gives an output of work which is a large proportion of the energy absorbed from the movement of the primary magnet 7 working, prior to switch changeover, against the repulsion from the adjacent pole of the secondary magnet 16.
The invention is concerned with a float operated switch assembly, for use with a boiler or other liquid container. The assembly has a float which follows the liquid level and is mounted with a primary 5. magnet on the wet side of the assembly so that the primary magnet moves upon movement of the float.
The primary magnet controls the movement of a secondary switch magnet by magnetic influence through a non-magnetic wall. The secondary magnet is mounted 10. on the dry side of the assembly and its movement controls the operation of a switch. Such an assembly is hereinafter referred to as of the kind described~
In a typical example the primary magnet reciprocates in a vertical non-magnetic tube at the 15. upper end of a stem proJecting upwards from the float. As is accepted in the art, the noat assembly, that is the float body and parts such as the stem and primary magnet carried by the float body, may be provided with spring assistance to the buoyancy of the 20. float body. This is particularly useful when llqu1ds o~ low specific gravity are involved as the weight of liquid displaced by the float body when fully immersed may be less than the weight of the float assembly. The secondary magnet is a bar magnet 25. pivoted about a vertical axis adjacent to the outside of the tube. The poles of the pr~mary magnet are one above the other so that when the primary magnet rises or falls with the float, the secondary magnet pivots between two end positions with a snap action 30. depending upon which pole of the primary magnet is c~oser to the secondary magnet. It is frequently desired to provide a number of switch functions each dependent upon a different level of li~uid. For this purpose a number of the secondarymagnets are pro-~5.
. .
11~'r~85 vided at different heights along the tube for cooperationwith a common primary magnet. However, the difficulty then arises of maintaining the function of one switch when the primary magnet has moved out of the sphere of influence of the respective secondary magnet. In order to hold the secondary magnet in the latched position in which it has last been pivoted by the primary magnet, it is known, as described for e~rample in our British Specifi-cation No. 688402, to provide end to end with the second-ary magnet a pivotally mounted tertiary magnet with theadaacent ends of the secondary and tertiary magnets acting in magnetic repulsion. This has the disadvantage that, upon switch over, when the secondary magnet begins to pivot to its other end position, the repulsive force between the adjacent poles of the secondary and tertiary magnet increases, giving rise to the possibility of hover of the secondary and tertiary magnets in an inter-- mediate position in which the switching function is neither in one configuration or another. A similar problem arises with the arrangement disclosed in British Patent Specification No. 976743, in which an end o~ the secondary magnet is attracted in its end positions by one or other end of a pivoted magnetic armatu.e.
A factor in any magnetically operated switch assembly is that the forces available for providing the switch function, e.g. contact faces between electrical switch contacts or operating forces for valve actuators, are limited by the magnetic influences.
In accordance with the present invention, in a 3 float operated switch assembly of the kind described, the secondary magnet is a bar magnet pivotally mounted to swing between two limited end positions under the in~lu-ence of the primary magnet, and a tertiary magnetic member is pivotally mounted to swing between two limited end positions about an axis which is substantially parallel to 111~78~
_ ~ _ the pivotal axis of the secondary magnet such that when the secondary magnet swings to one end position, one pole of the secondary magnet attracts an adjacent pole of the tertiary magnetic member to cause the tertiary magnetic member to swing to a corresponding one end position thereby latching the secondary magnet and tertiary magnetic member in their one positions, and when the secondary magnet swings to its other end position, the other pole of the secondary magnet attracts the adjacent other pole of the tertiary magnetic member to cause the tertiary magnetic member to swing to its other end position thereby latching the secondary magnet and tertiary magnetic members in their other end positions, and the swinging of the tertiary magnetic member effecting a switching function; and the arrangement being such that at least in one or other end positions of the secondary magnet and tertiary magnetic member, the torque experienced by the secondary magnet from the tertiary magnetic member is less than the torque exper-ienced by the tertiary magnetic member from the secondarymagnet.
The tertiary magnetic member may be a member of magnetizable material, such as soft iron or mu metal in which poles are induced by the adjacent poles of the secondary magnet. However, the available forces will be greater if the tertiary magnetic member is also a permanent magnet. In any case the tertiary magnetic member may by of any appropriate shape provided that ~t presents,adjacent to the poles o~ the secondary magnet, 3 poles of opposite polarity for attraction by the ad3acent poles of the secondary magnet. It may thus be of horseshoe shape but most simply is of bar magnet shape.
The tertiary magnetic member serves the purpose o~
latching the secondary magnet in one or other of its end positions, thereby providing a switch memory when the J 1117~85 _ 4 --primary magnet has moved to a position in which it no longer effectively influences the position of the second-ary magnet. The arrangement also provides an increase in the available torque for operating the switch function.
mus, in at least one or other of its end positions, the tertiary magnetic member experiences a greater torque from the secondary magnet than the secondary magnet experiences from the tertiary magnetic member, and only the torque experienced by the secondary magnet has to be overcome by the primary magnet for switch over.
me mutual magnetic torques experienced by the secondary magnet and tertiary magnetic member will depend upon the geometry, in particular the separation of the two pivotal axes, the separation of the poles of the secondary magnet and of the tertiary magnetic member,the relative positions of the poles to the pivotal axes, and the angles to and through which the secondary magnet and tertiary magnetic member are able to swing. The geometry will be such that in a position in which the torque on the tertiary magnetic member is greater than that on the secondary magnet, the line of action between their poles which are attracting one~another to determine the end position, passes closer to the pivotal axis of the secondary magnet than to that of the tertiary magnetic member. Furthermore, in order that the secondary magnet, in swinging between its end positions can capture the other end of the tertiary magnetic member, and ensure its swinging o~er as well, it is anticipated that the limited angular movement of the tertiary magnetic member will be less than that of the secondary magnet. A lock out features may be incorporated if the secondary magnet and/
or tertiary magnetic member are able to swing so far in one sense that an adiacent pair of their poles lie so close in an end position and pro~ide such attraction that the magnetic influence of the primary magnet is insufficient to rotate the secondary magnet away from this end position. This may be use~ul for example for a low level steam boiler alarm and will require a manual reset.
A further advantage of the new assembly is that, as the secondary magnet and tertiary magnetic member are arranged side by side, rather than end to end, and that magnetic attractive rather than repulsive forces are involved, initial movement of the secondary magnet away from an end position reduces rather than initially increases the mutual force with the adjacent pole of the tertiary magnetic member. The previously discussed pro-blem of hover is thus avoided.
The switch ~unction may be an electrical fw ^tion involving electrical switch contacts which are opened or closed by the swinging movement of the tertiary magnetic member. However, we envisage the application of the new assembly for the operation of a valve, such as a pneumatic valve. Such valve might be operated for example by means of a push rod, an end of which engages the tertiary magnetic member or a part which is carried and swings with the tertiary magnetic member.
When used in this way to operate a valve, such as a pneumatic ~alve, pressure surges in the pneumatic line mi~ht, transiently, be sufficient to swing the tertiary magnetic member to its opposite end position. This could lead to the possibility of unlatching of the seconda~y magnet and the possibility of the secondary magnet being relatched in its opposite end position. The switch would then have been changed over by the transient feed back from the pneumatic circuit and could have serious con-sequences.
In order to avoid this possibility, the geometry of ~he secondary magnet and tertiary magnetic members are 3~ preferably such that when the secondary magnet is latched ( 111778 -- 6 _ in an end position with the tertiary magnetic member in a corresponding position, rotation of the tertiary magnetic member to its opp~site end position does not aIfect the latching ol the secondary magnet. In pr~ct-5. ice this will normally be achieved by limiting the angular swinging movement of the tertiary magnetic member to an angle of say up to 10 either side a central position, whilst allowing the secondary magnet to swing through a larger angle of say between 20 and 10. 60, preferably 40 , either side a central position With this arrangement when the secondary magnet is in an end position, irrespecl~ive of the angular position of the tertiary ma~netic memb~r, one pole of the secondary magnet will always be nearer to the adjacent 15. pole of the tertiary magnetic member than is the other pole of the secondary magnet to the other pole of the tertiary magnetic member. In contrast, when the secondary magnet swings over between its end position~, the other pole of the secon~ary magnet will be nearer 20. to the adjacent pole of the tertiary ma~netic member, irrespective of the angular position of the tertiary magnetic ~e~ber. The terti ry magnetic member can then never be responsible for ch~nging over the secondary m~gne~ between its end positions and the stable 25. switched position is always determined by the secondary m~gnet. This feature is also useful in reducing the effects of vibration on ~he switch.
An example o~ a switch assembly constructed in accordance with the in-~enti~n is illustrated diagramm-30. atically i~. the accompanyi~g drawings, in which:-Figure 1 is a diagr2mmatic eleva-tion7 with parts bro~en away in vertical s~ction, showing ~wo switch assemblies co~nected to a liquid container;
Fi~ure 2 is a diagr~at~c plan ViW of one ~5. switch assembly; and, 111~785 Figure 3 is a perspective view of the one switch assembly.
As shown in Figure 1, a float 4 is buoyant in a liquid 5 within a container 6 and carries a vertically 5. polarized bar magnet 7 at the top of a stem 8. The magnet 7 moves vertically, upon movement of the float 4, within a non-magnetic, e.g. stainless steel or glass, tube 9 to the outer wall of which are attached two switch units 10, all within a housing 11 having a lower 10. wall 12 which seals the container 6. The wet side of the assembly is the part within the container 6 and within the tube 9 and the dry side the part within the housing 11 outside the tube 9.
As shown in Figures 2 and 3, each switch 15. assembly is shown as having a mounting plate 13 on which are pivotally mounted about vertical axes, and between plates 14 and 15, a secondary switch bar magnet 16 and a tertiary bar magnet 17. me angular movement of the secondary magnet 16 is limited by a pair of 20. abutments 18 mounted on the plate 14, and that of the tertiary m~gnet 17 by a pair of similar although smaller abutments 19. Angular movement of the tertiary magnet 17 is followed by a rocking member 20 which is pivotally mounted about a vertical axis 21 and has at 25. one end a roller 22 which bears against the magnet 17.
At its other end the rocking member 20 is coupled to the end of an operating rod 23 of a pneumatic valve 24.
In practice air lines to and from the pneumatic valves 24 will pass out of the housing 11 through conventional 30. hoses.
As will ~e apparent from Figure 2, the tertiary magnet 17 is free to rotate through an angle a, of approxi~ately 20 whereas the secondary magnet 16 is free to rock through a larger angle ~ , of approx-35- imately 80. The adJacent poles of the two magnets 16 1~1778 and 17 are of opposite polarity, thus the poles Pl and P2 shown in Figure 2 will be one a south pole and the other a north pole. It follows that there are two stable positions, one shown in full lines and one shown 5. in chain dotted lines. In each of these positions, it will be apparent that the line of force LF between the two closer poles represents the direction of an e~ual attraction on the poles Pl and P2 of the two magnets.
However, owing to the geometry of the siz~sof the two 10. magnets and their angular freedom of movement, the line of force LF is inclined to the line joining the pivotal axes of the two magnets. Consequently the perpendicular distance Y between the pivotal axis of the magr.et 1~ and the line LF is less than the perpendi-15. cular distance X between the pivotal axis of the magnet17 and the line LF Consequently the torque experienced by the magnet 17 is greater than that experienced by the magnet 16. Although other magnetic interactions exist, owing to the inverse square law only the 20. magnetic attraction between the poles pl and p2 is significant in the full line position of the magnets.
As one or other of the north and south poles of the magnet 7 moves up or down the tube 9 closely adJacent to the secondary magnet 16, the magnet 16 is urged to 25. rotate in the same sense by the mutual attraction and repulsion between its repsective poles and the adjacent pole of the magnet 7 so that it adopts one of its end positions. In either of the end positions the pole of the magnet 16 closer to the magnet 17 attracts the 30. adjacent end of the magnet 17 and both magnets are held in their illustrated full or chain dotted line positions by their mutual attraction. This is a stable latched con~iguration which is maintained until the other pole of the magnet 7 moves into proximity with the secondary 35. magnet 16. This causes the magnet 16, and hence the g magnet 17 to change over to their other mutually latched end p~sitions. As has been explained, in each of the end positions of the two magnets, the torque experienced by the magnet 16 is less than that 5. experienced by the magnet 17 so that the magnet 7 can change over the switch by providing a smaller torque on the magnet 16, to unlatch the magnet 16 from the magnet 17,than is available from the magnet 17 to operate the pneumatic switch 24.
10. It is assumed that the operating rod 23 is resiliently urged out of the pneumatic switch 24 so that the roller 22 is maintained in engagement with the tertiary magnet 1?. Rotation of the magnet 17 between its two end positions thus rGcks the member 20 between 15. its two end positions and causes the rod 23 to recipro-cate between two end positions, in each of which a different pneumatic configuration is provided, for example by means of a spool directly connected to the rod 23, within the switch 24.
20. It is possible that transient fluctuations in the pneumatic circuit connected to the switch 24 may cause transient movements of the rod 23 outwardly of the switch 24 when the tertiary magnet 17 is in its full line position. m is could momentarily o~ercome 25. the magnetic attraction be~ween the poles P1 and P2 andforce the magnet 17 to rotate clockwise as shown in Fi~ure 2 to its other end position. However the geo-metry of the magnets 16 and 17, and particularly the greater angular movement of the magnet 16 than that of 30. the magnet 17, pre~ents this movement of the magnet 17 ~rom affecting the latching between the two magnets.
Consequently the secondary magnet is maintained by the proxim}ty of the pole Pl in its illustrated full line position and when the pressure in the pneumatic circuit 35. has equalised again, the tertiary magnet 17 will readopt its full line position.
The particular geometric arrangement of the primary, secondary and tertiary magnets 7, 16 and 17, as illustrated, optimizes the transmission of energy from the float to the rocking member 20 and hence to the switch 24. The torque provided by the tertiary magnet 17 over its smaller angular movement compared to that of the secondary magnet 16 gives an output of work which is a large proportion of the energy absorbed from the movement of the primary magnet 7 working, prior to switch changeover, against the repulsion from the adjacent pole of the secondary magnet 16.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A float operated switch assembly having a float which is mounted with a primary magnet on a wet side of said assembly so that said primary magnet moves upon movement of said float, said primary magnet controlling the movement of a secondary switch magnet by magnetic influence through a non-magnetic wall, and said secondary magnet being mounted on a dry side of said assembly and its movement controlling the operation of a switch, wherein said secondary magnet is a bar magnet pivotally mounted to swing between first and second limited end positions under the influence of said primary magnet, and a tertiary magnetic member is pivotally mounted to swing between first and second limited end positions about an axis which is substant-ially parallel to the pivotal axis of said secondary magnet such that when said secondary magnet swings to its said first end position, one pole of said secondary magnet attracts an adjacent pole of said tertiary magnetic member to cause said tertiary magnetic member to swing to its said first end position thereby latch-ing said secondary magnet and tertiary magnetic member in their said first end positions, and when said secondary magnet swings to its said second end position, the other pole of said secondary magnet attracts the adjacent other pole of said tertiary magnetic member to cause said tertiary magnetic member to swing to its said second end position thereby latching said secondary magnet and tertiary magnetic members in their second end positions, and the swinging of said tertiary magnetic member effecting a switching function; and the arrangement being such that at least in one of said first and second end positions of said secondary magnet and tertiary magnetic member, the torque experienced by said secondary magnet from said tertiary magnetic member is less than the torque experienced by said tertiary magnetic member from said secondary magnet.
2. An assembly according to claim 1, wherein said tertiary magnetic member is a permanent magnet.
3. An assembly according to claim 1, wherein said tertiary magnetic member is of bar magnet shape.
4. An assembly according to claim 1, wherein angular movement of said tertiary magnetic member between its first and second limited end positions is less than that of said secondary magnet.
5. An assembly according to claim 1, wherein the geometry of said secondary magnet and tertiary magnetic members are such that when said secondary magnet is latched in one of its said first and second end positions with said tertiary magnetic member in a corresponding position, rotation of said tertiary magnetic member to the other of its said end positions does not affect the latching of said secondary magnet.
6. An assembly according to claim 1 or claim 5, wherein said switching function involves the operation of a pneumatic valve, an operating member of which is coupled to said tertiary magnetic member.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7908012 | 1979-03-07 | ||
| GB7908012 | 1979-03-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1117785A true CA1117785A (en) | 1982-02-09 |
Family
ID=10503683
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000346157A Expired CA1117785A (en) | 1979-03-07 | 1980-02-21 | Float operated switch assembly |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1117785A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105297355A (en) * | 2015-10-12 | 2016-02-03 | 安徽安泽电工股份有限公司 | Washing machine heater with flow diversion heating plates |
| US10161777B2 (en) | 2016-06-14 | 2018-12-25 | Badger Meter, Inc. | Water meter with magnetically driven flow restriction valve |
-
1980
- 1980-02-21 CA CA000346157A patent/CA1117785A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105297355A (en) * | 2015-10-12 | 2016-02-03 | 安徽安泽电工股份有限公司 | Washing machine heater with flow diversion heating plates |
| US10161777B2 (en) | 2016-06-14 | 2018-12-25 | Badger Meter, Inc. | Water meter with magnetically driven flow restriction valve |
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| Date | Code | Title | Description |
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| MKEX | Expiry |