Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
  • H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
  • H03K17/965—Switches controlled by moving an element forming part of the switch
  • H03K17/97—Switches controlled by moving an element forming part of the switch using a magnetic movable element

Definitions

• the present invention relates to an electromechanical switch assembly o f a vehicle, particularly, the present invention relates to a contactless electromechanical switch assembly for switching of ON/OFF functions like stop lamp, cruise control, etc., more particularly, the present invention relates to sealing of a contactless electromechanical switch assembly.
• electromechanical switch assemblies are widely being used in automobiles for a long time for switching on and off any one or all the various functions like stop lamp, cruise control, electronic stability function, engine start stop function, etc.
• An existing vehicle switch sim ilar to this invention is depicted in Figure 1 and 2.
• the main problem with the prior art switches was that it becomes electrical ly non-operable or failing to meet prime function of switching on and o ff of above said various functions. Water entrapment in the switch may result in short circuiting of movi ng and fixed contact and which may even lead to burning of contacts. This results into failure o f switch or reduction in switching life. Entrapment of water is shown i n Figure 1.
• fine dust entrapment in the switch occurs through the paths indicated by arrows. This ingress of dust results in bu ilding up of a layer o f dust on the moving contact and/or fixed contact. Due to the layer of dust between contacts introduces a friction between the contacts which results in slower contact separation and leads to switch failure or reduction in switching life of the switch assembly..
• a contactless stop lamp switch assembly is depicted wherein due to water entrapment in the switch, sensor or other electronic components (which are mounted on the printed circuit board) becomes wet and un-operable which leads to switch failure or reduction in switching life of the switch assembly. Furthermore, fine dust entrapment in the switch occurs through the paths indicated by arrows results in accumulation of dust on sensor element. Due to the accumulated dust, sensor' s sensitivity gets affected resulting in reduction in switching point accuracy o f switch assembly.
• An electromechanical switch comprising a housing comprising an interior and an exterior, a casing comprising a hollow region adapted to receive the housing, a magnet sub-assembly accommodating a magnet disposed in the housing under a force of a spring, being slidably supported on one or more guiding tracks formed in the interior of the housing, an actuating shaft comprising a proximal end being disposed in the interior of the housing so as to remain in contact with the magnet sub -assembly, a distal end operatively coupled with brake pedal so that movement of the brake pedal causes actuation of the actuating shaft thereby allowing movement of the spring loaded magnet sub-assembly in longitudinal direction a sealing unit mounted on the actuating shaft and adapted to provide sealing between the casing and the interior of the housing a PCB assembly accommodated in the housing; the PCB assembly comprises one or more Hall sensors adapted to detect change in magnetic flux due to movement of the magnet sub -assembly and to provide signal indicative of activation of brake light
• Figures 1 and 2 illustrate existing contact type and contactless switch assembly
• Figures 3 and 4 illustrate a housing of an electromechanical switch assembly according to an embodiment of the present invention.
• Figures 5a-5d illustrate a sealing unit of the electromechanical switch assembly according to an embodiment of the present invention.
• Figures 6a-6d illustrate an actuating shaft of the electromechanical assembly switch according to an embodiment of the present invention.
• Figures 7a-7b illustrates the non-actuated condition electromechanical switch assembly of the present invention.
• Figure 8 illustrates the actuation of electromechanical switch assembly of the present invention.
• FIG. 9 illustrates an electromechanical switch assembly according to an alternative embodiment of the present invention.
• Figure 10 illustrates an electromechanical switch assembly according to an embodiment of the present invention.
• FIG. 11 illustrates details of connector and housing in an electromechanical switch assembly according to an embodiment of the present invention.
• the present invention provides a electromechanical switch comprising: a housing comprising an interior and an exterior;
• a casing comprising a hollow region adapted to receive the housing
• a magnet sub-assembly accommodating a magnet disposed in the housing under a force of a spring, being slidably supported on one or more guiding tracks formed in the interior of the housing
• an actuating shaft comprising:
• a proximal end being disposed in the interior of the housing so as to remain in contact with the magnet sub -assembly
• a sealing unit mounted on the actuating shaft and adapted to provide sealing between the casing and the interior of the housing;
• the PCB assembly comprises one or more Hall sensors adapted to detect change in magnetic flux due to movement of the magnet sub-assembly and to provide signal indicative of activation of brake light.
• the sealing unit comprises a flat portion and a diaphragm portion formed on the flat surface.
• the sealing unit is provided with pockets for accommodating pluralities of crushing ribs formed in the interior of the housing for securing the PCB sub assembly in a more accurate manner.
• the actuating shaft has an annular seat at the proximal end for locating the diaphragm portion of the sealing unit.
• the diaphragm portion has a first annular end located at the flat portion and a second annular end opposite to the first annular end and having an annular flange extending radially inwardly.
• the flange portion of the diaphragm is seated on the annular seat formed at the proximal end of the actuating shaft.
• the diaphragm portion has a variable thickness with thickness at the first annular end smaller than the thickness at the second annular end so that the diaphragm portion can deform easily to actuated condition and can return quickly to non-actuated condition.
• the sealing unit is positioned between the housing and the stopping face of the casing.
• the proximal end of the actuating shaft has a curved surface which remains in contact with the magnet subassembly.
• the actuating shaft has plurality of ribs extending in longitudinal direction.
• the sealing unit is made up of elastomeric material preferably rubber.
• the proximal end of the shaft comprises an annular rim and an annular seat formed on the shaft and contiguous to annular rim.
• the thickness of the flange portion is higher than the thickness of the diaphragm portion of the sealing unit.
• the housing is provided with a locating pin extending for locating the spring and a cylindrical hole may be formed on the magnet sub assembly to accommodate the spring for resiliently mounting the magnet sub assembly.
• the proximal end of the shaft comprises an annular rim and an annular seat formed on the shaft and contiguous to annular rim;
• the sealing unit comprises a diaphragm portion having a flange portion which is seated on the annular seat.
• thickness of the flange portion is higher than the thickness of the diaphragm portion of the sealing unit.
• the actuating shaft has plurality of ribs formed on the shaft extending in longitudinal direction.
• the said one or more ribs have converging section extending from distal end towards the second annular rim at the proximal end of the shaft.
• Another embodiment of the present invention further comprising a connector disposed in the housing, and mating face of the housing and the connector are substantially flat in order to restrict dust and water ingress
• a clearance between the housing and the connector is provided so that the mating face of the housing and the connector abut at butting face.
• FIGs 3 and 4 illustrate an electromechanical switch assembly (1) according to an embodiment of the present invention.
• the electromechanical switch assembly (1) of the present invention comprises a casing (2) and a housing (3) forming an encapsulation for accommodating various components of the switch assembly such as a shaft (4), a sealing unit (S), a magnet sub assembly (5), a spring (6), a PCB sub assembly (7).
• the casing (2) has a box shaped geometry, formed by side walls (8), an open end (9) and a rear end wall (10).
• One or more locking grooves (11) are provided on the side walls (8) for securing the casing (2) to the housing for forming an encapsulation.
• the housing (3) and casing (2) can be made of any suitable material preferably a thermoplastic material.
• the rear end wall (10) is incorporated with a hollow cylindrical trough (12) extending perpendicularly and outwardly from the rear end wall of the casing (2).
• the hollow cylindrical trough (12) is adapted to receive the actuating shaft (4) in the longitudinal direction.
• the term 'longitudinal direction' herein refers to a direction perpendicular to the plane of the rear end wall (10).
• the actuating shaft (4) is a rigid structure having a proximal end (13) and a distal end (14) and is adapted to move longitudinally upon actuation of brake pedal (not shown in Figures).
• a skilled artisan can envisage the construction of brake pedal and other components which transfers the actuation force from the brake pedal to the distal end (14) of the actuating shaft (4).
• the distal end (14) is adapted to pass through the hollow cylindrical trough (12) of the casing (2).
• the distal end (14) of the actuating shaft (4) emerges from an open end (12a) of the hollow cylindrical trough (12) for contacting the brake pedal.
• the proximal end (13) of the actuating shaft (4) is disposed in the interior of the housing and remains in contact with the magnet sub assembly (5).
• proximal end (13)' refers to an end of the shaft which is nearer to the magnet sub-assembly (5).
• 'distal end (14)' refers to an end of the shaft which is located far from the magnet sub-assembly (5) as compared to the proximal end (13).
• the magnet sub assembly (5) accommodates a magnet.
• the magnet sub assembly is resiliently disposed in the housing (3) and adapted to move in a longitudinal direction upon actuation by actuation shaft.
• the housing (3) is provided with plurality of guiding tracks for slidably supporting the magnet sub assembly.
• the housing (3) is provided with a locating pin (not shown in figure) extending towards the open end from the rear end wall of the housing (3) for locating the spring (6) and a cylindrical hole may be formed on the magnet sub assembly (5) to accommodate the spring (6) for resiliently mounting the magnet sub assembly (5).
• the PCB sub assembly (7) is accommodated in the housing (3) so as to be located over the magnet sub assembly.
• the housing (3) is provided with slots extending longitudinally between the open end (20) and closed end wall (21) are formed on the side walls (18, 19).
• the slots are sized to accommodate the PCB sub assembly (7).
• a plurality of apertures is provided on the closed end wall for projecting there through the terminals of the PCB sub assembly (7) for electrical connections with the driving circuit.
• the PCB sub assembly (7) comprises one or more Hall sensors or Hall element and is configured to detect magnetic flux or change in magnetic flux due to the movement of the magnet sub assembly (5) and to provide signal indicative of activation of brake light, cruise control etc.
• the electromechanical switch assembly of the present invention comprises a sealing arrangement/unit for providing sealing between the casing and interior of the housing (3).
• Figures 5(a)-(c) illustrates a sealing arrangement/unit for the electromechanical switch assembly according an embodiment of the present invention.
• the sealing unit (S) may be formed of any suitable elastomeric material such as rubber. Referring to Figures 4 and 5a-5c, the sealing unit (S) has a flat portion (SI) and a diaphragm portion (S2) formed on the flat portion (SI). The diaphragm portion
• the sealing unit (52) is a bell shaped portion.
• the flat portion (SI) of the sealing unit has a same shape as the casing inner wall.
• the diaphragm portion (S2) of the rubber sealing has a first annular end (S3) and a second annular end (S4).
• the first annular end (S3) of the diaphragm portion (S2) is located at fiat portion (SI) of the sealing unit (S).
• the second annular end (S4) of the diaphragm (S2) is located opposite to the first end
• the sealing unit (S) is provided with a plurality of rectangular pockets (S5) formed on the flat portion (S2) of the sealing unit (S) for material removal to reduce sealing weight.
• the sealing unit (S) may be mounted on the shaft (4) preferably at the proximal end (13) of the shaft (4).
• the shaft (4) may be made of any suitable plastic material.
• Figures 6(a)-(d) illustrate a construction of the shaft (4) of electromechanical switch assembly (1) according to an embodiment of the present invention.
• the proximal end (13) of the shaft has two annular rims/flanges formed on the circumference of the actuating shaft (4).
• the first annular rim/flange (13a) has a top curved surface which remains in contact with the magnet sub assembly (5).
• the second annular flange/rim (13b) is located on the shaft at spaced apart location in longitudinal direction from the first annular rim (13a).
• An annular seat (13c) is formed in-between the first annular rim (13a) and the second annular rim (13b) of the shaft (4) to accommodate the sealing unit (S).
• the flange portion (S6) of the diaphragm (S2) of the sealing unit (S) rests on the annular seat (13c) formed on the proximal end (13) of the actuating shaft (4).
• diaphragm portion (S2) of the sealing unit (S) starts to actuate, the diaphragm portion (S2) will tend to easily bend first from thinner wall starting at the base wall of the sealing unit (S) and thicker wall section will exert opposite force and try to regain its unactuated condition.
• actuation force increases to the opposition force exerted by the thicker wall, the diaphragm portion (S2) gets momentarily actuated. Restoring force will be more at the thicker wall and thus diaphragm portion (S2) will return to its initial condition quickly.
• outer profile is 0.1 to 0.2mm offset of the internal profile of the casing (2) part so that rubber diaphragm can easily rest in the casing (2).
• vertical thickness tl is kept to be 2 ⁇ 3mm so that it can be compressed around 10% of its thickness during assembly with housing with the intentional interference provided between the housing and casing part. Further, height t2 is kept to be 4-7 mm depending upon the total compressed length of the rubber diaphragm when shaft is actuated completed to switch on all the functions. Also, section A-A has been disclosed to explain the constructional detail of flexible zone of the rubber diaphragm. Diameter dl has been kept as per the formula as dl>d2+4*t5 so that adequate sliding clearance remains for the movement of moving portion of the rubber diaphragm.
• FIG. 5d it represents the wall thickness design of the flexible portion for expansion and contraction of during completion of switching stroke.
• Thickness t6 has been kept intentionally of smaller value than the thickness t7.
• the relation between t6 and t7 has been established by conducting design of experiments and it is t7>t6+0.4mm so that diaphragm has been supposed to be bent from t6 only.
• actuating shaft (4) has plurality of ribs (16) formed on the shaft (4) extending in longitudinal direction.
• the ribs (16) are formed in between the second annular rim (13b) and the distal end (14) of the shaft.
• the one or more ribs (16) have converging section extending from distal end towards the second annular rim (13b) at the proximal end (13) of the shaft.
• the converging section reduces the area available for dust and water entry in the switch assembly (1) which will reduce the possibility of dust and water entry to reach the face area of the shaft in the switch assembly (1).
• Each of the ribs (16) tapers at the proximal end (13) so as to form multiple inlets (or longitudinal grooves). In case of dust or water accumulation of any assumed quantity near the second annual rim (13b), a greater pressure head built up by the available trapezoidal volumes will expel the water and dust towards outside automatically.
• the converging ribs forms diverging channels extending from the distal end towards the second annular rim (13b) at the proximal end (13) of the shaft.
• the size of the channel i.e. the space between two ribs
• the shaft comprises two converging ribs whose cross section decreases as we move from distal end to the proximal end and two ribs extending between the distal end and the proximal end whose cross section remains constant.
• the sealing unit (S) can be positioned between casing (2) and the housing (3). As shown in figure 7(a), the sealing unit (S) is positioned between peripheral edges of side walls (18, 19) of the housing (3) and stopping face (10a) of the rear end wall of the casing (2).
• the annular seal formed on the shaft acts as a holding groove for gripping the flange portion (S6) of the elastomeric sealing unit.
• the said elastomeric sealing part is gripped in shaft holding groove or annular seal due to the intentional interference provided between the both part diametrically.
• the flat portion of the sealing unit is disposed between the peripheral edges of the housing (3) and the stopping face (10a) of the rear end wall of the casing. Thus, the said elastomeric sealing unit is guided in all around the housing periphery.
• side walls (18, 19) of the housing (3) comprise an intentional interference between the side walls (18, 19) and the sealing unit (S) guided or disposed in the casing (2).
• This construction protects the switching parts for example magnet sub assembly (5), PCB sub assembly (7) from water and dust.
• FIG 8 illustrates actuation of electromechanical switch (1) of the present invention.
• the electromechanical switch (1) is in non- actuated or no switching condition.
• the brake pedal In the non-actuated condition, the brake pedal remains in released state i.e. no force is applied on the brake pedal.
• the brake pedal is operatively coupled with the distal end (14) of the actuating shaft (4) so as to apply a force on the distal end (14) of the shaft (4) when the brake pedal is in released position, In this position, the second annular rim (13b) of the proximal end (13) of the actuation shaft (4) is not in contact with the stopping face (10a) of the rear end wall (10) of the casing (2).
• the first annular rim (13a) of the actuation shaft (4) is in point contact with the magnet sub assembly (5) due to its hemispherical geometry.
• the spring (6) which is resiliently in contact with the magnet sub assembly (5) is in compressed state in the non-actuated position of the switch (1).
• the diaphragm portion (S2) of the sealing unit (S) deforms.
• the first annular end (S3) forms a hinge about which the diaphragm (S2) deforms.
• the diaphragm portion (S2) has a variable thickness ratio with thickness at the first annular end (S3) smaller than the thickness at the second annular end (S4) so that the diaphragm portion (S2) can deform easily.
• the variable thickness ratio of the diaphragm portion (S2) also provides quicker return of the diaphragm portion (S2) when the shaft (4) moves back to the non- actuated condition.
• the sealing unit (S) and the shaft (40) may be constructed to avoid contact between the second annular rim (13b) and the stopping face (10a).
• the proximal end (130) of the shaft (40) comprises an annular rim (130a) and an annular seat (130c) formed on the shaft (40) and contiguous to annular rim (130a).
• the annular seat (130c) extends partially from the annular rim towards distal end (140) of the shaft (40).
• the flange portion (S6) of the diaphragm portion (S2) of the sealing unit (S) has been seated on the annular seat (130c).
• thickness of the flange portion (S6) is higher than the thickness of the diaphragm portion (S2) of the sealing unit (S).
• the main advantage of the present invention is that the it prevents the entry of dust and water in the housing at two locations.
• the dust and water can enter in the housing through the cylindrical trough and through the junction of the housing and casing.
• the sealing unit in the present invention prevents the entry of water and dust from these two locations.
• the sealing unit forms a seal between the inner side of the rear end wall of casing and forms a seal around the proximal end of the shaft which is received in a hollow cylindrical trough.
• the sealing unit provide dust and water protection even when the shaft is reciprocating or in motion. This protection increases the product life cycle.
• the present invention invention is much advantageous in case of vehicles which are frequently washed by water jet pressure from the bottom side of the vehicle since the possibility of water ingression inside the switch assembly is quite high during this kind of washing.
• sealing unit is constructed so that the PCB assembly can be accommodated inside the housing and the actuation of the diaphragm portion does not interfere with the other components disposed in the housing.

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• Push-Button Switches (AREA)
• Switches That Are Operated By Magnetic Or Electric Fields (AREA)

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ID=54395922

Family Applications (1)

Country Status (2)

Cited By (2)

Citations (2)

• 2015
  • 2015-09-10 WO PCT/IB2015/056922 patent/WO2016038559A1/en not_active Ceased
  • 2015-09-10 IN IN2595DE2014 patent/IN2014DE02595A/en unknown

Patent Citations (2)

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