Patent Publication Number: US-2021188609-A1

Title: Proximity sensor assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application Ser. No. 61,762,502 filed May 7, 2018, the disclosure of which is hereby incorporated in its entirety by reference herein. 
    
    
     TECHNICAL FIELD 
     The invention relates to a proximity sensor assembly, a mobile work platform including such a sensor assembly, and a vehicle including such a sensor assembly. 
     BACKGROUND 
     Examples of safety devices for mobile work platforms are disclosed in U.S. Patent Application Publication Number 2013/0233645 A1 and U.S. Patent Application Publication Number 2015/0008073 A1. 
     SUMMARY 
     A proximity sensor assembly according to the disclosure may include a detection member, a switch, and a movable mounting arrangement associated with the detection member and the switch. The movable mounting arrangement may include a biasing characteristic for urging the detection member toward a home position after the detection member has been displaced from the home position, and a dampening characteristic for dampening movement of the detection member. Furthermore, the switch is actuatable when the detection member is displaced from the home position. 
     According to at least one embodiment of the disclosure, a mobile work platform assembly is provided for use with a movable support assembly that is configured to move the mobile work platform assembly. The mobile work platform assembly may include a work platform sized to receive an operator, a control arrangement associated with the work platform for controlling movement of the work platform, and a proximity sensor assembly associated with the work platform. The proximity sensor assembly may include a detection member, an actuatable switch, and a movable mounting arrangement associated with the detection member and the switch. The movable mounting arrangement may include a biasing characteristic for urging the detection member toward a home position after the detection member has been displaced from the home position and a dampening characteristic to dampen movement of the detection member. Furthermore, when the detection member is displaced from the home position, the switch is actuatable to inhibit operation of the control arrangement. 
     A vehicle according to the disclosure may include a vehicle body, a support assembly connected to the vehicle body, and a mobile work platform assembly supported by the support assembly so that the work platform assembly is movable with respect to the vehicle body. The work platform assembly may include a work platform sized to receive an operator, a control arrangement associated with the work platform for controlling movement of the work platform, and a proximity sensor assembly associated with the work platform. The proximity sensor assembly may include a detection member, an actuatable switch, and a movable mounting arrangement associated with the detection member and the switch. The mounting arrangement may include a biasing characteristic for urging the detection member toward a home position after the detection member has been displaced from the home position, and a dampening characteristic for dampening movement of the detection member. When the detection member is displaced from the home position, the switch is actuatable to inhibit operation of the control arrangement. 
     While exemplary embodiments are illustrated and disclosed, such disclosure should not be construed to limit the claims. It is anticipated that various modifications and alternative designs may be made without departing from the scope of the disclosure. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a vehicle including a mobile work platform assembly according to the present disclosure, and multiple proximity sensor assemblies attached to the work platform assembly; 
       FIG. 2  is a fragmentary cross-sectional view of one of the proximity sensor assemblies with a detection member shown in a home position; 
       FIG. 3  is a fragmentary cross-sectional view of the proximity sensor assembly of  FIG. 2  with the detection member shown in a displaced position, with a cover of the proximity sensor assembly removed; 
       FIG. 4  is an exploded perspective view of the proximity sensor assembly shown in  FIG. 2 ; 
       FIG. 5  is an enlarged perspective view of a base of the proximity sensor assembly including a circular insert for facilitating mounting of the proximity sensor assembly on a round rail or other feature of the work platform assembly; 
       FIG. 6  is an enlarged perspective view of the base of the proximity sensor assembly including a flat-sided insert for facilitating mounting of the proximity sensor assembly on a a rail or other feature having a rectangular cross-section; 
       FIG. 7  is an enlarged exploded fragmentary perspective view of a portion of the proximity sensor assembly showing the detection member and a detection member holder that receives the detection member, wherein the detection member and the detection member holder include mounting features for orienting the detection member with respect to the detection member holder; 
       FIG. 8  is a perspective view or a second embodiment of a proximity sensor assembly according to the disclosure; and 
       FIG. 9  is a fragmentary cross-sectional view of the proximity sensor assembly of  FIG. 8 . 
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary, and that various and alternative forms may be employed. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art. 
       FIG. 1  shows a vehicle  10 , according to the present disclosure, including a vehicle body  12 , a support assembly  14  connected to the vehicle body  12 , and a mobile work platform assembly  16  supported by the support assembly  14  so that the work platform assembly  16  is provided with an movable with respect to the vehicle body  12 . The work platform assembly  16  is provided with an obstruction proximity sensing system  18 , according to the disclosure, for sensing potential obstructions to the work platform assembly  16  during operation of the work platform assembly  16 , as explained below in detail. 
     The vehicle  10  may be any suitable vehicle, such as a boom lift, scissor lift, or any other suitable aerial lift. Furthermore, the vehicle body  12  may be supported on any suitable support members  20 , such as one or more tires, tracks, outriggers, etc. In the embodiment shown in  FIG. 1 , the vehicle body  12  is supported on multiple tires, two or more of which may be steerable. 
     The support assembly  14  likewise may be any suitable support assembly, such as a lift arm, vertical mast, articulating boom assembly, telescopic boom assembly, scissor lift assembly, etc. In the embodiment shown in  FIG. 1 , the support assembly  14  comprises a scissor lift  22  having multiple sections  24  that are movable relative to each other to move the work platform assembly  16  between a lowered position and a raised position (not shown). 
     The work platform assembly  16  includes a base or work platform  26  and a control arrangement  28  associated with the platform  26  for controlling movement of the platform  26 . In addition, the work platform assembly  16  includes the above-mentioned obstruction proximity sensing system  18 , which is also associated with the platform  26  and the control arrangement  28 . 
     The platform  26  of the work platform assembly  16  is sized to receive an operator thereon. A railing assembly or frame assembly  30  is provided on the platform  26 , and the frame assembly  30  includes one or more guard rails that cooperate to contain the operator within the frame assembly  30 . In the embodiment shown in  FIG. 1 , the frame assembly  30  includes multiple toe boards  32 , middle rails  34  and top rails  36 . The frame assembly  30  further includes a movable (e.g., pivotable) door  38  to allow or permit operator ingress to, and egress from, the work platform assembly  16 . 
     The control arrangement  28  may include any suitable controls for controlling operation of the platform  26  (e.g., movement of the platform  26 ). For example, the control arrangement  28  may include a control unit  40  (e.g., electronic control unit, control box or control panel) having one or more controls, such as buttons, switches, levers (e.g., joysticks), etc., for inputting control commands. 
     The above-mentioned obstruction proximity sensing system  18  is associated with the platform  26  and the control arrangement  28 , and includes one or more proximity sensor assemblies  42  that are configured to sense presence of an obstruction when the work platform assembly  16  is moved. The one or more proximity sensor assemblies  42  may also be electrically connected to the control arrangement  28 , e.g., to the control unit  40 . Details of one of the proximity sensor assemblies  42  will now be described with reference to  FIGS. 2-4 , with the understanding that any other proximity sensor assemblies  42  may have the same or similar configuration. 
     The proximity sensor assembly  42  shown in  FIGS. 2-4  includes a base  44 , such as an assembly mount, that is mountable onto a rail (e.g., a top rail  36 ) or other feature of the work platform assembly  16 . In the illustrated embodiment, the base  44  includes a first section or portion  45  that is attachable to the work platform assembly  16 , and a second section or portion  46  that is attachable to the first portion  45  with one or more fasteners, such as bolts or screws. 
     Referring to  FIGS. 5 and 6 , the first portion  45  may include a main body  47 , an insert  48  that is receivable in an opening or recess formed in the main body  47  for facilitating installation of the first portion  45  on a rail (e.g, top rail  36  of the frame assembly  30 ) or other feature of the work platform assembly  16 , and a retainer  49 , such as an end plate, that is attachable to the main body  47  with any suitable fasteners (e.g., bolts or screws) to help retain the insert  48  in the recess of the main body  47  when the first portion  45  is mounted on the rail or other feature of the work platform assembly  16 . In the embodiment shown in  FIG. 5 , the first portion  45  includes a cylindrical insert  48   a  having a cursed inner surface, such as a circular inner surface viewed in cross-section, that is configured to mate with a round rail or other feature of the work platform assembly  16 . In the embodiment shown in  FIG. 6 , the first portion  45  includes an insert  48   b  having flat inner sides or surfaces, such as a C-shaped insert having three flat inner sides or surfaces, that are configured to mate with a rail or other feature of the work platform assembly  16  having a rectangular cross-section (e.g., square cross-section). Furthermore, each insert  48   a,    48   b  may be formed as a single piece or multiple pieces, and each piece may be separately attachable to the main body  47 , such as with any suitable fasteners (e.g., bolts or screws). 
     Returning to  FIGS. 2-4 , the proximity sensor assembly  42  further includes a switch  50 , such as a limit switch, cut-off switch, etc., received in the base  44 ; a detection member, such as a wand assembly  52 , for sensing obstructions; and a movable mounting arrangement  54  associated with (e.g., connected to) the base  44  and the switch  50 . In the illustrated embodiment, the mounting arrangement  54  connects the wand assembly  52  to the base  44  and the switch  50  so that the wand assembly  52  is movable with respect to the base  44 . Furthermore, as explained below in further detail, the mounting arrangement  54  includes a biasing characteristic for urging the wand assembly  52  toward a home position, and a damping characteristic for dampening movement of the wand assembly  52 . 
     Referring to  FIGS. 2 and 3 , the switch  50  (e.g., limit switch) may include a switch body  56  that houses a set of contacts  57   a  and  57   b,  and an actuator, such as a spring-loaded button  58 , that is movable with respect to the switch body  56  and mechanically linked to one or both of the contacts  57   a  and  57   b  (the switch  50  is not shown in cross-section in  FIGS. 2 and 3 ). In the illustrated embodiment, the button  58  is linked to the upper contact  57   b  and movable with the upper contact  57   b.  When the button  58  is moved away from the switch body due to force of the associated spring (not shown), the switch  50  is actuated so that the contacts  57   a  and  57   b  are separated from each other. 
     Referring to  FIG. 4 , the wand assembly  52  may include a main body portion  60  and an angled head portion  62  attached to the main body portion  60 . The wand assembly  52  may further include a rotatable member, such as a wheel  64 , rotatably attached to the head portion  62 . With such a configuration, the wand assembly  52  may make contact with an obstruction prior to the platform  26  of the work platform assembly  16  being laterally aligned with the obstruction. Furthermore, the wheel  64  or other rotatable member may facilitate smooth contact with the obstruction and inhibit undesired bending of the main body portion  60  of the wand assembly  52 . 
     Referring to  FIGS. 2-4 , the mounting arrangement  54  may include a detection member holder or wand assembly holder  66  connected to the wand assembly  52  in any suitable manner (e.g., with a set screw), a mounting member or mount  68  connected to the switch  50  in any suitable manner (e.g., threadingly connected together), and a biasing member, such as a cylindrical spring member  70 , associated with the wand assembly holder  66  and the mount  68  and that provides the biasing characteristic. The spring member  70  is also configured to allow the wand assembly holder  66  and the wand assembly  52  to move with respect to the mount  68 . In the illustrated embodiment, the spring member  70  is connected to the wand assembly holder  66  and the mount  68  in any suitable manner. For example, the wand assembly holder  66  may include a threaded portion  72 , the mount  68  may include a threaded portion  74 , and the spring member  70  may be a coil, extension spring that is connected to the threaded portions  72  and  74 , such as by rotating the spring member  70  and/or the threaded portions  72  and  74  relative to each other. Furthermore, the mount  68  may be formed integrally with at least a portion of the base  44 . 
     The mounting arrangement  54  may further include an engaging member such as a plunger  76  that extends into the mount  68  for engaging the button  58  of the switch  50 , and a spacer member or intermediate member  78  positioned between the wand assembly holder  66  and the mount  68 . In addition, the mounting arrangement  54  includes one or more damping members, such as magnets  80 , that provide the damping characteristic for damping movement of the wand assembly  52 . 
     In the illustrated embodiment, the mounting arrangement  54  includes first, second, third and fourth magnets  80   a,    80   b,    80   c  and  80   d,  respectively. The first magnet  80   a  is attached to the wand assembly holder  66  with a first fastener  82   a,  such as, a screw. The second magnet  80   b  is attached to the intermediate member  78  with a second fastener  82   b,  such as a screw. The third magnet  80   c  is attached to the intermediate member  78  with a third fastener  82   c,  such as a screw. The fourth magnet  80   d  is attached to the mount  65  via an interference fit, and the fourth magnet  80   d  receives an end of the plunger  76  so that the plunger  76  is movable with respect to the fourth magnet  80   d.  The third fastener  82   c  also holds the plunger  76  in a depressed position shown in  FIG. 2 , so that the plunger  76  pushes against the spring force of the button  58  and holds the button  58  in a depressed position. Furthermore, the first and second magnets  80   a  and  80   b,  respectively, are oriented so that they are attracted to each other, and the third and fourth magnets  80   c  and  80   d , respectively, are oriented so that they are also attracted to each other. 
     In another embodiment, the mount arrangement  54  may include a single pair of magnets. For example, in such an embodiment, the mounting arrangement  54  may include the above-described third and fourth magnets  80   c  and  80   d,  respectively but not the first and second magnets  80   a  and  80   b,  respectively. 
     The mounting arrangement  54  may further include a cover  84  that covers one or more of the other components of the mounting arrangement. In the illustrated embodiment, the cover  84  is positioned over the intermediate member  78  and magnets  80   a - 80   d  to inhibit dirt, moisture and/or debris from contacting the magnets  80   a - 80   d.    
     Referring to  FIGS. 1-4 , operation of the vehicle  10  will now be described in further detail. When the vehicle  10  is located in a desired position and suitably supported or otherwise braced, the operator may enter the work platform assembly  16  through the door  38 . The operator may then move the work platform assembly  16  using the control unit  40 . The work platform assembly  16  may first require that the operator activate an enabling element, so that the control unit  40  may be operated to move the work platform assembly  16  and in order to activate the obstruction proximity sensing system  18 . For example, the work platform assembly  16  may include a foot-switch (not shown) that the operator may step on in order to allow operation of the control unit  40  and the obstruction proximity sensing system  18 . 
     The operator may move the work platform assembly  16  as desired using the controls of the control unit  40 . For example, the controls may be used to control movement of the support assembly  14  and/or movement of the work platform assembly  16  with respect to the support assembly  14 . While the work platform assembly  16  is in motion, one or more of the proximity sensor assemblies  42  of the obstruction proximity sensing system  18  may detect presence of one or obstructions by contacting the one or more obstructions. 
     Referring to  FIGS. 1-3 , when the wand assembly  52  of a particular proximity sensor assembly  42  contacts an obstruction, the movable mounting arrangement  54  is configured to allow the wand assembly  52  to move with respect to the base  44  and the switch  50  from a home position (shown in solid lines on the left side of  FIG. 1 , and in  FIG. 2 ) to a displaced position (shown in phantom lines on the left side of  FIG. 1 , and in  FIG. 3 ). For example, referring to  FIG. 3 , if the force on the wand assembly  52  is sufficient, the spring member  70  may flex or otherwise move to allow the wand assembly holder  66  to move with respect to the base  44  and the switch  50  so that the first magnet  80   a  separates from the second magnet  80   b , and so that the third magnet  80   c  separates from the fourth magnet  80   d.  As a result, the third fastener  82   c  associated with the third magnet  80   c  may likewise move away from the fourth magnet  80   d  to allow the plunger  76  and the button  58  of the switch  50  to move sufficiently away from the switch body  56  of the switch  50 , due to urging by the spring associated with the button  58 , thereby actuating the switch  50  (e.g., separating the contacts  57   a  and  57   b  of the switch  50 ). The switch  50 , which may be connected to the control arrangement  28  of the work platform assembly  16 , may then cause the control arrangement  28  to shut down. For example, actuation of the switch  50  may cause electrical power to be disconnected from the control unit  40  of the control arrangement  28 . The vehicle  10  may also include a control (e.g., button, switch, lever, etc.) that may be actuated or otherwise activated to override the switch  50  and return power to the control unit  40  or other portion of the control arrangement  28 . For example, the control unit  40  may include an override control that may be actuated to restore power. 
     When the wand assembly  52  is no longer contacting the obstruction, the spring member  70  urges the wand assembly  52  back toward the home position shown in  FIG. 2 . Furthermore, the magnets  80   a - 80   d  may advantageously function to limit over-travel of the wand assembly  52  as the wand assembly  52  returns to the home position. For example, the magnets  80   a - 80   d  may be configured to limit over-travel of the wand assembly  52  beyond the home position to less than 20% of the displaced distance when the wand assembly  52  is moved from the displaced position to the home position and then beyond the home position due to whipping motion of the wand assembly  52 . In that regard, the first and second magnets  80   a  and  80   b,  respectively, are drawn toward each other, and the third and fourth magnets  80   c  and  80   d,  respectively, are drawn toward each other, so that the wand assembly  52  is inhibited from moving significantly beyond the home position when the and assembly  52  is urged toward the home position. The magnets  80   a - 80   d  may also inhibit the wand assembly  52  from oscillating between the home position and the displaced position. The magnets  80   a - 80   d  may therefore act as damping members that provide an anti-whipping function for the wand assembly  52 . 
     When the magnets of the magnet pairs  80   a - 80   b  and  80   c - 80   d  are separated from each other, the intermediate member  78  is movably retained by the spring member  70 . In such case, the intermediate member  78  may be considered to “float” in a space defined by the spring member  70 . Furthermore, the intermediate member  78  and the second and third magnets  80   b  and  80   c , respectively, may together be considered an intermediate magnet assembly or mid-magnet assembly. 
     Furthermore, use of two magnet pairs  80   a,    80   b  and  80   c,    80   d  and the intermediate member  78  (i.e., floatable segment) may enable softer movement damping of the wand assembly  52  compared with a single magnet pair. Furthermore, the strength of the magnets may be selected so that only one magnet pair separates at a time. For example, the strength of attraction of the third and fourth magnets  80   c  and  80   d,  respectively, may be less than the strength of attraction of the first and second magnets  80   a  and  80   b,  respectively, so that the third and fourth magnets are configured to separate before the first and second magnets separate. With such a configuration, the switch  50  may be actuated when the wand assembly  52  is only slightly displaced. Furthermore, continued displacement of the wand assembly  52  may cause the first and second magnets  80   a  and  80   b,  respectively, to separate to prevent or inhibit damage to the wand assembly  52 . 
     Although the wand assembly  52  may be connected to the wand assembly holder  66  in any suitable manner as mentioned above, use of a set screw may allow the wand assembly  52  to be fixed in any suitable orientation with respect to the wand assembly holder  66 . With such a configuration, the and assembly  52  may be positioned (e.g., rotated) with respect to the wand assembly holder  66  to achieve a desired orientation with respect to potential obstructions, and then the wand assembly  52  may be secured in that orientation with the set screw. 
     Referring to  FIGS. 2-6 , the first and second portions  45  and  46 , respectively, of the base  44  may sandwich the switch  50 , mount  68  and spring member  70  therebetween when the portions  45  and  46  are connected together to provide secure attachment between the base  44  and the rest of the proximity sensor assembly  42 . Furthermore, one or both portions  45 ,  46  may include a mounting feature that cooperates with the switch  50  to hold the switch  50  securely in place. In the embodiment shown in  FIGS. 2 and 3 , the second portion  46  includes one or more recesses  86  that each receive a projection  88 , such as a ridge, formed on the switch body  56  of the switch  50 . 
     Referring to  FIG. 7 , additional details of an embodiment of the proximity sensor assembly  42  will now be described for orienting the wand assembly  52  with respect to the wand assembly holder  66 . For example, one of the wand assembly  52  and the wand assembly holder  66  may include one or more projections (e.g., at least two projections) that are each selectively receivable in one of multiple notches or slots formed in the other of the wand assembly  52  and the wand assembly holder  66  so that the wand assembly  52  may be oriented in any one of multiple orientations with respect to the wand assembly holder  66 . As a more specific example, one of the wand assembly  52  and the wand assembly holder  66  may include two projections that are selectively receivable in two of multiple slots (e.g., at least four slots) formed in the other of the wand assembly  52  and the wand assembly holder  66 . In the illustrated embodiment, the wand assembly  52  includes two projections  90   a  and  90   b,  and the wand assembly holder  66  includes eight slots  92  for selectively receiving the projections  90   a  and  90   b.  Furthermore, the projections  90   a  and  90   b  are spaced apart by 180° center to center, and the slots  92  are spaced equally about a perimeter of the wand assembly holder  66  so that adjacent slots  92  are spaced apart by 45° center to center. With such a configuration, position of the wand assembly  52  may be adjusted in 45° increments with respect to the wand assembly holder  66  and/or platform  26  in order to position the angled head portion  62  of the wand assembly  52  in a desired orientation with respect to the wand assembly holder  66  and/or platform  26 . Once a desired orientation has been selected, the wand assembly  52  may be connected to the wand assembly holder  66  in any suitable manner, such as with a set screw  94  that extends through an opening in the wand assembly holder  66  and into a notch or grove  96  (e.g., circumferential groove) formed in the main body portion  60  of the wand assembly  52 . 
     Referring to  FIGS. 8 and 9 , a second embodiment  42 ′ of a proximity sensor assembly is shown. The proximity sensor assembly  42 ′ includes various similar features as the proximity sensor assembly  42 , and those similar features are identified with the same reference numbers, except the similar reference numbers in  FIGS. 8 and 9  each include a prime mark. Therefore, the following description will primarily focus on the differences between the proximity sensor assembly  42 ′ and the proximity sensor assembly  42 . In that regard, the proximity sensor assembly  42 ′ includes a simplified movable mounting arrangement  54 ′ associated with (e.g., connected to) switch  50 ′ (e.g., limit switch, cut-off switch, etc.) and a detection member, such as wand assembly  52 ′. In the illustrated embodiment, the mounting arrangement  54 ′ includes a detection member holder, such as wand assembly holder  66 ′, connected to the wand assembly  52 ′, and a biasing member, such as a spring member  70 ′, associated with base  44 ′, the switch  50 ′ and the wand assembly holder  66 ′. Furthermore, the spring member  70 ′ is configured to provide a biasing characteristic for urging the wand assembly  52 ′ toward a home position, shown in  FIGS. 5 and 6 , and a damping characteristic for damping or dampening movement of the wand assembly  52 ′, as explained below in greater detail. For example, the spring member  70 ′ may be a conically-shaped, coil extension spring. 
     In the illustrated embodiment, the spring member  70 ′ is connected to the base  44 ′ and the wand assembly holder  66 ′. For example, the base  44 ′ may include a threaded portion (not shown), the wand assembly holder  66 ′ may include a threaded portion  72 ′, and the spring member  70 ′ may be a coil, extension spring that is connected to the threaded portions, such as by rotating the spring member  70 ′ and/or the base  44 ′ and wand assembly holder  66 ′ relative to each other. As another example, the spring member  70 ′ may be connected to the base  44 ′ and/or the wand assembly holder  66 ′ with suitable fasteners, such as clamps. 
     The mounting arrangement  54 ′ further includes an engaging member, such as a plunger  76 ′, that is fixedly connected to the wand assembly holder  66 ′ and engageable with an actuator, such as a spring-biased button  58 ′, of the switch  50 ′. When the wand assembly  52 ′ is in the home position shown in  FIGS. 8 and 9 , the plunger  76 ′ pushes against the spring force of the button  58 ′ and holds the button  58 ′ in a depressed position. When the wand assembly  52 ′ is moved to a displaced position similar to that shown in  FIG. 3 , due to contact with an obstruction for example, the plunger  76 ′ may move sufficiently away from switch body  56 ′ of the switch  50 ′, so that the button  58 ′ may likewise move away from the switch body  56 ′ to actuate the switch  50 ′. The switch  50 ′, which may be connected to the above-mentioned control arrangement  28  of the work platform assembly  16 , may then cause the control arrangement  28  to shut down. For example, actuation of the switch  50 ′ may cause electrical power to be disconnected from the control unit  40  of the control arrangement  28 . 
     When the wand assembly  52 ′ is no longer contacting the obstruction, the spring member  70 ′ urges the wand assembly  52 ′ back toward the home position shown in  FIGS. 8 and 9 . Furthermore, the conical shape of the spring member  70 ′ may advantageously function to limit over-travel of the wand assembly  52 ′ as the wand assembly  52 ′ returns to the home position. For example, the spring member  70 ′ may concentrate spring force toward the wand assembly holder  66 ′ and wand assembly  52 ′, due to the spring member  70 ′ being tapered toward the wand assembly holder  66 ′ and wand assembly  52 ′, so that the wand assembly  52 ′ is urged more quickly to the home position as compared to a cylindrical coil spring. The spring member  70 ′ may provide a biasing characteristic as weal as a dampening characteristic. 
     It should be noted that features of any of the above embodiments may be combined together to form other embodiments according to the disclosure. For example, the proximity sensor assembly  42  may be provided with a conically-shaped spring member, instead of a cylindrically shaped spring member. As another example, the proximity sensor assembly  42 ′ may include at least one damping member, in addition to the spring member  70 ′, to dampen movement of the wand assembly  52 ′. In that regard, the proximity sensor assembly  42 ′ may include at least one magnet or other magnet arrangement, such as described above with respect to the proximity sensor assembly  42 . 
     The below paragraphs describe general aspects that may be included in embodiments according to the disclosure. 
     A proximity sensor assembly according to the disclosure may include a detection member, a switch, and a movable mounting arrangement associated with the detection member and the switch. The movable mounting arrangement may include a biasing characteristic for urging the detection member toward a home position after the detection member has been displaced from the home position, and a dampening characteristic for dampening movement of the detection member. Furthermore, the switch is actuatable when the detection member is displaced from the home position. 
     The mounting arrangement of the proximity sensor assembly may include an extension spring to provide the biasing characteristic. The mounting arrangement may comprise a conical spring that provides the biasing characteristic and at least a portion of the dampening characteristic. 
     The mounting arrangement of the above proximity sensor assembly may comprise a biasing member that provides the biasing characteristic, and a detection member holder attached to the detection member and having a threaded portion. Furthermore, the biasing member may be attached to the threaded portion of the detection member holder. 
     The switch of the above proximity sensor assembly may comprise a switch body and an actuator that is movable with respect to the switch body, and the mounting arrangement may further comprise an engaging member for engaging the actuator of the switch. When the detection member is sufficiently displaced from the home position, the engaging member may be movable away from the switch body to actuate the switch. Furthermore, the mounting arrangement may comprise a biasing member that provides the biasing characteristic, and a mount connected to the switch and having a threaded portion that is connected to the biasing member. The mounting arrangement may also comprise a detection member holder connected to the detection member, and the engaging member may be fixedly connected to the detection member holder. 
     The above proximity sensor assembly may include at least one damping member that provides at least a portion of the dampening characteristic. For example, the proximity sensor assembly may include at least one magnet. 
     As another example, the at least one damping member may comprise a pair of magnets that are positioned adjacent each other when the detection member is in the home position, and that are separable from each other when the detection member is urged away from the home position. Furthermore, the magnets may be configured to be drawn toward each other when the detection member is urged bark toward the home position by the biasing characteristic after having been displaced from the home position. 
     As yet another example, the at least one damping member may comprise two pairs of magnets that each comprise first and second magnets. The first and second magnets of each pair may be positioned adjacent each other when the detection member is in the home position, and the first and second magnets of each pair may be separable from each other when the detection member is urged away from the home position. Furthermore, the first and second magnets of each pair may be configured to be drawn toward each other when the detection member is urged back toward the home position by the biasing characteristic after having been displaced from the home position. 
     As yet another example, the at least one damping member may comprise first, second, third and fourth magnets. When the detection member is in the home position, the first and second magnets are positioned adjacent each other and the third and fourth magnets are positioned adjacent each other. When the detection member is urged away from the home position, the first and second magnets are separable from each other and the third and fourth magnets are separable from each other. Furthermore, when the detection member is urged back toward the home position by the biasing characteristic after having been displaced from the home position, the first and second magnets are configured to be drawn toward each other and the third and fourth magnets are configured to be drawn toward each other. In addition, the mounting arrangement may further comprise a spacer member, and the second and third magnets may be attached to the spacer member so that the second and third magnets are spaced apart from each other. 
     For the above proximity sensor assembly with four magnets, the switch may comprise a switch body, and an actuator that is movable with respect to the switch body. In addition, the mounting arrangement may further comprise a detection member holder attached to the detection member, an engaging member for engaging the actuator of the switch, and a mount connected to the switch and that receives the engaging member. Furthermore, the first magnet may be attached to the detection member holder, and the fourth magnet may be attached to the mount. When the detection member is sufficiently displaced from the home position, the engaging member may be movable away from the switch body to actuate the switch. 
     The mounting arrangement of the immediately preceding proximity sensor assembly may include a biasing member that provides the biasing characteristic. Furthermore, the detection member holder and the mount may each have a threaded portion, and the biasing member may be attached to the threaded portions. 
     The mounting arrangement of the proximity sensor assembly described in paragraph may include a detection member holder for receiving the detection member. Furthermore, one of the detection member and the detection member holder may include two projections that are receivable in two of multiple slots formed in the other of the detection member and the detection member holder so that the detection member may be oriented in any one of multiple orientations with respect to the detection member holder. 
     The detection member of the proximity sensor assembly of the immediately preceding paragraph may include the two projections, and the two projections may be spaced apart by 180° center to center. Furthermore, the detection member holder may include at least four slots for selectively receiving the projections. 
     The detection member holder of the proximity sensor assembly of the immediately preceding paragraph may include eight slots for selectively receiving the projections. Furthermore, adjacent slots may be spaced apart by 45° center to center. 
     According to at least one embodiment of the disclosure, a mobile work platform assembly is provided for use with a movable support assembly that is configured to move the mobile work platform assembly. The mobile work platform assembly may include a work platform sized to receive an operator, a control arrangement associated with the work platform for controlling movement of the work platform, and a proximity sensor assembly associated with the work platform. The proximity sensor assembly may include a detection member, an actuatable switch, and a movable mounting arrangement associated with the detection member and the switch. The movable mounting arrangement may include a biasing characteristic for urging the detection member toward a home position after the detection member has been displaced from the home position, and a dampening characteristic to dampen movement of the detection member. Furthermore, when the detection member is displaced from the home position, the switch is actuatable to inhibit operation of the control arrangement. 
     The mounting arrangement of the above mobile work platform assembly may comprise a coil spring that provides the biasing characteristic, and a detection member holder attached to the detection member and having a threaded portion. In addition, the coil spring may be attached to the threaded portion of the detection member holder. 
     The mounting arrangement of the above mobile work platform assembly may comprise a conical spring that provides the biasing characteristic and at least a portion of the dampening characteristic. 
     The proximity sensor assembly of the above mobile work platform assembly may include at least one damping member that provides at least a portion of the dampening characteristic. For example, the at least one damping member may comprise a pair of magnets that are positioned adjacent each other when the detection member is in the home position, and that are separable from each other when the detection member is urged away from the home position. Furthermore, the magnets may be configured to be drawn toward each other when the detection member is urged back toward the home position after having been displaced from the home position. 
     As another example, the at least one damping member of the above mobile work platform assembly may comprise first, second, third and fourth magnets. When the detection member is in the home position, the first and second magnets may be positioned adjacent each other and the third and fourth magnets may be positioned adjacent each other. When the detection member is urged away from the home position, the first and second magnets may be separable from each other and the third and fourth magnets may be separable from each other. When the detection member is urged back toward the home position after having been displaced from the home position, the first and second magnets may be configured to be drawn toward each other and the third and fourth magnets may be configured to be drawn toward each other. In addition, the mounting arrangement may further comprise a spacer member, and the second and third magnets may be attached to the spacer member so that the second and third magnets are spaced apart from each other. 
     The switch of the above mobile work platform assembly may comprise a switch body, and an actuator that is movable with respect to the switch body. In addition, the mounting arrangement may further comprise a detection member holder attached to the detection member, an engaging member for engaging the actuator of the switch, and a mount connected to the switch. Furthermore, the first magnet may be attached to the detection member holder, and the fourth magnet may be attached to the mount. When the detection member is sufficiently displaced from the home position, the engaging member is movable away from the switch body to actuate the switch. 
     A vehicle according to the disclosure may include a vehicle body, a support assembly connected to the vehicle body, and a mobile work platform assembly supported by the support assembly so that the work platform assembly is movable with respect to the vehicle body. The work platform assembly may include a work platform sized to receive an operator, a control arrangement associated with the work platform for controlling movement of the work platforms, and a proximity sensor assembly associated with the work platform. The proximity sensor assembly may include a detection member, an actuatable switch, and a movable mounting arrangement associated with the detection member and the switch. The mounting arrangement may include a biasing characteristic for urging the detection member toward a home position after the detection member has been displaced from the home position, and a dampening characteristic for dampening movement of the detection member. When the detection member is displaced from the home position, the switch is actuatable to inhibit operation of the control arrangement. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms according to the disclosure. In that regard, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. Additionally, the features of various implementing embodiments may be combined to form further embodiments according to the disclosure.