Abstract:
A low profile limit switch utilizes a bowed spring actuator for advancing a bridge contact into and out of contact with a pair of terminal contacts to close and open the switch. The bridge contact is mounted on a glide on an end of the spring and formed from an insulating material. The terminal contacts are spring loaded and maintained in spaced apart and staggered relationship so that only one of the terminal contacts remains in contact with the bridge contact when it is retracted by the bowed spring. A mounting clip including a mounting flange and spaced apart spring loaded arms extending generally perpendicular to the mounting flange is used to mount the switch to a surface proximate an edge without having to obtain any significant amount of vertical clearance above the switch for bolting it to the surface.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to switches utilizing a bowed spring as an actuating mechanism. 
   In U.S. Pat. No. 5,446,252, issued Aug. 29, 1995, a switch assembly was disclosed utilizing a flat spring actuating mechanism formed from a bowed piece of spring steel for engaging the plunger of a plunger type switch. An improved, water resistant version is disclosed in U.S. Pat. No. 6,982,392. Commercial embodiments of these switch assemblies have been sold as the THINSWITCH® limit switch by Burger &amp; Brown Engineering, Inc. The flat spring actuating mechanism is particularly well adapted for use with plunger type switches that are often referred to as micro-switches. In such micro-switches, the length or height of the switch (the dimension of the switch extending along the axis of the plunger) is generally considerably greater than the thickness of the switch. To minimize the thickness of the switch assembly, the micro switch is mounted on its side in a housing and the bowed spring is positioned in the housing so a first end abuts against the plunger with the middle portion of the spring extending up through a hole or slot in the housing. Pressing down on the middle portion of the spring causes the ends of the spring to move outward, driving the first end against the plunger and advancing the plunger a sufficient distance to change the condition of the switch. Upon removal of the external force acting on the spring, the spring returns to its original bowed state such that the first end of the spring advances away from the plunger and the plunger is allowed to move to the extended position changing the switch back to its original condition. 
   The switch assembly utilizing the flat spring actuating mechanism disclosed in U.S. Pat. No. 5,446,252 is particularly well adapted for use as a position sensing switch to sense when one portion of a piece of equipment is or is not positioned in a designated position. For example, a mold assembly for an injection mold utilizes ejector pins for ejecting the molded part out of the mold when mold halves of the mold assembly are separated. The ejector pins are typically mounted on an ejector plate that moves between extended and retracted positions relative to a respective mold half to advance the ejector pins into and out of the mold cavity formed in the mold half for ejecting the molded part from the mold assembly. It is important to ensure that the ejector pins are withdrawn from extending into the mold cavity before the two mold halves are brought together in the subsequent cycle for molding the next part. If the pins are not retracted they may be damaged upon closing of the mold. 
   The switch assembly of U.S. Pat. No. 5,446,252 is particularly well adapted for confirming that the ejector plate, and therefore the ejector pins, are fully retracted before closing the mold. When the ejector plate is fully retracted, low profile, cylindrical stops on an outer surface of the ejector plate abut against an interior wall of the mold assembly and more specifically an interior wall of the ejector housing. Alternatively, the stops may be mounted on the interior wall of the ejector housing. In most molds made in the United States, the height of the cylindrical stops is typically 3/16 of an inch or 0.1875 inches. 
   A preferred micro switch utilized in the THINSWITCH limit switch for the ejector plate application as described, is a subminiature basic switch No. 91SX39-T sold by the Micro Switch Division of Honeywell. This switch has a thickness of approximately 0.156 inches and is believed to be the thinnest micro switch having sufficient mechanical life and electrical rating for its intended application. At 0.156 inches, the 91SX39-T switch can be utilized in the switch assembly and fit within the gap of 0.1875 inches created by the stops on the ejector plate. 
   However, in molds manufactured in Europe and Asia, the stops are often only 3 millimeters (mm) or 0.118 inches tall, which is less than the thickness of the smallest commercially available micro-switch having sufficient life cycle and electrical rating for use as part of a limit switch assembly for mold ejection assemblies. Therefore, there remains a need for an even thinner yet rugged position sensing switch assembly which is particularly well adapted for industrial applications including use in association with injection molding machines. 
   There also remains a need for a better system for attaching the switch assembly of the type disclosed in U.S. Pat. No. 5,446,252 to an ejector housing of a mold assembly. Currently, the mold must be disassembled to provide sufficient access to the ejector housing to allow holes to be tapped therein so that the switch assembly housing may be screwed to the ejector housing. 
   SUMMARY OF THE INVENTION 
   The present invention comprises a low profile position sensing switch utilizing a bowed spring as an actuator and which may also be secured in place using a mounting clip with spring biased arms engaging a portion of the switch housing. The switch includes a pair of terminal contacts mounted in spaced apart relationship within the switch housing and in electrical contact with a pair of conductors from a power supply cable. A bridge contact is mounted on a first end of the bowed spring with a middle portion of the bowed spring extending above an upper surface of the housing. The bowed spring being positioned within said housing such that when the bowed spring is in a resting position, the bridge contact is positioned proximate said first and second terminal contacts with no more than one of the terminal contacts in contact with the bridge contact. Compression of the middle portion of the bowed spring downward advances the first end of the spring toward the terminal contacts and into engagement with both terminal contacts changing the condition of the switch from its normally open condition to a closed condition. Upon removal of the compressive force on the bowed spring the first spring end advances away from the terminal contacts a distance sufficient to advance the bridge contact out of engagement with at least one of the terminal contacts changing the condition back to open. 
   The terminal contacts preferably comprise spring probes having a plunger spring loaded within a cylindrical barrel. The terminal contacts are held in spaced relation in bores formed in a terminal connector block. The terminal connector block includes flexible sidewalls to accommodate insertion of the end of a conductor and a spring probe in each of the bores and compress the conductor against the spring probe. Stops formed in the connector block at the end of each bore are staggered such that one of the spring probes extends out of the connector block further than the other spring probe. 
   The mounting clip includes a mounting flange for attachment to an edge adjacent and perpendicular to a support surface to which the switch is to be mounted. Spring arms extend outward from the mounting bracket at an angle of approximately ninety degrees or slightly less relative to the mounting flange, such that the spring arms may angle slightly downward. Inwardly curved or directed detents are formed on distal ends of the spring arms with a dimple or boss projecting downward from each of the detents. Corresponding recesses are formed in the upper surface of ears or wings projecting outward from the main portion of the switch housing. The spring arms are spaced apart a distance generally corresponding to the width of the switch housing. The switch housing is slid between the arms until the bosses on the detents engage a leading ramp like edge of each wing. The bosses slide over the leading edge until the bosses advance over and then drop into the recesses such that the spring arms hold the switch against the surface to which it is mounted. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a fragmentary, perspective view of a limit switch assembly mounted on a surface of a mold ejector housing by a mounting clip. 
       FIG. 2  is a bottom plan view of the limit switch assembly with a backing sheet removed to show detail thereof. 
       FIG. 3  is a cross-sectional view generally taken generally along line  3 - 3  of  FIG. 2  and showing the limit switch assembly secured within an ejector plate assembly of an injection mold with the ejector plate in an extended position. 
       FIG. 4  is a view similar to  FIG. 3  showing the ejector plate advanced into engaging relation with and compressing a bowed spring actuating mechanism of the limit switch assembly to advance a bridge contact connected to the bowed spring into engagement with a pair of terminal contacts. 
       FIG. 5  is an enlarged, fragmentary and exploded perspective view showing the terminal contacts, electrical conductors and a terminal connector block, the terminal connector block holding the terminal contacts and the conductors in electrical contact within a housing for the limit switch assembly. 
       FIG. 6  is an enlarged and fragmentary cross-sectional view taken generally along line  6 - 6  of  FIG. 4  showing the terminal contacts and the conductors mounted within the terminal connector block with the bridge contact engaging and compressing plungers of the terminal contacts. 
       FIG. 7  is an enlarged cross-sectional view of the terminal connector block with the terminal contacts and conductors secured therein and taken generally along line  7 - 7  of  FIG. 6   
       FIG. 8  is an enlarged and fragmentary cross sectional view taken generally along line  8 - 8 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
   Referring to the drawings in more detail, the reference numeral  1  refers to a low-profile switch assembly. As used herein, the front of the switch assembly  1  is shown to the left hand side in  FIG. 2 . The switch assembly  1  is shown in  FIG. 1  mounted to an inner surface  4  of a mold ejector housing  5  by a mounting clip  8 . As shown in  FIGS. 2-6 , the low-profile switch assembly  1  includes a switch housing  11 , a leaf spring or bowed spring  13  with first and second glides  14  and  15  mounted on or connected to first and second ends  16  and  17  respectively of the bowed spring  13 , an electrically conductive bridge contact  20  mounted on an outer face  21  of the first glide  14 , and first and second terminal contacts  24  and  25  mounted within a terminal connector block  28 . As will be discussed in more detail hereafter and as best seen in  FIGS. 2 and 5 , the terminal connector block  28  is mounted within the housing  11  such that distal ends of the terminal contacts  24  and  25  extend in closely spaced relation to the bridge contact  20  on the first glide  14 . 
   Power is supplied to the switch assembly by a power supply cable  32 , which preferably comprises a shielded cable with a drain ground. The power supply cable  32  is shown exiting the housing  11  to the rear thereof in  FIGS. 1 and 2 . The power supply cable  32  includes first and second conductors or leads  33  and  34  and is connected to and extends into the housing  11  with the first and second conductors  33  and  34  connected at first ends thereof to the first and second terminals  24  and  25  respectively in the terminal connector block  28 . The cable  32  is connected at second ends of the first and second conductors  33  and  34  to a processor or the like (not shown) for receiving signals from the switch assembly  1  indicative of whether the switch assembly  1  is in an open (off) or closed (on) condition. 
   The first and second terminal contacts  24  and  25  are electrically conductive and in the embodiment shown comprise spring contact probes. An example of a spring contact probe which is particularly well adapted for use as the terminal contacts  24  and  25  of the switch assembly  1  is an SS-100/GSS-100 probe sold by Interconnect Devices, Inc. utilizing a tip style number  10 , which generally comprises a hemi-spherical tip. 
   Each spring contact probe utilized as the terminal contacts  24  and  25  includes a barrel  38 , a plunger  39  and a compression spring  40 . Each barrel  38  is cylindrical with an open end  42 , a closed end  43  and an internal shoulder  44  formed by crimping the barrel  38  generally medially along its axis. Each plunger  39  includes a head  46  with a tip or distal end  47 , a shaft  48  of reduced diameter and a base or tail end  49  generally equivalent in diameter with the head  46 . The plunger  39  is mounted within the barrel  38  with the base  49  positioned between the closed end  43  and the shoulder  44  and with the compression spring  40  abutting at one end against the closed end  43  of the barrel  38  and at an opposite end against the plunger base  49 . The outer diameter of the plunger base  49  is larger in diameter than the plunger shaft  48  and larger than the inner diameter of the internal shoulder  44  to prevent the plunger from being urged completely out of the barrel  38 . The spring  40  engages and normally urges the plunger  39  outward relative to the barrel  38  (rearward relative to the switch assembly housing  11 ) to an extended position. The plunger  39  is compressible to a compressed position relative to the barrel and against the biasing force of the compression spring  40 . All of the components of the terminal contacts  24  and  25  are preferably formed from electrically conductive material such that the terminal contacts  24  and  25  are electrically conductive. 
   The terminal connector block  28  is preferably formed from plastic or other non-conductive materials. The block  28  functions to hold the terminal contacts  24  and  25  in the desired alignment relative to one another and relative to the bridge contact  20 . The terminal connector block  28  also facilitates holding the exposed ends of the first and second conductors  33  and  34  in electrically conductive contact with the terminal contacts  24  and  25 . As generally shown in  FIG. 7 , the conductors  33  and  34  may comprise multi-strand wire such as copper wire. The block  28  may be described as having a rear  51 , front  52 , top  53 , bottom  54  and sides  55  and  56 . First and second bores  59  and  60  extend into the block  28  from the rear  51  toward the front  52  in spaced relation on opposite sides of an axis of the block  28  with first and second stops  62  and  63  formed at the end of bores  59  and  60  respectively. The first bore  59  extends into the block  28  to a greater depth than the second bore  60 , such that stop  62  is spaced further forward from the block rear  51  than the stop  63 . 
   In the disclosed embodiment, first and second mounting arms  65  and  66  project laterally outward from the first and second sides  55  and  56  of the block  28 . The arms  65  and  66  are adapted for securing the block  28  within the housing and restricting axial movement of the block  28  relative thereto as described in more detail hereafter. First and second notches  69  and  70  extend into the sides  55  and  56  respectively of the block  28 , generally adjacent the first and second mounting arms  65  and  66  and open into the axial bores  59  and  60 . 
   First and second grooves  73  and  74  extend into the block  28  from the top or upper surface  53  and opening into the first and second bores  59  and  60  respectively generally along the axis of each bore  59  and  60 . Each groove  73  and  74  intersects with and extends from the respective notch  69  and  70  to the stops  62  and  63  at the end of each bore  59  and  60 . The grooves  73  and  74  generally function as expansion joints and create block sidewalls  77  and  78  which flex or expand outward to allow expansion of the size of the axial bores  59  and  69  and thereby accommodate the volume of both the respective terminal contact  24  and  25  and the associated conductor  33  and  34 . The notches  69  and  70  facilitate insertion of the stripped ends of the conductors  33  and  34  into the respective axial bores  59  and  60 , prior to insertion of the terminal contacts  24  and  25  therein. Due to the resilient nature of the plastic forming the terminal connector block  28 , the block sidewalls  77  and  78  generally compress against the respective conductors  33  and  34  and the terminal contacts  24  and  25  to ensure electrical connection therebetween. 
   The terminal contacts  24  and  25  are fully inserted into the block  28 , such that the closed end  43  of the barrel  38  of each contact  24  and  25  abuts against a respective stop  62  and  63 . Because the first stop  62  in block  28  is positioned further into the block  28  or forward of the second stop  63 , the tip  47  of the plunger  39  of the second terminal contact  25  projects further outward or rearward from the terminal connector block  28  than the tip  47  of the plunger  39  of the first terminal contact  25 . It is foreseen that structure for holding the terminal contacts  24  and  25  and the conductors  33  and  34  in the proper alignment and in electrical contact could be molded or otherwise formed directly in the switch housing  11  and not as a separate piece. 
   The switch housing  11  is preferably formed from a relatively hard, rigid material such as a hard plastic. The housing  11  includes an upper surface  81  and a lower surface  82 . As is best seen in  FIGS. 3 and 4 , the distance between the upper surface  81  and the lower surface  82  of the housing  11  is preferably only slightly greater than the thickness of the terminal connector block  28 . A terminal receiving cavity  83  is formed in the housing  11  and extends from the lower surface  82  toward the upper surface  81  thereof. The terminal receiving cavity  83  includes a central portion  84  and first and second slots  85  and  86  projecting sideways or outward from the main portion  84  on opposite sides thereof. The terminal receiving cavity  83  is sized to receive the terminal connector block  28  with the first and second mounting arms  65  and  66  extending into the first and second slots  85  and  86  respectively to fix the axial position of the terminal connector block  28  within the housing  11 . The terminal connector block  28  is secured in the cavity  83  such that the axis of the plungers  39  of each terminal contact  24  and  25  extends in parallel relation with the upper and lower surfaces  81  and  82  of the switch assembly housing  11 . 
   A circular recess  90  (seen in cross-section in  FIGS. 3 and 4 ) extends into the housing  11  from the upper surface  81  toward the lower surface  82 . A spring receiving channel, slot or opening  92  is formed in and extends into the housing  11  from the lower surface  82  toward the upper surface  81 . The spring receiving slot  92  is preferably rectangular and extends across the circular recess  90  coaxially with the axis of the terminal connector block  28 . A first end  93  of the slot  92  connects to and opens into the terminal receiving cavity  83  such that the plungers  39  of the first and second terminal contacts  24  and  25  extend into the slot  92 . In addition, the slot  92 , near its first end  94  does not extend completely through the housing  11  such that a portion of the housing  11  extends over the slot  92  at the slot first end  94  to form a first overhang  95 . Similarly, the slot  92 , near a second end  96  thereof, does not extend completely through the housing  11  such that a portion of the housing  11  extends over the slot  92  at the slot second end  96  to form a second overhang  97 . 
   A wiring channel  100  is also formed in the housing  11  so as to extend from the lower surface  82  and toward but not completely to the upper surface  81  of the housing  11 . A first end  101  of the channel  100  opens into the terminal receiving cavity  83  at an end of the cavity  83  opposite the spring receiving channel  92 . A second end  102  of the wiring channel  100 , extends out of a side or edge of the  103  of the housing  11 . The first end of the power supply cable  32  including the first and second conductors  33  and  34  is secured in the wiring channel  100 . The side or position on the edge of the housing  11  to which the power supply cable  32  needs to be routed may vary depending on the particular application sought and therefore the routing of the channel  100  may vary. A waterproof or water resistant sealing compound or potting compound (not shown) may be injected into the wiring channel  100  to form a water-tight seal around the wiring  100 . 
   The leaf spring or bowed spring  13  is secured within the spring receiving slot  92  and functions as an actuator for the switch. As discussed previously, the spring  13  includes a first spring end  16  with a first glide or shoe  14  mounted thereon, and a second spring end  17  with a second glide or shoe  15  mounted thereon. In its resting state, the spring  13  is bowed and the middle portion of the spring  13  is identified by the reference numeral  113 . 
   Referring to  FIGS. 3 and 4 , each glide  14  and  15  includes an outer face  21 , an inner end  122 , an upper surface  123  and a bottom surface  126 . A notch or groove  128  extends into each glide  14  and  15  from the inner end  122  thereof from side to side and is sized and shaped for receiving the first or second spring end  16  or  17  of spring  13 . An inwardly projecting overhang or upper flange  130  is formed in the glides  14  and  15  above the notch  128  and an inwardly projecting tail or lower flange  131  is formed in the glides  14  and  15  below the notch  128 . The upper flange  130  is preferably shorter than the lower flange  131  and includes an angled or beveled lower surface  132  to accommodate the bow of the spring  13  (as best seen in  FIGS. 3 and 4 ). The glides  14  and  15  are preferably formed from material exhibiting a relatively low coefficient of friction and which functions as an electrical insulator, such as plastic resin sold under the trademark Delrin. 
   The bridge contact  20  is secured to the first glide  14  in a recess  133  formed in the outer face  21  of the first glide  14  such that an outer surface  134  of the bridge contact  20  is exposed to and faces the first and second terminal contacts  24  and  25 . Sides of the recess  133  may be undercut to form overhanging edges along the sides of the recess for holding the bridge contact  20  in place. The bridge contact  20  is formed from electrically conductive material, such as copper and may be mechanically or adhesively secured to the glide  14  or possibly molded in place. The bridge contact  20  is sized to be slightly wider than the spacing of the two terminal contacts  24  and  25  and slightly taller than the diameter of each terminal contact  24  and  25 , such that when the bridge contact  20  is brought into engagement with the terminal contacts  24  and  25  as discussed below, the bridge contact  20  electrically connects the first terminal contact  24  to the second terminal contact  25 . 
   The terminal connector block  28  with terminal contacts  24  and  25  mounted therein, the spring  13 , glides  14  and  15  and power supply cable  32  are held within the housing  11  by a backing or backing sheet  135 . The backing  135  is formed from a layer of relatively thin material, such as a relatively rigid polyester plastic sheet. The relative thickness of the backing sheet  135  shown in the drawings is exaggerated to make the backing sheet  135  readily discernable. The backing  135  is secured to the lower surface  82  of the housing  11  by securement means such as an adhesive. The backing  135  extends across the terminal receiving cavity  83 , the spring receiving slot  92  and the wiring channel  100  to secure the terminal connector block  28  with terminal contacts  24  and  25  mounted therein, the spring  13 , glides  14  and  15  and power supply cable  32  respectively therein. 
   The glides  14  and  15  slide across the backing sheet  75  upon compression and subsequent release of the spring  13  as discussed in more detail below. Adhesive is selectively omitted from the backing  135  in the area in which the glides  14  and  15  will slide across the backing  135  to ensure proper functioning of the switch assembly  1 . Potting compound may be injected into the wiring channel  100  after the backing sheet  135  is secured to the housing  11 . 
   The spring  13  is positioned within the slot  92  of the housing  11  in the resting state, such that the middle portion  113  of the spring  13  extends through the circular recess  90  and bows above the upper surface  41  of the housing  11 . The first glide  14  is generally positioned beneath the first overhang  95  and the second glide  15  is generally positioned beneath the second overhang  97 . The distance between the upper surface of the backing  135  and the lower surface of the first and second overhangs  95  and  97  is just slightly greater than the thickness of the glides  14  and  15  such that the glides  14  and  15  are allowed to slide therebetween without binding. 
   The spring  13  is sized such that when it is positioned in the slot  92 , the bridge contact  20  on the outer face  21  of the first glide  14  is positioned in closely spaced relation to the tip  47  of the extended plunger  39  of the second terminal contact  25 , and the outer face  21  of the second glide  15  is positioned in closely spaced relation to an inner wall  138  of the housing  11  at the slot second end  96 . As used in the preceding description, the phrase “in closely spaced relation” is intended to mean in actual engagement or positioned slightly apart. Because the tip  47  of the extended plunger  39  of the second terminal contact  24  is offset rearward from the tip  47  of the extended plunger  39  of the first terminal contact  25 , the bridge contact  20  is maintained in spaced relation from the plunger tip  47  of the first terminal contact  24  when the bowed leaf spring  13  is in an uncompressed condition. In this condition, the switch assembly  1  is in an open condition, preventing the flow of electricity therethrough. 
   The overall length of the spring receiving channel or slot  92  is greater than the distance between the outer faces  21  of the first and second glides  14  and  15  when the spring  13  is in an uncompressed state, such that the spring force exerted by the compression spring  40  in the second terminal contact  25  is sufficient to maintain space between the bridge contact and the plunger tip  47  of the first terminal contact  24 . 
   A set screw  140  is threaded into a threaded bore  141  formed in the switch housing  11  and extending from an edge  143  of the housing  11  to the second end  96  of spring receiving slot  92 , through inner wall  138 . The inner end of the set screw  140  may be advanced past the inner wall  138  and into the spring receiving slot  92  a selected distance to reduce the effective length of the spring receiving slot  92 , thereby reducing the required distance to be traveled by the first glide  14  to depress the plunger  39  of the second terminal contact  25  and advance the bridge contact  20  into contact with both the first and second terminal contacts  24  and  25  to change the condition of the switch assembly to closed. When the inner end of the set screw  140  is extended through inner wall  138  and into spring receiving slot  92 , the outer face  21  of second glide  15  engages the set screw  140 , at least when the spring  13  is depressed. Prior to depression of the spring  13  the outer face  21  of second glide  15  is positioned in closely spaced relation with the inner end of the set screw  140 . A thread sealing compound is preferably applied to the set screw  140  prior to threading the set screw  140  into the threaded bore  141  to form a water tight seal between the set screw  140  and threaded bore  141 . 
   As is best seen in  FIG. 4 , application of a force to the middle portion  113  of the spring  13  and toward the upper surface  81  of the housing  11  compresses the spring  13  such that the first glide  14  on first spring end  16  advances further away from the second glide  15  on second spring end  17  and toward the first and second terminal contacts  24  and  25 . If not already in contact, the bridge contact  20  is first advanced into contact with the plunger tip  47  of the second terminal contact  25 , compressing the second terminal contact plunger  39  against the force of compression spring  40  until the bridge contact  20  is advanced into contact with the plunger tip  47  of the first terminal contact  24 . As best seen in  FIG. 6 , the first glide  14  and bridge contact  20  preferably are driven far enough toward the terminal connector block  28  upon compression of leaf spring  13 , such that the bridge contact  20  engages and compresses the plungers  39  of both the first and second terminal contacts  24  and  25  to ensure electrical contact therebetween to complete the circuit and change the condition of the switch assembly to closed or on. The spring  13  may be described as translating a force applied perpendicularly to the axis of the terminal contact plungers  39 , to a force applied coaxially with the plungers  39 . As the spring  13  is compressed, the first and second spring ends  11  and  17  are driven into a lower corner in the groove or notch  128  in the respective glide  14  and  15 . 
   Removal of the force applied to the middle portion  113  of the leaf spring  13  allows the leaf spring  13  to return to the resting state such that the first spring end  16  and the attached glide  14  including the bridge contact  20 , advance away from the plungers  39  of the first and second terminal contacts  24  and  25  allowing the plungers  39  to be biased to their extended positions by the compression springs  40  in each terminal contact  24  and  25 . Because the second terminal contact  25  is spaced or offset rearward from the first terminal contact  24 , the spring force exerted by compression spring  40  against the plunger  39  of the second terminal contact  25  ensures that the bridge contact  20  is advanced out of engagement with the first terminal contact  24  when the leaf spring  13  is allowed to return to its resting state thereby ensuring breaking of the electrical circuit and changing the condition of the switch assembly  1  to an open or off condition. 
   Although the glides  14  and  15  are generally only loosely connected to the first and second spring ends  16  and  17 , the downwardly and inwardly directed force exerted by the spring ends  16  and  17  on the inwardly projecting lower flange  131  of the respective glide  14  and  15  may be sufficient to pull the glides  14  and  15  away from the plungers  39  of the terminal contacts  24  and  25  and away from set screw  140  respectively. It is also foreseen that the first glide  14  may only retract the distance that it is pushed rearward by the plunger  39  of the second terminal contact  25  once the force is removed from the middle portion  113  of spring  13 , and the spring ends  16  and  17  will then slide inward along the upper surface of the associated lower flange  131  of each glide  14  and  15 . The lower flange  131  of each glide  14  and  15  is sufficiently long and the distance between the opposed lower flanges  131  when the glides  14  and  15  are separated their furthest distance apart is sufficiently small to prevent either spring end  16  or  17  from sliding off of either of the associated lower flanges  21  when the leaf spring  13  advances to the resting, uncompressed position. It is also to be understood that the glides  14  and  15  could be fixedly secured to the spring ends  16  and  17  by a wide variety of means including adhesives or mechanical connections. 
   A flexible seal or sealing member  145  is mounted on the upper surface  81  of the housing  11  over the leaf spring  13  and the circular recess  90 . The flexible seal  145  preferably is dome shaped or hemispherical with a peripheral flange  147  for securing the seal  145  to the housing  11  in a flange receiving recess  149  formed in the upper surface  81  of the housing  11 . The flange receiving recess  149  is formed around the periphery of the circular recess  90 , and the depth of the flange receiving recess  149  generally corresponds to the thickness of the peripheral flange  147  of the seal  145  so that the upper surface of the flange  147  extends flush with the upper surface  81  of the housing  11 . The flexible seal may be formed from a polyurethane, thermoset film approximately 5 to 10 mils thick. The flange  147  of seal  145  may be secured to the housing by a urethane pressure sensitive adhesive. A circular, flattened area (not shown) may be formed in the seal  145  around its apex. 
   When the seal  145  and spring  13  are compressed by advancement of a machine part or other surface against the seal  145  and the spring  13 , the excess material of the seal  145  is forced into the circular recess  90 . The semi-spherical shape of the seal  145  and the round shape of the circular recess  90  provide a relatively large area for receiving or taking up the excess material of the seal  145  as it is forced downward or inward by advancement of a surface against the seal  145 . The semi-spherical shape of the seal  145  is also believed to result in less stress to the polyurethane material, increasing the life of the seal. 
   The flexible seal  145 , the potting compound injected around the power supply cable  32  and the sealing compound applied to the set screw  140  function to form a water tight or liquid resistant seal around the terminal contacts  24  and  25  and the bridge contact  20 , and the electrical connections between the terminal contacts  24  and  25  and the first and second conductors  33  and  34 . The water resistant switch assembly  1  is particularly adapted for use in applications in which the actuating mechanism may be routinely exposed to water or other liquids. 
   As with the switch assemblies disclosed in U.S. Pat. Nos. 5,446,252 and 6,982,392, the switch assembly  1 , disclosed herein, is securable to various structural members by securement means such as adhesives or bolting. Referring to  FIGS. 2 and 7 , bores  152  are formed in the housing  11  through which screws or bolts (not shown) may be driven for securing the housing  11  to a structure such as the mold ejector housing  5  shown in  FIG. 1 . 
   Alternatively, a variety of clips or mounting brackets such as the mounting clip  8 , as shown in  FIGS. 1 and 8  may be used to secure the switch assembly  1  to a surface such as inner surface  4  of a mold ejector housing  5 . The clip  8  is preferably formed from spring steel (but could be molded from flexible plastic) and includes a mounting flange  155  and first and second spring arms  157  and  158  projecting away from the mounting flange  155  generally at an angle of slightly less than 90 degrees relative thereto such that the spring arms angle downward from the mounting flange  155  to distal ends thereof. The mounting flange  155  includes bolt holes (not shown) through which bolts  159  may be driven to mount the clip  8  to a side edge or surface  160  of the structure to which the switch assembly  1  is to be mounted, such as the mold ejector housing  5 . The distal ends of the spring arms  157  and  158  extend below an upper edge of the mounting flange  155 . 
   The distal ends of the spring arms  157  and  158  curve inward to form an inwardly directed detent or tongue  161  on the end of each arm  157  and  158 . A downwardly projecting dimple  163  is formed in each tongue  161 . The dimples  163 , which may also be referred to as indentations or bosses, are sized to be matingly received in first and second recesses  165  formed in first and second wings  167  forming part of the switch housing  11 . The wings  167  may also be referred to as ears or tabs and project outward from a main portion of the housing  11 , generally on opposite sides of an axis running through the spring receiving slot  92  and generally medially relative to the length of the housing  11 . The bores  152  for mounting the housing  11  using bolts or the like as discussed previously are also formed in the wings  167  and generally extend in alignment with the recesses  165 . A leading edge  169  of each wing  167  projects forward toward a front of the housing  11  and presents an upwardly and rearwardly sloped surface. 
   The spring arms  157  and  158  of the mounting clip  8  are spaced apart a distance which permits the switch housing  11  to be slid therebetween. The first and second detents  161  are positioned by the spring arms  157  and  158  to engage the wings  167  of the switch housing  11  as it is slid between the arms  157  and  158 . The downwardly projecting dimples  163  on each detent  161  engage a leading edge  169  of the associated wings  167 , biasing the detents  161 , and the spring arms  157  or  158  to which they are attached, upward until the dimple  163  passes up and over the front of the respective wing  167  and then drops into the recess  165  therein to form a mechanical connection between the clip  8  and the housing  11  to secure the housing  11  to the mold ejector housing  5  or other structure with which it is to be used. 
     FIGS. 3 and 4  are representative of one use of the actuating mechanism  1  of the present invention in an injection molding application, mentioned above and described in more detail in U.S. Pat. No. 5,446,252. Referring to  FIGS. 3 and 4  of the present application, the reference numeral  173  is representative of an ejector plate advanceable between an ejecting position (represented by  FIG. 3 ) and a retracted position (represented by  FIG. 4 ) by means not shown. In the retracted position, a lower surface  174  of the ejector plate  173  engages stops or rest buttons  175  (one of which is shown in  FIGS. 3 and 4 ) positioned on and extending above the inner surface  4  of the ejector housing  5 . 
   The switch assembly  1 , is used to verify that the ejector plate  173  has returned to the retracted position. The actuating mechanism  1  is sized to have a relatively narrow profile such that the housing  11  and backing sheet  135  are approximately the same thickness or height as and preferably no taller than the thickness of the rest buttons  175  and the upper surface  81  of the housing  11  extends generally flush with upper surfaces of the rest buttons  175 . The middle portion  113  of the spring  13 , when not engaged, extends above the upper surface  81  of the housing  11  and above the upper surfaces of the rest buttons  175 . As the ejector plate  173  is advanced to a retracted position, the lower surface  176  of the ejector plate  173  engages the seal  145  and compresses the spring  13 , advancing the first spring end  16  and first glide  14  with the bridge contact  20  mounted thereon toward and into contact with the first and second terminal contacts  24  and  25  so as to change the condition of the switch assembly  1  from an open condition to a closed condition and send a signal indicating that the ejector plate  173  has returned to the retracted position. 
   Because the mounting clip  8  can be bolted to the side of a mold ejector housing  5 , the switch assembly can be attached to the mold ejector housing  5  without first having to remove the ejector plate  173  from the mold to provide access to otherwise bolt the switch housing  11  to the upper or inner surface  4  of the mold ejector housing  5 . The mold operator can thereby avoid unnecessary downtime or labor in having to disassemble the mold. 
   It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangement of parts described and shown. 
   For example, it is foreseen that the switch assembly  1  of the present invention has numerous applications beyond the injection molding application discussed above and its use is not intended to be limited to such applications. Similarly it is foreseen that the mounting clip  8  can be utilized to mount devices other than the disclosed switch assembly to a wide variety of surfaces. However a preferred application of the clip  8  is to mount limit switches or the like on one of a stationary member and a moveable member, such as the ejector housing  5  and an ejector plate  173  of an injection mold, to determine the relative position of the moveable member relative to the stationary member. 
   It is also foreseen that the terminal contacts  24  and  25  could be mounted between the first and second spring ends  16  and  17  and facing the outward toward the first spring end  16  with the bridge contact  20  mounted on an inner face of the first glide  14  mounted on the first spring end  16 . In such an embodiment the application of a force to the middle portion  113  of the spring  13  to cause the spring  13  to bow advances the first spring end  16 , first glide  14  and bridge contact  20  away from the terminal contacts  24  and  25  a distance sufficient to draw the bridge contact  20  out of engagement with at least one of the terminal contacts  24  and  25  to change the condition of the switch from normally closed (on) to open (off). Release of the force, then allows the spring  13  to advance back to the resting position so as to allow the first spring end  16 , glide  14  and bridge contact  20  to advance toward and into contact with both terminal contacts  24  and  25  to change the switch condition back to closed. 
   It is foreseen that the first glide  14  could be formed from electrically conductive material such that the glide  14  itself, including an outer face  21 , functions as the bridge contact for completing an electrical connection between the first and second terminal contacts  24  and  25 . It is also foreseen that instead of having a glide  14  connected to the first end  16  of the spring  13 , the first end of the spring  13  could be utilized as the bridge contact  20 , for example, the first end  16  of the spring could be turned upward to form a foot (as shown in U.S. Pat. No. 5,446,252) to present a metallic surface for contacting and forming an electrical connection between the terminal contacts  24  and  25 . The flexible seal  145 , formed from an electrical insulating material, would prevent shorts of the switch assembly  1  through the spring  13  as long as the seal  145  does not tear or otherwise expose the spring  13 . 
   As used herein and in the claims, reference to the bridge contact being connected to the bowed spring or first end thereof is intended to include the alternative embodiments described above and any other embodiment in which the bridge contact is formed as part of the spring itself or formed separately and connected to the spring either directly or indirectly. Moreover, the terms connected to or connect are intended to include both direct and indirect connections (i.e. connection through intervening parts) unless clearly specified otherwise.