Abstract:
A thermal sensor incorporating an improved retention clip is disclosed herein. The improved retention clip is both easily fabricated from either sheet stock or wire stock and is designed to be easily and securely assembled to the sensor housing and provides a convenient easy to use retention system for attaching the sensor to a tubular or generally cylindrical conduit member. The retention clip includes a gently angled lead-in portion which aids in guiding the clip into the conduit with little force coupled with a more sharply angled retention portion that substantially increases the force required to dislodge the sensor once assembled. Additionally, the clips are designed to minimize contact surface engagement with the conduit so as to minimize crevice corrosion. Portions of the clips may be covered with a suitable material to further limit the possibility of localized corrosion as well as to insulate the clip from the conduit member while also resisting relative movement therebetween. An optional protector disc is also disclosed which serves to provide increased protection against damage to the sensor body.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates generally to thermally responsive controls and more particularly to such controls incorporating improved mounting brackets or clips which are utilized to retain such thermal sensors in intimate heat transfer relationship with tubular or cylindrical members such as fluid conduits and the like. 
     There exist a wide variety of applications in which it is necessary or desirable to attach sensors to generally cylindrically shaped members such as for example in attachment of thermal sensors to fluid flow conduits. In such applications, it is highly desirable that the bracket or clip utilized to secure the sensor be designed to enable easy installation of the sensor on the tubular member but yet provide a high resistance to dislodgment of the sensor. It is also highly desirable that such mounting clips be designed for easy and convenient assembly to the sensor during the manufacture thereof thus avoiding the need for additional assembly operations by the end user of the sensor. It is also important that the mounting clip be designed so as to minimize the possibility of crevice corrosion which could result in damage to the conduit to which it is secured or degradation of the clip itself thus impairing its retention abilities. Further, in some applications, it is desirable to insulate the mounting clip itself from the conduit as well as to inhibit relative movement therebetween. 
     Accordingly, the present invention provides a thermally responsive sensor having an improved sensor mounting arrangement which offers the desirable advantages and features noted above. More specifically, the present invention provides mounting clips which are designed to be easily and conveniently assembled to the sensor during the manufacture thereof so as to provide the end user thereof with an easy to use unitary sensor assembly. Further, the mounting clips of the present invention are designed to facilitate quick and easy attachment of the sensor assembly to the fluid conduit yet provide a strong resistance to dislodgment from the conduit once assembled thereto. In one embodiment, embossments are provided on portions of the mounting clip to minimize surface contact between the conduit and clip thus reducing heat transfer through the clip as well as inhibiting crevice corrosion. In another embodiment, the area of the clip contacting the conduit may include pads, a coating or plated material to inhibit corrosion and/or resist relative movement of the sensor with respect to the clip. An optional protective cover is also disclosed which may be secured to the cap portion of the sensor to protect it from possible damage during shipment and/or assembly to the conduit. In yet another embodiment, the mounting clip is in the form of an open ended wire loop which includes leg portions adapted to be received in integrally molded channels provided on the sensor housing to enable easy and secure attachment of the clip to the sensor housing. 
     In each of these embodiments, the mounting clip of the present invention is specifically designed to facilitate easy fabrication thereof at very low cost while providing a secure means by which the sensor may be secured to a fluid conduit. 
     Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a sensor incorporating a mounting clip secured thereto shown in operative relationship to a tubular member, all in accordance with the present invention; 
     FIG. 2 is a section view of the sensor assembly of FIG. 1, the section being taken along a diametrical plane extending through the longitudinal center of the mounting clip; 
     FIG. 2 a  is a section view showing the arrangement of the switch contacts within the switch case, the section being taken along line  2   a — 2   a  of FIG. 2; 
     FIG. 2 b  is a section view also showing the arrangements for the switch contacts within the switch case, the section being taken along lines  2   b — 2   b  of FIG. 2 a;    
     FIG. 3 is an elevational view of the sensor of FIG. 1 as seen looking in the direction of arrow  3  in FIG. 1; 
     FIG. 4 is an elevational view of the sensor housing of FIG. 1, all in accordance with the present invention; 
     FIG. 5 is a longitudinal section view of the mounting clip shown in FIG. 1; 
     FIG. 6 is an elevational view of the mounting clip of FIG. 5; 
     FIG. 7 is a fragmentary perspective view showing a modified clip receiving pocket; 
     FIG. 8 is a section view similar to that of FIG. 2 but showing an alternative embodiment of the sensor, all in accordance with the present invention; 
     FIG. 9 is a longitudinal section view of the mounting clip of FIG. 8; 
     FIG. 10 is an elevational view of the mounting clip shown in FIG. 9; 
     FIG. 11 is an elevational view of the sensor housing forming a part of the embodiment shown in FIG. 8; 
     FIG. 12 is a section view of the sensor housing of FIG. 11, the section being taken along lines  12 — 12  thereof; 
     FIG. 13 is a view similar to that of FIG. 2 but showing a cup protector disc secured to the sensor cup, all in accordance with the present invention; 
     FIG. 14 is a plan view of the cup protector shown in FIG. 13; 
     FIGS. 15 and 16 are elevational and plan views respectively of an alternative cup protector in accordance with the present invention; 
     FIGS. 17 and 18 are elevational and plan views respectively of a further alternative cup protector in accordance with the present invention; 
     FIG. 19 is a plan view of yet another alternative cup protector in accordance with the present invention; 
     FIGS. 20 and 21 are section views of the protector disc of FIG. 19, the sections being taken along lines  20 — 20  and  21 — 21  respectively; 
     FIG. 22 is a section view similar to that of FIG. 2 but showing a mounting clip incorporating a snap-in saddle in accordance with the present invention; 
     FIGS. 23 and 24 are elevational and plan views respectively of the snap-in saddle of FIG. 22; 
     FIG. 25 is a top view of the clip shown in FIG. 22; 
     FIG. 26 is a fragmentary longitudinal section view showing an alternative embodiment of the mounting clip shown in FIG. 22, in accordance with the present invention; 
     FIG. 27 is a plan view of the clip of FIG. 26; 
     FIG. 28 is a view similar to that of FIG. 26 but showing an alternative embodiment in accordance with the present invention; 
     FIG. 29 is a view similar to that of FIG. 1 but showing a sensor having a modified mounting clip in accordance with the present invention; 
     FIGS. 30 and 31 are an end view and side view respectively of the sensor housing shown in FIG. 29; 
     FIG. 32 is an elevational view of the mounting clip shown in FIG. 29; 
     FIG. 33 is an end view of a further embodiment of the present invention; and 
     FIG. 34 is an elevational view of the embodiment of FIG.  33 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and more specifically to FIG. 1, there is shown a sensor  10  incorporating a housing  12  to which is secured a mounting bracket or clip  14 . Sensor  10  is in the form of a thermally responsive switch and includes a metal cup  16  protruding slightly from one end of housing  12  which is to be positioned in thermally conductive relationship with a conduit  18 , the exterior temperature of which is to be sensed. For example, conduit  18  may be a fluid conducting conduit utilized for conducting refrigerant in a refrigeration or air conditioning system although it should be noted that the present invention is well suited for use in attaching a wide variety of sensors to cylindrical or generally cylindrical members. 
     As best seen with reference to FIG. 2, sensor  10  includes a pair of electrical leads  20 ,  22  extending into housing  12  and connected to a pair of laterally spaced terminals  24 ,  25  which are riveted by two rivets  26 ,  27  to a switch case  28 . A flexible conductive arm member  29  has one end secured to switch case  28  by rivet  27  and includes a diametrically extending spring arm portion  30  having a contact  31  provided at the movable free end thereof. A second conductive arm member  32  has one end secured to switch case  28  by rivet  26  and includes an arm portion  33  having a contact  34  provided thereon which is positioned in overlying engaging relationship with contact  31  provided on arm portion  30 . An actuator rod  35  is in turn movably supported by an irregular generally disc shaped member  36  which is seated within cup member  16 . A bimetal disc member  38  is disposed within a cavity defined between the end of cup member  16  and disc member  36  and has a downwardly facing concave surface against which actuator  34  is biased by conductive member  29 . As noted above, when bimetal disc member  38  is in a condition with the concave surface facing downwardly as shown in FIG. 2, spring arm portion  30  will serve to support actuator  35  in engagement therewith and contacts  31  and  34  will be in electrically conductive engaging relationship. However, when bimetal disc member  38  snaps to a concave upwardly facing shape in response to a sensed temperature above a predetermined temperature, it will bias actuating rod  35  downwardly (as seen in FIG. 2) thereby moving spring arm portion  30  and contact  31  away from and out of engagement with contact  34 . Switch case  28  and disc shaped member  36  are crimped within cup member  16  and this assembly is seated with the hollow interior of housing  12  which interior is thereafter filled with a suitable non-conductive potting material  43 . 
     While sensor  10  as described above is in the form of a normally closed switch which opens in response to a sensed temperature in excess of (i.e., above or possibly below) a predetermined temperature, it may also take other forms such as for example a normally opened switch. Further, sensor  10  may be in the form of a device for sensing some other parameter associated with a tubular member. 
     Housing  12  is preferably formed from a suitable polymeric material and includes an integrally formed mounting clip retaining slot pocket  44  provided on a sidewall portion thereof. Slot  44  is defined by a generally planar outer wall portion  45  from which a pair of generally parallel radially outwardly extending circumferentially spaced wall portions  46  and  48  project which wall portions extend substantially the entire length of housing  12 . Wall portions  46  and  48  are spaced apart a distance slightly greater than the width of clip  14 . A wall portion  50  is integrally formed with and extends between respective walls  46  and  48  to thereby define slot  44 . Preferably, wall portion  50  will have a length slightly less than half the length of sidewalls  46  and  48 . Additionally, a generally rectangular shaped protrusion  56  is integrally formed on the sidewall  45  of housing  12 , being substantially centered between walls  46  and  48  and extending downwardly from approximately the lower edge of wall portion  50 . The upper edges of walls  45 ,  46 ,  48  and  50  are each provided with a beveled surface  58 ,  60 ,  62 , and  64  respectively to facilitate insertion of clip  14 . 
     With reference to FIG. 5, clip  14  is preferably formed from a single piece of suitably resilient metal such as stainless steel and comprises an elongated strip of a generally rectangular shape. Clip  14  includes a generally flat leading free end portion  68  which is formed at an acute included angle A relative to a plane  69  defined by the upper surface of cup  16  and serves to facilitate assembly of sensor  10  to the cylindrical member or fluid conduit. A second generally flat portion  70  is formed at an included angle of approximately 90° to free end portion  68  and is interconnected therewith by a relatively tightly radiused portion  74 . A third generally planar portion  76  extends at an included angle of approximately 90° from portion  70  being interconnected thereto by a relatively large radiused portion  78 . Extending from portion  76  is a further planar section  80  which is angled so as to extend substantially perpendicular to plane  69  defined by the top surface of cup  16  when clip  14  is assembled to housing  12 . An offset portion  84  is provided being connected to portion  80  and a next adjacent substantially planar portion  86  by included wall portions  88  and  90 . Planar portion  86  is angled slightly relative to a plane defined by portion  80  and includes a generally rectangular shaped opening  92  therein which, as best seen with reference to FIG. 3, has a width and length slightly greater than that of protrusion  56 . The lower end portion  94  of clip  14  is angled outwardly slightly from the plane defined by portion  86  so as to provide a guide surface for guiding the clip over protrusion  56  during assembly. Additionally, the corners of portion  94  are preferably trimmed to aid in guiding clip  14  into slot  44  during assembly. 
     Referring again to FIGS. 5 and 6, portions  70  and  76  are each provided with a pair of laterally spaced longitudinally extending embossed ribs  96 ,  98 , and  100 ,  102  respectively. Ribs  96 ,  98 ,  100 ,  102  are positioned and have a length such that they will provide the sole bearing surface of engagement with conduit  18  when sensor is assembled thereto. These ribs serve to minimize the surface contact between clip  14  and conduit  18  so as to reduce the possibility of crevice corrosion as well as to reduce heat transfer to the clip itself. 
     As shown in FIG. 2, as clip  14  is assembled within slot  44  of housing  12 , angle end portion  94  will engage the upper edge of protrusion  56  thus guiding portion  86  up and over same until protrusion  56  is received within opening  92 . Once fully assembled, protrusion  56  will provide a mechanical interlock with clip  14  to retain housing  12  and clip  14  in assembled relationship. Additionally, offset portion  84  will bear against wall  50  with the angulation of portion  86  providing a spring action to maintain this engagement as well as to maintain protrusion  56  seated within opening  92 . 
     When sensor  10  is assembled to conduit  18 , embossments  96 ,  98 ,  100 ,  102  will engage conduit  18  thereby urging and maintaining it in heat transfer engagement with the outer surface of cup  16  thus enabling sensor  10  to monitor the temperature thereof. Preferably, clip  14  will be designed to maintain at least a 5 pound gripping force on conduit  18  through the cantilevered support arrangement provided by the engagement of offset portion  84  with wall  50  and the engagement of portion  86  with surface  45  of housing  12 . It should also be noted that clip  14  will preferably have a width approximately equal to the diameter of cup  16  and because it is positioned in overlying relationship thereto will offer some protection against damage to cup  16  during shipping, handling and installation of sensor  10 . Additionally, the relatively small angulation of free end  68  with respect to plane  69  defined by the outer surface of cup  16  will facilitate easy assembly of sensor  10  to conduit  18  whereas the relatively large angulation of portion  70  relative to this same plane will render removal of sensor  10  from conduit  18  substantially more difficult thus greatly reducing the potential for accidental dislodgment of the sensor. Additionally, the provision of embossments  96 ,  98 ,  100  and  102  serve to concentrate the retention force exerted by clip  14  along  4  point or line contacts with the surface of conduit  18  thus reducing the possibility of slippage therebetween. 
     A modified clip receiving slot  47  is shown on housing  49  in FIG. 7 in which wall portion  50  of slot  44  is replaced by a pair of outer wall sections  51  and  53  integrally formed with and extending toward each other from respective circumferentially spaced wall portions  55  and  57 . In all other respects, clip receiving retention slot  47  is substantially identical to clip receiving slot  44  described above. 
     Referring now to FIGS. 8-12, another embodiment of the present invention is shown being generally indicated by reference number  104 . Sensor  104  is substantially identical to sensor  10  with the exception of the clip receiving pocket  44  and portions  80 ,  84 ,  86 ,  88 ,  90  and  94  of the clip  14 . Portions of sensor  104  that are substantially identical to corresponding portions of sensor  10  are indicated by the same reference numbers primed. 
     In this embodiment, retention clip  106  includes an elongated generally planar portion  108  extending from portion  76 ′ and a substantially planar return bend portion  110  connected to the lower end of portion  108  by a generously radiused portion  112 . As best seen with reference to FIGS. 9 and 10 radiused portion  112  and planar portion  108  include an elongated slot or opening  114  substantially centered laterally and extending longitudinally through a major portion of the length of portion  108 . 
     The clip receiving pocket provided on housing  12 ′ includes substantially planar circumferentially extending outer wall portion  116  extending between a pair of elongated radially outwardly projecting circumferentially spaced sidewalls  118  and  120 . An outer wall portion  122  extends between and interconnects the outer ends of wall portions  118  and  120  and has a length slightly more than half the length of sidewalls  118  and  120 . Outer wall  122  has a reduced thickness lower portion that defines a recess  124  which is adapted to receive portion  110  of clip  106 . A small notch  126  is provided in end surface  128  of recess  124  into which the terminal end of clip  106  is received with notch  126  serving to provide a mechanical interlock to retain clip  106  in position therein. 
     Outer wall portion  116  also includes an elongated protrusion  130  generally centered thereon which is adapted to be received in slot  114  and serve to guide clip  106  into the clip receiving pocket as well as to limit its movement into same. Thus, when assembled, protrusion  130  together with recess  124  will serve to limit relative longitudinal movement of clip  116  with respect to housing  14 ′ whereas sidewalls  118 ,  120  will prevent relative angular rotational movement therebetween. 
     In all other respects, sensor  104  will provide substantially the same benefits and operate in substantially the same manner as set forth above with respect to sensor  10 . 
     In some applications, it may be desirable to provide additional protection against damage or denting of outer cup  16 . FIGS. 13 through 21 disclose several embodiments of protectors that may be utilized with any of the sensors disclosed herein to accommodate this objective. 
     With reference to FIGS. 13 and 14, a first embodiment of a protector is disclosed which protector is in the form of a circular disc  134  which is suitably secured to the outer surface  136  of cup  16  such as by welding, brazing, soldering or a suitable adhesive. Preferably, protector disc  134  will be fabricated from a highly thermally conductive material such as aluminum for example so as to minimize the effect of the increase in the length of the thermal transfer path to bimetal disc  38 . 
     FIGS. 15 and 16 show an alternative embodiment of a protector disc  138 . In this embodiment, disc  138  has a generally diametrically extending open V-shaped channel formed therein by deforming a slightly oval blank along chords thereof extending substantially perpendicular to the major axis of the blank to form two upwardly inclined side walls  140 ,  142  thereby creating two legs  144 ,  146  of the open V and a relatively narrow flat  148  at the juncture thereof. The V-shaped protector  138  is secured to the cup in the same manner as described above with respect to protector  134  and offers the advantages of a cradle to aid in properly positioning the sensor on the conduit as well as two lines of contact with the conduit for improved heat transfer. 
     A further variation of protector disc  138  is illustrated in FIGS. 17 and 18 being indicated by reference number  150 . Protector disc  150  comprises a flat disc in which a diametrically extending V-shaped notch  152  is provided. This embodiment offers the advantages of full heat transfer surface contact with the top surface of cup  16  while also incorporating the locating and heat transfer advantages of protector disc  138 . 
     Another embodiment of a protector disc is shown at  154  in FIGS. 19-21. This embodiment is similar to that of disc  150  but is trimmed along chords  156 ,  158  on opposite sides of the V groove  160 . Additionally, a diametrical slot  162  is provided at the apex of the V groove and circumferentially extending depending flanges  164 ,  166  are provided at opposite ends of the groove. Depending flanges  164 ,  166  assist in positioning disc  154  with respect to cup  16  as it is being secured thereto whereas slot  162  and the trimmed chords aid in more rapid cooling of the bimetal disc  38  in response to a drop in the temperature of conduit  18  being sensed. 
     It should be noted that each of these protector discs will preferably be fabricated from a material having excellent heat transfer capabilities such as for example aluminum. Further, the protector discs may be secured to cup  16  in any suitable manner such as by welding, brazing or soldering or even by a suitable adhesive. It should also be noted that preferably the V groove will be structured so as to avoid excessively increasing the distance between the conduit and cup  16  while still being adapted to accommodate a relatively wide range of conduit diameters. Alternatively, any of the protector discs could be fabricated with a radiused groove in place of the V groove and the radius could also be selected to match the radius of the conduit thereby providing even greater heat transfer surface contact between the sensor and the conduit. 
     In some applications, it may be desirable to avoid even the limited direct contact of the clip with the conduit as is required by the embossments in the clip embodiments described above. Accordingly, such an alternative embodiment is illustrated in FIGS. 22-25 being indicated generally at  168 . 
     Sensor  168  is substantially identical to sensor  10  described above except for the below noted modifications to the retaining clip  170  incorporated therein. Accordingly, corresponding portions thereof are indicated by the same reference numbers double primed. 
     Retaining clip  170  has a pair of openings  172 ,  174  centrally located on portions  70 ″ and  76 ″ thereof in place of embossments  96 ,  98 ,  100 ,  102 . A saddle member  176  is provided which includes a pair of appropriately positioned projections  178  and  179  which are designed to be received within respective openings  172 ,  174  to secure saddle member to clip  170 . 
     As best seen with reference to FIGS. 23 and 24, saddle member  176  is generally rectangular in shape and includes laterally extending relatively thick pad portions  180  and  182  adjacent opposite ends thereof and an interconnecting relatively thin web portion  184 . Web portion  184  is positioned relative to thickened portions  180 ,  182  such that the backside of saddle member  176  is substantially planar with the exception of protrusions  178 ,  179 . Further, protrusion  178  is generally centered on thickened portion  180  whereas protrusion  179  is generally centered on thickened portion  182 . Each of the protrusions  178  and  179  includes an enlarged diameter head portion  186 ,  188  respectively which operate to overengage the outwardly facing surface of clip  170  to retain saddle member  176  in assembled relationship thereto. 
     Saddle member  176  is preferably integrally molded from a suitable polymeric material which will provide a reasonable degree of resiliency as well as relatively high frictional engagement with conduit  18  so as to both insulate clip against vibrations as well as to resist relative sliding movement between the sensor and conduit. Additionally, saddle member  176  also serves to reduce heat transfer to the surrounding environment via clip  170 . Preferably saddle member  176  will have a width substantially equal to or slightly less than the width of clip  170  and a length sufficient such that thickened portions  180  and  182  will be suitably positioned for engagement with conduit  18  at spaced locations when sensor  168  is assembled thereto. Because saddle member  176  also serves to eliminate any metal to metal contact between clip  170  and the conduit to which it is mounted, it effectively eliminates any concern regarding crevice corrosion. 
     As an alternative to saddle member  176 , the conduit engaging section of portions  70 ′″ and  76 ′″ of clip  190  may be insulated by use of a heat shrink tubing or a suitable polymeric coating  192  applied as is shown in FIGS. 26 and 27. As the tubing or polymeric coating will completely surround the concerned sections of portions  70 ′″ and  76 ′″, openings  172  and  174  may be deleted from clip  190  if desired. 
     FIG. 28 illustrates a further alternative embodiment in which concerned sections of portions  70 ″″ and  76 ″″ of clip  194  are coated with a suitable paint or plated with a suitable material  196  if desired. 
     It should be noted that the saddle member, heat shrink tubing, polymeric coatings or plating concepts disclosed above may be applied to any of the retention clips disclosed herein. 
     Referring now to FIG. 29, there is shown a sensor  198  having a housing  200  to which is secured a wire retention clip  202 . Housing  200  has disposed therein a sensor assembly substantially identical to that disclosed within housing  12  with cup  204  projecting outwardly from the upper end thereof. 
     As best seen with reference to FIGS. 30 and 31, housing  200  is generally cylindrical in shape and includes a pair of elongated substantially parallel circumferentially spaced projections  206 ,  208  extending outwardly from sidewall  210  thereof. Each of projections  206  and  208  includes facing sidewalls  212  and  214  within which outwardly opening elongated grooves  216 ,  218  are formed. Respective grooves  216 ,  218  open outwardly from the upper end of respective projections  206 ,  208  and extend downwardly to perpendicularly oppositely extending openings  220 ,  222  positioned adjacent to but spaced from the lower ends of projections  206 ,  208 . Openings  220  and  222  each open outwardly through respective outer walls  224 ,  226  of projections  206 ,  208 . 
     As shown in FIGS. 29 and 32, wire retention clip  202  is formed from a single elongated length of wire formed into an irregular generally U-shaped configuration including a pair of substantially identically shaped spaced legs  228 ,  230  and an outer interconnecting portion  232 . As legs  228  and  230  are substantially mirror images of each other, only leg  228  will be described in detail, it being understood that leg  230  incorporates substantially identical portions. 
     Beginning from interconnecting portion  232 , leg  228  includes a first upwardly angled portion  234  which forms an acute included angle relative to a plane defined by the upper surface of cup  204 . A second relatively straight section  236  is connected to one end of section  234  by a relatively tightly radiused portion and extends upwardly therefrom at a second acute angle relative to a plane defined by the upper surface of cup  204 . Preferably, section  234  will be at a lesser angle relative to the above referenced plane than section  236  thereby affording a lower required installation force and high removal force for assembling or disassembling sensor  198  from a conduit. A generously radiused portion  238  interconnects section  236  to a third relatively straight section  240 . Preferably, the radius of portion  238  will be somewhat less than the radius of the conduit to which sensor  198  is to be assembled so as to provide for point contacts with the conduit only by respective sections  236  and  240  so as to minimize the potential for crevice corrosion. 
     A fourth relatively straight section  242  extends from section  240  and is angled with respect thereto such that it will extend substantially perpendicular to the plane defined by the upper surface of cup  204 . The terminal ends  244 ,  246  of wire clip  202  at the lower ends of respective legs  228  and  230  are each bent outwardly in opposite directions at an angle of substantially 90° to portion  242  thereof. 
     In order to assemble wire clip  202  to housing  200 , portions  242  of respective legs  228  and  230  are squeezed together slightly and ends  244 ,  246  inserted in respective openings  220  and  222  provided in housing  200  while leg portions  242  are positioned and received within respective grooves  216  and  218 . The spring action between respective legs  228  and  230  will operate to retain wire clip  202  in assembled relationship with housing  200 . If desired, grooves  216 ,  218  may be sized so as to provide a snap fit with leg portions  242 . The function and operation of wire clip  202  will otherwise be substantially identical to that described above with reference to clips  14  and  106  and as noted above clip  202  may be utilized in conjunction with any of the protective discs disclosed above and may also incorporate a suitable coating or plating as described above or may have portions of respective legs  228 ,  230  encased in a suitable tubing also as disclosed above. 
     Referring now to FIGS. 33 and 34, another embodiment of a sensor  248  is shown incorporating another modified wire retention clip  250 . In this embodiment, housing  252  is provided with an annular groove  254  adjacent its upper end for mounting of wire retention clip  250 . 
     Wire retention clip  250  is also formed from an elongated single length of a suitable wire and has an irregular generally W-shaped form (when viewed in plan) which is generally symmetrical about a diametric plane extending parallel to the longitudinal axis of body  252 . Accordingly, only one half of wire retention clip  250  will be described, it being understood that the other half will be the mirror image of the half described. 
     Wire clip  250  includes a relatively straight free end portion  256  extending to the left as shown in FIG. 33 to an arcuate section  258  which is designed to be received in annular groove  254 . Preferably, arcuate portion  258  will have a radius of curvature substantially equal to the radius of housing  252  at the inner base of groove  254 . Extending leftward (as shown) from arcuate portion  258  is a second generally straight portion  260  which connects to a generally U-shaped return bend portion  262 . A third generally straight portion  264  extends from U-shaped portion  262  and extends upwardly into overlying relationship with respect to cup  266 . A generously radiused portion  268  continues from straight portion  264  and is shaped to generally conform to the curvature of a conduit  272  to which sensor  248  is to be secured. Alternatively, portion  268  may have a radius less than that of conduit  268  so as to limit the surface contact therebetween. From portion  268  a generally straight portion  272  extends outwardly and in generally upwardly angled relationship to a plane defined by the upper surface of cup  266 . Portion  270  also serves to interconnect the two halves of wire clips  250  at the midpoint thereof. 
     In order to assemble wire clip  250  to housing  252 , respective end portions  256  are flexed apart slightly so as to allow arcuate portions  258  to move into annular groove  254 . Thereafter, the spring action of clip  250  will serve to retain portion  258  in assembled relationship with groove  254  of housing  250 . The remaining function and operation of wire retention clip  250  will be substantially the same as described above. 
     While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to provide the advantages and features above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.