Abstract:
A multifunction adapter for use in a motion sensor module holds a lens at the front of the adapter in a predetermined position and distance relative to a sensor mounted on a circuit board, and uses positioning projections at the rear of the adapter to set a predetermined distance of the adapter from the sensor and the circuit board. The adapter can be adjusted to set the focal point of the lens at an optimized position for the sensor. Additionally, a cover that shrouds the sensor is present on the rear side of the adapter for reducing or eliminating air flowing across and around the sensor. When the sensor is a passive infrared device, the reduction in air flowing around and across the sensor reduces the number of false signals.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to an adapter for positioning a lens. More specifically, the invention relates to an adapter in a motion sensor module for positioning a lens to a predetermined position relative to a sensor attached to a circuit board, and for shielding the sensor from air currents. The adapter is funnel-shaped, holds a lens on a front side, and has a shroud on the opposite back side for shielding the sensor from air currents. The shroud also has pins that are inserted through a circuit board for maintaining the adapter in a predetermined position, and each pin can have a stop that determines the distance between the lens and the sensor. 
     BACKGROUND OF THE INVENTION 
     Passive infrared sensors are commonly used in motion detectors to determine the presence or absence of individuals, generally determining if someone enters a zone of coverage. These detectors may be connected to security systems, and thereby alerting others of intrusion into the zone, or they may be connected to light switches, and may be used to turn lights on when a person is present in the zone, or deactivate the lights when a person is no longer present in the zone. 
     These motion detectors generally consist of a housing, and have a passive infrared sensor attached to a printed circuit board contained in the housing. A lens is positioned in front of the sensor, the lens focusing the infrared profile of a person as it moves across the field of view. The sensor is positioned near the focal point of the lens. A lens retainer allows the lens to be fixed in a predetermined position and assists in reflecting infrared towards the sensor. 
     However, tolerance buildup during manufacture can alter the predetermined lens position. Additionally, air currents passing over the sensor can result in false sensor readings. Consequently, there is a need for an adapter that accurately positions the lens to a predetermined focal point relative to the sensor, and a shroud for reducing or eliminating stay air currents from around the sensor. 
     Some examples of passive infrared motion detectors are U.S. Pat. No. 5,764,146 to Baldwin et al.; U.S. Pat. No. 4,672,206 to Suzuki et al.; U.S. Pat. No. 5,442,178 to Baldwin; U.S. Pat. No. 5,626,417 to McCavit; U.S. Pat. No. 5,772,326 to Batko et al.; U.S. Pat. No. 5,790,040 to Kreier et al; and U.S. Pat. No. 5,026,990 to Marman et al, the disclosures of which are incorporated herein by reference. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to provide an improved adapter for positioning a lens. 
     Another object of the present invention is to provide an improved adapter for positioning a lens having projections for positioning a lens a predetermined distance from a sensor. 
     The forgoing objects are basically attained by providing an adapter comprising a cover having a wall forming a hollow cavity and extending about the central axis; an extension coupled to and extending from the cover, the extension having a front side with a first opening and a back side with a second opening, the first opening being smaller than the second opening, the extension being attached to the cover at the back side with the second opening being aligned with the hollow cavity of the cover; and a plurality of projections coupled to the cover, each of the projections being spaced from each other and projecting from the cover in the direction of the central axis, opposite the extension. 
     The foregoing objects are also attained by providing a sensor assembly, comprising a circuit board; a sensor coupled to the circuit board; an adapter coupled to the circuit board and having a cover, an extension, and at least one projection, the cover having a wall extending around the sensor, the extension coupled to and extending from the cover and having a front side with a first opening and a back side with a second opening, the first opening being smaller than the second opening, the extension being attached to the cover at the back side with the second opening being aligned with the sensor, and the at least one projection coupled to the cover and attached directly to the circuit board. 
     The foregoing objects are also attained by providing a sensor assembly, having a circuit board; a sensor coupled to the circuit board, an adapter coupled to the circuit board; a lens coupled to the adapter; and means for accurately positioning the lens relative to the sensor and for prohibiting air currents from interfering with the functioning of the sensor. 
     Other advantages and salient features of the invention will become apparent from the following detailed description, which, when taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring to the drawings which form a part of the original disclosure: 
     FIG. 1 is a side elevation view of a sensor module assembly showing a funnel, a circuit board and a sensor, constructed in accordance with the present invention; 
     FIG. 2 is an exploded, partial, side, rear, top perspective view of the sensor module assembly in FIG. 1 with the housing in an open position; 
     FIG. 3 is a front, side, top perspective view of the adapter in accordance with the present invention; 
     FIG. 4 is a rear, side, bottom perspective view of the adapter in FIG. 3; 
     FIG. 5 is a rear view of the adapter attached to the circuit board and constructed in accordance with the present invention; 
     FIG. 6 is a cross-sectional side view of the adapter attached to the circuit board taken along line  6 — 6  in FIG. 5, and 
     FIG. 7 is a close-up cross-sectional view of the adapter attached to the circuit board taken along line  7 — 7  in FIG. 5 illustrating the first portion of a projection going through the circuit board and a second portion of the projection limiting the passthrough of the first portion. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1-4 depict a sensor module  10  according to this invention. The sensor module  10  comprises a rear housing member  12  which can be mounted to a mounting surface such as a wall of a house as known in the art, and a front housing member  14  which attaches to the rear housing member  12 . A sensor  16  is mounted on a circuit board  18  within the sensor module  10  as generally known in the art. The sensor  16  can be any parameter sensor known in the art, such as passive infrared (PIR) sensor, ultrasonic sensor, temperature sensor, light sensor, relative humidity sensor, a sensor for the detection of carbon dioxide or other gasses or ions, an audio sensor, or any other passive or active sensor that can be used to detect movement or change from the nominal environment. For example, the sensor can detect changes in vibration or sound, temperature, visual, ionic and moisture conditions. In the preferred embodiment the sensor  16  is a PIR sensor. 
     A lens  20  is positioned in front of and in the field of view of the PIR sensor  16  for focusing infrared radiation. When the PIR sensor is used, the lens  20  is preferably a fresnel lens, however, the lens  20  can vary with the type of sensor  16  used. When a PIR sensor is used, the lens focuses IR in the lens field of view to a focal point at the sensor. An adapter  22  is provided for holding the lens  20  securely in place using lens clips  24  to secure the ends of the lens  20 . Additionally, the adapter  22  optimally positions the lens  20  relative to the sensor  16  so that the focal point of the lens  20  is optimized for the sensor  16 . The front housing member  14  also includes a window  26 , in which the lens  20  is positioned and through which the sensor  16  can view the ambient environment. Except for adapter  22  and its connection to circuit board  18 , the structure and functioning of sensor module  10  is generally known in the art. 
     The adapter  22  has a cover or shroud assembly  27  that shrouds the sensor  16 , and a funnel portion  48 . The shroud assembly  27  has a shroud  28  and projections  30 . Shroud  28  is substantially cylindrical in shape, with one end attached to the funnel portion  48  and another, opposite end extending out from the funnel portion  48  towards the location of the sensor  16 . The shroud  28  can be fabricated from the same polymeric material as the adapter  22  and can be an integrally formed to be one-piece with the rest of the adapter  22 . The size of the shroud  28  is predetermined to shield the sensor  16  from air currents and extends far enough down the sides of the sensor  16  towards circuit board  18  to shield the sensor  16  from the air currents. The shroud  28  can extend down and contact the board  18  around 360° of the sensor  16 , thus, completely cutting off any possibility of air currents affecting sensor  16  from the sides of sensor  16 . As illustrated, the shroud  28  is spaced from circuit board  18 , although the shroud  28  is sufficiently covering the sensor to provide sufficient protection from air currents from the side. 
     Projections  30  extend from the shroud bottom  29  of the shroud  28  for insertion through the circuit board  18 . These projections position the shroud  28 , and therefore the adapter  22  relative to the sensor  16  and circuit board  18 . Projections  30  also allow for a gap between the shroud  28  and circuit board  18 . The amount of gap can vary from allowing the end of shroud  28  to be flush with circuit board  18  and completely enclose the sides of sensor  16  to the gap being predetermined separation between the end of the shroud  28  and circuit board  18 . 
     As seen in FIGS. 5-7, projections  30 , attached to the shroud bottom  29 , extend through the circuit board  18 , while maintaining the shroud  28  a predetermined distance from circuit board surface  82 . Optionally, the shroud bottom  29  can contact the surface  82  of the circuit board  18 . 
     As seen in FIG. 7, the first portion  32  of a projection  30  extends through the circuit board  18 . The second portion  34  limits the passing through of the projection  30  through the circuit board  18 , while the first portion  32  passes through the circuit board  18  unhindered. Second portion  34  has a substantially flat portion  35 , which abuts the substantially flat upper surface  82  of board  18 . 
     Four projections  30 , each having a first portion  32  and a second portion  34 , position the adapter  22 , and therefore the lens  20 , a predetermined distance from the sensor  16 . Although four projections  30  are shown, any number can be used. The first portion  32  of the projections  30  are inserted through projection holes  36  in the circuit board  18 . The projection holes  36  allow for proper positioning of the adapter  22  for stability and optimum positioning of the adapter  22  with respect to the sensor  16 . The second portion  34  limits the distance the projections  30  can travel through the circuit board  18 . Thus, the second portion  34  acts as a stop for the projections  30  since it abuts the surface of the circuit board  18  and does not fit in hole  36 . The second portions  34  are substantially flush with the surface of the circuit board  18  when adapter  22  is fully coupled to circuit board  18 . The distance each first portion  32  is allowed to pass through their respective projection hole  36  in the circuit board  18  determines the length of the second portion  34 . In this manner, a sensor module  10  can be designed whereby the adapter  22  is fabricated to place the lens  20  at a pre-focused location relative to the sensor  16 . Mounting screws  38  attach the adapter  22  to the circuit board  18  and the front housing  14 , and keep the projections  30  in holes  36 . 
     By trimming the second portion  34 , the distance of the lens  20  from the sensor  16  can be adjusted. The second portion  34  can be trimmed manually by cutting or otherwise removing a segment after it is fabricated. Alternatively, the manufacturing mold can be adjusted or a new mold fabricated as required. The first portion  32  is preferably integral and one-piece with the entire projection  30 . Alternatively, a first portion  32  having a predetermined length can be attached to the projections  30 . 
     As seen in FIGS. 3 and 4, the adapter  22  has an extension or funnel-shaped portion  48 , the wider funnel opening occurring on the funnel front side  50  and the smaller funnel opening occurring on the funnel rear side  52 . The funnel-shaped portion  48  permits maximum viewing by the sensor  16  of the ambient environment while blocking the flow of air. The funnel-shaped portion  48  can have multiple flat surfaces, multiple curved surfaces, a single curved surface, or a combination of flat and curved surfaces in order to tailor the range of view of the sensor  16  through the window  26  in the front housing  14 . FIGS. 3 and 4 show the funnel-shaped portion  48  having four flat walls  54 . When the sensor module  10  is assembled, the funnel front side  50  is covered by the lens  20 . The funnel-shaped portion  48 , indeed the entire adapter  22  including shroud  28  and its projections  30 , can be integrally fabricated from a single piece of plastic using, for example, injection molding techniques. The adapter  22  and the funnel-shaped portion  48  can also be fabricated from other materials using techniques known in the art, and can be formed from many pieces fit together. 
     The front of the adapter  22  is generally curved to maximize the lateral viewing range of the lens  20  and the sensor  16 . Also at the front of the adapter  22  are a bottom shelf  56  and a top shelf  58 . Shelf  56  has an inside surface  60  facing the funnel-shaped portion  48 , and an opposite facing outer surface  62 . Shelf  58  has an inside surface  64  facing the funnel-shaped portion  48 , and an opposite facing outer surface  66 . These shelves  56 ,  58  also act to minimize air flow, as well as being a spacer between the top and bottom of the lens  20  and the funnel-shaped portion  48 . Attached to the outer surface  66  of the top shelf  58  is a header  68 . The header  68  has two rearward facing stabilizing pins  70  situated on opposite sides of the header  68 . When the adapter  22  is attached to the circuit board  18 , the stabilizing pins  70  are inserted into stabilizing pin holes  72 , thereby preventing the adapter from rocking or other movement relative to the circuit board  18 . 
     A first adapter mounting screw boss  74  is also located on the header  68 . A second adapter mounting screw boss  76  is attached to the outer surface  62  of the bottom shelf  56 . These bosses  74 ,  76  allow the mounting screws  38  to mount the adapter  22  between the circuit board  18  and the front housing  14 . 
     In FIG. 6, the first mounting screw boss  74  is flush with the circuit board  18 , while the second mounting screw boss  76  is not flush with the circuit board  18 . In this configuration of the preferred embodiment, a mounting screw  38  passes through a first mounting screw slot  78 , through the first mounting boss  74  and attaches to the front housing  14 . A second mounting screw slot  80  allows a user access to a second mounting screw  38 , which passes through the second mounting screw boss  76  and attaches to the front housing  14 . Alternatively, a longer second mounting screw can be used in order to pass the second mounting screw through the circuit board  18  as well as the second mounting screw boss  76 . The circuit board  18  is fixedly attached to the front housing  14  using mounting screws  38 . The rear housing  12  can be pivotally attached to the front housing  14  by a hinge. In this manner, the rear housing  12  can pivot about the hinge and enclose the circuit board  18 , the sensor  16 , and the adapter  22  within the front housing  14  and rear housing  12 . A tab  42 , located at the top of the front housing  14 , has a series of tab holes  44  which engage a pin  46  on the rear housing  12 . Engagement of the tab  42  with the pin  46  latches the front housing  14  with the rear housing  12 . 
     Alternatively, projection  30  can be attached to the first adapter mounting screw boss  74  to set the predetermined distance between the sensor  16  and the lens  20 . In this manner, the projection  30  limits how close the adapter  22  can get to the circuit board  18 , and therefore limiting the distance of the lens  20  to the sensor  16 . 
     Furthermore, the first adapter mounting screw boss  74  and mounting screw  38  can be replaced with a snap-fit alternative, that is, the circuit board  18  and the adapter  22  can be snap-fit together such that the adapter  22  is maintained a predetermined distance from the circuit board  18 . This results in the lens  20  being maintained a predetermined distance from the sensor  16 . 
     Other attachment means that are known in the art can be used between the adapter  22  and the circuit board  18  that will result in the lens  20  being a predetermined distance from the sensor  16 . 
     While only one advantageous embodiment has been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.