Patent Publication Number: US-6710325-B2

Title: Light curtain mounting system wherein housing and mounting bracket include curved surfaces

Description:
TECHNICAL FIELD 
     The present invention relates in general to light curtains which detect the intrusion of human limbs or other objects into a protective zone and, more particularly, the present invention relates to a system for mounting light curtains. 
     BACKGROUND ART 
     Light curtains are commonly employed in a variety of industrial applications to detect the intrusion of objects, such as hands or feet of personnel, into or around a prescribed area or zone of protection. Typical applications for light curtains include providing operator protection around machinery, such as punch presses, brakes, molding machines, automatic assembly equipment, coil winding machinery, robot operation, casting operations and the like. Light curtain systems employ invisible pulsed infrared light beams which project across a plane along the zone to be protected. Unintended blockage of the light beams by an object, such as the operator&#39;s hand, is sensed such that a control circuit triggers a warning signal, shuts the machinery down or otherwise safeguards the area. 
     In order to function properly, transmitters and receivers of the light curtain must be properly aligned. In the past, alignment of the transmitters and receivers of the light curtain was very difficult. Transmitters and receivers of the light curtain must be properly positioned and oriented with respect to a horizontal axis, a vertical axis and depth axis. In the past brackets have been used to mount the components of the light curtain. Some prior art brackets are rigidly attached to the light curtain, making it difficult to properly orient the light curtain compartment about a vertical axis. Shims have been used to orient light curtain transmitters and receivers in a vertical axis. 
     U.S. Pat. No. 5,198,661 to Anderson illustrates mounting brackets that allow for rotative movement of the light curtain components with respect to the brackets. The mounting brackets of the &#39;661 patent are longitudinally fixed to ends of the light curtain component components. 
     What is needed is a light curtain mounting system that allows for rotational and longitudinal movement of light curtain components with respect to the mounting bracket. Such a system greatly eases alignment of the light curtain transmitters and receivers by allowing longitudinal and rotational adjustment of the light curtain with respect to the brackets. 
     DISCLOSURE OF INVENTION 
     The present disclosure concerns an apparatus for mounting optics of a light curtain that allows for longitudinal and rotational adjustment between a light curtain optics housing and a mounting bracket. The light curtain optics housing includes a curved mounting surface that extends along a length of the housing. The mounting bracket is connected to the curved mounting surface, such that the mounting bracket can be longitudinally adjusted with respect to the housing. The mounting bracket includes a curved inner surface and an adjustment slot through the curved inner surface that allows rotational adjustment of the housing with respect to the mounting bracket. 
     In embodiments of the invention, the curved mounting surface of the light curtain is defined by an outer surface of a pair of opposing mounting flanges that extend from the housing. 
     A threaded fastener that passes through the adjustment slot in the bracket is used to connect the mounting bracket to the curved mounting surface. The mounting flanges define a fastener retaining channel that allows for longitudinal adjustment of the bracket with respect to the housing. The housing is connected to the bracket by a fastener constrained in the fastener retaining channel and a second fastener that engages the curved outer surface of the mounting bracket. The center of the radius of the curvature of the curved mounting surface of the light curtain optics housing is located at a central axis of the optics mounting housing. A washer is used that has a curved surface and a flat surface. The fastener used to connect the housing to the bracket engages the flat surface of the washer to bring the curved surface of the washer into engagement with the curved outer surface of the bracket to bring the bracket into tight engagement with the housing. 
     In one embodiment, an internally threaded fastener is constrained within the channel defined between the pair of opposed flanges of the light curtain housing. The washer having a curved surface and a flat surface engages the curved outer surface of the mounting bracket. An externally threaded fastener engages the flat surface of the washer, extends through the washer and the slot in the mounting bracket and engages the internally threaded fastener to connect the bracket to the housing. 
     A method of mounting and aligning optics of a light curtain is performed using the disclosed apparatus. The curved mounting surface of the light curtain housing is loosely connected to the curved mounting surface of the mounting bracket. The curved mounting surface of the light curtain housing is rotated with respect to the curved mounting surface of the mounting bracket to an aligned position. The connection between the housing and the mounting bracket is tightened. These and other advantages of the present invention will become apparent upon reading the following detailed description in view of the drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a top plan view of a system for mounting a light curtain; 
     FIG. 2 is a perspective view of a system for mounting a light curtain; 
     FIG. 3 is a plan view of a housing for light curtain optics; 
     FIG. 4, is a perspective view of mounting brackets of three embodiments attached to a oil light curtain; 
     FIG. 5A is a top elevational view of an aligned light curtain; 
     FIG. 5B is a perspective view of an aligned light curtain; 
     FIG. 6A is a perspective view of a mounting bracket of one embodiment; 
     FIG. 6B is a perspective view of a mounting bracket of one embodiment; and, 
     FIG. 6C is a perspective view of a mounting bracket of one embodiment. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The present disclosure is directed to a system  10  for mounting optics  12  of a light curtain  14 . The system  10  includes a light curtain optics housing  16  that includes curved mounting surface  18  and a mounting bracket  20  connected to the curved mounting surface  18 . The mounting bracket  20  includes a curved inner surface  22  and adjustment slots  24 . The curved inner surface  22  and the adjustment slot  24  allow rotational adjustment  26  of the housing  16  with respect to the mounting bracket  20  when the connection between the bracket  20  and the housing  16  is slightly loosened. 
     Referring to FIGS. 1 and 3, the illustrated housing includes a main body portion  30  and a pair of opposing mounting flanges  32 . The main body portion  30  is configured to receive optics  12  of the light curtain  14  and to hold the optics in position. The illustrated main body portion  30  includes a pair of slots  34 ,  34  that hold the optics in place. It should be readily apparent to those skilled in the art that any main body portion configuration may be used to hold the optics  12  in place. The configuration of the main body portion  30  shown in FIGS. 1 and 3 is for illustrative purposes only. 
     The pair of opposing mounting flanges  32  is used to connect the housing  16  to the mounting bracket  20 . In the illustrated embodiment, the opposing mounting flanges extend along the length L of the housing, allowing for longitudinal adjustment of the housing  16  with respect to brackets  20 . In the illustrated embodiment, two pairs of opposing mounting flanges  32  are included on the housing to facilitate use of mounting brackets on either side of the housing  16 . 
     The pair of opposing mounting flanges  32  define the curved mounting surface  18 . A channel  36  is defined between the pair of opposing mounting flanges  32 . The channel  36  includes a relatively wide cavity  38  adjacent to the main body portion  30  of the housing  16  and a narrower cavity  40  that extends from the wider cavity  38  through the surface  18 . Referring to FIG. 2, the illustrated channel  36  extends along substantially the entire length of the housing  16 . The illustrated housing  16  is extruded. It should be readily apparent to those skilled in the art that the housing  16  could be constructed by other methods, such as molding or die casting. 
     Referring to FIGS. 6A,  6 B and  6 C, the illustrated mounting brackets  20  include a curved inner surface  22  that mates with the curved mounting surface  18  of the housing  16 . The illustrated brackets  20  also include a curved outer surface  42 . The illustrated brackets  20  are made from a metal plate and is bent to form a curved flange  44  and a mounting flange  46 . The curved flange  44  includes the curved inner surface  22  and the curved outer surface  42 . Slots  24  are included in the curved flange  44 . The slots  24  in the curved flange  44  allow for rotation of the housing  16  with respect to the mounting bracket  20 . In the illustrated embodiment, the housing  16  rotates about a central axis A when the housing  16  is rotated with respect to the mounting bracket  20 . The central axis A coincides with the central axis of the curved mounting surface  18  of the housing  16  and the curved inner surface  22  of the mounting bracket. 
     Referring to FIG. 4, the mounting flange  46  may be bent at various angles to the curved flange  44  to accommodate mounting to different surfaces. The bracket configuration shown at the top of FIG. 4 facilitates mounting of housings of a light curtain  14  as depicted in FIGS. 5A and 5B. The bracket configuration shown in the middle of FIG. 4 accommodates mounting of a light curtain parallel to a wall or surface of a machine. In one embodiment, the bracket configuration shown in the middle of FIG. 4 is used to detect passage of an object into an opening, such as a door. The bracket configuration shown at the bottom of FIG. 4 is used to mount the housing of a light curtain in applications where spaced is limited. 
     In the illustrated embodiment, slots  50  are included in the mounting flange. The mounting flange  46  facilitates connection of the mounting bracket  20  to a wall or a surface of a machine that the light curtain is being mounted on. In the illustrated embodiment, a plurality of mounting brackets  20  are used to mount the housing  16 . 
     Referring to FIG. 1, the illustrated mounting bracket  20  is connected to the housing  16  with an internally threaded member  52  an externally threaded member  54  and a washer  56 . In the exemplary embodiment, the internally threaded member slidably fits within the channel  36 . In the exemplary embodiment, two internally threaded members are used that each include a threaded hole  58 . The two internally threaded members correspond to the slots  24  in the curved flange  44 . The illustrated internally threaded member  52  fits within the wide cavity  38  of the channel  36 . In the illustrated embodiment, the internally threaded member is a weld tab nut. It should be readily apparent to those skilled in the art that the configuration of the internally threaded member  52  may vary from the illustrated internally threaded member. For example, the internally threaded member  52  may include a wide portion that fits within the wide cavity  38  of the channel  36  and a narrower portion that extends into the narrow cavity  40 . In one embodiment, two internally threaded members are replaced with a single member having two spaced apart threaded holes corresponding to the slots  24  in the bracket  20 . It should also be readily apparent to those skilled in the art that the internally threaded member  52  could be replaced with a member that fits within the channel  36  that has one or more studs extending from it. 
     Referring to FIG. 1, the externally threaded member  54  has a threaded portion  64  and a head  66 . The threads of the threaded portion  64  correspond to the threads of the internally threaded member  52 . In the exemplary embodiment, two externally threaded members  54  are used, corresponding to two internally threaded members or the two spaced apart threaded holes of the internally threaded member. It should be readily apparent to those skilled in the art that an internally threaded member can be used in place of the externally threaded member when a member including a stud is slidably disposed in the channel  36 . In the illustrated embodiment, the externally threaded member  54  is a button head cap screw having a large bearing area and a small hex drive. 
     The illustrated washer  56  has a curved side  68  and a flat side  70 . The curved side  68  is concave and has a radius of curvature that corresponds to the radius of curvature of the curved outer surface  42  of the bracket  20 . The flat side  70  provides a surface for the externally threaded member  54  to flushly abut against and keeps the externally threaded member in alignment with the horizontal axis of the housing. In the illustrated embodiment, the washer  56  includes two holes  72  that are aligned with the threaded holes  58  of the internally threaded members and the slots  24  in the curved flange  44 . 
     The externally threaded members  54  are inserted through the holes  72  in the washer  56  through the slots  24  in the bracket  20  and are threaded into the internally threaded member  52  to constrain the mounting bracket  20  to the housing  16 . The slots  24  allow the housing  16  to be rotated with respect to the mounting bracket  20  to pivotally adjust the housing  16  about the axis A. Conventional fasteners are inserted through slots  50  in the flange  46  to mount the brackets  20  to a wall or surface of a machine. 
     Referring to FIG. 2, an XYZ axis, which may correspond to the horizontal axis, depth axis and vertical axis, respectively, of the light curtain is depicted near the top of the illustrated light curtain  14 . When mounting the light curtain  14 , linear adjustment along the X axis is allowed by the slots in the bracket  20 . If a mounting surface is not true, rotational adjustment about the X axis is allowed for by using shims between one or more of the brackets  20  and the wall  74 . The brackets  20  are mounted to a true wall  74  or shims are used if linear adjustment along the Y axis is required. Rotational adjustment about the Y axis is allowed for by the slots  50  in the mounting flange  46 . The internally threaded member(s)  52  can slide within the channel  36  in the housing  16 . The slidable movement of the internally threaded member(s)  52  in the channel  36  allows for linear adjustment along the Z axis. The slots  24  allow the housing  16  to be rotated with respect to the bracket  44 , allowing for rotational adjustment about the Z axis. 
     The disclosed mounting system allows the installer to measure and level the light curtain  14  with ease without ever having to turn on the system. Once the curtain is turned on, the installer can rotate the housing  16  to align the beams of the transmitters of the light curtain with the receivers of the light curtain by rotating the housing(s)  16  with respect to the mounting brackets  20 . The disclosed system reduces the number of shims that are required to mount the light curtain and makes alignment much easier. The illustrated system allows for plus or minus 8° of rotational adjustment about the X axis. 
     Although the present invention has been described with a degree of particularity, it is the intent that the invention include all modifications and alterations falling within the spirit and scope of the following claims.