Abstract:
A flange bolt alignment system has an emitting unit including a beam emitting assembly adapted to emit an incident light beam and a beam reflecting assembly having a pivoting beam reflecting element continually oriented along a vertical axis by gravity; and a light reflecting surface on the beam reflecting element, the light reflecting surface positioned to receive the incident light beam and reflect a reflected light beam along a horizontal axis; and a receiving unit adapted for positioning in adjacent, spaced-apart relationship to the emitting unit. A flange bolt alignment method is also disclosed.

Description:
FIELD 
     Illustrative embodiments of the disclosure generally relate to conduits for pipelines and other fluid conveying systems. More particularly, illustrative embodiments of the disclosure relate to a flange bolt alignment systems and methods which facilitate alignment of bolt openings in the flanges of adjoining conduits to expedite bolting of the conduits to each other. 
     BACKGROUND 
     The background description provided herein is solely for the purpose of generally presenting the context of the illustrative embodiments of the disclosure. Aspects of the background description are neither expressly nor impliedly admitted as prior art against the claimed subject matter. 
     In the fabrication of pipelines used to convey fluids such as oil and gas, flanged pipeline conduits are connected to each other end-to-end. The flanges on each pipeline conduit typically include multiple bolt openings which are aligned with the bolt openings in the flanges of the adjacent pipeline conduits. Bolts are typically extended through the registering bolt openings and secured with nuts to attach the flanges and the adjacent conduits to each other. 
     One of the challenges commonly encountered in bolting adjacent pipeline conduits to each other is properly aligning the bolt openings in the flanges of the adjacent conduits with each other to facilitate extension of the bolts through the openings. Accordingly, flange bolt alignment systems and methods which facilitate alignment of bolt openings in the flanges of adjoining conduits to expedite bolting of the conduits to each other is needed. 
     SUMMARY 
     Illustrative embodiments of the disclosure are generally directed to flange bolt alignment systems which facilitate alignment of bolt openings in the flanges of adjoining conduits to expedite bolting of the conduits to each other. An illustrative embodiment of the flange bolt alignment systems has an emitting unit including an emitting unit housing; a beam emitting assembly in the emitting unit housing, the beam emitting assembly having a beam emitting device adapted to emit an incident light beam and at least one power source electrically connected to the beam emitting device; and a beam reflecting assembly in the emitting unit housing, the beam reflecting assembly having a beam reflecting element pivotally carried by the emitting unit housing and continually oriented along a vertical axis by gravity; and a light reflecting surface on the beam reflecting element, the light reflecting surface positioned to receive the incident light beam and reflect a reflected light beam from the emitting unit housing along a horizontal axis; and a receiving unit adapted for positioning in adjacent, spaced-apart relationship to the emitting unit, the receiving unit including a receiving unit housing and a light diffusing element in the receiving unit housing. 
     Illustrative embodiments of the disclosure are further generally directed to flange bolt alignment methods. An illustrative embodiment of the flange bolt alignment methods includes installing an emitting unit in a first bolt opening in a first flange of a first conduit; installing a receiving unit in a second bolt opening adjacent to the first bolt opening in the first flange of the first conduit; emitting a light beam from the emitting unit along a horizontal axis; adjusting a rotational position of the first conduit until the light beam impinges on the receiving unit; aligning a second conduit with the first conduit; installing a receiving unit in a first bolt opening in a second flange of the second conduit; installing a receiving unit in a second bolt opening adjacent to the first bolt opening in the second flange of the second conduit; emitting a light beam from the emitting unit along a horizontal axis; and adjusting a rotational position of the second conduit until the light beam impinges on the receiving unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative embodiments of the disclosure will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is an exploded side view of a typical emitting unit of an illustrative embodiment of the flange bolt alignment systems; 
         FIG. 2  is an exploded side view of a typical receiving unit of an illustrative embodiment of the flange bolt alignment systems; 
         FIG. 3  is a top view of an illustrative embodiment of the flange bolt alignment systems in typical application of the systems; 
         FIG. 3A  is a top view of a typical beam reflecting assembly of an illustrative embodiment of the flange bolt alignment systems in typical application of the systems; 
         FIG. 3B  is a side view of a typical beam reflecting assembly of an illustrative embodiment of the flange bolt alignment systems in typical application of the systems; 
         FIG. 4  is a front view of an illustrative embodiment of the flange bolt alignment systems in typical application of the systems, with a light beam from the emitting unit impinging on the receiving unit of the system to indicate proper horizontal orientation of a pair of bolt openings in a conduit flange; 
         FIG. 5  is a front view of an illustrative embodiment of the flange bolt alignment systems in typical application of the systems, with the light beam from the emitting unit emitting beyond the receiving unit of the system to indicate improper orientation of the pair of bolt openings in the conduit flange; 
         FIG. 6  is an exploded side view illustrating bolting of a pair of conduit flanges on adjacent conduits to each other after utilizing the flange bolt alignment system; 
         FIG. 7  is a side view with the conduit flanges on the adjacent conduits bolted to each other; 
         FIG. 8  is a flow diagram of an illustrative embodiment of the flange bolt alignment methods; 
         FIG. 9  is a top view of an alternative illustrative embodiment of the flange bolt alignment systems in typical application of the systems; 
         FIG. 10  is a top view of a typical beam reflecting assembly of the illustrative flange bolt alignment system illustrated in  FIG. 9 , in typical application of the system; 
         FIG. 10A  is a front view of a typical beam reflecting element of the illustrative flange bolt alignment system illustrated in  FIG. 9 ; and 
         FIG. 11  is a side view of a typical beam reflecting assembly of the illustrative flange bolt alignment system illustrated in  FIG. 9 , in typical application of the system. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the described embodiments or the application and uses of the described embodiments. As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art to practice the disclosure and are not intended to limit the scope of the appended claims. Moreover, the illustrative embodiments described herein are not exhaustive and embodiments or implementations other than those which are described herein and which fall within the scope of the appended claims are possible. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. Relative terms such as “front” and “rear” herein are used with reference to relative positions of various elements with respect to each other in exemplary application of the flange bolt alignment system and are not intended to be used in a limiting sense. 
     Referring initially to  FIGS. 3-7  of the drawings, an illustrative embodiment of the flange bolt alignment systems, hereinafter system, is generally indicated by reference numeral  1  in FIG.  3 . The system  1  includes an emitting unit  2  and a receiving unit  52  which is adapted for positioning in adjacent, spaced-apart relationship to the emitting unit  2  as will be hereinafter described. As illustrated in  FIGS. 6 and 7 , in typical application, which will be hereinafter described, the system  1  ( FIG. 3 ) facilitates alignment of a first set of bolt openings  76  in a first conduit flange  75  on a first conduit  74  with a second set of bolt openings  82  in a second conduit flange  81  on a second conduit  80  for insertion of flange bolts  86  through the registering first and second sets of bolt openings  76 ,  82 , respectively, and coupling of the second conduit  80  to the first conduit  74 . As illustrated in  FIG. 3 , the emitting unit  2  and the receiving unit  52  may initially be inserted through an adjacent pair of the first set of bolt openings  76  in the first conduit flange  75  on the first conduit  74 , after which the emitting unit  2  emits a reflected light beam  50 . In the event that the adjacent pair of the first set of bolt openings  76  is properly disposed in a horizontal plane  98  ( FIG. 4 ), the reflected light beam  50  is transmitted along a horizontal axis  91  ( FIG. 3 ) and impinges on the receiving unit  52 , as illustrated in  FIGS. 3 and 4 . Thus, the second conduit  80  ( FIG. 6 ) can be oriented in like manner such that an adjacent pair of the second set of bolt openings  82  in the second conduit flange  81  on the second conduit  80  are oriented in the horizontal plane  98  and the second set of bolt openings  82  is properly aligned or registered with the first set of bolt openings  76  on the first conduit  74  to insert and secure flange bolts  86  in the first and second set of bolt openings  76 ,  82 , respectively, and couple the second conduit  80  to the first conduit  74 . In the event that the adjacent pair of the first set of bolt openings  76  is not properly disposed in the horizontal plane  98 , the reflected light beam  50  misses the receiving unit  52 , as illustrated in  FIG. 5 . Thus, adjustments in the orientation of the first conduit  74  can be made to position the adjacent pair of the first set of bolt openings  76  in the horizontal plane  98  for alignment of the second set of bolt openings  82  with the first set of bolt openings  76  and coupling of the second  80  to the first conduit  74 . 
     As illustrated in  FIGS. 1 and 3 , the emitting unit  2  of the system  1  may include an emitting unit head  3  and an emitting unit tail  24  which is detachably attached to the emitting unit head  3 . The emitting unit head  3  and the emitting unit tail  24  may include an emitting unit housing  12 . The emitting unit head  3  portion of the emitting unit housing  12  may include an emitting unit head housing  4  which may be generally cylindrical. A tapered emitting unit head neck  5  may extend from the emitting unit head housing  4 . A generally elongated emitting unit head shaft  6  may extend from the emitting unit head neck  5 . The emitting unit head housing  4  may have an emitting unit head end panel  7  which is opposite the emitting unit head shaft  6 . A beam reflecting assembly compartment  8  may be provided in the emitting unit head housing  4 . The beam reflecting assembly compartment  8  may have a transparent compartment wall  9 . 
     The emitting unit tail  24  portion of the emitting unit housing  12  may include an emitting unit tail housing  25  which may be generally cylindrical. A tapered emitting unit tail neck  26  may extend from the emitting unit tail housing  25 . The emitting unit tail housing  25  may have an emitting unit tail end panel  27 . An emitting unit shaft cavity  30  may extend into the emitting unit tail neck  26 . The emitting unit shaft cavity  30  may be sized and shaped to accommodate the emitting unit head shaft  6  of the emitting unit head  3  in detachable attachment of the emitting unit tail  24  to the emitting unit head  3 , as will be hereinafter described. 
     A beam emitting assembly  10  may be provided in the emitting unit head  3  and the emitting unit tail  24  of the emitting unit  2 . The beam emitting assembly  10  may include a beam emitting device socket  11  which is provided in the emitting unit head housing  4 . A beam emitting device  14  may be disposed in electrical contact with the beam emitting device socket  11 . The beam emitting device  14  may include any type of device which is capable of emitting an incident light beam  49  ( FIG. 3 ). For example and without limitation, in some embodiments, the beam emitting device  14  may include a laser-emitting device. 
     A pair of beam emitting device contacts  18  may be provided on an exterior surface of the housing shaft  6  of the emitting unit head  3 . The beam emitting device contacts  18  may be electrically connected to the beam emitting device socket  11  of the beam emitting assembly  10  through contact wiring  20 . A pair of emitting unit tail contacts  40  may be provided in the emitting unit tail neck  26  of the emitting unit tail  24 . The emitting unit tail contacts  40  may be exposed inside the emitting unit shaft cavity  30 . At least one power source  31  may be electrically connected to the emitting unit tail contacts  40  such as through contact wiring  34 . In some embodiments, the power source  31  may include at least one battery  33 . Each battery  33  may be contained inside at least one battery compartment  32 . Accordingly, upon insertion of the emitting unit head shaft  6  of the emitting unit head  3  into the emitting unit shaft cavity  30  in the emitting unit tail  24 , the emitting unit head contacts  18  on the emitting unit head shaft  6  are disposed in electrical contact with the emitting unit tail contacts  40  in the emitting unit tail  24 . Thus, electrical current flows from the power source  31  through the contact wiring  34 , the emitting unit tail contacts  40 , the emitting unit head contacts  18  and the contact wiring  20 , respectively, to the beam emitting device socket  11 . The beam emitting device  14  emits an incident light beam  49  ( FIG. 3 ) for purposes which will be hereinafter described. A switch  38  may be electrically connected between the power source  31  and the emitting unit tail contacts  40  typically through the contact wiring  34  to selectively energize and de-energize the beam emitting device  14 . The switch  38  may be provided on an exterior surface of the emitting unit tail housing  25  or in any other accessible location on the emitting unit tail  24 . 
     As illustrated in  FIGS. 1 ,  3 ,  3 A and  3 B, a beam reflecting assembly  44  may be provided in the beam reflecting assembly compartment  8  of the emitting unit head housing  4 . The beam reflecting assembly  44  may include a beam reflecting element  45  which is disposed in the path of the incident light beam  49  ( FIG. 3 ) emitted from the beam emitting device  14 . The beam reflecting element  45  may be any type of light-reflecting device or component which reflects the incident light beam  49  to the reflected light beam  50  such that the reflected light beam  50  exits the emitting unit head  3  through the compartment wall  9  along the horizontal axis  91  and typically in perpendicular relationship to a longitudinal axis of the emitting unit  2 . An example of a suitable device or component which may be suitable for the beam reflecting element  45  includes a prism. The beam reflecting element  45  may have any design which is suitable for the purpose. As particularly illustrated in  FIGS. 3A and 3B , in some embodiments, the beam reflecting element  45  may be generally triangular in top view with a light-reflecting surface  45   a  which is disposed at a 45-degree angle to the path of the incident light beam  49 . Upon impingement of the incident light beam  49  on the light-reflecting surface  45   a , the reflected light beam  50  is reflected at a 90-degree angle to the incident light beam  49  and exits the emitting unit head housing  4  through the compartment wall  9 . 
     The beam reflecting element  45  may be pivotally mounted in the beam reflecting assembly compartment  8  such as via an element mounting pin  45   b . The element mounting pin  45   b  may attach to the beam reflecting element  45  above the center of gravity of the beam reflecting element  45 . Thus, the beam reflecting element  45  is continually oriented along a vertical axis  90  ( FIG. 1 ) by gravity irrespective of the rotational position of the emitting unit  2 . Therefore, the reflected light beam  50  is transmitted from the emitting unit head  3  of the emitting unit  2  along the horizontal axis  91  ( FIG. 3 ) irrespective of the rotational position of the emitting unit  2 . As illustrated in  FIGS. 1 and 3B , in some embodiments, a counterweight  46  may be suspended from the beam reflecting element  45 . A counterweight support line  47  may be attached to the beam reflecting element  45  and to the emitting unit head end panel  7  via a counterweight support line attachment  48 . The counterweight  46  may be attached to the counterweight support line  47  according to the knowledge of those skilled in the art. Thus, the counterweight  46  may ensure that the beam reflecting element  45  is always oriented along the vertical axis  90  ( FIG. 1 ) by gravity such that the reflected light beam  50  is transmitted from the emitting unit head  3  only along the horizontal axis  91  ( FIG. 3 ). 
     As illustrated in  FIGS. 2 and 3 , the receiving unit  52  of the system  1  may include a receiving unit head  53  and a receiving unit tail  64  which detachably engages the receiving unit head  53 . The receiving unit head  53  and the receiving unit tail  64  may include a receiving unit housing  62 . The receiving unit head  53  portion of the receiving unit housing  62  may include a receiving unit head housing  54  which may be generally cylindrical. A tapered receiving unit head neck  55  may extend from the receiving unit head housing  54 . A generally elongated receiving unit head shaft  56  may extend from the receiving unit head neck  55 . The receiving unit head housing  54  may have a receiving unit housing end panel  57  which is opposite the receiving unit head shaft  56 . A light diffuser compartment  58  may be provided in the receiving unit head  53 . The light diffuser compartment  58  may have a transparent compartment wall  59 . A light diffusing element  60  may be provided in the light diffuser compartment  58 . The light diffusing element  60  may be any type of material which diffuses light upon impingement of the reflected light beam  50  on the light diffusing element  60 . Materials which are suitable for the light diffusing element  60  include glass and plastic, for example and without limitation. 
     The receiving unit tail  64  portion of the receiving unit housing  62  may include a receiving unit tail housing  65  which may be generally cylindrical. A tapered receiving unit tail neck  66  may extend from the receiving unit tail housing  65 . The receiving unit tail housing  65  may have a receiving unit tail end panel  67 . A receiving unit shaft cavity  70  ( FIG. 2 ) may extend into the receiving unit tail neck  66 . The receiving unit shaft cavity  70  may be sized and shaped to accommodate the receiving unit shaft  56  of the receiving unit head  53  in detachable attachment of the receiving unit tail  64  to the receiving unit head  53 , as will be hereinafter described. 
     Referring again to  FIGS. 3-7  of the drawings, in typical application, the system  1  facilitates alignment of the first set of bolt openings  76  in the first conduit flange  75  on the first conduit  74  with the second set of bolt openings  82  ( FIGS. 6 and 7 ) in the second conduit flange  81  on the second conduit  80  for insertion of the flange bolts  86  through the registering first and second sets of bolt openings  76 ,  82 , respectively, and coupling of the second conduit  80  to the first conduit  74 . As illustrated in  FIG. 3 , the emitting unit  2  and the receiving unit  52  may initially be installed in an adjacent pair, respectively, of the first set of bolt openings  76  in the first conduit flange  75  on the first conduit  74 . Installation of the emitting unit  2  in the first one of the adjacent bolt openings  76  may be accomplished by initially inserting the emitting unit head shaft  6  on the emitting unit head  3  of the emitting unit  2  through the first one of the first conduit bolt openings  76  and then inserting the emitting unit head shaft  6  into the emitting unit shaft cavity  30  in the emitting unit tail  24 . Thus, the power source  31  in the emitting unit tail  24  is disposed in electrical communication with the beam emitting device  14  in the emitting unit head  2  typically through the contact wiring  34 , the emitting unit tail contacts  40 , the emitting unit head contacts  18 , the contact wiring  20  and the beam emitting device socket  11 , respectively, of the beam emitting assembly  10 . In some embodiments, the beam emitting device  14  may be selectively energized to emit the incident light beam  49  typically by actuation of the switch  38 . Installation of the receiving unit  52  in the second one of the adjacent bolt openings  76  may be accomplished by initially inserting the receiving unit head shaft  56  on the receiving unit head  53  of the receiving unit  52  through the second one of the first conduit bolt openings  76  and then inserting the receiving unit head shaft  56  into the receiving unit shaft cavity  70  in the receiving unit tail  64 . As illustrated in  FIG. 3 , the receiving unit  52  is thusly disposed in adjacent and spaced-apart relationship to the emitting unit  2  with the beam reflecting element  45  of the beam reflecting assembly  44  in the emitting unit  2  adjacent to the light diffusing element  60  in the receiving unit head  53  of the receiving unit  52 . 
     The rotational position of the first conduit  74  may initially be manually adjusted in an attempt to position the pair of adjacent first conduit flange bolt openings  76  in the horizontal plane  98  ( FIG. 4 ) as closely as possible. The system  1  is then operated to determine whether the pair of adjacent first conduit flange bolt openings  76  are disposed in the horizontal plane  98 . Accordingly, the switch  38  ( FIG. 1 ) may be manipulated to establish flow of electrical current from the power source  31  to the beam emitting device  14  in the emitting unit head  3  of the emitting unit  2 . The beam emitting device  14  emits the incident light beam  49 , which impinges on the light reflecting surface  45   a  of the beam reflecting element  45 . The reflected light beam  50  is transmitted from the emitting unit head  3  along the horizontal axis  91  ( FIG. 3 ). 
     As illustrated in  FIG. 4 , in the event that the adjacent pair of the first set of bolt openings  76  is properly disposed in the horizontal plane  98 , the light diffusing element  60  of the receiving unit  52  lies in the path of the reflected light beam  50  emitted from the emitting unit  2 . Thus, the reflected light beam  50  impinges on the light diffusing element  60  in the receiving unit head  53  of the receiving unit  52 , as illustrated in  FIGS. 3 and 4 , and diffuses the light to indicate the horizontal position of the adjacent pair of the first set of bolt openings  76 . As illustrated in  FIG. 5 , in the event that the adjacent pair of the first set of bolt openings  76  is not properly disposed in the horizontal plane  98 , the reflected light beam  50  misses the receiving unit  52  due to the continual orientation of the beam reflecting element  45  along the vertical axis  90  and thus, the transmission of the reflected light beam  50  along the horizontal axis  91 . Thus, adjustments in the rotational position of the first conduit  74  can be made to orient the adjacent pair of the first set of bolt openings  76  until the reflected light beam  50  impinges on the light diffusing element  60 , thus indicating that the adjacent pair of the first set of bolt openings  76  are disposed in the horizontal plane  98 . After the second conduit  80  is aligned with the first conduit  74 , the foregoing procedure can be carried out with respect to the second conduit  80  ( FIG. 6 ) such that an adjacent pair of the second set of bolt openings  82  in the second conduit flange  81  on the second conduit  80  are oriented in the horizontal plane  98  and the second set of bolt openings  82  is properly aligned or registered with the first set of bolt openings  76  on the first conduit  74 . The flange bolts  86  can be inserted through the registering first and second set of bolt openings  76 ,  82 , respectively, and typically secured with nuts  87  to couple the second conduit  80  to the first conduit  74 . 
     Referring next to  FIG. 8  of the drawings, a flow diagram  100  of an illustrative embodiment of the flange bolt alignment methods is illustrated. At block  102 , an emitting unit of a flange bolt alignment system may be installed in a first bolt opening in a first flange of a first conduit. At block  104 , a receiving unit of the flange bolt alignment system may be installed in a second bolt opening adjacent to the first bolt opening in the first flange of the first conduit. At block  106 , a light beam may be emitted from the emitting unit along a horizontal axis and typically in perpendicular relationship to a longitudinal axis of the emitting unit. At block  108 , the rotational position of the first conduit may be adjusted until the light beam impinges on the receiving unit. 
     At block  110 , a second conduit may be aligned with the first conduit. At block  112 , the emitting unit of the flange bolt alignment system may be installed in a first bolt opening in a second flange of the second conduit. At block  114 , the receiving unit of the flange bolt alignment system may be installed in a second bolt opening adjacent to the first bolt opening in the second flange of the second conduit. At block  116 , a light beam may be emitted from the emitting unit along a horizontal axis and typically in perpendicular relationship to a longitudinal axis of the emitting unit. At block  118 , the rotational position of the second conduit may be adjusted until the light beam impinges on the receiving unit. At block  120 , bolts may be installed and secured in the registering bolt openings in the first flange on the first conduit and the second flange on the second conduit, respectively, to couple the second conduit to the first conduit. 
     Referring next to  FIGS. 9-11  of the drawings, an alternative illustrative embodiment of the flange bolt alignment systems is generally indicated by reference numeral  101  in  FIG. 9 . In the system  101 , elements which are analogous to the respective elements of the assembly  1  that was heretofore described with respect to  FIGS. 1-7  are designated by the same numeral in the 101-199 series in  FIGS. 9-11 . The emitting unit head end panel  107  and the compartment wall  109  may be component parts of an emitting unit head cap  116  which detachably engages the emitting unit head  103  typically at a set of threads  161 . Accordingly, the emitting unit head cap  116  can be selectively detached from the emitting unit head  103  of the emitting unit  102  to facilitate maintenance and repair or replacement of the interior components of the emitting unit head  103  such as the beam emitting assembly  110  and the beam reflecting assembly  144 . In some embodiments, the receiving unit head end panel  157  and the compartment wall  159  may be component parts of a receiving unit head cap  172  which detachably engages the receiving unit head  153  typically at a set of threads (not illustrated). Accordingly, the receiving unit head cap  172  can be selectively detached from the receiving unit head  153  of the receiving unit  152  to facilitate maintenance and repair or replacement of the interior components of the receiving unit head  153  such as the light diffusing element  160 . 
     As illustrated in  FIGS. 10 and 11 , in some embodiments, the beam reflecting element  145  may be secured to the emitting unit head end panel  107  inside the beam reflecting assembly compartment  108  by threading an assembly mount bolt  151   a  in an assembly mount tube  151  which extends through a tube opening (not illustrated) in the emitting unit head end panel  107 . The beam reflecting element  145  may be mounted on the assembly mount tube  151  inside the beam reflecting assembly compartment  108 . 
     As illustrated in  FIGS. 9 and 10 , operation of the system  101  may be as was heretofore described with respect to operation of the system  1  in  FIGS. 1-7 . The beam reflecting assembly  145  may be capable of receiving the incident light beam  149  emitted by the beam emitting device  114  of the beam emitting assembly  110  and reflecting a pair of reflected light beams  150  from opposite sides of the emitting unit head  103  generally perpendicular to a long axis of the emitting unit  102  and along a horizontal axis  191  ( FIG. 10 ). Accordingly, the emitting unit  102  can be placed on either side of the adjacent receiving unit  152  since the reflected light beams  150  emerge from both sides of the emitting unit head  103  of the emitting unit  102 . This may facilitate ease in use of the system  101 . 
     While illustrative embodiments of the disclosure have been described above, it will be recognized and understood that various modifications can be made and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the disclosure.