Abstract:
The focus angle of a search light mounted on a helicopter or other platform is narrowed or widened by rotating a bidirectional focus control cam in a clockwise or counterclockwise direction as selected by a manually operated three-position control switch which determines the rotational direction of a DC motor driving the bidirectional focus control cam. The DC motor has first and second terminals which are selectively connected to either a DC power source or ground by a double-pole, single throw dual relay which reverses the polarity and thus the direction of rotation of the DC motor. The dual relay is connected by the same single wire interface currently in use to the manually operated control switch, which manually operated control switch is within a control box located in the helicopter. By operating the manually operated control switch to connect coils in the dual relay to either a power source or to ground, the coils are selectively energized or deenergized causing the dual relay to operate switches that reverse polarity of current flowing through the DC motor. This selectively changes the direction of rotation of the bidirectional cam which advances and retracts a focusing reflector within the search light to widen and narrow its focus angle, thereby widening and narrowing the area illuminated by the search light beam.

Description:
FIELD OF THE INVENTION 
     The present invention is directed to a focus control for search lights. More particularly, the present invention is directed to a bidirectional focus control for search lights. 
     BACKGROUND OF THE INVENTION 
     Search lights are extensively used on police and rescue helicopters to illuminate subjects on the ground and in the water. Generally, search lights are mounted on gimbles which enable the search lights to be angularly adjusted with respect to helicopters in order for the light beams of the search lights to remain in alignment with subjects under scrutiny. This is necessary because a subject may move with respect to a helicopter, either as the helicopter moves, or when the helicopter is substantially stationary and the subject moves. It is frequently necessary to first illuminate a relatively large area in order to locate whatever subject is of interest and then to progressively illuminate smaller and smaller areas in order to isolate the subject so that the subject can be readily discernable by a helicopter crew or other observers either on the ground or at another location. 
     Currently, the focus of a search light beam from a helicopter mounted search light is adjusted by a uni-directional cam which is driven to rotate in only one direction by a DC motor. Consequently, if a desired focus angle has been passed and one wishes to change the size of an area illuminated, there is a lag period as the uni-directional cam recycles. This can result in the subject being observed either escaping from or unintentionally moving out of an illuminated area. It is therefore desirable to rotate the cam in both directions in order to enhance an operator&#39;s ability to maintain a desired illuminated area or to rapidly change the size of the area without recycling the cam. 
     In helicopters and fixed-wing aircraft, search lights are generally connected by a connecting wire harness to internal cable systems within the fuselage of the helicopter or aircraft. In accordance with standard practice, there is only a single wire in the connecting wire harness devoted to interfacing with the focus control for the search lights, which focus control axially moves bidirectionally according to the rotational position of the uni-directional cam. Normally in order to make the cam bidirectional, the DC motor must run in both directions. In the prior art bidirectional motor rotation requires two wires, one for each direction of cam rotation. In order to provide a second wire in the wire harness, the wire harness must be changed or re-engineered. Moreover, after the wire harness has been changed or re-engineered, the helicopter or aircraft must be inspected by licensing authorities and the new wiring arrangement approved before the aircraft or helicopter is legally allowed to fly. This is an expensive, time-consuming undertaking which requires not only re-wiring of the connecting harness but also re-wiling of the search lights and search light controls. Consequently, helicopters and aircraft already equipped with search lights having a single wire for focus control forego improvements in focus control which would enable focus control to proceed in both directions rather than a single direction. 
     In view of the aforementioned considerations, there is a need for an arrangement which allows a search light on a helicopter or an aircraft to be modified in order to have a bidirectional focus control without having to do any re-wiring. 
     While this problem is primarily a problem with search lights mounted on platforms such as helicopters and fixed wing aircraft, it is also a consideration for other platforms such as search lights mounted on boats and land vehicles and even those mounted on remotely controlled stationary supports. 
     SUMMARY OF THE INVENTION 
     It is a feature of the present invention to provide a new and improved focus control for a search light wherein the focus control is bidirectional and requires but a single control wire interface with a control station remote from the search light. 
     The present invention is directed to a focus control for narrowing and widening the focus angle of a search light beam emitted by a search light mounted on a platform having a power source. The search light includes a motor, a cam driveable by the motor to rotate and a focus control operated by the cam for narrowing and widening the focus angle in response to control signals over a single wire interface between a remotely positioned control switch and the motor. The remotely positioned control switch has an open position, a power source position and a ground position, wherein when the remotely positioned control switch is in the power source position, the single wire interface is in a first state different from a second state of the single wire interface which occurs when the remotely position control switch is in the ground position. A switching circuit is connected between the power source and the motor for reversing polarity of current flowing through the motor. The switching circuit is connected to the remotely positioned control switch by the single wire interface and includes an input responsive to a change in state of the single wire interface, which input reverses the polarity of current flowing through the motor to reverse rotation of the motor and thus the cam. When rotation of the cam reverses, the direction of the focus angle magnitude reverses. 
     In another aspect of the invention, the motor is a DC motor and circuitry is included for connecting both poles of the DC motor to ground when the remotely positioned switch is in the open position. 
     In still another aspect of the invention, diodes suppressing voltage spikes are provided between the first and second poles of the motor and the power source, as well as between the poles and ground. 
     In still another aspect of the invention, the input comprises a pair of coils, one connected to the power source and the other connected to ground. Both coils are directly connected to the single wire interface, whereby a change in state of the single wire interface deenergizes one coil while the other coil remains energized. The coils are each associated with a bipolar switch connected to the DC motor and disposed between ground and the power source, the bipolar switches individually changing connections to reverse polarity of current flowing through the DC motor as the coils are individually deenergized due to changes in state of the single wire interface. 
     Aspect of the invention, in order to protect the coils, protective diodes are disposed between the power source of the coils and the single wire interface, as well as between ground and the single wire interface. 
     In still a further aspect of the invention, the switching circuit is a double-pole, single-throw dual relay. 
     In a more specific aspect of the invention, the platform upon which the search light is mounted is a helicopter or fixed wing aircraft having a fuselage; the search light being mounted on the helicopter or aircraft at a location exterior to the fuselage and the remotely positioned switch being within the fuselage and connected to the switching circuit by the single wire interface. 
     In still another aspect of the invention, the switching circuit includes a double-pole, single-throw dual relay and includes circuitry for connecting both poles of the DC motor to ground when the remotely positioned switch is in the open position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various other features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts through the several views, and wherein: 
     FIG. 1 is a perspective view of an airborne platform, such as a helicopter, having a search light mounted thereon, wherein the search light has an adjustable focus; 
     FIG. 2 is a perspective view of a portion of the airborne platform of FIG. 1 showing a search light employing features of the present invention mounted thereon; 
     FIG. 3 is a perspective view of a search light configured in accordance with the prior art showing a cam driven by a motor for adjusting the focus of the search light of FIGS. 1 and 2; 
     FIG. 4 is a perspective view of a back plate of the search light of FIG. 3 modified to include circuitry configured in accordance with the present invention; 
     FIG. 5 is a circuit diagram illustrating a search light focus control circuit configured in accordance with the principles of the present invention, the circuit being in an inactive mode prior to applying electric power to the circuit; 
     FIG. 6 is the circuit of FIG. 5 but showing the circuit energized by DC current applied thereto; 
     FIG. 7 is the circuit of FIGS. 5 and 6 but showing the circuit energized to rotate the armature of a focus control motor to drive a bidirectional cam in a clockwise direction, and 
     FIG. 8 is the circuit of FIGS. 5-7 but showing the circuit energized to rotate the armature of the focus control motor to drive the bidirectional cam in a counter-clockwise direction. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, there is shown a platform in the form of a helicopter  10  having a fuselage  11  with a search light  12  mounted thereon, the search light casting a light beam  14  with a focus angle θ, which light beam illuminates an area  16  of ground or water. Frequently, it is desirable to expand or decrease the area  16  being illuminated by expanding or contracting the focus angle θ of the beam  14 . For example, in order to search a large area  16 ′ for a particular subject  18 , the beam  14  has a wide focus angle θ 1 . In order to concentrate on a specific subject  18 , such as the person, the beam  14  is progressively narrowed to have a focus angle of θ 2 , illuminating a smaller area  16 ″. In accordance with the present invention, the focus angle θ is changeable bidirectionally by a control within the helicopter  10  to either immediately widen the focus angle θ so as to approach θ 1 , or to immediately narrow the focus angle so as to approach θ 2 . 
     Referring now to FIG. 2, it is seen that the search light  12  is mounted on a gimble  20  which is in turn supported by a tripod arrangement  22  attached to the fuselage  11  of the helicopter  10 . The gimble  20  is driven by electric drives  24  and  25  to steer the beam  14  so that the beam can move independently of the orientation of the helicopter  10 . The search light  12  also includes a bulb  26  and an internal focus DC control motor  28  (see FIGS.  3  and  4 ). The drive  24 , bulb  26  and focus motor  28  each receive +28 volt DC power from the helicopter  10  through an external wire harness cable  30 , which wire harness cable  30  includes a single wire interface  32  (see FIGS. 5-8) for controlling the DC motor  28 . 
     As is seen in FIG. 2, the wire harness  30  has a connector  34  at one end thereof which plugs into a cooperating connector  36  connected to internal cables (not shown) within the fuselage  11  of the helicopter  10 . The type of search light  12  is exemplified commercially by search lights available from SpectroLab, Inc., of Sylmar, Calif., a Hughes Electronics Corporation company, and identified as NIGHTSUN® SX-16® and STARBURST SX-5® search lights. 
     Referring now mainly to FIGS. 3 and 4, where interior portions  40  of the search light  12  are shown, it is seen that the motor  28  drives a cam  42  as armature  43  rotates. The cam  42  abuts a cam follower  44  which is urged by springs  45  against the cam. The cam follower  44  is connected by rods  46  to a reflector  47  which, when moved axially in the direction of arrow  48 , narrows the focus angle θ toward the minimum focus angle θ 2  and which when moved in the direction of the arrow  49  widens the focus angle θ toward the maximum focus angle θ 1 . 
     Referring now mainly to FIG. 4, the housing of the search light  12  has a back plate  52  on which has been mounted a circuit board  53 , which in turn mounts the components of a search light head circuit  60 . The search light head circuit is a switching circuit through which current passes to drive the DC motor  28  to rotate the armature  43  in either a clockwise direction or the counter-clockwise direction. 
     According to the present invention, the armature  43  of the DC motor  28  bidirectionally rotates the cam  42  in order to axially slide focus control rods  46  and thus axially position the reflector  47 . The focus control rods  46  and the cam  42  already exists in prior art search lights  12  if the search lights are exemplified by the NIGHTSUN SX-16® and STARBURST SX-5® search lights. In accordance with the prior art, the DC motor  28  rotates the cam  42  in only one direction. Consequently, there can be a lag period as the cam  42  cycles around to a desired focus angle that was passed in a previous focus angle adjustment. By utilizing the present invention, the lag time is eliminated because the rotation of the cam  42  is now bidirectional. 
     Having a bidirectional cam  42  to allow an immediate change in the magnitude of the focus angle θ is of considerable interest to police departments. This is because the focus angle θ is only one of several activities preformed by a police helicopter pilot during a search in that the pilot must also adjust the search light  12  while simultaneously flying the helicopter  10  and talking on the radio. TV stations fly their own helicopters videoing the pursuit of criminal suspects. The pursuit is broadcast in real time by television stations as information for, and perhaps entertainment of, the general public. If a pursuit takes place at night, the search light beam  14  is of primary significance and is an important aspect in enhancing the spectacle. The police helicopter pilot then has the added pressure of thousands of excited television fans before whom he must perform. Having bidirectional focus angle control makes it less likely that pilot will mess up and lose sight of the suspect, a mistake not lot on his television audience. This enhancement of focus angle control is also of enormous value in other operations, such as, for example, attempting a rescue at sea during a storm, rescuing hikers stranded in the wilderness or medivacting the injured or sick. 
     Referring now to FIGS. 5-8, there is shown a diagram of circuitry according to the present invention which allows the search light head circuit  60  disposed within the search light  12  to function as a switching circuit controlled from a control box circuit  62  situated within the fuselage  11  of the helicopter  10  by utilizing only the single wire interface  32  currently within the wiring harness  30 . The search light head circuit  60  includes a dual relay  64  which is connected through a protective diode pair  65  to the single wire interface  32  as well as a diode array  66  which protects the motor  28  from voltage spikes. 
     Within the control box circuit  62  located in the helicopter  10  there is a remotely positioned, bidirectional control switch SW 1  that is connected to the dual relay  64  in the search light head circuit  60  by the single wire interface  32 . Since the control switch SW 1  is in the fuselage of the helicopter  10 , it is remotely positioned with respect to the search light  12  which is mounted exteriorly with respect to the fuselage in the tripod  22 . The control switch SW 1  is a manual switch having three positions, i.e., the OFF position shown in FIGS. 5 and 6 in which both momentary contacts  70  and  71  arc open; a first momentary closed position in which momentary contact  70  is closed as is shown in FIG. 7, and a second momentary closed position in which the momentary contact  71  is closed as is shown in FIG.  8 . As will be explained hereinafter, there is a change in state on the single wire interface depending on the position of the control switch SW 1  so that in the first momentary closed position, the DC motor  28  rotates the focus control cam  42  clockwise as is shown in FIG.  7  and in the second momentary closed position of FIG. 8, the DC motor  28  rotates the cam  42  in the counter-clockwise direction as is seen in FIG.  8 . 
     In a preferred embodiment of the invention, the dual relay  64  is a double pole, single throw relay. As is seen in FIG. 4, the dual relay  64  is conveniently mountable on circuit board  53  attached to the back plate  52  of the housing of search light  12 , which back plate already has space available to receive the circuit board  53 , thus allowing unidirectional prior art focusing arrangements to be conveniently converted to bidirectional focusing arrangements. 
     Considering the circuit elements more specifically, the momentary closed contact  70  is connected through a  100  ohm  3 -watt resistor R 1  to a power source provided by a +28 volt DC power supply  72  and through a first 18-volt Zener diode D Z1  to ground  73 . Throughout these drawing figures the power source is the helicopter&#39;s +28 volt DC power supply  72  and ground  73  is the helicopter grounding system. In other applications the power source may be different, for example, in a boat or motor vehicle the power source may be +12 volt DC. The dual relay  64  has a first coil  76  therein which is connected via a line  77  to the 28-volt DC power source via a 100 ohm 3-watt resistor R 2  and which is connected to ground through a second 18-volt Zener diode D Z2 . A second coil  78  is connected directly to ground via a line  79 , while the first coil  76  and second coil  78  are mutually connected to the single wire interface  32  through protective diode pair comprising diodes D 1  and D 2 . The protective diodes D 1  and D 2  are flyback diodes which clamp any voltage flybacks which occur when the coils  76  and  78  are de-energized, thereby protecting the coils, also within the dual relay  64  are switches SW 2  and SW 3 . Switches SW 2  and SW 3  close normally closed contacts  81  and  82  connected to the +28-volt DC power supply  72  via line  83  while normally open contacts  84  and  86  are connected to ground  73  via line  88 . The coils  76  and  78  provide an input to the switches SW 2  and SW 3  which is responsive to a change in state on the single wire interface  32  which as explained hereinafter reverses polarity of current flowing through the motor  28 . 
     The DC motor  28  is connected via line  90  to the +28-volt DC power supply  72  through protective diode D 3  while the line  91  is connected to the +28-volt power supply  72  through protective diode D 4 . Line  90  is also connected to ground through protective diode D 5  while line  91  is connected to ground  73  through protective diode D 6 . The diodes D 3 -D 6  suppress both positive and negative voltage spikes that are generated when switching the DC motor  28  “on” and “off”. The Zener diodes D Z1  and D Z2  regulate the power supply voltage down from +28 volts DC to +18 volts DC for use by the manual control switch SW 1  and by the components of the dual relay  64 . 
     Considering now the operation of the circuitry of FIGS. 5-8, FIG. 5 illustrates the condition of circuitry when the helicopter  10  is not operating and thus not generating +28-volt DC power for the power supply  72 . Accordingly, in FIG. 5 the +28-volt DC power is not shown. In this condition, switch SW 1  in the control box circuit  62  is in the OFF position and the switches SW 2  and SW 3  and the dual relay  64  arc open. 
     Upon starting the helicopter  10  so as to supply +28-volt DC power, the switch SW 1  remains open but the switches SW 2  and SW 3  automatically switch to a normally open mode in which they contact the normally open contacts  84  and  86  so as to connect both line  90  and line  91  to ground  73  by energizing both the first coil  76  and the second coil  78 . When switch SW 1  is open, no voltage from the control box  62  in the fuselage  11  of the helicopter  10  is present on the single wire interface  32 , consequently the voltage is allowed to float to a potential of about +9 volts due to the matched resistance of the first and second coils  76  and  78  and the +18 volt Zener diode D Z2  connected to coil  76 . By having +9 volts across the coils  76  and  78 , there is enough voltage to energize each of the relay switches SW 2  and S W 3  which results in both relay switches moving to the normally open position in which the normally open contacts  84  and  86  are closed. The DC motor  28  is thus grounded on both poles provided by terminals  92  and  93  thereof because the +28 volt DC power supply  72  is applied to both line  90  and line  91  by lines  94  and  95 , respectively. The armature  43  of the DC motor and thus the bidirectional cam  42  are then positively held stationary with no rotation. 
     Referring now to FIG. 7 in which clockwise rotation  100  of the armature  43  and cam  42  occurs, it is seen that when the switch SW 1  is moved to close with the contact  70 , there is a change in state on the single interface wire from an inactive state to a first active state where +18 volts is applied through the single interface wire  32 , the resistor R 1  having reduced the +28 volt DC power supply  72 . Application of +18 volts to the single wire interface  32  to place the single wire interface in the first state causes the first coil  76  to de-energize while the second coil  78  remains energized. This causes the first relay switch SW 2  to close with the contact  81  while the second relay switch SW 3  remains closed with the normally open contact  86 . Current therefore flows through the first relay switch SW 2 , line  90  and DC motor  28  to ground  73  through line  91  and the second relay switch SW 3 . This causes the armature  43  of the motor  28  to rotate the bidirectional cam  42  in the clockwise direction  100  as long as the switch SW 1  in the control box circuit  62  closes with the contact  70 . Upon releasing the switch SW 1 , the first relay switch SW 2  returns to the OFF position so that the first relay switch SW 2  opens the normally closed contact  81  and closes the normally open contact  84 , thus returning the circuitry to the mode of FIG. 6, which positively holds the armature  43  and thus the cam  42  positively fixed with no rotation so as to stabilize the selected focus angle θ of the beam  14 . Referring now to FIG. 8 if it is desired that the armature  43  and the cam  42  rotate in the counter-clockwise direction  102 , the manual switch SW 1  is moved from the inactive off state to close with contact  71  which puts the single interface wire  32  in a second active state. This causes the second coil  78  to de-energize while the first coil  76  remains energized which results in the second relay switch SW 3  closing with contact  82  while the first relay contact switch SW 2  remains closed with the normally open contact  84 . Power supplied +28-volt DC current flows through the second relay switch SW 3  over line  91  and through the motor  28  to line  90 . Line  90  is connected to ground  73  through the first relay switch SW 2  so that in the mode of FIG. 8, the direction of current flow to the DC motor  28  is reversed with respect to current flow through the DC motor in the mode shown in FIG.  7 . This causes the armature  43  and cam  42  to rotate in the counter-clockwise direction  102 . When the manual control switch SW 1  in the control box circuit  62  is thereafter moved to the OFF position, the second relay switch SW 3  opens contact with the normally closed contact  82  and closes contact with the normally open contact  86  so that the circuit arrangement returns to the mode of FIG.  6 . As was stated before, when the circuit arrangement is in the stabilized mode of FIG. 6, the armature  43  is electrically locked to positively fix the bidirectional cam  42  in its last position so that the cam cannot inadvertently rotate and change the focus angle θ. 
     While the circuit disclosed in FIGS. 5-8 is a preferred circuit, corresponding circuits using equivalent components such as power transistors and chips which are now available or which may become available in the future are within the purview of this disclosure. 
     In the aforedescribed exemplary embodiment of the invention, the following specific circuit components were used: 
     Dual relay  64 —double pole, single-throw dual relay Model No. V2R1002, available from Potter &amp; Brumfield; 
     DC Motor  28 —DC motor with a permanent magnet available from Globe Motors Co.; 
     Zener diodes D Z1  and D Z2 —1N5355B-18 volts; 
     Diodes D 1 -D 6 —IN4936, and 
     Resistors R 1  and R 2 —100 ohm, 3-watt 
     While the focus control described herein is especially useful for search lights  12  mounted on helicopters  10 , it is also useful for mounting on fixed wing aircraft, boats, land vehicles, and stationary illuminating facilities. With applications other than helicopters and fixed-wing aircraft the power supply voltages may need to be altered so that the platform upon which the search light is mounted can readily accept the modification set forth in this disclosure. For example, boats and land vehicles may have a 12-volt DC power supply  72  so that the components of the circuits as shown in FIGS. 5-8 would need to be modified to operate from a 12-volt DC power supply rather than a 28 volt DC power supply. 
     From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.