Abstract:
A fire-fighting turret or monitor includes a curved pipe formed in three successive sections separated by swivelable joints. The first joint swivels about the axis of the first section; the second joint swivels about an axis disposed at an acute angle to the first axis; and the third section includes a corresponding bend so that the exit from the third section can be pointed anywhere within substantially a hemisphere.

Description:
FIELD OF THE INVENTION 
     This invention relates to a fire-fighting turret or monitor, or similar fluid-projecting device, which is mounted in a fixed position but can be aimed in any direction and at any elevational angle by rotating a pair of swivelable joints disposed at an acute angle to each other. 
     RELATED CASES 
     This application claims the benefit of provisional application Ser. No. 60/213,016 filed Jun. 21, 2000 and entitled “A New Design for Fire-fighting Water Turrets, or Monitors”. 
     BACKGROUND OF THE INVENTION 
     In fire fighting and other applications, water turrets or monitors are used to direct a stream of water. Generally these monitors are controlled by a manual operator who maneuvers a handle or other mechanically linked device, or by an operator who remotely controls the action of the monitor through hydraulic or electric links or a combination thereof. Such monitors can also be operated and activated automatically, as for example by a fire detector or timed circuit. 
     It is desirable to make such turrets cover an area with a volume of water by appropriately moving the nozzle continuously or intermittently to aim the water stream in different directions. In general, the positional variables of the monitor include the elevation and azimuth in which the nozzle is pointing or spraying. Thus terms like Left, Right, Up and Down are used to label the positional turret controls and describe the motion of the stream. 
     As the state of the art has evolved from handheld hoses and nozzles to the manually operated turrets, and on to the remotely controlled and automatic monitors discussed above, there has been a tendency to add onto current methods without going back to the primary function to be served and creating a product from the ground up. Thus the axes necessary to create independent left-right and up-down actions were maintained without change from the hose to the monitor to the remote-controlled monitor. In addition, each of the axes or joints could be held against unintended movement by a mechanical device such as a friction lock or a pin in a hole. Automating merely meant adding electrical, mechanical or hydraulic actuators to the joints and swivels that were used in the mechanically controlled units. To gain the torque necessary to control the joints and to supply the static friction required to hold the nozzle in place when not being moved in one of the axes, a combination of gears including a worm gear was generally used. 
     Several general models of monitors have been devised to create the ability to sweep through the necessary range. One of these is a re-converging stream in which the water generally passes through a pipe that swivels to create the left-right rotation and coverage, then splits roughly equally and directs the water through separate symmetric pipes into flows which are perpendicular to the first swivel. This allows for a second set of swivels to provide the up-down coverage. Then the water is re-converged into a single stream and sent through a nozzle as desired. This model requires several complex cast components. Splitting the water into two pipes, forcing it through a quick series of sharp bends, then recombining the two streams which are running in almost opposite directions creates turbulence, back pressure and pressure losses that are detrimental to the water flow. 
     Another model can be thought of as a series of bent tubes. In this traditional configuration the water stream is forced over 45° of bends, with one bend being a 180° bend causing the stream to flow twice as far and twice as fast on the outside of the bend as the water on the inside of the bend. This geometry also creates turbulence and pressure drops that are adverse to the final stream pattern. 
     A third model is a tighter version of the bent tube design created by using castings. This allows for a tighter geometry but exaggerates the turbulence of flow speed differentials. In order to combat these problems, this design is forced to increase the cross-sectional area of the joint areas, which increases turbulence and forces acting on the joints. Even internal flow straightening vanes cast into the waterways to combat these deficiencies have the adverse effect of causing additional surface drag. 
     When these designs were automated to allow for operator control through switches or a joystick, or to allow for automatic operation in a preset manner without input from an operator, gearing and actuators such as electric and hydraulic motors were added on top of existing designs. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems of the prior art by providing a monitor or turret using a single curved tube with three mutually rotatable sections. The sections are separated by two swivelable joints whose axes are at an acute angle (e.g. 45°) to each other. The axes of the joints are interdependent, i.e. rotation of one joint changes the axial or angular orientation of the other joint. By concurrently rotating both joints, the nozzle can be aimed at any point within more or less a hemisphere centered on the monitor. 
     In accordance with one aspect of the invention, the joints are preferably rotated by a direct electric or hydraulic drive or servo motor in which the static position of the monitor is maintained electrodynamically or electromechanically. A microprocessor control computes and executes the appropriate motion of each joint to obtain a nozzle orientation having a desired bearing and azimuth within the monitor&#39;s hemisphere. 
     In the joint mechanism of this invention, the fundamental components of the joints and bearings are part of the waterway formed by the curved tube. The geometry of the joints is such that the water stream at each joint is always coaxial with that joint so as to eliminate any water-caused torque on the joint and drive. The geometry of the monitor is such that a full forwardly extending hemisphere ahead of a fire truck can be covered by a monitor mounted on a horizontal pipe on the front of the truck without requiring a 90° bend for vertical mounting. Alternatively, the inventive monitor can cover an entire upwardly extending hemisphere centered on the truck if mounted vertically. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a horizontal section through a horizontally truck-mounted first embodiment of the monitor of this invention with the nozzle aimed straight ahead; 
     FIG. 2 is a view similar to FIG. 1 but showing the nozzle aimed to the left; 
     FIG. 3 is a view similar to FIG. 1 but showing the nozzle aimed to the right; 
     FIG. 4 is a plan view of the monitor with the nozzle aimed up; 
     FIG. 5 is a view similar to FIG. 1 but showing an alternative embodiment of the invention; 
     FIG. 6 is a view similar to FIG. 3 but showing the alternative embodiment of FIG. 5; 
     FIG. 7 is a block diagram of an automatic control for the inventive monitor; and 
     FIG. 8 is a spatial diagram illustrating the geometry of the inventive monitor. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a monitor  10  mounted on a horizontal pipe  12  e.g. on the front of a fire truck. The monitor  10  has a base section  14  terminating in a first joint  16  in which the midsection  18  of monitor  10  is mounted for swiveling movement about the horizontal axis  20 . At its other end, the midsection  18  terminates in a second joint  22  in which the nozzle-carrying exit section  24  is mounted for swiveling movement about an axis  26  preferably disposed at a 45° angle to the axis  20 . A 45° angle produces a hemispheric coverage; greater or lesser angles produce greater or lesser coverage. The midsection  18  and the exit section  24  are preferably so curved that when the nozzle  28  is aimed straight ahead as shown in FIG. 1, the base section  14  and the nozzle  28  are coaxial. 
     When the nozzle  28  is aimed straight ahead, the net torque exerted by the water stream on the monitor  10  as a whole is essentially zero because the torque created by the clockwise 45° bends in the exit section  24  and the proximal end  30  of the midsection  18  are balanced by the 90° counterclockwise bend of the distal portion  32  of midsection  18 . It will be noted that at the joints  16 ,  22  themselves, the water flow is coaxial with the joint, so that regardless of the position of the joint, the water flow through the joint does not create any torque on it. 
     The joints  16  and  22  may be swiveled by motors  34  and  36 , respectively. These motors have relatively small drive gears  38  that engage the much larger gear  40  of the swiveling joint itself. Because of this size disparity, it is possible in the device of the invention to use a direct drive instead of the more cumbersome worm gear drive typical of the prior art. This in turn makes it practical to swivel the joints  16 ,  22  by hand, e.g. in case of a motor failure, through a hand wheel  42 . 
     To prevent undesired movement of the monitor  10 , the shafts  44  of drive gears  38  may be equipped with conventional brakes  46  that prevent the shafts  44  from turning unless the motors  34 ,  36  are powered or the brake  46  is manually released. Alternatively, the motors  34 ,  36  may be computer-controlled servomotors that electrically maintain the joints  16 ,  22  in the desired positions. Dynamic braking may also be achieved by shorting the motor poles through a normally closed switch that can be opened for manual override. 
     FIGS. 2 through 4 show the nozzle  28  aimed to the left, to the right, and to the observer, respectively. If the two limit positions of the axis  37  of nozzle  28  (which is at an acute angle to axis  26 ) as a result of the swiveling of joint  22  are coaxiality with axis  20  and perpendicularity thereto, FIGS. 2-4 will show that the monitor of FIG. 1 is capable of aiming the nozzle  28  anywhere within a hemisphere centered on the monitor  10 . 
     FIGS. 5 and 6 illustrate an alternative embodiment of the invention, in which the midsection  18  forms a single 45° bend between the joint  16  and the joint  22 , with the exit section  24  having the clockwise (in FIG. 5) 90° bend followed by a counterclockwise (in FIG. 5) 45° bend to the nozzle  28 . Otherwise, however, the embodiment of FIGS. 5 and 6 works in the same way as the embodiment of FIGS. 1-4. It is, however, preferable from a torque point of view because the nozzle  28  in this embodiment is nearer to the joint  16  in the direction of the axis  20  than in the embodiment of FIGS. 1-4. 
     It will be seen from FIGS. 1 and 5 that the modular construction of the inventive device with 45° bends, 90° bends, and straight pieces/joints allows the inventive device to be arranged in several different configurations to suit particular applications. In all of these configurations, however, turbulence is minimized by the gradual curvature of the water conduit and the unbroken smooth interior wall of the water conduit. The straight pieces such as  29  in FIG. 1 form a counterpart to a joint such as  22  to maintain the ability of axes  20  and  37  to become coaxial in the FIG. 1 position. 
     The novel geometry of the inventive monitor presents some control issues not encountered in the prior art. Specifically, for example, in a vertically mounted monitor, a transition of the nozzle  28  from a horizontal to a vertical orientation while remaining in the same vertical plane  50  (FIG. 8) requires a coordinated simultaneous rotation of both the joint  22  and the joint  16 . Thus, in FIG. 8, if the home position of the nozzle  28  is coaxial to the intersection of horizontal plane  52  and vertical plane  50 , a transition of the nozzle  28  in the vertical plane  50  from horizontal to vertical requires a simultaneous rotation of the joints  22  and  16  in accordance with the trigonometrically derived formulas 
     
       
           T =arccos {(1/sin 2   M )*(cos 2   M −sin E )}  (1) 
       
     
     
       
           B =arctan {sin T /[cos M *(1+cos T )]}  (2) 
       
     
     wherein E is a desired elevation angle above the horizontal plane  52 ; M is the inclination of the axis  26  of the joint  22  with respect to the axis  20 ; T is the required rotation angle of joint  22 ; and B is the required rotation angle of joint  16 . 
     In order to aim the nozzle  28  at the elevation E in any vertical plane  54  other than the plane  50 , the desired azimuth angle A is simply added to the rotation required by formula (2), so the total rotation R of joint  16  is 
     
       
           R=B+A   (3) 
       
     
     For the simplest case in which M=45° (and consequently sinM equals cosM), formula (1) reduces to 
     
       
           T =arccos {1−(sin E /sin 2   M )}  (4) 
       
     
     For elevation changes in 5° increments, formula (4) yields the following look-up table for a nozzle transition from horizontal to vertical in plane  50  of FIG.  8 : 
     
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE I 
               
               
                   
               
               
                 Elevation (degrees) 
                 Joint 22 (degrees) 
                 Joint 16 (degrees) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0 
                 0 
                 0 
               
               
                 5 
                 34 
                 24 
               
               
                 10 
                 49 
                 33 
               
               
                 15 
                 61 
                 40 
               
               
                 20 
                 72 
                 46 
               
               
                 25 
                 81 
                 50 
               
               
                 30 
                 90 
                 55 
               
               
                 35 
                 98 
                 59 
               
               
                 40 
                 107 
                 62 
               
               
                 45 
                 114 
                 66 
               
               
                 50 
                 122 
                 69 
               
               
                 55 
                 130 
                 72 
               
               
                 60 
                 137 
                 74 
               
               
                 65 
                 144 
                 77 
               
               
                 70 
                 152 
                 80 
               
               
                 75 
                 159 
                 82 
               
               
                 80 
                 166 
                 85 
               
               
                 85 
                 173 
                 87 
               
               
                 90 
                 180 
                 90 
               
               
                   
               
             
          
         
       
     
     It will be seen that the rotation of neither joint is linear, with the rotations for each 5° interval being greatest near the horizontal and diminishing toward the vertical. 
     The positioning and tracking of the nozzle  28  may readily be accomplished automatically through the use of a microprocessor  56  (FIG.  7 ). The inputs  58 ,  60  to the microprocessor  56  are the desired values, respectively, of elevation and azimuth. These may be generated manually, preferably digitally, by a keyboard or joystick. Alternatively, they may be generated by a computer program programmed to move the nozzle  28  in a desired predetermined pattern or in response to an operator&#39;s or sensor&#39;s instructions. 
     By means of a look-up table  61  such as Table I above, or by means of direct computation from formulas (1) through (4) above, the microprocessor  56  first computes at  62  a joint- 22  position signal  64  that represents the rotational position of joint  22  which will produce the desired elevation, and outputs that signal to the servomotor  36 . Based on the input  58  or the signal  64 , the microprocessor  56  then computes at  63  the compensatory rotation of joint  16  that is necessary to maintain the nozzle  28  in the vertical home plane  50  at the chosen elevation. The resulting signal  66  is then added in adder  68  to the signal  60  representing the chosen azimuth to produce the joint- 16  position signal  70  that is applied to servomotor  34 . Position feedback signals  72 ,  74  from the servomotors  34 ,  36  may be used to correct any unintended rotation of the joints  22 ,  16  as a result of torque transients in the water stream or other causes. 
     The feedback signals  72 ,  74  may be generated in a variety of ways. For example, a potentiometer or other analog device, an optical encoder, or a Hall effect sensor or other pulse counter, may be used on either a motor or a joint. 
     The motors  34 ,  36  may of course be operated manually by a joystick or similar device. Because of the interrelationship of the rotations of joints  22  and  16 , however, accurate manual handling of the monitor  10  with a joystick is likely to require skill and experience. 
     Another way of manually handling the joints  16 ,  22  in the absence of any motors (or handling motors by incremental-rotation pulsing) relies on a corollary of Table I. If the joint  10  is equipped e.g. with equidistant markings or detent notches around its circumference, the joint  22  can be equipped with corresponding non-equidistant notches or markings that are increasingly farther apart as nozzle  28  approaches the horizontal in FIG.  8 . The rotational increments between the markings are so calculated that a rotation of joint  22  from one of its non-equidistant marks to the next requires a compensating movement of joint  16  from one of its equidistant marks to the next. Thus, joint  16  may first be moved to point the nozzle  28  in a desired azimuth direction. Then, if the elevation is changed by moving joint  22  by e.g. three marks, joint  16  need merely also be moved three marks to maintain the nozzle  28  in the same azimuth direction. 
     It will be understood that the embodiments of the invention described herein are only illustrative, and that the invention may be carried out in a variety of different ways without departing from the scope of the following claims.