Abstract:
A hoisting apparatus and a control circuit therefor comprising a reversible electric motor drivingly connected to a hoisting drum for hauling an object up and down. The control circuit includes first and second photosensitive elements each responsive to a light beam for initiating rotation of the electric motor in either direction and means for terminating rotation of the electric motor.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a hoisting apparatus operable in response to optical remote control for moving an object such as an athletic game goal or other objects up and down or from a first to a second position. 
     2. Description of the Prior Art 
     In playing a ball game in a gymnasium, it is often necessary to remove the ball game goals and nets for other types of ball games out of the ball game zone. This is especially true for a basketball goal which is hung down from the ceiling of the gymnasium. In view of the above and other considerations, several systems have been proposed which include remote control means for permitting upward and downward movement of the basketball goal. However, such prior art systems have been found to be disadvantageous as they require a control board and wire cords connecting the control means and result in a system which is expensive and difficult to install. 
     Accordingly, a need has been recognized for a new and improved hoisting apparatus for hauling the basketball goal up and down. 
     SUMMARY OF THE INVENTION 
     Thus, it is a general object of the present invention to provide a new and improved hoisting apparatus which avoids or eliminates many of the limitations and drawbacks inherent in previous designs. 
     Another object of the present invention is to provide a hoisting apparatus which is relatively simple and inexpensive in design. The present invention eliminates the requirement for the control board and wire cords employed in conventional designs. 
     Still another object of the present invention is to provide a hoisting apparatus which is easy to install and controllable in a position where the operator can view the object. 
     In accordance with the present invention, there is provided a hoisting apparatus for hauling up and down an object which comprises a reversible electric motor drivingly connected to a hoisting drum for winding and unwinding a wire rope having its free end connected to the object. The hoisting apparatus also comprises a control circuit which includes first and second photosensitive elements each operated responsive to a light beam for initiating operation of respective first and second switching means so as to connect the electric motor to a source of power thereby rotating it in either direction. Such operation of the switching means is deferred a predetermined time after the photosensitive element is operated and also is terminated when the object reaches a predetermined position. The operation of the switching means is held until the object reaches the predetermined position. 
     Other objects and advantages of the present invention will become apparent to those skilled in the art from a consideration of the following detailed description of one exemplary embodiment of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following description of the present invention is had in conjunction with the accompanying drawings, in which like reference characters refer to the same or corresponding parts, and wherein: 
     FIG. 1 is a perspective view showing a motor driven basketball backboard hanging mechanism with which the hoisting apparatus of the present invention is associated, 
     FIGS. 2A and 2B are elevational and side views of the mechanism of FIG. 1, 
     FIGS. 2C and 2D are enlarged elevational and side views showing the guide roller unit employed in the mechanism, and 
     FIG. 3 is a circuit diagram showing the hoisting apparatus made in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made to the drawings which depicts illustratively in more detail the significant portions of the hoisting apparatus of the present invention. 
     The present invention is contemplated for use in conjunction with a basketball backboard hanging mechanism as shown in FIGS. 1 and 2. While the basketball backboard hanging mechanism itself does not form a part of the present invention, it is illustrated to provide a point of reference for the present invention in a practical environment. 
     A basketball backboard hanging mechanism 1 is shown as including a first frame structure 2 composed of a pair of side members 3 extending vertically in spaced relation and cross bars 4 extending between the side members 3 in longitudinally spaced relation and secured at their opposite ends to the side members 3 by means of clamps 5. The first frame structure 2 supports at its lower portion a basketball backboard 6 provided centrally with a goal or basket 7. A guide rail 8 is attached by means of clamps 9 to the rear side of each of the side members 3. The mechanism 1 also includes a second frame structure 10 composed of a pair of stay members 11 extending in parallel spaced relation and cross bars 12 extending between the stay members 11 in longitudinally spaced relation. A slider 13 is provided at the lower end of each of the stay members 11 which is best shown in FIGS. 2C and 2D as including four rollers 14 journalled on respective shafts 15 such as to hold one of the guide rails 8 for sliding movement along it. The mechanism 1 further includes a third frame structure 16 of a rectangular parallelipiped shape which has upper ends 17 embedded in the ceiling of the gymnasium, a horizontal rod 18 to which the upper ends of the side members 3 of the first frame structure 2 are connected by pivotal connections 19, and another horizontal rod 20 to which the upper ends of the stay members 11 of the second frame structure 10 are connected by pivotal connections 21. 
     A wire rope 22 extends from one of the cross bars 4 to a pulley 23 and another wire rope 24 extends from one of the cross bars 12 through the pulley 23 and another pulley 25 hung from the ceiling to a hoisting drum (not shown) connected to an electric motor contained in an hoisting apparatus 30 as will be described later. When the electric motor is placed in operation to pull the wire rope 22 in the direction indicated by the arrow A, the first and second frame structures 2 and 10 rotate in the clockwise direction about their pivotal connections with the sliders 13 sliding along the respective guide rails 8 so that the first frame and second frame structures 2 and 10 are placed in a horizontal position as shown by the phantom lines of FIG. 2B. Such lifting of the basketball backboard 6 is accomplished by projecting a light beam for a predetermined time from a projector 26 to a first photosensitive element 41 as will be described in detail later as shown in FIG. 1. A light beam may be projected for a predetermined time from the projector 26 to a second photosensitive element 42 to be described later if the basketball backboard 6 is required to fall. 
     As noted above, the basketball backboard hanging aspects of the present disclosure do not constitute a portion of the inventive concept herein disclosed. For example, any mechanism may be used to support the basketball backboard for swinging movement. 
     Referring now to FIG. 3, there is illustrated a hoisting apparatus designated generally by the reference numeral 30 and placed on the third frame structure 16 fixed to the ceiling of the gymnasium. The hoisting apparatus 30 comprises a reversible electric motor 31 drivingly connected to a hoisting drum (not shown) for winding and unwinding the wire rope 22. The electric motor 31 is driven through a control circuit. The control circuit comprises first and second photosensitive elements 41 and 42 such as photoconductive cells (CdS) or the like which are provided with a hood for shading unnecessary light beams. The first photosensitive element 41 has its one end connected to an AC power terminal 43 and the other end connected through a variable resistor 45 to the gate of a first bidirectional triode thyristor 47 (referred also to as a &#34;triac&#34;). The bidirectional thyristor 47 has its anode connected to the AC power terminal 43 and its cathode connected to one end of a first relay 49, the other end of which is connected to another AC power terminal 44. In a similar fashion, the second photosensitive element 42 has its one end connected to the AC power terminal 43 and the other end connected through a variable resistor 46 to the gate of a second bidirectional triode thyristor 48. The anode of the thyristor 48 is connected to the AC power terminal 43 and the cathode thereof is connected to one end of a second relay 50, the other end of which is connected to the AC power terminal 44. The first relay 49 is operable to close a normally open contact 49a and open normally closed contacts 49b and 49bb when energized. The second relay 50 is operable to close a normally open contact 50a and open normally closed contacts 50b and 50bb when energized. 
     The control circuit comprises first and second electromagnetic contactors 51 and 52. The first electromagnetic contactor 51 has an operating coil 51a and normally open contacts 51b to 51f, the normally open contact 51b serving as a self-holding contact. The second electromagnetic contactor 52 includes an operating coil 52a and normally open contacts 52b to 52f, the normally open contact 52b serving as a self-holding contact. The coil 51a of the first electromagnetic contactor 51 has its one end connected to the AC power terminal 44 through a timer circuit 53 and a thermal relay 54 and has the other end connected to the AC power terminal 43 through a first limit switch 55 and the series arrangement of the normally open contact 49a of the first relay 49 and the normally closed contact 50b of the second relay 50. The first limit switch 55 serves to cut off power to the coil 51a in response to the basketball backboard 6 rising to a first predetermined position. 
     The coil 52a of the second electromagnetic contactor 52 has its one end connected to the AC power terminal 44 through the timer circuit 53 and the thermal relay 54 and has the other end connected to the AC power terminal 43 through a second limit switch 56 and the series arrangement of the normally open contact 50a of the second relay 50 and the normally closed contact 49b of the first relay 49. The second limit switch 56 serves to cut off power to the coil 52a in response to the basketball backboard 6 falling to a second predetermined position. 
     The timer circuit 53 may be comprised of any conventional time delay circuit which serves to maintain the first or second electromagnetic contactor coil 51a or 52a deenergized a predetermined time (several seconds in this embodiment) after the first or second photosensitive element 41 or 42 is operated to energize the first or second relay 40 or 50, thereby preventing a malfunction such that the control circuit does not become operative to drive the motor 31 in response to any unspecified or unwanted light beam which may instantaneously become incident upon the first or second photosensitive element 41 or 42. Therefore, any extraneous unwanted light which impinges onto the photosensitive elements 41 or 42 is not effective to render motor 31 operative. The thermal relay 54 serves to deenergize the coil 51a or 52a when the temperature of the motor 31 increases above a predetermined level. 
     The reversible electric motor 31 has four terminals 31a to 31d. The terminals 31a and 31b are connected to the AC power terminal 44 through the normally open contacts 51f and 51e of the first electromagnetic contactor 51 and the terminals 31c and 31d connected to the AC power terminal 43 through the normally open contacts 51d and 51c thereof. Also, the terminals 31a and 31c of the electric motor 31 are connected to the AC power terminal 44 through the normally open contacts 52f and 52e of the second electromagnetic contactor 52 and the terminals 31b and 31d are connected to the AC power terminal 43 through the normally open contacts 52d and 52c thereof. Thus, the contacts 51c to 51f are closed to supply power to the electric motor 31 so as to rotate it in one direction to lift the basketball backboard when the first electromagnetic contactor 51 is energized, whereas the contacts 52c  to 52f are closed to supply power to the electric motor 31 so as to rotate it in a reverse direction to lower the basketball backboard when the second electromagnetic contactor 52 is energized. 
     The normally closed contact 49bb is connected between the one end of the second relay 50 and the terminal 31d of the electric motor 31 for holding the second relay 50 energized until the second limit switch 56 is rendered operative and is opened to deenergize the second electromagnetic contactor 52. The normally closed contact 50bb is connected between the one end of the first relay 49 and the terminal 31d of the electric motor 31 for holding the first relay 49 energized until the first limit switch 55 becomes operative and is opened to deenergize the first electromagnetic contactor 51. 
     The operation of the hoisting apparatus of the present invention will now be described as it is used with a basketball backboard hanging mechanism as shown in FIGS. 1 and 2. 
     If the basketball backboard 6 is in its lower position, and it is required to rise to be moved away so as to permit the playing of another ball game, a continuous and sustained light beam may be continuously projected onto the first photosensitive element 41 from projector 26 for a predetermined length of time sufficient to overcome the delay imparted by the timer circuit 53, as shown by the phantom lines of FIG. 1. This causes a reduction in the resistance of the first photosensitive element 41 so as to render the first thyristor 47 conductive to energize the first relay 49. As a result, the normally open contact 49a is closed to form a closed circuit including the normally closed contact 50b, the normally open contact 49a, the first limit switch 55, the coil 51a of the first electromagnetic contactor 51, the timer circuit 53, and the thermal relay 54. Thus, the timer circuit 53 becomes conductive a predetermined time after the sustained actuation of the first photosensitive element 41 to close the circuit to and to energize the coil 51a so as to close the normally open contacts 51b to 51f thereby supplying power to the electric motor 31 for rotation thereof in one direction to lift or raise the basketball backboard 6 out of the way with the contact 51b holding this state. At this time, the first relay 49 is held in circuit in its energized condition through the contact 51c and the contact 5bb. When the basketball backboard 6 is lifted to and reaches a first predetermined position such as the horizontal position shown by the phantom lines of FIG. 2B, the first limit switch 55 detects this first predetermined position to break the closed circuit so that the first electromagnetic contactor 51 is deenergized to terminate the rotation of the electric motor 31. 
     On the other hand, when the basketball backboard 6 is in the horizontal position which is the same as the aforesaid first predetermined position and is required to fall for playing basketball, a sustained light beam may be continuously projected for the predetermined time from the projector 26 onto the second photosensitive element 42 as shown by the solid lines of FIG. 1. This causes a reduction in the resistance of the second photosensitive element 42 to render the second thyristor 48 conductive to energize the second relay 50. As a result, the normally open contact 50a is closed to form a closed circuit including the normally closed contact 49b, the normally open contact 50a, the second limit switch 56, the coil 52a of the second electromagnetic contactor 52, the timer circuit 53, and the thermal relay 54. Thus, the timer circuit 53, which includes the delay, becomes conductive a predetermined time after the sustained and continuous actuation of the second photosensitive element 42 to energize the coil 52a so as to close the normally open contacts 52b to 52f thereby supplying power to the electric motor 31 to rotate it in the reverse direction to lower the basketball backboard 6 with the contact 52b hold this state. The delay in timer circuit 53 also prevents the energization of coil 52a as a result of extraneous or unwanted light energy impinging onto the second photosensitive element 42. At this time, the second relay 50 is held through the contact 52c and the contact 49bb. When the basketball backboard 6 is lowered to a second position such as the vertical predetermined position shown by the solid lines of FIG. 2B, the second limit switch 56 detects the arrival of the backboard 6 into this position so as to break the closed circuit so that the second electromagnetic contactor 52 is deenergized to terminate the rotation of the electric motor 31. 
     With the above described hoisting apparatus, the basketball backboard can be securely hauled up or down merely by continuously projecting a light beam onto the first or second photosensitive element for a predetermined time. The hoisting apparatus cannot become operative in response to any instantaneous or undesired light beam becoming incident upon the photosensitive element because of the delay imparted as a result of the function of the timer circuit. 
     The hoisting apparatus also cannot be rendered operative in response to energization of both the photosensitive elements 41 and 42 simultaneously, as both normally closed contacts 49bb and 50bb would be opened. There is no need for any control board and wire cords connecting the control board and the apparatus. The hoisting apparatus of the present invention is simple, inexpensive, and easy to install. 
     Although the present invention has been described in connection with a hoisting apparatus for moving a basketball backboard into its usable position and to remove it therefrom, the hoisting apparatus fo the present invention can be used with other athletic game goals, nets and other objects which have to be removed or restored. 
     While the present invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present invention.