GB2023879A - Hoisting apparatus - Google Patents

Abstract

Hoisting apparatus for moving an object (e.g. a basketball goal) between two positions comprises an AC motor 1 energisable through contactor 12 or 13 to move the object up or down, relays 7, 11 whose contacts 7a, 11a respectively energise contactor coils 12a 13a through respective limit switches 16, 17, a timer 14 and thermal relay 15, and further relays 2, 37, 3, 38 in a tenser 30 responsive to raising or lowering signals of different frequency produced by a remote optical command signal generator 20, the closing delay of timer 14 being sufficient to prevent energisation of coil 12a, 13a by transient closure of relays 2, 3 (e.g. due to vibration), sustained closure of relay 2 or 3 energises relay 7 or 11 through thyristor 6 or 10 to energise coil 12a or 13a after the timer delay and so close contactor 12 or 13 until switch 16 or 17 opens. In a modification, Figures 3 and 4 (not shown) using an ultrasonic command signal generator (200) the latter includes a switch (SW3) operable to deenergise the motor to stop the object during its movement. <IMAGE>

Description

SPECIFICATION Hoisting apparatus This invention relates to hoisting apparatus.

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 reasult 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.

In accordance with the present invention, there is provided a hoisting apparatus for moving an object between a first predetermined position and a second predetermined position, a reversible motor drivingly connected with object, and a circuit for operating the motor in one direction of rotation to move the object from the first predetermined position to the second predetermined position and to reverse the operation of the motor to move the object from the second predetermined position to the first position, a source of power, first coupling means connecting the motor to the source of power for rotation of the motor in the one direction for movement of the object from the first position to the second position, and second coupling means connecting the motor to the source of power for reversing the rotation of the motorfor movement of the object from the second position to the first position. A first switch means is interconnected between the motor and the first coupling means for electrically coupling the motor with the first coupling means when actuated, and a second switch means independent of the first switch means is interconnected between the motor and the second coupling means for electrically coupling the motor with the second coupling means when actuated.

Also provided are command signal generator adapted to generate command signals having different predetermined frequencies, and a command signal sensor responsive to a command signal transmitted from the command signal generator for actuating either of the first and second switch means. Time delay means is interconnected with the first and the second switch means and the first and the second coupling means to delay the connection between the first coupling means and the motor and the second coupling means and the motor to assure connection of the motor with the first or the second coupling means solely in response to a sustained actuation of the first or the second switch means.

In a preferred embodiment, the command signal generator is adapted to generate light beams modulated at different frequencies and the command signal sensor is adapted to be responsive to the light beam transmitted from the command signal generator for actuating either of the first and second switch means. The hoisting apparatus cannot become operative in response to any light beam becoming incident upon the command signal sensor as long as it has a frequency other than those specified levels.

In another preferred embodiment, the command signal generator is adapted to generate ultrasonic waves having different frequencies and the command signal sensor is adapted to be responsive to the ultrasonic wave transmitted from the command signal generator for acuating either of the first and second switch means. This arrangement is free from the influence of dust and vapor and permits a wider directional angle as compared to the first embodiment employing light beams.

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 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: Figure 1 is a circuit and block diagram showing a preferred embodiment of the present invention which utilizes modulated light beams to control the operation of the hoisting apparatus.

Figure 2 is a block diagram showing a modification of the command signal sensor used in the apparatus of Figure 2.

Figure 3 is a circuit and block diagram showing a part of preferred embodiment of the present invention which utilizes ultrasonic waves to control the operation of the hoisting apparatus.

Figure 4 is a circuit diagram showing a command signal generator used in the apparatus of Figure 3.

Description of the Preferred Embodiments Referring now to Figure 1 of the drawings, there is shown a hoisting apparatus according to the present invention which comprises a reversible electric motor 1 drivingly connected to a hoisting drum (not shown) for winding and unwinding a wire rope coupled to an object such as an athletic game goal or other objects. The hoisting apparatus may be mounted on a support member fixed to the ceiling of the gymnasium. The electric motor 1 is driven through a control circuit. The control circuit comprises first and second relay operated switches 2 and 3 having normally open contacts. The first relay switch 2 has its one contact connected to an AC power terminal 4 and the other contact connected through a variable resistor 5 to the gate of a first bidirectional triode thyristor 6.The first bidirectional thyristor 6 has its anode connected to the AC power terminal 4 and its cathode connected to one end of a first relay 7, the other end of which is connected to another AC power terminal.

In a similar fashion, the second relay switch 3 has its one contact connected to the AC power terminal 4 and the other contact connected through a variable resistor 9 to the gate of a second bidirectional triode thyristor 10. The anode of the thyristor 10 is connected to the AC power terminal 4 and the cathod thereof is connected to one end of a second relay 11, the other end of which is connected to the AC power terminal 8. The first relay 7 is operable to close a normally open contact 7a and open normally closed contacts 7b and 7bb when energized. The second relay 11 is operable to close a normally open contact 1 1a and open normally closed contacts 11 b and llbbwhen energized.

The control circuit comprises first and second electromagnetic contactors 12 and 13. The first electromagnetic contactor 12 has an operating coil 12a and normally opens contacts 1 2b to 12f, the normally open contact 12b serving as a self-holding contact. The second electromagnetic contactor 13 includes an operating coil 13a and normally open contacts 13b and 13f,the normally open contact 13b serving as a self-holding contact. The operating coil 1 2a of the first electromagnetic contactor 12 has its one end connected to the AC power terminal 8 through a timer circuit 14 and a thermal relay 15 and has the other end connected to the AC power terminal 4through a first limit switch 16 and the series arrangement of the normally open contact 7a of the first relay 7 and the normally closed contact 11 b of the second relay 11.The first limit switch 16 serves to cutoff power to the coil 1 2a in response to the object such as a basketball backboard rising to a first predetermined position.

The operating coil 13a of the second electromagnetic contactor 13 has its one end connected to the AC power terminal 8 through the timer circuit 14 and the thermal relay 15 and has the other end connected to the AC power terminal 4 through a second limit switch 17 and the series arrangement of the normally open contact 50a of the second relay 50 and the normally closed contact 7b of the first relay 7. The second limit switch 17 serves to cutoff power to the coil 13a in response to the object falling to a second predetermined position.

The timer circuit 14 may be comprised of any conventional time delay circuit which serves to maintain the first or second electromagnetic contactor coil 12a or 13a deenergized a predetermined time (several seconds in this embodiment) after the first or second relay operated switch 2 or 3 is closed to energize the first or second relay 7 or 11 thereby preventing a malfunction such that the control circuit does not become operative to drive the motor 1 in response to any vibration or the like which may instantaneously close the first or second relay operated switch 2 or 3. Therefore, any vibration is not effective to renderthe motor 1 operative. The thermal relay 15 serves to deenergize the coil 12a or 13a when the temperature of the motor 1 increases above a predetermined level.

The reversible electric motor 1 has four terminals 1 a to 1 d. The terminals 1 a and 1 b are connected to the AC power terminal 8 through the normally open contacts 1 2f and 1 2e of the first electromagnetic contactor 12 and the terminals lcand 1d connected to the AC power terminal 4 through the normally open contacts 1 2d and 1 2c thereof. Also, the terminals 1a and 1c of the electric motor 1 are connected to AC power terminal 8 through the normally open contacts 13f and 13e of the second electromagnetic contactor 13 and the terminals 1b and 1d are connected to the AC power terminal 4 through the normally open contacts 1 3d and 1 3c thereof.Thus, the contacts 1 2c and 1 2f are closed to supply power to the electric motor 1 so as to rotate it in one direction to lift the object when the first electromagnetic contactor 12 is energized, whereas the contacts 1 3c to 1 3f are closed to supply power to the electric motor 1 so as to rotate it in a reverse direction to lower the object when the second electromagneticcontactor 13 is energized.

The normally closed contact 7bb is connected between the one end of the second relay 11 and the terminal 1d of the electric motor 31 for holding the second relay 11 energized until the second limit switch 17 is rendered operative and is open to deenergize the second electromagnetic contactor 13.

The normally closed contact 11 bb is connected between the one end of the first relay 7 and the terminal 1d of the electric motor 1 for holding the first relay 7 energised until the first limit switch 16 becomes operative and is opened to deenergize the first electromagnetic contactor 12.

The reference numeral 20 designates a command signal generator comprising a luminous element 21 such as a light emission diode or the like, a drive circuit 22 for causing the luminous element 21 to generatoe a light beam, and an oscillator circuit 23 adapted to selectively generate a signal having a predetermined frequency and a signal having another predetermined frequency so as to modulate, at different frequencies, the light beam generated from the luminous element 21. The command light beam signal is transmitted to a command signal sensor generally designated at 30.The command signal sensor 30 comprises a light receiver 31 such as a photoelectric converting element for converting the comming light beam into an electric signal, an amplifier circuit 32 for amplifying the electric signal from the ligut receiver 31, two filters 33 and 34 each allowing the passage of an electric signal having a frequency specified therein, a rectifier circuit 35, a Schmitt circuit 36 for shaping the rectified electric signal, and first and second relays 37 and 38 responsive to the shaped electric signal from the Schmitt circuit 36 for actuating the respective relay switches 2 and 3. The command signal generator 20 is sized to be hold in one hand of the operator and the command signal sensor 30 may be mounted on a support member fixed to a ceiling of the gymnasium.

The operation of the hoisting apparatus of the present invention will now be described as it is used with a basketball goal. If the basketball goal 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 light beam having a predetermined frequency (for example,5KHz) may be continuously projected from the luminous element 21 of the command signal generator 1 onto the light receiver 31 of the command signal sensor 30 for a predetermined length of time sufficient to overcome the delay imparted by the timer circuit 14.The receiver element 31 converts the comming light beam into an electric signal which, turn, is amplified in the amplifier circuit 32, fed through the filter 33 allowing the passage of a5 KHZ frequency signal, rectified in the rectifier circuit 35, and shaped in the Schmitt circuit 36. The shaped electric signal energizes the relay 37 so as to close the relay operated switch 2 to render the first thyristor 6 conductive thereby energizing the first relay 7. As a result, the normally open contact 7a is closed to form a closed circuit including the normally closed contact 11 b, the normally open contact 7a, the first limit switch 16, the coil 12a of the first electromagnetic contactor 12, the timer circuit 14, and the thermal relay 15.Thus, the timer circuit 14 becomes conductive a predetermined time after the sustained energization of the first relay 37 to close the circuit to and to energize the coil 12a so as to close the normally open contacts 1 2b to 1 2f thereby supplying power to the electric motor 1 for rotation thereof in one direction to lift or raise the basketball goal out of the way with the contact 12b holding this state. At this time, the first relay 7 is held in circuit in its energized condition through the contact 1 2c and the contact 11 bb.When the basketball goal is lifted to and reaches a first predetermined or upper position, the first limit switch 16 detects this first predetermined position to break the closed circuit so that the first electromagnetic contactor 12 is deenergized to terminate the rotation of the electric motor 1.

On the other hand, when the basketball goal is in the upper position which is the same as the aforesaid first predetermined position and is requied to fall for playing basketball, the oscillator circuit 23 of the command signal generator 1 may be changed over so as to provide an output having the other frequency (for example, 10 KHz) to cause the luminous element 21 to produce a sustained light beam having a 10 KHz frequency toward the light receiver 31 of the command signal sensor 30 for the predetermined time. The receiver element 31 converts the comming beam into an electric signal which, in turn, is amplified in the amplifier circuit 32, fed through the filter 34 allowing the passage of a 10 KHZ frequency signal, rectified in the rectifier circuit 35, and shaped in the Schmitt circuit 36.The shaped electric signal energizes the relay 38 so as to close the relay operated switch 3 to render the second thyristor 10 conductive thereby energizing the second relay 11. As a result, the normally open contact 11 a is closed to form a close circuit including the normally closed contact 7b, the normally open contact 11 a, the second limit switch 17, the coil 13a of the second electromagnetic contactor 13, the timer circuit 14, and the thermal relay 15.Thus, the timer circuit 14, which includes the delay, becomes conductive a predetermined time after the sustained and continuous energization of the relay 38 to energize the coil 1 3a so as to close the normally open contacts 13bto 13ftherebysupplying powerto the electric motor 1 to rotate it in the reverse direction to lower the basketball gaol with the contact 13b holding this state. The delay in timer circuit 14 also prevents the energization of the coil 13a as a result of vibrations exerting on the relay operated switch 3. At this time, the second relay 11 is held through the contact 13c and the contact 7bb.

When the basketball goal is lowered to a second predetermined or lower position, the second limit switch 17 detects the arrival of the basketball goal into this position so as to break the closed circuit so that the second electromagneticcontactor 13 is deenergized to terminate the rotation of the electric motor 1.

Figure 2 illustrates a modification of the command signal sensor 30 in which the electric signal delivered from the first filter 33 is fed through a first rectifier circuit 35' and a first Schmitt circuit 36' to the relay 37 and also the electric signal delivered from the second filter 34 is fed through a second rectifier circuit 35" and a second Schmitt circuit 36" to the relay 38. The operation of Figure 2 embodiment is substantially similar to that described in connection with Figure 1 and will not be described further.

Referring now to Figures 3 and 4, there is illustrated an alternative embodiment of the hoisting apparatus of the present invention which is substantially similar to that of the first described embodiment except for the command signal generator and the command signal sensor arrangement. In this embodiment, the command signal generator is generally designated at 200 which comprises an LC oscillator circuit 201 including a coil Land a capacitor C1 for producing an ultrasonic wave having a predetermined frequency, a frequency changing circuit 202 including capacitors C2 to C4 having different capacity values and switches SW1 to SW3 connected to series to the respective capacitors C2 to C4 for coupling the respective capacitors C2 to C4 in parallel with the capacitor C1 when closed, and a transmitter circuit 203 including a speaker SP and a coupling capacitor C5 interconnected between the speaker SP and one end of the capacitor Cl. The command signal generator 200 is sized to be held in one hand of the operator.

In this embodiment, the command signal sensor which is generally designated at 300 comprises a receiver element 301 such as a microphone for converting the comming ultrasonic wave into an electric signal, an amplifier circuit 302 for amplifying the signal from the receiver element 301, a synchronous timer 303, first to fourth signal discrimination circuit 304 to 307 each allowing the passage of a signal having a frequency specified therein, first to fourth amplifier circuits 308 to 311 for amplifying the signals from the respective discrimination circuits 304to 307, and firstto fourth relays 312 to 315 responsive to the signals from the respective amplifier circuits 308 to 311 for actuating the relay switches 316,2,3 and 317. The relay switch 316 is interconnected between the source of power and the AC terminal 4 for applying power when the relay 312 is energized to close the relay switch 316, and the relay switch 317 is interconnected between the AC terminal 8 and the first and the line leading to the first and second electromagnetic contactors 12 and 13 for terminating rotation of the motor 1 in the course of upward or downward movement of the basketball goal when the relay 315 is energized to open the relay switch 317.

The operation of the hoisting apparatus of this embodiment is as follows: First, an ultrasonic wave having a frequency determined by the capacitor C1 and the coil L is transmitted from the command signal generator 200 to the receiver element 301 of the command signal sensor 300. The receiver element 301 converts the comming ultrasonic wave into an electric signal which, in turn, is fed through the amplifier circuit 302, the synchronous timer 303, the first signal discrimination circuit 304, and the first amplifier circuit 308 to the relay 302 to energize it so as to close the relay switch 316 to couple power to the AC terminal 4.If the basketball goal 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, the switch SW1 of the frequency changing circuit 202 may be closed so as to connect the capacitor C2 in parallel to the capacitor C1 to reduce the frequency of the ultrasonic wave generated from the transmitter circuit 203. The receiver element 301 of the command signal sensor 300 converts the comming ultrasonic wave into an electric signal which, in turn, is fed through the amplifier circuit 202, the synchronous timer 303, the second signal discriminating circuit 305, and the second amplifier circuit 300 to the relay 313 to energize it so as to close the relay switch 2.As a result, the basketball goal is lifted until it reaches the first predetermined position in the same manner as described in connection with the first embodiment.

When the basketball goal is in the upper position or the first predetermined position and is required to fall for playing basketball, the switch SW2 of the frequency changing circuit 202 of the command signal generator 200 is closed so as to connect the capacitor C3 in parallel to the capacitor C1 to change the frequency of the ultrasonic wave generated from the transmitter circuit 203 to a predetermined level.

The transmitted ultrasonic wave is received and converted into an electric signal by the receiver element 301 of the command signal sensor 300. The electric signal is fed through the amplifier circuit 302 and the synchronous timer 303, the third signal discrimination circuit 307, the third amplifier circuit 310 to the relay 314 to energize it so as to close the relay switch 3. As a result, the basketball goal is lowered until it reaches the second predetermined position in the same manner as described in connection with the first embodiment.

If the basketball goal is required to be stopped in the course of its upward or downward movement, the switch SW3 may be closed so as to connect the capacitor C4 in parallel to the capacitor C1 to change the frequency of the ultrasonic wave generated from the transmitter circuit 203. The receiver element 301 of the command signal sensor 300 converts the comming ultrasonic wave into an electric signal which, in turn, is fed through the amplifier circuit 302, the synchronous timer 303, the fourth signal discriminating circuit 307, and the fourth amplifier circuit 311 to the relay 315 to energize it so as to open the relay switch 317 thereby decoupling power to the motor 1 to stop its rotation.

Although the present invention has been described in connection with a hoisting apparatus for moving a basketball goal into its usable position and to remove it therefrom, the hoisting apparatus of 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 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.

Claims (17)

1. In a hoisting apparatus for moving an object between a first predetermined position and a second predetermined position, a reversible motor drivingly connected with the object, and a circuit for operating the motor in one direction of rotation to move the object from the first predetermined position to the second predetermind position and to reverse the operation of the motor to move the object from the second predetermined position to the first position, a source of power, first coupling means connecting the motor to the source of power for rotation of the motor in the one direction for movement of the object from the first position to the second position, and second coupling means connecting the motor to the source of power for reversing the rotation of the motor for movement of the object from the second position to the first position, the improvement comprising:: a first switch means interconnected between said motor and said first coupling means for electrically coupling said motor with said first coupling means when actuated; a second switch means independent of said first switch means, said second switch means being interconnected between said motor and said second coupling means for electrically coupling said motor with said second coupling means when actuated; a command signal generator adapted to generate command signals having different predetermined frequencies; a command signal sensor responsive to a command signal transmitted from said command signal generator for actuating either of said first and second switch means; and, time delay means interconnected with said first and said second switch means and said first and said second coupling means to delay the connection between said first coupling means and said motor and said second coupling means and said motor to assure connection of said motor with said first or said second coupling means solely in response to a sustained actuation of said first or said second switch means.

2. In the hoisting apparatus as claimed in claim 1, wherein said command signal generator is adapted to generate modulated light beams having different predetermined frequencies and said command signal sensor is adapted to actuate either of said first and said second switch means in response to one of the light beams.

3. In the hoisting apparatus as claimed in claim 2, said command signal generator comprises a luminous element, a drive circuit for causing said luminous element to generate a light beam, and an oscillator circuit selectively generating signals having different frequencies so as to modulate at different frequencies, the light beam to be generated from said luminous element.

4. In the hoisting apparatus as claimed in claim 2, wherein said command signal sensor comprises a photoelectric converter element for converting the comming light beam into an electric signal, an amplifier for amplifying the electric signal from the converter element, two filters each allowing the passage of an electric signal having a frequency specified therein, a second amplifier for amplifying the electric signal from one of said filters, a Schmitt circuit for shaping the electric signal from said second amplifier, and two relays one of which is responsive to the electric signal from said Schmitt circuit for actuating the corresponding switch means.

5. In the hoisting apparatus as claimed in claim 2, wherein said command signal sensor comprises a photoelectric converting element for converting the comming light beam into an electric signal, a first ampliferfor amplifying the electric signal from said converting element, two filters each allowing the passage of an electric signal having a frequency specified therein, second and third amplifiers for amplifying the electric signals from said respective filters, two Schmitt circuit for shaping the electric signals from said respective amplifiers, and two relays responsive to the electric signals from said respective Schmitt circuits for actuating said respective switch means.

6. In the hoisting apparatus as claimed in claim 1, wherein said command signal generator is adapted to generate ultrasonic waves having different predetermined frequencies and said command signal sensor is adapted to actuate either of said first and second switch means in response to one of the ultrasonic waves.

7. In the hoisting apparatus as claimed in claim 6, wherein said command signal generator comprises an oscillation circuit including a coil and a first capacitor for producing an ultrasonic wave having a predetermined frequency, a frequency changing circuit including capacitors having a different capacity values and switches connected in series to said respective capacitors for coupling said respective capacitors in parallel with said first capacitor when closed, and a transmitter circuit including a speaker and a coupling capacitor interconnected between said speaker and one end of said first capacitor.

8. In the hoisting apparatus as claimed in claim 6, wherein said command signal sensor comprises a receiver element for converting a comming ultrasonix wave into an electric signal, an amplifierfor amplifying the electric signal from said receiver element, a synchronous timer, two discrimination circuits each allowing the passage of a signal having a frequency specified therein, two amplifier circuits for amplifying the signals from said respective discrimination circuits, and two relays responsive to the signals from said respective amplifier circuits for actuating said first and said second relay switches, respectively.

9. In the hoisting apparatus as claimed in claim 6, wherein said command signal sensor comprises a receiver element for converting a comming ultrasonix wave into an electric signal, an amplifierfor amplifying the electric signal from said receiver element, a synchronous timer, four discrimination circuits each allowing the passage of a signal having a frequency specified therein, four amplifier circuits for amplifying the signals from said respective discrimination circuits, and four relays responsive to the signals from said respective amplifier circuits for actuating a normally open relay switch to couple power to said apparatus, said first relay switch, said second relay switch, and a normally closed relay switch to decouple power to said apparatus, respectively.

10. In the hoisting apparatus as claimed in claim 1, including first and second limiting means coupled with said first and said second coupling means, respectively, said first and said second limiting means being responsive to said object reaching said first and said second predetermined positions, respectively, for rendering said first and said second coupling means inoperative to connect said motorto said power source.

11. In the apparatus as claimed in claim 1, wherein said first coupling means and said second coupling means each includes an operating coil in circuit with said time delay means, a normally open switch in circuit with said time delay means, and a plurality of normally open contacts when in their closed condition connecting said motor with said source of power and when in their open condition disconnecting said motor from said source of power and said normally open switch of each said first and said second coupling means being a self-holding contact.

12. In the apparatus as claimed in claim 11, including a thermal relay in circuit with both said selfholding contacts, said thermal relay being adapted to open upon the temperature of said motor reaching a predetermined temperature to deenergize the operating coils of said first and said second coupling means.

13. In the apparatus as claimed in claim 1, wherein said first coupling means includes a first switch means, coupled to said motor and said time delay device for rotation of said motor in a first direction upon activation and a first relay means in circuit with said motor and said second coupling means to control the connection of said motor with said first switch means and prevent connection to said second switch means and said second coupling means includes a second switch means coupled to said motor and said delay means for rotation of said motor in a direction reverse to said first direction upon activation and a second relay means in circuit with said first coupling means to disconnect said first switch means from said first photosensitive energy device.

14. In the apparatus as claimed in claim 13, wherein said first relay means includes a pair of normally closed contacts in circuit with said second photosensitive energy responsive device and said second switch means which upon energization of said first photosensitive energy responsive device is opened and decouples said second switch means from said second photosensitive energy responsive device, and a normally open contact in circuit between said first switch means and said first photosensitive energy responsive device to couple said first switch means through said time delay means to said first photosensitive energy responsive device, and said second relay means includes a pair of normally closed contacts and a normally open contact, said last-mentioned normally closed contacts being in circuit with said first photosensitive energy responsive device and said first switch means and being opened upon energization of said second photosensitive device to decouple said first switch means from said first photosensitive device, said last-mentioned normally open contact being closed upon energization of said second photosensitive energy responsive device to couple said second switch means with said second photosensitve device through said time delay means.

15. In the apparatus as claimed in claim 13 or 14, including an upper limit control switch in circuit with said first switch means to disconnect said first switch means and said motor for stopping thereof when said object reaches said first predetermined position, and a lower limit control switch in circuit with said second photosensitive energy device and said second switch means to disconnect said second switch means and said motor for stopping thereof when said object reaches said second predetermined position.

16. In the apparatus as claimed in claim 13 or 14, including means interconnected with said first and second coupling means responsive to the temperature of said electric motor and operable to decouple said first and said second coupling means from said motor when the temperature thereof is above a predetermined level.

17. Hoisting apparatus substantially as hereinbefore described and as illustrated in the accompanying drawings.