Hoisting device for lighting fixture

Abstract: A device for mounting a lighting fixture to a high ceiling comprises a casing ( 10 ) incorporating an electric motor with a rotating drum. A loader ( 30 ) carrying the lighting fixture is suspended from the casing ( 10 ) by means of a wire ( 40 ) having a first end fixed to the drum and a second end fixed to the casing ( 10 ). The wire extends from the drum to pass round first and second pulleys within the casing, descends from the second pulley to pass round pulleys ( 31 , 32 ) in loader ( 30 ), and ascends back to the casing ( 10 ) to terminate at the second end such that winding and unwinding of the wire ( 40 ) on and from the drum lifts and lowers the loader ( 30 ) together with the lighting fixture. The casing ( 10 ) is provided in its bottom with a recess ( 14 ) which receives the loader ( 30 ) and which has an electrical connector for feeding electricity to the lighting fixture. The second end of the wire ( 40 ) is anchored to the casing ( 10 ) by means of a bearing ( 41 ) which comprises a first member ( 42 ) mounted to the casing and a second member ( 43 ) rotatable relative to the first member ( 42 ) and holding the second end of the wire ( 40 ) to release any twisting of the wire ( 40 ).

Description: TECHNICAL FIELD The present invention is directed to a hoisting device, and more particularly to a device for mounting the lighting fixture to the ceiling of a building and capable of lifting and lowering the lighting fixture. BACKGROUND ART When a lighting fixture is mounted on a high ceiling of a building such as a gymnasium or the like, a stepladder or ladder scaffold is necessary for maintenance of the lighting fixture, including the replacement of lamps. Such maintenance operation at a high elevation is difficult and dangerous. Therefore, it is desired to suspend the lighting fixture by the use of a wire such that the lighting fixture can be lowered to the floor for easy and safe maintenance. However, the use of the wire raises some problems in successfully and safely lifting and lowering the lighting fixture. The problems involve that the wire may twist during the lifting and lowering operation of the lighting fixture to such an extent to impede the winding and unwinding of the wire and eventually cause jamming of the wire as well as to wrongly orient the lighting fixture. From the DE-A-32 32 625, which discloses the features included in the preamble of attached claim 1, it is known a mounting device for a special type of lighting fixtures used for photographic purposes. These lighting fixtures have great dimensions, and the mounting device comprises at least a pair of hoisting devices so that the lighting fixture may be oriented in any desired manner. The US-A-4 234 165 discloses a luminaire lowering device for movement along a pole by a plurality of hoist cables. For preventing the cables from twisting and tangling during the raising and lowering operations, the hoist cables are secured by freely rotatable ball bearing devices. Accordingly, it is the object of the present invention to provide a device which is capable of eliminating the twisting of the wire and the lighting fixture for successfully lifting and lowering the lighting fixture. This object is solved by the device defined in attached claim 1. The device of the present invention provides additional features for easy installation and safe operation of the device. The present invention provides a device capable of avoiding the wire and the lighting fixture from twisting during the movement of the lifting and lowering the lighting fixture. The device in accordance with the present invention comprises a casing incorporating an electric motor with a rotating drum. The casing is adapted to be mounted to a ceiling of a building by means of a support member. A loader carrying the lighting fixture is suspended from the casing by means of a wire having a first end fixed to the drum and a second end fixed to the casing. The wire extends from the drum to pass round first and second pulleys within the casing, descends from the second pulley to pass round a pulley in loader, and ascends back to the casing to terminate at the second end such that winding and unwinding of the wire on and from the drum lifts and lowers the loader together with the lighting fixture towards and away from the casing. The casing is provided in its bottom with a recess which receives the loader and which has an electrical connector for feeding electricity to the lighting fixture. The second end of the wire is anchored to the casing by means of a bearing which comprises a first member mounted to the casing and a second member rotatable relative to the first member and holding the second end of the wire. With the use of the bearing, the twisting of the wire can be released by rotation of the second member relative to the first member of the bearing. The above object and other advantageous features of the present invention will become more apparent from the following detailed description of the invention when taken in conjunction with the attached drawings. BRIEF DESCRIPTION OF THE INVENTION FIG. 1 is a front view illustrating a hoisting device for a lighting fixture in accordance with a preferred embodiment of the present invention; FIG. 2 is a side view of the device; FIG. 3 is a top view of the device; FIG. 4 is a plan view illustrating the interior of a casing of the device; FIG. 5 is a sectional view taken along line 5-5 of FIG. 4; FIG. 6 is a sectional view taken along line 6-6 of FIG. 4; FIG. 7 is a sectional view illustrating a structure of supporting a free end of a wire utilized to suspend a loader in the above device; FIGS. 8A and 8B are explanatory views, respectively for installation of the device; FIG. 9 is a view illustrating a drum employed in the device; FIG. 10 is a sketch illustrating a manner in which a wire is wound around the drum; FIG. 11 is a plan view illustrating a relation between the drum and an associated pulley; FIG. 12 is a sectional view of the device illustrating a limit sensor for a loader carrying a lighting fixture; FIG. 13 is a perspective view of an electrical connector employed in the device for feeding electricity to the lighting fixture; FIG. 14 is a top view illustrating a mechanism of sensing slackening of the wire around the pulley; FIG. 15 is a view illustrating a mechanism of sensing a reverse winding of the wire; FIG. 16 is a view illustrating a mechanism of sensing a torsion of the lighting fixture about a vertical axis; FIGS. 17A and 17B are views illustrating the lighting fixture in a normal position and the associated operation of the mechanism, respectively; FIGS. 18A and 18B are views illustrating the lighting fixture in a twisted position and the associated operation of the mechanism, respectively; FIGS. 19A and 19B are views illustrating the lighting fixture in a half-turned position and the associated operation of the mechanism, respectively; FIGS.20A and 20B are views illustrating an overload sensing mechanism operating in a normal condition and in an overloaded condition, respectively; and FIG. 21 is a partial view illustrating another overload sensing mechanism. DESCRIPTION OF THE EMBODIMENT FIG. 1 illustrates a hoisting device of a lighting fixture in accordance with a preferred embodiment of the present invention. The device comprises a casing 10 installed on a building ceiling by a generally U-shaped support member 20 , and a loader 30 carrying the lighting fixture 1 and suspended from the casing 10 by means of a wire 40 . The lighting fixture 1 has an top attachment 2 by which it is held to the loader 30 . Accommodated in the casing 10 is an electric motor 50 for lifting and lowering the loader 30 together with the lighting fixture 1 . The casing 10 is of a flat rectangular configuration composed of a base 11 and a cover 12 . The support member 20 is of a generally U-shaped configuration with a web 21 and a pair of legs 23 . The web 21 has mount holes 22 through which screws (not shown) extends into the ceiling to secure the support member 20 to the ceiling. The leg 23 has an vertically elongate hole 24 through which bolts 25 extends into a hole in a bracket 13 at the opposite sides of the casing base 11 for supporting the casing 10 to the ceiling. As shown in FIGS. 8A and 8B, the casing 10 can be held horizontally even when installed to an inclined ceiling since the casing 10 can adjusts its position relative to the support member 20 by shifting the bolts 25 within the length of the elongate holes 24 and by pivoting the casing 10 about an axis of the bolts 25 . The base 11 is formed in its center with a recess 14 into which the loader 30 fits, as shown in FIG. 5. The motor 50 is mounted on the base 11 in a space on one side of a convex formed by the recess 14 . The motor 50 has an output shaft connected to rotate a drum 51 so as to wind and unwind the wire 40 on and from the drum. The drum 51 is rotatively fixed upon deenergization of the motor by a gear mechanism (not shown) in a motor housing to stop unwinding the wire 40 . The wire 40 extends generally horizontally from the drum 51 to pass round an end pulley 53 and a center pulley 55 , as shown in FIGS. 4 and 5, then goes down to the loader 30 in which the wire 40 passes round a spaced pair of pulleys 31 and 32 , as shown in FIG. 6, and returns into the casing where the wire 40 has its free end fixed to the base 11 by means of a thrust ball bearing 41 . As shown in FIG. 7, the bearing 41 comprises a lower race 42 mounted on the base 11 and an upper race 43 held rotatable relative to the lower race 42 . A tubular bushing 45 is inserted in a center opening of the bearing with a flange of the bushing 45 resting upon the upper race 43 so that the bushing 45 is rotatable together with the upper race 43 relative to the base 11 of the casing 10 . The wire 40 is provided at its free end with an anchor sleeve 46 which is clamped to the wire 40 and rests on the bushing 45 so that the free end of the wire 40 is anchored to the casing 10 . With this arrangement, the bearing 41 can absorb any twisting movement of the wire which appears during the operation of winding and unwinding the wire for lifting and lowering the lighting fixture 1 . As shown in FIGS. 9 and 10, a hub of the drum 51 is formed with a groove 52 for tightly winding the wire in rows and in a closely stacked manner. The end pulley 53 is supported about a shaft 54 , as shown in FIG. 11, and is movable in the axial direction of the shaft to give a minimum fleet angle α for guiding the wire 40 smoothly in and out of the groove 52 of the drum 51 when winding and unwinding the wire. The device includes a limit sensor 60 for the lifting movement of the loader 30 . The limit sensor 60 comprises a flat spring 62 of which one end projects into the recess 14 for abutment against the upper end of the loader 30 when the loader 30 is fully received in the recess 14 . When abutting against the upper end of the loader 30 , as shown in FIG. 12, the flat spring 62 resiliently deform so as to actuate an adjacent miniature switch 61 , which disconnects the motor 50 from a power source, thereby stop rotating the drum, i.e., winding the wire 40 . To this end, the miniature switch 61 is connected to give an output to a control circuit formed on a circuit board 56 which deenergize the motor 50 upon sensing that the loader 30 is lifted into the recess 14 . The casing 10 is provided in the bottom of the recess 14 with a set of electrical connectors 15 which come into contact with corresponding pins 33 on the upper end of the loader 30 when the loader 30 is fully received in the recess 14 , for feeding electricity to the lighting fixture 1 . The electrical connectors 15 are wired to a terminal 16 to which an external cable is connected for feeding the electricity to the electrical connectors. Another terminal 17 is provided to be connected to an external cable for energizing the motor 50 . The pins 33 of the loader 30 are connected to leads (not shown) routed through within the loader 30 for feeding electricity to the lighting fixture 1 . As shown in FIG. 12, the pin 33 is formed to have a ring contact for engagement with the connector 15 of the casing 10 . The ring contact is provided for the purpose of preventing the contact from being spoiled due to an arc developing upon disengaging the pin from the connector 15 , thereby avoiding conduction failure between the pin 33 and the connector 15 . Also included in the device is a loose sensor 70 which comprises, as shown in FIG. 14, the shaft 54 and a miniature switch 71 . The shaft 54 is supported between yokes 72 and 73 integrally upstanding from the base 11 of the casing 10 in a manner to extend through a round hole 74 in the yoke 72 and through an elongate hole 75 in the other yoke 73 . One end of the shaft 54 projecting out of the round hole 74 is connected to a coil spring 76 to be pulled towards the drum 51 , while the other end of the shaft 54 is freely movable in the elongate hole 75 so that the shaft 54 can pivot generally about the connection to the round hole 74 . The movable end of the shaft 54 projecting out of the elongate hole 75 is formed with an actuator 77 located in proximity to the miniature switch 71 . Due to the tension force applied to the wire 40 and therefore to the end pulley 53 , the shaft 54 is normally held in parallel with an axis of the drum 51 against the bias of the spring 76 in which condition the actuator 77 engages a button (not shown) of the miniature switch 71 . When the wire 40 is slackened as a result of that the loader 30 is lowered to reach the floor of the building or to be caught by a personnel, the shaft 54 is caused to pivot under the action of the coil spring 76 so as to be inclined with respect to the axis of the drum 51 , thereby releasing the actuator 77 from the button of the miniature switch 71 . Upon this occurrence, the miniature switch 71 outputs a signal to the control circuit which responds to stop rotating the motor 50 , i.e., stop unwinding the drum 51 , allowing the personnel to handle the lighting fixture 1 for maintenance thereof. The control circuit holds this condition until the personnel operates to lift the lighting fixture 1 . The device also includes a mechanism for avoiding reverse winding of the wire 40 . As shown in FIG. 15, the mechanism comprises a miniature switch 81 with an actuator 82 disposed between the drum 51 and the end pulley 53 . The actuator 82 is positioned in a path extending from the circumference of the hub of the drum 51 and the circumference of the end pulley 53 such that when the drum 51 still rotates after fully unwinding the wire, the wire 40 just starting to be wound in the opposite direction engages the actuator 82 to operate the miniature switch 81 . Upon this occurrence, the switch 81 outputs a signal to the control circuit to stop the motor 50 , thus preventing the reverse winding of the wire 40 and therefore holding the lighting fixture 1 at a lowermost position where wire 40 is fully unwound until the control circuit is instructed to lift the lighting fixture 1 . Further included in the device is a mechanism for sensing the twisting of the loader 30 relative to the casing 10 . As shown in FIG. 16, the mechanism includes a lever 93 which is inserted loosely through a hole 19 in a wall member 18 surrounding the recess 14 to be movable horizontally. The lever 93 is formed at its one end with an arcuate guide 94 engageable with an actuator 92 of a miniature switch 91 fixed to the wall member 18 . The wire 40 extends loosely through a hole 95 in the other end of the lever 93 such that when the horizontal movement of the wire cause the lever 93 to displace horizontally. In a normal condition where the loader 30 , i.e., the lighting fixture is suspended regularly as shown in FIG. 17A, the lever 93 is in a position, as shown in FIG. 17B, that the guide 94 is kept disengaged from the actuator 92 so as not to actuate the switch 91 . When the loader 30 becomes twisted as shown in FIG. 18A, the wire 40 displaces correspondingly as indicated by an arrow in the figure to cause the lever 93 to pivot about the connection to the wall member 18 , as shown in FIG. 18B, thereby engaging the guide 94 with the actuator 92 in a direction of actuating the switch 91 . In this response, the switch 91 outputs a signal to the control circuit that stop operating the motor 50 . Further, when the loader 30 becomes largely twisted, for example, to such an extent to cross the wire, as shown in FIG. 19A, the wire 40 displaces largely to pull the lever 93 in a direction as indicated by an arrow in FIG. 19B, engaging the guide 94 with the actuator 92 to actuate the switch 91 for stopping the motor 50 . In this manner, the motor 50 can stop when the lighting fixture 1 swing or twist during the operation of lifting and lowering the lighting fixture. Besides, the device has an overload sensor which comprises, as shown in FIG. 20A, a sensor sleeve 47 fixed to the wire 40 between the bearing 41 and a link 97 through which the wire 40 extends. The link is a generally L-shaped configuration and is supported to the wall member 18 with its corner engaged loosely in a hole 99 in the wall member 18 and with one arm thereof engaged with the flat spring 62 of the limit sensor 60 . The anchor sleeve 46 responsible for fixing the one end of the wire 40 to the casing 10 is clamped to the wire 40 at a clamping strength which is sufficient to bear a limited load of suspending the lighting fixture 1 but fails to bear an overload applied to the loader 30 . That is, when the overload is applied to the loader 30 , the wire 40 slips out of the anchor sleeve 46 to be thereby lowered until an end sleeve 48 at the distal end of the wire 40 abuts against the bearing 41 , as shown in FIG. 20B. Upon this occurrence, the sensor sleeve 47 pushes the arm of the link 97 which in turn to resiliently deform the flat spring 62 to thereby actuate the associated switch 61 , thus stopping the motor 50 . In order to protect the end of wire 40 from entirely slipping out of the bearing 41 , the end sleeve 48 is tightly or permanently secured to the wire 40 . At this moment, the loader 30 is lowered to disengage the pins 33 from the connector 15 so as to stop feeding electricity to the lighting fixture, thereby alerting the overload condition. Although the overload sensor utilizes the flat spring 62 and the switch 61 common to the limit sensor 60 , separate flat spring and switch may be provided for the overload sensor. Instead of providing the anchor sleeve 46 , a coil spring 49 may be provided between the end sleeve 48 and the bearing 41 , as shown in FIG. 21. The coil spring 49 is chosen to have a stiffness great enough to bear the normal load of suspending the lighting fixture and is compressed only when the overload is applied to the wire 40 . Thus, upon the wire seeing the overload condition, the coil spring is compressed to lower the sensor sleeve 47 together with the end sleeve 48 , thereby actuating the link 97 to actuate the switch 61 for stopping the motor. In order to reduce the thickness of the casing 10 , the interior space around the convex formed by the recess 14 is effectively utilized to accommodate the motor 50 in a space on one side of the convex and accommodate the end pulley 53 and the circuit board 56 on the opposite side of the convex.

Claims: A device for mounting a lighting fixture to a ceiling, said device having a capability of lifting and lowering the lighting fixture and comprising: a casing (10) for mounting at the ceiling and incorporating an electric motor (50) with a rotating drum (51); a loader (30) carrying said lighting fixture (1); and a wire (40) extending from said drum (51) and descending from the casing (10) to pass round a pulley (31, 32) in said loader (30), and ascending back to said casing (10) to terminate at a second end fixed to said casing (10), such that winding and unwinding of the wire (40) on and from said drum (51) lifts and lowers said loader (30) together with the lighting fixture (1), characterized in that said second end of said wire (40) is anchored to said casing (10) by means of a bearing (41), said bearing comprising a first member (42) mounted to said casing (10) and a second member (43) rotatable relative to said first member and holding said second end of said wire (40); and that the device includes further a fit sensor (61, 62) which outputs a fit signal upon sensing that said loader (30) fits into a recess (14) of said casing (10); a torsion sensor (91, 93) which outputs a torsion signal upon sensing that said loader (30) is twisted relative to said casing (10); a loose sensor (54, 71) which outputs a loose signal upon sensing that said wire (40) is slackened around a pulley (53); in said casing (10) a reverse-winding sensor (81, 82) which outputs a reverse-winding signal upon sensing that said wire (40) is wound reversibly around said drum (51); a load sensor (47, 97, 62, 61) which outputs an over-load signal upon sensing that said loader (30) receives an overload; and a controller which stops said motor (50) in response to any of said signals. The device of claim 1, wherein said wire (40) passes from said drum (51) round first and second pulleys (53, 55) provided within said casing (10) and descends from the second pulley (55) towards said loader (30). The device of claim 1 or 2, wherein said casing (10) is provided in its bottom with a recess (14) to receive said loader (30), the recess being provided with an electrical connector (15) for supplying electricity to said lighting fixture (1). The device of claim 1, wherein said casing (10) accommodates said motor (50) and electrical components for said controller, respectively on opposite sides of a convex portion formed in the interior of said casing (10) by said recess (14). The device of any preceding claim, wherein said casing (10) is suspended from the ceiling by means of a support member (20), said casing (10) being articulated to said support member (20) so as to extend horizontally when suspending from an inclined ceiling.

Inventors: SHIMIZU TOSHIYUKI, SHIMIZU, TOSHIYUKI, Shimizu, Toshiyuki, c/o Matsushita Elec. Works,Ltd
Applicants: MATSUSHITA ELECTRIC WORKS LTD, MATSUSHITA ELECTRIC WORKS, LTD.
Application year: 1995
Main classification: F21V21
IPC codes: F21V21