Abstract:
A hoist system having a drum primarily self-contained within a batten, for raising and lowering lighting, sound equipment, curtains and the like in a performance environment. The hoist system may be adapted with safety mechanisms including an overload sensor and/or a slack line detector. The system may be provided in the form of a point hoist. The compact system is highly scalable to a variety of spaces and applications, including school and public theaters and concert halls, as well as some homes, private business, etc.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/725,831, filed Dec. 21, 2012, now U.S. Patent No. , which application is hereby incorporated herein by reference in its entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    Not Applicable. 
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
       [0004]    Not Applicable. 
       REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX 
       [0005]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0006]    Field of the Invention 
         [0007]    The invention relates generally to an apparatus, system and method for moving a load. More specifically, the invention relates to a compact hoist system with potential applicability in a theater, concert hall or stage environment, for raising and lowering curtains, scenery, lights and the like, as well as in a variety of other home and business contexts. 
         [0008]    Description of the Related Art 
         [0009]    Conventional lift or hoist systems of a variety of types are known for use in theatrical or other performance environments. A typical system may include a large rectangular casing having therein a winch or other motor, a drive mechanism, a drum around which winds lifting or support cable, along with various controllers, sensors and safety mechanisms. 
         [0010]    The mechanics of a conventional hoist system may be fixed to a framing beam or other secure, elevated structure of the performance location. Elongate cables or other members emerge from the mechanics, potentially re-routed by pulleys and other features prior to descending, and are typically connected to a batten or other structure to which are connected items to be raised or lowered, such as lights, speakers, curtains, etc. 
         [0011]    An alternative implementation has the elongate members fixed to the overhead structure, with the other end of the elongate members descending downward toward and supporting the mechanics of the hoist, which move upward and downward along with the items to be raised and lowered, which commonly are connected to a batten attached to a body of the hoist. 
         [0012]    Conventional hoist systems tend to be bulky, with asymmetrical enclosures and external battens, which may lead to a costly loss of space in cramped environments, complicated retrofit projects or, in cases of new construction, expensive custom designs. 
       SUMMARY OF THE INVENTION 
       [0013]    The invention relates to a hoist system, method and apparatus. In one embodiment, the invention includes a hoist or lift contained within a compact structure. In a more specific embodiment, the invention seeks to offer a compact and highly adaptable self-climbing hoist system, at least some of the components of which are confined within an enclosure of the same. In a still more specific embodiment, the enclosure may be a tube or batten to which are attached items to be raised and/or lowered. The design of the invention is such that it may be scalable to a wide variety of sizes and applications. 
         [0014]    In one aspect, a hoist in accordance with an embodiment of the invention includes a pipe batten or other object, for raising and lowering items under control of a motor-driven drum having wound around it an elongate member fixed to an elevated support, thereby raising and lowering the hoist upon rotation of the drum, wherein the drum is disposed within the pipe batten or other object. Depending upon a particular application, this arrangement may permit use of a hoist that is lighter, occupies less space and/or requires a motor having less torque, among other features, as compared to other hoist designs. 
         [0015]    In another aspect, a batten in accordance with the invention may further act as a structure for supporting desired features, including light and sound fixtures, sources of electrical power, etc. 
         [0016]    In another aspect, a point hoist is provided in accordance with an embodiment of the invention, moveable throughout a variety of locations such as for use for less permanent lifting needs. 
         [0017]    In another aspect of the invention, a safety mechanism is provided by way of a slack-line detector, having a mechanism for detecting a reduced tension in a supportive elongate member, as may result from an object to be raised/lowered encountering an obstruction during lowering. In response to detecting slack on the line, the associated system may be partially or completely shut down, among other possibilities. 
         [0018]    In another aspect of the invention, a safety mechanism is provided by way of an overload sensor, having a mechanism for detecting a load that exceeds a desired or recommended capacity of the associated hoist system. In response to a determination that an excessive load is present, the associated system may be partially or completely shut down, among other possibilities. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a partial perspective view of an embodiment of a hoist system in accordance with the invention, the view being truncated for illustration purposes. 
           [0020]      FIG. 2  is a perspective view of an embodiment of the internal mechanics of a hoist system in accordance with the invention. 
           [0021]      FIG. 3  is a perspective view of a dual-motor embodiment of a hoist system in accordance with the invention. 
           [0022]      FIG. 4  is a perspective view of an embodiment of the internal mechanics of a hoist system in accordance with the invention. 
           [0023]      FIG. 5  is a detailed perspective view of an embodiment of a mechanism for connecting a batten to an overhead support in accordance with the invention. 
           [0024]      FIGS. 6A and 6B  are detailed perspective views of an embodiment of a mechanism for connecting a wire rope to a double sheave assembly in accordance with the invention. 
           [0025]      FIG. 7  is a detailed perspective view of the internal components of an embodiment of a hoist system in accordance with the invention. 
           [0026]      FIGS. 8A and 8B  are a perspective view and sectional view respectively of an overload sensor in accordance with an embodiment of the invention. 
           [0027]      FIGS. 9A and 9B  are perspective views of alternative embodiments of a slack line detector in accordance with the invention. 
           [0028]      FIG. 10  illustrates a perspective view of a point hoist in accordance with an embodiment of the invention. 
           [0029]      FIG. 11  illustrates a perspective view of an embodiment of a diverter pulley system in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    In the following detailed description of the invention, reference is made to the figures, which illustrate specific, exemplary embodiments of the invention. It should be understood that varied or additional embodiments having different structures or methods of operation might be used without departing from the scope and spirit of the disclosure. 
         [0031]    In one implementation, the invention comprises a self-contained, self-climbing hoist system, having a motor, and a drum around which winds one or more lengths of cable, rope or other elongate member, for lifting and lowering at least a portion of the system, thereby also lifting attached objects, with respect to a fixed support. Depending upon an intended application, the motor and drum may be partially or fully contained within a batten or other enclosure. A batten often takes the form of a pipe or tube batten, though other forms are contemplated. For example, the use of a length of material having a square or other polygonal, elliptical, or any other cross-section might be beneficial, depending upon a particular application. Articles to be raised and lowered may be attached to the pipe directly, or indirectly, such as through a laddered arrangement of one or more additional pipes or other support mechanism, depending upon a particular application. 
         [0032]    An embodiment of the invention is illustrated by  FIG. 1  as a hoist  100 . In this embodiment, the hoist  100  is self-contained within a tube or pipe, here a batten  102 . The size and/or shape of the batten  102 , its method of manufacture, etc., may vary significantly depending upon a particular application. In one embodiment, the batten  102  is formed as an extrusion in a desired shape (i.e., cross section, generally, through the use of a die). The shape may be chosen for ease of attachment of a wide variety of attachments (temporary or permanent), including light fixtures, sound elements, power outlets, etc. 
         [0033]    The batten  102  as illustrated houses a motor and drum. Powered by the motor, the drum rotates about an axis that may be substantially shared by the batten  102 , spooling or winding an elongate member  104  around the drum. As explained in greater detail herein, the drum may, during rotation, further move in a direction parallel to its center axis and at a predetermined distance/rate with respect to the rotation, such that as the elongate member  104  encircles the drum, successive lengths thereof lay in direct contact with the drum, rather than the elongate member piling  104  atop itself. 
         [0034]    The drum may further be adapted with grooves or ridges for receiving the successive lengths of the elongate member  104 , such that an outer diameter of the combination of the drum and wound elongate member is 1) greater than an outer diameter of the drum itself by an amount less than a diameter of the elongate member, or 2) not increased at all by the elongate member  104 , in a case that the elongate member  104  fits entirely within the grooves. In an application where elongate members  104  fit fully within grooves of the drum, a batten  102  may be chosen such that, as elongate members  104  encircle the drum, the batten  102  prevents the elongate members  104  from leaving the grooves, although tension on the elongate members  104  may not be fully maintained. In either case, this feature may enable a more compact design, e.g., the use of a tube of a relatively smaller diameter, depending upon a particular application. 
         [0035]    An elongate member may be connected to a drum and adapted to wind thereabout in a variety of ways. In one embodiment, a drum is adapted to receive two elongate members  104  (or two lengths of a continuous elongate member  104  as further discussed herein) at an end. Thus, the grooves may be formed as a double-lead helical groove, i.e., double-start drums may be used. Three (triple)- or further multiple-lead arrangements are contemplated as well, depending upon a particular application. A multi-lead arrangement may increase strength and reliability over a single lead, provide redundancy as a safety measure, decrease noise and/or component wear, etc. For example, instead of an arrangement having two 3/32″ leads, a single ⅛″ lead, three 1/16″ leads, etc., might be substituted, depending on needs. Although the wire ropes may be in close proximity, they do not cross over each other as they wind onto the drum. This may extend the life of a wire rope on average, avoiding the additional physical stresses that may occur through the piling of the rope, crossing over, etc. 
         [0036]    As further described herein, a batten and drum may cooperate in a variety of ways. In one embodiment, a drum is entirely encompassed by a batten having the same shape as the drum, with the batten having an internal diameter (and circumference) only slightly larger that an external diameter (and circumference) of the drum. In certain applications, the difference may be on the order of a few thousandths of an inch, for example. The design parameters of the drum and batten may alternatively be such that the two surfaces are intended to remain in slight contact during operation, where the surface of the drum may be interrupted by grooves for receiving a wire rope. A depth of grooves in the drum may likewise be on the order of a few thousandths of an inch deeper than a diameter of the wire ropes. 
         [0037]    In such an embodiment and others, materials for the batten and drum may be chosen accordingly. For example, a drum may be formed from a glass-filled nylon or other low-friction material with respect to a steel batten, among a number of other contemplated materials pairs. 
         [0038]    Other factors contributing to a chosen tube diameter might include the nature of the cable or other elongate member. Winding a cable upon a small-diameter drum might degrade the cable over time, due to physical stresses within the strands or other material of which it is formed, imparted when the cable is over-flexed upon being wound. The use of a larger diameter drum might lessen these stresses, depending upon the relative diameters involved, the nature of the elongate member, etc. 
         [0039]    In many applications, it is desirable to attach a hoist to a fixed, elevated structure. As shown in the exemplary embodiment of  FIG. 1 , the elongate member  104  emerges from the batten  102  through an opening, and may be used to couple the hoist assembly  100  directly or indirectly to an overhead structure or other support. Specifically, the elongate member  104  in  FIG. 1  passes through a double sheave assembly  106 , and is connected to a beam clamp  108  by any of a variety of means, as further described herein. The beam clamp  108  may be attached as desired to an elevated structure, such as an overhead beam in a concert hall or theater setting, among numerous other potential applications. Other means of installing a hoist assembly for use are contemplated, as would be understood by one skilled in the art. 
         [0040]    The elongate member  104  may be fabric rope, wire rope or cable, among others. In one embodiment, four approximately 0.28 ( 3/32″) inch wire ropes are used, though countless variations are contemplated, depending upon a variety of factors. In another embodiment, approximately 0.28 ( 3/32″) inch wire ropes are attached at a separation of 1.125 (1⅛) inch and wound at a ¼ inch pitch (i.e., 4 grooves per rope per inch, i.e., 8 grooves per inch for a dual-rope, double-start drum). Single-rope hoists are contemplated as well, as for lighter-duty applications. Larger diameter or more numerous ropes, with the same or larger diameter drums, may be used for heavier duty applications. 
         [0041]    As illustrated by  FIG. 1 , an elongate member  104  may be comprised of multiple (as shown, 2) strands of rope. In one embodiment, a single strand of elongate member  104  is connected at both ends to a beam clamp  108  or other means of attachment, while a body of the member  104  passes unbroken through the double sheave assembly  106  or other suitable means of attachment to the batten  102 . This continuous U-shaped length of elongate member  104  may further be fitted with, for example, a compression sleeve (see  FIG. 6 ), such that if one of the two (in this embodiment) substantially parallel lengths of member  104  breaks, the other does not pull through the assembly  106 , and maintains its support of the hoist assembly  100 . A compression sleeve may likewise be used to couple the ends of two separate elongate members  104  in an embodiment where two strands are used, or in a single-strand embodiment in which the continuous end is disposed within or near the beam clamp  108 . 
         [0042]      FIG. 2  illustrates components of an embodiment of a hoist system  200  that may be internal to an enclosure or tube, for example a batten  102  as in  FIG. 1  or a pipe batten  202  (illustrated transparently except for an outer periphery) as in  FIG. 2 , in accordance with the invention. Depending upon a particular application, an internal mechanism of the hoist system  200  might include a wide range of components, for example a motor  210 , a gearbox  214 , a gear mount to pipe batten coupling  215 , a motor shaft to spline shaft coupling  217 , a shaft coupling  216 , a drum  220 , a drum shaft or axle  225 , a nut collar  230  fixed within the drum  220 , an acme screw  240 , a spline outer race housing  255 , and a spline shaft  250  (see also  FIG. 3  and description). In one embodiment, a motor  210  is coupled to and drives a drum  220  via a spline shaft  250 , through which the motor  210  is able to impart a rotational force while allowing the drum  220  to slide, within a predetermined space, along the spline shaft  250 . The spline shaft might further be connected to the acme screw  240  via the drum axle  225 . 
         [0043]    In operation, these components may share a center axis, or various components may be offset as desired, with certain components potentially disposed outside of the tube, depending upon constraints including space, lift capacity required, etc. For example, it might be desirable due to space constraints that the motor be disposed in an offset position, parallel to and coupled to the drum  220  using gears or other suitable means, such that a length of the tube and/or overall apparatus might be lessened. 
         [0044]    In one embodiment in accordance with the invention, as illustrated by  FIG. 3 , a hoist system  300  includes two motors  310   a  and  310   b  for driving two drums  320   a  and  320   b  disposed between the two motors  310   a  and  310   b,  one disposed at each approximate end of the associated enclosure, which may be a box, case, etc., here assumed for purposes of illustration to be a batten or other tube-like structure. Alternatively, the motors  310   a  and  310   b  or a single dual-drive motor might be disposed in an approximate center along a length of batten, or offset and having a nut collar or analogous feature at an approximate center, for driving the drums  320   a  and  320   b  positioned outwardly from the center, depending upon a particular application. 
         [0045]    An operation of an implementation of a hoist system in accordance with the invention is described herein in the context of a dual-motor embodiment, with the associated concepts applicable as well to a single-motor embodiment, in accordance with the skill in the art. In another embodiment, a single motor, which might need to be of increased power in certain applications, is disposed at one end of a pipe or other enclosure, to drive one (1) or more drums about an acme screw fixed at the second end. For example, in a large venue application, e.g., an airplane hangar or terminal, a hoist of 300 or more feet might be needed, in which case it may be desirable to chain 15, 30 or more drums together. The invention is in that sense and others scalable and adaptable to a wide variety of potential implementations. 
         [0046]    As described herein, the hoist system  300  might be designed such that, upon operation of the motors  310   a  and  310   b,  an approximately horizontal (assuming a normal operating position) translation of the drums  320   a  and  320   b  occurs. 
         [0047]    In one embodiment, casings of the motors  310   a  and  310   b  and a nut collar  330  are fixed with respect to the tube, while rotors of the motors  310   a  and  310   b,  the drums  320   a  and  320   b,  an acme screw  340  and a spline shaft  350  are fixed with respect to each other, and turn within the tube. In addition to rotating within the tube, the drums  320   a  and  320   b  might be adapted for lateral (generally horizontal, assuming a normal operating position) movement along the spline shaft  350  by virtue of a pair (in a dual motor environment) of sliding couplers, herein spline couplers  355   a  and  355   b,  rotationally coupling each of the drums  320   a  and  320   b  to the spline shaft  350 , i.e. transferring the driving force thereto, while allowing the drums  320   a  and  320   b  to respectively slide along the spline shaft  350  upon rotation, as described herein. 
         [0048]    For example, an assembly of the two drums  320   a  and  320   b  and an acme screw  340  connecting them might be disposed in relation to the nut collar  330  such that upon rotation the two drums  320   a  and  320   b  move in unison along spline shaft  350 , either toward one motor  310   a  or the other motor  310   b,  depending upon a direction of rotation. For example, the fixed-position nut collar  330  might be threaded to mate with threads of the acme screw  340 , thereby imparting a generally horizontal force upon rotation of the acme screw  340  with respect to the respectively fixed nut collar  330 . The resulting horizontal translation allows elongate members entering a fixed cutout in the tube to wrap around the drums  320   a  and  320   b  as the drums  320   a  and  320   b  rotate. Alternative arrangements leading to a similar result are possible as well. 
         [0049]    In an alternative embodiment, the drums  320   a  and  320   b  move inward toward each other or outward away from each other, depending upon a direction of rotation of the motors  310   a  and  310   b.  Multiple nut collars  330  might be used or, as another example, one shaft might be threaded internally within another, etc., thus pulling the shafts inward. A relative direction of rotation of drums  320   a  and  320   b  is variable as well. For example, whether under control of a single or multiple motors  310   a  and  310   b,  the drums  320   a  and  320   b  might rotate in the same or opposite directions, either consistent with the directions of rotation of the motors  310   a  and  310   b  or, as in a single-motor embodiment, through the use of differentials to switch a direction of rotation inline. In one embodiment, depending upon an angle of exit of an elongate member from a batten, multiple such exits at the same angle along an outer periphery (e.g., circumference) of a batten (as might be the case when using drums that rotate in unison) might naturally lead to a torque being imparted on the batten. Utilizing drums rotating in opposite directions, with corresponding rope exits being on opposite sides (for example, at 10 o&#39;clock and 2 o&#39;clock, or 9 o&#39;clock and 3 o&#39;clock positions, about a cross-sectional periphery of a batten) of the batten, might beneficially lessen or eliminate (by counteraction) a collective torque on the batten. 
         [0050]    As noted herein, an embodiment of a hoist  400  is contemplated in which a driving source, such as a motor  410 , is disposed outside of a pipe  402 , as illustrated by  FIG. 4 . The motor  410  in this embodiment is coupled to a threaded drive shaft such as a spline shaft  450  through an optional gear box  414  and pipe batten-to-gearbox coupling  415 . A gear box  414  might allow use of a motor  410  having less horsepower or lower torque, which may be a tradeoff for higher revolutions-per-minute (RPM) to achieve a comparable lifting action (speed, maximum load, etc.). Pipe batten-to-gearbox coupling  415  connects and prevents respective motion between the pipe  402  and the gearbox  414 . 
         [0051]    A pipe batten  502 , the position of which may be seen in  FIG. 5 , has been rendered transparent in  FIG. 4  to better illustrate internal features such as a drum  420 , a spline shaft  450  and a spline outer race to drum shaft coupling  455 . In this embodiment, the spline outer race to drum shaft coupling  455  couple the spline shaft  450  to the drum  420 , such that as the spline shaft  450  rotates under the power of the motor  410 , the drum  420  translates parallel to a center axis (e.g., of rotation) of the spline shaft  450  (and in this embodiment, an axis of the motor  410 ). It is also contemplated that an axis of the motor  410  be offset from an axis of the spline shaft  450  if desired, such as to accommodate for space limitations. 
         [0052]    It may further be seen in connection with  FIGS. 4 and 5 , as further described herein, that a batten  502  may be chosen to be only slightly larger than an outer surface (i.e., the lands of any grooves) of the drum  420 . This may have the effect of, as wire ropes enter the batten  502  to be wound upon the drum  420 , physically maintaining the wire ropes within the grooves around nearly an entire circumference of the drum  420  (in one embodiment, on the order of 340 degrees of the circumference). 
         [0053]      FIG. 5  generally represents the view of  FIG. 4  as a hoist system  500  having a motor  510  and a gearbox  512 , without the transparency of the batten  502 . In addition to the features described in the context of particular embodiments of the invention, it is contemplated that the features be variously used in other applications, and additional features are contemplated as well, including an overload sensor  518  and slack line detector  558 , described in greater detail with respect to  FIGS. 8 and 9 , respectively. 
         [0054]      FIGS. 6A and 6B  illustrate an embodiment of a mechanism for connecting a wire rope  604  and a sheave assembly  606 . As discussed herein, a single length of wire rope  604  may be looped through the sheave assembly  606 . In such an embodiment, it may be desirable to include an inline compression fitting  607 , such that if the wire rope  604  fails in one of the two parallel portions, the hoist  600  will remain supported by the remaining length of wire rope  604 , by virtue of the compression fitting preventing the wire rope  604  from freely pulling out of the assembly  606 . 
         [0055]    An enlarged view of the cooperation between a drum shaft  725 , an acme nut  730  and an acme screw  740  in accordance with an embodiment of the invention is provided by  FIG. 7 . The acme screw  740  in this embodiment is coupled to an interior wall of the pipe batten  702  by an acme screw anchor  742 . As disclosed herein, as the acme screw  740  turns with respect to the screw anchor  742  (and pipe batten  702 ), the acme screw  740  and the drum (not shown) is drawn or pushed in a direction substantially parallel to the length of the pipe batten  702 , depending upon a direction of rotation of the acme screw  740 . Alternatively, the acme rod  740  may be held fixed, while an acme nut, e.g., screw anchor  740  is attached to the drum. As the acme nut  740  turns, it travels along the acme rod  740 , moving the drum laterally. 
         [0056]      FIGS. 8A and 8B  illustrate an embodiment of an overload sensor  818   a  and  818   b  that might be provided for use with a hoist  800  in accordance with the invention, such that if too great a load is placed upon the hoist  800 , a portion or all of the overall system is disabled. In one embodiment, between a beam clamp  808  (or other suitable support mechanism) and a sheave assembly  806  (or other suitable attachment mechanism) are disposed a fixed bracket  824  coupled to the beam clamp  808  and moveably coupled to a sliding bracket  822 . Between the fixed bracket  824  and the sliding bracket  822  may be disposed one or more compression springs  826  or other resistive means to assert a certain amount of resistive force against the movement of the sliding bracket  822  in the direction of the fixed bracket  824 , each bracket having one or more ground-out contacts  828  that come into contact with each other upon a sufficient displacement of the sliding bracket  822  toward the fixed bracket  824 . A strength of the springs  826  or other resistive means may be chosen such that contact between the contacts  828  only occurs under a pre-determined sufficiently great load has been placed on the elongate members  804 . Contact between the contacts  828  may be designed to create a condition, such as an electrical ground-out, switch actuation, etc., sufficient to disable at least a portion of the system  800   a  to avoid operation during an overload situation. 
         [0057]    In one embodiment, an internal shaft (e.g., drum shaft  725  in  FIG. 7 ) is energized, for example with  24  volts or other appropriate potential, which will be electrically isolated, and which will energize at least one of the wire ropes (also electrically isolated, as by the drum), while the pipe  802  is connected to electrical ground through the motor. When the springs  826  of the overload sensor  818  are compressed (due to too much weight on the batten), the contacts  828 , illustrated in the form of bolt heads, will contact each other, creating a ground-out situation through connection to the building steel or other support structure for example, stopping the pipe  802 . Limiting the electrical current (in one embodiment, only 200 milliamps) running through the wire rope  804  can eliminate or reduce the risk of a harmful electrical shock if a person were to come into contact with the wire rope  804 . 
         [0058]    Another feature that might be offered in conjunction with the hoist electrical arrangement disclosed herein is a limit selector for controlling an operating range of motion (e.g. lifting range) of a hoist. In one embodiment, in which a drum translates as it rotates, a controller may be provided in connection with a moveable switch (not shown) placed in a path of the drum. The switch may be positioned such that when the drum translates to a certain location (corresponding to a certain lift position), the drum actuates the switch, in connection with the ground-out system, for example, to prevent further translation (and thus rotation) of the drum in the same direction (though it may still be reversed to lower a load to the extent of a second limit position). Through selection of positions of limit switches, the operable range of a hoist system might be variably chosen.  FIG. 8  further illustrates a slack line detector  858 , as described in greater detail herein with respect to  FIGS. 9A and 9B . 
         [0059]      FIGS. 9A and 9B  illustrate embodiments of a hoist  900  adapted with slack line detectors  958   a  and  958   b  for detecting a condition in which an expected tension on an elongate member  904  releases, as may occur when a load to be hoisted encounters an obstacle while being lowered. A slack line detector  958   a  may serve as an alternative to a ground out bar, which may run the length of, and parallel to, a drum, such that when a wire rope goes slack, it pulls or falls away from the grooves of the drum, contacting the ground out bar and stopping the system. The slack line detector  958   a  may be adapted to work in a variety of ways. In one embodiment, a tensioned (e.g., spring loaded) rocker arm  962  having a pulley  960  is positioned such that upon action of the spring or tensioning device (not shown) the arm  962  is contact with a bar  964  (see  FIG. 9A ). When the pulley  960  is disposed against a taut wire rope  904 , the rocker arm  962  is pulled away from the bar  964  (see  FIG. 8A ). When the wire rope goes slack, the spring loaded arm  962  moves to contact the bar  964 , creating a ground-out condition through connection to the detector  958   a,  which is connected to the grounded pipe, for example. 
         [0060]    As described with respect to an overload sensor, one of the wire ropes  904  may be electrically charged while another wire rope  904  is electrically isolated, in which case contact between the wire ropes  904  will cause a ground out situation, stopping the system. The small pulley  960  may be formed from a metal or other conductive material, with the arm  962  being electrically isolated, such that it will ground upon contact with the small bar  964  to stop the system. In another embodiment, the arm  962  of a slack line detector  958   b  instead contacts and activates a micro-switch  963 , electrically sending a signal to the motor to stop, as illustrated by  FIG. 9B . 
         [0061]    In another embodiment, a hoist is provided in the form of a type of movable point hoist, an embodiment of which is illustrated by  FIG. 10 . In a point hoist  1000 , a motor  1010  may be attached to a drum  1020 , which is drawn inward into a pipe or cover  1002  as the drum  1020  rotates, drawing up wire ropes  1004  and lifting or lowering an object or structure as desired, as described herein. In this embodiment, an acme rod  1040  would be held stationary (with respect to any translation along its length), while the drum  1020  would translate as it turns, drawing the assembly into the pipe or cover  1002 . A point hoist may be mounted to a simple aluminum channel, for example, as opposed to being inside a pipe. This channel could be mounted to a grid or other means above the stage, etc. and could be moved to different positions. The motor  1010  and drum  1020  may be mounted on bearings or other low friction or otherwise slide-friendly surface within the channel. In one embodiment, a point hoist will weigh approximately  50  pounds for ease of movement. As noted, in certain applications a point hoist  1000  has a drum  1020  that is not necessarily confined within a pipe  1002 , which may permit use of a larger diameter wire rope (⅛ inch, 3/16 inch, etc.), which may enable lifting a heavier load. 
         [0062]    Herein, various hoist systems have been illustrated by way of example as primarily having elongate members exiting a batten or related structure and extending substantially vertically, such as to fixed overhead locations. It should be noted, however, that a hoist system in accordance with the invention is further versatile in this aspect.  FIG. 11  illustrates a hoist system  1100  with a batten  1102  having connected thereto a double sheave assembly  1106  that has been adapted for use with a diverter pulley system  1144 . The pulley system  1144  is formed from a bracket  1146  coupled to the batten  1102  along its length by a mount  1147 . The pulley system  1144  is mounted a distance from a sheave assembly  1106  to divert elongate members  1104  approximately laterally along the batten  1102  through the use of pulleys  1148 , in order adapt to varying overhead attachment locations and scenarios. 
         [0063]    In the exemplary embodiment illustrated, the bracket  1146  is formed from a unitary piece of material, adapted for a predetermined overhead location, however it may alternatively be formed from multiple individual pieces, in one embodiment having a set of pulleys  1148  positioned near the sheave assembly  1106 , and another set of pulleys  1148  attached to a second bracket, moveable along a length of the batten  1102 . Alternatively, such a bracket  1146  assembly may slide to lengthen, to adapt for varying points of overhead attachment. As illustrated by  FIG. 11 , a hoist system  1100  of the type shown may also accommodate scenarios in which overhead support structures are at an angle (i.e., not level) and/or in which the batten  1102  itself is desired to be used at an angle, independent of an orientation of overhead support structures. 
         [0064]    Within the broader concept of a compact hoist system in accordance with the invention, many specific implementations are contemplated, along with various alternatives. With respect to exterior dimensions, in one embodiment, an enclosure (e.g., batten, etc.) having a diameter of 2.125 (2 and ⅛) inches and 20 feet in length is utilized with two-foot drums. Some scalability might be achieved by varying the length and/or size of various components, while more extreme scalability might be achieved by coupling multiple such apparatus end to end, or using only half (e.g., a single motor-drum combination), which itself might be scaled as necessary, depending upon a particular application or environment. 
         [0065]    Various motors might be used in accordance with the invention, depending upon a particular application, among them a variety of currently available tubular motors, or any of a variety of servo motors, such as stepper motors or other suitable drive unit, among others, in environments where it may be desirable to receive feedback regarding a motor&#39;s position. 
         [0066]    An elongate member, e.g., rope, cable, etc., might be attached to a drum in a variety of ways. Multiple cables might be associated with a single drum or multiple drums. In one embodiment, a connector or sleeve facilitates installation of the member at one end to a drum. The end is pushed into the connector, which might sit in a cutout in the drum, and forced through spiral grooves or other features adapted to clamp or grasp the end, with a second end emerging through an opening in the batten. Outside of the batten, the elongate member might pass through a sheave assembly or other suitable means for supporting the batten. In one embodiment, the elongate member is attached at its other end with a thimble to a triangular or other shape block, as desired, which is attached to a beam clamp. In one embodiment, the beam clamp is formed from two partially overlapping J-shaped members, as illustrated herein. 
         [0067]    While the description herein may refer to specific reference numbers in the figures, the description is likewise applicable to analogous elements having different numbers. For example, descriptions of features of a drum  220  may likewise apply to others such as drums  320   a  and  320   b,  etc., and components such as a drum  220  may be used with any other features, although they might only be disclosed herein with respect to another embodiment. 
         [0068]    As noted above, battens are only one embodiment of an enclosure in accordance with the invention. The concepts of the invention may have applicability to other structures/enclosures, etc. as well, and numerous additional applications are further contemplated. For example, the inventions have been described primarily with respect to an enclosure that takes the form of a tubular structure, e.g., a circular, elliptical or otherwise rounded structure. As will be clear to one skilled in the art from the disclosure, however, other shapes, including square, rectangular and other polygonal and other shapes as well, depending upon a desired application. Nor is the invention limited to any particular material or structural framework. The concepts, methods and apparatus disclosed may be used in countless other applications not expressly mentioned herein without departing from the scope and spirit of the invention. 
         [0069]    The inventions have been described for connection to an overhead support for lifting objects vertically, primarily in performance-type environments. Other implementations are contemplated, however, such as for pulling up an incline, and dragging/towing an object across a horizontal surface, among others, as well as in a variety of other venues and outdoors. An embodiment is also contemplated in which a vertical orientation of a hoist in accordance with the invention is substantially reversed, such that batten is mounted in an elevated position with elongate members extending outwardly therefrom, for attachment to an object to be lifted or moved. 
         [0070]    As described herein, positional references and terms of orientation, such as overhead, elevated, above, below, horizontal, vertical, etc., herein assume a certain orientation of the described apparatus, are not intended to dictate precise angles or positions, and may be reversed or otherwise varied, depending upon the relative locations and orientations of the items involved. 
         [0071]    A means for causing translation of a drum due to rotational motion is described herein by way of example as a rod having acme threading, but variations are contemplated. A variety of threading techniques are known, and the threads need not be trapezoidal in cross section and/or formed at any particular angle or pitch. Nor must a threaded rod be used at all where other drive means are available. 
         [0072]    The inventions have been described in the context of a system whose primary mechanics (motors, drums, drive features, etc.) may be enclosed within a batten or other support enclosure. The system, however, might further include external features as described, including elongate members, mechanism for attachment to an elevated support, pulleys, sheave assembly, etc. In addition, various primary features might be disposed externally, depending upon a nature of the enclosure used and the application environment. Many features as well have been described as sharing a center axis, but a departure from this is likewise contemplated, as described herein. Furthermore, while the invention has often been described generally in the context of a smaller, more compact system, the concepts herein are applicable and scalable to much larger-scale operations as well. 
         [0073]    In describing the inventions, various articles may be described as coupling or being coupled, connecting or being connected, attached, etc., to one another. This phraseology is not intended to exclude potential intermediate parts, i.e., coupling and connecting may be direct or indirect, unless otherwise limited.