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BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to safety accessories for use in building construction, specifically additions to structures such as swingstage scaffolds, buckhoists, and mastclimbers to prevent objects from falling to the ground below such structures. 
         [0003]    2. Description of the Related Art 
         [0004]    Various industries require workers to be in position on the exterior of a building, whether the building is complete or under construction. For completed buildings, various maintenance and cleaning operations necessitate that workers have access to the exterior surfaces. During construction, many operations related to both erection of the structure and treatment of exterior surfaces create similar requirements. 
         [0005]    Necessarily, access must be provided to building exteriors from ground level up to the full height of such structures. This requires support structures to be movable vertically. This has been achieved by use of devices such as swing stage scaffolds, which are typically supported by cables attached to the roof of a building. Buckhoists and mastclimbers are known alternatives used as the need dictates. 
         [0006]    Where the area surrounding buildings is open public space, pedestrians and automobiles are moving in and out of the area on the ground that lies directly beneath the support structures on which the workers are standing. Consequently, people are potentially in the direct path of construction materials, tools, and any other object on the support that might fall over the side. 
         [0007]    During some construction projects, rigid temporary canopies are created to shield pedestrians from such projectiles. However, it is not always practical or even possible to put a hardened structure in place any time one or more workers is in place on the side of a structure. There remains the concern, therefore, that an object will be accidentally dropped over the side of a support structure on which an individual is working and will fall to the ground below with disastrous consequences. Even a relatively small article with comparatively low mass, if dropped from a sufficiently great height, will achieve enough momentum to cause serious injury or death if it falls upon a person below. 
         [0008]    In addition to the concern of materials being accidentally dropped over the edge of a support structure, some dropping of materials is an almost unavoidable consequence of the construction process. One such example is the application of stucco to a building exterior. The surface texture of stucco arises from the fact that it is applied to building exteriors before it has hardened. The stucco is applied manually using a trowel in such a way so as to produce the desired texture effect. Unlike structural concrete, the stucco is not supported while it is sets. 
         [0009]    Accordingly, at the time of application, the stucco must be sufficiently liquid so that it can be worked and shaped, yet no so thin so that it runs or falls off prior to setting. The nature of the material and the process of applying it, however, are such that as a practical matter, some amount of stucco will fall from the building surface as it is being applied. Stucco is dense material, and even when not fully set it represents a significant safety hazard when it falls from the point of application to the ground below. 
         [0010]    Accordingly, there has arisen a need for a new support structure for workers, or an accessory for existing support structures, that can effectively prevent objects from falling to the ground below. There has also arisen the need to catch stucco and other material that falls not from the support structure on which a worker is standing, but from the building surface itself. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention addresses the problems of preventing objects from falling from a support structure and from building surfaces where workers are performing tasks. The support structure and support structure accessory of the present invention provide a catch that is positioned beneath the support structure in such a way that an object dropped from the support structure will fall into and be held by the catch. The catch can be supported along an inboard edge facing the building and along an outboard edge opposite the building. The inboard edge of the catch can be supported in such a way that it is held very close to or in contact with the building surface. The inboard edge of the catch can be held close to the building surface even as the support structure moves toward and away from the building surface. 
         [0012]    This is particularly helpful in situations such as applying stucco. If the inboard edge of the catch is maintained in contact with or in very close proximity to the building surface, stucco that has been applied to the building surface but has fallen off will fall into the catch even as the distance between the support structure and the building surfaces changes. 
         [0013]    In a first embodiment of the invention, a movable platform for supporting a load alongside a structure has an attached catch. The movable structure includes a base having an inboard side and an opposite outboard side, an inboard support extending away from the inboard side of the base, an outboard support extending away from the outboard side of the base, and a catch connected to both the inboard support and the outboard support and passing beneath the base, so that an object dropped over an inboard or outboard edge of the base will be caught by the catch. The inboard support is attached to the base so that a distal end of the inboard support is movable with respect to the base. 
         [0014]    The inboard support can include a plurality of pivotally attached inboard arms. The inboard arms can be mounted so that a distal end of a given inboard arm remains above a proximal end of that inboard arm. A wheel can be attached to the distal end of each of the inboard arms. The catch can be attached to the distal end of each of inboard arms. The outboard support can also be made up of a plurality of outboard arms, in which case the catch can be attached to the distal end of each of the outboard arms. The catch can be a flexible member. 
         [0015]    A distal end of each of the inboard arms can include a traversal mechanism. The outboard support can include a plurality of outboard arms rigidly connected to the base. The catch can be secured to the distal end of each of the inboard arms and a distal end of each of the outboard arms. The traversal mechanism can include a wheel. Alternatively, the traversal mechanism can include a skid. 
         [0016]    A securing means can be provided for securing the flexible member to the distal end of each of the inboard and outboard arms. The securing means can include a hook disposed at the distal end of each of the inboard and outboard arms, an inboard cable connected to each of the hooks on the inboard arms, an outboard cable connected to each of the hooks on the outboard arms, and a plurality of inboard and outboard latches connected to inboard and outboard edges of the catch, respectively, the inboard latches being securable to the inboard cable, the outboard latches being securable to the outboard cable. 
         [0017]    The catch can be made of netting. Alternatively, the catch can be made of a woven fabric. 
         [0018]    The inboard support can be pivotably attached to the base, in which case the inboard arms can be hingedly mounted to the base. The inboard arms are constructed and arranged so that the distal end of a given one of the inboard arms is kept at least as high as proximal end of that inboard arm. The inboard arms can be constructed and arranged so that the distal end a given one of the inboard arms is kept higher than the proximal end of that inboard arm. The inboard arms can be constructed and arranged so that the inboard arm remains elevated at least 40° from horizontal. 
         [0019]    The inboard support can include a plurality of inboard arms, each of which is axially extendable away from the base. The inboard support can include an urging element that urges a distal end of each of the inboard arms away from the base. 
         [0020]    The invention can also take the form of a safety accessory for a preexisting movable construction platform with a base having an inboard side and an opposite outboard side. The inboard arms, outboard arms, catch, and traversal mechanism can be provided as a kit which can be mounted to a conventional swing stage scaffold, buckhoist, mastclimber, or similar device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The device will be described in connection with the attached drawings, in which 
           [0022]      FIG. 1  is a perspective view of the overall device; 
           [0023]      FIG. 2  is a perspective view of a mechanism for attaching inboard arms to the base; 
           [0024]      FIG. 3  is a side view of the device illustrated in  FIG. 2 ; 
           [0025]      FIG. 4  is a perspective view of a mechanism for attaching the outboard arm to the base; 
           [0026]      FIG. 5  is a perspective view of the distal end of the inboard arm in a preferred embodiment; 
           [0027]      FIG. 6  is a side view of the device shown in relation to a building with which the device makes contact; and 
           [0028]      FIG. 7  is a side view of an alternative embodiment of an inboard arm which extends axially to accommodate differences in the distance between the base and the building. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0029]      FIG. 1  provides an perspective view of a first embodiment of a movable platform according to the present invention. The platform includes a base  101 , which provides the surface upon which people and/or materials are supported. The base as illustrated in  FIG. 1  includes walls that surround a floor section of the base. As alternatives to walls, a railing structure, vertical netting or other similar structure that provides for a barrier to prevent people and materials from falling off of the platform may be provided. Such a barrier is not a necessary part of the present device. 
         [0030]    The platform includes both inboard and outboard supports. The inboard supports are in the form of inboard arms  102 . Each inboard arm  102  is mounted at its near or proximal end  106  to base  101  in such a way that the distance between a far or distal end  107  lies a variable distance from the base  101 . This may be achieved by way of a swivel or hinge attachment between proximal end  106  and base  101 . With proximal end  106  attached in this manner to base  101 , as inboard arm  102  swings thorough its range of motion, distal end  107  can move up and down, and more significantly can move in and out or laterally, with respect to base  101 . The device may be configured to have a single inboard arm on each end of base  101 . Alternatively, a plurality of such arms  102  can be mounted along the inboard side of base  101 . 
         [0031]    One embodiment of such a connection of proximal end  106  to base  101  appears in  FIG. 2 . Inboard rail  205  is an element of base  101 . As illustrated, rail  205  has an L-shaped profile, although the present device can be used with rails or other elements having different profiles. Rail  205  may be an element of a protective railing structure of base  101 , a component of a floor section of base  101 , or other element. Inboard arm fixing element  200  provides a connection between base  101  and inboard arm  102 . Inboard arm fixing element  200  includes clamp  201 , arranged to partly surround inboard rail  205 . Fixing bolt  202  is threaded into a corresponding aperture in clamp  201 . With fixing bolt  202  removed or partially withdrawn, the clamp  201  can slide onto rail  205 . By tightening down fixing bolt  202 , clamp  201  is secured to inboard rail  205 , and therefore to base  101 . Alternative mechanisms for securing the inboard arm fixing element to base  101  are available, and include welding or mounting to an element specifically provided on base  101  for such attachment. 
         [0032]    Two flanges  203  extend away from a side of clamp  201 . Axle  204  spans the space between flanges  203  and passes through proximal end  106  of inboard arm  102 . Inboard arm  102  is therefore able to pivot through a vertical arc with respect to base  101 . 
         [0033]    One option for clamp  201  is illustrated in  FIG. 3 . In some embodiments, it may be useful to attach one or more of inboard arms  102  to base  101  in such a way as to ensure that inboard arm  102  does not fall below an elevation angle α from horizontal. This can be achieved by a stop  206 . Stop  206  can be mounted to span between flanges  203 . With stop  206  in place, inboard arm  102  can rise to be approximately vertical, and in some embodiments beyond vertical, but cannot fall below elevation angle α. Elevation angle α can be chosen so as best to match a particular application. One such angle can be 40°. Stop  206  can also be arranged so as to provide an adjustable minimum elevation angle α. Mechanisms other than stop  206  can also be used, so long as they provide a way to maintain inboard arm  102  to have at least a certain elevation angle with respect to base  101 . 
         [0034]    The embodiment of  FIG. 3  illustrates two stops  206  attached on opposite sides of fixing element  200 . Inboard arm  102  can be pivoted beyond vertical until coming into contact with stop  206  on the opposite side. In this way, if clamp  201  is constructed to be mounted to an element of a particular profile that can appear in either of two orientations on various examples of base  101 , fixing element  200  can be mounted with either two different orientations, as conditions require. 
         [0035]      FIG. 1  also illustrates an outboard support in the form of outboard arms  104 . Each of outboard arms  104  is fixed to an outboard side of base  101 . Outboard arms  104  extend upward and outward from base  101 . 
         [0036]      FIG. 4  illustrates one example of an attachment mechanism to secure outboard arm  104  to base  101 . An outboard rail  303  runs generally horizontally along the outboard side of base  101 . Outboard arm  104  is made to have two apertures passing therethrough at proximal end  108  thereof. U-bolt  301  is passed over an interior side of outboard rail  303  so that threaded ends  304  extend out beyond an exterior edge of outboard rail  303  and through the two apertures of outboard arm  104 . Nuts  302  are then threaded onto respective ends  304  so as to clamp outboard arm  104  between nuts  302  and outboard rail  303 . 
         [0037]    With outboard arms  104  attached held in a fixed relationship with base  101  and inboard arms  102  movable held to base  101 , catch  105  is suspended between distal ends  107  of inboard arms  102  and distal ends  109  of outboard arms  104 , as illustrated in  FIG. 1 . Catch  105  can assume any of a number of forms. Among other materials, it can be a woven fabric, netting, or other flexible member. The requirements are that it be sufficiently strong so that an object dropped from the base  101  and caught in catch  105  will not pass or break through the material of catch  105  itself, nor will such objects break catch  105  away from any of its attachments points. 
         [0038]    One option for attaching catch  105  to inboard arms  102  and outboard arms  104  is illustrated in  FIG. 5 .  FIG. 5  illustrates inboard arm  102 , but the same attachment mechanism can be used in connection with outboard arm  104 .  FIG. 5  presents a view of an underside of inboard arm  102 . 
         [0039]    Tab  403  extends out from distal end  107  of inboard arm  102 . A cable  405  passes through an aperture  404  in tab  403 . Cable  405  interconnects all of inboard arms  102  on the inboard side. A separate cable  405  interconnects all of outboard arms  104  on the outboard side. At the outermost inboard arm  102 , cable  405  is passed through aperture  404 , looped back upon itself, and secured with a cable clamp. If there are three or more inboard arms  102 , cable  405  is looped back and secured at the outermost inboard arms  102 , and passed through aperture  404  of each of the intermediate arms  102 . Alternatively, aperture  404  can be located in inboard arm  102  itself. 
         [0040]    By appropriately setting the attachment point and configuration of tab  403  as well as the location and dimensions of aperture  404 , cable  405  will be positioned as close as possible to the surface of the building. Such positioning of cable  405  necessarily positions the inboard edge of catch  105  as near as possible to the building as well. 
         [0041]    One category of objects that are intended to be caught by catch  105  are those that are accidentally dropped from the base  1001  itself. Another source is the building surface. As one example, during the application of stucco to the side of a building, it can be expected that some amount of stucco applied by a worker will fall away from the building surface. This falling stucco clearly presents a safety hazard. By configuring tab  403  and aperture  404  with respect to inboard arm  102  and wheels  401 , cable  405  and catch  105  can be located as close as possible to the side of the building during use, thereby increasing the likelihood that stucco falling from the surface of the building will fall into catch  105 . 
         [0042]    An inboard edge of catch  105  is then secured along the cable  405  that interconnects inboard arms  102 . An outboard edge of catch  105  is secured along the separate cable  405  that interconnects outboard arms  104 . Catch  105  can be secured by zip ties, clips, or any other similar mechanism that provides for connection with sufficient strength and at a sufficient number of points so that an object dropped over an inboard or outboard edge of base  101  will fall into catch  105  and thereby be prevented from falling below, without tearing catch  105  away from its attachment points. 
         [0043]      FIG. 5  also illustrates wheels  401  attached to distal end  107  of inboard arms  102 . wheels  401  are mounted so as to be rotatable about axle  402 . The diameter of wheels  401  and the position of axle  402  is set so that the extreme distal end of inboard arm  102  does not extend beyond a circumference of wheels  401 . 
         [0044]      FIG. 6  illustrates how the apparatus operates in use. Base  101  can be suspended from cables secured to the roof of a building and operated as a swing-stage scaffold. Alternatively, base  101  can be an element of a mastclimber or a buckhoist. The length of inboard arm  102  is selected so that, with inboard arm  102  at its lowest elevation, wheels  401  make contact with the building when base  101  is in use. In one embodiment, inboard arms  102  are approximately 24″ long. Additionally, the length of inboard arms  102  is selected so that if base  101  moves away from the building within an anticipated range, there remains a sufficient range of motion of inboard arm  102  at its pivoting connection with base  101  that wheels  401  remain in contact with the side of the building. This has the effect of keeping an inboard edge of catch  105  in close proximity to the exterior of the building. 
         [0045]    As catch  105  passes from its inboard edge adjacent the building to distal end  109  of outboard arm  104 , catch  105  operates to prevent any object that might be dropped over the edge of base  101  from falling to the ground. Any such object will fall into catch  105  and collect at the lowest point thereof. In one embodiment, outboard arms  104  are approximately 42″ long. By having outboard arms  104  extend up and away from the outboard side of base  101 , any item that may be placed near the outboard edge of base  101  and accidentally pushed over the edge will fall into catch  105 . 
         [0046]    As base  101  travels vertically up or down along the side of the building, wheels  401  roll along the surface of the side of the building. This has the effect of keeping the inboard edge of catch  105  close to the side of the building. If the base  101  swings away from the building, or the nature of the shape of the building exterior is such that the distance between base  101  and the side of the building increases as base  101  moves up or down with respect to the building, inboard arms  102  automatically adjust to keep the inboard edge of catch  105  adjacent the exterior of the building. 
         [0047]    If the distance between base  101  and the exterior of the building increases, the weight of outboard arms  102  and the attached catch  105  pivots inboard arms  102  downward, maintaining contact between wheels  401  and the exterior of the building, up to a maximum pivoting range allowed for inboard arms  102 . Alternatively, if the distance between base  101  and the exterior of the building decreases, inboard arms  102  will be forced to pivot upward, and hence closer to base  101 . This also has the effect of keeping wheels  401  in contact with the building. 
         [0048]    If the distance between base  101  and the building increases beyond the reach of inboard arm  102 , inboard arm will pivot downward no farther than is allowed by stop  206 . This maintains inboard arm  102  in a position in which is angled upward from horizontal, keeping distal end  107  higher than proximal end  106 . In this way, if base  101  moves beyond a maximum reach of inboard arm  102 , inboard arm  102  remains in its lowermost position. Catch  105  remains in a condition that it continues to be of use, as the inboard edge of catch  105  is held at a distance from the inboard edge of base  101 , so that if an object were to fall over the inboard edge of base  101 , such object would fall into and be trapped by catch  105 . If base  101  then moves back toward the building, distal end  107  again makes contact with the side of the building and inboard arms  102  continue to keep the inboard edge of catch  105  in close proximity to the side of the building. 
         [0049]      FIG. 7  illustrates an axially extendable arm  152 , which can be mounted in a fixed manner to base  101 . In this way the inboard edge of catch  105  is kept in close proximity to the side of the building by the distal end  157  of the axially extendable inboard arm, which automatically extends to maintain contact with the building as the distance between base  101  and the building increases and decreases. In the embodiment illustrated, extendable arm  152  is of a telescoping configuration, with distal section  161  sized to slide within proximal section  162 . Axially extendable arm  152  is urged toward its most fully extended position. This may be achieved by pneumatics, spring force, or any other mechanism that serves to keep the arm in contact with the building. 
         [0050]    Axially extendable arm  152  is shown as having a skid  163  at its distal end. The skid is meant to slide along a surface of the building as base  101  travels up or down. As base  101  swings toward or away from the building, axially extendable arm  152  contracts or expands axially to maintain skid  163  in contact with the building. The same effect results if changes in the contour of the building cause the effective distance between base  101  and the building to change as base  101  moves up or down. 
         [0051]    If base  101  moves sufficiently far from the building so that axially extendable arm  152  reaches its position of maximum extension, the arm remains in this position and holds catch  105  away from base  101 . At such time that base  101  moves back toward the building sufficiently far so that skid  163  again makes contact with the building, skid  163  returns to the condition of maintaining such contact, thereby holding the inboard edge of catch  105  in close proximity to the building. 
         [0052]    While the various embodiments have been shown to have either one or more wheels or a skid at an outermost position of inboard arms, other implementations are possible. Also, the pivoting and fixed but axially extending embodiments for attachment of inboard arms to the base can be replaced with other embodiments and remain within the scope of the present invention. In any event, the inboard arms are to be implemented in such a way that a distal end of the inboard arm can remain in contact or close proximity with the building as the base and building surface move laterally and vertically with respect to one another. Whatever device is used to terminate the inboard arm should provide for contact between the distal end of the inboard arm and the building without catching or binding.

Summary:
A movable platform for supporting a load alongside a structure has an attached catch. The movable structure includes a base having an inboard side and an opposite outboard side, an inboard support extending away from the inboard side of the base, an outboard support extending away from the outboard side of the base, and a catch connected to both the inboard support and the outboard support and passing beneath the base, so that an object dropped over an inboard or outboard edge of the base will be caught by the catch. The inboard support is attached to the base so that a distal end of the inboard support is movable with respect to the base. The distal end is maintained to be in contact with the building exterior. Also described is an accessory for a preexisting movable platform that allows the arms and catch to be attached.