Abstract:
A portable bleacher construction includes a wheeled framework for supporting a plurality of bleacher seats thereon in a mobile travel condition and a stationary seating condition. At least one pair of leveling jacks is located on opposite sides of the framework for stabilizing and leveling the framework upon a ground surface when the portable bleacher construction is in the stationary seating condition. The jacks are arranged to provide a four-point stance for the framework, and have a high sway load capacity to provide lateral stability. A control arrangement is associated with one of the jacks in each pair for separately controlling the leveling of both of the jacks. The control arrangement is located on one side of the bleacher construction, and enables operation of leveling jacks on both sides. The control arrangement includes a pair of transfer rods and a separate operating handle interconnected with each transfer rod. One of the transfer rods provides an input to the jack with which the control arrangement is associated, and the other transfer rod extends across the bleacher construction and provides an input to the opposite jack.

Description:
FIELD OF THE INVENTION 
     This invention relates broadly to a portable bleacher construction and, more particularly, pertains to a jack system for leveling and stabilizing a portable bleacher in a stationary position upon a ground surface. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     There are various instances where events, particularly outdoor events, are to be staged which require the availability of seating for a viewing audience. Permanent seating, such as bleachers, can be constructed for events which are always held in the same place. For one-time events or less frequent events, temporary seating such as portable bleachers can be employed. Portable bleachers can also be used to supplement existing permanent seating to increase seating capacity, if desired, for certain events. One of the characteristics of such portable seating is that the mobile framework carrying the seating must be stabilized and leveled on ground surfaces which are frequently uneven and vary from site to site. 
     Portable bleacher constructions are known in which one section of seating is permanently fixed to a wheeled framework and at least one other section of seating is pivotally mounted thereto. Hydraulic cylinders or other mechanical devices are often used to pivot the movable section between a nested, travel position and an operative, seating position. In order to stabilize and level the bleacher construction prior to use, it has been the practice to install a plurality (i.e. 10-14) of individually operated jacks along the framework. Typically, the jacks are installed such that a series of jacks are located on each side of the framework. In operation, the operator must swivel each jack down from a storage mode, and then each jack must be manually cranked from a squatting or kneeling position to adjust for the particular terrain, to stabilize and level the portable bleacher. This necessitates that an operator will expend a great deal of time and energy adjusting the jacks on each side of the framework. 
     Accordingly, it would be desirable to markedly reduce the labor-intensive efforts required in deploying and individually adjusting the jacks employed in a portable seating arrangement. It would also be desirable to shorten the time needed to efficiently effect leveling of the mobile framework supporting the portable seating. 
     It is one object of the present invention to provide a portable bleacher construction equipped with a stabilizing jack system in which an operator can control the deployment and operation of the jacks to stabilize and level the portable bleacher construction with a minimum of time and effort. 
     It is also an object of the present invention to provide a portable bleacher framework with at least one pair of leveling jacks on opposite sides of the framework such that a control arrangement on one side of the framework is employed to independently adjust the positioning of both jacks. 
     It is a further object of the present invention to provide a stabilizing jack system for a portable bleacher in which a plurality of jacks disposed on each side of the portable bleacher framework may be operated in a standing position from one side of the framework. 
     In one aspect of the invention, a portable bleacher construction includes a wheeled framework for supporting a plurality of bleacher seats thereon in a mobile travel condition and a stationary seating condition. At least one pair of leveling jacks is located on opposite sides of the framework for stabilizing the framework in the seating position upon a ground surface. The invention contemplates a small number of high-capacity jacks in selected locations on the framework, to provide ease of operation and to increase stability to the portable bleacher construction. In a preferred form, four jacks are mounted to the framework to provide a stable stance, and each jack has a high sway load capacity to provide a high degree of lateral stability. In a particularly preferred form, a control arrangement is located on one side of the framework for separately controlling the deployment and leveling of both jacks in each pair of jacks. The framework includes a pair of parallel, spaced longitudinal beams interconnected by a pair of transverse end beams. A pair of wheel assemblies are located one on each of the longitudinal beams between the transverse end beams. Each jack is mounted to one of the longitudinal beams. Each jack has an upper tubular member affixed to one of the beams, and a lower tubular member with a ground engaging foot telescopically received and movably mounted in the upper tubular member for upward and downward movement relative thereto. The control arrangement is preferably interconnected with one of the jacks in each pair, and is located on a rear one of the longitudinal beams. 
     In one form, the control arrangement includes a first rotatable crank assembly and a second rotatable crank assembly movably mounted on an upper end of the upper tubular member of the jack disposed on the rear longitudinal beam. Each crank assembly is operably interconnected with one of the jacks, and the crank assemblies are operable to move the lower tubular members of the jacks on opposite sides of the framework upwardly and downwardly independent of each other. The first rotatable crank assembly has a first S-shaped handle pivotally mounted to a shortened transfer rod projecting into the upper end of the upper tubular member of the jack disposed on the rear longitudinal beam. The second rotatable crank assembly has a second S-shaped handle pivotally mounted to an elongated transfer rod extending from the jack on the rear longitudinal beam to the jack on the front longitudinal beam. The upper tubular member of the jack on the rear longitudinal beam includes clamp structure adapted for engagement with the first handle and the second handle for selectively retaining the first handle and the second handle in an inoperative position when not in use. The first handle and the second handle are disengaged from the clamp structure and pivoted upwardly on their respective transfer rods to an operative position, after which the handles are separately rotated to turn the transfer rods and operate the jacks, to effect movement of the lower tubular members against the ground surface. In a preferred form, at least one pair of jacks is located between the wheel assemblies and one of the transverse end beams, and another pair of jacks is located between the wheel assemblies and the other of the transverse end beams. 
     The invention also contemplates a portable bleacher construction having a mobile framework for supporting a plurality of bleacher seats thereon, and a plurality of pairs of leveling jacks located on opposite front and rear sides of the framework for stabilizing the framework on a ground surface when the framework is stationary. The invention includes a control station commonly located on each jack position on one side of the framework for allowing independent adjustment of each pair of jacks on the front and rear sides of the framework. The control station includes a pair of side-by-side, manual crank assemblies disposed upon an upper end of each jack positioned on one side of the framework. Each of the manual crank assemblies has a handle which is pivotable about a first horizontal axis extending generally parallel to the longitudinal axis of the framework, and is rotatable about a second horizontal axis extending generally perpendicularly to the first horizontal axis. The control station is preferably located on the rear side of the framework. 
     Various other objects, features and advantages of the invention will be made apparent from the following description taken together with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings illustrate the best mode presently contemplated of carrying out the invention. 
     In the drawings: 
     FIG. 1 is a rear isometric view of a portable bleacher construction having a stabilizing jack system embodying the present invention; 
     FIG. 2 is an enlarged, detailed partial isometric view of one of the stabilizing jacks incorporated in the portable bleacher construction, with reference to line  2 — 2  of FIG. 1; 
     FIG. 3 is a partial top view taken on line  3 — 3  of FIG. 2; and 
     FIG. 4 is a partial sectional view taken on line  4 — 4  of FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, a portable bleacher construction  10 , as seen from the rear, has a mobile framework  12  comprised of a pair of parallel, front and rear longitudinal beams  14 ,  16 , respectively, interconnected by a pair of transverse end beams (one of which is seen at  18 ). A multiplicity of parallel, transverse intermediate beams (one beam being seen at  20  in FIGS.  3  and  4 ,) extends between the front and rear longitudinal beams  14 ,  16 . The mobile framework  12  includes a pair of tandem wheel assemblies  22 ,  24  outside each of the front and rear longitudinal beams  14 ,  16 . A tongue  26  is provided on one transverse end beam  18  to permit the framework  12  to be connected to a tractor vehicle (not shown) such as an automobile, truck, van or tractor so that the framework  12  can be moved in a direction parallel to its length or longitudinal axis. 
     Framework  12  carries a lower, fixed bleacher section  28  to which an upper movable bleacher section (not shown) is pivotally mounted in a manner as is well known. Normally, the movable bleacher section is carried in a nested position when the framework  12  is in a mobile travel condition, and is pivoted into an operative seating position when the framework  12  is stationary. Fixed bleacher section  28  includes a series of horizontal seating stringers  30  which extend along the length of the framework  12 . Depending from the seating stringers  30  is a set of vertical support posts  32  which are joined at their lower ends to a number of angled support members  34 . The lower, front end of the support members  34  terminate at a vertical front support member  36  (FIG.  4 ). A group of horizontal tubular braces  38  extend across the top of the front and rear longitudinal beams  14 ,  16 . A rear end of each horizontal brace  38  is connected to a rear support post  40  which projects vertically from the rear of framework  12 . A fence-like railing  42  is secured to the rear support posts  40  and extends above the top seating stringer  30  to provide a guard and backrest for persons seated at the top row of fixed bleacher section  28 . Fence-like railings  44 , which include a stationary upper section and a movable lower section, are provided on each end of the framework  12 , to provide a guard for the ends of portable bleacher construction  10 . 
     To support portable bleacher construction  10  in use, portable bleacher construction  10  includes a first pair of corresponding leveling jacks  46 ,  48  and a second pair of corresponding leveling jacks  50 ,  52  mounted to framework  12 . Jacks  46 - 52  are of heavy duty construction, and function to relieve the load on wheel assemblies  22 ,  24 . In one form, jacks  46 - 52  may be such as are typically employed for semi-trailer landing gear. The four jacks  46 - 52  provide a stable four-point stance, and have a high sway load capacity to provide lateral stability. 
     Jacks  46 ,  48  are disposed on opposed front and rear longitudinal beams  14 ,  16 , respectively, at a location between transverse end beam  18  and wheel assemblies  22 ,  24 . Jacks  50 ,  52  are disposed on front and rear longitudinal beams  14 ,  16 , respectively, at a location between the other transverse end beam (opposite end beam  18 ) and wheel assemblies  22 ,  24 . Jacks  46 ,  48 , as seen in FIG. 2, include respective upper tubular members  54 ,  55  and lower tubular members  56 ,  57  telescopically received and slidably mounted for upward and downward movement in the upper tubular members  54 ,  55 . In the following description, only the details of jacks  46 ,  48 , are set forth, it being understood that the structure and function of jacks  50 ,  52  is identical. Although not shown, each jack  46 ,  48 ,  50 ,  52  has a conventional internal mechanism, such as a rack and pinion or the like, which allows a rotational force imparted to an operating member to be transferred into linear vertical movement of the lower tubular members such as  56 ,  57 , relative to their respective upper tubular members such as  54 ,  55 . 
     Referring to FIGS. 2 and 4, each of the front and rear longitudinal beams  14 ,  16  is a rigid load bearing member which may be C-shaped in cross section, or which may have any other shape, in a manner as is known. Front longitudinal beam  14  includes an upper flange  58  and a lower flange  60  interconnected by a web  62 . Rear longitudinal beam  16  has an upper flange  64  and a lower flange  66  joined by a web  68 . Jack  46  is installed inwardly of front longitudinal beam  14  and front vertical support member  36 . Jack  48  is mounted outwardly of rear longitudinal beam  16  and rear support posts  40 . 
     Upper tubular member  54  of jack  46  is fixedly connected to front longitudinal beam  14  by a pair of upper and lower angle brackets  70 ,  72 , respectively. Upper bracket  70  has a vertical leg  74  secured to an upper portion of a sidewall  76  of upper tubular member  54 , and a horizontal leg  78  fixed, such as by a series of fasteners  79  (FIG.  3 ), to the top of upper flange  58  of front longitudinal beam  14 . Lower bracket  72  has a vertical leg  80  attached to a lower portion of sidewall  76  of upper tubular member  54 , and a horizontal leg  82  fixed to the bottom of lower flange  60  of front longitudinal beam  14 . 
     In a similar manner, upper tubular member  55  of jack  48  is anchored to rear longitudinal beam  16  by a pair of angle brackets  84 ,  86 , respectively. Upper bracket  84  has a vertical leg  88  secured to an upper portion of a sidewall  90  of upper tubular member  55 , and a horizontal leg  92  fixed, such as by a series of fasteners  93 , to the top of upper flange  64  of rear longitudinal beam  16 . Lower bracket  86  has a vertical leg  94  attached to a lower portion of sidewall  90  of upper tubular member  55 , and a horizontal leg  96  attached to the bottom of lower flange  66  of rear longitudinal beam  16 . 
     Each of the lower tubular members  56 ,  57  has a cross section which is smaller than that of respective upper tubular members  54 ,  55  so as to enable the sliding relationship therebetween. In addition, each of the lower tubular members  56 ,  57  has a suitable length such that respective feet  98 ,  100  at the lower end thereof will be engageable with the ground surface  102 , which is shown as being uneven in FIG.  4 . 
     In accordance with the invention, there is a control station or arrangement  104  on each jack  48 ,  52  positioned on one side of the framework  12  for allowing independent adjustment and leveling of each corresponding pair of jacks  46 ,  48  and  50 ,  52  on the respective front and rear beams  14 ,  16  of the framework  12 . Because each control arrangement  104  on jacks  48 ,  52  is identical, only the control arrangement  104  on jack  48  (as shown in FIG. 2) will be described. 
     Control arrangement  104  includes a first rotatable crank assembly  106  and a second rotatable crank assembly  108  movably mounted in side-by-side relationship on the upper end of the upper tubular member  55  for moving the lower tubular members  56 ,  57  on opposite sides of the framework  12  upwardly and downwardly separately from each other. The first rotatable crank assembly  106  has a first S-shaped handle  110  with a slotted, bifurcated upper end  112  pivotally mounted to a transverse pin  113  (FIG. 3) mounted to an outer end of a shortened, rotatable transfer rod  114 . The rod  114  projects through a bearing collar  115  on sidewall  116  and projects into the interior of upper tubular member  55  where it is operably connected to a suitable internal mechanism, such as the drive pinion of a rack and pinion mechanism, for raising and lowering the lower tubular member  57 . 
     An L-shaped bracket  117  is connected to the upper end of the upper tubular member  55 . Bracket  117  has an attachment flange  118  anchored to sidewall  119  in any satisfactory manner, such as by welding, and an apertured support flange  120  which carries a bearing collar  122 . The second rotatable crank assembly  108  has a second S-shaped handle  124  with a slotted, bifurcated end  126  pivotally secured to a transverse pin  127  mounted to an outer end of an elongated, rotatable transfer rod  128 . The rod  128  passes through the bearing collar  122  and support flange  120  and extends across the width of framework  12  through another bearing collar  130  on upper tubular member  54  of corresponding jack  46 . The end of rod  128  projects into the interior of upper tubular member  54  where it is operably connected to a suitable internal mechanism, such as the drive pinion of a rack and pinion mechanism, for raising and lowering lower tubular member  56 . Control arrangement  104  includes a pair of spring-type clamp retainers  132 ,  134  mounted to upper tubular member  55  for retaining the handles  110 ,  124 , respectively, in an inoperative position against adjacent sidewalls  116 ,  119 . 
     In use, when portable bleacher construction  10  is placed in a stationary position in preparation for use, as shown in FIG. 1, the framework  12  must be stabilized and leveled relative to the prevailing ground surface  102 . Jacks  46 - 52  are in a retracted position during transport, in which lower tubular members  56 ,  57  are fully retracted into respective upper tubular members  54 ,  55 , and are extended in order to stabilize and level framework  12 . To extend jacks  46 - 52 , an operator successively disengages the handles  110 , from respective clamp retainers  132 ,  134 , pivots the particular handle  110  or  124  upwardly about horizontal axis A and then rotates the handle to rotate the transfer rod  114  or  128  to extend the lower tubular members  56  or  57  into engagement with the ground  102 . This procedure is carried out for both pairs of jacks  46 ,  48  and  50 ,  52 , as necessary to extend all jacks  46 - 52  into engagement with the ground and to then adjust jacks  46 - 52  as necessary to level framework  12 . 
     FIGS. 3 and 4 illustrate the procedure for independently controlling jack  46  on front longitudinal beam  14 . After handle  124  is pivoted on horizontal axis A, it is rotated to turn the elongated transfer rod  128  about the longitudinal axis of rod  128 , which is generally perpendicular to the first horizontal axis A. Turning of rod  128  causes the internal mechanism of jack  46  to extend and retract lower tubular member  56 . When jack  46  is suitably adjusted, the operator pivots handle  124  downwardly about horizontal axis A and handle  124  is reengaged with clamp retainer  134 . As a feature of the invention, the operator, without having to change location, disengages handle  110  and performs a similar operation to adjust the jack  48  on rear longitudinal beam  16 . Handle  110  is then reengaged with clamp retainer  132  and the operator simply moves along the rear longitudinal beam  16  until he reaches the jack  52 . Again, the handles  110 ,  124  on jack  52  are separately manipulated as described above to independently adjust the lower tubular members of jacks  50 ,  52 . This procedure is repeated as necessary until framework  12  is completely stabilized and leveled. 
     While jacks  46 - 52  are illustrated and described as manually operated telescoping type jacks, it is understood that any type of jack may be employed, including (but not limited to) hydraulic jacks, electric jacks, screw-type jacks, scissors-type jacks, etc. 
     It should thus be appreciated that the control arrangements  104  permit efficient stabilization and leveling of the portable bleacher construction  10  with a minimum of time and effort. The operator is able to operate jacks  46 - 52  to level the mobile load upon variable ground surfaces from one side only (preferably the rear) of the framework  12 . Control arrangements  104  are constructed and arranged so as to be easily manipulated by an operator in a comfortable standing position. In addition, the use of four jacks, each of which is located at one comer of framework  12 , ensures that each jack is in engagement with the ground and carries its share of the load of bleacher construction  10 . In the prior art arrangement, adjustment of one of the series of jacks mounted to each beam  14 ,  16  could alleviate the load on others of the jacks, making it difficult to ensure engagement of all jacks while maintaining a level attitude of bleacher construction  10 . 
     Control stations or arrangements  104  have been shown and described as being located on jacks  48 ,  52  at the rear of portable bleacher construction  10 . It is understood, however, that control stations or arrangements  104  may also be located at the front of portable bleacher construction  10 , or one at the front and one at the rear. It is preferred, however, to provide both control stations or arrangements  104  on the same side, to facilitate quick and easy operation of jacks  46 - 52 . 
     In addition, while the invention has been shown and described with respect to two pairs of jacks, it is understood that additional jacks or pairs of jacks may be employed between those jacks which define the four-point stance, as necessary according to length spans or load requirements. 
     While the invention has been described with reference to a preferred embodiment, those skilled in the art will appreciate that certain substitutions, alterations and omissions may be made without departing from the spirit thereof. Accordingly, the foregoing description is meant to be exemplary only, and should not be deemed limitative on the scope of the invention as set forth in the following claims.