Abstract:
A safety cage improves the safety of workers servicing tanker vehicles having top side hatches. A part or parts of the cage can be repositioned to permit the hatch cover to be opened and then can be returned to a safety enchancing position.

Description:
BACKGROUND OF THE INVENTION 
   When loading tanks of transport trucks it is necessary for a workman to open the hatch or hatches on the tank prior to loading and to close the hatches after loading. The surface of the tank is cylindrical and may be slippery which presents a hazardous condition for the workman. The hatch cover is normally hinged on a horizontal axis extending in the longitudinal direction of the tank and truck and when opened it is desirable to pivot the hatch cover to a fully open position in which the top of the cover rests on the upper part of one lateral side of the tank. If the side railing of a safety cage is spaced laterally outward a sufficient distance to permit the hatch cover to be fully opened, the side railing would be positioned too far laterally to prevent the worker from falling. It also may be too far away to be used by the worker as a grab bar to regain balance or to stop a fall. 
   SUMMARY OF THE INVENTION 
   This safety cage presents a safety railing structure which includes a grab bar section at each lateral side which can be pivoted from its downwardly extending guard position to an upwardly extending position to permit the tank hatch cover to be pivoted to a fully open position at one or the other lateral side of the container. The grab bar section is then pivoted back to its downwardly extending guard position. The safety cage may be attached to an adjustable stairway with self leveling steps which in turn is mounted on an access platform. The adjustable stairway permits lowering of the cage to a safety enhancing position and provides upward adjustment of the position of the cage so as to not interfere with the truck moving into its position for opening or closing the hatch. Once the truck is in its servicing position the safety cage is lowered by downwardly adjustment of the stairway to afford the worker access and protection. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One embodiment of the invention is illustrated in the drawings in which: 
       FIG. 1  is a front view of an access platform, the adjustable stairway and the safety cage positioned above the hatch of a bulk material tank mounted on a truck; 
       FIG. 2  is a top view of the safety cage and the adjustable stairway shown in  FIG. 1 ; 
       FIG. 3  is a side view of the safety cage taken on line  3 — 3  in  FIG. 2 ; 
       FIG. 4  is a side view of the safety cage taken on line  4 — 4  in  FIG. 2 ; and 
       FIG. 5  is a rear view of the safety cage taken in line  5 — 5  in  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates a tanker vehicle in the form of a bulk material tank truck  11  positioned for servicing at a hatch opening and closing station which includes a worker access or service platform  12  with a floor  13 , supported by one or more pillars  14 , and a ladder  16 . Typical bulk material handling tanker vehicles have a hatch  17  on the top of a tank  18  with a hatch cover  19  which is pivotally hinged to the hatch  17  on a horizontal axis  21  extending in the longitudinal direction of the vehicle, that is, in a fore and aft direction. The open position of the hatch cover is shown by broken lines  22 . 
   In order to enhance the safety of workmen who open and close the hatches of the tanker vehicles, a safety cage  31  is provided, which is designed to be placed in encompassing relation to the hatch  17 . The safety cage  31  is supported on the free end of a gangway in the form of an adjustable access stairway  32  having self leveling steps. As shown in  FIG. 1 , the access stairway  32  has been lowered by extension of a pair of hydraulic actuators  33 , to its safety enhancing position in which the bottom of an offset portion  40  of the safety cage  31  is near or adjacent to the hatch  17  on the top of the tank  18  of the tank truck  11 . 
   Referring also to  FIGS. 2 through 5 , the safety cage  31  is a quadrilateral shaped enclosure which includes a worker access opening  36  at one end of a first lateral upright side  37 , as shown in  FIGS. 1 and 3 . The safety cage also includes a front side  38  shown in  FIG. 1 , a second lateral side  39  shown in  FIG. 4  and a rear side  41  shown in  FIG. 5 . As shown in  FIG. 2  the safety cage  31  has an offset portion  40  with the front side  38  and the lateral sides  37 ,  39  in a safety enhancing position shown in  FIGS. 1 and 2 . The safety cage  31  includes a horizontal upper tube  46  and a horizontal intermediate tube  47  which are parallel to one another and extend in vertical alignment with one another about the cage with their opposite ends rigidly secured as by welding to vertical mounting brackets  48 ,  49  by which the safety cage  31  is rigidly secured to upright posts  51 ,  52  at the end of the stairway  32 . The upper tube  46  forms an upper guard rail  53  of the front side  38 , an upper guard rail  54  of the rear side  41 , an upper guard rail  56  for the first lateral side  37  and an upper guard rail  57  for the second lateral side  39 . The intermediate tube  47  forms an intermediate guard rail  61  of the front side  38 , an intermediate guard rail  62  of the rear side  41 , an intermediate guard rail  63  of the first lateral side  37  and an intermediate guard rail  64  of the second lateral side  39 . 
   The safety cage  31  has a lower guard rail structure which includes a lower guard rail  66  on the front side  38 , a lower guard rail  67  on its rear side, and a lower guard rail  68  on part of its second lateral side  39 . The lower guard rail structure for the safety cage  31  also includes shiftable grab bar sections  71 ,  72  which have horizontal guard rails or grab bars  73 ,  74 , respectively, disposed at the same height as the bottom guard rails  66 ,  67 ,  68 . The grab bar section  71  has vertically extending arms  76 ,  77  which rigidly interconnect opposite ends of the grab bar  73  with a horizontal support member  78 . A pair of parallel upstanding legs  81 ,  82  are rigidly secured at their lower ends to the support member  78  and extend upward on the laterally inward side of the first lateral side  37  to upper ends pivotally connected on a longitudinally extending horizontal axis  79  to a pair of vertical struts  83 ,  84 , respectively, extending between the upper guard rail  56  and the intermediate guard rail  63 . The grab bar section  72  has a pair of vertically extending arms  86 ,  87  which rigidly interconnect opposite ends of the grab bar  74  with a horizontal support member  88 . A pair of parallel upstanding legs  91 ,  92  are rigidly secured at their lower ends to the support member  88  and extend upward on the laterally inner side of the second lateral side  39  on a longitudinally extending horizontal axis  93  to a pair of vertical spacing struts  94 ,  96  between the upper guard rail  57  and the intermediate guard rail  64 . Addition struts  97 ,  98 ,  99 ,  101 ,  102  interconnect the top tube  46  to the intermediate tube  47 . The intermediate guard rail  63  serves as an abutment which prevents the grab bar section  71  from swinging laterally outward from its downward extending guard position shown in  FIG. 2 ,  3  and  5 . In a like manner the intermediate guard rail  64  serves as an abutment for the grab bar section  72 , preventing it from swinging laterally outward from its downwardly extending safety position shown in  FIGS. 2 ,  4  and  5 . 
   In performing servicing operations, the gangway or stairway  32  is placed in a raised position by contraction of the hydraulic actuators  32  thereby elevating the safety cage  31 . The tank truck  18  is driven beneath the safety cage  31  and the safety cage is lowered to its safety enhancing position shown in  FIG. 1 . In this position of the safety cage  31  the hatch cover  19  can not be pivoted to its open position shown in broken lines  22  because the grab bar sections  71 ,  72  are spaced laterally from the hatch cover a distance less than the width of the hatch cover  19 . However, upon pivoting the grab bar section  72  to the position shown in broken lines  72 ′ the hatch cover  19  can be opened. The safety cage  31  is then raised and the truck  11  is driven to a loading station, not shown, to receive bulk material such as cement. The loaded tank truck  11  is then driven back to the servicing station where a workman closes the hatch cover  19 ; at which time the grab bar section  71  is pivoted to its raised position shown by broken line  71 ′ to permit the hatch cover  19  to be closed-assuming the truck  11  is headed in the opposite direction upon its return to the servicing station.