Abstract:
An elevating conveyor is mounted to a pivoting bridge so that the elevating conveyor can be shifted by a 22 degree rotation between a lowered position in engagement with a loading floor and an elevated storage position where the conveyor is out of the way of the loading floor. A counterweight arrangement is mounted to the bridge to bias the conveyor toward the loading floor when it is in a lowered position, and to bias it toward the elevated storage position when it is in the up position. The conveyor may be readily moved between the positions with a moderate application of force. The force may be applied by an operator standing on the loading floor or by a liner actuator mounted between the bridge and a fixed structure.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to conveyors in general and to in particular to elevating conveyors which can be retracted for storage. 
     Conveyor systems have been developed for both speedy and efficient loading or unloading of packages or containers from or to transportation vehicles or storage areas. The packages and or containers are typically not sorted or only partially sorted when they arrive and are loaded unloaded in the most convenient sequence, normally starting with those most accessible, and fed onto an elevating conveyor which delivers the packages or containers to a sorting conveyor above the working floor which distributes individual packages or containers to workstations on the working floor below, where the packages or the containers&#39; contents may be further sorted. Because delivery of packages is not generally continuous, the elevating conveyor is typically pivoted to a horizontal elevated position, for safety and convenience reasons, to remove the elevating conveyor from the ground or working floor space when it is not in use. In existing systems a chain fall, wire drum winch, or, pneumatic cylinder is used to elevate the lower loading side of the elevating conveyor. The chain fall or other hoist rotates the elevating conveyor about a pivot mounted at the discharge end where the elevating conveyor discharges to the elevated sorting conveyor. The chain fall or hoist represents an additional cost an inconvenience and a possible obstacle to workers. 
     SUMMARY OF THE INVENTION 
     The elevating conveyor of this invention is mounted to a bridge which is counterweighted and turns about an overhead pivot shaft. The bridge supports the elevating conveyor so both the bridge and the elevating conveyor pivot about the same overhead pivot shaft. The bridge extends in part above and beyond the pivot shaft and terminates in a bracket for mounting a counterweight. The elevating conveyor is mounted to a part of the bridge which extends below the pivot and is arranged to pivot 22° about the pivot shaft between a loading position resting on the work floor and an elevated storage position where the conveyor and bridge are approximately parallel to the work floor. The bridge counterweight is spaced away from the pivot by the part of the bridge extending beyond the pivot shaft and is mounted on the counterweight bracket spaced upwardly of a plane containing the elevating conveyor. The counterweight thus arranged has a center of gravity which moves toward the pivot point more than the center of gravity of the counterbalanced weight on the opposite side of the pivot. This movement is selected so the total center of gravity of the bridge and elevating conveyor when in the down position produce a downward force on the floor amounting to about 30 pounds, whereas in the up position a comparable force amounting to about 30 pounds holds the conveyor in an up or storage position. The elevating conveyor has a leg at its lower end which holds the conveyor at an ergonomic height above the work floor e.g., 2 feet 8½ inches, for loading with boxes or cartons. 
     The bridge and the elevating conveyor are arranged so it can be raised with 30 pounds lifting force, or lowered by reaching up and pulling the conveyor down with a 30 pound force. The bridge may be moved by a linear actuator, for example an electromechanical type actuator. A spring activated brake is failsafe, requiring electrical power to release the brake so that the bridge and elevating conveyor are positively prevented from movement when power fails or is off. 
     It is an object of the present invention to provide an elevating conveyor which is simpler and more easily operated and which provides safety benefits. 
     It is a further object of the present invention to provide a pivoting bridge which supports an elevating conveyor which is mechanically arranged to be stable in the up or down position. 
     Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view of a elevating conveyor on a counterweighted support bridge of this invention. 
         FIG. 2  is a side elevational schematic view showing the operation and mass properties of the elevating conveyor on the counterweighted support bridge of  FIG. 1 . 
         FIG. 3  is a top plan view of the elevating conveyor of  FIG. 1 . 
         FIG. 4  is a side elevational view of the elevating conveyor on the counterweighted support bridge of  FIG. 1  in the up position. 
         FIG. 5  is a fragmentary side elevational view showing an electromechanical actuator for controlling the movement of the counterweighted support bridge of  FIG. 1 , showing the conveyor in the down position. 
         FIG. 6  is a fragmentary side elevational view of the apparatus of  FIG. 5 , showing the support bridge in the up position. 
         FIG. 7  is a fragmentary front elevational view of the apparatus of  FIG. 1 . 
         FIG. 8  is a fragmentary cross-sectional side of the device of  FIG. 1 , taken along section line  8 - 8  and showing a pin lock on the pivot shaft. 
         FIG. 9  is a fragmentary rear elevational view of the device of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring more particularly to  FIGS. 1-9  wherein like numbers refer to similar parts, a conveyor system  20  is shown in  FIG. 1 . The conveyor system  20  is mounted to extend between a loading floor  22  and an upper platform or distribution level  24 . The conveyor system  20  comprises a bridge structure  28  and an elevating conveyor mounted to the bridge structure. The bridge structure is itself mounted to a pivot shaft  32  on the upper platform  24  so the bridge can pivot about a horizontal axis to pass through a vertical plane  30  which extends through the pivot shaft. The elevating conveyor  34  is arranged to transport packages or cartons  36  from a loading section  38  at a lower end  39  of the elevating conveyor to an elevated conveyor  26 . The bridge  28  supports the elevating conveyor  34  when the bridge and the elevating conveyor are in the down position as illustrated in  FIG. 1 . The bridge  28  has a first portion  42  which supports a counterweight  44  and a second portion  40  which supports the elevating conveyor  34  and which is opposite the first portion with respect to the pivot, bearing or shaft  32 . The loading section  38  at the lower end  39  of the elevating conveyor  34  is supported by a leg  46  on the loading floor  22 . 
     The bridge  28  moves between the lowered position shown in  FIG. 1  to an elevated position shown in  FIG. 4  where the bridge rests on a stop  48 . The elevating conveyor  34  may be any type of conveyor e.g., rolls or belts, but is shown in  FIG. 1  as a series of belt conveyors  50  arranged with conventional sensors and controls to detect the presence of packages, cartons, or trays  36 , and control the plurality of belt conveyors  50 . The elevating conveyor  34  supports a guide bar  52 , shown in  FIG. 8 , to prevent cartons  36  from tipping and falling off the elevating conveyor  34 . 
     The schematic view of  FIG. 2  represents the bridge  28  and the elevating conveyor  34  in the up position as a horizontal straight line  54  with a counterweight  44  positioned on an upper end  56  of the bridge. The counterweight  44  is elevated above the upper end  56  of the bridge, as illustrated schematically in  FIG. 2  and as illustrated in detail in  FIGS. 5 ,  6  and  9 . As shown in  FIG. 2 , the center of gravity (cg)  58  of the first portion  42  is positioned above the line representing the bridge  28  and elevating conveyor  34 , whereas the center of gravity (cg)  60  of the second portion  40  of the bridge and the elevating conveyor are positioned on the line  54 . Referring to the straight line  54  of  FIG. 2  representing the bridge  28  and the elevating conveyor  34 , a total center of gravity (total cg)  62  of the combination bridge and elevating conveyor is positioned over the first portion of the bridge  42 , to the right as shown in  FIG. 2 , of the pivot shaft  32  and therefore biases the bridge and elevating conveyor in the up position as shown in  FIG. 4 , and schematically as the horizontal line  54  of  FIG. 2 . When the conveyor is in the down position as illustrated by the sloping line  64  in  FIG. 2 , the (cg)  58  of the first portion  42  of the bridge  28 , and the (cg)  60  of the second portion  40  of the bridge and the elevating conveyor, both move toward the pivot  32 . However because the counterweight  44  is elevated above the horizontal line  54  the cg of the first portion  42  moves a greater distance toward the pivot  32  than the cg of the second portion  40  moves toward the pivot so that the total cg  62  of the bridge  28  and elevating conveyor  34  moves to the left in  FIG. 2  to be on the downward side of the pivot  32 , thus biasing the bridge and elevating conveyor in the down position represented by the line  64  in  FIG. 2 . In the down position, as shown in  FIG. 1 , the support leg  46  extends from the lower end of the bridge and conveyor to engage the loading floor  22 . 
     The result of the position of the counterweight  44  in an elevated position on the upper end  56  of the bridge  28  is to create a mechanical arrangement wherein the bridge and elevating conveyor  34  has two stable positions: a down position, as shown in  FIG. 1 , where the elevating conveyor leg  46  is biased against the loading floor  22 ; and an up position, shown in  FIG. 4 , where the bridge first portion  42 , on the opposite side of the pivot, is biased against the stop  48 . The bridge  28  and elevating conveyor  34  can be stably positioned either raised or lowered with very little force, for example by simply pulling the elevating conveyor  34  down by means of the conveyor leg  46 , until the total cg  62  is on the lower side of the pivot  32 , or by lifting the elevating conveyor  34  up until the total cg  62  passes to the upper side of the pivot  32  and the bridge  28  and the elevating conveyor  34  pivot to the up position shown in  FIG. 4 . Typically the size and positioning of the counterweight  44  are selected so that a gravitational biasing force of approximately 20-80 pounds is created to hold the bridge  28  and elevating conveyor  34  in both the up and down positions. 
     As shown in  FIGS. 5 ,  6 , and  9  the movement of the bridge  28  can also be controlled by a linear actuator  66 , shown as an electromechanical actuator, to overcome the small gravitational biasing force to move the bridge  28  and elevating conveyor  34  between the up and down positions. As best shown in  FIG. 9 , the counterweight  44  is comprised of a plurality of individual weights  68  which are mounted over threaded support rods  70  which connect with outboard flanges  72  welded or mounted to the upper end  56  of the bridge  28 . Holes in the flanges  72  receive the threaded support rods  70  which pass through holes in the individual weights  68 . Nuts  74  are threadedly engaged with the rods  70  to clamp the individual weights  68  to the flanges  72  of the counterweight brackets  75  to form the counterweight  44 . Additional nuts  74  are positioned above the counterweight  44  on the threaded supports  70  and engage an attachment flange  76 . This arrangement of the threaded supports  70  and the nuts  74  allows the counterweight  44  to be adjusted for changes in the weight of the elevating conveyor  34 . The linear actuator  66  is pivotally mounted to the attachment flange  76  and pivotally mounted to the upper platform  24  so that the actuator  66  may rotate with respect to both the attachment flange and a mounting point  78  on the upper platform. An electric motor  80 , as shown in  FIG. 6 , drives the linear actuator  66  to raise and lower the bridge  28  with a relatively small force of, for example, 30 pounds positive to 30 pounds negative force as the bridge  28  moves from a horizontal position (shown in  FIG. 6 ) to a lowered functional position (shown in  FIG. 5 ). In the lowered functional position the bridge is positioned with an approximately 22° negative slope with respect to the pivot  32 , and the elevating conveyor  34  engages the loading floor  22  with the support leg  46 . 
     In order to minimize a gap  82  which opens between the elevating conveyor  34  and the elevated conveyor  26 , the conventional conveyor units which are used to construct both conveyors must be modified to allow for the conveying surface  84  of the elevating conveyor  34  to more closely approach the conveying surface  86  on the elevated conveyor  26 . Specifically, the support structure  88  of the conveying unit  90  of the elevating conveyor  34  closest to the pivot  32  has a cutaway  92  as shown in  FIGS. 5 and 6 . The cutaway  92  allows the conveying surface  84  to overlie the pivot shaft forming the pivot  32 , particularly in the elevated position shown in  FIG. 6 . Similarly the elevated conveyor  26  conveying unit  94  closest to the pivot  32  has a cutaway  96  in the support structure of the conveying unit. The cutaway  96  allows the conveying surface  86  to overlie the shaft forming the pivot  32 . Thus when the bridge  28  and elevating conveyor  34  are in the elevated position, shown in  FIG. 6 , the conveying surface  84  abuts or closely abuts the conveying surface  86  of the elevated conveyor  26 , and when the bridge and elevating conveyor are in the lowered position shown in  FIG. 5 , a gap  82  is minimized. 
     As shown in  FIG. 5 , the bridge  28  has a king post  98  extending upwardly from a structural base  100 , to an upper end  103 , and has connecting members  102  connected to the upper end of the king post  98  which form a truss between the upper end  56  of the bridge and the lower end  104  of the bridge. 
     Although the bridge  28  is stabilized in the upper and lower positions by a force e.g., 30 lbs, a spring loaded brake  106  is shown in  FIG. 9  mounted to lock the pivot shaft  32  to the upper platform  24 . The brake, for example a disk brake, is engaged by the spring to lock the bridge  28  against movement unless power is available and applied to an electromechanical actuator (not shown) to overpower the spring and release the brake  106 . 
     It should be understood that the bridge  28  while shown as having king posts  98  and connecting members  102  forming trusses between the upper end  56  of the bridge and the lower end  104  of the bridge, this configuration may be replaced with any suitable structural arrangement which provides the necessary strength and stiffness and structural efficiency to the bridge  28 . 
     It should also be understood that the support leg  46  may also be pivotally mounted to the lower end  39  of the elevating conveyor  34 , so that the leg may be retracted by a linear actuator such as a motor driven linear actuator similar to but smaller than the actuator  66  which raises and lowers the bridge  28 . 
     It should also be understood that the vertical position of the counterweight  44  can be raised by additional nuts  74  positioned above the flanges  72  to support the counterweight in a more elevated position as another variable in positioning the counterweight to control how the total cg  62  moves as the bridge  28  and the elevating conveyor  34  are tilted. The counterweight  44 , as shown in  FIG. 9 , is arranged to provide an even biasing force to hold the bridge in the upper or lower position with about 30 pounds of force, as will be understood by a person of ordinary skill in the art. This force could be increased by adding more weights e.g. more individual weights  68 , and by adjusting the height of the total counterweight height above a plane passing through the pivot  32 . 
     It should also be understood that the bridge  28  and more particularly the elevating conveyor and more particularly the elevating conveyor  34  is normally tilted a maximum of 22° when used with segmented belt convertor sections due to the limited drive force of the motors when moving a 70 lb pound load, and is limited to about 26° even with a one continuous belt conveyor. Practical installations consideration may limit the minimum tilt angle to 5° of 10° or 15° due to space consideration. 
     It is understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces all such modified forms thereof as come within the scope of the following claims.