Abstract:
A movable backup bar assembly includes an endless drive chain, a sprocket or the like for coupling the drive chain to the power source, and a backup bar for guiding the drive chain. The assembly has two positions: a first position for holding the drive chain in engagement with the chain to be driven and a second position for holding the drive chain away from the driven chain. An actuator is provided for positively shifting the assembly between these two positions.

Description:
This application claims the benefit of U.S. provisional patent application 60/051,336, filed on Jun. 30, 1997. 
     The present invention is directed toward a backup bar assembly for guiding and positioning a drive chain, and, more specifically, toward a movable backup bar assembly that can be quickly and easily shifted from a first position for holding a drive chain against an object to be driven, and a second position for disengaging the drive chain from the object. 
    
    
     BACKGROUND OF THE INVENTION 
     Drive chains are used to transfer power from a source of rotational energy to a secondary chain or similar device such as the power chain in a power and free conveyor system. The drive chain is connected between two sprockets, at least one of which is powered by a drive shaft, and includes a plurality of teeth or dogs extending outwardly from the chain for engaging the driven chain. The drive chain is positioned in proximity to the driven chain, and a backup bar is used to guide the drive chain and hold it against the driven chain. This allows the teeth on the drive chain to engage the secondary chain and transmit the rotation of the drive chain to the driven chain. 
     A backup bar must be carefully positioned in order to transfer power from the drive chain to the driven chain in an efficient manner. If the bar does not hold the drive chain sufficiently firmly against the conveyor chain, the teeth may slip, resulting in a lower or inconsistent level of power. If the drive chain is pressed too firmly against the conveyor chain, it may interfere with the smooth rotation of the drive shaft. If the drive chain is not properly aligned with the chain being driven, damage may result to one or both of the chains, shortening the lives thereof. Furthermore, significant stresses are placed on the backup bar by the drive chain during operation which could alter the orientation of the backup bar if it were not securely fastened in place. Therefore, drive chain assemblies are constructed with backup bars bolted in place to hold the drive chain precisely in position. 
     It occasionally becomes necessary to disengage the drive chain from the conveyor chain such as when performing certain maintenance tasks or when auxiliary drives are connected to the conveyor. In order to do this, it is necessary to unbolt the backup bar and remove it, or reposition it so that it no longer holds the drive chain against the conveyor chain and refasten the backup bar in this new position. Because the unbolting of the backup bar can introduce slack into the drive chain, the person performing this operation must be careful to ensure that the drive chain is completely clear of the conveyor chain and not drooping onto the conveyor or onto any other moving parts. It may also be necessary to secure the drive chain to keep it clear of the conveyor chain. Care must be taken not to operate the drive chain when slack is present because this could cause the drive chain to slip off of the drive sprockets and cause damage to nearby equipment such as the drive shaft. This repositioning process requires a variety of tools and special skills and can take approximately 15 minutes, even when performed by a skilled technician or engineer. It would therefore be desirable to provide a backup bar assembly that could be repositioned quickly to positively engage or disengage a drive chain from a conveyor chain and which could be operated without special tools or skills, yet which was still capable of securely holding a backup bar in a required position. 
     SUMMARY OF THE INVENTION 
     These and other objects are accomplished by the present invention which comprises a backup bar assembly for use in connection with a drive chain which assembly can be repositioned with an actuator operable either automatically or by hand. The actuator is preferably lockable in only one of two positions to ensure that the backup bar is either positively holding the drive chain against the conveyor chain or is separated from the drive chain, and that it is not in some intermediate position. Furthermore, the backup bar assembly may include a structure for placing tension on the drive chain to hold it away from the driven chain even when the drive chain is disengaged from the driven chain. 
     In a preferred embodiment of the subject invention, the drive chain assembly comprises first and second sprockets, each supported by a rotatable shaft for rotation about the longitudinal axis of the shaft. At least one of the shafts is a drive shaft connected to a power source. An endless drive chain is connected between the sprockets and rotates about the sprockets when the drive shaft turns. A backup bar is attached to a backup bar support and the backup bar support is connected to an actuator which in turn is connected to a structure that is fixed with respect to the sprockets. The backup bar is positioned inside the curve defined by the endless drive chain and in alignment with the drive chain. The actuator can be manipulated by hand to move the backup bar against the drive chain to push the drive chain into engagement with the chain being driven and then locked in place to hold the drive chain against the driven chain. The actuator can also be locked in a second position to hold the backup bar away from the drive chain. 
     Preferably, when the actuator is in this second position, the backup bar support places tension on the drive chain to hold it away from the chain being driven. The drive chain may still be turning when it is disengaged from the driven chain. Therefore, it is important that it be held away from the driven chain so that the driven chain will not change position when it is supposed to be at rest. Likewise, the driven chain may continue to be driven by an auxiliary drive after the main drive chain is disengaged. It is therefore important that the drive chain be held clear of the driven chain to prevent it from interfering with the free movement thereof. 
     It is therefore the principal object of the present invention to provide an apparatus for moving a drive chain into and out of engagement with another object. 
     It is another object of the present invention to provide an apparatus of the forgoing character which can be operated without the use of tools. 
     It is a further object of the present invention to provide an apparatus of the forgoing character which can be operated by a person without any special skills. 
     It is yet another object of the present invention to provide an apparatus for reducing slack in a drive chain when it is disengaged from a driven chain. 
     It is still another object of the present invention to provide an apparatus of the forgoing character that is lockable in a first or second position to positively hold a drive chain against or away from a driven chain. 
     It is yet another object of the present invention to provide an actuator for a backup bar. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other object of the invention will become apparent from a reading and understanding of the following detailed description of the preferred embodiment of the invention together with the following drawings of which: 
     FIG. 1 is a front elevational view of a drive chain and a movable backup bar assembly according to the present invention with the backup bar shown in the down position; 
     FIG. 2 is a front elevational view of the drive chain and movable backup bar assembly of FIG. 1 with the backup bar shown in the up position; 
     FIG. 3 is a side elevational view of the backup bar assembly of FIG. 1; 
     FIG. 4 is a bottom plan view of the backup bar assembly of FIG. 1; and, 
     FIG. 5 is a top plan view of the backup bar assembly of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, wherein the showings are for the purposes of illustrating a preferred embodiment of the subject invention only, and not for purposes of limiting same, FIG. 1 shows a backup bar assembly designated generally by the numeral  10  comprising a backup bar support  12  having a top wall  14 , a front wall  16  and a rear wall  18 , two legs  20  extending away from top wall  14  and having bottom walls  22 , and an inner wall  24  located between the leg bottom walls. A bore  26 , connects top wall  14  with inner wall  24  and is located closer to rear  18  than to front wall  16 . A backup bar  28  is attached to bottom walls  22  of support  12  and closer to front wall  16  than to rear wall  18  such as by welding or bolting, and the backup bar is preferably made from aluminum or steel or any of the other materials from which ordinary backup bars are normally constructed. Backup bar  28  comprises a length of a generally C-shaped channel section comprising a channel bottom  30  and channel sides  32 , and the channel sides are flared at end portions  34  to help guide a moving chain through the channel. If bolts are used to hold backup bar  28  to support  12 , the bolt heads should be counter-set below channel bottom  30  so as not to interfere with the movement of a chain across the channel bottom. Support  12  includes a channel  36  in top wall  14  located near front wall  16  and directly above and aligned with backup bar  28 . A channel insert  38 , made from the same material as the backup bar is fitted within channel  36 , although this insert  38  may be omitted if support  12  is itself made from the same material as the backup bar. Insert  38  has flared end portions  40  which fit within flared end portions  42  of channel  36 . 
     Backup bar  28  is supported by an actuator  44  which includes a fixed cylindrical housing  46  connected to a stationary structure  48  by brackets  50 , and a movable rod portion  52  supported within housing  46  for coaxial movement with respect thereto. Actuator  44  further includes a handle  54  which is used to move rod  52  with respect to housing  46 . Handle  54  is lockable in first and second positions for securely holding rod  52  in a given position, even when stresses are applied to the rod. A suitable actuator is a push/pull clamp sold by the Carr Lane Manufacturing Company of St. Louis Mo. as model number CL-300-PC. While this clamp can be locked in a given position, preferably it is modified by drilling two holes  58  and  60  into stationary structure  46  and a third hole  62  through handle  54  so that a pin  64  can be inserted through opening  62  and one of openings  58 ,  60  to hold handle  54  and hence rod  52 , in a specific position with respect to the housing. 
     Stationary structure  48  is the housing of a motor for driving a drive chain. Two shafts  66  extend from openings in housing  48  and at least one of the shafts is connected to a drive for rotating the shaft. A pair of sprockets  68  are supported on the shafts and a drive chain  70  is supported by the sprockets. Chain  70  includes a number of dogs  72  extending away from the sprockets and the chain is long enough so that slack remains in it when it is supported only by sprockets  68 . A driven chain  74  is located adjacent drive chain  70  close enough so that drive chain  70  can biased against driven chain  74  by removing the slack from the drive chain. When drive chain  70  is held against driven chain  74  with dogs  72  in engagement with the driven chain  74 , the rotation of the drive chain will be transmitted to the driven chain causing it to rotate as well. 
     Rod  52  passes through bore  26  and is secured with respect to support  12  with bolts  76  or in any other suitable manner such as by the use of pins or by welding. Actuator  44  is positioned so that backup bar  28  is aligned with the part of the drive chain adjacent driven chain  74 . This portion is the lower portion of the drive chain as seen in the figures and will be referred to as the lower portion of the chain herein, it being understood that the drive chain could be oriented differently so that this portion of the drive chain would no longer be the lower portion. When backup bar  28  is in its lowered position as shown in FIG. 1, drive chain  70  is received within backup bar  28  and held in engagement with driven chain  74  so that the rotation of the drive chain will be transmitted to the driven chain. When actuator  44  is moved to the second position, shown in FIG. 2, backup bar  28  is pulled away from the driven chain and the drive chain ceases to drive the driven chain, even if the drive chain continues to rotate. In this second position, the top portion of drive chain  70  is supported by channel  36  in top wall  14  of support  12  to hold drive chain  70  taut and to keep the drive chain from drooping into contact with the driven chain which might still be moving, such as when an auxiliary drive is present in the conveyor line. Actuator  44  is freely movable between these two positions, and thus the backup bar assembly can be shifted to engage or disengage a drive chain from a driven chain in a matter of seconds, and without the use of any tools. In addition to being easier to use, it is also significantly easier to manufacture, reducing manufacturing time by approximately 25%. 
     The subject invention has been described with respect to a preferred embodiment in which the backup bar assembly is used to move a drive chain into and out of engagement with a conveyor chain. It should be understood, however, that the invention has broader applications and could be used any time it is necessary to hold a driving belt or chain against another object. It can also be used with a variety of different drive systems without extensive modification. These and other obvious modifications will become apparent to those skilled in the are upon a reading and understanding of this specification and such modifications are included within the scope of this invention to the extent they are defined by the claims appended hereto.