Abstract:
A chain tension maintenance device for use with the bowl loading elevator of the excavating scraper variety which is adjustable to vary the slack in the chain and paddle structure. At least one idler arm having bell crank geometry is pivotally mounted to the elevator frame through a first pivot point. An idler wheel axially mounted at a second pivot point of the idler arm, is urged into tension maintaining contact with the elevator chains by force exerted through the third pivot point of the idler arm by an adjustable turnbuckle grounded to the elevator frame.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     A chain tension maintenance means is provided to maintain the tension of the paddle and chain structure of an elevator as used on an elevating scraper. 
     2. Description of the Prior Art 
     An optional device on earth moving scrapers is an elevator that assists in loading the bowl or load carrying portion of an earth moving scraper. The elevator is usually comprised of a pair of substantial chains driven by sprocketed axles. A series of paddles are carried by the chain pair transversely thereto to make a unified structure for loading the scraper. 
     Elevator chains of elevating scrapers tend to stretch and wear under normal operation. Currently only complicated and time consuming adjustment means are available. Typical adjustment procedure would require the use of hydraulic cylinders intergral with the elevator frame to maintain tension. Alternative procedures may require hydraulic jacks to tension the chain while idler sprocket bolted connections are repositioned. As the chains on each side of the elevator may wear or stretch at different rates it is occasionally necessary to remove or add links to allow the range of a tensioning idler to accommodate the chain. Most contempory procedures can be improved upon through cost reduction, decreased complexity or ease of adjustment. 
     SUMMARY OF THE INVENTION 
     A chain tensioner is provided for use in tensioning the chains of the elevator train of an elevating scraper. A pivotally mounted idler arm having bell crank geometry is carried on each side of the elevator frame. An idler wheel is axially mounted to one pivotal location of the idler arm such that it may be in its sprocketed relationship with each elevator chain. A turnbuckle is pivotally mounted or grounded to the elevator frame at one end thereof and pivotally mounted to a third pivotal location on the idler arm. Turnbuckle adjustment decreasing the length of the turnbuckle results in an increased angular relationship between the elevator frame and the idler wheel effectively moving the idler wheel away from the elevator frame and thus increasing the chain tension. An adjusting lug is provided on the turnbuckle and further accommodates an adjusting pin which serves as a turnbuckle lock when proper tensioning exists in the chain and as an adjusting tool to operate the turnbuckle to increase or decrease chain tension. 
     Alternative structures using the same principles of operation are also disclosed. A first of these structures embodies a single turnbuckle and an elongated single idler arm having a pair of idler wheels one located at each end of the elongated idler arm. One idler wheel maintains tension on the chain through its position on chain contact relatively above the elevator frame while the other idler wheel maintains tension on the chain relatively below the elevator frame. 
     A third embodiment incorporates a fixed center point turnbuckle positioned between a pair of idler arms of identical geometry which will position attendant idler wheels against the elevator chain on the same relative sides of the elevator frame. Turnbuckle adjustment in this configuration results in simultaneous and equal adjustment of each idler arm upon adjustment of the fixed center turnbuckle. 
     The primary object of this invention is to provide a simplified, efficient, low cost means of adjustment. This is accomplished through the use of the turnbuckle as provided with the adjusting pin carried on the turnbuckle. No extraneous adjustment tools are needed. 
     It is further an object to provide a chain adjusting device allowing infinite adjustment increments for each of the pair of chains in an elevator. 
     Another object of this invention is to provide an adjusting device that will maintain a preset adjustment when subject to continuous vibration or jostling. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The environment of the instant invention as well as several embodiments thereof are presented by the drawing figures in which: 
     FIG. 1 presents an elevation view of a construction scraper that would accommodate the invention; 
     FIG. 2 is a side view of an elevator chain tensioner having a single tensioning arm with a pair of chain sprockets; 
     FIG. 3 is a side view of an elevator chain tensioner having a single tension arm and sprocket; and 
     FIG. 4 is a side view of an elevator chain tensioner having a pair of tension arms and sprockets. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is fully shown in the accompanying drawings wherein FIG. 1 presents the environment typical for the application of an elevator chain tensioner. In FIG. 1 an elevating scraper generally 10 includes a forward drive section 12 accommodating an operator&#39;s compartment 14 and supported on driven axle and wheel assembly 16. The forward drive section is a conventional apparatus of a scraper and generally includes an engine and drive train (not specifically shown). Pivotally attached at articulation point 20 to the forward drive section is a trailing rear section generally 22. In the scraper shown this rear section 22 is equipped with a rear drive engine 24 and drive train to drive the rear wheel and axle assembly 26, however, it is also common to manufacture elevating scrapers without rear engines. 
     The conventional functional parts of the scraper include the bowl 30, the cutting edge 32, the side cutter blades 34, the bowl cylinders, one shown as 36, the elevator generally 40 which is the specific apparatus of importance to this invention, and an ejector 42 which may slide forward in the bowl 30 to assist in unloading the bowl. 
     In operation the scraper is driven over a path to be excavated with the cutting edge 32 lowered below the ground surface. As the excavated material builds up on the apron or floor of the bowl 30 the elevator 40 will be driven in a counterclockwise direction to load material into the bowl. When the bowl is full the operator elevates the cutting edge 32 and the bowl 30 to prevent further loading. This process is conventional. 
     The remaining figures show three embodiments of elevators equipped with variations of this invention. In each of these figures like numbers represent like parts and distinctively different components are assigned unique reference numbers. 
     In FIG. 2 an elevator is shown separated from the scraper vehicle. The elevator is built around an elevator frame 44 which is a rectangular frame having a pair of longitudinal side frame members one shown as 46, and a plurality of transverse cross members which are not shown. A driven axle 50 or a driven cross support tube and a lower shaft or undriven axle 52 are carried at the ends and between the side frame members 46 transversely thereto. Each axle includes a pair of sprockets, specifically shown are a driven sprocket 54 and a lower sprocket 56. The lower sprocket could alternatively be a untoothed chain guide. 
     An endless elevator chain 60 composed of links 62 is simultaneously engaged by the driven 54 and lower 56 sprockets. A typical elevator will have a pair of endless chains between each set of driven and lower sprockets. A plurality of paddles such as 64 are provided transversely between the paired endless chains thus combining each of the two endless chains into a unitary device. 
     The chain tensioner of the FIG. 2 embodiment includes a double idler arm 66 which is pivotally mounted to a bracket 70 through pivot pin 72. The double idler arm is based on a quadralateral plate with a plurality of apertures for use as pivot points for supporting related axles. Each double idler arm 66 carries a pair of idler wheels, an upper 74 and a lower 76 pivotally mounted on axles 80 and 82 respectively. The idler wheels of all the embodiments present herein may have sprocket teeth if desirable or may be untoothed. The idler wheels are located by the placement of the double idler arm to engage the endless chain 60. The idler wheels are located in the same plane as the driven and undriven sprockets in order to assure good alignment with the chains. Turnbuckle 80 is pivotally attached at a first end 82 thereof to a pivot point 84 turnbuckle attachment means on the double idler arm 66. A second end 92 of the turnbuckle is pivotally mounted to a turnbuckle anchor or support 94 which is integral with the side frame members 44. The turnbuckle is relatively conventional with an elongated central body having a threaded longitudinal bore with right and left hand threads. Threaded eyebolts are accommodated by the central body in a conventional manner. A handle 86 is provided on the elongated central body of the turnbuckle to serve the dual purpose of acting as a adjusting wrench and preventing undesirable adjustment of the turnbuckle through vibration. A locking mechanism 90 is provided on the body of the turnbuckle. 
     As shown in FIG. 2 the chain adjuster is movable from a dotted line position A, which represents a virtually non-tension inducing displacement, to the solid line position B which represents a substantially adjusted position. When in position A stop 96 prevents further clockwise rotational adjustment of the double idler arm. 
     Adjustment, typically to increase chain tension, is facilitated by removing the handle 86 from its retaining means on the turnbuckle and using it as a wrench to turn the turnbuckle. As is apparent the decrease in the overall length of the turnbuckle facilitated by the threaded parts thereof being fed into the turnbuckle pivots the double idler arm 66 around point 72 thus urging each double idler arm outwardly against the chain as shown by the solid line displacement B of FIG. 2. Similar adjustment will be made to the idler arm assembly on the other side of the elevator in order to insure that both chains are equally tensioned. After adjustments the handle 86 is replaced in its retaining means on the turnbuckle so it will be available for future adjustments. 
     FIG. 3 presents an alternative embodiment of the elevator chain tensioner. Basic elements of the frame are as described in FIG. 2 with the differences being in the tensioning apparatus itself. 
     A bracket 96 is attached to the side frame members 46 to which idler arm 100 is pivotally attached by pivot pin 102. The idler arm is of a generally triangular shape having an aperture at each corner thereof to affect a bell crank type geometry when connected to the frame, turnbuckle and idler wheel. This geometry is dependent on the placement of the apertures. As can be seen in FIG. 3 the distance between the first and second apertures is less than the distance between the second and third apertures. The idler arm 100 carries idler wheel 104 on axle 106 which is engageable with the endless chain 60 as shown. 
     The idler arm 100 is maintained in a tensioning position against the endless chain 60 by the bell crank geometry presented by the location of the pivotal means 110 which allows a turnbuckle 112 similar to that earlier to be attached thereto and to hold the idler arm 100 in position. 
     The second end of the turnbuckle is pivotally mounted to the support 114. The turnbuckle is provided with at least one adjusting lug 116 which is equipped with an aperture therethrough to accommodate a pin 120 that also passes into a pin chuck 122 having an elongated slot that can receive the pin 120 regardless of the elongation of the turnbuckle. The pin 120 is a rod having a bent end portion perpendicular to the major axis of the rod. A retaining means 124 may also be provided to prevent pin 120 from being jostled out of the pin chuck 122. The retaining means may be associated with an aperture in the end of the pin. The pin 120 may be removed from the pin chuck 122 and used as a lever or tool to adjust the turnbuckle as this becomes necessary. 
     Adjustment to increase chain tension entails removing the pin 120 from its retained position and utilizing it as a tool to turn the turnbuckle. The pin 120 would be engaged with the adjusting lug 116 to provide necessary leverage to turn the turnbuckle. Adjustment decreasing the overall length of the turnbuckle results in increased tension on the chain. Adjustment of both tensioners (one on each side of the elevator frame may be desirable in order to maintain even tension throughout the elevator.) Obviously lengthening the turnbuckle results in decreased chain tension. 
     A third embodiment is shown by FIG. 4 which uses the principles taught by this disclosure through the use of a pair of idler arms. The pair of idler arms are shown as first twin idler arm 126 and second twin idler arm 130. The first twin idler arm is pivotally mounted at first pivot point 132 to a first apertured tab 134 which is integral with the side frame member 46. The second twin idler arm 130 is pivotally mounted at second pivot point 136 to a second apertured tab 140 also integral with the side frame member 46. Each twin idler arm is equipped with a pivot point 142 and 144 respectively, to accommodate the attaching ends 146 and 150 of the twin turnbuckle 152. Each twin idler arm carries a twin idler wheel 154 and 156 on axles 160 and 162 respectively as is apparent from the drawing figure. The relative triangular shape of these idler arms is apparent from FIG. 4. 
     The twin turnbuckle 152 used in this embodiment is similar to the turnbuckle 112 of FIG. 3, and has features of the turnbuckles previously described, with the addition of first 164 and second 166 washers welded to the body of the twin turnbuckle to provide locating flanges. A turnbuckle guide 170 having an aperture to accommodate the twin turnbuckle is welded or otherwise affixed to each side frame member 46 through which the twin turnbuckle passes. The washers or locating flanges 164 and 166 prevent significant lateral movement of the twin turnbuckle as they will not pass through the aperture of the guide 170. 
     The pin 120, adjusting lug 116, pin chuck 122 and retaining means 124 are similar to items shown in FIG. 3. 
     Adjustment of this chain tensioning device is exactly as described for the adjustment of the FIG. 3 embodiment as is apparent. 
     Thus it is apparent that there has been provided, in accordance with the invention, a chain tensioner that fully satisfies the objects set forth above. While the invention has been described in conjunction with three specific embodiments, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, this disclosure is intended to embrace all such alternatives, modifications and variations as fall within the scope of the appended claims.