Dirt scrapers are mechanical devices used in dirt removal and land leveling operations. Dirt scrapers with large buckets for collecting scraped dirt include a cutting edge on the front of the bucket, hydraulic means for elevating and rotating the bucket when filled with dirt for transporting the dirt to another location and hydraulic means for tilting the bucket to empty the dirt contents and thereafter leveling the dirt.
A condition identified as "bounce" has long been a problem in dirt scraping operations, particularly when loading dirt scrapers, transporting the dirt scrapers with filled buckets of dirt, dumping the contents from the buckets and returning the empty scrapers to the original site. The term "bounce" includes the tendency of the cutting edge of the bucket to dig too deep or too shallow when collecting and removing a slice of dirt from the area being worked. Bounce also includes the concept of excessive vibration of the bucket during filling and transportation. Also, bounce may occur when one portion of the bucket cutting edge reaches the material being collected slightly ahead of the other edge portions of the bucket producing a horizontal bouncing effect from the bucket jumping back and forth from one side to the other in a somewhat uncontrollable manner. This bouncing effect presently can be corrected only when the pulling vehicle is slowed down to a crawl or after sufficient dirt is accumulated in the bucket to hold it down. Also, the bounce problem is compounded when the empty dirt scraper is returned for another leveling operation and has to go over the rough ground created by the uneven slices from previous loadings. The bounce problem is compounded and multiplied by the number of dirt scraping rigs utilized on a particular leveling job.
It has been previously proposed to mount solid skid shoes on the lower forward portion of the bucket near the cutting edge of the bucket. This reduced bucket bounce but did not eliminate the problem. Also, skid shoes have been mounted external of the bucket by attaching them to the front frame section of the dirt scraper. Skid shoes have even been attached to the towing tongue of the dirt scraper. Some skid shoes have been adjustable by means of bolts and it is also known to adjust the pitch of skid shoes by means of hydraulic assist.
U.S. Pat. No. 5,058,294 discloses a mobile excavating system having a continuous bucket series mounted at the leading end of a structural mainframe which includes a mold board/skid plate assembly which may be raised or lowered to hold at or near a particular grade elevation desired. The skid plate is used as a stabilizer for the digging wheel and the mold board blade. The skid plate is positioned against the mold board blade cutting edge and is held in position by means of compression springs and hydraulic damping cylinders. Such an arrangement is complicated, does not work effectively and is replaced only with great difficulty
U.S. Pat No. 4,389,800 discloses land leveling scrapers having skid shoes whose bottom surfaces are free to accommodate and follow irregularities in the ground surface being leveled. The skid shoes are urged against the ground surface with a force proportional to the load on the bucket or the scraper by means of a complicated mechanical arrangement. Again, it must be noted that such arrangement would be difficult to install and maintain.
The problems associated with known prior devices are overcome by the present invention which is characterized by a damping device comprised of a spring loaded skid shoe with protected, easily replaceable parts.