Title:
Resilient link means for the apron of a self-loading scraper
United States Patent 3921314


Abstract:
A self-loading wheel-tractor scraper comprises a bowl connected to a draft tube of the tractor by a pair of draft arms. A pair of double-acting lift cylinders are pivotally interconnected between a draft tube of the tractor and a forward end of the bowl to selectively raise or lower the same during various phases of scraper operation. At least one resilient link is pivotally interconnected between the draft tube and an apron, pivotally mounted on a forward end of the scraper bowl, to alternately close or open the forward end of the bowl upon selective actuation of the cylinders.



Inventors:
FREESE GARY P
Application Number:
05/552382
Publication Date:
11/25/1975
Filing Date:
02/24/1975
Assignee:
CATERPILLAR TRACTOR CO.
Primary Class:
Other Classes:
37/417, 37/422
International Classes:
E02F3/64; (IPC1-7): E02F5/00
Field of Search:
37/126AB,126AA,126AD,126,129,8,126A
View Patent Images:



Primary Examiner:
Pellegrino, Stephen C.
Attorney, Agent or Firm:
Phillips, Moore, Weissenberger Lempio & Strabala
Claims:
I claim

1. In a scraper of the type comprising a tractor having a transversely disposed draft tube secured rearwardly thereon, a scraper bowl having an open forward end and a cutting edge secured forwardly thereon, a pair of draft arms pivotally interconnected between said draft tube and said scraper bowl, actuating means interconnected between said draft tube and said scraper bowl for selectively raising or lowering said scraper bowl and an apron pivotally mounted on a forward end of said bowl for movement between closed and opened positions on said bowl, the improvement comprising resilient link means operatively interconnected between said draft tube and said apron for automatically pivoting said apron between its opened and closed positions upon actuation of said actuating means and for maintaining a predetermined closing force on said apron when it is in its closed position on said bowl.

2. The scraper of claim 1 further comprising an elevator assembly mounted on a forward end of said bowl and having its lower end disposed adjacent to said cutting edge.

3. The scraper of claim 1 wherein said apron is pivotally mounted on said bowl to have a lower end thereof engage said cutting edge when said apron is in its closed position.

4. The scraper of claim 1 wherein said bowl comprises a pair of laterally spaced sidewalls and wherein said apron is pivotally mounted on a bracket secured on each of said sidewalls.

5. The scraper of claim 1 wherein said link means comprises first and second telescoped members pivotally attached to said apron and said draft tube, respectively.

6. The scraper of claim 5 wherein said link means further comprises first spring means normally compressed axially between said first and second members for urging said first member and said apron downwardly towards said bowl.

7. The scraper of claim 6 wherein said link means further comprises second spring means compressed axially between said first and second members for urging said first member and apron upwardly away from said bowl.

8. The scraper of claim 7 wherein each of said first and second spring means constitues a compression coil spring.

9. The scraper of claim 8 wherein said first member constitutes a rod and said second member constitutes a tubular housing having said rod telescopically mounted therein.

10. The scraper of claim 9 wherein said link means further comprises annular first and second piston members slidably mounted on said rod and spaced axially thereon, upper and lower ends of said first spring engaging and compressed between an upper closed end of said housing and said first piston member, respectively, and upper and lower ends of said second spring engaging and compressed between said first and second piston members, respectively.

Description:
BACKGROUND OF THE INVENTION

This invention relates to self-loading wheel-tractor scrapers of the type comprising a bowl having an elevator assembly mounted on a forward end thereof. Such a scraper is not normally provided with an apron pivotally mounted on an open forward end thereof. In particular, the lower end of the elevator assembly is positioned closely adjacent to a cutting edge secured on the bowl to thus aid in retaining material in the bowl. However, the loading and hauling of non-cohesive materials, such as sand, oftentimes results in a sifting of the sand through the elevator flights upon forward movement of the scraper.

Various closure structures have been proposed to overcome such problem, as exemplified by the type of structures disclosed in U.S. Pat. Nos. 3,170,254; 3,474,547 and 3,698,109. Also, it has been proposed to pivot an apron on a forward end of the bowl and to connect the apron to a draft tube of the tractor to automatically close or open the apron upon alternate lowering or raising of the bowl. However, material tends to be lodged between the apron and the cutting edge of the scraper during operation thereof to thus prevent complete closing of the open forward end of the bowl.

Summary of this Invention

An object of this invention is to overcome the above, briefly described problems by providing resilient link means operatively interconnected between an apron, pivotally mounted on a forward end of a scraper bowl, and a draft tube of a tractor. The link means maintains a predetermined closing force on the apron during the carry phase of scraper operation. Such link means preferably comprises at least one pair of telescopic members connected to the apron and draft tube, respectively, and spring means operatively connected between the two members for constantly applying the closing force on the apron upon its contact with a forward end of the scraper bowl.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects of this invention will become apparent from the following description and accompanying drawings wherein:

FIG. 1 is a side elevational view of a self-loading wheel-tractor scraper having the resilient link means of this invention pivotally interconnected between a closed apron and draft tube thereof;

FIG. 2 is an enlarged side elevational view more clearly showing the interconnection of the link means between the apron and draft tube and wherein the apron is shown in its opened position; and

FIG. 3 is an enlarged sectioned view of the resilient link means.

Detailed Description

FIG. 1 illustrates a self-loading wheel-tractor scraper 10 comprising a tractor 11 having a goose neck 12 extending rearwardly therefrom. A transversely disposed draft tube 13 is secured to the goose neck and has the forward ends of a pair of draft arms 14 (one shown) pivotally mounted on the ends thereof in a conventional manner. The rearward end of each draft arm is pivotally mounted on a respective sidewall 15 of a scraper bowl 16 by a standard trunnion assembly 17.

A conventional elevator assembly 18 is mounted on the bowl at a forward open end thereof. The elevator assembly essentially comprises a pair of laterally spaced endless chains 19 (one shown) having a plurality of longitudinally spaced and laterally extending flight members 20 secured therebetween. In such a conventional arrangement, each pair of adjacent flight members define an opening therebetween which permits egress of material therethrough at the lower, forward end of the bowl and adjacent to a standard cutting edge 21 thereof.

In order to prevent the same, an apron 22 is pivotally mounted on bowl 16 by a pair of pins 23 (one shown) each attached to a bracket 24 welded on a forward edge of each sidewall 15 of the bowl (FIG. 2). A pair of laterally spaced extensible and contractible resilient link means 25 (one shown) are each pivotally interconnected between the apron and draft tube 13 by pivot pins 26 and 27, respectively. Such link means function to open the apron automatically upon lowering of the bowl by a pair of conventional double-acting hydraulic cylinders 28 (one shown) each pivotally interconnected between a forward end of the scraper bowl and the draft tube by a pair of pivot pins 29 and 30, respectively.

Referring to FIG. 3, link means 25 comprises a rod member 31 telescopically received wtihin a housing member 32. A cup-shaped upper piston member 33 is slidably mounted on a reduced upper end of rod member 31. The upper piston member is retained thereon by a washer 34 and a cap screw 35 and engages a lower end of a first spring means 36, preferably a compression coil spring, having its upper end abutting a closed end of housing 32. The upper piston member further engages an upper end of a second spring means 37, also preferably in the form of a compression coil spring. A cup-shaped lower piston member 38 engages a lower end of spring 37 and a shoulder on rod 31. Both springs 36 and 37, both pistons 33 and 38, and rod 31 are retained in housing 32 by an annular plate 39 suitably secured to ring member 40, and thus housing 32, by a plurality of cap screws 41. Upon assembly of link means 25, springs 36 and 37 do not require compression but their function would not be restricted should they be preloaded.

Referring once again to FIG. 1, apron 22 must be maintained in its closed position or cutting edge 21 during forward travel of the loaded scraper to prevent spillage of the loaded material. If rocks or other hard substances should pile up between the cutting edge and the apron as it is being closed, such rocks might prevent the apron from closing completely against the cutting edge. However, resilient link means 25 will automatically exert a downward force on the apron and force it closed against the cutting edge.

The prior art includes aprons that are hydraulically powered and aprons with positive closing linkages. Hydraulic powered aprons are expensive as they require hydraulic circuitry and positive linkages must be adjusted so that apron lip just touches cutting edge at the full raise position of the bowl. If the positive linkage is not adjusted properly or if a foreign object gets lodged between the apron lip and cutting edge, high forces could occur in the linkage. In contrast thereto, the resilient linkage of the present invention allows an economical downforce at the apron lip and provides for a limited amount of variation between cutting edge and apron lip.

When the apron is opened automatically to its FIG. 2 position by link means 25, upon retraction of cylinders 28, the dead weight of the apron will be supported on draft tube 13 by spring 37 and housing 32 (FIG. 3). Thus spring 37 will be further compressed and will function to hold the apron in its open position with sufficient resiliency to prevent damage thereto by vibrations generated in the scraper during operation thereof.

When the apron is closed by raising the bowl, both springs 36 and 37 are compressed equally since piston member 33 is slidably mounted on rod 31. This provides a predetermined load between the cutting edge and apron lip. A foreign object that will not be crushed by apron down force will increase the normal down force by compressing springs 36 and 37 even more. The link will absorb the forces imposed thereon by a foreign object size until rod 31 bottoms-out on top of housing 32. When rod bottoms-out on upper part of housing 32, the linkage becomes positive and high loads can occur. The distance between the two slidable pistons 33 and 38 also give the fully extended link buckling stability.