Static structures (e.g. – buildings) – Machine or implement
Patent
1980-04-09
1984-01-31
Friedman, Carl D.
Static structures (e.g., buildings)
Machine or implement
212266, 414722, 228166, 228182, E04C 330
Patent
active
044281730
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
Technical Field
The invention relates to load carrying structures generally of a box-like structure and having preselected load input locations on said structures. More particularly, the invention relates to load carrying structures, such as, for example, the stick of an excavator, which encounter side, torsional, bending and columnar loading.
Background Art
In the use of load carrying structures, it is desirable to carry and distribute loads exerted on the structures to minimize failure of the structure elements. It is also desirable to minimize weight of the structure and to simplify fabrication and inspection as much as possible.
Load carrying structures have preselected load input locations through which various loads on the structure are exerted. In the stick of an excavator, for example, which is typical of such load carrying structures, the preselected load input locations represent the connecting points of the boom, bucket and hydraulic control cylinders to the stick. The stick thus acts as an intermediate link in the control operations of the bucket or other work elements of the excavator. The bucket of the excavator, for example, is often subjected to severe work applications which create high torsional and bending loads on the stick through the load input locations. It will be readily understood that such loads and the possible combinations thereof can cause early failure of a stick, particularly where the design of the stick creates highly localized loading. Thus, each portion, or step of manufacturing, of a load carrying structure is critical to its overall ability to effectively and efficiently carry the particular types of loads which will be encountered. In the excavator this is particularly important as the front load carrying structures need be as lightweight as possible for counterbalancing purposes.
Heretofore, typical stick design has included top and bottom plates and side plates which are fabricated, generally by welding, into a rectangular box-like arrangement. The load input locations, most commonly determined by pin joints with other parts of the excavator, are often defined by castings which provide an area of the structure having increased section properties in a relatively compact space. Such castings have generally been added to the ends of the box structure to define respective connections of the stick control cylinder and of the bucket and bucket linkage. A casting also is commonly added in the middle portion of the stick to define the boom mounting location. Also, the bucket control cylinder is connected to the stick at a tab or extended portion of the side plates adjacent the boom connection. Welding of the various elements of the stick one to the other has been by using weld back-ups which cover the back-up side of the weld and interfere with thorough inspection of the welds as a result.
Constructions of, and methods for, making load carrying structures are disclosed in the following patents. U.S. Pat. Nos. 4,159,796 which issued to Braithwaite on July 3, 1979, and 3,902,295 which issued to Yancey on Sept. 2, 1975, show details of booms used on excavators. U.S. Pat. Nos. 2,846,081 which issued on Aug. 5, 1958, to Moore and 2,257,386 which issued on Sept. 30, 1941, to Kempe disclose load carrying structures as are used on cranes or derricks. U.S. Pat. No. 1,960,557 which issued to Snyder on May 29, 1934, shows details of a pipe fitting for joining two sections of pipe.
In the use of the excavator, loading of the stick varies with the input location as related to the element of the excavator connected to the stick. Loads from the bucket onto the stick include side, torsional, axial and bending loads. For example, the bending loads result from digging or lifting with the bucket. The reaction to such loading forces are primarily taken by the stick at the boom-stick pin (load input) connection, as are the forces from side and torsional loading. The stick is also loaded as a column at its end opposite the bucket, along with stick control cylinder bending load
REFERENCES:
patent: 1960557 (1934-05-01), Snyder
patent: 2257386 (1941-09-01), Kempe
patent: 2846081 (1958-08-01), Moore
patent: 3722864 (1973-03-01), Borer et al.
patent: 3902295 (1975-09-01), Yancey
patent: 4034876 (1977-07-01), Yancey
patent: 4159796 (1979-07-01), Braithwaite
patent: 4161369 (1979-07-01), Moreno
patent: 4193734 (1980-03-01), Williams
patent: 4216895 (1980-08-01), Holmes
patent: 4293269 (1981-10-01), Zook
Caterpillar Tractor Co.
Friedman Carl D.
Heming William B.
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