JPH0581693B2 - - Google Patents

Description

Claim 1 The load supporting structure 10 includes first and second side edge portions 50, 52, 54, 5.
6 and the first and second end portions 38, 46, 40, 4
an upper plate 22 and a lower plate 24 each having a first plate portion 158, 162 and a first plate portion 158, 162 coupled in series with the first plate portion 158, 162 and having a lower plate portion 8; Thinner second
The upper plate 2 consists of plate portions 160 and 164.
2 and the lower plate 24 respectively to form a box-shaped shape. first and second side plates 30, 32, the first plate portions 158, 162 extending outwardly from the first end portions 38, 40 of the upper plate 22 and lower plate 24, respectively; the first plate portion 15 of the first and second side plates 30,32.
8,162, the second load input location 72
is on the second plate portion 160,164 of the first and second side plates 30,32, and the third load input location 74 is on the first plate portion 158,162 of the first and second side plates 30,32. said outwardly extending portion 7 of
30, 32 as defined above 8, 80 and U from the first end portion 34 to the second end portion 36.
The first and second ends of the upper plate 22 and the lower plate 24 are made of an integrally cast body extending in the shape of a letter, and have a bottomed box shape as a whole. a first plate of said first and second side plates 30, 32 at first and second side edge portions 58, 60 defining opposite edges of the U-shaped elongated casting; a first support member 26 welded to portions 158, 162, respectively, of the first plate portion 1 of said first and second side plates 30, 32;
a through hole 122 extending from the first side edge portion 58 to the second side edge portion 60 in alignment with the first load input location 70 defined on the first side edge portion 58,162;
at the base of the "U"; and from the first end portion 42 to the second end portion 44 the U
The second part of the upper plate 22 and the lower plate 24 is made of a monolithic casting extending in the shape of a letter, and has a bottomed box shape as a whole. a second plate of said first and second side plates 30, 32 at first and second side edge portions 62, 64 defining opposite edges of the U-shaped elongated casting; a second support member 28 welded to portions 160 and 164, respectively;
the first side edge portion 6 in alignment with the second load input location 72 defined on the second plate portions 160, 164 of the first and second side plates 30, 32;
2 to the second side edge portion 64
34 at the base of the "U"; and 28.

2. The first and second support members 26, 28 are
Double horizontal butt welds 106, 108, 110, 1
2. A load-bearing structure according to claim 1, wherein said load-bearing structure is connected to said upper and lower plates 22, 24 by 12.

3. Each of the first and second side plates 30, 32 has an inner surface 113, 115, and the inner surface 11
3,115, said first side edge portion 50,5
4 and the second side edge portions 52, 56, respectively, and the first and second side plates 30,
32 is the abutting inner surface 113, 115
and the first and second side edge portions 50, 54, 5
Welds 114, 116, 11 along 2, 56
8,119 said upper plate and lower plate 22,24
A load-bearing structure according to claim 1, wherein the load-bearing structure is coupled to.

4 The welded portions 114, 116, 118, 119
4. A load-bearing structure according to claim 3, wherein is a single lateral butt weld.

5 the first and second plate portions 158, 160,
162, 164 each have an edge 166, 168, 1
70,172 and associated said first and second
The end edges 166, 168, 170, 172 of the plate portions 158, 160, 162, 164 are arranged to abut each other and are connected to each other by welds 174, 176 at this abutment location. A structure that supports the load described in Section 1.

6. Each of the first and second side plates 30, 32 has a first and second hole 120, 130, 121, 13.
2, said first load input location 70 defining a first hole 120, 121 in said first and second side plates 30, 32, respectively. and a portion of the first support member 26 defining the hole 122 of the first support member 26;
The load input locations 72 are located in the associated second holes 130, 13 of said first and second side plates 30, 32.
the first and second side plates 30, 32 defining
and the hole 13 of the second support member 28
4. A load-bearing structure according to claim 1, wherein said second support member (28) defines a portion of said second support member (28).

7. The outwardly protruding portions 78, 80 of the first and second side plates 30, 32 are connected to the first holes 139, 1, respectively.
40 and said third load input location 74
are the respective first portions of the outwardly projecting portions 78 and 80.
said first and second holes defining holes 139, 140 of
A load-bearing structure according to claim 1 defined by portions of side plates 30, 32 of.

TECHNICAL FIELD This invention relates to a load bearing structure consisting of a generally box-shaped structure having a plurality of predetermined load input locations. More particularly, the invention relates to load bearing structures, such as excavator stakes, which are subjected to lateral, torsional, bending and column loads.

BACKGROUND OF THE INVENTION In the use of load-bearing structures, it is desirable to support and distribute the loads applied to the structure in order to minimize failure of the structural elements. It is also desirable to minimize the weight of the structure and to simplify fabrication and inspection as much as possible.

A load-bearing structure has several predetermined load input locations through which various loads on the structure are exerted.

For example, in an excavator stake, which is typical of such load-bearing structures, the predetermined load input location is the attachment point of the boom, bucket, and hydraulic control cylinder to the stake. The stake serves as an intermediate link in the control operation of the bucket or other work elements of the excavator. For example, excavator buckets are used in demanding operations that create large torsional and bending loads on the stakes through the load input locations. Such loads and their possible combinations are:
It will be readily appreciated that premature failure of the stake can occur, particularly where the configuration of the stake produces highly localized loads. Therefore, each part of a load-bearing structure, or each process of manufacture, is critical to its overall ability to effectively and efficiently carry the particular type of load to which it may be subjected. . In excavators, the front load-bearing structure is
This is particularly important since it needs to be as light as possible for balancing purposes.

In the past, a typical stake configuration includes top and bottom plates and side plates that are assembled into a rectangular box-like device, typically by welding. Typically, the load input location is often determined by pin connections to other parts of the excavator.
Often defined by a molding providing an area of structure with increased sectional properties in a relatively compact space. Such castings are commonly added to the ends of the box-like structure to define the respective connections of the stake control cylinders and the respective connections of the buckets and bucket connections. Castings are also typically attached to the central portion of the stay to define the boom attachment location. The bucket control cylinder is also coupled to the stake at an ear or protrusion in the side plate adjacent the boom coupling. Welding between the various elements of the stake is accomplished by using a weld backing which covers the backing side of the weld and, as a result, prevents adequate inspection of the weld.

The construction of load bearing structures and methods of making them are disclosed in the following patents. U.S. patent granted for brace weight on July 3, 1979
No. 4,159,796 and U.S. Pat. No. 3,902,295, issued to Yancey on September 2, 1975, show details of a boom used in an excavator. U.S. Patent No. 2,846,081, issued to Moore on August 5, 1958, and U.S. Patent No. 2,257,386, granted to Kemp on September 30, 1941,
A load supporting structure for use in a crane or derrick is disclosed. U.S. Patent No. 1960557, granted to Snyder on May 29, 1934, covers two tubes.
The figure shows details of a pipe fitting for connecting individual parts.

During use of the excavator, the load on the stake varies according to the input location relative to the elements connected to the stake of the excavator.
The loads exerted by the bucket on the stake include lateral torsional loads, axial loads and bending loads. For example, bending loads result from excavation or lifting by buckets. Reactions to such loading forces are absorbed by the stake primarily at the boom-stay pin (load input) connection. The same applies to forces from lateral and torsional loads. Staitsku is also
At the end opposite the bucket end, a column load is applied along with a stake control cylinder bending load. The bucket tortoise cylinder similarly exerts a bending load on the stake. In addition, significant rolling and lateral loads are further created on the stake during excavation, depending on the various conditions of stake operation, such as corner loading and side loading of the bucket.

The complex loading described above can quickly create local loading conditions on the stake, which can cause failure at weak points in the design. The location and interconnection of the elements of a load-bearing structure are therefore of great importance to the satisfactory support of loads or reaction forces in the stakes. For example, the adjacency of the side panels and castings should be uniform and properly located in the structure to substantially eliminate cross-sectional discontinuities that tend to create highly localized stresses. It takes. It is also desirable to combine the elements adjacently so that uniform weld grooves and constant weld cross sections can be easily and consistently formed. Therefore, in this context, both sides of the weld should be visible to eliminate hidden welds and to facilitate visual and ultrasonic inspection throughout the assembly process.

Therefore, it is desirable to design and construct load-bearing structures, such as excavator stakes, to optimize the location and coupling of elements to support the loads exerted on particular portions of the stake. . It is also important to simplify assembly and testing to ensure proper construction and operability based on design parameters.

The present invention aims to solve one or more of the problems described above, and in particular, it has a small number of components and can be manufactured easily and quickly (and therefore cheaply) while still being resistant to loads. It is an object of the present invention to provide a support structure such as a box-shaped stake having a special structure with high durability.

DISCLOSURE OF THE INVENTION According to the invention, this object is achieved by:
6 and the first and second end portions 38, 46, 40, 4
an upper plate 22 and a lower plate 24 each having a first plate portion 158, 162 and a first plate portion 158, 162 coupled in series with the first plate portion 158, 162 and having a lower plate portion 8; Thinner second
The upper plate 2 consists of plate portions 160 and 164.
2 and the lower plate 24 to form a box shape, respectively, the first and second side edge portions 50, 52, 54, 56 of both the upper plate 22 and the lower plate 24. first and second side plates 30, 32, the first plate portions 158, 162 extending outwardly from the first end portions 38, 40 of the upper plate 22 and lower plate 24, respectively; the first plate portion 15 of the first and second side plates 30,32.
8,162, the second load input location 72
is on the second plate portion 160,164 of the first and second side plates 30,32, and the third load input location 74 is on the first plate portion 158,162 of the first and second side plates 30,32. said outwardly extending portion 7 of
30, 32 as defined above 8, 80 and U from the first end portion 34 to the second end portion 36.
The first and second ends of the upper plate 22 and the lower plate 24 are made of an integrally cast body extending in the shape of a letter, and have a bottomed box shape as a whole. said first and second side plates 3 at first and second side edge portions 58, 60 defining opposite side edges of a U-shaped elongated casting at end portions 38, 40 of
The first support member 26 is welded to the first plate portions 158, 162 of the first and second side plates 30, 32, respectively.
8,162 having a through hole 122 in the base of the "U" extending from the first side edge portion 58 to the second side edge portion 60 in alignment with said first load input location 70 as defined above. 26, and U from the first end portion 42 to the second end portion 44.
The second part of the upper plate 22 and the lower plate 24 is made of a monolithic casting extending in the shape of a letter, and has a bottomed box shape as a whole. said first and second side plates 3 at first and second side edge portions 62, 64 defining opposite side edges of the U-shaped elongated casting at end portions 46, 48 of
a second support member 28 welded to the second plate portions 160, 164 of the first and second side plates 30, 32, respectively;
a through hole 134 extending from the first side edge portion 62 to the second side edge portion 64 in alignment with the second load input location 72 defined on the second side edge portion 60,164;
28 at the base of the "U".

That is, in the load supporting structure of the present invention, the upper plate, the lower plate, two side plates each consisting of a first plate portion and a second plate portion, and two supporting members are actually simply assembled by welding. Since it can be produced by bonding, its production can be carried out easily and quickly (and therefore cheaply).

From the viewpoint of the shape of the component parts, for example, the load supporting structure of the present invention has a box shape as disclosed in Japanese Utility Model Application Publication No. 52-320, but has two side plates, an upper plate, and a lower plate. In particular, U-shaped integral parts are used at both ends of the upper plate and the lower plate as supporting members to connect them.

On the other hand, from a structural point of view, the load supporting structure of the present invention does not require the provision of a reinforcing plate inside the structure as shown in FIG. This is because the necessary strength can be obtained. One reason for this is that in the load-bearing structure of the present invention, the bottom of a square tube (box) is defined at each end of the upper and lower plates that cooperate with the two side plates to form a box shape. By forming the U-shaped supporting member that is connected as a cast body, the rigidity of the square tube (box) can be reduced to the end (bottom) of the square tube so that the cross-sectional shape of the square tube (box) remains square. This is because the strength of the square tube against lateral loads, etc. was increased. In addition, in the load supporting structure of the present invention, the first and second through holes formed at the base of the "U" of the U-shaped cast body
so that the load applied to each load input location is transmitted to both side plates reliably and as evenly as possible through a highly rigid casting (support member), This is so that the load can be received as evenly as possible on both sides (for example, with respect to the bending load in the normal direction applied to the load input location). Furthermore, in the load supporting structure of the present invention, by thickening the side plate using the thicker first plate portion near the first load input location, one of the three load input locations is increased. This is because the strength against the bending load is maximized near the first load input location, which is located in the middle and is subjected to a larger (maximum) load (therefore, the largest bending stress) than the second load input location. . Note that making the second side plate thinner than the first side plate conversely reduces the weight of the entire structure, and reduces the load on the supporting structure when the structure is used as an arm. It will be possible to do so.

In addition, in the case of the load supporting structure of the present invention, the first end portions of the upper plate and the lower plate are welded and connected to the first U-shaped support member, so that the welded connection portion is Locate the first load input location at the base of the "U" of the first support member that is susceptible to bending loads (in the normal direction applied to the load input location) and that is subject to maximum loads. As a result, the welded connection point is located very close to the first load input location, and there is a high risk that the welded connection point will be damaged by the bending load. In the load-bearing structure of
Since the plate sections extend on both sides of the welding point and support this welding point on both sides, the bending load is actually supported by these two first plate sections, and this welding Since no bending load is actually applied to the part, the load-bearing structure of the present invention can withstand large bending loads, even though it is a structure that can be manufactured easily and in a short time. .

The load-bearing structure is a work element, such as the stake of an excavator, which receives and transmits loads applied to a load input location through the structure. During operation of the excavator, the stake
For example, lateral, torsional, bending, and column loads are encountered through the bucket, boom, and bucket and stake control cylinders. Under the high loads of some operations, the loads can cause the stays to fail. Load input locations are specially positioned within the structure relative to the structural elements to better resist the types of failure commonly associated with the loads that excavator stakes may be subjected to. Ru.

[Brief explanation of the drawing]

1 is a schematic side view of an embodiment of the invention represented in a typical environment as an excavator stand; FIG. 2 is a schematic perspective view of an intermediate stage in assembly of the embodiment of FIG. 1; 3 is a schematic perspective view showing the embodiment of FIG. 1 in detail; FIG. 4 is a schematic cross-sectional view taken along the line - of FIG. 3; FIG. FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings and in particular to FIG. 1, a load bearing structure 10 is shown as a stake 12 of, for example, an excavator (not shown). The excavator has a boom 14 and a bucket 16, as is known in the art, and the bucket has first and second hydraulic cylinders 1 for carrying out the working operations of the excavator.
8 and 20 are interconnected to the stake for controllably positioning the bucket.

The load supporting structure 10 includes an upper plate 22 and a lower plate 24,
It includes a first support member 26, a second support member 28, a first side plate 30, and a second side plate 32. The first side plate 30 is the first side edge portion 50,5 of the upper plate and the lower plate.
4 and, in the illustrated embodiment, first side portions 58, 62 of the first and second support members. A second side plate 32 is coupled to second side edge portions 52, 56 of both the top and bottom plates and to second side portions 60, 64 of both the first and second support members. ing. In the illustrated embodiment, the first and second support members are thus obscured by first and second side plates. The first support member is attached to the first end portion 3 of the top plate at the first end portion 34.
8 and is connected at the second end portion 36 to the first end portion 40 of the lower plate. Second
The support member is also coupled at a first end section 42 to a second end section 46 of the top plate and at a second end section 44 to a second end section 48 of the bottom plate.

The load-bearing structure 10 has a stake 12
(FIG. 1), there are at least first, second and third predetermined load input locations 70 through which associated actuating elements such as the boom 14, the first or stake control cylinder 18, and the bucket 16 are coupled to each other. , 72, 74. 1st and 2nd
A load input location is defined on each of the first and second side plates 30, 32, and the first and second support members 26, 28, respectively, are located at said location. With respect to the second load input location, the first and second side plates 30, 32 protrude outwardly from and adjacent to the first support member, with an outwardly projecting portion 78 thus defined by the side plates. , 80 are spaced apart from each other (see FIG. 3). Third load input locations are formed at predetermined portions of both of the outwardly projecting portions.

Therefore, the load supporting structure 10 generally includes the first and second support members 26, 28 within the box-shaped structure 8.
2, the first and second load input locations 7
0 and 72 at the first and second ends 86 and 88, respectively, of the box-shaped structure. First and second side plates 30, 32 extend outwardly from the box structure to define a third load input location 74. Structural details of load bearing structure 10 will be described below. Recommended methods for fabricating load bearing structures will also be disclosed in detail later in this description.

To form the skeletal assembly 89 shown in FIG.
The respective edges 90, 92, 94, 96 of the end portions 38, 46, 40, 48 of the first and second supporting members 26, 28
(See also FIG. 5). Preferably, the edges of the associated joined end portions are positioned in an abutting relationship, one edge against the other, and the upper and lower plates and support members are arranged at the associated abutting edges. They are joined together by welding along the sides.

Edges 90, 92 of top plate 22 are connected to first and second support members 26, 28 by first and second welds 106, 108, respectively. Lower board edge 9
4 and 96 are connected to the first and second support members by third and fourth welds 110 and 112, respectively. The associated edges connected by the first, second, third and fourth welds are connected to the skeletal assembly 89 between the first and second load input locations 70, 72 as shown. It is desirable that they be located in an abutting relationship at locations along the line.

The first and second side plates 30, 32 each have an inner side surface 113, 115, and the first side edge portions 50, 52 and the second side edge portions of the upper plate 22 and the lower plate 24, respectively, on the inner side surfaces 113, 115. It lies in abutting relation to portions 54, 56 (FIG. 4). As seen in FIGS. 3 and 4, the first side plate is provided with fifth and sixth welds 114 and 116 at the first side edge portions of the upper and lower plates, respectively. , the first related abutment
are joined along side portions and side edge portions.
The second side plate has a second side edge portion of the upper plate and the lower plate.
They are joined along the associated abutting first and side edge portions by seventh and eighth welds 118, 119, respectively.

The predetermined load input locations 70, 72, 74 of the illustrated load bearing structure 10 are represented by pin connections between the excavator stake 12 and associated elements. These load input locations are
The pin thus completes the connection and transfers loads from the various interconnected elements of the excavator to the stay.
or as a portion of the stake forming a hole into which the staple may be disposed in communication.

For example, the first and second side plates 30, 32 each have a first hole 120, 121, and
First support member 26 has an associated alignment hole 122 (FIG. 3). A first predetermined load input location is defined by portions of the first and second side plates defining the respective first holes and by portions of the first support member defining the holes. be done. Preferably, the first support member includes first and second supports located in a respective one of the first holes 120, 121 in each of the first and second side plates to further limit the first load input location. It has ears 124 and 126. Pins 128 are placed through the holes 120, 121, 122 and they constitute the coupling link for the boom 14 (FIG. 1). Accordingly, the portion of the side plate and the first support member defining the first load input location is the area around the associated pin hole which receives the load directed to the load bearing structure via the pin connection joint.

Similarly, first and second side plates 30, 32 have second holes 130, 132, respectively, and second support member 28 has an associated aligned hole 134. The portions of the side plate and the second support member that define the associated respective holes define a second preselected load input location 72 . As with the first load input location 70, the second support member preferably includes the second holes 130, 13.
first and second support ears 1 located on each of the two sides;
Contains 36,137. A pin 138 is placed through the hole defined by the support ear to complete the connection with the bucket control link 76 (first
figure).

A third load input location 74 is defined in outwardly projecting portions 78,80 of the first and second side plates 30,32. Each outwardly protruding portion has a first pin hole 13
9, 140, and the portion of the side plate defining the pin hole has first and second load input locations 7.
Define a third load input location similar to 0.72. The holes are the third support ears 141, 14, respectively.
2 is placed.

Additionally, stake 12 includes a fourth stake 12, as shown, to provide additional connections to excavator elements.
and a fifth predetermined load input location 143,1
It has 44. First, second and third load input locations 70, 72, 74 are located generally along longitudinal axis 146 (FIG. 1) of stake 12. A fourth load input location is defined in the outwardly projecting portions 78, 80 of the first and second side plates 30, 32 and is spaced a predetermined distance from said longitudinal axis and generally adjacent to the first load input location. Located in an adjacent location. A fifth predetermined load input location is located generally along the longitudinal axis between the first and second load input locations.

Fourth and fifth load input locations 143,1
44 are similarly defined as first, second and third load input locations 70, 72, 74. The outwardly projecting portions 78, 80 of the first and second side plates that define holes 148, 150, respectively, in said side plates define a fourth load input location. The portions of the first and second side plates and second support member 28 defining holes 152, 154, and 156, respectively, define a fifth load input location. As previously discussed, the support ears 157 establish load input locations and determine the portions that receive or transmit loads to and from the stakes 12.

To explain in more detail, the load supporting structure 10
The first and second side plates 30, 32 and welds preferably have a special shape to optimize load-bearing ability. The side plates each have first and second plate portions 158, 160, 162, 164 (a third
(Fig.), said first plate sections each have a moment of inertia greater than the associated moment of inertia of the second plate section. First plate portion 15
8,162 are the first and third load input locations 7
0,74 and a second plate portion 160,164
has a second load input location 72. In the illustrated embodiment, the greater moment of inertia of the first plate section relative to the associated second plate section is determined by the width (thickness) of the first plate section (looking at the plate section itself). The "thickness" is the "width" if you focus on a box-shaped object and consider it as a part of it.))W ₁ :
W ₃ is the width (thickness) of the related second plate part (if we focus on the plate part itself, it is its "thickness", but if we focus on the box-shaped object and consider it as a part of it) "Width")) W ₂ ; obtained by increasing W ₄ by a predetermined amount (FIG. 3).

Each of the plate portions 158, 160, 162, 164 has an edge 166, 168, 170, 172, and the edges of the associated first and second plate portions are positioned in an abutting relationship with each other. First and second side plates 3
The first and second plate portions 0 and 32 are joined along the associated abutment portions by ninth and tenth welds 174 and 176, respectively. The edges are preferably positioned in abutting relationship between the first and second load input locations 70, 72 and are oriented generally perpendicular to the longitudinal axis 146 as shown.

The welds used in the load bearing structure 10 are preferably lateral butt welds. This type of weld is shown in detail in FIG. 5, which shows the first end portion 38 of top plate 22 and first end portion 34 of first support member 26. Welding part 106
It represents. The horizontal butt weld is between the top plate and the first
by abutting the two elements such as at the edges 90, 98 of the support member and forming a groove 178, such as the v-shaped groove shown, into which the welding material is fed. made with 1st
The weld 106 is a double lateral butt weld in which welding material is fed into grooves on both sides of the two plates to be welded together. Second welding part 108, third
Weld 110, fourth weld 112, ninth weld 174, and tenth weld 176 are also preferably double lateral butt welds. Fifth welding part 11
4, the sixth weld 116, the seventh weld 118 and the eighth weld 119 are single lateral butt welds. This welded portion is located between the first and second side plates 30, 32.
It is also described as a vertical bevel weld made without backing and formed with a single weld groove to join the skeletal structure 66 to the skeletal structure 66.

The shape of the load-bearing structure 10, and in particular the shapes of the plates, support members and welds, as well as the location of the load input locations, may vary as is known in the art without departing from the invention. The support member as described may be replaced by a tubular member extending between and connected to the side plates. In that case, in order to increase the sectioning properties in the area adjacent to the tubular member, the outwardly projecting portion 7 of the side plate is
Larger width and thickness plate sections may be used, as illustrated in connection with 8 and 80. Elements of the load bearing structure, such as skeletal structure 89, may also be forged or cast, as is known in the art, to further impart desirable properties to the structure.

Industrial Applicability The presented method for fabricating the above-described embodiments of the load-bearing structure 10 lends itself to improved inspection procedures and uniformity of the product. First, the first and second end portions 38, 46 of the top plate 22 are connected to the first end portions 36, 46 of the first and second support members 26, 28, respectively.
42, and the first and second end portions 40, 48 of the lower plate 24 are connected to the second end portions 36, 44 of the first and second support members, respectively. This not only allows the use of welds from both sides to connect elements, but also allows for visual, ultrasonic or other inspection of welds from both the interior and exterior of the structure (89). Figure 2).

The next step includes contacting the skeletal assembly at a location generally adjacent to the skeletal assembly 89 and protruding outwardly from the skeletal assembly side at a portion thereof to be the first support member 26. Second side plate 3
Including placing 0,32. The first and second side plates are then welded to the first and second end portions 38, 46, 40, 4 of the top plate 22 and bottom plate 24, respectively.
8 and first and second support members 26 and 28, respectively.
are coupled to first and second side portions 58, 60, 62, 64 of.

One of the important steps in assembling a welded structure as a load bearing structure 10 is maintaining uniform welds and satisfied manufacturing tolerances. In manufacturing the skeleton assembly 89, the upper plate and the lower plate 2
2, 24, respectively, edges 90, 92, 94, 9
6 and the respective edges 98, 100, 102, 104 of the first and second support members 26, 28 preferably establish predetermined dimensions of the upper and lower plates and the first and second support members. Machined to look like this. By doing this prior to placing the relevant edges in abutting relationship, a uniform skeletal assembly can be assembled efficiently and easily. Machining of the side edge portions 50, 52, 54, 56 of the upper and lower plates 22 and 24 is also preferably performed prior to placing the first and second side plates in contact with said upper and lower plates. .

The shape of the load-bearing structure 10 is easily determined by assembly of subassemblies, such as by clamping, and by eliminating discontinuities along associated adjacent elements, resulting in a uniform and easy manufacturing process. It will be understood. For example, the first and second support members 2
The casting representing 6,28 is not an "additional addition" to the structure, but rather is an integral part of the illustrated skeletal assembly 89, which is fabricated by continuous, uniform welds. In between it serves as an "anchor" to which the side plate is simply and firmly attached. Pre-machining of the weld surfaces eliminates back-up type welds. Back-up type welds can create stress risers and require additional elements or more complex geometries to provide support for the weld.
Also, as mentioned above, the associated edges or sides of the various elements are joined in abutting relationship by butt welding, a technique which further advantageously adds stress properties to the structure.

The section characteristics of the load bearing structure are also controlled to provide load bearing characteristics, particularly with respect to load input locations. For example, the support members and support ears used with the basic box structure 82 are
Generally, it is a casting that provides a larger moment of inertia in a smaller space at various load input locations. The wider (thicker) first plate portions 158, 160 are connected to the side plates 30,
32 to their second plate portions 160, 164 also provides a larger moment of inertia in the area of the first load input location. Additionally, the relatively widely spaced first plate portion provides third and fourth load input locations 7.
4,143, the combination of increased width (thickness) and support ears in that portion of the structure provides sufficient moment of inertia.

The various loads experienced by the stake 12 during excavator operation are illustrated in FIG. 1, for example, for excavation with a bucket 16. Bending force FB ₁ , lateral force
FS ₁ as well as torsional forces are applied at the second load input location 72 by the bucket. 1st
At the load input location 70, the reaction force
RB and RS will be generated accordingly. Bending force FB ₂ and force acting as column load FC ₂
will occur at the third load input location 74 due to the force exerted by the first hydraulic cylinder 18. The second hydraulic cylinder 20 will exert a force at the fourth load input location 143 and a reaction force will occur at the bucket and first, second, and fifth load input locations 70, 72, 144. It will be readily appreciated by those skilled in the art that additional forces, such as lateral bending loads from deflection of the pin at each support ear, may also be applied to the stake. However, for purposes of understanding the improved force handling behavior of stake 12, the few forces described above are sufficient.

When the bucket 16 is in use, the reaction to the forces FB ₁ and FS ₁ applied through the bucket is:
Substantially, this occurs at the first point of attachment of the stake to the external element, ie the first load input location 70. It will therefore be appreciated that the box structure 82 resists the most severe loads on the stake resulting from the complex forces experienced by the bucket through the boom-stay pivot points. Also, the box-shaped structure is the strongest part of the stake, as well as the part with the largest moment of inertia, so it is structurally necessary to resist the bending and torsional loads from the bucket. located in the most advantageous location from the viewpoint of On the other hand, the third and fourth load input locations 74, 14
The forces at 3 are relatively small and in particular the loads that create torsional forces at such points are smaller.

The spaced outward projections 78, 80 of the side plates 30, 32 are sufficient to handle primarily column and bending loads without the need to resist strong torsional forces. This reduces the overall weight of the structure by reducing the need for castings at these points and
And it allows easier access for welding of the first support member 26 or casting to the inner surfaces 113, 115 of the side plates.

Accordingly, the load-bearing structure 10 is designed for ease of manufacture and to minimize discontinuities in the finished structure with uniform welds. The structure is also designed to resist column loads and reduce bending loads across the spaced apart outwardly projecting plate structure and to support torsional loads and larger bending loads through the box structure. This effectively carries the loads encountered during operation. Furthermore, the useful life of a load-bearing structure can be increased by increasing the thickness of the structural elements, especially the plates.

Other aspects, objects, and advantages will become apparent from a study of the specification, drawings, and appended claims.