US2399375A

US2399375A - Walking apparatus for excavators

Info

Publication number: US2399375A
Application number: US506943A
Authority: US
Inventors: Thomas C Mullins
Original assignee: Marion Steam Shovel Co
Current assignee: Marion Steam Shovel Co
Priority date: 1943-10-20
Filing date: 1943-10-20
Publication date: 1946-04-30
Anticipated expiration: 1963-04-30

Description

April 30, 1946. T. c. MULLlNs 2,399,375

WALKING APPARATUS FOR EXCAVATORS Filed oct. 2o, 1945 2 sheets-sheet- 1 fifa/07026.36

fifmwfwi" n10/VHS C. /VluLLm/s April 30, 1946. r T. c. MULLlNs v 2,399,375

WALKING APPARATUS FOR EXCAVATORS Filed Oct. 20, 1943 2 Sheets-Sheet 2 gyj l 26 @VQ/QZ?? THON/Q5 C. /VULLms Patented Apr. 30, 1946 UNITED STATES PATENT OFFICE WALKING APPARATUS FOR EXCAVATORS Thomas C. Mullins, Chcago,^-Ill., assigner to The Marion Steam ShovelCompany, Marion, Ohio, a corporation of Ohio Application october 20, 1943, serial No. 506,943

- 7 Claims. (o1. iso-s) `This invention relates to improvements in Walking apparatus of the type employed in mobile excavating machines. of the dip bucket or drag line type.

One form of such walking cavators of the mobile type comprises a central base or so-called tub which normallysupports the machine during digging or excavating operations Aand upon which the apparatus can be turned for swinging the boom and bucket, if of the drag line type, or the stick and dipper, `if of the shovel type, into the desired positions for loading` and dumping. In moving such apparatus a pair of shoes of pontoon-like form cooperate with the tub and are operated by crank arm mechanism for lifting the tub and machine from the ground and moving the same forwardly a short distance and then lowering them, whereupon, by continued rotation of the crank arms the shoes are elevated and moved forwardly and then into contact with the ground to again lift the machine and tub and advancing the same another step.

Such walking mechanism generally has been satisfactory especially for use with excavating machines of moderate weight, but it was found that when embodied lin a machine of substantially larger capacity and greater weight, for instance a machine having a drag bucket of twenty-ve cubic yards capacity, the conventional walking mechanism failed several times under conditions that. could vbe expected to be encountered frequently in the use of the machine. Such failures occurred notwithstanding that the walking mechanism of the machine was carefully de signed originally to withstand the expected stresses and, after failure, was Vfurther strengthened, but without correcting the cause of the breakage and avoiding the resultant shut-down i of the machine and reduced coal production.

The principal object of the present invention, therefore, is to provide improvements in walking apparatus of excavating or like machines which without inordinately increasing the size of the parts of the crank arm mechanisms to prevent breakage thereof, affords relative lateral movement of the crank arm mechanisms with respect to the shoes to reduce or avoid imposition on the arm mechanism of destructive stresses resulting from the tendency of the machine to shiftlaterally under certain conditions during walking operations, as where the shoes contact soil affording unequal support at opposite sides of the machine.

An additional object of the invention is to provide a structure accommodating relative apparatus for exmovementbetween crank arm mechanisms and the .respective shoes o f walking apparatus, and tov provide relatively large surfaces of bearing contact between such relativelymoving parts for reducing excessive wear under the large loads imposed on such parts.

Other objects of the invention relate to various features of construction and arrangement of parts which will be apparent from a consideration of the `following specification and accompanying drawings wherein:

Figure 1 is a side elevational view of an excavating machine of the drag line type embodying improvements which are illustrative of the present invention. i

Fig. 2 is a top plan view of the machine shown in Fig. 1;

Fig. 3` is anV enlarged broken plan View illustrating one of the two shoes and associated operating means therefor;

Fig. 4 is a side elevation of the apparatus shown in Fig. 3;

Fig. 5 is a top plan view of a modification of the improvements; and' Fig. 6 is a side elevation of the modification shown in Fig. 5.

In Figs. 1 and 2 of the drawings a drag line machine is shown which comprises a house or housing I0 within which is positioned the major portion of the operating mechanism (not shown) including a control cab or compartment for the operator and power .units by means of which the power operated boom ll can be raised and lowered by cables I2 and whereby a bucket I3, provided vwith haul and hoist lines I4 and l5, respectively, can be loaded, elevated and supported by the boom as the machineis swung upon its turntable from loading to load-discharging positions and vice-versa. The details of such parts being well-known are not shown in the drawings nor are the conventional power means, such as the electric motors that supply the control and operating power and which are positioned within the housing l0. Whether the apparatus isl electrically operated, as may be assumed in the present instance, or is operated by steam or Diesel' power is not important insofar as the present invention is concerned.

The conventional apparatus shown also comprises a tub I6 .which normally supports the machineduring excavating operations and upon which the machine may be rotated or oscillated in swinging the housing and boom arcuately for carrying a loaded elevated bucket to and from load 'and discharging positions.

At opposite sides of the machine are shown shoes Il which cooperate with the tub I6 during walking operations. The conventional means shown for operating the shoes comprise a power operated shaft I8 extending from each side of the housing and provided with crank arms I9 at each side of the machine but inasmuch as the parts of the walking mechanism ateach side of the machine are similar and areV operated in unison, only the parts at one side of the machine as shown in Figs. 3 and 4 will be described.

Pivotally secured to a crank pin Illa at the end of the crank arm I9 is a leg or link 20 which,

in the form shown constitutes one side of a triangular member 2| and to the forward apex of which is pivotally attached at 22 the lower end of a link 23 which at its upper end (see Fig. 1) is pivotally attached at 24 to the exterior supporting structure 25, which in turn is secured at its upper portion to the framework of the super-.structure of the machine and atits lower end is secured to a laterally extended portion 26 of the base 2l of the machine.

In such types of walking mechanisms hereto fore employed, the lower ends of the links or legs 20 have been attached pivotally by suitable bearing means directly to the respective shoes without interposed means for accommodating relative lateral movement vof the crank arm mechanisms with respect to the `shoes while the arms are elevating the machine. In large capacity machines in particular, such as are herein under consideration, it was found that breakage of the crank arm mechanism at one side of the ma1 chine or the other occurred notwithstanding that those Darts Were Originally so designed and subseu quently strengthened to provide whatappeared to be adequate strength to withstand the stresses normally imposed thereon. However, it has `been.

found that due to the tendency of a machine to shift laterally during walking operations when one shoe is less firmly supported by the ground than the other, lateral stresses were set up which caused failures even of the strengthened cranky arm mechanisms.

During the walking operations, the shaft I8 is rotated in one direction (counter-clockwise as viewed in Figs. l and 4') which, by reason of the controlling action of the members 2l and 23 causes the legs 20 to move downwardly during the rst portion of the walking operation and press the shoes I 1 into contact with the ground and, as the rotation of the shaft I8 continues .to lift the tub and machine and move it to the left, (as viewed in said figures) and thereafter to lower the tub and machine and then lift the shoes and move the latter arcuately to the left (counterclockwise) in preparation for the next downward movement constituting the beginning of the next walking step or cycle. Since the machine can be swung arcuately in either direction when the tub supports the machine and the shoes are elevated, the machine can be caused to walk in any angular direction from a given position. Such walking operations, as stated, have resulted in breakage of the crank arm mechanism at one side of the machine or the other under conditions wherein one shoe failed to provide adequate support for the load due to the character of the supporting earth. Under such conditions apparently a greater portion of the work in elevating the machine was imposed on the crank arm mechanism on the other side of the machine which apparently set up laterally directed stresses which, with the shoes unable to shift laterally by reason of their contact with the ground, caused breakage of one or the other of the crank arm mechanisms.

For the purpose of compensating for the inability of the shoes to shift laterally while in contact with the ground and while offering unequal support for the machine during the walkingoperation and to preventthe setting up of -destructive lateral stresses in the crank arm mechanism, means have been provided to permit limited relative movement between the crank arm structure and the respective shoes. Such lateral shifting can be accommodated by various structures, two of which are shown for illustrative purposes in the drawin-gs.

As shown in the drawings the lower end of each crank arm 20 is pivotally secured at 28 to a saddle bearing indicated generally by numeral 29 and 'comprising a member 30 which itself is pivotally mounted at its ends in brackets or supports 3|. Such saddle bearings 29 accommodate movement of the arms 20 to slightly different angular posi tions of the shoes when pressed against the ground, but instead of being secured directly to the shoes Il as heretofore, said bearings are secured to plates 32 which are so mounted on the respective shoes that they can shift laterally relative to the same though limited distances when excessive lateral stresses are imposed on the crank arm mechanisms.V The plates 32 while movable upon the shoes are attached thereto by suitable means so that during elevation of the plates during walking operations the shoes will be lifted and moved forwardly as heretofore.

The means shown in Figs. 1 to 4 for securing each plate 32 to a shoe I 'l comprises a pair of cables 33 each attached to the respective end of the plate as by eye members 34 and to the shoe by eye members 35. Sufficient slack is provided in the cables to enable the plate to slide laterally on the shoes to a limited extent, a few inches to a foot generally bein-g adequate for adjustment ol the plate with respect to a shoe in response to imposed lateral stresses and hence to prevent breakage of the crank arm mechanisms from that cause. The plates 32 contact relatively large portions of the surface area of the respective 'shoes and hence wear of the contacting surfaces is kept at a minimum.

Upon elevation ol the plates during a walking operation, the cables 33 will elevate the shoes and permit the latter to reassume normal positions with respect to the plates but due to the slack provided in the cables as mentioned, a slight vertical separation of the plates from the shoes will occur during that portion of the walking cycle. Where such separation is objectionable, substantial contact between the plates and respective shoes can be maintained by any suitable means such, for example, as shown in Fig. 4 or by the modification of the structure illustrated in Figs. 5 and 6.

In Fig. 4 there is shown a cable 36 which is attached at its ends to end portions of the shoe Il and passes tautly over a grooved cam or eccentric 31 mounted on the crank pin |9a and secured to the leg 20 against relative rotation with respect to the latter.

When the crank arm mechanism is in the shoe elevating position shown in Fig. 4, the eccentric 31 retains the shoe in suitably close contact with the plate'whereby the shoe is elevated to the greatest extent for reducing drag on-the shoe the shoe within a walking cycle. Such arrangement permits relative lateral movement of the shoes Il with respect to the plates 32 as stated and during elevation of the shoes to the position shown in Fig, 4, when the load is removed from them, the shoes by gravity readjust or realign themselves from a laterally or longitudinally displaced position with reference to the plates.

The modied structure shown in Figs. and 6 eliminates the use of the cable 36 and eccentric 3l by providing a pair of transverse bars 38 which extend across the upper surface of the plate 32 and are attached at the ends to the upper surface of the shoe Il. The length of the bars and vertical spacing between the intermediate portions of the b-ars and shoes is such as to accommodate sliding movement of the plate without permitting appreciable relative vertical movement between the shoes and plates whereby the latter, during the elevating portion of a walking cycle will pick up the shoes without lost motion.

In Figs. 5 and 6 the ends of the plate 32 are shown attached to the shoes also by short cables 33 as in the structure shown in Fig. 4 and in addition means are provided for restoring the shoes to normal relation following lateral displacement thereof.

The last mentioned means shown for illustration are in the form of coil springs 39 under compression between pairs of seat members 40 to il secured respectively to the shoe and plate. Upon elevation of the shoes, the springs 39 will restore the shoes to original position with respect to the respective plates following lateral displacement, should such occur, during the portion of the walking cycle within which the load of the machine is imposed upon the shoes.

While I have shown and described structures for permitting relative movement between the crank arm mechanisms and the respective shoes while the latter are in contact with the earth and are supporting the weight of the machine, and have provided relatively large bearing surfaces between the plates and shoes for distributing the imposed loads and reducing wear of the parts between which such relative movement occurs, it will be apparent that other modication of the disclosed structure may be utilized within the spirit of the invention.

I claim:

1. Walking apparatus for an excavating machine comprising a crank arm mechanism and an associated shoe at each side of the machine, plates each secured to one of said mechanisms and arranged to bear on the upper surface of the respective shoes for transmitting to the latter the weight of the machine during the machine elevating and advancing portion of the walking cycle, and means comprising flexible members operatively attaching the shoes to the respective plates whereby the latter can slide laterally of the shoes during said portion of the walking cycle and said shoes will be suspended from said plates during a succeeding portion of the walking cycle and will be free to return to their original positions with relation to the respective plates.

2. Walking apparatus for an excavating machine comprising a crank arm mechanism and associated shoe at each side of the machine, a plate secured to each mechanism and arranged to make load-supporting contact with the respective shoe during the machine elevating and advancing portion of a walking cycle, and iiexible means attaching said shoes to the plate to accommodate limited relative movement between the respective shoes and plates during said portion of the walking cycle.

3. Walking apparatus for an excavating machine comprising a crank arm mechanism and associated shoe at each side of the machine, a plate secured to each mechanism and arranged to make load supporting contact with the respective shoe during the machine elevating and advancing portion of a walking cycle, and means comprising iiexible members attaching the shoes to the respective mechanisms for affording relative sliding movement therebetween and for effecting elevation and advancing movements of the shoes during the remaining portion of a walking cycle.

4. Walking apparatus for an excavating machine comprising a crank arm mechanism and an associated shoe at each side of the machine, a plate on the upper surface of each shoe Providing a relatively large area of contact therewith, means attaching each plate to the respective mechanism, and flexible means at opposed portions of each plate securing the same to the respective shoe to enable limited relative sliding movement of the plate upon the shoe during the machine elevating and advancing portions of a walking cycle.

5. Walking apparatus for an excavating machine comprising a crank arm mechanism and an associated shoe at each side of the machine, a slidable load distributing plate on the upper surface of each shoe, means operatively securing each mechanism to the respective plate, and means comprising flexible members securing each plate to the associated shoe for limiting the sliding movement of the former with respect to the latter and for supporting the shoes during the shoe elevating and advancing portion of a walking cycle.

6. Walking apparatus. for an excavating machine comprising a rotary crank arm mechanism and a ground engaging shoe at each side of said machine, load supporting and distributing plates, connected with the respective crank arm mechanisms for movement thereby and arranged to bear upon theupp'er surfaces of the respective shoes during the machine advancing portion of a walking cycle, and means for connecting each plate with its associated shoe for movement as a whole on and transversely to said shoe during said machine advancing portion of said walking cycle, for preventing substantial movement of said plate lengthwise of and with relation to said shoe and for causing said shoe to move with said plate during a succeeding portion of said walking cycle.

7. Walking apparatus for an excavating machine comprising a rotary crank arm mechanism and a ground engaging shoe at each side of said machine, load supporting and distributing plates, connected wth the respective crank arm mechanisms for movement thereby and arranged to bear upon the upper surfaces of the respective shoes during the machine advancing portion of a walking cycle, and means for connecting each plate with its associated shoe for movement as a whole on and transversely to said shoe during said machine advancing portion of said walking cycle, for preventing substantial movement of said plate lengthwise of and with relation to said shoe and for supporting said shoe for movement with relation to said plate to its original position during the shoe advancing portion of said walk. ing cycle.

:THOMAS C. MULIDIS'