US2066600A - Boom construction - Google Patents

Description

Jam. 5, 1937.

E. J. WILSON BOOM CONSTRUCTION Filed Aug. 21, 1935 3 Sheets-Sheet l INVENTOR.

fmery J M/son. BY QM, Q gd 'sA'ITORNEYa Filed Aug. 21, 1935 3 Sheets-Sheet 2 INVENTOR- Emery JM/san. BY '39 6C, '4 QQMXHLLQ MsATTORNEYs Jam. 5, 193% E. J. WILSON fl fi BOOM CONSTRUCTION Filed Aug. 21, 1935 3 Sheets-Sheet 5 P71 32 ir-w 50 INVENTOR. [77767;] J M/l/son.

BY Q m Q ww J' ATTORNEYs fiitentecl Jan. 19 37 UNITED STATES PATENT OFFICE ration of Ohio Application August 21, 1935, Serial No. 37,203

9 Claims.

My invention relatesto boom constructions, and more particularly to an improved boom for excavating machines such as power shovels and the like.

The conventional power shovel comprises a turntable mounted upon a truck and carrying a boom, dipper and dipper stick. The dipper stick is guided by a sleeve structure mounted on a shipper shaft in the boom so that the motion of the stick is confined entirely in a vertical plane passing through the longitudinal axis of the boom. The stick is actuated back and forth by rotation of the shipper shaft, and is swung about the shipper shaft as an axis by a rope attached at the dipper which is mountedon the free end of the stick.

Normal digging without swinging the turntable subjects the boom structure only to bending, due mainly to thethrust of the stick on the shipper shaft, and to direct compression due mainly to the rope pulls. When the turntable is swung with a loaded dipper extended, considerable side load occurs at the dipper due to the inertia of the :dipper and load. When swinging is accomplished or attempted with the dipper embedded in a bank or resting on the ground as in sweeping up operations, the side load at the dipper is frequently great enough to cause boom failure since this side load acts through the stick as a lever arm and produces not only torsion about the axis of the boom but also an equal side load on the boom at the dipper stick guide.

The primary cause of boom failure under the severe conditions encountered is due to the com- W bined torsional and bending stresses to which the boom is subjected, and the torsional strains are a major factor in boom failure despite increase in section modulus to care for these combined strains. .In the conventional boom it is practi- .4o cally impossible to accurately predetermine the .stresses resulting from combined torsional and bending strains.

I have devised an improved boom construction comprising a member which takes substantially all of the torsional stresses and is substantially free from bendingstresses, the bending stresses beingabsorbed by the boom proper.

' It is an object of my invention, therefore, to provide an improved boom construction wherein an auxiliary member absorbs substantially all torsional stresses.

' Another object of my invention is to provide an improved boom construction generally of the fish belly girder type wherein the girders are subtion itself will become increasingly apparent from U jected substantially only to bending and direct compression stresses.

Another object of my invention is to provide an improved boom construction having a member associated therewith adapted to absorb substantially all of the torsional stresses, having improved means for mounting the torsional member.

Another object of my invention is to provide a boom of the above type, wherein side loading at 10 the shipper shaft is carried by diagonal members so that a major portion of the lower part of the boom will be of open construction, resulting in increased visibility for the operator and minimizing blind spots necessarily occurring in a 15 closed construction boom.

Another object of my invention is to provide an improved boom having the maximum resistance to torsional and bending stresses with a minimum of weight.

Another object of my invention is to provide an improved boom of the above type, which is relatively simple and economical in construction.

Other objects of my invention and the invena consideration of the following description and drawings, wherein:

Fig. 1 is a side elevational view mainly diagrammatic of a power shovel incorporating my invention;

Fig. 2 is a plan view of theboom illustrated in Fig. 1;

Fig. 3 is an elevational view of the embodiment of Figs. 1 and 2;

Fig. 4 is a horizontal sectional view showing the method of connecting the torsional member to the shipper-shaft; and,

Fig. 5 is a horizontal sectional view showing the method of connecting the. torsional member at the boom foot.

Referring now to the drawings, and particularly to Fig. 1, I have indicated a shovel turntable generally at It, forming a support at its forward end for a boom H, the boom generally centrally thereof supporting a dipper stick l2 to which is aiiixed a dipper l3. The dipper stick is actuated by a shipper-shaft indicated at l4, and guided by a sleeve [40. pivoted thereon, the shipper-shaft being operable in any conventional manner from the power unit of the shovel. The usual supporting cables for the dipper or bucket are reeved through sheaves at the boom end, and it is apparent that little or no torsional strain can be transmitted through the supporting cables and consequently the portion of the boom outwardly of the 55 shipper-shaft will be subjected to little or no torsional stresses.

The torsional stresses must be transmitted by the portion of the boom extending from the shipper-shaft to the turntable, and in order that the boom proper may be substantially free from such stresses I provide a torsional member generally indicated at I5 in Fig. 2, and which is preferably of tubular construction, as illustrated, since such a construction affords a maximum resistance to torsional stresses for a given cross-sectional area, and the resistance of such a section to torsional strain may be easily computed. The torsion member 15 comprises a tube l6 having an annular flange ll rigidly secured to its outer end in any suitable manner, such as by a fillet weld, as indicated. A yoke member 18 is rigidly and removably secured to the outer end of the tube [6 preferably by a plurality of bolts projected through the flange H and engaging a flange portion of the yoke l 8.

The opposite end of the tube I6 is rigidly and integrally secured to a cross-head generally indicated at l9, the cross-head being mounted adjacent the boom foot in a manner to be later described.

The mounting of the yoke member !8 on the shipper-shaft I4 is best illustrated in Fig. 4, the side plates of the boom, generally indicated at 22, being perforated to receive tubular mounting elements 23 rigidly secured to the side plates, as by riveting. The bore of the mounting element 23 may be suitably bushed to receive a sleeve 25 provided with an outwardly flanged shoulder which abuts the outer face of the element 23 and forms a bearing for an end of the shipper-shaft It.

The sleeve 25 is of sufiicient length to project through a bored portion 26 provided in the arms of the yoke l8, and the sleeve 25 and shippershaft are maintained in fixed relation relative to the yoke ill by pins 27 projected therethrough.

The external surface of the sleeve 25 is provided with an enlarged shoulder, indicated at 28, relatively narrow in width, the remainder of the sleeve being slightly spaced inwardly from the bushing provided in the mounting element 23, whereby the shipper-shaft is permitted to rock a limited amount relative to the boom side plates ensuring that any angular movement of the shipper-shaft in a plane perpendicular to the longitudinal axis of the boom, tending to set up torsional stresses in the boom girders, will be absorbed in a major degree by the yoke 18 and transmitted through the tube and cross-head to the boom foot.

Referring to Fig. 5, the manner of aflixing the cross-head to the lower end of the boom will now be described. Secured to the foot end of the side plates are opposite hand similar castings 30 comprising sleeve portions 3l--3l transversely aligned and alsotransversely aligned bores 3232 for the reception of hinge pins mounted upon the turntable, whereby the boom may be hinged at its foot in the conventional manner. The crosshead is inserted between the inner confronting faces of the sleeves 3| and secured therein by means of a shaft 33, the shaft end portions being encased by rubber bushings 34-34 which abut the end portions of the cross-head at their confronting faces, and the bushings 34 being maintained by means of cap elements 35 detachably secured to the shaft 33 by bolts 36.

It will be noted that the resilient rubber bushings 34 are completely encased and prevented from being forced axially from the position illustrated; and that the torsional loading will produce eccentric movement of the ends of the shaft 33 relative to the sleeves 3| and effect compression of the rubber in one portion of the annular space and force it to move circumferentially to another portion. Thus the rubber will quickly return the torsional member to its normal position relative to the boom upon release of the torsional force.

Mounting of the cross-head in resilient rubber bushings as described permits of a slight twisting movement transversely of the cross-head, without imparting a twisting movement of any appreciable amount to the boom side plates, and further insures that the torsional member will only be subjected to torsional stresses since due to the modifled floating connection, the tension or compression stresses will be absorbed by the rubber mounting.

Diagonal tie rods interconnecting the side plates from points adjacent the shipper-shaft and the boom hinge pins, both at the top and bottom of the boom, afford the necessary strength to carry side loads applied at the dipper stick guide Ma while permitting sufficient flexibility to ensure that torsional strains will be absorbed by the torsional member.

The tube I6 is preferably secured to the crosshead by inserting the lower tube end in an annular flange 43 integral with the cross-head and welding the same thereto.

This open construction not only permits of greater visibility by the operator compared to a closed construction boom, but permits of periodic inspection, and any undue strains to which the torsional member is subjected which might cause cracks will be readily apparent, and the torsional member may be relatively easily replaced by removal of the top tie rods and the cap elements 35, permitting shaft 33 to be removed. The opposite end of the torsional element may be removed from the yoke element upon removal of the bolts projected through the flange I1.

I have thus provided a boom construction wherein the bending stresses are substantially all taken by the conventional side girders of the boom and the torsional stresses are substantially all absorbed by a torsional element associated therewith, resulting in a boom of exceptional strength with a minimum of weight and which can be economically and easily assembled.

Although I have shown a preferred embodiment of my invention, I contemplate that numerous and extensive departures may be made therefrom without departing from the spirit of my invention and the scope of the appended claims.

Having thus described my invention, what I claim is:

1. A boom adapted to be subjected to 'both bending and torsional stresses comprising a foot portion adapted to be secured to a support, spaced longitudinally extending members adapted to receive substantially all of the bending stresses, a transverse element extending through said members at a substantial distance from the boom foot portion and adapted to be subjected to a twisting movement relative to the boom axis, a torsion member rigidly secured to said transverse element and secured to the boom adjacent the foot whereby torsional strain will be transmitted to the boom foot by said member.

2. The boom as described in claim 1 and wherein the transverse element has bearing supports in said longitudinally extending members permitting a limited rocking action of the transverse element relative thereto whereby any twisting action to which the transverse element is subjected will be substantially entirely absorbed by the torsion element.

3. The boom as described in claim 1 and wherein the portion of the torsion element secured adjacent the boom foot is resiliently mounted permitting torsional loads to be transmitted to the support without subjecting the longitudinally extending members to any appreciable torsional stress.

4. A boom construction comprising spaced generally longitudinally extending members adapted to be hingingly secured to a support, the boom being adapted to be subjected to bending stresses about a transverse axis, a transverse element spaced outwardly from the boom foot adapted to be subjected to a turning movement about a longitudinal axis, a longitudinal torsional element rigidly secured to the transverse element at its outer end, the end portions of the transverse element having a rocking bearing connection with the spaced longitudinal members, the lower end of the torsional element having portions resiliently mounted in the spaced longitudinal members adjacent the boom foot, whereby a limited floating action of the torsional member relative to the longitudinal member is permitted ensuring that the torsional member will be substantially free from bending stresses.

5. A boom comprising transversely spaced generally longitudinally extending channel members adapted to be secured to a support at the boom foot, a shipper-shaft having a rocking bearing with the channel members, transversely aligned resilient bushings disposed in the channel members adjacent the boom foot forwardly of the support engaging portion, a rod removably mounted in said bushings, a torsion member comprising a yoke rigidly secured to the shipper-shaft and a cross-head pivotally mounted upon said rod interconnected by a rigid longitudinal portion, the yoke being detachable from the longitudinal portion whereby, upon removal of the rod, the longitudinal portion including the cross-head may be replaced.

6. The boom as described in claim 5 and wherein the channel members are reenforced by tie rods above and below the torsion member, affording a large area of visibility through the boom intermediate the shipper-shaft portion and the boom foot.

7. A boom adapted to be subjected to both bending and torsional stresses comprising a longitudinal member of generally hollow construction adapted to be hingingly secured to a support at its foot, said member being adapted to transmit substantially all of the bending stress to which the boom is subjected, an element extending transversely of the longitudinal member at a substantial distance from the boom foot, a generally axially extending member rigidly secured to the transverse element and secured to the longitudinal member adjacent the hinging support portion, the transverse element being mounted on the longitudinal member so as to permit a limited rocking action whereby, when the transverse element is subjected to a twisting stress relative to the longitudinal axis of the boom, such stress will be substantially entirely transmitted by the axial member.

8. A boom adapted to be subjected to both bending and torsional stresses comprising a longitudinal member of generally hollow construction adapted to be hingingly secured to a support at its foot, said member being adapted to transmit substantially all of the bending stresses to which the boom is subjected, a generally axially extending member mounted at its lowermost end adjacent the boom foot, the opposite end of the axially extending member including a transverse element rockingly supported by the longitudinal element at a substantial distance from the boom foot whereby a twisting action imparted to the transverse element relative to the longitudinal axis of the boom will be substantially entirely transmitted by the axially extending member and means whereby the axially extending element may be detached from the transverse element and removed from the mounting at its lowermost end.

9. A boom adapted to be subjected to both bending and torsional stresses comprising a longitudinally extending member having transversely spaced walls and adapted to be hingingly secured to a support at its foot, said member being adapted to transmit substantially all of the bending stresses to which the boom is subjected, a member extending generally axially of the boom and terminating at each end in transversely extending support elements rigidly secured thereto, the lowermost transverse element being resilent- 1y supported adjacent the boom foot, the uppermost transverse element being rockingly supported by the walls of the longitudinal member and the uppermost transverse element being adapted to be subjected to a twisting action relative to the longitudinal axis of the boom whereby torsional stress occasioned thereby may be substantially entirely transmitted by the axially extending member.

EMERY J. WILSON.

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