US2084718A - Back-digger boom construction - Google Patents

Description

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Zei/man,

Phl INVENTOR. er' OMPM HSATTRNEYS.

Patented June 22, 1937 BACK-BIGGER BOOM CONSTRUCTION Roy H. Zeilman, Lorain, Ohio, alsignor'to Thew Shovel Company, Lorain, Ohio, a corporation of Ohio Application July 11, 1936, Serial No. 90,238

4 Claims.

This in'ventlon relates to boom constructions, and more particularly to an improved boom construction adapted to power operated excavating machines of the back-digger type.

The back-digger type of excavating machines usually comprises a dipper stick supported at the boom outer end and movement ef the boom and dipper stick is controlled by cables secured to the dipper and the upper end of the dipper stick. Due to the dipper stick being supported at the outer end of the boom and extended therebeyond during digging operations, the boom'is subjected to considerable stress particularly in compression and torsion. Also, since the cables leading to the dipper are reeved through sheaves disposed generally centrally of the boom, the boom is subjected to a considerable bending moment. The greatest stress will occur in portions of the boom remote from the boom foot or the outer portion of the boom.

Heretofore, it has been customary to provide a relatively heavy boom to care for these stresses and due to the difference in operating conditionsand boom loading, booms adapted to other type excavating machines have not been adaptable to back-diggerrmachines.

I have provided a. boom construction for backdigger machines which is relatively light and a 'detachable member transmits a large portion of the stresses encountered in the outer portion of the boom. Due to the detachable arrangement of this member power shovel and the like booms may be easily converted to back-digger booms.

It is an object of my invention therefore to provide a boom structure for excavating machines having a supplemental stress member in the outer po rtion of the boom.

Another object of my invention is to provide a boom of the above type which is of improved construction relative to the transmission of bending and torsional strains.

Another object of my invention is to provide a boom of the above type which may be relatively economically manufactured and assembled and which is of rugged construction compared to the boom weight.

Other objects of my invention and the invention itself will become increasingly apparent from a consideration of the following description and drawings wherein:

v Fig. 1 is an elevational view of a back-digger type of excavating machine embodying my invention;

Figs. 2 and 3 are enlarged plan and elevational views respectively of the boom of Fig. 1;

Fig. 4 is a view of the boom of Figs. 2 and 3 prior to insertion of the sheave shafts and supplemental stress member;

Fig. 5 is a sectional view taken along line 5-5 0f F18. 2; and.

Fig. 6 is a fragmentary sectional view taken along line 8--8 of Fig. 3. 1

Referring now to the drawingsI I have illustrated in Fig. 1 an excavating machine of the back-digger type comprising a truck generally indicated at I0 upon which is rotatably mounted a superstructure generally indicated at II comprising the power unit and associated mechanism for controlling operation of the boom and supported parts and also movement of the truck..

The superstructure I I is mounted on a turntable indicated at I2 and the boom I3 is hinged at its foot in the usual manner to a forward portion of the turntable. Cables I5 are reeved through sheaves I6 rotatably secured to a dipper stick I1 which pivotally engages boom I3 and jointly with a drag cable I8 secured to a drag bucket IS at the lower end of the dipper stick controls movementof the boom. The cable I5 is also reeved vthrough sheaves 2l! supported on an A frame 2| comprising part of the superstructure mounted on the turntable. A dead end of the cable I5 is secured as indicated at 22 and the opposite end after passing over one of sheaves 2li is wound upon a. rotatable hoist drum (not shown) operable in the usual manner.

The drag cable I8 has a dead end secured in the usual manner to the boom adjacent its foot and then passes over one of two transversely spaced sheaves 23 and is reeved 'through a sheave 24 secured to the drag bucket I9, then it is reversely passed over the second of the pair of sheaves 23 and through a fairead arrangement to a rotatable drum. In this manner, the boom may be raised or lowered together with the parts supported thereby including the dipper stick and drag bucket through manipulation of the cables I5 and I8 in a manner well understood. The operation of the parts thus far described is well understood and a further description is not believed necessary. The boom I3 comprises side plates 25-25 generally channel-shaped in transverse section tapering from a zone of maximum depth generally centrally of the boom towards each end, the channel form preferably being effected by providing longitudinally extending angles which may be riveted or otherwise integrally secured to the sideplate along the top and bottom edges and with the horizontally extending flanges of the angles inwardly disposed. Transverse spacing plates reinforced by angles may be Provided at the lower end of the boom as indicated at 26 and adjacent the outer end of the boom as indicated at 21 which together with a topplate 28 and diagonal tie members 29 comprise the 'transverse spacing members. Rearwardly extending arms at the boom foot indicated at 30 are perforated for the reception of hinge pins side-plates 25 with the projecting U legs being provided with transversely aligned perforations for the reception vof a shaft 34.

As best illustrated-in Figs. 2 and 5, an element generally indicated ,at 35 comprising a central generally box-shaped portion 36 and cylindrical end portions 31--31 is provided with a relatively large transverse bore through the centralportion 36 for the reception of a tubular member 38, the tubular member 38 preferably prior to assembly v.with element 35 being bored to co-axially align with the cylindrical end portions 31-31. The cylindrical end portions form bearings foi` the sheaves 23 which are telescoped thereover and upon projecting the tubular element 38 axially fromv the outer end of the boom to the position illustrated in Fig. 2 and weldingly securing the same to the member 35 along circular zones indicated at 39 and 4U the shaft 32 may be projected through'element 35 and bearing elements 3|. Suitable spacing washers 4I may be provided intermediate the bearing elements and the outer faces of the sheave hub portion.

The opposite end of tubular element 38 is integrally secured to an axially extending tubular portion 42 of a transverselylextending plate element 43 by telescoping portion 42 thereinto and weldingly uniting plate element 43 with the tubular element 38. The plate element 43 is perforated as indicated at 44fwhereby it may be secured to a stiffener plate 45 by bolts 46 and4 nuts 41. The plate 2l is provided with a perforation 48 affording ample-clearance for tubular element 38.

The shaft 34 forms a mounting for guide sheaves for cable I5 and also for perforated and rearwardly extending arms 49 of a yoke element 50, the shaft being projected through the perforated arms of member 33 and secured against transverse movement in any suitable manner as by the provision of collars 5I. The yoke element 50 is integrally secured to the dipper stick I'l whereby the dipper stick may cooperate with the boom I3 in a manner well understood to control movement of the dipper I9.

It will be observed that the elements 35 and 43 are each integrally united with the tubular element 38 whereby torsional stresses encountered when the side of the dipper I9 strikes an obstruction or when rapidly swinging the boom in a lateral direction are absorbed closely adjacent the shaft 34 which transmits such torsional stress to the plate element 43 by the U-member 33 and which stress, in turn, is transmitted to the shaft 32 by tubular element 38 and thence to the boom side plates at substantially the mid-portion of the boom; The stress is then transmitted through the boom proper to the boom foot. -Thusl, the boom is largely relieved of torsional stresses in its weakest portion or 'the portion outwardly from the mid-point of the boom. In a similar manner, a large portion of the compression stresses are transmitted-by the tubular element 33 and the boom side plates 25 are proportionately relieved of compression stresses and primarily absorb thev bending stresses. v

I have described the assembly of the supplemental stress member with the boom as adapting a boom structure illustrated in Fig. 4 to a back-digger boom at the scene of operations or in the field but it is understood that the manner of assembly may be varied as desired or in -accordance with best shop practice when assembled at the factory.

Although I have shown and described modifications of my invention I contemplate that numerous and extensive departures may be made there- Y from withoutdeparting from the spirit of my invention and the scope of the appended claims.

Having thus described my invention what I claim is: 4

1. A boom construction adapted to back-digger type excavating machines, comprising spaced longitudinally extending side plates, transversely aligned bearing elements inthe side plates generally centrally of the boom, a sheave supporting shaft rotatably mounted in the bearing elements, a transversely extending element rigidly fixed to the side plates adjacent their outer ends, and a tubular element rigidly secured to the transverse element at one end of said tubular element and at-its opposite end encircling the type excavating machines, comprising transversely spaced longitudinallyextending side plates, transversely aligned bearing elements in the side plates generally centrally of the boom, a removable shaft rotatably mounted in the bearings, a transverse element integrally secured to the side plates adjacent to the outer en`d, and a tubular element detachably secured to the transverse velement and encircling the shaft adapted to transmit torsional stress from the boom outer end to the boom central portion.

4. The method of converting a boom comprising transversely spaced longitudinally extending side plates into a back-digger boom adapted to withstand severe torsional and compression stresses intermediate the boom outer end and central portions, the method including projecting a tubular element into the boom axially thereof, transversely mounting a shaft having an encircling element associated therewith in the side plates generally centrally of the boom, weldingly securing the inner end of the tubular element to Ithe encircling element, integrally securing a transverse element tothe side plates adjacent the boom outer end, and detachably securing the outer end of the tubular element to the transverse element. l

ROY H. ZEILMAN.

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