US2838857A

US2838857A - Moldboard tilt adjusting arrangement

Info

Publication number: US2838857A
Application number: US374648A
Authority: US
Inventors: Jr George S Allin; George E Bock
Original assignee: Pullman-Standard Car Manufacturing Co
Current assignee: Pullman-Standard Car Manufacturing Co
Priority date: 1953-08-17
Filing date: 1953-08-17
Publication date: 1958-06-17
Anticipated expiration: 1975-06-17

Description

J ne 17, 19 G. s. ALLlN, JR., ET AL MOLDBOARD TILT ADJUSTING ARRANGEMENT 2 Sheets-Sheet 1 Filed Aug. 17, 1953 E fwihinlnlw w 8 a m 2 o ..nfl\"..L mwvqiwmflkwfihwuL H wfl m, n WVNWWEE :SNEI: H M @w) f p. e

June 17, 1958 G. s. ALLlN, JR, ET AL 2,838,857

MOLDBOARD TILT ADJUSTING ARRANGEMENT Filed Aug. 17. 1953 I 2 Sheets-Sheet 2 7 2,838,857 MOLDBOARD TILT ADJUSTING ARRANGEMENT Application August 17, 1953, Serial No. 374,648 12 Claims. (Cl. 37-144) The present invention relates to an arrangement for adjusting the tilt of moldboards of bulldozers or the like, and more particularly to an arrangement for adjusting the pivotal connections of moldboard thrust arms on the lift frame to compensate for variation of the moldboard spacing relative to such connections resulting from tilting of the moldboard, and also for Variation in part dimensions or locations.

While the invention is particularly intended for bulldozers or like earth-moving machines employing moldboards or blades for digging or scraping and pushing earth or like material and is disclosed herein in connection with a bulldozer, it is applicable to many other devices involving adjustment of pivotal connections. A bulldozer moldboard is commonly mounted on a lift frame in such fashion that it may swing to positions obliquely of the machine and tilt in its own plane but cannot shift longitudinallyv of the machine, or in other words along the tilt axis. Adjacent its ends, the moldboard has pivoted a pair of thrust arms extending rearwardly and pivoted on the frame. When the moldboard is tilted to cut or grade at an angle to the plane of the machine, its opposite ends in swinging up or down about the tilt axis also swing about the thrust arm pivots on the frame, with the result that relative displacement of the moldboard occurs along the tilt axis. Since the moldboard is actually held at its center against such displacement, the spacing of the moldboard ends from the thrust arm pivots on the frame is changed and requires some means to compensate for the variation because the displacement of each end is not equal and opposite to the other. In the disclosed embodiment of the invention, adjustment or compensation is achieved by varying the location of the pivot centers of the thrust armson the frame. A trunnion pinis provided which engages in a lug on the frame and has a ball pivot portion journaled in the thrust arm. The pin is rotatable in the lug when not under load, and the pivot portion is eccentric of the pin axis so that it may be shifted about the axis to different positions and thus vary the location of the thrust arm pivot center relative to the lug. Under thrust arm load, the pin is prevented from rotating in the lug by friction, the eccentricty of the pivot portion being insuflicient to provide a turning force due to the load great enough to overcome the frictional force resulting from the load and resisting rotation of the pin.

The invention thus permits the various parts and connections to be made to close tolerances, eliminating misfit stresses and undesirable play and reducing the possi bility of damage by shock loads, and prevents warping or undue stressing of the moldboard or other parts which would occur if no provision were made to compensate for the variations resulting from tilting of the moldboard.

In addition adjustment for variations in dimensions, locations, or spacing of the parts is made possible. It will be apparent that the invention provides improved and advantageous results in the proper positioning of bulldozer and like moldboards.

It is an object of the present invention to provide improved means for connecting the thrust arms of bulldozer or like moldboards to lift frames or other moldboard supports in pivotal relation which allow adjustment of the pivot centers of the thrust arms to compensate for variations in dimensions or spacing of the parts.

Another object is the provision of an improved mounting for a moldboard or like tiltable earth-moving blade of a bulldozer or similar machine permitting adjustment of the pivot centers of the thrust arms on the bladecarrying frame to compensate for movement of the blade along its tilt axis relative to the frame in tilting of the blade.

Another object is the provision of improved means for pivotally connecting moldboard or like thrust arms on a moldboard-carrying support which permit adjustment of the pivot centers of the thrust arms relative to the support and positively prevent shifting of the adjusted pivot centers under load.

A further object is the provision of a trunnion pin for pivotally connecting a moldboard or like thrust arm to a lift frame or other moldboard support which has an eccentric pivot portion for journaling the thrust arm and is rotatable in bearing means on the frame under no load conditions to adjust the position of the thrust arm pivot center and is positively held against rotation when subjected to thrust arm load. 7

It is another object of the invention to provide a trunnion pin for pivotally connecting a thrust arm of a moldboard or like blade to the lift frame or other support for the blade which is rotatably engageable in bearing means on the support and has an eccentric pivot moldboard, thrust arm,,

portion journaled in the thrust arm for adjustment of the thrust arm pivot center by rotation of the pin in the bearing means, the eccentricity being insuificient to cause rotation of the pin under thrust arm load against the friction of the pin in the bearing means under the same load.

Other and further objects, advantages, and features of the invention will be apparent to those versed in the art from the following description and the accompanying drawings, in which:

Fig. 1 is a side elevation of a bulldozer moldboard and its associated mounting means in raised inoperative position on a tractor of which a portion is shown in broken lines;

Fig. 2 is a broken plan view of the moldboard-carrying frame showing a plurality of lugs in one of which is engaged a trunnion pin carried by a thrust arm, and also showing in broken lines a partially engaged position of the pin in a lug;

Fig. 3 is an enlarged fragmentary side elevation, with parts broken away, of a portion of Fig. 1, showing a lug with the trunnion pin engaged therein;

Fig. 4 is a vertical sectional view taken substantially along the line 4-4 of Fig. 3; and

Fig. 5 is a diagrammatic side elevational view of the and frame, illustrating the relative displacement of the moldboard along its tilt axis resulting from tilting thereof.

Referring to the drawings, and particularly to Figs. 1 and 2, there is shown a moldboard 10 of a bulldozer, carried by a generally U-shaped lift frame 11 having each arm journaled on a horizontal pivot 12 secured.

tially the longitudinal axis of the frame by means of horizontal pivot means 14. The pivotal connection of the moldboard to the frame need not be described in detail, since it may be of any suitable construction permitting the two-way swinging of the moldboard specitied. It is to be noted, however, that the connection prevents-any movement of the moldboard along its tilt axis, except such slight movement as may be permitted by play in the pivot parts. A thrust arm generally designated 15, sugstantially in the form of 'a V, is pivoted 'to the rear of the rnoldboard adjacent each end and extends rearwardly' to the corresponding side of the frame 11. Each thrust arm has a lower strut -16 of fixed length extending upwardly and rearwardly from the moldboard to the frame and having a two-part socket portion 17 at its rear end for journaling a trunnion pin. The socket portion 17 has a forwardly and upwardly extending projection 18 to which is pivoted the rear end of an upper thrust arm strut Ztl which has its forward end extending into a sleeve 21 The sleeve has a ball portion at its forward end received in a cooperating twopart socket 22 secured on the rear of the moldooard adjacent an upper corner thereof to provide a ball and socket connection between the upper strut and moldboard. The forward end of the upper strut is threadedly received through the ball portion of the sleeve 21 so that by rotating the sleeve in one direction or the other the strut is projected or retracted by its threaded connection in the ball portion, so that the effective length of the strut 20 may be varied, A pair of apertured cars 23 are provided on the sleeve 21 for engagement by a suitable lever to facilitate turning of the sleeve. This type of upper strut construction is well known in the art, and is employed to effect tilting of the moldboard, as hereinafter explained, The forward end of the lower strut 16 of each thrust arm is pivotally connected to the rear of the moldboard 10 adjacent a lower corner thereof by a substantially vertical pivot, not shown, rotatable in a pivot bracket 24, and a pivot pin 25 disposed at right angles to the vertical pivot and substantially parallel to the moldboard, extending through registering apertures in a swivel block 26 rotatable on the vertical pivot axis and in pivot lugs 27 of the strut 16. The pivot connections of the lower struts to the moldboard are somewhat below the plane of the pivot means 13 and 14.

A trunnion pin 29, best shown in Fig. 4, is provided for each thrust arm 15 to connect the rear end thereof pivotally -to the frame 11. The pin has a ball portion 3% at one end which is journaled in the socket portion 17 of the lower strut, and a body portion of circular cross section and stepped configuration. Adjacent the ball portion, the pin body has a cylindrical portion 31 with a neck portion 32 connecting the ball and cylindrical portions. Spaced axially from the cylindrical portion 31, and adjacent the other end of the pin, is another cylindrical portion 33 of smaller diameter than the portion 31 but coaxial therewith. 'Between the two cylindrical portions, the pin body-has a portion 34 tapered from the larger to the smaller cylindrical portion and the end portion 35 adjacent the smaller cylindrical portion 33 is similarly tapered. A pair of diametric intersecting passages 36, at right angles to each other, are provided through the end portion 35 for selectively receiving a securing pin. The ball portion 30 is offset or disposed eccentrically of the axis of the

cylindrical portions

31 and 33, ortin other words of the trunnion pin body axis A, as appears clearly from Figs. 3 and 4. In the. present instance, the ball portion is set on an axis B intersecting the pin body axis A, for convenience in manufacture, but the axis 13 may be in any other desired offset relation to the axis A, for example parallel thereto, without affecting the invention. The eccentricity of the ball portion 30 relative to the pin body is not required to be very great, as will be evident from Fig. 4. The neck portion 32 preferably is centered on the ball portion axis and formed of greater diameter than the cylindrical portion 31 so as to provide a crescent-shaped flange or shoulder 37 adjacent the portion 31.

On each side of the frame 11 a plurality of lugs 39, in this case three, are secured in longitudinally spaced relation to serve as bearing means for the trunnion pin 29 of the adjacent thrust arm 15. Each lug has a pair of spaced upstanding ears 40 parallel to each other and more or less parallel to the longitudinal axis of the frame. The laterally outer ear 40 has a circular aperture 4-1 (Figs. 3 and 4) of a diameter to frictionally receive the cylindrical portion 31 of the trunnion pin, while the laterally inner car has a similar but smaller aperture 42 (Fig. 4) in which the cylindrical portion 33 of the trunnion pin engages frictionally. The

apertures

41 and 42 are of course coaxial, and the spacing of the lug cars 40 and of the trunnion pin

cylindrical portions

31 and 33 correspond, so that the cylindrical portions engage properly in the respective apertures when the pin 29 is inserted in the lug. The tapered end portion 35 of the pin projects laterally inwardly beyond the laterally inner ear 40 of the lug when the trunnion pin is engaged in the lug, and a securing pin 43 is inserted through one of the passages 36 to prevent accidental withdrawal of the pin. The shoulder 37 of the pin engages the outer face of the laterally outer lug ear 40 to locate the

cylindrical portions

31 and 33 extending through the

apertures

41 and 42, and to hold the trunnion pin against inward movement in the lug, When the trunnion pin 29 is not subjected to any appreciable load by the thrust arm 15, vibration due to the tractor motor or like causes may result in undesired rotation of the pin in the lug. To prevent this, three bosses 44 are formed on the laterally inner car 40, spaced substantially apart about the opening 42 therein, so as to be engaged by the securing pin 43 upon rotation of the trunnion pin in either direction and thus limit such rotation to a few degrees. The pin/l3 may conveniently be attached to the thrust arm 15 by a circle or the like to prevent its loss.

To tilt the moldboard 10, the sleeves 21 of the two thrust arms 15 are turned in opposite directions .0 increase the length of one upper strut 20 and shorten the other. When an upper strut is lengthened, it thrusts against the projection 18 of the socket portion 17 to rotate the lower strut 16 upwardly about the trunnion pin ball portion 39, or counterclockwise as viewed in Figs. 1 and 3, thus raising the adjacent end of the moldboard and with it the forward end of the upper strut 26, the entire thrust arm thus swinging upwardly about its pivotal connection to the frame 11 and carrying the moldboard end to which it is connected in an arc about that pivot as well as swinging the moldboard end upwardly about the moldboard tilt axis. When an upper strut is shortened, it draws the projection 18 toward the moldboard to rotate the socket portion 17 and lower strut 16 downwardly, or clockwise, to lower the adjacent moldboard end by an action the reverse of that caused by lengthening of the upper strut. Thus one end of the moldboard is raised and the other lowered to set the moldboard in a desired tilted position. The turning of the sleeves/must be simultaneous, or one thrust arm must be'disengaged from the frame while the sleeve of the other is actuated, and then its sleeve oppositely turned until the thrust arm is broug t to proper position and its trunnion pin 29 reinserted in the lug.

Referring to the diagrammatic showing in Fig. 5, representing the moldboard .111 in raised inoperative position for tilting, it will be seen that the horizontal pivot pin '25 of each thrust arm lower strut Mis a neutral position N and the ball portion of the upper strut sleeve 21 in a corresponding position N. When the upper strut of one thrust arm 15 is lengthenedto raise the moldboard end, the pin :25 swings in an are about the trunnion pin 29 upwardly to an upper position U, while the ball portion of the upper strut moves upwardly to a corresponding position U, and the adjacent moldboard end is raised to the upper dotted-line position shown. The other end of the moldboard is swung to the lower dotted-line position indicated, as the pin 25 of the other thrust arm swings downwardly .to a lower position D and the ball portion of the shortened upper strut moves to a corresponding lowered position D. Because of the location of the pivots of the parts, however, the vertical and horizontal displacement of one end of the moldboard, or of the pin 25 of one thrust arm, is not identical to the other, although the arcs through which they swing are the same. Thus, since the pivot'pins 25 are positioned below the horizontal or tilt axis pivot 14 of the moldboard, as shown in Fig. l, the vertical distance a which one pin moves upwardly from position N to position U is greater than the vertical distance 0 that the other pin moves downwardly from its position N to position D. The difference in vertical displacement, however, is so slight that for practical purposes it may be disregarded, since it is readily accommodated or taken up by the necessary tolerances between the various pivot parts even when those are relatively close. The horizontal displacement presents a more serious problem, for as readily evident from Fig. 5, the pin 25 swung upwardly from position N to position U moves forwardly a horizontal distance b while the downwardly swinging pin moves rearwardly a horizontal distance d greater than the distance 11, despite the fact that the arcuate movements are identical though in opposite directions. This results from the disposition of the pins 25 offset from the horizontal plane of the pivot centers of the thrust arms on the frame. If the pins 25 were in the same horizontal plane as the frame pivot centers of the lower struts, they would both move rearwardly the same distance, whether swung up or down. It will be seen that since the two. pins 25, or in other words the opposite moldboard ends, are displaced horizontally unequal forward and rearward distances b and d, the moldboard center would have to be displaced along the tilt axis in the direction of the greater distance d by half the difference of these two distances, if the frame pivot centers of the thrust arms 15 were held fixed. The moldboard, however, is prevented from shifting'along its tilt axis by the pivot means 13, as already pointed out, and unless an undesirable and otherwise unnecessarily loose fit of the parts is provided or the moldboard is warped from its intended shape, means must be provided to adjust the thrust arms to the variations in the spacing of the moldboard ends from the lugs. The present invention provides such means.

By rotation of the trunnion pin 29 so that the ball portion 30 revolves about the pin axis A, the ball portion may be shifted forwardly or rearwardly of the axis, so that the thrust arm having its rear end pivoted thereon may be moved in accordance with the horizontal displacement of the adjacent moldboard end resulting from tilting of the moldboard, and thus adjustment for the spacing variations is made. The trunnion pin rotates fairly easily in the lug when substantially relieved of load, .or may be withdrawn from the lug and turned, the securing pin 43 being removed in either case and reinserted after the trunnion pin has been brought to the desired position in the lug. The adjustment may be considered either as varying the effective length of the thrust arm or as changing the location of the thrust arm pivot center on the frame'll, to conform to or compensate for the changed spacing of the moldboard relative to the frame lug, measured horizontally or parallel to the tilt axis, brought about by disposing the moldboard in tilted position. The adjustment may be made by turning one or both of the trunnion pins, as may be necessary or convenient. Thus instead of relying upon loose fitting of the parts for accommodating the difference in displacement of the moldboard ends in tilted position, as has been the common practice heretofore, close-fitting parts may be employed to reduce the effects of shock loading, and the necessary adjustment achieved by the means and in the manner dis-'- closed herein. It will be apparent that the use of the invention is not limited to adjustment for displacement of parts due to movement between different positions, but embraces adjustment or compensation for variations in dimensions, locations, or spacing of parts in manufacture or assembly. It may also be noted that if for any reason, such as an increase in the maximum tilt permitted the moldboard, the difference in vertical displacement of the opposite moldboard ends should be too great to be accommodated by the play in the pivot parts, adjustment will be made simultaneously with adjustment for the horizontal displacement by shifting the pivot centers of the thrust arms on the frame as already explained.

The moldboard 10 may be tilted in either its straightcasting position parallel to the pivotal axis of the frame 11 or a side-casting or oblique position at an angle to the frame pivot axis, swung about the vertical pivot means 13. In either case, the adjusting arrangement compensates for the displacement of the moldboard. The moldboard is swung to oblique position by shifting one thrust arm for the middle lug on one side of the frame to the forward or rear lug, and the other thrust arm from the middle lug on the other frame side to the rear or the forward lug, the trunnion pin 29 of each merely being withdrawn from one lug after removal of the securing pin 23 and inserted in the desired lug. Since the thrust arm swings-about its pivotal connection with the moldboard so that its rear end moves in an arc toward and away from each lug for insertion and removal of the trunnion pin, as the trunnion pin might bind in the' lug and cause difiiculty in engagement or disengagement, if it were" not formed to avoid this possibility. The generally tapered or stepped configuration of the pin 29 assures that it will not become cocked or jammedin the lug as it is inserted or withdrawn, and facilitates engagement in the lug, the tapered end portion 35 and intermediate portion 34 serving to pilot or guide the large cylindrical portion 31 into the lug aperture 41 and the end portion also guiding the small cylindrical portion 33 into the aperture 42.

While the trunnion pin 29 is rotatable in the lug when not under load, it is positively held against rotation when a load is applied, as by the thrust arm. The eccentric ball portion 30, providing the pivot center for the thrust arm, therefore is held in the position to which it has been adjusted and does not shift under load.

This results from the fact that the friction of the

cylindrical portions

31 and 33 in the lug under a given thrust arm load is always greater than the force tending to turn the pin resulting from the same load, the eccentricity of the ball portion being insuflicient to provide a force couple great enough to overcome the friction. In other words, the eccentricity is kept small enough relative to the radii of the cylindrical portions to prevent the thrust arm load from overcoming its friction load reactions; although the reverse statement may be more accurate, that is that the radii of the cylindrical portions are made large enough to assure friction load reactions under a given thrust arm load greater than the product of the eccentricity and the thrust arm load. The precise dimensions or relations may readily be calculated for any particular application. What is claimed is:

1. In a bulldozer or like earth-moving device including a moldboard lift frame vertically swingable on a vehicle, a moldboard carried by the frame tiltable transversely of the frame, a pair of thrust arms pivoted on the moldboard and pivotally connectible to the frame, and means for tilting the moldboard in the plane thereof about a central axis, an improved pivot connection between each thrust arm and the frame comprising a lug on the frame having a pair of parallel ears disposed in vertical planes extending substantially longitudinally of the frame each with a circu-lar aperture therein, the apertures being coaxial and assassr that in the laterally outer ear having a greater diameter than the other, and a truninon pin of suflicient length to extend through the lug having a ball portion at one end journaled in the thrust arm and a body portion with two spaced coaxial cylindrical portions of different diameters respectively corresponding to the apertures of the ears for frictionally engaging therein with the larger cylindrical portion adjacent said one pin end, said ball portion being eccentric of said cylindrical portions, a portion tapering from the larger to the smaller cylindrical portion, a portion tapered from the smaller cylindrical portion to the other pin end, and means for substantially preventing accidental rotation of the trunnion pin in the lug when substantially free of load, the frictional force of the pin in the lug being great enough under thrust arm load to resist rotation of the pin in the lug induced by the eccentricity of said ball portion under said load, whereby the .thrust arm pivot center may be adjusted by revolution of the ball portion about the pin axis under no load conditions to compensate for displacement of the moldboard along said central tilt axis relative to the lug resulting from tilting of the moldboard.

2. In a bulldozer or like earth-moving device including a moldboard lift frame vertically swingable on a vehicle, a moldboard carried by the frame'tiltable transversely of the frame, a pair of thrust arms pivoted on the moldboard and pivotally connectible to the frame, and means for tilting the moldboard transversely of the frame about a central axis, improved means for pivoting each thrust arm on the frame comprising a trunnion pin having a cylindrical portion and a pivot portion journaling the thrust arm and eccentric relative to the axis of the cylindrical portion, and a lug on the frame having a circular aperture frictionally receiving the cylindrical portion of the trunnion pin, the frictional force of the cylindrical portion in the lug being great enough under thrust arm load to resist a maximum force couple tending to rotate the trunnion pin in the lug induced by the eccentricity of said pivot portion under said load and comprising the sole resistance to rotation of said pin under load.

3. A mounting for a bulldozer or like moldboard, comprising a moldboard-carrying frame, a pivot connection between the frame and moldboard permitting tilting of the moldboard in its own plane but substantially preventing movement of the moldboard along the tilt axis, a plurality of circularly apertured lugs on the frame spaced from the moldboard, a pair of thrust arms each pivoted at one end on the moldboard and pivotally connectible at the other end to a lug, means for tilting the moldboard about said axis with resultant swinging of the moldboard and thrust arms about the lugs and variation in the spacing of the moldboard ends from the lugs measured parallel to said tilt axis, and a trunnion pin for each thrust arm having a cylindrical portion frictionally engaged in a lug and a pivot portion journaling the thrust arm disposed eccentric of the cylindrical portion to adjust the location of the thrust arm pivot center relative to the lug in compensation for said variation, the frictional force of the cylinder portion in the lug being great enough under thrust arm load to resist rotation of the pin in the lug induced by the eccentricity of the pivot portion under said load.

4. A mounting for an earth-moving or like blade, comprising a support, a pivot connection between the blade and support permitting tilting of the blade about an axis transverse of the blade but substantially preventing mov ment of the blade along said tilt axis, a pair of lugs on the support each having a circular aperture therein, a pair of thrust arms each pivoted at one end on the blade and also pivotally connected at the other end to one of said lugs, means for tilting the blade with resultant variation in the distance between the blade and each lug measured parallel to the tilt axis due to swinging of the blade and thrust arms about the lugs in upward and downward movement of the ends of the blade in tilting, and means for adjusting the pivot centers of the thrust arms at the lugs to compensate for said variation comprising a trunnion pin carried by each thrust arm having a cylindrical portion fitting frictionally in the aperture of a lug and a pivot portion journaling the thrust arm and eccentric of the axis of the cylindrical portion, said trunnion pin being removable from said lug independently of the mounting of the lug on said support.

5. A mounting for an earth-moving or like blade, comprising a support, a pivot connection between the blade and support permitting tilting of the'blade about an axis transverse of the blade but substantially preventing movement of the blade along the tilt axis, a pair of thrust arms connected to the blade on opposite sides of said axis, means for tilting the blade about said axis, a pair of lugs on the support each having a circular aperture therein, and means for pivotally connecting the thrust arms to the lugs comprising a trunnion pin for each thrust arm having a cylindrical portion frictionally fitting in the aperture of a lug and a pivot portion journaled in and carried by the thrust arm and eccentric of the cylindrical portion revolvable about the cylindrical portion axis to adjust the thrust arm pivot center relative to the lug to vary the effective length of the thrust arm, said trunnion pin being removable from said lug independently of the mounting of the lug on said support.

6. Meansfor pivotally connecting a swingable thrust arm of a bulldozer or like moldboard on a lift frame, comprising a lug on the frame having a pair of parallel ears each having an aperture therein defining a cylindrical surface, said surfaces being of different radii and centered on a common axis extending substantially in the horizontal plane of swing of said thrust arm, and a trunnion pin having a spherical head journaled in the thrust arm and a body with two coaxial cylindrical portions spaced in correspondence to said lug ears and each frictionally engageable with one of said surfaces, a portion tapering from the larger cylindrical portion to the smaller, said pivot head being disposed eccentrically of the axis of the cylindrical portions and under substantially no load conditions being revolvable about said axis to adjust the pivot center of the thrust arm relative to the lug, the frictional force of the cylindrical portion in the lug being great enough under thrust arm load to resist a maximum force couple tending to rotate the trunnion pin in the lug induced by the eccentricity of said pivot portion under said load.

7. Means for pivotally connecting a swingable thrust arm of a bulldozer or like moldboard on a frame, comprising a lug on the frame having a pair of apertures of different radii therein centered on an axis substantially in the horizontal plane of swing of said thrust arm, and a trunnion pin having a spherical pivot head journaled in the thrust arm and a body having two coaxial cylindrical portions of radii respectively corresponding to those of said lug apertures for frictional engagement in the apertures, a portion tapering from the larger cylindrical portion to the smaller, said head being offset from the axis of the cylindrical portions.

8. Means for pivotally connecting a swingable thrust arm of a bulldozer or like moldboard to a moldboardcarrying frame, comprising a lug on the frame having a circular aperture therein, and a trunnion pin having a cylindrical portion adapted to engage frictionally in the lug aperture and a pivot portion journaled in the thrust arm and offset from the axis of the cylindrical portion and revolvable about said axis under substantially no load conditions to adjust the pivot center of the thrust arm relative to the lug for accommodation to variations in spacing and dimensions of the parts, the frictional force of the cylindrical portion in the lug being great enough under thrust arm load to resist a maximum force couple tending to rotate the trunnion pin in the lug induced by the eccentricity of said pivot portion under said load and comprising the sole resistance to rotation of said pin under load.

9. A trunnion pin for connecting-a moldboard thrust arm to a moldboard-carrying frame lug having a pair of spaced coaxial circular apertures of different radii, comprising a pin body having a spherical head at one end adapted to be journaled in the thrust arm, said body being of circular cross section substantially throughout its length and having two cylindrical portions of respective radii to engage frictionally in said lug apertures and axially spaced in correspondence With the axial spacing of said apertures, a conical portion tapering from the larger of the cylindrical portions to the smaller, and a conical end portion tapering from said smaller cylindrical portion, said head extending from the larger cylindrical portion and being located eccentrically of the axis of said body, the frictional force of the pin in the lug being great enough under thrust arm load to resist rotation of the pin in the lug induced by the eccentricity of said head under said load.

10. A trunnion pin for pivotally connecting a thrust arm swingable on a blade to a blade-supporting frame lug having a pair of cars each having a circular aperture coaxial with but of different diameter than the other, comprising a pin body having a ball portion adapted to be journaled in the thrust arm and coaxial cylindrical portions of ditferent diameters each adapted to engage frictionally in one of the lug apertures and a portion tapering from the larger cylindrical portion to the smaller, said ball portion being located eccentrically relative to the axis of said cylindrical portions for adjusting the pivot center of the thrust arm relative to the lug by revolution of the ball portion about the cylindrical portions axis upon engagement of the pin with the thrust arm and lug.

11. A trunnion pin for pivotally connecting a blade thrust arm to a blade-carrying frame lug having a pair of coaxial apertures ofdifferent radii therein, comprising a pin body having a pivot portion adapted to be journaled in the thrust arm and a pair of coaxial cylindrical portions of dilferent radii respectively adapted to engage frictionally in said lug apertures, a connecting portion between the cylindrical portions of less diameter than the larger cylindrical portion, said pivot portion being located eccentrically of the axis of the cylindrical portions, the frictional force of the cylindrical portion in the lug being great enough under thrust arm load to resist a maximum force couple tending to rotate the trunnion pin in the lug induced by the eccentricity of said pivot portion under said load.

12. A trunnion pin for pivotally connecting a thrust arm swingable on a blade to a cir'cularly-apertured bladecarrying frame lug, comprising a pin body having a cylindrical portion adapted to engage frictionally in the lug aperture and a pivot portion adapted to journal the thrust arm and offset from the axis of the cylindrical portion a distance great enough to adjust the pivot center of the thrust arm relative to the lug by revolution of the pivot portion about the cylindrical portion axis under substantially no load conditions to accommodate variations in dimensions and spacing of the parts, the frictional force of the cylindrical portion in the lug being great enough under thrust arm load to resist a maximum force couple tending to rotate the trunnion pin in the lug induced by the eccentricity of said pivot portion under said load and comprising the sole resistance to rotation of said pin under load.

References Cited in the file of this patent UNITED STATES PATENTS 1,917,674 Weaver July 11, 1933 2,159,348 Austin May 23, 1939 2,311,553 Le Tourneau Feb. 16, 1943 FOREIGN PATENTS 145,374 Australia Feb. 25, 1952