US3151406A

US3151406A - Dozer blade including overload relief means

Info

Publication number: US3151406A
Application number: US200380A
Authority: US
Inventors: Edward R Fryer
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1962-06-06
Filing date: 1962-06-06
Publication date: 1964-10-06
Anticipated expiration: 1981-10-06
Also published as: GB973069A

Description

Oct. 6, 1964 E. R. FRYER DOZER BLADE INCLUDING OVERLOAD RELIEF MEANS 3 Sheets-Sheet 1 Filed June 6, 1962 V INVENTOR. {aka a ZZWK BY A TTOR/VEY Oct. 6, 1964 E. R. FRYER DOZER BLADE INCLUDING OVERLOAD RELIEF MEANS Filed June 6, 1962 5 Sheets-Sheet 2 ATTORNEY 1964 E. R. FRYER 3,151,406

DOZER BLADE INCLUDING OVERLOAD RELIEF MEANS Filed June 6, 1962 3 Sheets-Sheet 3 AT T ORNEY United States Patent() 3,151,466 DGZER BLADE HNQLUDING GVERLOAD RELEEF MEANS Edward R. Fryer, Euciid, Uhio, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed June 6, 1962, Ser. No. 206,389 9 Claims. (ill. 37-444) The present invention relates .to a dozer assembly particularly adapted for use with a prime mover having a relatively light frame which would be unable to withstand the extreme forces encountered periodically during dozing.

In general, a dozer assembly typically comprises a pair of push arms, or beams, having one end thereof pivotally connected to a prime mover, such as a rubber tired or crawler tractor. The lower portion of a dozer blade is pivotally connected on a horizontal transverse axis to the front end of the push beams so as to extend transversely of and in front of the prime mover. It is common practice to have rigid or manually adjustable struts extending between each push beam and upper portion of the dozer blade so as to hold the latter in any selected position relative to the push bearns. Hydraulically operated jacks or a cable operated control unit is operatively associated with the dozer blade for moving the latter and its push arms between a lowered dozing position and upper carry position.

During dozing operations, such a dozer assembly is periodically subjected to extremely great forces and stresses due, for example, to the dozer blade encountering a large boulder or other relatively immovable obstruction. Such forces are transmitted by the push beams to the main frame of the prime mover. Because of this, prime movers designed specifically to receive dozer blades are equipped with heavy high-strength frames to withstand the maximum forces which might be encountered.

In many instances, especially where overhung scrapers are used, it has been found desirable to mount a dozer blade in front of the tractor so that a light-duty type dozing operation can be accomplished. It is common knowledge that the frame of an overhung tractor normally designed to accept the stresses imposed in a typical scraper application and not necessarily built to withstand severe bulldozer shock-loading. Hence, unless provision is made for relieving the overloads frequently encountered by a dozer blade, the tractor frame could be damaged due to severe stressing.

Accordingly, one object of the present invention is to provide a dozer assembly having means which permit the dozer blade to trip over an obstacle that would cause extremely large forces and stresses to the frame of a prime mover, and returns the dozer blade to a dozing position upon clearing the obstacle.

Another object of the present invention is to provide a dozer assembly having fluid operated means for moving a dozer blade between a dozing and carry position and includes means permitting automatic expansion and contraction of the fluid operated means whenever the dozer blade is subjected to a predetermined force.

The above and other objects are accomplished with a dozer assembly for a prime mover that includes a dozer blade mounted at one end of a push-arm with a hydraulic jack pivotally connected thereto for raising and lowering the dozer blade between a carry position and a dozing position respectively. Overload relief means are provided in the hydraulic circuit connected to the jack for permit ting the latter to expand and contract whenever the dozer blade is subjected to a predetermined load so that the blade may raise over an obstacle. Means are associated with the dozer blade and the push-arm for returning the dozer blade to a normal dozing position once the blade has cleared the obstacle and in the event of a failure in the hydraulic system when the blade is in a carry position, means are provided for latching the blade to the prime mover.

A more complete understanding of the subject invention can be derived from the following description taken in conjunction with the drawings in which:

FIGURE 1 is an elevation view showing the present invention incorporated with a rubber tired overhung tractor.

FIGURE 2 is a front end view of the tractor shown in FIGURE 1.

FIGURE 3 is an enlarged view of the subject invention with the dozer blade in the various positions assumed after encountering an overload condition.

FIGURE 4 shows the dozer blade in a carry position and shows the safety latch associated with the dozer blade and the tractor vehicle.

FIGURE 5 is a schematic diagram illustrating the fluid circuitry operating the dozer assembly jacks.

Referring to FIGURES 1 through 3, a dozer assembly 2 incorporat ng the subject invention is shown mounted to an overhung two-wheeled rubber tired tractor 4 having the usual frame 5 and pivotally connected by a conventional hitch 6 to a scraper bowl frame 4. Inasmuch as the tractor and scraper form no part of this invention, further detail description thereof is omitted and suffice it to say that the components and operation thereof are conventional.

The dozer assembly 2 comprises a pair of push-arms 10, each of which consist of two forwardly diverging strut members 12. The rear end of each push-arm 10 is pivotally connected at A to a bracket 14 secured to the tractor frame 5. The forward end of each push-arm is pivotally connected at B to a lower rearward portion of the dozer blade mold board 16 to which a cutting edge 18 is secured while a chain 19, secured between the tractor frame 5 and the push-arms, limits downward movement of the latter. The forward end of the strut member 12 includes a stop collar 20 engageable with opposite ends of arcuate stop plates 22 secured to the rear portion of the mold board 16. Engagement between the stop collar and the ends of the stop plates limits pivotal movement of the dozer on the axis B between a normal dozing position illustrated in full lines and the forwardly tipped positions shown by the phantom lines. A spring 24 is connected between each push-arm '10 and a bracket 26 on the rear of the mold board above axis B. The spring members continuously urge the dozer blade to its normal position relative to the push-arms 10 as limited by the aforementioned stop means. On the other hand, the springs permit forward tipping of the dozer blade relative to its push-arms and as limited by the aforementioned stop means in a manner to appear hereinafter.

The dozer assembly is lifted and lowered by means of a hydraulically operated double-acting jack 28 which includes the usual piston 36 and rod 31 and being pivotally connected at points D and C to the tractor frame and the dozer mold board, respectively. As shown in FIG- URE 5, the hydraulic circuit for operating the jack 28 includes

relief valves

32 and 34 connected with lines 35 and 37 for exhausting or filling the jack at either the upper or lower side of the piston 36 In addition, both

relief valves

32 and 34 are respectively connected by lines 36 and 38 to a conventional control valve 40 which selectively supplies fluid pressurized by the pump 42 to either line while returning the fluid to a reservoir 44 via a line 4% when in a neutral position. Each relief valve includesappropriate valving for preventing return flow between the jack 2% and control valve 40, but permitting return flow through other lines when the fluid pressure in either line 35 or 37 exceeds a predetermined design value of the associated relief valve as will be more fully explained hereinafter. The reservoir, pump, and control valve are interconnected by a line 46 while check valves ,5!) and 52 maintain fluid flow in one direction only so as 'to prevent fluid flow toward lines 54 and 56 via the FIGURE 3, it will be noted that pivot connections A, B,

and C and the jack anchorD are illustrated for four different positions of forward travel of the vehicle as the mechanism operates to relieve loads or stress beyond any particular design value. Thus, when the jack 28 is operatedto lower the dozer assembly 2 into a dozing position, as the cutting edge '18 digs into the ground, the resistance acting against the edge creates a counterclockwise moment about the push-arm 1i pivotal connection A which causes the push-arms to rotate downwardly to an extreme'position so as to tighten the chain 19. At this time the push-arms are no longer free to rotate about the pivot axis vA due to the taut chain and the blade is then disposed in its maximum depth dozing position in dicated by the solid lines in FIGURE 3.

As the Vehcle moves from the solid line position toward position No. 2 (indicated by the pivot connections A B C and D the resistance on the dozer blade may vary. If it remains below a predetermined design value of the overload relief valve 34, the dozer blade remains in its normal dozing position relative to its push-arms under the influence ofsprings 24 and due to the fact that the load on the jack 28 is not sufficient to open the relief valve. If this resistance exceeds such design value, the dozer blade rotates counterclockwise about the pivot axis B since the force imposed thereon is great'enough to overcome the spring 24 and open relief valve 34 to permit necessary extension of the jack 28. As seen in the schematic of FIGURE 5, extension of the jack causes fluid to be redirected from the lower to the upper portion of the piston via the line 37, relief valve 34, and line 35. The lower portion of the jack has less volume than the upper portion because of the rod 31, and therefore the deficiency in fluid required to fill the upper portion is provided from the return line 48 which is con nected to line 35 through line 54 and check valve 5%. As the blade continues to rotate in this manner it approaches a centered position between the first and second positions. That is, pivot axis B approaches alignment with pivot axes A and C. If the resistance continues, the dozer blade continues, to rotate counterclockwise about pivot axis B into an overcenter position indicated by the pivot axes A B and C in which E is just above a line passing through the points A and C At this time the dozer assembly collapses. That is, the resistance on the dozer blade rapidly pivots the blade forwardly about axis B and causes push-arms to pivot upwardly about axis A. During this action the springs 24 extend and relief valve 32 operates to permit the jack 28 to shorten. Referring to FIGURE 5, it can be seen that the latter occurs when the piston moves in an upward direction thereby causing a pressure increase in the fluid located in line 35 so as to open the relief valve 32 and follow a path which returns a portion of the fluid to the reservoir 44 through the flow restrictor 58. The restrictor serves to limit the amount of fluid returning. to the reservoir through line 69 and therefore the remainder of the fluid returns via the line 56, check valve 52, relief valve 34, and line 37 to the lower side of the jack. At vehicle position No. 3 (indicated by the pivot connections A B C and D the blade is freely rotated about B against the stop collar.

During the forward tipping movement of the dozer blade, the ground resistance to forward travel of the vehicle acts on the inclined surface of the moldboard 16 to provide a clockwise movement about the pivot axis A thereby forcing the blade to slide upward and forward over the overload resistance, such as a large rock or boulder. During this action, relief valve 32. is operated to permit further shortening of jack 28 in a manner as described above. Position No. 4 (indicated by the pivot connections A B C and D shows the dozer blade a vehicle position after being forced up and {wot a typical overload mass. Once this overload 'is released, the spring 24 in conjunction with the weight of the assembly, rotates the blade to its normal position relative to the push-arm it} in the dozing position. During this return movement of the dozer blade, the extending movement of the jack causes the fluid to flow from the lower portion of the jack to the upper portion as described above.

It should be apparent that this dozer assembly can encounter various conditions other than the one described above and still provide overload relief. For example, the cutting edge 18 can ride over a portion of a boulder or other obstacle partially protruding above ground level without causing the moldboard to pivot forwardly about pivot point B. In this instance, when the vertical force acting against the lower portion of the cutting edge exceeds the design value of the overload relief valve 32, the jack would contract and the moldboard would be raised vertically about pivot A. Once the dozer assembly has cleared the obstacle, the jack can be extended to reposition the moldboard in the normal dozing position.

FIGURE 4 illustrates the manner in which the dozer assembly 2 is stored in a high lift or carry position when not in use. In addition, a safety latching arrangement is shown which serves to operate in case a hydraulic failure should occur. Thus the forward end of the vehicle frame 5 is provided with a pair of spaced keepers 62, each having a cam surface 64 for cooperation with a corresponding latch member 66 carried at the upper edge of the blade and also including a cam surface 68. As aforementioned, the jack 28 may be operated to lift the dozer assembly from the full line dozing position shown in FIGURE 3 to various intermediate positions toward the upper or carry position, as shown in full lines in FIGURE'4. As the dozer blade moves from the dozing position to the carrying position, the members 62 and 66 cam against each other and position and dozer blade, as shown in full lines in FIGURE 4. Should a hydraulic failure occur, the dozer blade will drop from the full line position to the position shown by the phantom lines at which time the member 66 is held in latching engagement with the keeper 62 by the spring 24. It should be apparent at this time that if hydraulic pressure is then reapplied to lower the assembly to the dozing position, the cam surfaces 64 and 63 pivot the dozer blade forwardly about axis B overcoming the force of springs 24. Thereafter, the springs 24 return the dozer blade to its normal dozing position relative "to push-arm 10, and jack 28 continues to operate to lower the assembly into dozing position.

Various changes and modifications can be made in the above described structure without departing from the spirit of the invention. Therefore, it should be understood that such changes and modifications are contemplated and the invention is not limited except by the scope of the appended claims.

I claim:

1. In combination with a tractor having a main frame, a dozer assembly comprising push arm means including a push arm having a first pivotal connection at one end' thereof pivotally mounting the push arm to said frame, a mold board including a cutting blade, said push arm having a second pivotal connection at the other end thereof pivotally carrying the mold board, operating means pivotally connected between the main frame and the mold board for raising and lowering the mold board to a dozing position, said push arm second pivotal connection being located to one side of a line passing through the push arm first pivotal connection and said operating means pivotal connection on the mold board when the latter is in a dozing position, means including the operating means for permitting the second pivotal connection to move across said line and toward the frame when the blade encounters a predetermined resisting force so as to cause said force to pivot the push arm toward the frame, and means interconnected between said push arm and mold board for returning the mold board to a dozing position upon clearing said resisting force.

2. In combination with a tractor having a main frame, a dozer assembly comprising push arm means including a push arm having a first pivotal connection at one end thereof pivotally mounting the push arm to said frame, a mold board having the ground engaging portion thereof mounting a cutting blade, said push arm having a second pivotal connection at the other end thereof pivotally carrying the mold board, operating means pivotally connected between the main frame and the mold board for moving the mold board between a dozing and carry position, said push arm second pivotal connection being located to one side of a line passing through the first pivotal connection and said operating means pivotal connection on the mold board when the mold board is in a dozing position, and means including the operating means permitting the second pivotal connection to move across said line toward the frame when the blade encounters a predetermined resisting force so that said force pivots the push arm about the first pivotal connection toward the frame and thereby raises the mold board to prevent excessive loads from being applied to the frarne, and spring means connected between said push arm and the mold board and including said operating means for returning the mold board to a dozing position upon clearing said resisting force.

3. In combination with a tractor having a main frame, a dozer assembly comprising push arm means including a push arm having a first pivotal connection at one end thereof pivotally mounting the push arm to said frame, a mold board having the ground-engaging portion thereof mounting a cutting blade, said push arm having a second pivotal connection at the other end thereof pivotally carrying the mold board, operating means pivotally connected between the main frame and the mold board for moving the mold board between a dozing and carry position, said push arm second pivotal connection being located to one side of a line passing through the first pivotal connection and said operating means pivotal connection on the mold board when the mold board is in a dozing position, cooperating stop means formed with said push arm and said mold board for limiting pivotal movement of the mold board about the second pivotal connection, and means including the operating means for permitting the second pivotal connection to move across said line toward the frame when the blade encounters a predetermined resisting force so that said force pivots the push arm about the first pivotal connection toward the frame and thereby raises the mold board to prevent excessive loads from being applied to the frame, and means connected between said push arm and the mold board and including said operating means for returning the mold board to a dozing position upon clearing said resisting force.

4. In combination with a tractor having a main frame, a dozer assembly comprising push arm means including a push arm having a first pivotal connection at one end thereof pivotally mounting the push arm to said frame, a mold board having the ground-engaging portion thereof mounting a cutting blade, said push arm having a second pivotal connection at the other end thereof pivotally carrying the mold board, a hydraulically operated jack pivotally connected between the main frame and the mold board for moving the mold board between a dozing and carry position, said second pivotal connection being located to one side of a line passing through the first pivotal connection and said jack pivotal connection on the mold board when the mold board is in a dozing position, and overload relief means operatively associated with the jack for permitting the second pivotal connection to move across said line and toward the frame when the blade encounters a predetermined resisting force so that said force pivots the push arm about the first pivotal connection toward the frame and thereby raises the mold board to prevent excessive loads from being applied to the frame, and a spring connected between said push arm and the mold board and coacting with said jack for returning the mold board to a dozing position upon clearing said resisting force.

5. In combination with a tractor having a main frame, a dozer assembly comprising push arm means including a push arm having a first pivotal connection at the one end thereof pivotally mounting the push arm to said frame, a mold board having the ground-engaging portion thereof mounting a cutting blade, said push arm having a second pivotal connection at the other end thereof pivotally carrying the mold board, a hydraulically operated jack pivotally connected between the main frame and the mold board for moving the mold board between a dozing and carry position, said second pivotal connection being located to one side of a line passing through the first pivotal connection and said jack pivotal connection on the mold board when the mold board is in a dozing position, cooperating stop means formed with said push arm and said mold board for limiting pivotal movement of the mold board about the second pivotal connection, and overload relief means associated with the jack for permitting the second pivotal connection to move across said line and toward the frame when the blade encounters a predetermined resisting force so that said force pivots the push arm about the first pivotal connection toward the frame and thereby raises the mold board to prevent excessive loads from being applied to the frame, and a spring connected between said push arm and the mold board and coacting with said jack for returning the mold board to a dozing position upon clearing said resisting force.

6. In combination with a tractor having a main frame, a dozer assembly comprising push arm means including a push arm having a first pivotal connection at the one end thereof pivotally mounting the push arm to said frame, a dozer blade, said push arm having a second pivotal connection at the other end thereof pivotally carrying the dozer blade, operating means pivotally connected between the main frame and the mold board for raising and lowering the push arm, said push arm second pivotal connection being located to one side of a line passing through the push arm first pivotal connection and said operating means pivotal connection on the dozer blade when the latter is in a dozing position, and means in cluding the operating means permitting the second pivotal connection to move across said line and toward the frame when the lower portion of the dozer blade encounters a predetermined resisting force so as to cause said force to pivot the push arm toward the frame, and means connected between said push arm and the dozer blade for returning the push arm to a dozing position upon clearing said resisting force.

7. In combination with a tractor having a main frame, a dozer assembly comprising push arm means including a push arm pivotally mounted at one end thereof to the main frame, a dozer blade pivotally supported by the other end of the push arm, operating means pivotally connected between said frame and dozer blade for moving the latter between a carry and dozing position, a latch secured to said dozer blade, a keeper fixed to said frame, said latch being located above said keeper when the dozer blade is in the carry position, and means connected between said dozer blade and the push arm to cause said latch to engage said keeper upon failure of said operating means when the mold board is in a carry position.

8. In combination with a tractor having a main frame, a

dozer assembly comprising push arm means-including a push arm pivotally mounted at one end thereof to the main frame, a dozer "olade pivotally supported by the other end of the push arm, a hydraulically operated jack pivotally connected between said frame and push arm for moving the dozer blade between a carry and dozing position, safety latch means incorporated with the frame and dozer blade, said latch means comprising a projection extending from the dozer blade and a keeper formed with the mainframe, said projection being located above said keeper when the mold board is in a carry position, a spring connected between the dozer blade and push arm to cause said projection to engage the keeper and thereby hold the dozer blade in an elevated position upon failure of said jack when the dozer blade is in a carry position.

9. In combination with an overhung tractor having a main frame, a dozer assembly comprising push arm means including a push arm having a first pivotal connection at one end thereof for pivotally mounting the push arm to the frame, a mold board having the ground engaging portion rigidly mounting a cutting blade, a second pivotal connection on the push arm for pivotally supporting the mold board, a hydraulically operated jack pivotally connected between the main frame and the mold board for moving the latter between a dozing and carry position, cooperating stop means formed with the push arm and mold board for limiting pivotal movement of the mold board about the second pivotal connection, a fluid circuit for operating the jack, overload relief means in said circuit for perrnitting the jack to lengthen and shorten when the blade encounters a predetermined resisting force so that the push arm can move about the first pivotal connection towards the frame to raise the mold board, a spring connected between the push arm and mold board for returning the mold hoard toa d zing position when the mold board clears the resisting force; a chain mounted between the frame and push arm t6 limit movement of the latter in a direction away from the frame, and a latching arrangement for locking said mold board to the frame when the mold board is in a carry position and a failure occurs in the fluid circuit;

Referenees Cited in the tile of this patent UNITED STATES PATENTS 2,117,561 McMaster May 17, 1938 arse 124 Qoa tes July 13, 1939 2,254,151 runner Aug; g 1941 2,626,470 Cook et a1. -l Ian, 27, 1953 2,792,650 Kenyon May 21, E57 2,804,702 Corser et all. Sept.- 3, 1957 2,910,790 Armington a Nov.- 3 195? 3,005,511 Riedy Oct; 24, 1961

Claims

1. IN COMBINATION WITH A TRACTOR HAVING A MAIN FRAME, A DOZER ASSEMBLY COMPRISING PUSH ARM MEANS INCLUDING A PUSH ARM HAVING A FIRST PIVOTAL CONNECTION AT ONE END THEREOF PIVOTALLY MOUNTING THE PUSH ARM TO SAID FRAME, A MOLD BOARD INCLUDING A CUTTING BLADE, SAID PUSH ARM HAVING A SECOND PIVOTAL CONNECTION AT THE OTHER END THEREOF PIVOTALLY CARRYING THE MOLD BOARD, OPERATING MEANS PIVOTALLY CONNECTED BETWEEN THE MAIN FRAME AND THE MOLD BOARD FOR RAISING AND LOWERING THE MOLD BOARD TO A DOZING POSITION, SAID PUSH ARM SECOND PIVOTAL CONNECTION BEING LOCATED TO ONE SIDE OF A LINE PASSING THROUGH THE PUSH ARM FIRST PIVOTAL CONNECTION AND SAID OPERATING MEANS PIVOTAL CONNECTION ON THE MOLD BOARD WHEN THE LATTER IS IN A DOZING POSITION, MEANS INCLUDING THE OPERATING MEANS FOR PERMITTING THE SECOND PIVOTAL CONNECTION TO MOVE ACROSS SAID LINE AND TOWARD THE FRAME WHEN THE BLADE ENCOUNTERS A PREDETERMINED RESISTING FORCE SO AS TO CAUSE SAID FORCE TO PIVOT THE PUSH ARM TOWARD THE FRAME, AND MEANS INTERCONNECTED BETWEEN SAID PUSH ARM AND MOLD BOARD FOR RETURNING THE MOLD BOARD TO A DOZING POSITION UPON CLEARING SAID RESISTING FORCE.