Machine element or mechanism – Mechanical movements – Reciprocating to reciprocating
Patent
1979-12-26
1982-07-20
Herrmann, Allan D.
Machine element or mechanism
Mechanical movements
Reciprocating to reciprocating
59 7, 173101, F16H 2144, B21L 900
Patent
active
043399614
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
Technical Field
This invention relates to an apparatus for selectively applying pressure to a pair of contact points by movable pressure heads and more particularly to an apparatus for assembling an articulated track chain with the pressure head.
Conventional joints in track chains adapted for use in the track assemblies of track type vehicles include pin and bushing subassemblies having a sprocket engaging bushing and include a first pair of links pressed thereon, a pin rotatably disposed within the bushing, and a second adjacent pair of links pressed onto the opposite ends of the pin. A thrust ring generally positioned in a counterbore in one of the links spaces the assembled links at a preselected distance and cooperates with the counterbore in forming a chamber for receiving a lubricant retaining seal. Typically, track chains are assembled by multi-station track presses such as disclosed in U.S. Pat. No. 4,027,471 issued to Lipp et al, June 7, 1977 and assigned to the assignee of the present invention. The track presses include retractable rams and associated tooling fixtures for simultaneously pressing adjacent, overlapping link pairs onto adjacent pin and bushing subassemblies and indexing subsystems for sequentially moving the assembly a preselected distance from one station to the next.
The assembly of track chains has presented a number of problems including the difficulty of aligning and pressing the parts of a link to assemble them with each other and with previously assembled portions of the chain without introducing bending moments and high residual stresses in the chain or damage to the parts. Yet another problem introduced during assembly is that of controlling link end play to within acceptable limits. To obtain correct assembly, the link must contact or "bottom out" on the thrust ring in the chamber at one end being pressed onto a pin. At the other end, to obtain correct bushing protrusion, the tooling fixture must bottom out on the end of the bushing. One end always bottoms out first. Generally, the ratio of the force required to press a link onto a pin to the force required to press a link onto a bushing is approximately 2:1, if the dimensions of the respective members are nominal, but may vary from 1:1 to as high as 6:1, depending on dimensional variations. Thus, it may be seen that to bottom out the other end of the link for proper assembly, it may be necessary to apply press loads which are high enough to deflect or bend the tooling fixture. This, in turn, places intolerably high loads on the thrust ring which often is crushed in assembly. Additionally, the press fit relationship between the track chain elements prevents relaxation of these elements, thereby introducing high residual loads in the chain, which, in operation, cause thrust ring cracking and premature failure of the track.
Proper operation of the track requires that "link end play" must be controlled. Link end play is the amount of movement of a link along the longitudinal axis of the pin during operation of the track. It is an important parameter from the standpoints of wear and sealing effectiveness. A serious problem associated with excessive end play is the reduction of sealing effectiveness at the bushing-seal interface. Track joint seals are effective only over a limited gap range at the interface. If the gap is too great due to excessive end play, the resultant loss of lubricant will cause damage to the joint and a premature failure of the track chain and excessive vehicle down time.
On the other hand, if there is no end play of the outwardly disposed link ends, the joint during operation may be too tight, causing binding and excessive wear between the link faces, possible damage to the thrust ring, and, again, premature failure of the track chain. These problems are further aggravated by the thickness tolerances of the ends of the adjacent links and the dimensional tolerances of the pin and the bushing.
End play may be reduced by increasing the press forces employed during assembly of the links ont
REFERENCES:
patent: 1946911 (1934-02-01), Lindberg et al.
patent: 2757391 (1956-08-01), Stottlemyer
patent: 3028723 (1962-04-01), Kaplan et al.
patent: 3075346 (1963-01-01), Quarve et al.
patent: 3097477 (1963-07-01), Rodgers
patent: 3939648 (1976-02-01), Cullen
patent: 4027471 (1977-06-01), Lipp et al.
Grillot John W.
Young Teddy R.
Caterpillar Tractor Co.
Herrmann Allan D.
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