US2747559A

US2747559A - Valve tappet with temperature responsive clearance compensation

Info

Publication number: US2747559A
Application number: US367672A
Authority: US
Inventors: Osmon B Campbell
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-07-13
Filing date: 1953-07-13
Publication date: 1956-05-29
Anticipated expiration: 1973-05-29

Description

y 9, 1956 o. B. CAMPBELL 2,747,559

VALVE TAPPET WITH TEMPERATURE RESPONSIVE CLEARANCE COMPENSATION Filed July 15, 1953 Fig .1 "i f 3 INVENTQ 05mm: E CAMPBELL ATTORN United States Patent VALVE TAPPET WITH TEMPERATURE RESPON- SIVE CLEARANCE COMYENSATIQN Osmon B. Campbell, St. Joseph, M0.

Application July 13, 1953, Serial No. 367,672

2 Claims. (Cl. 12390) The invention relates to the valve mechanism of internal combustion engines and is particularly concerned with maintaining a predetermined clearance in the mechanism in spite of the changes in temperature of the parts, which takes place during operation of the engine.

Due to the lengthening which occurs, particularly, in the valve stem, when the engine heats up, quite a large clearance must be provided to make sure that the valves will seat at maximum temperature. Although the temperatures of the different parts of a valve and its gear differ widely, they bear a definite relation to each other, and I use this relationship to maintain the desired clearance throughout the changes in temperature.

I use a temperature sensitive mechanism, preferably within the valve lifter, to ofiset the changes in length of the valve stem, as it undergoes changes in temperature.

Referring to the drawing, Fig. l is a vertical section of the lifter through the middle of the slots in the head of the vertical member. Fig. 2 is a side view of one of the thermal elements. Fig. 3 is a top view of one of the wedges. Fig. 4 is a top view of the head of the vertical member.

I have shown a valve lifter comprising a cylindrical body member 1 having a longitudinal bore, said body being closed at the bottom and open at the top, a vertical member 2, with a flattened top 3, extending upward from the bottom, a pair or a plurality of pairs of metal pieces 4, which are thinner at one end than the other, so that they are wedge shaped, rest upon the flattened top and are adapted to abut the valve stem. Bimetallic thermal elements 5, one on each side of the vertical member, are fixed at one end thereto and engage, preferably, the thick ends of the wedges with their other ends. The extended portion 6, of each thermal element engages half of the wedges through the hole 7, and is slidable in the slot 8, in the other Wedges. By this means the wedges are held in good alignment.

With changes in temperature, flexing of the thermal elements will move the Wedges in and out, varying the total thickness of metal in the clearance. Necessarily,

the thermal elements cannot move the wedges, when the cam is engaged and the valve is off its seat, but a definite, very small clearance is provided in the mechanism, so that the pressure is OE and the wedges are free to move once during each revolution of the cam. The length of movement of the wedges is not great and is far below the elastic limit of the thermal elements, so that they are not damaged by being temporarily restrained.

When designing the device for any engine, the correct cold clearance for that engine, when using tappets with a fixed setting, must be known. Then provide such a relation between the length of travel of the wedges, their taper, and the number to be used, that their action will shorten the effective length of the lifter by the amount of the above mentioned known clearance, when the lifter reaches its maximum temperature.

I have found that any engine cam striking a litter, even with zero clearance, is slightly audible and that with the minimum clearance permissible to insure that the valve will seat, the impact of the valve upon its seat is distinctly audible. I have also found that a clearance of about two thousandths inch does not seemingly increase the sound.

While quiet operation is a feature of this invention, it is not by any means as important as the constant correct timing, which is attained by its use.

I claim:

1. A valve lifter comprising a cylindrical body member having an axial bore, said body being closed at the bottom and open at the top, a second member with flattened top extending upward from the bottom, a pair of wedges movably supported upon said flattened top of the second member, two thermal elements, one on each side of the second member, affixed at one end to said second member, and each engaging one of the wedges at its other end, all in combination and in operative relation to vary the total thickness of the wedges in the clearance, when flexing of the thermal elements occurs in response to changes in temperature.

2. A valve lifter comprising a body member having an axial bore, closed at one end, a standard therein, at least one pair of wedges supported by the standard, slidably movable one upon the other across the axis of the bore, and temperature sensitive elements attached to the standard and engaged with the wedges, so that the wedges will be caused to move upon flexing of the elements.

References Cited in the file of this patent UNITED STATES PATENTS 1,531,909 Engemann Mar. 31, 1925 1,637,020 Fekete et al July 26, 1927 1,689,801 Pope Oct. 30, 1928 1,692,435 Clemenson Nov. 20, 1928 1,696,361 Reich Dec. 25, 1928