From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Patent claim and detailed description for a self-adjusting hydraulic valve tappet.
| Identifier | ExFiles\Box 19\3\ Scan153 | |
| Date | 11th October 1927 guessed | |
| 1,644,840 Patent No. II,122/ the valve stem or valve rod and maintains it in touch therewith at all times, though of course the spring 25 is inferior to the valve spring 14 and cannot obstruct the closing of the valve. The fit of the plunger 19 in the cylinder 17 is reasonably tight and the upward movement of the plunger with respect to the cylinder is accompanied by an outflow of oil from the oil well through a passage 28 into the space between the cylinder end and the plunger cannot return through said passage because of the check valve 29 and consequently the elongation of the tappet by the relative movement between the plunger and cylinder is maintained so that the valve will receive the full throw of the cam. Repeated operations, during which the tappet is subjected to considerable pressure, will effect a very slow leakage of oil around the plunger until the openings 22 are reached, through which it is returned to the oil well, and it is this slow bleeding or leakage that is relied on for permitting the tappet to contract as the other parts elongate and so avoid holding the valve off of its seat, though not permitting play or lost motion. Should the bleeding allow of contraction of the tappet greater than necessary for this purpose, the least tendency to play will permit the spring 25 to slightly lift the plunger with respect to the cylinder and so permit sufficient oil to pass the check valve to restore the tappet to the length necessary for making a close fit between the cam and the valve stem or valve rod. The expansion of the parts is gradual, so that the tappet may easily keep pace therewith in its self-elongation or contraction. Should it become necessary to replenish the supply of oil in the oil well from time to time, it is only necessary to inject oil from an oil can into the plunger, after removing the screw plug 23, preferably at times when the valves are reground and the valve springs are released for that purpose. Should the supply of oil become exhausted or, for any other reason, the hydraulic jack principle fail, the tappet may only be compressed by the action of the cam to an extent that is at present allowed for the play between the tappet and the valve rod for this is the distance that is allowed when adjusting the screw plug 23 while the flange or stop of plunger 19 bears on the end of cylinder 17. That distance will, of course, vary as the effective length of the tappet varies to compensate for contraction and expansion of other parts, but the point now made is that a failure of the hydraulic jack will only allow that amount of play which is now customary and which may be determined by the adjustment of screw plug 23. The use of tappets according to the present invention serves to eliminate the valve noises and the loss of efficiency in wear caused by excessive play or lost motion and still the tappet contains its compensating mechanism within itself so that it may readily replace the ordinary tappets. The internal spring arrangement shown is preferred, though obviously an external spring may be substituted so long as it tends to separate the plunger and the cylinder. While the tappet compensator is herein shown as embodied in the tappet member itself, it will be understood that it may be located anywhere in the line of communication between the tappet member and the valve. What I claim as new and desire to secure by Letters Patent is:– 1. A valve tappet comprising a cylinder forming a tappet member, a plunger working therein and containing an oil well having check valve controlled communication with the space between the plunger and the cylinder, an adjusting screw threaded in the plunger for engaging the valve stem, a cross pin extending through the cylinder without interfering with movements of the plunger, and a spring bearing on the cross pin and on the adjusting screw and tending to separate the plunger and the cylinder. 2. A valve tappet comprising a slidably mounted cylinder forming a tappet engaged by the cam, a plunger working therein and provided with a central bore forming an oil well with a check valve controlled communication with the space between the plunger and the cylinder, an adjusting screw threaded in the bore of the cylinder for engaging the valve stem, there being a transverse opening through the plunger, a cross pin passing through the cylinder and freely contained within the transverse opening of the plunger without interfering with the plunger movements, a guide pin fitting in the cross pin and in the adjusting screw, and a coiled spring surrounding the guide pin and bearing on the cross pin and on the adjusting screw and tending to separate the plunger and the cylinder. In testimony whereof, I affix my signature. ROYAL LEE. [Handwritten note in the left margin] oil level maintains itself from seepage | ||