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US3574304A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Gasoline engine exhaust valve rotator
Assignee: Briggs and Stratton Corp
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Filing: 1969-03-10
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Granted: 1971-04-13
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Expires: 1989-03-10
Abstract
Abstract The cam for the exhaust valve has a small lobe that momentarily interrupts closing motion of the valve just before it seats, so that the valve slips rotationally relative to its spring under rotational inertia built up during the preceding part of closing motion and induced by rotation of the moving end of the spring. The profiled cam surface is recessed in the neighborhood of said lobe to engage the tappet only at one side of its axis and thus encourage rotation.
Inventors
- 👤 John D Santi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 23:09
CPC Classifications
F; F01; F01L; F01L1/00; F01L1/32; F02; F02B; F02B1/00; F02B1/02; F02B1/04; Y; Y10; Y10T; Y10T74/00; Y10T74/21; Y10T74/2101
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
261 words
A reciprocating internal combustion engine having a poppet valve which is urged axially toward its seat by a helical expansion spring that reacts between a keeper on the stem of the valve and a fixed part of the engine, and which valve is moved off of its seat by a rotatable cam in cooperation with a tappet that is coaxial with the valve stem, said engine being characterized by: A. the cam having a large lobe with a tappet engaging surface which is of increasing radius in the direction opposite to that of cam rotation to effect motion of the valve away from its seat; B. the cam also having a ramp with a cam engaging surface which extends from that of said large lobe in the direction opposite to that of cam rotation and which is of steadily decreasing radius in said direction to permit the spring to accelerate the valve rapidly towards its seat; and C. the cam further having a small lobe, the cam engaging surface of which extends from that of said ramp in the direction opposite to that of cam rotation and is of such rapidly increasing radius in said direction that said small lobe effects an abrupt and brief deceleration of the valve in the latter part of its motion towards its seat to cause a momentary cessation of the rotational force which the spring imparts to the valve as a component of spring expansion, during which cessation the valve continues to turn under its own rotational momentum and slips rotationally relative to the spring.
Claim 2
Dependent Claim
261 words
A reciprocating internal combustion engine having a poppet valve which is urged axially toward its seat by a helical expansion spring that reacts between a keeper on the stem of the valve and a fixed part of the engine, and which valve is moved off of its seat by a rotatable cam in cooperation with a tappet that is coaxial with the valve stem, said engine being characterized by: A. the cam having a large lobe with a tappet engaging surface which is of increasing radius in the direction opposite to that of cam rotation to effect motion of the valve away from its seat; B. the cam also having a ramp with a cam engaging surface which extends from that of said large lobe in the direction opposite to that of cam rotation and which is of steadily decreasing radius in said direction to permit the spring to accelerate the valve rapidly towards its seat; and C. the cam further having a small lobe, the cam engaging surface of which extends from that of said ramp in the direction opposite to that of cam rotation and is of such rapidly increasing radius in said direction that said small lobe effects an abrupt and brief deceleration of the valve in the latter part of its motion towards its seat to cause a momentary cessation of the rotational force which the spring imparts to the valve as a component of spring expansion, during which cessation the valve continues to turn under its own rotational momentum and slips rotationally relative to the spring.
Claim 3
Dependent Claim
66 words
The internal combustion engine of claim 1, further characterized by: that portion of the cam which defines said small lobe having its tappet engaging surface axially relieved at one side of the tappet axis so that the remaining tappet engaging surface of the small lobe cooperates with the tappet in frictionally inducing rotation of the tappet in the direction of said rotational slipping of the valve.
Claim 4
Dependent Claim
95 words
a portion of said surface which extends from the last-mentioned portion thereof in said direction and which has a radius that increases so rapidly in said direction as to provide for an abrupt momentary interruption of spring propelled valve closing motion in a later stage thereof, just before the valve seats, so that during said interruption the valve rotates relative to the spring under its turning momentum built up during the preceding stage of valve closing motion as the valve followed the keeper engaging end of the spring in its rotational component of spring expansion.
Claim 5
Dependent Claim
95 words
a portion of said surface which extends from the last-mentioned portion thereof in said direction and which has a radius that increases so rapidly in said direction as to provide for an abrupt momentary interruption of spring propelled valve closing motion in a later stage thereof, just before the valve seats, so that during said interruption the valve rotates relative to the spring under its turning momentum built up during the preceding stage of valve closing motion as the valve followed the keeper engaging end of the spring in its rotational component of spring expansion.
Claim 6
Dependent Claim
122 words
Mechanism in an inteRnal combustion engine for actuating a poppet valve that has a stem and a coaxial head at one end of the stem and which is movable to and from engagement of its head with a valve seat, said mechanism comprising a cam follower at the other end of the stem for imparting axial motion thereto, a rotatable cam which has a surface engageable with the cam follower and which propels the valve in its opening motion and releases it for closing motion, and a helical expansion spring reacting between a keeper on the stem and a fixed part of the engine to propel the valve in its closing motion, said mechanism being characterized by: the cam being formed with:
Claim 7
Dependent Claim
122 words
Mechanism in an inteRnal combustion engine for actuating a poppet valve that has a stem and a coaxial head at one end of the stem and which is movable to and from engagement of its head with a valve seat, said mechanism comprising a cam follower at the other end of the stem for imparting axial motion thereto, a rotatable cam which has a surface engageable with the cam follower and which propels the valve in its opening motion and releases it for closing motion, and a helical expansion spring reacting between a keeper on the stem and a fixed part of the engine to propel the valve in its closing motion, said mechanism being characterized by: the cam being formed with:
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-04-12 | 1974-10-12 | 1975-04-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-04-12 | 1978-10-12 | 1979-04-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-04-12 | 1982-10-12 | 1983-04-13 | $7700.00 | Window Closed / Lapsed |