Patent Application
20130062547
The present disclosure relates generally to a seal for a rotary valve through which air flows, such as an air valve in a carburetor or throttle body.
In a 2-stroke engine, stratified scavenging arrangements have been used to reduce or prevent the blow-through or loss of fuel through exhaust ports at the time of a fuel and air mixture entering the combustion chamber. Some such arrangements use an air passage that is separate from a fuel and air mixture passage, to provide a separate flow of air to the engine.
A seal for an air valve having a valve shaft rotatably carried in a bore formed in a body and a valve head carried by the valve shaft to control air flow through an air passage as the valve shaft is rotated. The seal may include a pair of spaced apart sealing members adapted to engage the body within the air passage to seal a junction between the valve and air passage. The seal may also include an intermediate member between and interconnecting the sealing members, where the intermediate member is flexible to permit movement of at least a portion of the sealing members toward each other and the intermediate member is also resilient to yieldably bias the sealing members away from each other at least when the sealing members are displaced toward each other.
An air valve adapted to be rotatably carried by a body that has an air passage and a bore that intersects the air passage, the air valve may include a valve shaft, a valve head and a seal. The valve shaft may be adapted to be received in the bore in the body. The valve head may be coupled to the valve shaft and adapted to be received within the air passage for rotation to control air flow through the air passage. And the seal may be positioned adjacent to the valve head and have a pair of sealing members adapted to engage the body within the air passage to seal the junction areas between the bore of the valve shaft, the air passage and the valve head.
The following detailed description of preferred embodiments and best mode will be set forth with reference to the accompanying drawings, in which:
Referring in more detail to the drawings,
The throttle valve 16 may include an actuating lever 20 coupled to a throttle valve shaft 22 to rotate the throttle valve shaft 22, and a throttle valve head 26 (presented in dashed lines in
In the implementation shown, the air valve 18 is constructed similarly to the throttle valve 16. In this way, the air valve 18 may have an actuating lever 30 coupled to an air valve shaft 32 to rotate the air valve shaft 32, and an air valve head 34 may be carried on the air valve shaft 32 and at least partially within the air passage 14. The air valve shaft 32 may be rotatably received in a bore 36 that intersects the air passage 14. The air valve head 34, in the implementation shown, is a thin disc or butterfly-type valve head. The air valve head 34 may be rotated from a first position closing or substantially closing the air passage (e.g. as shown in
In more detail, and as shown in
Even when fully closed, air may leak or otherwise flow past the air valve 18 and through the air passage 14. For example, at the interface or junction points between the air valve head 34, air valve shaft 32 and air passage 14, generally labeled X in
As shown in FIGS. 2 and 4-8, one or more seals 42 may be provided for the air valve 18, to seal the junction points X between the air valve shaft 32, air valve head 34 and the air passage 14. In the implementation shown, the seal 42 may be a single, unitary body with all of its features and components formed from the same piece of material. Of course, separate seals could be used for the various junction points X. The seal 42 may have a flat first face 44 adapted to be received against a face of the air valve head 34. The seal 42 may include two opposed sealing members 46 interconnected by an intermediate portion 48.
The sealing members 46 are spaced apart and are adapted to be located at diametrically opposed sides of the air valve head 34 to cover the generally diametrically opposed junctions X of the air valve head 34 and air valve shaft 32. The sealing members 46 preferably have an outer surface 50 adapted to engage the carburetor body 11 within the air passage 14 at one or more, and up to all, of the junction points X. The outer surfaces 50 may be spaced apart a distance equal to or greater than the diameter of the air passage 14 so that each outer surface 50 engages and seals against the carburetor body 11 to limit or prevent airflow therebetween. The outer surfaces 50 may be curved or arcuate and complementary in shape to the air passage 14, or at least somewhat conformable to the shape of the air passage 14. In this way, the sealing members 46 may more effectively seal or block the junction points X and accommodate variations in the size and shape of the air valve head 34, air valve shaft 32 and air passage 14. The sealing members 46 may have a height h (
The seal 42 may also include one or more retention features 54, which are shown in this implementation as being located outboard of the sealing members 46. In the implementation shown, one retention feature 54 is provided outboard of each sealing member 46, providing two generally diametrically opposed retention features 54. Each retention feature 54 may include a knob 56 adapted to be at least partially received within the bore 36 for the air valve shaft 32. The retention features or knobs 56 may have a height (dimension extending away from the first face) that is slightly less than, equal to or greater than the distance from the air valve shaft 32 (and/or valve head 34) to a surface of the bore 36 of the air valve shaft 32 to maintain the seal 42 generally flat against the air valve head 34. That is, the knobs 56 may be closely received in the bore 36 but with some gap between the knob and bore, or the knobs may have an interference fit within the bore. Accordingly, in this implementation, the seal 42 may be retained in place relative to the valve head 34 and air passage 14 without a connection feature, such as a fastener or adhesive, connecting the seal 42 to the valve head 34. This facilitates relative movement between the seal 42 and valve head 34 which may facilitate rotation of the valve head and re-establishing a seal at the junction points X when the air valve is closed again, as will be explained in more detail below. A reduced thickness web 58 may interconnect the knobs 56 to their adjacent sealing members 46 to improve the flexibility of the sealing members 46. The retention features 54 could be formed from the same piece of material as the sealing members 46, as is shown, or they could be separately formed and connected to the sealing members.
To maintain the sealing members 46 a desired distance apart from each other, the seal 42 may include an intermediate portion 48. The intermediate portion 48 may extend between and interconnect the sealing members 46, and the intermediate portion 48 may be received within the air passage 14 and generally against the air valve head 34, if desired. To increase the flexibility of the seal 42, a reduced thickness and/or reduced width connecting portion 59 may be provided between the intermediate portion 48 and the sealing members 46. The intermediate portion 48 may be generally flexible and resilient, and may provide a force that yieldably biases the sealing members 46 radially outwardly into engagement with the body 11 of the carburetor 10 within the air passage 14 at least when the sealing members 46 are displaced or flexed more toward each other than they are in the at rest or uninstalled position of the seal 42. In the implementation shown, the intermediate portion 48 is thin and generally annular and in assembly, surrounds the screw 40 holding the air valve head 34 to the air valve shaft 32. Of course, the intermediate portion 48 could be differently shaped and arranged, including a solid member, a straight strip of material, a spring or other, as desired. The intermediate portion 48 could be formed from the same piece of material as the sealing members 46 and retention features 54, as is shown, or it could be a different piece of material coupled to the sealing members. Further, more than one intermediate portion 48 could be used. To facilitate proper orientation of the seal 42 within the air passage 14 and relative to the air valve 18, an indicator 60 may be provided on the seal 42. As shown, the indicator 60 includes a protrusion on the intermediate portion 48 which provides a visual indicator of the position of the seal 42 during and after installation of the seal.
Because at least a portion of the seal 42 may extend outwardly of the axis of rotation of the air valve 18, the distance between the points of engagement of the sealing members 46 and the body 11 changes as the air valve 18 is rotated between its first and second positions. As shown in
The seal 42 may be formed from any suitable material capable of providing the seal at the junction points X, durable enough for a high number of cycles, and having sufficient resiliency to return to its sealing position (as generally shown in
While shown and described with regard to an air valve 18 of an air scavenging carburetor 10, the seal 42 may also be used in other applications. For example, the seal 42 could also be used with a throttle valve in an air throttle body such as may be used with fuel injected engine systems. In that application, the seal could limit or prevent air leakage through the junction points or areas between the throttle valve head, throttle valve shaft and throttle bore. The reduced or eliminated air leakage may make it easier to calibrate the throttle valve, and/or make calibration more accurate as the size of the leak paths at the junction points will vary from one throttle body to the next due to production tolerances and variations. The seal may make measuring and controlling airflow through a valve more consistent, reliable and easier by eliminating a source of air or fluid flow that is inconsistent and difficult to measure or determine apart from other air flow paths around or through the valve.
While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. It is understood that the terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.
