Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed

Field of the invention
[0001] The present invention relates to a sealing ring for a spark plug.

[0002] Background of the invention
[0003] As a standard, it is required from spark plug to not have leakage more than 2cc/min at higher temperatures. The leakage of the combustion gases can be attributed to a low efficiency or a damaged sealing ring between Spark Plug housing and engine cylinder head. Typically, a compressible metal sealing ring provides spring stiffness and prevents leakage of the combustion gases.

[0004] The spark plugs are tapped inside the cylinder heads by screwing them into a tapped bore in a cylinder. In order to screw the spark plug into the cylinder bore, torques are applied. Between the spark plug and the cylinder head bore, a sealing ring is provided so as to prevent any gases from leaking the cylinder head.

[0005] However, these sealing rings are prone to deformation and damage when the spark plug is screwed into the cylinder head and is tightened with a predetermined torque. When tightening the spark plug, a significant deformation of the sealing ring occurs and a predetermined spark position can be achieved. The efficiency of the sealing ring depends on the stiffness of the system, and stiffness depends on the material and shape of the sealing ring.

[0006] The prior art JP2010027626A discloses a cross section of a gasket 80 made of stainless steel of high rigidity to be mounted on the spark plug for use, provided, the number of layers of plate materials at a site where the most layers of the plate materials overlap each other in an axis-line O direction is n, and a total of thicknesses of the layers at the most-overlapped site (a total thickness) is denoted by L, a thickness x of the gasket 80 as a whole satisfies: 1.1L≤x≤1.45L. Clamping torque increases as clamping of the spark plug progresses at its fitting, but, the gasket 80 first begins to generate elastic deformation, and, when it reaches the limit, generates plastic deformation. The above formula is satisfied at this point, so that, the plate materials themselves get adhered to each other during the elastic deformation, or soon after generation of the plastic deformation, which hardly gives rise to loss of the axial tension.

[0007] The present disclosure provides a new shape of the outer sealing ring in order to achieve greater spring stiffness and better leak tightness. Further, the disclosed sealing ring can result in a slimmer design using less material.

Brief description of the accompanying drawings
[0008] An embodiment of the invention is described with reference to the following accompanying drawings:
[0009] Figure 1 depicts a sealing ring of a spark plug installed in a cylinder head
[0010] Figure 2 depicts a sealing ring in a parallel spring arrangement.

Detailed description of the drawings:
[0011] The efficiency of the outer sealing ring to prevent any leakage depends on the stiffness of the system, and stiffness depends on the material and shape of the sealing ring.
[0012] Disclosed is a shape of a sealing ring capable of achieving superior spring stiffness and hence better leak tightness. There are three curved members in the disclosed sealing ring, wherein, the two curved members in series are in parallel arrangement with the first curved member. incorporates taking advantage of the spring stiffness in a parallel arrangement, thereby achieving higher stiffness.
[0013] A curved member of the sealing ring with spring stiffness K1 is parallel to a second curved member of stiffness K2 and a third curved member K3. The Curved members with stiffness K2 and K3 are in series . The equivalent stiffness of this spring system adds up, wherein, Keq = K1 + ( K2 K3/(K2 + K3))
[0014] The sealing ring is designed such that a radius R1 (between a longitudinal axis of the spark plug and the first curved member) reduces on application on compressive load during assembly. The sealing ring gets locked in the spark plug groove with certain rotational degree of freedom and limited translation along the spark plug longitudinal axis within the confines of the groove in the spark plug, but it cannot be removed from the spark plug without permanent damage to either spark plug or the sealing ring. Also during installation of the spark plug on the engine, the radius R1 further reduces but not to the extent that it interferes with the outer diameter of the spark plug groove.
[0015] The radius R2 and R3 (between the longitudinal axis and second and third curved member respectively) are such that they increase when compressive load is applied during assembly and further during application of the torque on the spark plug when it is installed on the engine. In any case it does not Interfere with the inner diameter of the cylinder head.
[0016] The present invention will now be described by way of example, with reference to accompanying drawings. Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations, and fragmentary views. In predetermined instances, details which are not necessary for an understanding of the present invention, or which render other details difficult to perceive may have been omitted.
[0017] Figure 1 depicts a sealing ring of a spark plug installed in a cylinder head. The sealing ring is secured within a groove (6) defined between a spark plug housing (4) and a cylinder head (5) of an engine. The sealing ring comprises a first curved member (1) comprising an upper-portion (1a), a lower-portion (1b) and a body portion extending between the upper portion (1a) and the lower portion (1b). A second curved member (2) is formed by extending and bending the upper portion (1a) of the first curved member (1) towards the body portion of said first curved member (1). A third curved member (3) formed by extending and bending the lower portion (1b) of the first curved member (1) towards the body portion of the said first curved member (1), such that, an end (3a) of the third curved member (3) is slidable with an end (2a) of the second curved member (2).

[0018] Figure 2 depicts a sealing ring in a parallel spring arrangement. A radius R2 defined between a longitudinal axis (7) of the spark plug and the second curved member (2) increases when a force is applied in the direction of the longitudinal axis of said sealing ring. Similarly, a radius R3 defined between the longitudinal axis of the spark plug and the third curved member (3) increases when the force is applied in the direction of the longitudinal axis (7) of said sealing ring. The radius R1 defined between the longitudinal axis of the spark plug and the first curved member (1) decreases when the force is applied in the direction of the longitudinal axis of said sealing ring.

[0019] The second curved member (2) and the third curved member (3) together constitute a stiffness (K) that is equal to a ratio of the product of an individual stiffness (K2) of the second curved member and an individual stiffness (K3) of the third curved member; and the sum of the individual stiffness (K2) of the second curved member and the individual stiffness (K3) of the third curved member.

[0020] The first curved member (1), the second curved member (2) and the third curved member (3) constitute an equivalent stiffness (Keq) that is equal to a sum of the stiffness (K) and the stiffness (K1) of the first curved member. The second curved member (2) and the third curved member (3) are equivalent to two springs that are sequentially connected in series.

[0021] The first curved member(1) is equivalent to a single spring,(1) such that the two springs (2, 3) that are sequentially connected in series is in parallel arrangement with the single spring (1).

[0022] The sealing ring is adapted to be displaced within the groove and wherein the sealing ring is adapted to partially rotate within the groove (6) (see Fig 1) to enable the sealing ring to snugly fit within the groove. The sealing ring is manufactured from a material such as but not limited to zinc plated steel. The sealing ring is an integrally formed unitary member that is secured within the groove defined between the spark plug housing and the cylinder head of the engine.

[0023] The disclosure advantageously provides seal tightness in order to prevent leakage of hot combustion gases from the spark plug, it further allows for a higher angle of rotation while torquing thereby reducing the chances of damage to the housing threads or the sealing ring.
, Claims:
We Claim:
1.A sealing ring for a spark plug that is secured within a groove (6) defined between a spark plug housing (4) and a cylinder head (5) of an engine, the sealing ring comprising:
-a first curved member (1) comprising an upper-portion (1a), a lower-portion (1b) and a body portion extending between the upper portion (1a) and the lower portion (1b) ;
-a second curved member (2) formed by extending and bending the upper portion (1a) of the first curved member (1) towards the body portion of said first curved member (1); and
-a third curved member (3) formed by extending and bending the lower portion (1b) of the first curved member (1) towards the body portion of the said first curved member (1), such that, an end (3a) of the third curved member (3) is slidable with an end (2a) of the second curved member (2).

2.The sealing ring as claimed in Claim 1, wherein, a radius R2 defined between a longitudinal axis of the spark plug and the second curved member (2) increases when a force is applied in the direction of the longitudinal axis of said sealing ring.

3. The sealing ring as claimed in Claim 2, wherein, radius R3 defined between the longitudinal axis of the spark plug and the third curved member (3) increases when the force is applied in the direction of the longitudinal axis of said sealing ring.

4. The sealing ring as claimed in Claim 2, wherein, radius R1 defined between the longitudinal axis of the spark plug and the first curved member (1) decreases when the force is applied in the direction of the longitudinal axis of said sealing ring.

5. The sealing ring as claimed in Claim 1, wherein, the second curved member (2) and the third curved member (3) together constitute a stiffness (K) that is equal to a ratio of :
the product of an individual stiffness (K2) of the second curved member and an individual stiffness (K3) of the third curved member; and
the sum of the individual stiffness (K2) of the second curved member and the individual stiffness (K3) of the third curved member.

6. The sealing ring as claimed in Claim 4, wherein the first curved member (1), the second curved member (2) and the third curved member (3) constitute an equivalent stiffness (Keq) that is equal to a sum of the stiffness (K) and the stiffness (K1) of the first curved member.

7. The sealing ring as claimed in Claim 5, wherein the second curved member (2) and the third curved member (3) are equivalent to two springs that are sequentially connected in series.

8. The sealing ring as claimed in Claim 6, wherein the first curved member (1) is equivalent to a single spring, such that the two springs that are sequentially connected in series is in parallel arrangement with the single spring.

9. The sealing ring as claimed in Claim 1, wherein the sealing ring is adapted to be displaced within the groove(6) and wherein the sealing ring is adapted to partially rotate within the groove to enable the sealing ring to snugly fit within the groove.

10. The sealing ring as claimed in Claim 1, wherein the sealing ring is manufactured from a material such as but not limited to zinc plated steel.