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 before installing on the spark plug.

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. This disclosed sealing ring incorporates taking advantage of the spring stiffness in a parallel arrangement, thereby achieving higher stiffness.
[0013] A curved member of the sealing ring is parallel to an inclined member on the outer edge of the sealing ring, both acting as spring elements with spring stiffnesses of K1 and K2 respectively. Both act as two parallel springs such that the equivalent stiffness of this spring system adds up, wherein, Keq = K1 + K2.
[0014] The sealing ring is installed such that a radius R1 defined between a longitudinal axis of the spark plug and the curved member reduces on application of compressive load during assembly. The sealing ring gets locked in the spark plug groove such that it possess a rotational degree of freedom and limited translation along the spark plug 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.
[0015] The radius R2 defined between the longitudinal axis of the spark plug and the outermost edge of the inclined member is such that it increases when compressive load is applied it.
[0016] In addition to this, there is a deformation of a pre-determined distance which is allowed during manufacture of the ring which ensures easy assembly of the sealing ring on the spark plug with lower force application. Once this spark plug and ring are installed on the engine cylinder it acts as springs in parallel and provides higher stiffness and ensures superior leak tightness. The shape of the sealing ring also allows higher angle of rotation while torquing the ring to the spark plug.

[0017] 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.

[0018] Referring to Figure (1), the same depicts a sealing ring of a spark plug. The sealing ring (10) is secured within a groove defined between a spark plug housing(4) and a cylinder head (5) of an engine. The sealing ring comprises a curved member (1), an elongated member (2) and an inclined member (3). The curved member (1) comprises an upper-end (1a), a lower-end (1b), and a body portion extending between the upper-end (1a) and the lower-end (1b).

[0019] The elongated member (2) extends from the upper end (1a) of said curved member. The inclined member (3) is secured to an end of the curved member (1) at its lower end (1b) and to an end of the elongated member (2) at its opposite second end. The inclined member further comprises a first inclined member (3a) and a second inclined member (3b). The first inclined member (3a) extends from the lower end (1b) of the curved member (1) towards the elongated member (2) at a pre-defined angle of inclination with reference to a horizontal axis.

[0020] The second inclined member (3b) extends from the elongated member (2) and is positioned against the first inclined member(3a) such that said first inclined member (3a) abuts against the second inclined member (3b) and is slidable within said second inclined member (3b).

[0021] The angle of inclination of the first inclined member (3a) may be same as the angle of inclination of the second inclined member (3b) to ensure a smooth slidable fit between said first inclined member (3a) and said second inclined member (3b).

[0022] The sealing ring is an integrally formed member that is secured within the groove defined between the spark plug housing and the cylinder head of the engine. An inner radius R1 defined between a longitudinal axis (7) of the spark plug and the curved member (3) of the sealing ring decreases when a force is applied in the direction of the longitudinal axis. An outer radius R2 defined between the longitudinal axis of the spark plug and the inclined member of the sealing ring increases when a force is applied in the direction of the longitudinal axis.

[0023] The curved member (1) and the inclined member (3) together constitute a stiffness that is equal to an arithmetic sum of an individual stiffness of the curved member (1) and an individual stiffness of the inclined member (3). The sealing ring is adapted to translate within the groove and wherein the sealing ring is adapted to partially rotate within the groove to enable the sealing ring to snugly fit within the groove. In an embodiment, the sealing ring is manufactured from a material such as but not limited to zinc plated steel.

[0024] The disclosed sealing ring thus allows superior leak tightness and utilizes higher stiffness from spring system in parallel. It further allows higher angle of rotation during torquing of the sealing ring.

[0025] Referring to Figure 2, the same depicts the sealing ring before installing on the the spark plug. A pre-determined gap (x) between the first inclined member (3a) and the second inclined member (3b) is allowed during manufacture of the ring. This gap ensures easy assembly of the sealing ring on the spark plug with use of less force. Once this spark plug with the sealing ring is installed on the engine cylinder, this gap is eliminated as the first inclined member slidably abuts within the second inclined member. The sealing ring then acts as two parallel springs as mentioned above.

[0026] 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 defined between a spark plug housing (4) and a cylinder head (3) of an engine, the sealing ring comprising:
- a curved member (1) comprising an upper-end (1a), a lower-end (1b), and a body portion extending between the upper-end (1a) and the lower-end (1b);
- an elongated member (2) extending from the upper end (1a) of said curved member;
-an inclined member (3) secured to an end of the curved member (1) at its lower end (1b) and to an end of the elongated member (2) at its opposite second end, said inclined member (3) further comprising:
a first inclined member (3a) extending from the lower end (1b) of the curved member (1) towards the elongated member (2) at a pre-defined angle of inclination with reference to a horizontal axis; and
-a second inclined member (3b) extending from the elongated member (2) and positioned against the first inclined member(3a) such that said first inclined member (3a) abuts against the second inclined member (3b) and is slidable within said second inclined member (3b).

2. The sealing ring as claimed in Claim 1, wherein the angle of inclination of the first inclined member (3a) is same as the angle of inclination of the second inclined member (3b) to ensure a smooth slidable fit between said first inclined member (3a) and said second inclined member (3b).

3. The sealing ring as claimed in Claim 1, wherein the sealing ring for the spark plug is an integrally formed member that is secured within the groove defined between the spark plug housing and the cylinder head of the engine.

4. The sealing ring as claimed in Claim 1, wherein an inner radius R1 defined between a longitudinal axis of the spark plug and the curved member (3) of the sealing ring decreases when a force is applied in the direction of the longitudinal axis.

5. The sealing ring as claimed in Claim 1, wherein, an outer radius R2 defined between the longitudinal axis of the spark plug and the inclined member of the sealing ring increases when a force is applied in the direction of the longitudinal axis.

6. The sealing ring as claimed in Claim 1, wherein, the curved member (1) and the inclined member (3) together constitute a stiffness that is equal to an arithmetic sum of an individual stiffness of the curved member (1) and an individual stiffness of the inclined member (3).

7. The sealing ring as claimed in Claim 1, wherein the sealing ring is adapted to translate within the groove and wherein the sealing ring is adapted to partially rotate within the groove to enable the sealing ring to snugly fit within the groove.

8. 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.