Claims:We Claim:
1. A spark plug (100) for an engine, said spark plug (100) adapted to be located onto the head of said engine and comprising at least:
an electrode (102), said electrode 102 housed within an insulator (104);
said insulator (104) enclosed within a shell (106); characterized in that:
said shell (106) adapted to comprise threads of varying length, said length of thread enabling ingress of said spark plug 100 onto said head of said engine .

2. The spark plug 100 of claim 1, wherein said shell 106 is at least one chosen from a combination comprising a metallic shell 106 and a ceramic shell 106.

3. The spark plug 100 of claim 1, wherein heat transfer rate from said engine to said spark plug 100 is in dependence of said length of said thread.
, 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]This invention relates to the field of spark plug.

Background of the invention
[0002]A spark plug is used in a gasoline, CNG, LPG or ethanol engine for enabling combustion of air and fuel mixture in the engine cylinder. The spark plug includes a central electrode, an insulating member which holds the central electrode in an axial hole, a metal shell which surrounds the periphery of the insulating member to hold the insulating member, and a ground electrode which is joined to the metal shell at a proximal end portion which forms a spark gap at a distal end portion with the central electrode. The fuel mixture is ignited by a spark discharge occurring in the spark gap.

[0003]The temperature of the spark plug must neither exceed nor fall below a given range for ensuring combustion of the air and fuel mixture. This means that the spark plug for a hot engine must efficiently dissipate the heat acting on it, in order to remain within the working temperature range. Whereas a spark plug for a cold engine must absorb more heat in order to reach its working temperature. This calls for equilibrium between the heat absorbed and heat dissipated.

Brief description of the accompanying drawing
[0004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[0005] FIG. 1 illustrates a spark plug.

Detailed description of the embodiments
[0006] FIG. 1 illustrates a spark plug 100. The spark plug 100 is adapted to be located onto the head of the engine and comprises at least an electrode 102 that is housed within an insulator 104. The insulator 104 is enclosed within a shell 106. The shell 106 is adapted to comprise threads of varying length, the length of the thread enables ingress of the spark plug 100 onto the head of the engine. In an embodiment the shell 106 is chosen from a combination comprising a metallic shell 106 and a ceramic shell 106. The heat transfer rate from the engine to the spark plug 100 is in dependence of the length of the thread.

[0007]The construction of the spark plug 100 will be explained in further detail. The spark plug 100 disclosed herein is used for enabling combustion of air and fuel mixture in the internal combustion engine. The electrode 102 in the spark plug 100 is used for generating a spark that ignites the air and fuel mixture. The electrode 102 is housed within the insulator 104. The dimensions of the insulator 104 is kept constant. As illustrated in FIG. 1, the shell 106 is adapted to comprise threads of varying length, length L12 being lesser than length L21, and length L3 lesser than both L2 and L1.

[0008]The heat absorption of the insulator 104 depends up on the surface area of insulator 104 nose exposed to the combustion gases. If a larger surface area of insulator 104 nose is exposed to combustion gases more amount of heat will be absorbed by the insulator 104 nose, and this is referred to as higher heat value (hotter spark plug). In case of less surface area of insulator 104 nose exposed to combustion gases, less amount of heat will be absorbed by insulator 104 nose, this is referred to as cold spark plug 100. The surface area of exposure depends upon the length of the threads. For thread length L1, the threads are located all along the length of the shell 106. Hence during mounting of spark plug 100 the ingress of spark plug 100 leading to exposure of electrode 102 is different for thread length L1 as compared to a spark plug 100 with thread length L2. This leads to spark plug 100 comprising different heat absorption and dissipation capabilities.

[0010] By having a shell 106 of varying lengths it is now possible to use spark plug 100 varying applications depending upon the degree of hotness or coldness in the spark plug 100. This enables the spark plug 100 to be used for wide range of applications.

[0010] ‘Adapted’ or ‘arranged’, in the context of the instant disclosure, refers to the technical capability or the technical capacity of a component, in relation to which the term ‘adapted’ or ‘arranged’ is used, to carry out or executed a specified action or actions, upon the requirement of the specified action or actions to be carried out or executed. Moreover, the usage of the term ‘adapted’ or ‘arranged’ here, is in reference with the normal technical capability or technical capacity of the component, imparted by the design or the structure or the composition of the component, and not in reference with any special or extraneous capability or capacity, beyond the scope of the normal technical capability or technical capacity. Therefore there is a need to address this problem.

[0011]It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention in terms of the type of spark plug used. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.