CLIAMS:NO CLAIMS ,TagSPECI:FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005
PROVISIONAL SPECIFICATION
(SEE MEMBER 10 AND RULE 13)
TITLE OF THE INVENTION
“A Load Distributing Member to Increase Bolt Compression Zone”
APPLICANTS:
Name : Mahindra & Mahindra Ltd

Nationality : Indian
Address : Mahindra Research Valley, Mahindra World
City, Plot No. 41/1, Anjur P.O.,
Chengalpattu – 603204,
Kancheepuram Dist, Tamilnadu, India
The following specification describes the nature of the invention:
FIELD OF INVENTION
[001] This invention relates generally to a load distributing member and, more particularly but not exclusively relates to a load distributing member which is used in combination with a bolt to join at least two parts together. This invention is applicable to non-permanent joints of threaded fasteners like bolt & nut, stud etc. It can be implemented in all kinds of industry where bolted flange joints are used between two parts.

BACKGROUND OF INVENTION
[002] Bolted joints are one of the most common elements in construction and machine design, especially used for fastening components together. Many industrial, pressure vessel, automotive and aerospace applications require the transfer of fluid between two components. For example, in tractor skid it is common to transfer lubricating oil between speed housing and rear housing, or in gas turbine compressed air transferred from compressor to combustion chamber. Generally, in order to transfer fluid between two components, both the components are bolted together using threaded fasteners such as bolts, screws, studs and so on. Further, fluid is transferred from one component to another component. However, fluid leakage from joints like bolted joints is a perennial problem in industrial applications.
[003] Normally, each bolt in a bolted joint defines a specific compression zone. While tightening the bolt, a compression zone is developed in the component's flange thereby securing the components together. In a bolted joint, significant importance is given to the compression zone such that the compression zone is available over the entire joint area. However, the compression zone of a bolt within each flange is limited to 25-33 degree (half angle of an imaginary conical frustum). Therefore, the effective compression length on a flange varies from 3D to 5D where D is diameter of the bolt. The bolted joint which does not have compression zone over the entire joint area is subjected to fluid leakage when fluid is transferred across the bolted joint. Therefore, in order to maintain the compression zone over the entire joint area the number of bolts is significantly increased. Further, the increase in number of bolts subsequently increases the machining cost and assembling cost. At present, to address the issue, special gaskets or liquid sealants are used. The sealants spread out over the entire joint area when a minimum clamping pressure is applied, thereby providing a proper sealing against fluid leakage when fluid is transferred across the bolted joint. However, the cost associated with these special gaskets is high thereby making the gaskets and sealants not desirable for practical applications.
[004] Thus, there is a need for a load distributing member which may be readily used with the bolt to increase the compression zone of the bolt. Further, there is a need for a load distributing member that could obviate the above mentioned drawbacks associated with the conventional systems.
OBJECT OF INVENTION
[005] The principal object of this invention is to provide a load distributing member which could be used in combination with a bolt to join two or more parts together.
[006] Another object of the invention is to provide a load distributing member that could increase compression zone of a bolted flange joint.
[007] Yet another object of the invention is to provide a load distributing member that could reduce cost of assembly when compared to conventional system.
[008] These and other objects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF FIGURES
[009] This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0010] Fig. 1 depicts a perspective view of a system having a speed housing and a rear housing which are coupled together by a bolt flange joint according to an embodiment of the present invention;
[0011] Fig. 2 illustrates a detail sketch of a bolt joint incorporating a load distributing member according to an embodiment of the present invention; and
[0012] Fig. 3 illustrates a sketch of the load distributing member according to an embodiment of the present invention.
DESCRIPTION OF INVENTION
[0013] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. For example, it should be noted that while some embodiments are explained with respect to a load distributing member 101 which is used in combination with a bolt 102 for coupling two parts in an automobile, it should be noted that the load distributing member 101 as disclosed in the present invention could also be used for several other purposes by incorporating the subject matter of the invention with little or no modifications. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0014] The invention discussed herein provides a load distributing member 101 which is used in combination with a bolt 102 to provide a tight coupling between two parts. Further the load distributing member 101 according to an embodiment of the present invention provides an increased compression zone of a bolt. In addition, the load distributing member 101 according to an embodiment of the present invention reduces the cost of assembly when compared to the conventional system.
[0015] Traditionally a bolt joint consists of two mating flanges having at least one hole, and at least one threaded fastener like bolt 102 and nut 103 or a stud connecting the flanges. The bolt 102 is passed through the said hole of the mating flanges and is engaged with the nut 103 to form the bolted flange joint. The bolt joint holds the two mating flanges firmly intact to each other. In one embodiment Fig.1 shows a joint of two housing of a tractor. The two housing of the tractor refers to speed housing 104 and rear housing 105. Both the speed housing 104 and the rear housing 105 are provided with flanges F1 and F2 on the adjoining surfaces respectively so that they can be joined easily.
[0016] Conventionally a flat disc washer is used in combination with the bolt 102 and nut 103 for joining the flanges. The washer is mainly used in the bolt joint to distribute the load between the bolt head and nut face. By providing the washer in the bolt joint, the bearing stress is maintained within a predetermined range such that it does not exceed the bearing strength of the joint material. Thus the usage of washer avoids creep which in turn avoids bolt preload loss.
[0017] In recent days flanged fasteners are widely used instead of washers. These flanged fasteners transfer the load within an imaginary conical frustum whose half angle lies in the range of 25-33 degree. In one embodiment increasing the half angle of the imaginary conical frustum increases the compression zone of the bolt.
[0018] In an embodiment, the present invention provides a load distributing member 101 which increases the half angle of the imaginary conical frustum. The aforementioned load distributing member 101 hereafter referred as “conical washer” defines a washer having a conical configuration. The conical washer 101 transfers the load acting on the bolt 102 in the direction perpendicular to its cone angle which in turn leads to increase in the half angle of the imaginary conical frustum. Further, increase in the half angle of the imaginary conical frustum, increases the compression zone of the bolt.
[0019] In one embodiment, the two housings are joined using the bolted joint as shown in fig. 2. The Flange F1of the speed housing 104 having a thickness t1 is pressed against the flange F2 of the rear housing 105 having a thickness t2. The flange F1 is provided with at least one hole for passing a hexagonal bolt. Further, the flange F2 is provided with at least one hole for passing said bolt or one tapped hole for engaging a stud with the tapped hole. However, it is also within the scope of invention that the bolt could be of any other shape without otherwise deterring the intended function of the conical washer 101 as could be deduced from this description. The hexagonal bolt 102 engages with a nut 103 such that both the flanges F1 and the flange F2 are held firmly together. Further, aforementioned conical washer 101 is provided between the bolt head and the flange F1 such that the conical washer 101 transfers the load acting on the bolt 102 in the direction perpendicular to its cone angle which in turn leads to increase in the half angle of the imaginary conical frustum.
[0020] In one embodiment, the conical washer 101 is configured with a height ht, an angle ?, an inner radius r1 and an outer radius r2 respectively as shown in figs. 2-3. A pocket is defined in the flange F1 such that the pocket could accommodate the conical washer 101. The dimensions of the pocket are configured to be same as that of the conical washer 101. In one embodiment, depth of the pocket is configured to be larger than that of contact length of the conical washer 101. A gap g is defined in the flange which ensures that there is a minimum amount of load transfer in the bolt axis direction and the remaining of load acting on the bolt 102 is transferred away from the bolt. Thus resulting in increased compression zone.
[0021] In an embodiment the height ht of the conical washer 101 is configured to be greater than 1mm, however the recommended value for the conical washer 101 height ht ranges between 2-8 mm. In another embodiment the conical washer 101 angle ? is configured to be 10o which has been optimized using finite element analysis, however the value for ? can be between 5o to 85o. In one embodiment the gap g can vary from 0.5 mm to t1 - ht, however recommended range of the gap is between 1 to 3 mm. In another embodiment the inner radius r1 equals to the radius of bolt hole and the outer radius r2 equals to the radius of standard used washer or flanged bolt which is usually 2* r1. In one embodiment dimension t at the pocket varies from 0 to t1-ht-g, however the recommended value for t is 5 to 10mm.
[0022] In one embodiment the conical shaped washer can be manufactured from the flat disc washer by various manufacturing processes like lathe machining, forging, etc. Also, the corresponding shape of the pocket in the flange F1 can be provided by spot machining using a tapered cutter. In another embodiment the material of the conical washer 101 can be same as that of the standard flat disc washer, for example, hardened steel. A close tolerance is maintained between the mating conical face angle such that the inclined contact area is sufficient enough to transfer the load in all direction to the farthest position of the bolt.
[0023] In an alternative embodiment the conical washer 101 can be integrated with the bolt. Instead of manufacturing the conical washer 101 as a separate component and then assembling it with bolt, the conical washer 101 can be integrated with the bolt 102 to ease the assembly. Thus it avoids the inventory on manufacturing a separate conical washer 101. Further integration of the conical washer 101 with bolt 102 saves assembling time.
[0024] In yet another embodiment, more than one conical washer could be provided to couple the housings, such that each of flange F1 and F2 includes a conical washer 101. It should be noted that the aforementioned configuration of conical washer 101is provided for the ease of understanding of the embodiments of the invention. However, certain embodiments may have a different configuration of the components of the conical washer 101 and certain other embodiments may exclude certain components of the conical washer 101. Therefore, such embodiments and any modification by addition or exclusion of certain components of conical washer 101 and without otherwise deterring the intended function of the conical washer 101 as is apparent from this description and drawings are also within the scope of this invention.
[0025] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Referral numerals:
101 Conical washer, load distributing member
102 Bolt
103 Nut
104 Speed housing
105 Rear housing

ABSTRACT
A load distributing member 101 in combination with a bolt 102 to join at least two parts together is disclosed. The load distributing member 101 disclosed is washer which is configured to be conical in shape. The conical washer 101 facilitates in increasing the half angle of an imaginary conical frustrum. Further increase in the half angle of the imaginary conical frustum, increases the compression zone of the bolt.
Fig. 2

Date: 31st January 2013 Signature

Dr. Kalyan Chakravarthy
Patent Agent