Claims:We Claim:
1. A supercharger assembly (10, 20), comprising:
a shaft (105); and
a lobe (107) disposed concentric to the shaft (105);
characterized in that:
a circumferential projection (110) disposed on the shaft (105); and
a surface (120) on the lobe (107) disposed against the circumferential projection (110) of the shaft (105) to enable being rotated by the shaft (105).

2. The supercharger (10, 20) assembly as claimed in claim 1, the circumferential projection (110) being a step.

3. The supercharger assembly (10, 20) as claimed in claim 1, the circumferential projection (110) being a taper extending away from an axis (122) of the shaft (105).

4. The supercharger (10, 20) assembly as claimed in claim 1, further comprising:
a retainer (125) fastened to an end (130) of the shaft (105), a length of a retaining portion (135) of the retainer (125) being greater than a diameter of the shaft (105) to contact and force the lobe (107) axially against the circumferential projection (110) of the shaft (105).

5. The supercharger assembly (10, 20) as claimed in claim 4, the retainer (125) being a screw received by the shaft (105) along the axis (122) of the shaft (105).

6. The supercharger assembly (10, 20) as claimed in claim 2, the lobe (107) comprising a section (145) extending from the step of the shaft (105) and away from the retainer (125), the section (145) of the lobe (107) concentric to the step of the shaft (105).
7. The supercharger assembly (10, 20) as claimed in claim 6, the section (145) of the lobe (107) being in contact with the step of the shaft (105).

8. A lobe (107) for the supercharger assembly (10, 20), the lobe (107) arranged to be disposed concentric to a shaft (105) having a circumferential projection (110), the lobe (107) comprising:
a surface (120) arranged to be disposed against the circumferential projection (110) of the shaft (105) to enable being rotated by the shaft (105).

9. The lobe (107) for the supercharger (10, 20) as claimed in claim 8, the surface (120) being at an angle to an axis (122) of the lobe (107).

10. A supercharger assembly (30), comprising:
a shaft (105); and
a lobe (107) disposed concentric to the shaft (105);
characterized in that:
threads (160) disposed externally on the shaft (105);
threads (165) disposed internally in the lobe (107), the threads (165) disposed internally in the lobe (107) fastened to the threads (160) disposed externally on the shaft (105). , Description:FIELD OF THE INVENTION
[0001] This invention relates to a supercharger assembly and a lobe for the supercharger assembly.

BACKGROUND OF THE INVENTION
[0002] Superchargers comprise a shaft and a lobe, among other components. The lobes are mounted on the shaft and rotated by the rotation of the shaft. This is common for both the drive shaft as well as the driven shaft. An effective contact between the shaft and the lobe provides for efficient power transfer from the shaft to the lobe. US4828467 discloses a roots-type blower or supercharger having a pair of meshed, lobed rotors press-fitted onto a pair of shafts. Each of the rotors includes a first bore portion, and a second bore portion, while the shaft defines a first shaft portion, press fit into the first bore portion and a second shaft portion press fit into the second bore portion.

BRIEF DESCRIPTION OF DRAWINGS
[0003] Embodiments of this disclosure are explained in principle below with reference to the drawings. The drawings are:
[0004] FIGURE 1 illustrates a first arrangement of a supercharger assembly;
[0005] FIGURE 2 illustrates a second arrangement of the supercharger assembly; and
[0006] FIGURE 3 illustrates a third arrangement of the supercharger assembly.

DETAILED DESCRIPTION
[0007] FIGURE 1 illustrates a first arrangement of a supercharger assembly 10. The supercharger assembly 10 comprises a shaft 105 and a lobe 107 disposed concentric to the shaft 105. The supercharger assembly 10 is characterized in that, there is a circumferential projection 110 disposed on the shaft 105 and a surface 120 on the lobe 107 disposed against the circumferential projection 110 of the shaft 105 to enable being rotated by the shaft 105. As illustrated in FIGURE 1, the circumferential projection 110 is a step on the shaft 105. In other words, the shaft 105 in the supercharger assembly 10 is a stepped shaft, with the step having a diameter greater than a diameter of the shaft. The step in the shaft 105 in the first arrangement is a single level step with a circumferential surface of the step parallel to a circumferential surface of the shaft 105. The surface 120 of the lobe 107 which is disposed against the step of the shaft 105 is perpendicular to an axis 122 of the shaft 105.
[0008] FIGURE 2 illustrates a second arrangement of the supercharger assembly. The supercharger assembly 20 in the second arrangement also comprises the shaft 105 and the lobe 107 disposed concentric to the shaft 105. The second arrangement 20 is also characterized in that, there is the circumferential projection 110 disposed of the shaft 105 and the surface 120 on the lobe 107 disposed against the circumferential projection 110 of the shaft 105 to enable being rotated by the shaft 105. In the second arrangement, the circumferential projection 110 is a taper extending away from the axis 122 of the shaft 105. The taper is a self-locking type, which is an industrial standard understood by a person of ordinary skill in the art and the angle of the taper also conforms to the above standard. In other words, the taper extends outwardly from the circumferential surface of the shaft 105. Consequently, the taper is not constant diametrically and a diameter of the taper increases with the extension of the taper from the circumferential surface of the shaft 105. The surface 120 of the lobe 107 is disposed against the taper.
[0009] Both the supercharger assembly 10 and the supercharger assembly 20 further comprise a retainer 125 fastened to an end 130 of the shaft 105. A length of a retaining portion 135 of the retainer 125 is greater than a diameter of the shaft to contact and force the lobe 107 axially against the circumferential projection 110 of the shaft 105. To elaborate, the retaining portion 135 is orientated perpendicular to the axis 122 of the shaft 105 and thereby the length of the retaining portion 135 is also perpendicular to the axis 122 of the shaft 105. The retainer 125 can be any fastener such as a screw or can be anything else that can be fixed onto the shaft 105 and leverages the shaft 105 to force axially the lobe 107. In the supercharger assembly 10 and the supercharger assembly 20 shown as examples, the retainer 125 is received by the shaft along the axis 122 of the shaft 105. The objective of the axial forcing of the lobe 107 towards the circumferential projection 110 will be explained hereinafter.
[00010] In the supercharger assembly 10, the lobe 107 comprises a section 145 extending from the step of the shaft 105 and away from the retainer 125, the section 145 being concentric to the step of the shaft 105. To elaborate, an inner diameter at the section 145 of the lobe 107 is greater than an inner diameter of the lobe 107 at other portions to accommodate the circumferential projection 110 or the step in the first arrangement. The section 145 of the lobe 107 can also be in contact with the step of the shaft 105.
[00011] The mounting structure described above is used for all the lobes in the supercharger assembly 10 or the supercharger assembly 20. The supercharger assembly 10 and the supercharger assembly 20 further comprise a cover plate 150 on a side 155 of the assembly having the retainer 125. The cover plate 150 can be fitted to the supercharger assembly 10 or the supercharger assembly 20 using fasteners.
[00012] The step is positioned away from the retainer 125 and the end 130 of the shaft 105 in the first arrangement, as illustrated in FIGURE 1. The step can be positioned proximal to the retainer 125 also as well.
[00013] The surface 120 of the lobe 107 disposed against the circumferential projection 110 in both the supercharger assembly 10 and the supercharger assembly 20 provides an interface for or a mechanism of transferring power from the shaft 105 to the lobe 107 to enable rotation of the lobe 107. So, as the shaft 105 rotates, the lobe 107 is rotated along with the shaft 105.
[00014] The retainer 125 by virtue of being fastened to the shaft 105 and axially forcing the lobe 107 against the circumferential projection 110 provides the advantage of facilitating a better contact between the surface 120 and the circumferential projection 110, thereby improving the transfer of power from the shaft 105 to the lobe 107. As illustrated in FIGURE 1 and FIGURE 2, the other advantage provided by the retainer 125 is that the retainer 125 contains or retains the lobe 107 between the retaining portion 135 of the retainer 125 and the circumferential projection 110 of the shaft 105, so that as the shaft 105 rotates, the retainer 125 and the lobe 107 are also rotated along with the shaft 105. Another advantage provided by the retainer 125 is the easy assembly and disassembly of the lobe 107 from the shaft 105. For disassembly of the lobe 107 from the shaft 105, the retainer 125 is to be unfastened or removed from the shaft 105 and the lobe 107 is to be pulled out. For assembly, the lobe 107 is to be mounted over the shaft 105 and then fixed in place with the fastening of the retainer 125.
[00015] The advantage of having the section 145 of the lobe 107 in contact with the circumferential surface of the step of the shaft 105 is that, there is an improved or increased contact between the shaft 105 and the lobe 107, which provides a mechanism for improved power transfer from the shaft 105 to the lobe 107.
[00016] The cover plate 150 on the side 155 of the supercharger assembly 10 or supercharger assembly 20 covers the end 130 of the shaft 105. The cover plate 150 can be removed and fitted easily as they are fastened to the side 155 by fasteners. The easy fitting and removal of the cover plate 150 facilitates improved assembly and disassembly of the supercharger assembly 10 or supercharger assembly 20.
[00017] Considered independently, the lobe 107 for the supercharger assembly 10 and the supercharger assembly 20, is arranged to be disposed concentric to the shaft 105 having the circumferential projection 110, wherein the lobe 107 comprises the surface 120 arranged to be disposed against the circumferential projection 110 of the shaft 105 to enable being rotated by the shaft 105. The working principle of the components of the lobe 107 above has been described earlier.
[00018] The surface 120 of the lobe 107 is at an angle to an axis (not shown in FIGURES) of the lobe 107. The axis of the lobe can be the same as the axis 122 of the shaft 105 or parallel to the axis 122 of the shaft 105. In the case of the lobe 107 for the supercharger assembly 10, the surface 120 of the lobe 107 is perpendicular or at an angle of 90° to the axis of the lobe 107. In the case of the lobe 107 for the supercharger assembly 20, the surface 120 of the lobe 107 can be at an acute angle to the axis of the lobe 107.
[00019] FIGURE 3 illustrates a third arrangement of the supercharger assembly. The supercharger assembly 30 in the third arrangement comprises the shaft 105 and the lobe 107 disposed concentric to the shaft 105. The supercharger assembly 30 is characterized in that threads 160 are disposed externally on the shaft 105 and threads 165 are disposed internally in the lobe 107, wherein the threads 165 in the lobe 107 are fastened to the threads 160 on the shaft 105. For the purposes of explanation, the threads 160 disposed externally on the shaft are referred to as external threads 160 or external threaded portion 160 and the threads 165 disposed internally in the lobe 107 are referred to as internal threads 165 or internal threaded portion 165. As illustrated in FIGURE 3, the external threaded portion 160 is disposed circumferentially on a portion of the shaft that is away from an end 130 of the shaft 105. Alternately, the threaded portion 160 can be disposed on other portions of the shaft 105 as well. The internal threaded portion 165 is disposed on the internal diametrical portion of the lobe 107, as the lobe 107 is a hallow cylinder having an inner diameter.
[00020] The lobe 107 is screwed onto the shaft 105 such that the internal threaded portion 165 is fastened to the external threaded portion 160 of the shaft. The fastening of the internal threaded portion 165 and the external threaded portion 160 keeps the shaft 105 and the lobe 107 coupled or fastened and thereby results in the rotation of the lobe 107 along with the shaft 105. The advantage provided by the third arrangement is the easy assembly and disassembly of the lobe 107 from the shaft 105 and also the improved fastening of the shaft 105 and the lobe 107. The third arrangement also comprises a cover plate 150 on the side 155 of the supercharger assembly 30. The function and the advantages provided by the cover plate 150 as described with respect to the supercharger assembly 10 and the supercharger assembly 20 is applicable to the supercharger assembly 30.
[00021] The first arrangement, the second arrangement and the third arrangement can be generally applied to superchargers, which are suitable for the above described mounting of the lobe over the shaft.
[00022] Each of FIGURE 1, FIGURE 2 and FIGURE 3 illustrate two sets of shaft and lobe. The numerals have been marked only for one set of shaft and lobe. The numerals equally apply for the unmarked set of shaft and lobe in each of the above figures. Similarly, the description also refers to one set of shaft and lobe. It is to be noted that the description of the structure and the working principle equally applies to the unmarked set of shaft and lobe as well.
[00023] It is to be understood that the foregoing description is intended to be purely illustrative of the principles of the disclosed techniques, rather than exhaustive thereof, and that changes and variations will be apparent to those skilled in the art, and that the present invention is not intended to be limited other than as expressly set forth in the following claims.