FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Dual Amplitude Exciter Shaft Assembly For Vibratory Compactor"
2. APPLICANT:
(a) NAME: Larsen & Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: LARSEN & TOUBRO LIMITED,
L&T House, Ballard Estate, P. O. Box: 278, Mumbai 400 001, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Dual Amplitude Exciter Shaft Assembly For Vibratory Compactor
Field of the invention
The present invention relates generally to vibratory compactors used to compact soil, warm asphalt and other granular base materials applied in road and pathway making, and more particularly, the present invention relates to an dual amplitude exciter shaft assembly of the vibrating compactor.
Background of the invention
Vibratory compactors are widely used in pavement, road and airport runway construction for compaction and ground leveling applications such as compaction of soil, granular sub base, crushed aggregates, asphalt, macadam and the like.
The vibratory compactors are provided with either a single or double drum for rolling with vibrations over the surface to be compacted. The vibratory compactors are self-propelled with the help of a diesel driven internal combustion engine operative!)' connected to pumps that supply pressurized hydraulic fluid to motors to drive roller propulsion and vibration system. In a typical double drum compactor, each roller is rotatingly connected to the machine structural frame and each frame is pivot connected to allow frame articulated steering. The frames support engine, hydraulic pumps, valves and associated hydraulic, diesel tank and other peripheral systems for engine and hydraulics. In case of machines used for the asphalt compaction, the frames also support additional water sprinkling system with a tank which provide fine spray of water over the drum surface during operation so as to avoid asphalt sticking to the surface of the drums. Each drum assembly rotatingly supports an exciter shaft assembly at its center which is operatively connected to a dedicated

hydraulic motor. The exciter shaft assembly typically consists of one or more eccentric masses coaxially arranged in such a manner that the masses add up when rotated in one direction and subtract when rotated in opposite direction. The exciter shaft assembly rotated by the hydraulic motor provides the vibration to the drum assembly which is used in compaction of the surface underneath the drum.
Specifically, US Patent No. 8,206,061 discloses a vibratory mechanism using double angled central shaft. Another US Patent No. 5,618; 133 discloses a vibratory mechanism for creating variable amplitude in compactor machines.
Referring to figures 1-4, a typical exciter shaft assembly (100) for creating two amplitude vibrations used in compactors of the prior art is shown. The exciter shaft assembly (100) includes a long eccentric shaft (1) with a fixed mass (la) disposed at a distance (3) from a revolving center (2). The exciter shaft assembly (100) supports floating/movable masses (5) on both ends housed a inside ring assembly (4). The ring assembly (4) consisting the movable mass (5) is connected to the eccentric shaft by a key (6) arrangement. The axial movement of floating mass/movable mass (5) with the ring assembly (4) is constrained by a retainer ring (9) on one side and by a eccentric shaft shoulder (8) on the other side. The ring assembly (4) contains a stopper pad (7) attached to inner wall thereof by means of welding which makes orientation of the moving masses (5) with respect to the fixed mass (la). The masses, for example the fixed mass (la) and the movable mass (5) add up and produce high amplitude in one direction of rotation of the exciter shaft assembly (100) and subtract and produce low amplitude when rotated in opposite direction. The eccentric shaft assembly (100) having the long eccentric shaft (1) on which a pair of the ring assembly (4) is coaxially mounted is rotatingly supported on a pair of bearings (10) and (II) on either side. The outer races of the bearings (10, 11) are press fitted inside the bearing housing (12) and (13). The bearing housing (12, 13) is connected to the drum vertical supports (14) and (15) by means of plurality of fastener (16) and

(17). The exciter shaft assembly (100) is operatively and rotatingly connected to a hydraulic motor (not shown). The hydraulic motor is operatively connected to hydraulic pump by means of hoses.
Total value of eccentric moment for the summation of the fixed mass (la) and the movable mass (5) contributes for the amplitude and effects the vibration to the drum assembly. The exciter shaft assembly shown in figure. 2 has the fixed mass of 57.9 kg and total moving mass of 8.1 kg. The corresponding eccentricities are 19 mm and 59 mm respectively. The total eccentric moment of the eccentric shaft assembly (100) is 1596 kg-mm. The total mass of the fixed and floating mass is 66 kg and the ratio of eccentric moment to total mass is 24.2. These weights of the fixed mass (la) and the movable mass (5) are very high and requires a huge cost.
Further, the existing exciter shaft assembly requires eccentric machining of long shaft from a round bar stock to create eccentricity of the fixed mass. This imposes huge material and manufacturing cost. Furthermore, the method of fixing of the moving mass ring assembly on to the eccentric shaft requires additional key way milling and fasteners. This increases the direct material and manufacturing cost.
Accordingly, there exist a need to provide an exciter shaft assembly for vibratory compactors which overcomes drawbacks of the prior art.
Objects of the invention
An object of the present invention is to minimize need of eccentric machining of a shaft of an exciter shaft assembly from a round bar stock to create eccentricity.
Another object of the present invention is to create simple and cost effective design for generating vibration of two amplitudes in a compactor machine.

Summary of the invention
Accordingly, the present invention provides a dual amplitude exciter shaft assembly for a vibratory compactor having at least one drum supported on support plates. The exciter shaft assembly comprises a shaft rotatingly supported at a center of the drum and connected to a motor, a stopper pad configured at outer surface of the shaft, end caps affixed to the shaft on both ends thereof, and a covering member covering the shaft thereby forming an annular space between the shaft and the covering member. The covering member is closed by the end caps at both ends of the shaft, a moving mass positioned freely inside the annular space. Further, the dual amplitude exciter shaft assembly includes a fixed mass attached to outer surface of the covering member such that the stopper pad is at 90° to the fixed mass, wherein upon rotating the shaft in clockwise direction, the fixed mass and the movable mass occupy opposite positions thereby creating a smaller amplitude. Further, upon rotating the shaft in counter-clockwise direction, the fixed mass and the floating mass add up creating higher amplitude of vibration.
Brief description of the drawings
Figure 1 shows a sectional view of a vibratory drum of a vibratory compactor of the prior art;
Figure 2 shows an enlarged sectional view of a eccentric shaft assembly of the vibratory drum of Figure 1;
Figure 3 and 4 shows a sectional view of the eccentric shaft assembly of figure 2;

Figure 5 shows a sectional view of a drum assembly, in accordance with the present invention;
Figure 6 shows an enlarged sectional view of an exciter shaft assembly in accordance with the present invention;and
Figure 7 shows a sectional view of the exciter shaft assembly of figure.6
Detailed description of the invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The present invention provides a dual amplitude exciter shaft assembly for a vibratory compactor. The dual amplitude exciter shaft assembly includes a mechanism which is simple and does not need any eccentric machining of a shaft. This is achieved by judicious disposition and rotation of effective fixed mass and floating mass in the exciter shaft assembly so that they produce the required amplitude and vibration forces. The ratio of total eccentric moment to the total mass is maximized to reduce the effective masses which produce the moment.
Referring now to figures 5-7, there is shown an dual amplitude exciter shaft assembly (200) (hereinafter 'the assembly (200)?) for a vibratory compactor, in accordance with the present invention. The vibratory compactor includes a first drum/inner drum (300) configured inside a second drum (400). The first drum/ inner drum (300) is attached to the second drum (400) through support plates (310, 320) by means of welding. Specifically, the first drum (300) is supported on support plates (310, 320). The support plates (310) and (320) includes a

plurality of housing, for example, a housing (330) and a housing (340) supported thereon.
As shown in figure 5, the exciter shaft assembly (200) is supported at the center of the first drum (300). Specifically, the exciter shaft assembly (200) is rotatingly and operatingly connected to a dedicated motor (not shown), for example a dedicated hydraulic motor.
The exciter shaft assembly (200) is supported by a plurality of bearings, for example, a bearing (210) and a bearing (220) at its either end. More specifically, the bearing (210) is mounted inside the housing (330) and the bearing (220) is mounted inside the housing (340).
In an embodiment the housings (330, 340) are connected to the support plates (310, 320) by means of plurality of fasteners (332, 334) respectively. The exciter shaft assembly (200) between the support plates (310, 320) is arranged inside the first drum/inner drum (300). The first drum/inner drum (300) provides the sump for the oil lubricating the bearing (210) and the bearing (220). To supply lubricating oil to the first drum/inner drum (300), the support plate (310) and the first drum/inner drum (300) are connected with a tube (350).
Referring to figures 6 and 7, the exciter shaft assembly (200) is shown. The exciter shaft assembly (200) include a shaft (110), a stopper pad (120). end caps (130), a covering member (140), moving mass (150) and a fixed mass (160).
The shaft (110) is rotatingly supported at center of the first drum/inner drum (300). Further, the stopper pad (120) is attached to the shaft (110). In an embodiment, the stopper pad (120) is attached to the shaft (110) by welding.
The end caps (130) are affixed to the shaft (110) on both ends thereof. In an embodiment, the end caps (130) are press-fitted to the shaft (110) on ends

thereof. The covering member (140) covers the shaft (110) thereby forming an annular space (112) between the shaft (110) and the covering member (140). In an embodiment, the covering member (140) is like a tube structure covering the shaft (110).
The covering member (140) is closed by the end caps (130) at both ends of the shaft (110). Specifically, one end of the covering member (140) is positioned inside step of a end cap (130a) of the end caps (130) and connected by welding. Further, other end of the covering member (140) is positioned inside step end of a end cap (130b) of the end caps (130).
The moving mass/floating mass (150) is placed inside the annular space (112) available between the shaft (110) and the covering (140). In an embodiment, the moving mass/floating mass (150) is made of steel. However, it may be evident to those skilled in the art to use moving mass/floating mass of any heavy metal which produces desired amplitude.
Further, the fixed mass (160) is attached to the outer of the covering member (140) such that the stopper pad (120) is at 90 degrees to the fixed mass (160) when viewed from a side. In an embodiment, the fixed mass (160) is made of steel. However, it may be evident to those skilled in the art to use fixed mass of any heavy metal which produces desired amplitude.
In an embodiment, the present invention has the fixed mass (160) of 13.5 kg and the moving mass (150) of 9.7 kg. The corresponding eccentricities are 82.8 mm and 49.4 mm. Further, the total mass of fixed mass (160) and the floating mass (150) is 23.2 kg and the ratio of eccentric moment to total mass is 68.8.
In an operation, when the shaft (110) is rotated in clockwise direction, the fixed mass (160) and the movable mass (150) occupy opposite positions and creates smaller amplitude. Further, when the shaft (110) is rotated in counter-clockwise

direction, the fixed mass (160) and the movable mass (150) add up and create higher amplitude of vibration.
Advantages of the invention
1. The exciter shaft assembly (200) provides two amplitudes.
2. The exciter shaft assembly (200) has reduced manufacturing cost and simple in construction.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient; but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

We Claim
1. A dual amplitude exciter shaft assembly for a vibratory
compactor having a drum supported on support plates, the exciter shaft assembly
comprising:
a shaft rotatingly supported at a center of the drum and connected to a motor;
a stopper pad configured at outer surface of the shaft;
end caps affixed to the shaft on both ends thereof;
a covering member covering the shaft thereby forming an annular space between the shaft and the covering member, wherein the covering member is closed by the end caps at both ends of the shaft;
a moving mass positioned freely inside the annular space; and
a fixed mass attached to outer surface of the covering member such that the stopper pad is at 90° to the fixed mass.
wherein upon rotating the shaft in clockwise direction, the fixed mass and the movable mass occupy opposite positions thereby creating a smaller amplitude, and upon rotating the shaft in counter-clockwise direction, the fixed mass and the floating mass add up creating higher amplitude of vibration.
2. The dual amplitude exciter shaft assembly as claimed in claim 1.
wherein the exciter shaft assembly is supported inside the drum on either side by
a plurality of bearings mounted inside a plurality of housing.
3. The dual amplitude exciter shaft assembly as claimed in claim],
wherein plurality of housing are connected to the support plates.