FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
PROVISIONAL / COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION :
'A Novel Mounting Arrangement for Vibration Isolation of Rotating Machines Coupled With Reciprocating Machines'
2. APPLICANT:
(a) NAME : Larsen & Toubro Ltd
(b) NATIONALITY : An Indian Company registered under the
Provisions of the Companies Act, 1956
(c) ADDRESS : North Block 1, 6th Floor, Gate No. 1
Powai Campus (W), Saki Vihar Road
MUMBAI-400072
Maharashtra State, INDIA

PROVISIONAL
The following specification describes the
invention.


Title of invention
A novel mounting arrangement for vibration isolation of rotating machines coupled with reciprocating machines
Field of invention
The present invention relates to vibration isolation of rotating machines. More
particularly it relates with vibration isolation of rotating machines coupled with reciprocating machines over wide frequency range.
Prior art and its deficiencies
Rotating machines coupled with reciprocating machines are very common in many industrial applications. Rotating machines coupled with reciprocating machines need to be isolated over wide frequency range so that other machines running in close proximity may not get effected. Vibration isolation generally refers to the means used to reduce the transmittance of vibration of one body to another. In rotating machines coupled with the reciprocating machines, mechanical vibration is generated due to unbalance of rotating mass, unbalance of reciprocating mass, misalignment etc. To reduce this mechanical vibration, a stack of disc spring is proposed. The result is an attenuation of vibration generated by the machine that would otherwise be transmitted to the sole plate of machine.
The conventional method of vibration isolation is to provide insulating plates between machine and foundation. As shown in Fig 1, pump coupled with motor (not shown in the figure) is mounted rigidly on pump-motor bracket (3). The pump-motor bracket (3) vibrates due to excitation by operating pump and motor. The pump motor bracket (4) is mounted on sole plate(4) with a bolt (1). Insulating disc (6) is provided between pump motor bracket (3) and sole plate (4) to isolate vibration from pump motor bracket (3) to sole plate (4). Similarly, insulating disc (5) is provided between washer (2) and pump motor bracket (3) to isolate vibration from pump motor bracket (3) to bolt (1). Thus, mechanical vibration is isolated from pump motor bracket (3) to sole plate (4). Insulating pads are made of elastomers. Such isolators are effective but very limited by a maximum allowable static deflection and by inherent material characteristics. Isolator

stiffness increases with increasing frequencies consequently, such isolators are not efficient over a wide frequency range. Moreover, performance of elastomers depends on amplitude of vibration, therefore if at any frequency amplitude of vibration increases, isolation efficiency reduces. Environmental conditions like temperature and humidity also alters the performance of elastomers.
Object of the present invention:
The object of the present invention is to provide an isolator mount that is able to isolate a wide frequency range for varying load conditions.
Description of the figures
Figure 1 is a diagrammatic representation of the prior art
Figure 2 is a diagrammatic representation of the present invention
Figure 3 is a graphic representation of comparison between the prior art and the present
invention.
Summary of the present invention
In rotating machines coupled with the reciprocating machines, mechanical vibration is generated due to unbalance of rotating mass, unbalance of reciprocating mass, misalignment etc. To reduce this mechanical vibration, a stack of disc spring is proposed. The result is an attenuation of vibration generated by the machine that would otherwise be transmitted to the sole plate of the machine.
In the present invention, the frequency ratio is increased (say 10 times natural frequency) many other resonance peaks are found at higher frequency ratio. This limits the frequency range for which an isolator can be used. The frequency range is increased by a unique combination of disc spring as compared to the rubber pad. Performance of both the isolators is shown in Figure 1. It is clear from the Figure 1 that rubber pad isolates vibration from 180 Hz to 440 Hz ,480 Hz to 1120 Hz and then 1240 Hz to 2000 Hz. In the rubber pad 2 resonant peaks are present at higher frequency ratio. When frequency ratio is around 4 and when frequency ratio is around 10. Whereas, our invention is

isolating vibration from 60 Hz to 2000 Hz. There are no resonant frequency present after 60 Hz. Figure 3 indicates the effectiveness of our invention (a unique combination of the disc springs).
Damping is useful at resonance. It reduces the amplification factor ( Q factor) at resonance. If damping is increased, amplification at resonance gets reduced. But, damping reduces the transmissibility at higher frequencies, therefore, undesirable if higher isolation efficiency is required at higher frequencies. In the present invention damping is present as Coulomb damping and internal friction damping which is sufficient to keep the Q factor maximum up to 4.
Description of the present invention
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention as described bellow in the preferred embodiment. This invention is illustrated in the accompanying drawings, through out which like reference letters indicate corresponding parts in the various figures.
The present invention proposes to address the vibration transmitted by a motor coupled with reciprocating pump or equivalent to the sole plate, with stack of disc springs. The invention concerns with vibration isolation over wide frequency range. Fig. 2 shows the mounting arrangement of disc springs. Pump coupled with motor (not shown in the figure) is mounted rigidly on pump-motor bracket (3). The pump-motor bracket (3) vibrates due to excitation by operating pump and motor. The pump motor bracket (4) is mounted on sole plate(4) with a bolt (1). A stack of disc springs (8) is provided between pump motor bracket (3) and sole plate (4) to isolate vibration from pump motor bracket (3) to sole plate (4). Similarly, another stack of disc springs (7) is provided between washer (2) and pump motor bracket (3) to isolate vibration from pump motor bracket (3) to bolt (1). Thus, mechanical vibration is isolated from pump motor bracket (3) to sole plate (4). The number of disc springs, their dimensions, their stacking arrangement and preload are adjusted such that the isolation over broad frequency range is achieved. The present invention is capable of isolating vibration isolation over desired frequency range by different combination of disc springs. The stiffness of the disc spring stack can be

customized as per the requirement. A softening spring arrangement can be utilized for
good isolation over the wide frequency range. Effect of temperature and humidity is
negligible.
The present invention isolates vibration from 60 Hz to 2000 Hz. There are no resonant
frequencies present after 60 Hz. Figure 3 indicates the effectiveness of the present
invention (a unique combination of the disc springs).
Advantages of the invention
The present invention is able to isolate vibrations for a wide range of frequencies.
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment.
Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or matter.
The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention; which is defined by the scope of the following claims.


Dated this 4th day of July 2009