The present invention relates to a vibration isolation system or damping system. More particularly, the invention provides a dual natural frequency vibration isolator capable of isolating and damping the vibration of machines/equipment.
BACKGROUND OF THE INVENTION
In certain types of equipment it is highly desirable to provide isolation from vibrations produced through operation of the equipment. In certain operations and applications, because of arising motions, accelerations and vibrations, it is necessary that an arrangement is able to provide damping/isolation of the arising vibrations, preferably in multiple axes. In order to provide the isolation, the mounting arrangement in such operations and applications thus includes spring damping elements forming a multi-axis damping system for mounting the payload in a spring-damped manner relative to a support structure.
It has been known that an effective way of isolating a body from a mass vibrating a substantially constant frequency is to spring couple the vibrating mass to the body and to provide an auxiliary mass arranged so that inertial forces generated by vibration-induced displacement of the mass act on the body to substantially cancel the constant frequency vibratory forces transmitted through the coupling spring.
For instance, in certain machines/equipment/devices which are very precise such as all types of measuring and testing equipment and metrology machines/equipments. They have dynamic behavior, motion and acceleration during their own operation and they need to be isolated from the vibrations/shocks coming from external sources. Further, certain production machines which have high dynamic behavior such as power presses, centrifuges etc. They have dynamic behavior, motion and acceleration during their own

operation and they need to be isolated from transmitting vibrations to the nearby machines, structures, humans and the building.
Traditionally, spring mounts with combination of low natural frequency value and high natural frequency value are primarily used for vibration absorption in a wide range of building and industrial applications where low excitation frequency vibration control is required. A single coil spring or multiple springs combined with rubber elements, at the base, is applied to increase the vibration isolation efficiency in high frequencies.
In U.S. Pat. No. 3,606,233 a hybrid device, combining both passive and active isolation apparatus for producing isolation over a prescribed frequency range of the generated vibrations, while permitting the mass to be rigidly coupled to the source for frequencies below the isolation range is disclosed. The passive system contributes stiffness at low frequencies and isolation at high frequencies, while the active system is operable only in a narrow intermediate frequency range to override the resonance associated with the passive system. However, it has been found that the known arrangement of the damping system is combination of active and passive vibration isolation thus adds up to dependency and complexity to the system. Therefore, to simply fulfill the multi-axis spring damping requirements, the known mounting system is more complicated and costly.
In Patent No. CN 206290636 a variable load damper is disclosed capable for variable load demand and the damping spring isolator, more conventional fixed load isolator, the isolator spring design according to the frequency and weight of the device. However, it has been found that the known arrangement of the damping system is combination of dual spring structure with variable natural frequency for varying load. Therefore, to simply fulfill the multi-axis spring damping requirements, the known mounting system is more complicated and costly.

Therefore, as we can deduce from the current state of art that, there is a need for a vibration isolator in which both low as well as high natural frequency isolators can be integrated as single unit keeping the assembly simple and cost effective.
OBJECT OF THE INVENTION
The main object of the invention is to provide dual natural frequency vibration isolation or damping system.
Another main object of the present invention is to provide a vibration isolator to isolate the weight of a machine in a defined ratio and damp the vibration of isolated percentage of weight of the machine separately.
Yet another object of the invention is to provide a dual natural frequency vibration isolator having a plurality of springs to damp both low and high natural frequency vibration.
Yet another object of the invention is to provide a dual natural frequency vibration isolator having at least one rubber support of an elastomer material acting as a load bearer to reduce dynamic movement.
Yet another object of the present invention is to provide a dual natural frequency vibration isolator having at least one rubber support to damp the high frequency vibration of the machine.
Still another object of the present invention is to provide a simple and cost effective dual frequency vibration isolator to reduce vibrations from external surroundings and reduces the shaking of the machine.
SUMMARY OF THE INVENTION
The present invention aims to provide a dual natural frequency vibration isolation system that overcomes the drawbacks of the prior arts and capable of efficiently

and effectively isolate/damp the vibration using combination of percent of weight of the machine supported by a plurality of springs and rubber supports.
In a main embodiment, the present invention provides a dual natural frequency vibration isolator comprising an upper housing plate, a lower housing plate, at least one rubber support, a plurality of anti-slip pads and a plurality of springs. The upper housing plate is secured in the rubber support and the rubber support is fixed around the lower housing plate to form a casing. The plurality of anti-slip pads is mounted over the upper housing plate and below the lower housing plate to prevent slips and trips of a machine. The plurality of springs is secured in a cavity of lower housing plate to reduce the vibration of the machine by tuning external frequencies. The plurality of springs and rubber supports forms a sandwich between the upper and lower housing plate. The dual natural frequency vibration isolator damps both low and high natural frequency vibrations. It isolates the weight of a machine in a defined ratio and damps the vibration of isolated percentage of weight of the machine separately by using the plurality of springs and the rubber supports.
In another embodiment, the present invention provides an upper housing plate made up of material but not limited to carbon steel, stainless steel etc. The anti-slip pads are made up of material but not limited to elastomer, rubber, neoprene, etc. to prevent slips and trips of the machine. The plurality of anti-slip pads reduces the machine-borne noise to ensure optimum deflection and level consistency both under static and under dynamic loading. Further, the lower housing plate has cavity to uniformly secure the plurality of springs to facilitate damping of low natural frequency as well as high natural frequency vibration.
In an another embodiment, the present invention provides the rubber supports made up of material but not limited to elastomeric material to isolate a percentage of weight in a defined ratio and damp the high natural frequency vibration of the isolated weight of the machine. The plurality of rubber supports is sandwiched between the upper housing plate and the lower housing plate and helps in holding the overall assembly of a dual natural frequency vibration isolator.

Yet in another embodiment, the present invention provides a dual natural frequency vibration isolator wherein the isolation efficiency of an isolator is improved by supporting a combination of percentage of weight in a defined ratio by a plurality of springs and rubber supports. The overall isolation efficiency is defined by the combination of fraction of weight of machine supported by each natural frequency spring. The defined ratio is determined by measuring the tensile/compressive strength of springs and rubber supports.
In still another embodiment, the present invention provides a dual natural frequency vibration isolator in which the plurality of springs reduces the vibrations coming from the external surroundings from going into the machine and rubber supports reduces the machine from shaking due to inherent high dynamic operation of the machine.
BRIEF DESCRIPTION OF THE DRAWING
The object of the invention may be understood in more details and more particularly description of the invention briefly summarized above by reference to certain embodiments thereof which are illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the appended drawings illustrate preferred embodiments of the invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective equivalent embodiments.
Figure 1 is the exploded perspective view of a dual natural frequency vibration isolator/damper in accordance with an embodiment of the present invention.
Figure 2 is the perspective view of a dual natural frequency vibration isolator/damper in accordance with an embodiment of the present invention.
Figure 3 is the top view of a dual natural frequency vibration isolator/damper in accordance with an embodiment of the present invention.

Figure 4(a) and 4(b) shows the vibration level in X-axis and Z-axis on machine bed in accordance with an embodiment of the present invention.
Figure 5(a) and 5(b) shows the vibration level in X-axis and Z-axis on the floor near machine in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which a preferred embodiment of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough, and will fully convey the scope of the invention to those skilled in the art.
The present invention aims to provide a dual natural frequency vibration isolation system that overcomes the drawbacks of the prior arts and is capable of efficiently and effectively isolate/damp the vibration using combination of percent of weight of the machine supported by a plurality of springs and rubber supports.
In a main embodiment, the present invention provides a dual natural frequency vibration isolator comprising of an upper housing plate, a lower housing plate, at least one rubber support, a plurality of anti-slip pads and a plurality of springs. The upper housing plate is secured in the rubber support and the rubber support is fixed around the lower housing plate to form a casing. The plurality of anti-slip pads are mounted over the upper housing plate and below the lower housing plate to prevent slips and trips of a machine. The plurality of springs are secured in a cavity of lower housing plate to reduce the vibration of the machine by tuning external frequencies. The plurality of springs and rubber supports forms a sandwich between the upper and lower housing plate. The dual natural frequency vibration isolator damps both low and high natural frequency vibrations. It isolates the weight of a machine in a defined ratio and damps the vibration of

isolated percentage of weight of the machine separately by using the plurality of springs and the rubber supports.
In another embodiment, the present invention provides an upper housing plate made up of material but not limited to carbon steel, stainless steel etc. The anti-slip pads are made up of material but not limited to elastomer, rubber, neoprene, etc. to prevent slips and trips of the machine. The plurality of anti-slip pads reduces the machine-borne noise to ensure optimum deflection and level consistency both under static and under dynamic loading. Further, the lower housing plate has cavity to uniformly secure the plurality of springs to facilitate damping of low natural frequency as well as high natural frequency vibration.
In an another embodiment, the present invention provides the rubber supports made up of material but not limited to elastomeric material to isolate a percentage of weight in a defined ratio and damp the high natural frequency vibration of the isolated weight of the machine. The plurality of rubber supports is sandwiched between the upper housing plate and the lower housing plate and helps in holding the overall assembly of a dual natural frequency vibration isolator.
Yet in another embodiment, the present invention provides a dual natural frequency vibration isolator wherein the isolation efficiency of an isolator is improved by supporting a combination of percentage of weight in a defined ratio by a plurality of springs and rubber supports. The overall isolation efficiency is defined by the combination of fraction of weight of machine supported by each natural frequency spring. The defined ratio is determined by measuring the tensile strength of springs and rubber supports.
Still in another embodiment, the present invention provides a dual natural frequency vibration isolator in which the plurality of springs reduces the vibrations coming from the external surroundings from going into the machine and rubber supports reduces the machine from shaking due to vibrations.
Figure 1 shows the exploded perspective view of a dual natural frequency vibration isolator 100 comprising an upper housing plate 101 made up of material

but not limited to carbon steel, stainless steel etc. and an anti-slip pad 104 is fixed at the top of the upper housing plate 101 and is made up of material but not limited to elastomer, rubber, neoprene, etc. to prevent slips and trips of the machine. The anti-slip pad 104 reduces the machine-borne noise to ensure optimum deflection and level consistency both under static and under dynamic loading. A lower housing plate 102 is made up of material but not limited to carbon steel, stainless steel, etc. and an anti-slip pad 105 is fixed below the lower housing plate 102 and is made up of materials but not limited to elastomer, rubber, neoprene, etc. to prevent slips and trips of the machine. Further, lower housing plate 102 has cavity to uniformly secure the plurality of springs 106 to facilitate the damping of both low natural frequency as well as high natural frequency vibrations. The rubber support 103 is provided made up of material but not limited to elastomeric material, etc. to damp the high natural frequency vibration of the machine. The rubber support 103 is sandwiched between the upper housing plate 101 and lower housing plate 102 helps in achieving higher natural frequency and reducing machine shaking and also holds the overall assembly of a dual natural frequency vibration isolator system 100.
Figure 2 shows the perspective view of a dual natural frequency vibration isolator 100 having an anti-slip pad 104 made up of material but not limited to elastomer, rubber, neoprene, etc. mounted at the top of an upper housing/plate 101 made up of material but not limited to carbon steel, stainless steel, etc. to prevent slips and trips of the machine. The anti-slip pad 104 further facilitates in reducing the machine-borne noise to ensure optimum deflection and level consistency both under static and under dynamic loading. The lower housing plate 102 is made up of material but not limited to carbon steel, stainless steel, etc. and at bottom of it, an anti-slip pad 105 made up of material but not limited to like elastomer, rubber, neoprene, etc. is provided to prevent slips and trips of the machine. A rubber support 103 is provided made up of material but not limited to elastomeric material, etc. to damp high natural frequency vibration of the machine. The rubber support 103 is sandwiched between the upper housing plate 101 and lower

housing plate 102 and helps in holding the overall assembly of a dual natural frequency vibration isolator 100.
Figure 3 shows the top view of a dual natural frequency vibration isolator 100 having an anti-slip pad 104 made up of material but not limited to elastomer, rubber, neoprene, etc. mounted at the top of an upper housing plate 101 to prevent slips and trips of the machine. The lower housing plate 102 made up of material but not limited to carbon steel, stainless steel, etc. The rubber support 103 of high stiffness or higher natural frequency is provided made up of material but not limited to elastomeric material etc. to reduce machine shaking. The rubber support 103 is sandwiched between the upper housing plate 101 and lower housing plate 102 and helps in holding the overall assembly of a dual natural frequency vibration isolation system or damping system 100.
The dual natural frequency vibration isolator 100 isolates the percentage of weight of the machine in a defined ratio and damps the vibration of isolated percentage of weight of the machine separately by using the plurality of springs and rubber supports. The defined ratio is determined by measuring the tensile strength of the plurality of springs and rubber supports.
EXAMPLE 1 DETERMINATION OF VIBRATION LEVEL OF THE POWER PRESS
MACHINE
The dual natural frequency vibration isolator was placed under a 160 ton mechanical power press machine having a weight of 17000 kg. The mechanical power press machine was stroking in the vertical direction at 60 steps per minute (SPM). The vibration isolator placed on and under the machine has plurality of coil springs and rubber supports for damping the vibrations of the machine. When the machine was placed over it, the coil springs get deflected by 3.5 mm and exhibits a natural frequency of 8.4 hertz and rubber supports get deflected by 0.98 mm and exhibits a natural frequency of 15.93 hertz. The 78% of the weight of the

machine was borne by low natural frequency coil springs and 22% of the weight of the machine was borne by the high natural frequency rubber support of elastomeric material.
The distribution of weight of machine on the coil springs and rubber supports was determined by measuring the tensile/compressive strength of coil springs and rubber supports. The vibration analyzer was used to compute the vibration in frequency domain and accelerometer was used to measure the acceleration of vibrating machine. The measured values of frequency and acceleration were plotted and the results were obtained.
Referring to Figure 4 (a) and 4(b), it is observed when sensor (accelerometer) is placed on the machine bed, the vibration level in X-axis on machine bed is measured by determining the acceleration and frequency of vibration and the overall acceleration level is 230.6 mm/sec2 with peak acceleration of 104 mm/sec2 at a frequency of 44.73 hertz hence high level of acceleration is achieved in machine bed. Similarly, when the vibration level in Z-axis on machine bed is measured the overall acceleration level is 184.2 mm/sec2 with peak acceleration of 121 mm/sec2 at a frequency of 83.69 hertz.
Referring to Figure 5 (a) and 5(b), it is observed that when sensor (accelerometer) is placed On the floor near machine base, the vibration level in X-axis is measured by determining the acceleration and frequency of vibration and the overall acceleration level is 10.54 mm/sec2 with peak acceleration of 6.54 mm/sec2at a frequency of 83.69 hertz hence very low level of acceleration is transferred to the floor. Similarly, when the vibration level in Z-axis is measured the overall acceleration level is 23.7 mm/sec2with peak acceleration of 121 mm/sec2 at a frequency of 83.69 hertz.
The vibration isolation efficiency is calculated as given in equation (1):

Vibration efficiency = 1-(overall acceleration in machine body in X-axis or Z-axis/overall acceleration on the floor near machine base in X-axis or Z-axis)*100 ..(1)
Vibration isolation efficiency in X-axis = 1- (10.54/230)*100 = 95.4% Vibration isolation efficiency in Z-axis = l-(23.7/184.2)*100= 87.1%
Machine shaking is measured by placing a long dial gauge against machine body and comes out to be 1.9 mm in X-axis and 1.6 mm in Z-axis. The machine shaking is very less and isolation efficiency is high.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principals of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.

We claim:

1.A dual natural frequency vibration isolator (100) comprising of:
an upper housing plate (101) and a lower housing plate (102);
a plurality of anti-slip pads (104, 105);
a plurality of springs (106);
at least one rubber support (103);
characterized in that,
the upper housing plate (101) is secured in the rubber support (103) and the rubber support (103) is fixed around the lower housing plate (102) forming a casing;
the anti-slip pad (104) is mounted over the upper housing plate (101) and the anti-slip pad (105) is placed below the lower housing plate (102);
the plurality of springs (106) are secured in a cavity of the lower housing plate (102);
the dual natural frequency vibration isolator (100) damps both low and high natural frequency vibrations;
the dual natural frequency vibration isolator (100) isolates the weight of a machine in a defined ratio and damps the vibration of isolated percentage of weight of the machine separately by using the plurality of springs (106) and the rubber supports (103).
2. The system as claimed in claim 1, wherein, the plurality of rubber supports
(103) and the plurality of springs (106) is sandwiched between the upper
(101) and the lower (102) housing plate.

3. The system as claimed in claim 1, wherein, the dual natural frequency vibration isolator (100) damps the dual i.e. low and high frequency vibration, reduces the vibrations coming from the external surrounding from going in to the machine, reduces the machine from shaking and supports the percentage of weight of the machine in a defined ratio.
4. The system as claimed in claim 1, wherein, the plurality of anti-slip pads (104, 105) is made up of material but not limited to elastomer, rubber, neoprene, etc. to prevent slips and trips of the machine and helps in reducing the machine-borne noise, adds-up to damping properties to ensure optimum deflection and level consistency both under static and under dynamic loading.
5. The system as claimed in claim 1, wherein, the plurality of springs (106) damp high and low natural frequency and reduces the vibration of the machine by tuning external frequencies.
6. The system as claimed in claim 1, wherein, the plurality of rubber supports (103) damps the high frequency and reduces the machine shaking.
7. The system as claimed in claim 1, wherein, the housing plates (101, 102) are made up of material but not limited to carbon steel, stainless steel etc.
8. The system as claimed in claim 1, wherein, the defined ratio is determined by measuring the tensile strength of plurality of springs (106) and rubber supports (103).