Title of Invention

A FRICTION SNUBBER USED FOR DAMPING OSCILLATION IN PASSENGER COACHES

Abstract

This invention relates to a friction snubber used for damping oscillations in passenger coaches comprises: a cylindrical sleeve, a friction damping arrangement positioned within said sleeve a friction spring assembly positioned below the friction damping arrangement for providing pressure onto the damping components a central spindle, said friction spring assembly being assembled on said central spindle on which said sleeve and friction damping arrangement is positioned, said sleeve and friction damping arrangement being positioned upon said friction spring assembly, said central spindle being secured onto the bottom of the glass by means of mounting and cushioning arrangement.

Full Text

The present invention relates to a friction snubber used for damping oscillation in passenger coaches. BACKGROUND It is a well known fact that India has the largest railway network in Asia. At present, the Integral Coach Factory, Chennai of the Indian Railways manufactures passenger coaches. Each coach consists of two bogies. The Railway coach factory, Kapurthala and BEML, Bangalore also manufacture the same bogies. The bogies manufactured have two axles, four wheels and a bogie frame. The bogie frame is supported on eight springs which are called the 'primary springs'. In other words, each axle has four springs, two on each side. The arrangement of mounting the bogie frame on the axle and springs is called 'primary suspension' and the arrangement of mounting the body of the coach on to the bogie is called 'secondary suspension'. While in motion, the wheels of the bogies transmit lateral and vertical deflection to the bogie frame through the primary springs. At present, these oscillations of the springs on primary suspension are dampened by providing dash-pot. The existing dash-pot is arranged on the spring seats on each side of the axle box and is filled with hydraulic oil. The dash-pot consists of an outer glass and an inner tapered guide. A guide cap having small oil holes is screwed on to the bottom of the guide. Between the glass and the guide a homopolymer acetal guide bush is provided. The guide cap retains the guide 2 bush in position and forms a part of the damping arrangement. The glass, the guide cap and the guide are assembled so as to damp the oscillation and vibration of the primary springs in vertical direction. As mentioned earlier the glass is filled up with hydraulic oil. When the axle moves upwards, the gap between the guide cap and the bottom of the glass is reduced, forcing the oil to flow through the hole into the guide cap and into the space in the guide. When the spring has pushed the bogie frame and the guide upwards, the distance between the guide cap and the bottom of the glass increases thereby increasing the volume and causing the oil in the guide to flow back in the glass reservoir through the hole in the guide and guide cap holes. This gives a forced circulation of the oil as a result of which the oscillation and vibration of the primary springs are absorbed. One of the disadvantages of the dash-pot are that there is a lot of oil leakage and spillage of hydraulic oil during operation. It is very uneconomical and costly to refill hydraulic oil in to the glass. Oilless dash-pot causes poor riding quality to the coaches. During the maintenance and the periodic overhaul (POH) of these coaches which takes place once in one to and one and a half years, the oil of the dash-pot is wasted and if spilled, the shop floor becomes very untidy and messy. It is therefore the object of the present invention to overcome the aforesaid disadvantages. Another object of the present invention is to avoid the use of hydraulic oil, which is not only expensive but also if spilled on the shop floor, makes it very messy. 3 Further object of the present invention is to provide a friction snubber, which can be accommodated within the restricted space of the dash-pot assembly. Yet another object of the present invention is to lower the maintenance cost (zero maintenance between POH to POH) of these coaches and still keep the damping effect of the said coaches intact. The present invention relates to a friction snubber, which is a mechanical damping device which works in a uniform cylindrical bore. Accordingly the present invention provides a friction snubber used for damping oscillations in passenger coaches comprising: a cylindrical sleeve, a friction damping arrangement positioned within said sleeve a friction spring assembly positioned below the friction damping arrangement for providing pressure onto the damping components a central spindle, said friction spring assembly being assembled on said central spindle on which said sleeve and friction damping arrangement is positioned, said sleeve and friction damping arrangement being positioned upon said friction spring assembly, said central spindle being secured onto the bottom of the glass by mounting and cushioning arrangement. The sleeve is positioned onto the inside of the guide of the bogie which is secured onto the bogie frame. 4 A ring is inserted in the gap between the guide and sleeve. The said ring is welded both to the sleeve and to the guide of the bogie. The out side of the said sleeve is a reverse tapered sleeve or a straight sleeve, or a combination of taper & straight. The mounting and cushioning arrangement is welded to the glass. The mounting and damping arrangement may be welded to the glass from the outside or from inside. The mounting and damping arrangement is welded to the glass by bracket means and the angle is bolted in any conventional manner to the glass. The central spindle passes through the bottom of the glass and is secured to the bottom of the glass. The friction damping arrangement comprises of at least two wedge blocks, at least three friction shoe arrangements. Below the said blocks, is a friction spring assembly. The lower end of the friction spring assembly has a nut for holding the said spring assembly. The friction damping arrangement comprises of asbestos pad (a friction material) and a steel shell segment with wedges being an integral part of the steel shell. The said shells are segments of a cylinder and has an outer and inner shell. The outer shell being the friction material. The said inner and outer shell are divided into three equal parts with small gaps between adjacent parts. These gaps facilitate independent pressure on the guide walls, and allows self adjustment of the shelfs against the sleeve during wear & tear. 5 According to the present invention the guide cap and the base of the glass of the existing dash-pot have been modified to accommodate the snubber assembly. Suitable modifications in the glass have also been made for securing the spindle of the snubber. A hole is drilled or bored in the guide cap and glass to allow the passage of friction snubber parts. The present invention will now be described with reference to the accompanying drawings: Figure 1 illustrates a general arrangement of the existing primary spring and the dash-pot. Figure 2 illustrates the conventional dash-pot assembly Figures 3 and 3(a) illustrates the friction snubber arrangement in the modified component of dash-pot assembly according to the present invention. Figures 4 and 4(a) shows the friction snubber arrangement. Figure 5 illustrates another embodiment of positioning the friction snubber assembly externally. Figure 6 gives a cross sectional view of the friction snubber assembly. As shown in figure 2 the glass (1) is mounted on the spring seat of the axle box (2) and is filled with hydraulic oil (3). To the inner side of the glass (1) there is a 6 guide (4) which is welded onto a bogie frame (5). Between the glass (1) and the guide (4), a guide bush (6) is provided. A guide cap (7) having small oil holes (8) is screwed to the bottom of the guide (4). The friction snubber according to the present invention as shown in figure 3 & 3(a) is provided within the limited space in the modified components of the dash-pot assembly namely, glass (1), guide (4) and guide cap (7). The glass (1) is a glass-shaped pot made of steel, which contains the oil. The friction snubber as shown in figures 3 and 4 comprises of a reverse tapered sleeve (9), which is positioned within the guide (4). Within the sleeve (9) there is provided a friction damping arrangement (10). The straight sleeve is provided with a ring for securing the sleeve to the inside of the guide. The said friction damping arrangement (10) comprises of an outer friction material (10) which rubs against the inner surface of the cylindrical sleeve (9) and is positioned on the outer surface of the steel shell Segment (10). This entire friction damping arrangement is positioned upon a friction spring assembly (11). There is a central spindle (12) on which all the components of the snubber assembly including the spring assembly are assembled which in turn is secured on the bottom of the glass by mounting and cushioning arrangement (13). The sleeve is welded on to the guide (4) of the bogie frame. In figure 3(a) and 4(a), the sleeve runs parallel to the guide (4) and are secured to each other by a ring (14). Also brackets (15) are welded onto the bottom of the glass for securing the mounting and cushioning arrangement (13). Figure 5, is the alternative damping arrangement. 7 In Figure 6, it may be seen that there is a two wedge blocks (16) and a friction shoe arrangement (17). A nut (19) is secured at the bottom of the spring assembly (18). WORKING: When the bogie is in motion, the wheels provide oscillation to the spindle secured to the bottom of the glass. The principle involved in the working of the friction snubber is 'friction damping'. According to this principle the friction force opposes movement, when a surface slides upon another surface. A force is required to move the said surfaces. As a result of which the mechanical energy which is converted into heat energy is dissipated by conduction. During the motion of the bogie, the friction damping components move upwards and downwards rubbing against the inner wall of the sleeve providing damping effect. 8 I claim: 1. A friction snubber used for damping oscillations in passenger coaches comprises: a cylindrical sleeve, a friction damping arrangement positioned within said sleeve a friction spring assembly positioned below the friction damping arrangement for providing pressure onto the damping components a central spindle, said friction spring assembly being assembled on said central - spindle on which said sleeve and friction damping arrangement is positioned, said sleeve and friction damping arrangement being positioned upon said friction spring assembly, said central spindle being secured onto the bottom of the glass by mounting and cushioning arrangement. 2. A friction snubber as claimed in claim 1 wherein the outside of said sleeve is a reverse tapered sleeve or a straight sleeve, or a combination of both reverse taper and straight. 3. A friction snubber as claimed in claim 1 wherein the mounting and cushioning arrangement is welded to said glass. 4. A friction snubber as claimed in claim 1 wherein said friction damping arrangement comprises of asbestos pad (a friction material) and a steel shell segment. 9 10 5. A friction snubber as claimed in claim 1 wherein said central spindle passes through the bottom of the glass and is secured to the bottom of the glass. 6. A friction snubber as claimed in claims 1 and 4 wherein said shell are segments of a cylinder and has an outer and inner shell, the outer shell being made of asbestos pad (friction material) and secured on to the inner shell. 7. A friction snubber as claimed in claim 6 wherein said inner and outer shell are divided into three equal parts with gaps between adjacent parts for facilitating independent pressure on the guide walls. 8. A friction snubber as claimed in any of preceding claims wherein a ring is inserted in the gap between the guide and sleeve, said ring is welded both to the sleeve and to the guide of the bogie. 9. A friction snubber used for damping oscillations in passenger coaches substantially as herein described with reference to the accompanying drawings. This invention relates to a friction snubber used for damping oscillations in passenger coaches comprises: a cylindrical sleeve, a friction damping arrangement positioned within said sleeve a friction spring assembly positioned below the friction damping arrangement for providing pressure onto the damping components a central spindle, said friction spring assembly being assembled on said central spindle on which said sleeve and friction damping arrangement is positioned, said sleeve and friction damping arrangement being positioned upon said friction spring assembly, said central spindle being secured onto the bottom of the glass by means of mounting and cushioning arrangement.

Documents:

01106-cal-1998-abstract.pdf

01106-cal-1998-claims.pdf

01106-cal-1998-correspondence.pdf

01106-cal-1998-description(complete).pdf

01106-cal-1998-description(provisional).pdf

01106-cal-1998-drawings.pdf

01106-cal-1998-form-1.pdf

01106-cal-1998-form-2-1.1.pdf

01106-cal-1998-form-2.pdf

01106-cal-1998-form-3.pdf

01106-cal-1998-form-5.pdf

01106-cal-1998-p.a.pdf

1106-CAL-1998-(22-02-2012)-FORM 27.pdf

1106-cal-1998-granted-abstract.pdf

1106-cal-1998-granted-claims.pdf

1106-cal-1998-granted-correspondence.pdf

1106-cal-1998-granted-description (complete).pdf

1106-cal-1998-granted-drawings.pdf

1106-cal-1998-granted-examination report.pdf

1106-cal-1998-granted-form 1.pdf

1106-cal-1998-granted-form 2.pdf

1106-cal-1998-granted-form 3.pdf

1106-cal-1998-granted-form 5.pdf

1106-cal-1998-granted-form 6.pdf

1106-cal-1998-granted-letter patent.pdf

1106-cal-1998-granted-reply to examination report.pdf

1106-cal-1998-granted-specification.pdf