WO1998054415A1

WO1998054415A1 - Improved pneumatic suspension for vibrating tamping rollers

Info

Publication number: WO1998054415A1
Application number: PCT/EP1998/002765
Authority: WO
Inventors: Domenico Domenighetti
Original assignee: Niarb S.A.
Priority date: 1997-05-30
Filing date: 1998-05-12
Publication date: 1998-12-03
Also published as: AU8016498A; IT1292046B1; ZA984481B; ITMI971281A1; ITMI971281A0

Abstract

The pneumatic suspension device, suitable for transmitting torque, consists of a vibration-damping pneumatic ring, the inner surface of which rests on a rim connected to the part of the machine which must be free from vibration (for example, a hydraulic engine (12) directly flanged on a reduction unit (13), both made integral with a bracket (9) and a frame (8)), while the outer surface of the pneumatic ring (1) is gripped by a series of S-shaped jaw elements (3, 3') bolted onto a support ring (4) welded to the inner cylindrical wall of the vibrating drum (5). Said S-shaped gripping elements (3, 3') are secured, at the ends opposite those fixed to the support ring (4), to a symmetrical pair of metal rings (20 and 20') which are pressed against the sides of the pneumatic ring.

Description

DESCRIPTION

IMPROVED PNEUMATIC SUSPENSION FOR VIBRATING TAMPING ROLLERS

In vibrating compacting rollers for road construction, and in many other vibrating machines, it has been demonstrated that systems with a cushion of air for insulating from vibration those parts of the machine which should be kept free from vibration are superior. The vibrating effect is instead concentrated on the ground or on other materials which are to be subjected to vibration.

Swiss patents No. 364804 of August 25, 1958 and No. 365.099 of August 28, 1958 and relative Italian patents No. 593.924 of August 27, 1958 and No. 595.270 of October 1, 1958, describe some devices of this type.

In particular, Italian patent No. 1.213.179 describes a pneumatic suspension, suitable for transmitting torque, which comprises a single vibration-damping pneumatic ring, with a particular structuring of the rigid elements which envelop and block the pneumatic ring holding it in position. The state of the art according to this last cited patent is reproduced herein in Figures 1, 2 and 3, which diagrammatically represent, respectively: Figure 1, a sectional view along the plane marked 1-1 in Figure 2; Figure 2, a sectional view along 2-2 of Figure 1 showing the pneumatic ring, the vibrating drum and some parts of the general frame of machine; and Figure 3, a partial perspective view of the vibration- damping pneumatic ring.

The vibration-damping devices in this field prior to patent IT 1.213.179 comprised, as a basic element, one or more toroid-shaped pneumatic rings, suitably fitted on generally metallic inner rigid elements and outer rigid elements, having geometric shapes of solids of revolution.

Once fitted in position, the inner rigid elements and the outer rigid elements are interconnected solely by means of the pneumatic ring in such a way that if, for example, the set of inner rigid elements is subjected to vibration, the set of outer rigid elements feels the effect thereof only through the pneumatic ring , which is able to dampen a large part of the vibration.

According to said Italian patent No. 1.213.179, the outer rigid elements 3 are made in such a form that, when fixed in position, they form a polygonal structure, which experience has shown to be particularly suitable for transmitting torque.

In Figure 1 the vibration-damping pneumatic ring is indicated by 1 , the set of inner rigid elements, of the "rim" type, by 2 and the outer or peripheral rigid elements by 3.

These elements 3 are fixed on a generally metallic ring 4, integral with the vibrating drum 5, which acts as a tamper or compactor. The valve 6, which allows the pressure inside the central pneumatic ring to be controlled, can be seen protruding from the inner rigid element 2 (rim). The outer rigid elements 3, 3' are fixed in pairs on the rigid ring 4 by means of bolts 7.

In Figure 1 the main frame of the machine, which must remain free from vibration, is indicated by 8, and the descending bracket by 9. The bracket is integral with the frame and serves to support the end of the vibrating drum 5 which is now being examined. A protective covering 10 is fixed to the bracket 9 by means of bolts 11 and serves to protect the hydraulic engine, directly connected to the reduction unit 13, from any object projected from the outside. The reduction unit is fixed to the bracket 9 and at the other end carries the rim 2 fitted with valve 6 and fixed with bolts 14.

The ring 4 (Figure 1) with an inner diameter smaller than the outer diameter of the pneumatic ring is welded onto the vibrating drum 5.

In addition, the vibrating drum 5 is provided with an inside wall 17 which also serves to support the vibrator 18 in the centre of the drum.

The rigid elements 3 and 3' are S-shaped in cross-section, which allows the pneumatic ring 1 to be enveloped and gripped in a single movement. Said outer rigid elements 3 and 3' are arranged along the outer circumference of the pneumatic ring 1, spaced apart from one another (Figure 1) by a distance dl5, which is a function of the distance dl6, along which each element 3 and 3' engages with the outer wall of the pneumatic ring 1. With R indicating the outer radius of the pneumatic ring 1 , according to said patent the following geometrical conditions are to be complied with:

(R.π/2) > di6 > (R.π/8)

The distance di5 along the circumference between two adjacent outer rigid elements must be within on half and one and a half times the length di6 measured along the circumference of each element 3 and 3'.

Since numerous examples of machines built according to the patent cited have been constructed in recent years, it has been possible to accumulate extensive statistical experience on the practical advantages and disadvantages.

Experience has shown that even if the instructions contained in Italian patent No. 1.213.179 were strictly observed, the operation of the device did not meet expectations, especially with the widespread use of "radial", or "radial ply" (or belted) tires which do not withstand the grip of rigid external elements such as those proposed and described in the aforementioned patent.

The object of the present invention is to overcome the drawbacks of the prior art. A further object is to reduce the localized stresses that occur in the device of the prior art.

These objects have been achieved with a pneumatic suspension as stated in claim 1.

The new suspension makes it possible to use radial or radial ply tires as pneumatic suspensions, with a good vibration damping effect, on vibrating compacting or tamping rollers.

The invention will be described below with reference to the appended figures in which: Figures 1, 2 and 3 illustrate the state of the art, as stated above;

Figure 4 is section along 4-4 of Figure 5, of an unrestrictive exemplary embodiment of a suspension according to the invention;

Figure 5 is a section along 5-5 in Figure 4;

Figure 6 shows a detail of Figure 4 enlarged with respect to said figure. Figure 4 shows a portion of a vibrating drum similar to that shown in Italian patent No. 1.213.179. The same notations have been maintained whenever possible and the description of details already described is not repeated. According to the present invention, a new element of fundamental importance has been introduced, that is, a pair of toroid-shaped metal rings 20 and 20' which are fixed by welding, for example, 21 and 21' of Figure 6, or by other known means, to the ends of the S-shaped elements 3 and 3' nearest to the center of the pneumatic ring.

These metallic rings 20 and 20' rest laterally against the pneumatic ring 1 and are pressed against it by the S-shaped elements 3 and 3', enveloping it and holding it along its entire circumference, thus greatly reducing the localized stresses that occurred in the device of the previous patent.

According to a preferred embodiment of the present invention, the radius r of the body with a circular section of the rings 20 and 20' is comprised between values linked to the greatest outer radius R of the circumference of the pneumatic ring according to the following inequality:

0.01R < r < 0.05R, preferably 0.012R < r < 0.05R.

The metallic rings 20 and 20' are gently pressed against the upper part of the sides of the toroid-shaped pneumatic ring 1 through the combined action of the bolts 7 and of the elements 3 and 3' which, in this embodiment, are welded onto the toroid-shaped metallic rings 20 and 20' by means of welding 21 and 21 '.

Claims

1. A vibration-damping pneumatic suspension for vibrating tamping rollers, which comprises at least one pneumatic ring (1), on which are engaged rim-shaped inner rigid elements (2) connected with the part of the machine which must be free from vibration and pairs of outer elements (3, 3'), which are connected with the part of the machine (5) intended to vibrate, characterized in that said outer elements (3, 3') are fixed with their respective ends to a pair of metallic rings (20, 20') which, once fixed in position, form an enveloping structure in direct contact with the pneumatic ring (1).

2. A pneumatic suspension according to claim 1, in which the outer rigid elements (3, 3') are S-shaped and are welded to metallic rings (20) and (20').

3. A pneumatic suspension according to claim 2, characterized in that the rings (20, 20') are circular in cross section and the values of the radius (r) of the circular section of the metallic rings (20) and (20') are within 1% and 5% of the value of the greatest radius (R) of the circumference of the pneumatic ring.