CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from Italian patent application no . 102021000001028 filed on January 21 , 2021 , the entire disclosure of which is incorporated herein by reference .

TECHNICAL FIELD

The present invention relates to a damping rod for vehicles .

The present invention finds its preferred, though not exclusive , application in aircraft vehicles . This application will be referred to hereinafter by way of example , it being clear that the damping rod of the invention could be used for other vehicular purposes .

STATE OF THE PRIOR ART

It is well known that in aircraft vehicles some of the elements thereof are connected by rods . Said rods are therefore provided with respective end portions defining portions for anchoring to the respective elements to be connected, and with a central portion carrying said end portions . Clearly, i f one of the elements connected by the rod vibrates , this vibration will be transmitted from the rod to the other element , thus propagating the vibration . These vibrations clearly increase the vehicular noise and reduce the fatigue li fe of the connected elements .

The need to reduce the transmission of vibrations between elements connected by rods in aircraft vehicles is therefore well known .

To overcome this problem, it is known to insert damping material between the end portions and the central portion .

However, this solution fails to ef ficiently dampen vibrations as they are transmitted along a direction parallel to the longitudinal axis of the rod and over a small contact area .

Therefore , there is a need to improve the damping ef ficiency of a connecting rod for elements of an aircraft vehicle , in particular while maintaining the same structural requirements and without increasing the weight or cost thereof .

The obj ect of the present invention is to meet the above requirements in an optimi zed and cost-ef fective manner .

SUMMARY OF THE INVENTION

Said obj ect is achieved by means of a damping rod as claimed in the appended claims .

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, a preferred embodiment is described below by way of a nonlimiting example and with reference to the accompanying drawings , wherein :

• Figure 1 is a perspective view of a damping rod according to the invention;

• Figure 2 is a sectional view of the rod in Figure 1 along the line I I- I I ;

• Figure 3 is a cross-sectional view of the rod in Figure 2 along the line I I I- I I I ;

• Figure 4 is an enlarged schematic view of the section in Figure 3 ;

• Figure 5 is an exploded perspective view, with parts removed for clarity, of the rod in Figure 1 ; and

• Figure 6 is a schematic sectional view, enlarged with respect to Figure 2 .

DETAILED DESCRIPTION OF THE INVENTION

In Figure 1 , the reference number 1 indicates , as a whole , a damping rod according to the invention configured to connect together a first and a second element of a vehicle (not shown) , for example an aircraft vehicle .

The rod 1 essentially comprises an intermediate body 2 , a first anchoring element 3 and a second anchoring element 4, in particular the first and second anchoring elements 3, 4 are carried by the intermediate body 2.

In particular, the intermediate body 2 has a prismatic, preferably hollow, and more preferably cylindrical shape, extending along a longitudinal axis A. Therefore, the intermediate body 2 defines a first end portion 2' and a second end portion 2' ', longitudinally opposite to the first, configured to carry the first and the second anchoring element 3, 4, respectively.

As described above, the intermediate body 2 defines a cylindrical cavity 5 passing along the axis A of the intermediate element 2 itself. The latter therefore defines an outer surface 2a and an inner surface 2b.

Both the first and the second anchoring element 3, 4 define an anchoring portion 3', 4' configured to allow connection to the respective first and second elements of the vehicle to be connected together, and a coupling portion 3' ’ , 4' ’ configured to allow connection of the first and second anchoring elements to the intermediate body 2. In particular, the anchoring portion 3', 4' and the coupling portion 3' ', 4' ' are made of one piece.

As illustrated by way of example, the anchoring portion example , configured to be connected to a pin integral with the first element , whereas the anchoring portion 4 ' of the second anchoring element 4 defines a plate configured to be rigidly connected to the second element , for example , by means of threaded elements .

According to one aspect of the invention, the coupling portion 3 ' ' of the first anchoring element 3 is integrally fixed to only the inner surface 2b of the intermediate body 2 , whereas the coupling portion 4 ^{, f} of the second anchoring element 4 is fixed to only the outer surface 2a of the intermediate body 2 .

In particular, the coupling portions 3 ' ’ , 4 ' ’ are fixed to the respective surface of the intermediate body 2 by friction . In greater detail , the anchoring elements 3 , 4 are made of metallic material , whereas the intermediate body 2 is made of composite material .

According to the illustrated embodiment , the coupling portion 3 ’ ’ defines a pin 6 able to fit into the seat 5 in contact with the inner surface 2a, whereas the coupling portion 4 ' ’ defines a sleeve 7 able to externally wrap the outer surface 2b of the intermediate body .

Advantageously, the metallic material of the anchoring elements 3 , 4 has a greater thermal expansion than the composite material of the intermediate body 2 . Consequently, friction fixing can be provided by dimensioning the anchoring elements 3 , 4 so that their coupling portions 3 ' ’ , 4 ' ’ have a larger/ smaller diameter than the inner/outer diameter of the intermediate body 2 , respectively, and heating the anchoring elements 3 , 4 and the intermediate body 2 until the di f ferent thermal expansion allows their mutual coupling when they return to room temperature . Advantageously, a layer of adhesive , preferably an epoxy adhesive , can be provided between the anchoring elements 3 , 4 and the intermediate body 2 .

Preferably, the first and second anchoring elements 3 , 4 are further connected to the intermediate body 2 by means of respective emergency connection means 8 configured to maintain the connection between the respective anchoring element 3 , 4 and the intermediate body 2 i f it is compromised .

Advantageously, said emergency connection means 8 comprise threaded elements 9 housed in respective openings 10 formed so that they radially pass through the anchoring portions 3 , 4 and the intermediate body 2 . Preferably, these openings 10 are three in number and circumferentially angularly equally spaced from each other about the axis A of the rod 1 , as shown in Figure 3 .

In the case shown, the threaded elements 9 comprise a screw configured to be coupled, on the opposite side of the rod 1 , to a bolt configured to tighten the threaded element 9 , thus providing a compressive force between the respective anchoring element 3 , 4 and the intermediate body 2 . Alternatively, the emergency connection means may comprise nails of the "hi-lock" type .

In particular, with reference to the schematic Figure 4 , the intermediate body 2 comprises an outer portion 11 , an inner portion 12 and an intermediate portion 13 in the radial direction from the axis A. The inner and outer portions 11 , 12 are both cylindrical in shape and coaxial with each other about the axis A and radially delimit the intermediate portion, which therefore is also cylindrical in shape and coaxial with the axis A.

Advantageously, the inner and outer portions 11 , 12 are made of epoxy resin, preferably reinforced with carbon fibers . In particular, the cross-linking temperature of carbon can be 130 ° with a thickness preferably comprised between 0 . 40 and 0 . 50 mm, more preferably of 0 . 45 mm . Preferably, the layers 11 , 12 can also comprise , at the end portions 2 ' , 2 ' ’ , glass fibers to improve the corrosion protection of the layers 11 , 12 where they are connected to the anchoring elements 3 , 4 .

Advantageously, the intermediate portion 13 is made of material having vibration damping properties , preferably a sponge made of polymeric material , preferably neoprene or silicone .

Advantageously, the intermediate portion 13 is connected to the inner and outer portions 11 , 12 by means of an adhesive layer 14 . In particular, the adhesive layer has a constant radial thickness , preferably between 0 . 1 and 0 . 3 mm, more preferably of 0 . 2 mm . Advantageously, the intermediate portion 13 extends over at least 80% of the length of the intermediate body 2 along the axis A.

Advantageously, the adhesive layer 14 is an epoxy layer . In particular, the intermediate body 2 is shown to provide an overall resistance of 100000 N .

Shoulders 16 , 17 are also provided between each anchoring element 3 , 4 and the intermediate body 2 and are configured to limit the shear force transmitted between the inner and outer layers 11 , 12 of the intermediate body 2 . In particular, as the exemplary embodiment described herein is geometrically formed, a first shoulder 16 is provided between the body 2 and the coupling portion 3 ' ’ of the first anchoring element 3 , for example , made by a flange extending from the pin of the latter, and a second shoulder 17 is provided between the body 2 and the coupling portion 4 ' ’ of the first anchoring element 4 , for example , made as a reduction in the radial dimension of the inner seat defined by the sleeve of the latter .

Each shoulder 16 , 17 is axially spaced along the axis A from the body 2 by a distance x, y, advantageously of 1 mm, and can be in contact therewith when the force transmitted between the anchoring elements 3 , 4 exceeds a predetermined threshold . Beyond this threshold, the layers being in axial contact between the anchoring elements 3 , 4 , the load would therefore be a simple normal load instead of a shear load .

In particular, the rod 1 can be made by using the following manufacturing steps : preparing by exfoliation the intermediate damping layer ;

• Assembling the elements forming the rod and the intermediate body 2 ,

• Carrying out a heating thermal treatment ;

• Carrying out a maintenance thermal treatment ; and

• Carrying out a cooling thermal treatment .

In particular, the preparation involves chemical activation using acetone .

In particular, the heating treatment comprises heating with a thermal gradient of 2 or 3 ° C per minute up to about 130 ° C, the maintenance step comprises maintaining the previous temperature for 75- 120 minutes at a pressure of

0 . 3 MPa, and the cooling step comprises cooling down to 60°C with a thermal gradient of 2 or 3°C per minute with subsequent free ambient cooling.

The operation of the embodiment of the rod described above is as follows.

A compressive stress between the first and the second element connected to the rod 1 is transmitted to the anchoring elements 3, 4. These, through the respective coupling portions 3' ’ , 4' ' , transmit the normal load along the axis A, respectively, to the inner and outer portions of the intermediate body 2.

Since the normal stress is imparted in the intermediate body 2 between two portions 11, 12 which are not rigidly in contact with each other, the normal stress is necessarily transferred as shear stress through the damping layer 13. In this way, excellent vibration damping performance is guaranteed and, at the same time, correct load transmission is ensured.

In the event of excessive stress, i.e., in the event that the shear stress in the damping layer is higher than that deriving from the mechanical characteristics of the layer itself, the presence of the shoulders 16, 17 allows both layers 11, 12 to be placed in direct contact with each of the anchoring elements 3,4, thus allowing stress transmission in the normal direction between the latter. Thus , by varying the transverse modulus of elasticity and the shear modulus of the layer 13 , it is possible to optimi ze the damping of the rod 1 according to its dimensions and the loads to which it is subj ected .

The advantages of a damping rod according to the invention are clear from the foregoing .

The damping rod according to the invention allows the vibrations between two elements of a vehicle to be connected to each other to be dampened in an optimi zed way .

In particular, the excellent damping characteristics are obtained in a widespread, economical , and compact way without any weight increase .

Moreover, the excellent damping characteristics do not af fect the structural characteristics of the rod compared to known rods .

The use of the shoulders illustrated above allows the maximum peak load transmissible by the rod 1 to be increased .

Lastly, it is clear that modifications and variations may be made to the damping rod according to the present invention, without however departing from the scope of protection defined by the claims .

In particular, the geometry of the intermediate body 2 of the anchoring elements 3 , 4 may be changed . Similarly, the fastening means 8 may be absent or made differently.

Furthermore, the materials of which the intermediate body 2 is made can vary according to the claimed limits.