Constant-level pneumatic suspension for motor vehicles

Claim 2

A constant-level pneumatic suspension for vehicles, particularly commercial vehicles and buses, including a pneumatic circuit for connecting a compressed-air supply to the air springs of the suspension, regulating valve means associated with the pneumatic circuit for control­ling the admission and discharge of compressed air to or from these springs as a result of variations in the load on the vehicle, on/off solenoid valves (18) interposed between the regulating valves (14) and the air springs (12) for isolating the air springs (12) from the pneumat­ic circuit (10a) when the vehicle exceeds a predetermined speed characterised in that it further includes auxiliary on/off solenoid valves (26) interposed between the compressed-air supply (S) and the regulating valve means (14) and operated in synchronism with the on/off solenoid valves (18) to isolate the portions of the pneumatic circuit (16a) between the latter (18) and the auxiliary on/off solenoid valves (26).

Claim 3

A suspension according to Claim 1, characterised in that the on/off solenoid valves (18) and the auxiliary on/off solenoid valves (26) are combined in pairs in a single four-way solenoid valve (28).

Claim 4

A constant-level pneumatic suspension, in which the pneumatic circuit includes at least one pair of corre­sponding right- and left-hand air springs, a pair of branch pipes (17) communicating with the air springs (12) and connected to a single main pipe (16) for the connec­tion to a compressed air supply, characterised in that, for the pair of springs (12), the suspension includes a levelling valve (50) having a first connector (54) connected to the main pipe (16), a second discharge connector (56), and apair of third connectors (58a, 58b) each connected to the respective branch pipe (17), the levelling valve (50) including a first portion (50a) for modulating the pressure in the third connectors (58a, 58b) in dependence on the load on the vehicle and a second portion (50b) including a seat (60) and a corre­sponding obturator (62) for enabling communication between the branch pipes (17) and the first portion (50a) of the solenoid valve in a first position and, in a second position, for cutting off the air flow between the third connectors (58a, 58b) and the first and second connectors (54, 56) and for isolating the third connectors (58a, 58b) simultaneously from each other.

Claim 5

A constant-level pneumatic suspension, in which the pneumatic circuit includes at least one pair of corre­sponding right- and left-hand air springs, a pair of branch pipes (17) communicating with the air springs (12) and connected to a single main pipe (16) for the connec­tion to a compressed air supply, characterised in that, for the pair of springs (12), the suspension includes a levelling valve (50) having a first connector (54) connected to the main pipe (16), a second discharge connector (56), and apair of third connectors (58a, 58b) each connected to the respective branch pipe (17), the levelling valve (50) including a first portion (50a) for modulating the pressure in the third connectors (58a, 58b) in dependence on the load on the vehicle and a second portion (50b) including a seat (60) and a corre­sponding obturator (62) for enabling communication between the branch pipes (17) and the first portion (50a) of the solenoid valve in a first position and, in a second position, for cutting off the air flow between the third connectors (58a, 58b) and the first and second connectors (54, 56) and for isolating the third connectors (58a, 58b) simultaneously from each other.

Claim 6

4A suspension according to Claim 3 characterised in that the second portion (50b) of the levelling valve (50) includes a seat (60) for the obturator (62), which is coaxial with a cylindrical wall (68) with axially spaced apertures (68a, 68b) communicating with the branch pipes (17), the obturator (63) having an annular sealed portion (66) for location, in the second position of the obturator (62), between the apertures (68a, 68b) in order to isolate the branch pipes (17) from each other.

Claim 7

A suspension according to any one of the preceeding claims, characterised in that control means are associat­ed to the on/off solenoid valves, which include a timer (24) for the periodic deactivation of the on/off solenoid valves (18, 26, 28, 32b, 50b) when the vehicle is moving.