GB2128698A

GB2128698A - Preventing simultaneous operation of pneumatically released, spring-applied brakes and pneumatic service brakes

Info

Publication number: GB2128698A
Application number: GB08326515A
Authority: GB
Inventors: Domenico Angelillo
Original assignee: Fabbrica Italiana Magneti Marelli SpA; Magneti Marelli SpA
Current assignee: Industrie Magneti Marelli SRL; Marelli Europe SpA
Priority date: 1982-10-11
Filing date: 1983-10-04
Publication date: 1984-05-02
Also published as: SE455591B; SE8305516L; FR2534211B3; IT8223690A0; GB2128698B; DE3336541A1; FR2534211A1; IT1153902B; SE8305516D0; GB8326515D0

Abstract

<IMAGE> <H0> Preventing simultaneous operation of pneumatically released, spring-applied brakes and pneumatic service brakes

Description

SPECIFICATION A system for pneumatic braking of vehicles by pneumatic and sprung braking elements This invention relates to a system for pneumatic braking ofvehicles by braking elements of the pneumatic and sprung combined type.

Known are oneumatic braking systems, wherein at least part of the braking elements are of the pneumatic combinedtype(forservicebrakingthrough usual pedal distributor) and sprung (for parking braking through a spring associated with a pneumatic piston normally counteracting the action of such a spring).

These elements are inserted in the braking system by suitable safety members preventing the application on the brakes of abnormal forces occurring upon conjoint and contemporaneous operation of the pneumatic braking members and springs. Generally, such safety members comprise suitable distributors shutting off the supply ofthe pneumatic pistion associated with the braking spring and connecting the chamber of said piston with exhaust.

Obviously, this solution does not fully satisfy use requirements, and particularly does not preventthe braking members from being subjected to overstres sesduetothesummation of the forces transmitted from the braking elementtothe braking members when an operator simultaneously operates both the pedal distributor and the manual distributor. Thus, breakages orfailures would occur to the vehicle braking members and further drawbacks.

A system according to the invention is directed to obviate to these and other drawbacks, always ensuring, independently ofthe operations being carried out by the user, that the vehicle braking is only effected either pneumatically or mechanically.

A system according to the invention, in which at least part of the pneumatic braking members thereof controlled by the pedal distributor are coupled with sprung members provided with pneumatic blocking members controlled by a manual distributor, is characterised by an automatic switchable shut off memberforcontrollingtheconnection ofthe pneumatic blocking members either with the pressure supply through the relative manual distributor, or with the exhaust relevantto the pedal distributor, which switchable shut off member is selectively actuated either by the pressure supplying said pneumatic blocking members, or by the pressure applied to the pneumatic braking means.

According to an advantageous embodiment ofthe automatic switchable shut off member,the latter has an envelope or shell, the interior of which is connected with the pneumatic blocking means and at opposite positions has sealing seats terminating in said manual and pedal distributors, and with which alternatively cooperates a shut off element responsive to the pressures time bytime applied to said pneumatic blocking means and said pneumatic braking means.

Obviously, said shut off element provided bythe shutoff member could comprise a membrane, or a plunger sliding in guides provide internally of the envelope or sheel, while possible force accumulators, such as weights and/or springs, exertthe action thereof in orderto maintain said shut off element in engagement with oneofthetwosealing seats provided in said envelopeorshell.

The invention will now be explained bythefollowing description referring to the accompanying draw ing showing byway of examplethe braking system according to the invention, and particularly in which: Fig. 1 is the diagram ofthe pneumatic braking circuit; and Fig. 2 is a sectional view showing an advantageous embodiment ofthe switchable member as provided bythe circuit of Fig. 1.

Referring to the diagram of Fig. 1,thecompressorA is connected with a plurality of tanks or reservoirs B1, B2, B3,thefirstofwhich supplies through a pedal distributorCthefront and rear braking elements D and F, respectively. The reservoir ortanks B2 connects through a manual distributor G an automatic switchable shut off member H, to be discussed about in the following, and which automatically controls the supplyforthe pneumatic blocking means F1 presented by the braking elements F. Finally, the reservoir or tank B3 forms an emergency reservoir ortank and forthe unboard services of a vehicle.

The system, when under conditions of normal operation, that is with said braking elements D and F inactive or at rest, has the pressure of reservoir ortank B2 present in the chambers ofthe pneumatic blocking means F1. Therefore, the pistons associated with such blocking means provide for maintaining the springs at compressed condition and counteractthe action of said springs on the brakes. Such an action is released by actuation of the manual distributor G, which by cutting off said reservoir ortank B2, connects the chambers ofthe blocking means F1 either with exhaust or ambient.

According to the invention,the pneumatic system of Fig. 1 is provided with the automatic switchable shut off member H shown in Fig. 2. Such a member has an envelope or shell 10 with a cap or cover 12 and is provided with a plurality of connectors, of which the first connector 14 connects to the manual distributor G. A second connector 16 connects the automatic shut off member H with the connectorA, ofthe pedal distributor A and which supplies the pneumatic units F2 ofthe braking elements F. Finally, connectors 18 and 20 terminate at the chambers ofthe pneumatic blocking means F1.

The connectors 14 and 16terminate inside of said envelope or shell 10, 12 with annular sealing surfaces 22 and 24 opposite to one another and conveniently spaced apart in order to slidably retain a shut off element 26 alternatively cooperating with said seats or surfaces 22 and 24. In the case shown, such an element comprises a flexible disc, such as a rubber disc, sliding with suitable clearance between guides 28 in said envelope orshell 10. Of course, said flexible disc 26 could be equivalently replaced by a plunger fitted with sealing seats cooperating with the corresponding seats 22 and 24 in said envelope or sheel 10, 12.

Said seats 22 and 24 (particularly the latter seat 24) define within said envelope or shell 10, an annular chamber 30 mainly comprising a crown 25 and which connects with said connectors 18 and 20.

When taking into account the pneumatic connection provided bysaid automatic switchable shutoff member H In the circuit of Fig.1, the regular service braking of the vehicle will clearly appear. Particularly, the operation ofthe pedal distributor C actuates as usual the braking elements D and Fwithoutcausing the operation of the automatic shut off member H.

This because on the upper side or face of the flexible disc26there acts upon a higher pressure than the braking pressure from the pedal distributor C and which presses said disc againstthe seat24. This condition could be further ensured by the action of a spring associated with said flexible disc26, and this particularly when said automatic shut off member H is installed at different position than horizontal.

Similar conditions would occurwhen the manual distributor G for parking braking is operated: on one hand, the connection ofthe reservoir ortank B2 with the pneumatic blocking means is shut off, and on the other hand, the latter are connected with atmosphere, thus releasing the springs, the operation of which actuates the rear brakes of the vehicle. In this case, any actuation of the pedal distributor C does not actuate the pneumatic units F2, since by entering the connec tor 6the air under pressure will lift said flexible disc 26 which closes the passage to the connector 14 and the air under pressure is exhausted to atmosphere through the connector C1 ofthe manual distributor G.

Such functional conditions would occur when said distributors C and G are simultaneously operated since, as above mentioned, the pressure of reservoir ortank B2 acting on said flexible disc 26 is aiways higherthan the braking pressure supplied through the pedal distributor C.

Modifications and changes can be made to the system according to the invention and particularly to the automatic shut off member H, and this in connection with the operating requirements and other requirements as requested by such a system. All of this within the scope ofthe present invention.

Claims

1. A system for pneumatic braking ofvehicles, in which at least part of the braking members thereof comprise two sections, that is a pneumatic section controlled by the pedal distributor, and the other or sprung section associated with pneumatic blocking means controlled by a manual distributor, characterized by an automatic switchable shut off member (H) controlling the connection of the pneumatic blocking means of said sprung section (F1) eitherwith the pressure supply (B2) through the manual distributor (G), or with exhaust (C2) provided by the pedal distributor (C), which automatic shutoff member is selectively actuated either by the pressure supplying said pneumatic blocking means (F1), or by the pressure applied by the pedal distributor (C) to the pneumatic braking members(D, F).

2. A system as claimed in Claim 1,characterized in that said automatic shut off member (H) has an envelope or shell (10, 12), the interior of which connects with the pneumatic blocking means (F1) and at opposite positions has sealing seats (22 and 24) terminating at the manual distributor (G) and pedal distributor (C), while a shut off element (26) resionsive to the pressurestime by time appliedto said pneumatic blocking means and pneumatic braking members (D, F) ofthe system alternatively cooperates with said sealing seats,

3. A system according to Claims 1 and 2, characterized in that said envelope or shell (10,12) internally adjacent said sealing seats (22 and 24) has guide means (28) forthe shut off element (26) alternatively cooperating with said sealing seats.

4. A system as claimed in Claims 1 to 3, characterized in that at least one of said sealing seats (22 and 24) extends inside of said envelope or shell (10, 12) with a crown (25) defining in said shell or envelope a chamber (30) connecting with the pneumatic blocking means (F1) through relative connectors (18,20).

5. Asystem as claimed in Claims 1 to 4, characterized in that said shut off element comprises a disc (26) preferably of resilient material.

6. Asystem as claimed in Claims 1 to 4, characterized inthatsaid shutoffelement (26) comprises a plunger sliding in guides provided by said envelope or shell (10,12) and which has sealing surfaces cooperat ingwiththoseofsaid envelope or shell.

7. A system as claimed in Claims 1 to 6, characte- rized by sprung means exerting the action thereof on said shut off element (26) for maintaining the latter adherent to one of the opposite two sealing seats (22, 24) of said envelope or shell (10,12).

8. Asystem as claimed in claims 1 to7, characterized bythe embodiment accordinglytothe accompanying drawing, substantially as described for the specified objects.