Warning device for hydraulic systems

(© Agent:

© Warning device for hydraulic systems.

(© invention of: Juan Belart and Ulrich Seidel.

© ©) (© Conventional priority: Patent application filed in the Federal Republic of Germany ie December 10, 1969, η. P 19 61 845.2 in the name of the applicant.

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44505 2073539, The present invention relates to a warning device for hydraulic systems, the device comprising a cylindrical bore in the body and a sliding element which is sealingly disposed in said bore. The sliding element consists of two pistons which are arranged coaxially, at a certain distance from each other, so as to slide in leaktight manner in the borehole one behind the other or one against the other. The front faces of the pistons which are distant from each other are subjected to the action of the pressure agent circuits to be separated. In these warning devices, it is important to separate the two pressure agent circuits from one another, so that in the event of failure of one of the circuits an alarm signal can be given , the piston in the cylinder being simultaneously pressed against a stop so as to maintain at least one circuit in operating condition.

Warning devices are already known for the braking systems of dual-circuit vehicles (English patent n ° 999 538) in which two pistons are arranged so as to slide against one another and undergo the pressure prevailing in the brake lines and in which electrical contact switches are actuated by said pistons. These warning devices have the disadvantage that in the event of a brake circuit failure, a large displacement of the pistons is essential to ensure a reliable reaction of the electric switch. An essential disadvantage resulting from the relatively large displacement of the pistons is that the clearance of the brake pedal - which, of course, must be limited - is in turn unduly extended. The piston during the action of the pressure agent in the brake circuit in operation is influenced by the slightest leak in one of the two brake circuits. The corresponding piston does not move until the force, generated by the absolute pressure in the braking circuit, acting on the piston, is greater than the force of the adjusting spring. This however has a negative influence on the sealing provided by the seals.

The object of the present invention is to allow a particularly small movement of the pressure agent in such warning devices and a small movement of the piston seal during braking. The device must be able to operate without an adjustment spring and must have a fixed switching point for alarm indication. A more reliable operation and a more compact type of construction must be able to be obtained with separate constituent elements, fewer and less costly to constitute the warning device.

According to one of the characteristics of the invention, the front faces of the two pistons, opposite one another, have chamfered or curved guide surfaces at the end of a contact pin rests against said contact surfaces. chamfered or curved guide, thus keeping the pistons in their i

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To allow immediate detection of leaks at a piston seal, a pressure agent outlet is provided in the form of a groove which communicates the space between the two pistons with the chamber in which the piston is placed. signaling device. This room in turn has an outlet opening communicating with the atmosphere. Preferably, a stop valve is interposed in the communication conduit between the atmosphere and the space between the two pistons, so as to allow the outlet of any oil leakage to the outside without allowing the penetration of dust inside in the space between the two pistons.

The signaling device preferably consists of a contact pin of synthetic material which, in its initial position, presses at one end on the body and at the other end on the two front faces of the piston.

The front faces of the pistons placed one opposite the other may be of conical shape or of solid or hollow spherical shape i or alternatively, they may have chamfered surfaces.

The advantages of the present invention lie in the fact that the losses of pressure agent are reduced and a rapid oscillation of the piston seals occurs with each braking. Manufacturing is more economical because a smaller number of components are necessary and that a simple spring is used which does not require any adjustment. The simple arrangement of a single contact pin and a single signaling lamp facilitates system monitoring and thus meets the reliability conditions of a warning device.

The objects and characteristics of the present invention will appear more clearly on reading the following description of exemplary embodiments, said description being made in relation to ï

The single figure which represents an exemplary embodiment of the invention.

The warning device consists of a body with a hole

3θ cylindrical 2 and the ends 3 and 4 of the pressure agent conduits, these ends being placed in alignment with the bore. Stops 5 and 6 are provided in the connections 3 and 4. In the cylindrical bore 2 are arranged ooaxially two pistons 7 and 8 as well as seals 9 and 10 which can slide one behind the other or one against the 'other. Eh position of rest, the conical ends 11 and 12 are in contact with the synthetic contact pin 13 which is pressed by the spring 14 with a certain force against the stop 15. The spring 14 presses on the cap which is adapted in the body 1. The synthetic contact pin 13 has a metallic core 17 which transmits the electrical signal to the cable 18.

The operation of the device provided according to the invention is as follows:

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during a practically uniform increase in pressure in the two pressure agent circuits, the two pistons 7 and 8 move in the direction of one another until they come to press one another against the ends of the thrones of cSne 11 and 12, thus supporting each other. As a result of their movements towards each other, the conical ends 11 and 12 move the contact pin 13 only enough so that said pin is moved away from its stop 15 without however triggering an electrical signal. It is only when one of the two braking circuits fails, that is to say when a considerable excess pressure is established in one of the two braking circuits 3 and

4, that the two pistons 7 and 8 are pressed together against the stops 5 and 6.

Simultaneously, the synthetic contact pin 13 is moved completely out of the hollow space 20 and its metallic core 17 comes to press against the pistons 7 or 8 as a result of the action of the spring 14 so that, even in the case of vibrations in the body, a secure electrical contact between the pistons 7 or 8 and the core

17 is however insured. The synthetic contact pin 13 has a groove allowing the pressure agent to pass through the space 20 to the chamber 19 and from there, through the groove 21, in the cap 16 to the outside, in the event that a leak occurs at one of the two seals 9 or 10. The cap is designed so as to allow the evacuation or the outward flow of the pressure agent while protecting it from atmosphere the inner part.

Although the principles of the present invention have been described above in relation to particular embodiments, it will be clearly understood that said description is given only by way of example and does not limit the scope of the invention.

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