MASTER CYLINDER RESERVOIR

Abstract: A master cylinder reservoir (1) is provided with flexible arms (14, 15) adapted to snap-engage with a retaining formation (8A) on a pressure cylinder (8), the arms lying generally parallel to a spigot (9) of the reservoir received within a socket (9A) of the cylinder. A seal (13) is provided between opposed surfaces of the spigot and socket.

Description: This invention relates to a master cylinder, primarily for use in a vehicle hydraulic braking system, and including a separately made hydraulic fluid reservoir having at least one connector means adapted to form a connection between the reservoir and a pressure cylinder. One prior master cylinder proposal is illustrated in our published British specification No. 2086512 and employs rubber bungs carried by the cylinder to receive hollow spigots projecting from the reservoir such as to mount the reservoir on the cylinder in fluid-tight manner. Our published British Specification 2064037 shows an alternative but similar form of connector spigot on a reservoir container. Both of these proposals provide a satisfactory reservoir to cylinder connection but have the disadvantage of being relatively expensive to manufacture because the rubber bung or other mounting means need to be of somewhat complex form to perform the necessary retention and sealing functions and also of adequate substance and strength to serve as a mounting for the reservoir. In another known proposal illustrated in EP-A-0049657, a fluid reservoir has a connector means engaged with port means of a pressure cylinder, the reservoir having a flexible arm provided with catch means which is snap-engaged with a retaining formation of the cylinder to retain the reservoir in an operative position on the cylinder. An object of the present invention is to provide a master cylinder in which the reservoir to cylinder mounting and connection is simplified. The master cylinder according to the present invention, is characterised in that the flexible arm forms part of the connector means and the retaining formation of the pressure cylinder is carried by the port means. In one preferred arrangement, the flexible arm lies generally parallel to and externally of a projecting hollow spigot connector of the reservoir and the catch means is a formation thereon providing a shoulder for engagement with said retaining formation on the cylinder. Said formation is conveniently adapted for reception within a socket on the cylinder adapted to receive said connector, for which purpose said shoulder projects laterally outwardly of said arm. Conveniently, the reservoir connector means is shaped to accommodate an annular sealing element in such a manner that the element seals between respective opposing surfaces of the reservoir connector means and said socket. Preferably, the reservoir, its connector means and the flexible catch means are integrally moulded. The invention will now be described, by way of example, with reference to the accompanying drawings in which:- Figure 1 is a side view, partly in cross-section, of one form of master cylinder reservoir of the invention and including, for the purpose of illustration, two alternative forms of connector means respectively at the right and left hand sides thereof; Figure 2 is an enlarged detail of the left hand connector means of Figure 1; Figure 3 is an enlarged detail of the right hand connector means of Figure 1; Figure 4 is a view similar to Figures 2 and 3 illustrating a further alternative embodiment of reservoir connector means, and Figure 5 illustrates futher alternative forms of connector means respectively at the right and left hand sides thereof. Referring to Figure 1, this illustrates a master cylinder reservoir which has a container 1 having, in an upper region thereof, a filler neck 2 closed by a screw closure cap 3. In this particular embodiment, the cap 3 carries a liquid level indicator 4 of which an electrical connection is indicated at 5. The container 1 is provided on its undersurface with a pair of port connectors 6 and 7 and whilst these would normally be identical on a single container, two alternative forms of connection are shown in Figure 1 for convenience of illustration. Figure 2 illustrates, to a larger scale, part of the reservoir container 1 assembled by way of the connector 6 on a pressure cylinder 8. The connector 6 comprises a central hollow cylindrical spigot 9 extending from the base of the reservoir and forming a passage 10 which communicates with a radial port 11 through the cylinder wall to place in communication the respective interiors of the reservoir 1 and cylinder 8. The cylinder 8 has a socket 9A for receiving the spigot 9 in the manner to be described. The free extremity of the spigot 9 is formed with a generally radial flange formation 12, the extreme end portion 12A of the outer periphery of which is reduced in diameter to carry an annular seal 13. The portion 12A may have a peripheral groove 12B to aid retention of the seal thereon. A pair of diametrically opposed arms 14, 15 extend from the underside of the reservoir in generally parallel relationship with and towards the free end of the spigot 9, each arm having a circumferential extent of, typically, approximately 50°. The external surface of each arm is stepped to form a shoulder 14A, 15A facing the base of the reservoir, and the entrance to the socket 9A is surrounded by an internally projecting flange 8A for co-operation with the shoulders 14A, 15A. A free end portion of each arm has an inwardly tapered outer surface 14C, 14D for the purpose to be described. In order to assemble the reservoir 1 on to the cylinder 8, the reservoir connectors, which it will be assumed are both of the type designated 6, are offered to their respective cylinder sockets 9A. The distance between the radially outermost surfaces of the arms in their relaxed state is greater than the diameter of the internal radially facing surface of the cylinder flange 8A, but as the arms are forced into the sockets, they are resiliently deflected inwardly, aided by the action of the inclined end portions 14C, 14D, until the arms reach the position shown, at which time they resiliently recover outwardly to snap-engage behind the shoulders 14A, 15A of the flange 8A. This provides a very effective axial retention of the reservoir relative to the cylinder. Prior to the assembly process, the sealing ring 13 is placed in position in the groove 12B around the smaller diameter portion of the spigot. As the reservoir connection is pushed into its socket, the seal 13 engages an internal cylindrical surface 8B of the socket and is compressed to form a fluid-tight seal between the flange 12 and surface 8B, the spigot being afforded axial guidance and support by engagement of the flange 12 with the surface 8B. It is possible to withdraw the connections 6 from their sockets by applying an inward force to the arms 14, 15 at their exposed upper ends in order to deform the arms inwardly and disengage the shoulders 14A, 15A from the flange 8A. The alternative embodiment illustrated in Figure 3 is essentially similar in principal to that of Figure 2 and represents the connection designated 7 in Figure 1. The main difference is that the arms 14′, 15′ are connected to the outermost end portion of the cylindrical portion 9 so that the free end portions of the arms are adjacent the base of the reservoir. A seal 13′ is arranged in a manner substantially similar to the seal 13 of Figure 2 to provide a fluid-tight seal between the reservoir connection and socket wall. In this embodiment, the upper exposed extremities of the arms 14′, 15′ are provided with lateral extensions in the form of tongues 16 which may be manipulated from the exterior in order to retract the tongues inwardly to permit removal of the reservoir from the cylinder. In both of the embodiments of Figures 2 and 3, the wall of the socket adjacent the final positions of the seals may be slightly inwardly recessed at 13A and 13A′ to provide additional retention for the seals. The reservoir, of which part is illustrated in Figure 4, is designed for use with a cylinder having projecting spigots 20 in place of the sockets described above. The spigot 20 has a reduced diameter portion at its inner end forming a shoulder 21 behind which engage claws 22 at the end of diametrically opposed arms 23, 24, which, in this arrangement, extend from the axially outermost extremity of a cylindrical spigot 9′ having a port 9″ therethrough. The inwardly facing surfaces 25 of the arms are bevelled and the distance between the outer ends of the arms is smaller than the diameter of the spigot 20 so that the arms are resiliently outwardly expanded, as described above, when the reservoir is pressed onto the spigots 20, the arms subsequently resiliently recovering to snap engage behind the shoulder 21. In this embodiment, a groove 26 is formed in the end of the cylindrical 9′ and receives a seal 27 which, during assembly, is compressed against the facing upper end of the spigot 20 to form a fluid-tight seal between the reservoir and cylinder. In the alternative embodiment shown in Figure 5, the invention is shown applied to a fabricated master cylinder having a thin-walled pressure cylinder 30 provided with port connectors 31, 32 secured to the cylinder, preferably by welding. The right-hand connector means 7 is similar to that shown in Figure 3 and has a pair of arms 33, 34 of which shoulders 33A and 34A snap-engage behind shoulders 35 of the port connector 32. The shoulders 35 are formed by turning inwardly the outer peripheral extremities of the ports. An annular seal 36 is compressed between the underside of the connector means and the base of the port connector. This connector means 33 is assembled to the port connector 32 in the manner described previously. The left-hand connector means 6 has only a single arm 34 co-acting with a shoulder 35, in the manner already described. The wall of the port connector 31 is apertured at 37 to receive a flexible elbow 38, as of rubber or plastics for example. One arm 38A of the elbow engages within a hollow spigot 6A of the connector means 6 and the other arm 38B of the elbow extends outwardly through the aperture 37 and reveives a tubular member 39 extending from an end closure member (not shown) of the cylinder. The elbow 38 may either be inserted through the aperture 37 and the spigot 6A connected to the arm 38A within the port connector, or the elbow may be connected to the spigot 6A prior to assembly of the reservior on the cylinder, and the arm 38B fed through the aperture 37 for subsequent connection to the tubular member 39. For the latter assembly method, it may be necessary to elongate the aperture 37 in a direction radially of the cylinder 30. It will be understood that any convenient number of arms may be used instead of the two shown in each of the above described embodiments and the shapes of the arms may be modified, as required, whilst still retaining the snap-engaging function described above. The cross-section of the seals 13, 13′, 27 may, if required, be increased in size to ensure sealing even in the event of any slight relative movement between the reservoir and pressure cylinder. The reservoir may readily be formed as a single injection or blow moulding and can therefore be rapidly and conveniently manufactured and readily assembled onto a pressure cylinder during manufacture on a production line.

Claims: 1. A master cylinder comprising a hydraulic fluid reservoir having a container (1) and at least one connector means (6) engaged with port means (9A) of a pressure cylinder (8), said reservoir having a flexible arm (14) provided with catch means (14A) snap-engaged with a retaining formation of said pressure cylinder in order to retain the reservoir in an operative position on the cylinder, characterised in that the flexible arm (14, 15) forms part of the connector means (6) and the retaining formation (8A) of the pressure cylinder is carried by the port means (9A). 2. A master cylinder according to Claim 1, characterised in that each said arm (14, 15) lies generally parallel to and externally of a projecting hollow spigot connector (9) of the reservoir extending within said cylinder port means (9A) and communicating with a port (11) of the cylinder. 3. A master cylinder according to Claim 1 or Claim 2, characterised in that each said shoulder projects laterally outwardly of said arm. 4. A master cylinder according to any one of the preceding claims, characterised in that each connector means (6, 7) is shaped to accommodate an annular sealing element (13) sealing between respective opposing surfaces of the reservoir connector means and said port means (9A). 5. A master cylinder according to any one of Claims 2 to 4, characterised in that each arm (14, 15) is connected to the reservoir adjacent the container (1) and extends away from the latter. 6. A master cylinder according to any one of Claims 2 to 4, characterised in that each arm (14′, 15′) is connected to the connector means at a location remote from the container and extends towards the latter, the free end of each arm lying outwardly of the cylinder port means (9A) and being provided with a lateral extension (16) which may be manipulated from the exterior to retract the arm inwardly to permit removal of the reservoir from the cylinder. 7. A master cylinder according to any one of Claims 1 to 5, characterised in that the cylinder port means forms a spigot (20) and each arm (23, 24) extends externally of the spigot to engage a retaining formation (21) of the spigot. 8. A master cylinder according to Claim 1, characterised in that each arm (23, 24) extends beyond and generally parallel to a projecting hollow spigot connector (9′) of the reservoir having a port (9″) therethrough, a seal element surrounding said port (9″) and engaging opposed axially facing surfaces of the spigot connector (9′) and cylinder port means (20). 9. A master cylinder according to any one of the preceding claims, characterised in that the reservoir, its connector means and the flexible catch means are integrally moulded. 10. A master cylinder according to any one of the preceding claims, characterised in that the pressure cylinder (8) is provided with at least one separately made port connector (31, 32) secured thereto and a shoulder (35) is formed on each connector by turning over inwardly the outer extremity thereof 11. A master cylinder according to any one of Claims 1 to 9, characterised in that the pressure cylinder (8) is provided with at least one separately made port connector (31, 32) secured thereto, said connector being apertured to receive an elbow (38) of which one arm (38A) is received within a hollow spigot (6A) of the reservoir and the other arm (38B) projects outwardly of the port connector for connection to a hollow element (39).

Inventors: CUNNINGHAM, PHILIP
Applicants: LUCAS INDUSTRIES PUBLIC LIMITED COMPANY
Application year: 1988
Main classification: B60T11
IPC codes: B60T11