WO1987003344A1

WO1987003344A1 - Fluid pressure system and actuator therefor

Info

Publication number: WO1987003344A1
Application number: PCT/AU1986/000367
Authority: WO
Inventors: Vincent Joseph Keane
Original assignee: Brake And Clutch Industries Australia Pty. Ltd.
Priority date: 1985-11-26
Filing date: 1986-11-26
Publication date: 1987-06-04
Also published as: EP0247096A1

Abstract

A cylinder for use in a fluid pressure system having a body composed of an outer shell (9) and an inner sleeve (18), both of which are formed of a plastics material. The sleeve is relatively short as compared with the shell so that at least part of the pressure chamber (29) of the cylinder is formed by the shell alone. A piston (25) slidably located in the sleeve may be also formed of a plastics material. An actuator for a fluid pressure system may include a master cylinder constructed in the foregoing manner and that actuator comprises a pivotally mounted lever or arm with the master cylinder attached so as to move with that lever or arm. Control means cooperates with a push rod of the master cylinder so that the master cylinder piston moves in response to pivotal movement of the lever or arm. A two-part coupling having at least one frangible diaphragm is used in a connection between the master cylinder pressure chamber and another component so that the master cylinder and that component can be pre-filled with fluid prior to interconnection. When the two parts of the coupling are brought together, a probe of one part punctures the diaphragm of the other and thereby interconnects the relevant components.

Description

"FLUID PRESSURE SYSTEM AND ACTUATOR THEREFOR" This invention relates to fluid pressure systems such as

J vehicle clutch and brake systems and also to actuators for such systems. As a matter of convenience the invention will 5 be hereinafter described with particular reference to hydraulically controlled vehicle clutch systems.

A typical hydraulically actuated clutch system includes a master cylinder which is connected to a hydraulic fluid reservoir and the vehicle clutch foot pedal, and a slave 0 cylinder which is connected to the master cylinder and the clutch assembly. Depression of the foot pedal causes the master cylinder to drive pressurised fluid into the slave cylinder which responds by operating the associated clutch assembly. Both the master and slave cylinders are generally 5 made of metal as are various related components such as the cylinder push rods. Metal components/ and particularly metal cylinder bodies, are expensive to manufacture and that contributes significantly to the cost of such fluid systems.

Another difficulty with the foregoing arrangement is

20 that the master cylinder needs to be mounted on the vehicle fire wall or at some other appropriate location with sufficient rigidity to react the forces to which it is subjected when in use. That is, proper operation of the

•\ clutch system demands that the master cylinder body be held

25 against deflection when subjected to operating forces. Still another problem is that the master cylinder occupies a substantial amount of space.

It is an object of the invention according to one aspect to provide a fluid actuated system which is relatively

30 inexpensive to manufacture and which is simple to install. It is a further object of the invention to provide an improved cylinder construction for use in such a system.

It is an object of the present invention according to another aspect to provide a fluid pressure system actuator which avoids the mounting and space requirement difficulties referred to above. It is another object of the invention to provide a fluid system actuator which can be conveniently arranged to provide output displacement and/or pressure characteristics to suit particular requirements. According to one aspect of the present invention, there is provided a cylinder for use in a fluid pressure system including, a body having two parts, each of which is formed of a plastics material, one said part comprising an outer shell having an opening and an end wall at respective opposite ends thereof, the other said part comprising an inner sleeve which is neatly located within said shell so as to extend from said open end towards said end wall, the end of said sleeve remote from said open end being located in spaced relationship from said end wall, a cylindrical bore formed in said sleeve, a piston slidably located within said bore for movement towards and away from said end wall, sealing means engaging around said piston and being captured between said sleeve inner end and an opposed surface of said shell, and a pressure chamber formed between said end wall and said piston. According to a further aspect of the invention, there is provided a cylinder for use in a fluid pressure system including, a body having an outer shell and an inner sleeve, said outer shell containing at least a substantial part of said inner sleeve in close fitting relationship, said inner sleeve being formed of a relatively hard plastics material. said outer shell being formed of a plastics material which is selected to suit the environment of use of said cylinder, a i cylindrical bore formed within said inner sleeve, and a piston slidably located within said bore. 5 According to yet another aspect of the invention, there is provided an actuator for use in a fluid pressure system including, an arm arranged for movement about a pivot axis, a cylinder body attached to or formed integral with said arm so as to be movable with said arm about said pivot axis, a io cylindrical bore within said body and having its axis extending transverse to said pivot axis, a piston slidably mounted within said bore for axial movement relative to said body, a pressure chamber formed within said body between said piston and a transverse wall of said body, a push rod

15 connected to said piston for movement therewith and extending axially out of said body through an end thereof remote from said transverse wall, and control means cooperating with said push rod so as to be operative to cause said piston to move towards said transverse wall in response to pivotal movement

20 of said arm in one direction.

According to still another aspect of the invention, there is provided a coupling for use in a fluid system including a male part and a female part, a passage within each s said part, said female part having a frangible diaphragm- which

25 is arranged to prevent flow of fluid through the female part passage, and said male part having a probe which is insertable into said female part and is adapted to penetrate through said diaphragm in the course of said insertion so as to thereby provide communication between the two said passages, the

30 arrangement being such that said probe penetrates through said diaphragm when the two parts are in cooperative engagement and the penetrated diaphragm is thereby flexibly distorted to sealingly engage against an outer surface of said probe.

Embodiments of the invention are described in detail in the following passages of the specificaton which refer to the accompanying drawings. The drawings, however, are merely illustrative of how the invention might be put into effect, so that the specific form and arrangement of the various features as shown is not to be understood as limiting on the invention. In the drawings:

Figure 1 is a diagrammatic view of one form of fluid pressure system incorporating an embodiment of the invention,

Figure 2 is a cross-sectional view of a master cylinder as shown in the system of Figure 1, Figure 3 is a cross-sectional view of a slave cylinder as shown in the system of Figure 1,

Figure 4 is a diagrammatic view of yet another fluid pressure system incorporating another embodiment of the invention, Figure 5 is a cross-sectional view of the foot pedal shown in the system of Figure 4,

Figure 6 is a front elevational and partially sectioned view of the foot pedal of Figure 5,

Figure 7 is a view similar to Figure 5 but showing the foot pedal depressed,

Figure 8 is an enlarged cross-sectional view of the conduit coupling shown in the system of Figure 4,

Figure 9 shows the coupling of Figure 8 in the separated and ready to use condition. Figure 10 is a cross-sectional view of portion of a cylinder in accordance with another embodiment of the invention.

, The system shown in Figure 1 is a typical fluid pressure system as used in relation to vehicle clutches. It includes a 5 master cylinder 1, a slave cylinder 2, a fluid reservoir 3, and a foot pedal 4. The cylinders 1 and 2 are interconnected through a conduit 5 so that actuation of the master cylinder 1 causes movement of the push rod 6 of the slave cylinder 2, and an associated clutch (not shown) responds to that movement. io Actuation of the foot pedal 4 causes actuation of the master cylinder 1 through the push rod 7. The reservoir 3 is connected to the master cylinder 1 so as to make-up for any fluid losses which might occur in the system, and it can be located remote as shown or it can be mounted directly on the

15 body of the cylinder 1. Both the master cylinder 1 and foot pedal 4 are usually mounted on the vehicle fire wall 8 as shown.

In the system shown, the body of each cylinder 1 and 2 is composed of two main parts - an inner sleeve and an outer

20 shell - both of which are composed of a plastics material. By way of example, the inner sleeve may be composed of a material such as "Celcon" and the outer shell may be composed of a glass-filled nylon. A piston is slidably mounted in each _t cylinder body and that may be formed of a material such as

25 "Delrin", and each cylinder also includes a push rod which may be formed of "Celcon" or other relatively hard and form stable plastics material.

Figure 2 shows the master cylinder 1 constructed in the foregoing manner. The outer shell 9 of the master cylinder

30 body is generally of tubular form and that shell may have a plurality of longitudinally and transversely extending ribs 10 on its outer surface. Such ribs 10 serve to strengthen the shell 9 so that its basic wall thickness may be kept to a minimum. In an example form of the master cylinder 1 as shown, the outer shell 9 is generally cylindrical, has an opening 11 at one end and has an end wall 12 substantially closing the opposite end. A mounting flange 13 is arranged around the open end and a tube connecting nipple 14 projects axially outwards from the end wall 12. A communication passage 15 extends axially through that nipple 14 and the end wall 12. The cylinder 1 may be connected directly to the reservoir 3 or connected through a tube 16 to a remotely located reservoir 3 as shown. In either case appropriate connecting means 17 can be formed integral with the outer shell 9.

The inner sleeve 18 of the master cylinder shown is also a generally cylindrical tubular member, but that member is open at both ends. In the example construction shown, a substantial part of the sleeve 18 is located neatly within the outer shell 9 and an outer end portion 19 of the sleeve 18 projects axially beyond the open end of the shell 9. The inner end 20 of the sleeve 18 terminates short of an internal shoulder 21 formed within the outer shell 9 and sealing means 22 is disposed between that shoulder 21 and the adjacent sleeve end 20. Retention of the sleeve 18 within the outer shell 9 may be effected by snap engagement between those members. In the example shown, a bead 23 extending around the outer surface of the sleeve 18 snap engages within a corresponding groove 24 formed within the inner surface of the shell 9 .

As will be seen from Figure 2, the sleeve end 20 is spaced axially from the end wall 12. The sleeve 18 is therefore substantially shorter in axial length than the outer s shell 9, and that is one of the consequences of forming the two cylinder parts 9 and 18 and the piston 25 of a plastics material. The piston 25 is the only one of the three components which requires critical manufacturing tolerances, and it is not necessary to support that piston over its entire 0 length during its movement through the sleeve 18.

Sealing means 22 as referred to above may include a pair of annular flexible seals 26 of appropriate shape and material and a spacer ring 27 located between those seals 26. The spacer ring 27 could be composed of a plastics material such 5 as "Celcon" and is preferably located at the region of the outer shell 9 through which communication is made with the reservoir 3. Transfer passages 28 are formed through the spacer ring 27, and possibly the piston 25 also, whereby fluid from the reservoir 3 can reach the pressure chamber 29 of the 0 master cylinder 1. That chamber 29 is defined in a space between the piston 25 and the end wall 12 of the outer shell 9.

An inlet passage 30 formed through the side wall of the shell 9 provides means whereby fluid from the reservoir 3 can enter the body of the cylinder 1. The passage 30 is in J5 communication with the transfer passages 28 and fluid can pass from those passages 28 through a clearance space (not shown) between the spacer ring 27 and the piston 25. Short longitudinally extending grooves 31 formed in the outer surface of the piston 25 at its inner end 20 then provide space into the pressure chamber 29. When the piston 25 is moved towards the end wall 12, that communication is closed as a consequence of a non-grooved surface of the piston 25 being located at each of the seals 26. The piston 25 of the master cylinder 1 is also a cylindrical member which is slidably mounted within the bore 31 of the inner sleeve 18. A coil compression spring 32 or other biasing means may be arranged to urge the piston 25 away from the end wall 12 of the outer shell 9. The piston may be formed of a tubular section 33 which is open at one end 34 and closed at the other by a transverse wall 35 as shown. The spring 32 extends into the tubular section 33 so that one end of the spring 32 engages against the transverse wall 35 and the other end of the spring 32 engages against the end wall 12 of the outer shell 9. Stop means such as internal shoulder 37 in the bore 31 of the inner sleeve 18 may be provided for engagement by the piston 25 so as to limit movement of the piston 25 away from the outer shell end wall 12.

The push rod 7 extends axially through the open end of the cylinder body and has one end connected to the piston 25. That connection may be a snap connection and in the arrangement shown includes an enlargement 38 on the end of the push rod 7 which snap engages within a complementary cavity 39 in the transverse wall 35 of the piston 25. The snap engagement may be effected, by a lip 40 which is integral with the piston 25 and surrounds the open mouth of the cavity 39 so as to effectively reduce the size of that mouth. The lip 40 is sufficiently flexible to allow the push rod enlargement 38 to be forced through the reduced mouth. In the installed condition of the push rod 7, the lip 40 locates behind the rod enlargement 38 so as to resist separation of the push rod 7 and piston 25.

A flexible sealing boot 41 may be provided at the open end of the cylinder body so as to effectively close that end.

" 5 The boot 41 may locate over and snap engage with the outer end portion 19 of the sleeve 18 and has an axial opening 42 which neatly surrounds the push rod 7 to provide something of a seal.

Connecting means 43 may be provided at the outer end of the push rod 7 for connecting the rod 7 to the clutch pedal ιo 4. That connecting means 43 may comprise a ring 44 which is integral with the outer end of the push rod 7 and is arranged with its axis transverse to the rod axis. In the form shown, a plurality of integral and flexible lugs 45 project radially inwardly from the inner surface of the ring 44 to provide

15 retention lugs which are operable to snap engage within a circumferential groove (not shown) of a connecting pin 46 (Figure 1) attached to the clutch pedal 4.

As will be apparent from Figure 3, the slave cylinder 2 may be constructed substantially the same as the master

20 cylinder 1 as described above, but there is no need for a connection to the reservoir 3 as in the case of the master cylinder 1. In particular, the slave cylinder 2 includes a body composed of an outer shell 47 and an inner sleeve 48 which can be formed and arranged in the manner described in

_*

25 connection with the master cylinder 1. A piston 49 slides within the bore 50 of the sleeve 48 and is connected to the push rod 6, preferably in the manner also described in connection with the master cylinder 1. In this case, however, the piston 49 has an additional tubular section 36 which

30 extends from the transverse wall 51 in a direction away from the cylinder body end wall 52.

A bleeder valve 53 of known construction and operation may be provided adjacent the end wall 52 of the slave cylinder body. Also, the sealing means 54 between the inner sleeve 48 and the outer shell 47 may comprise a single annular seal. Still further, there is generally no need for a connecting ring as described in connection with the master cylinder 1, but a part-spherical enlargement 55 may be provided at that end to serve as an abutment for engagement with the clutch fork (not shown) .

It will be apparent from the foregoing description that each cylinder can be manufactured at a much lower cost than conventional metal cylinders. Also, in the case of the master cylinder in particular, the improved construction requires a substantially smaller number of components. The materials for the shell and sleeve of the cylinder bodies can be selected to suit requirements. The sleeve will usually be of a relatively hard and wear resistant plastics material, and the material of the shell may be selected to suit the use environment of the cylinder. For example, in vehicle applications, it may be desirable to form the shell of a plastics material which is resistant to battery acid.

Figure 4 shows, in diagrammatic form, another fluid pressure system to which a further embodiment of the invention is applied. Components of this system which correspond to components described in connection with Figures 1 to 3 will be given like reference numerals, but they will be in the number series 100 to 199.

The system of Figure 4 includes a master cylinder 101, a slave cylinder 102, a reservoir 103, and a foot pedal 104. The cylinder 102 and reservoir 103 are connected to the master cylinder 101 through respective conduits 105 and 116, and the master cylinder 101 and the foot pedal 104 are mounted on a vehicle fire wall 108. As in the previous case, this embodiment will be described in relation to a vehicle clutch system, but it has other applications.

It is a feature of the particular system shown by Figure 4 that the master cylinder 101 is attached to or formed integral with the foot pedal 104 so as to move with that foot pedal 104. The master cylinder 101 and foot pedal 104 therefore form a composite actuator 156 for the system. The foot pedal 104 may be of the usual form having an arm 157 which is pivotally connected to a support structure 158 at one end and has a foot engageable pad 159 at its opposite end. Operation of the clutch system is effected by pressing against the pedal pad 159 so as to cause the pedal arm 157 to swing inwards about its pivotal mounting 160. The master cylinder 101 is arranged to respond to that inward pivotal movement in a manner such as to cause operation of the associated clutch (not shown) .

The body 109 of the master cylinder 101 could be formed integral with the clutch pedal arm 157 and for that purpose both the cylinder body 109 and the pedal arm 157 may be moulded or otherwise formed from a suitable plastics material. Figure 5 shows an alternative arrangement in which the cylinder body is separately formed and is attached to the pedal arm 157 in a suitable manner such as through snap engagement. In either arrangement it is preferred that the cylinder 101 is disposed within the pedal arm 157 rather than being mounted on a side of that arm 157. According to the example of Figures 5 to 7, at least part of the arm 157 is of channel shape and thereby defines a recess 161 within which the cylinder body 109 is located.

The general construction of the master cylinder 101 may be substantially as described in relation to Figure 2. A fluid reservoir for the master cylinder 101 may be connected to or formed integral with the foot pedal 104, but it is generally preferred to locate that reservoir 103 remote from the pedal 104 and connect it to the master cylinder 101 through a suitable flexible connection 116 as shown. A similar flexible connection 116 may be provided between the master cylinder 101 and the slave cylinder 102, which can be constructed substantially as described in connection with Figure 3. As seen in Figure 5, the master cylinder 101 includes a piston 125 slidably mounted within a cylindrical bore 131 of the cylinder body 109, and a push rod 107 connected to that piston 125 and projecting axially through an end of the cylinder body 109. A pressure chamber 129 is formed within the cylinder body 109 between the end wall 112 thereof and the piston 125, and the size of that chamber 129 will of course vary according to movement of the piston 125 within the cylinder body 109. The pressure chamber 129 is connected to both the reservoir 103 and the slave cylinder 102. A spring 132 may act on the piston 125 so as to normally urge it in a direction away from the end wall 112 of the cylinder body 109 to thereby enlarge the pressure chamber 129.

The push rod 107 is arranged to respond to inward pivotal movement of the foot pedal 104 so as to push the piston 125 towards the cylinder body end wall 112 and thereby pressurise hydraulic fluid contained within the pressure chamber 129. That pressurised fluid causes operation of the slave cylinder 102 in a known manner. Such response of the

* push rod 107 can be effected in a variety of ways through

5 suitable control means 162. v.

In the particular arrangement shown, the control means 162 includes cam means which controls axial movement of the push rod 107 in accordance with pivotal movement of the foot pedal 104. Alternatively, the control means 162 may include a 0 linkage system which achieves substantially the same result. According to the arrangement shown, the push rod 107 extends generally in the longitudinal direction of the foot pedal arm 157 and has its outer end 163 located adjacent the pivotal mounting 160 of that arm 157. Since the master cylinder body 5 109 is secured to that arm 157, both that body 109 and the associated push rod 107 swing with the arm 157 during its movement about its pivotal mounting 160. The axis of the pivotal mounting 160 extends transverse to the longitudinal axis of the push rod 107. 0 Cam means which has been found satisfactory includes a cam member 164 which may be secured to the same structure 158 as that supporting the foot pedal 104 and has a suitably profiled cam surface 165. A cam follower, such as a roller 166, is mounted on the outer end 163 of the push rod 107 and 5 the arrangement is such that the roller 166 engages and tracks along the cam surface 165 during at least a substantial part of the available pivotal movement of the clutch pedal 104.

The cam surface 165 is profiled and arranged relative to the foot pedal 104 so that the push rod 107 is caused to move 0 axially inwards relative to the cylinder body 109 as the foot pedal 104 is swung inwards about its pivotal mounting 160. It will be evident from Figure 7 that during such movement of the foot pedal 104, the push rod roller 166 travels along the cam surface 165 and because of that travel it is forced to progressively move further towards the end wall 112 of the cylinder body 109. The master cylinder piston 125 naturally follows that movement of the roller 166 and consequently pressurises fluid within the pressure chamber 129.

As shown in Figure 5, a slide block 167 may be provided at the outer end 163 of the push rod 107 and arranged to slidably engage a surface 168 of the pedal arm 157. Such an arrangement assists in guiding the movement of the push rod 107 and supports the rod 107 against deflection arising out of the reaction between the roller 166 and the surface 165. When foot pressure on the clutch pedal 104 is removed or reduced, that pedal 104 returns towards its original position as in conventional clutch systems. Such return movement may be due solely to the reaction occurring between the cam surface 165 and the engaging roller 166 because of spring and/or fluid pressure acting on the master cylinder piston 125. Alternatively, additional biasing means may be connected to the pedal 104 to augment the returning influence of the master cylinder 101. Such return movement of the pedal 104 naturally causes enlargement of the pressure chamber 129 so that the clutch is released from the influence of the slave cylinder 102.

With the above arrangement it is generally convenient to have the cam member 164 positioned to intrude into the recess 161 of the foot pedal arm 157. It will be appreciated that the profile of the cam surface 165 can be predetermined so as to achieve any desired fluid displacement and/or pressure- characteristics for the pressure chamber 129. That aspect can be of value in providing improved clutch feel and/or travel, and/or to provide optimum user control for smooth clutch operation. Furthermore, the incorporation of the master cylinder 101 within the foot pedal 104 results in a saving of space which can be of substantial advantage in some circumstances.

According to another aspect of the invention which has particular application to the actuator 156 described, but has other uses, there is provided an improved method of connecting the actuator 156 into a hydraulic system. The improved method, when applied to the actuator 156, enables that actuator 156 to be supplied to an end user in a ready to use form to the extent that it is adapted for connection to other components such as a reservoir 103 and slave cylinder 102 to form a sub-system for inclusion in a vehicle clutch system. Also, the components of that sub-system can be preconditioned for use in that they can be prefilled with hydraulic fluid and pre-bled of air before supply to the end user.

In a particular form of this further aspect as shown by Figures 4, 5, 8 and 9, the foot pedal actuator 156 is connectable to a fire wall 108 or other support of a vehicle through a mounting bracket 169. That bracket 169 may include or have secured thereto the cam member 164 as previously described and is pivotally connected to the pedal arm 157 in a suitable manner. Flexible conduits 116 and 105 connecting the master cylinder 101 to the reservoir 103 and slave cylinder 102 respectively preferably extend through the bracket 169 as hereinafter described in detail. As shown in Figure 5, a base 170 of the bracket 169 is preferably arranged for engagement against a surface of the vehicle fire wall 108 and any suitable means can be adopted to secure the base 170 against separation from that wall 108. In the example shown, the base 170 includes at least one hollow or tubular stud 171 which can snap engage within or through a hole in the vehicle fire wall 108. A pin 172 may be then driven into the body of the stud 171 to hold it in a radially expanded condition such as to resist its withdrawal from the hole. The base 170 of the bracket 169, the stud 171 and the pin 172 could be formed as integral parts by moulding from a plastics material in which event the pin 172 is preferably connected to the base 170 through a frangible connection and is located in axial alignment with the stud 171. The flexible conduit 116 between the reservoir 103 and the master cylinder 101 may pass directly through the base 170 and may be removably connected to the reservoir 103 and/or master cylinder 101 for a reason hereinafter discussed. The conduit 105 between the master cylinder 101 and the slave cylinder 102, however, is preferably formed of two parts 105a and 105b which are connectable through a make and break coupling 173 located at or adjacent the base 170 of the bracket 169. It is a feature of the coupling 173 that it enables temporary separation of the two conduit parts 105a and 105b without allowing substantial egress of hydraulic fluid or ingress of air. As a matter of convenience the conduit part 105a connected to the master cylinder 101 will be referred to as the inner part 105a and the other part will be referred to as the outer part 105b. In the particular form shown by Figures 8 and 9, the coupling 173 includes a fixed or female part 174 and a movable or male part 175, and the former is preferably attached to the base 170 of the bracket 169 so as to project from the side thereof remote from the master cylinder 101. The fixed part 174 may have a cylindrical body 176 and a tubular nipple 177 projecting axially from one end of that body 176. Attachment of the fixed part 174 to the base 170 may be achieved by inserting the nipple 177 into an end portion of the conduit inner part 105a which is located within a through hole 178 in the base 170. Both the conduit end portion 105a and the nipple 177 may be retained in their respective positions by frictional engagement, and in that regard the nipple 177 may cause radial expansion of the conduit end portion to secure it firmly within the hole 178 of the base 170. An axial bore 179 (Figure 9) extends into the fixed coupling part 174 through the end of that part 174 remote 'from the nipple 177 and an internal passage 180 connects that bore 179 with the interior of the nipple 177. A tubular probe 181 projects axially into the bore 179 from the end thereof adjacent the nipple 177 and that probe 181 contains at least part of the passage 180. The probe 181 projects towards the open mouth of the bore 179 and an annular clearance space 182 (Figure 9) exists between it and the surrounding bore surface. Furthermore, the probe 181 may be formed integral with the body 176 of the fixed part 174.

Closure means is provided over the open mouth of the bore 179 and that takes the form of a rubber or other flexible diaphragm 183 which is snap-engaged or otherwise attached to the respective end of the fixed part body 176. In the example shown, the diaphragm 183 forms part of a cap 184 which snaps over the end of the fixed part body 176. It is preferred that the diaphragm 183 is adapted to be broken or punctured as hereinafter described and for that purpose it may have one or more zones or lines of weakness (not shown) . The movable part 175 of the coupling 173 may have a form similar to that of the fixed part 174. That is, it may include a cylindrical body 185 having an axial bore 186 (Figure 9) in one end and a nipple 187 projecting axially from the other end for connection to the outer part 105b of the conduit. A probe 188 is also included and that will be hereinafter called the outer probe, whereas the probe 181 of the fixed part 174 will be called the inner probe. Means is provided for closing a passage 189 through the outer probe 188 and that preferably comprises an internal frangible diaphragm wall 190 which is located within that passage 189 at a position spaced axially from the terminal end 191 of the probe 188. The bore 186 of the movable part 175 is dimensioned to receive the body 176 of the fixed part 174 as shown in Figure 8, and preferably slidably engage with portion of the cap 184 so as to create a seal between the two parts 174 and 175. The outer probe 188 is dimensioned to fit within the bore 179 of the fixed part 174 and the inner probe 181 is dimensioned to fit within the passage 189 through the outer probe 188.

The arrangement is such that when the two coupling parts 174 and 175 are being moved into cooperative engagement as shown in Figure 8, the terminal end 191 of the outer probe 188 engages the diaphragm 183 of the fixed part 174 subsequent to the body 176 of that part 174 being received in the bore 186 of the movable part 175. Continued movement of the movable part 175 over the fixed part 174 causes the outer probe 188 to break through the diaphragm 183 and the inner probe 181 breaks through the diaphragm wall 190 of the outer probe 188, preferably at a subsequent stage in that movement. After each probe 188 and 181 breaks through its respective diaphragm 183 and 190, the body of that diaphragm is flexibly distorted to form a cylindrical lip or sleeve which bears against the outer surface of the respective probe to form a fluid tight seal (see Figure 8) . It will be understood that rupture of the diaphragms 183 and 190 results in the interconnection of the two probe passages 180 and 189 and consequently interconnection of the two parts 105a and 105b of the conduit to which the coupling 173 is connected.

A spring clip 192 (Figure 8) or other releasable fastener may be provided to hold the two coupling parts 174 and 175 in the fully connected condition.

As previously stated, the sub-assembly components namely, the master cylinder 101, slave cylinder 102 and reservoir 103 - can each be supplied to the end user in a pre-filled condition. In the as-supplied condition, each of the two cylinders 101 and 102 will have connected thereto a respective part of the two-part conduit 105 and each of those conduit parts terminates in a respective part 174 and 175 of the coupling 173. The diaphragm 183 and 190 of each coupling part is intact in the as-supplied condition and thereby prevents egress of hydraulic fluid.

When the sub-system of which the components form part is being installed in a vehicle, the two coupling parts 174 and 175 are joined as previously described so as to rupture the two diaphragms 183 and 190 and thereby establish a working interconnection between the two cylinders 101 and 102. A coupling 173 as described may be also provided in the conduit 116 between the master cylinder 101 and the reservoir 103, but that is not usually necessary. It is generally possible to disconnect one end of that conduit 116 without substantial loss of fluid for the purpose of installing the sub-system in a vehicle.

A coupling as described has the potential to provide substantial advantages when used in a fluid system of any kind, but it is particularly useful in a hydraulic system such as used in relation to brakes and clutches. When the coupling is used in a clutch system as described, it adds substantially to the convenience of installing the master cylinder, particularly because of the ability to preload that cylinder with hydraulic fluid. Figure 10 shows part only of a modified form of cylinder

200 which could be used in any one of the embodiments previously described. That cylinder 200 includes a shell 209 and a sleeve 218, each of which is formed of a suitable plastics material. The sleeve 218 is reduced in diameter between its ends to provide a clearance space 2^'93 between it and the shell 209 so that contact with the shell occurs at two axially spaced land portions 294.

The push rod enlargement 238 is substantially spherical and snap engages in a substantially complementary cavity of the piston 225 as in the prior embodiments. A circumferential flange 295 is provided on the push rod 207 adjacent the enlargement 238 and abuts against an opposed shoulder 296 provided within the sleeve 218. The push rod 107 is thereby securely captured against separation from the cylinder body. Various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention as defined by the appended claims.

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Claims

CLAIMS :

1. A cylinder for use in a fluid pressure system including, a body having two parts, each of which is formed of a plastics material, one said part comprising an outer shell having an opening and an end wall at respective opposite ends thereof, the other said part comprising an inner sleeve which is neatly located within said shell so as to extend from said open end towards said end wall, the end of said sleeve remote from said open end being located in spaced relationship from said end wall, a cylindrical bore formed in said sleeve, a piston slidably located within said bore for movement towards and away from said end wall, sealing means engaging around said piston and being captured between said sleeve inner end and an opposed surface of said shell, and a pressure chamber formed between said end wall and said piston.

2. A cylinder according to claim 1, wherein a push rod extends axially through the end of said sleeve remote from said end wall, and snap engaging means releasably connects an end of said rod to said piston.

3. A cylinder according to claim 2, wherein said snap engaging means includes an enlargement at said rod end, a cavity within said piston which receives said enlargement, and a flexible lip which surrounds the mouth of said cavity and engages behind said enlargement to resist axial separation of said rod and piston.

4. A cylinder according to any preceding claim, wherein said sleeve is in the form of an open ended tube, a substantial part of said sleeve is neatly located within said shell, and an end portion of said sleeve projects axially outwards beyond said shell open end.

5. A cylinder according to claim 4, wherein a flexible boot is snap engaged over said sleeve end portion and slidably engages around said rod to form a fluid seal.

6. A cylinder according to any preceding claim, wherein a 5 stop shoulder is formed within the bore of said sleeve and limits axial movement of said piston away from said end wall, and a spring acts between said end wall and said piston to urge said piston away from said end wall.

7. A cylinder according to any preceding claim, wherein 10 said sleeve is retained within said shell by cooperative snap engagement between the sleeve and the shell.

8. A cylinder according to claim 7, wherein said snap engagement is effected between a circumferential bead provided on the outer surface of said sleeve and a complementary

15 circumferential groove formed within the inner surface of said shell.

9. A cylinder according to any preceding claim, wherein a plurality of ribs are formed on the outer surface of said shell so as to strengthen said shell.

20 10. A cylinder according to any preceding claim, wherein an inlet passage is formed through a wall of said shell at a location between the ends of the shell, said inlet passage communicates with transfer passage means provided through said sealing means, said transfer passage means communicates with •25 said pressure chamber when said piston is at a retracted position, and said piston operates to close said communication between the transfer passage means and the pressure chamber as it moves from said retracted position in a direction towards said end wall.

30 ιι. A cylinder according to claim 10, wherein said sealing means includes a pair of annular flexible seals and a spacer ring located between said seals, and said transfer passage means includes passages formed through said spacer ring.

12. A cylinder according to claim 10 or 11, wherein an inner end portion of said piston is surrounded by said sealing means when the piston is in said retracted position, and a plurality of longitudinally extending grooves is formed in the outer surface of said piston end portion to facilitate communication between said pressure chamber and said transfer passage means.

13. A cylinder for use in a fluid pressure system including, a body having an outer shell and an inner sleeve, said outer shell containing at least a substantial part of said inner sleeve in close fitting relationship, said inner sleeve being formed of a relatively hard plastics material, said outer shell being formed of a plastics material which is selected to suit the environment of use of said cylinder, a cylindrical bore formed within said inner sleeve, and a piston slidably located within said bore.

14. A cylinder according to any one of the preceding claims, wherein said piston includes a tubular section which is open at one end and has a transverse wall at its opposite end, and said open end is located adjacent said end wall.

15. A cylinder according to claim 14, wherein a further tubular section extends from said transverse wall in a direction away from said end wall.

16. A cylinder according to claim 2 or any claim appended thereto, wherein a flange is provided on said push rod adjacent said enlargement and abuts against a shoulder of said sleeve to resist separation of said push rod from said cylinder body.

17. A cylinder according to any preceding claim, wherein at least part of said pressure chamber is formed between adjacent ends of said shell and sleeve respectively.

18. A fluid pressure system including a master cylinder which is a cylinder according to any one of claims 10 to 12, a slave cylinder which is a cylinder according to any one of claims 1 to 9, a reservoir connected to said master cylinder inlet passage, and means interconnecting the pressure chambers of the two said cylinders.

19. A system according to claim 18, wherein said slave cylinder has a push rod which is connected to a vehicle clutch so that said clutch is operated in accordance with axial movement of said slave cylinder piston, and a foot pedal is connected to a push rod of said master cylinder so that depression of said pedal causes movement of said master cylinder piston towards the end wall of the master cylinder body.

20. An actuator for use in a fluid pressure system including, an arm arranged for movement about a pivot axis, a cylinder body attached to or formed integral with said arm so as to be movable with said arm about said pivot axis, a cylindrical bore within said body and having its axis extending transverse to said pivot axis, a piston slidably mounted within said bore for axial movement relative to said body, a pressure chamber formed within said body between said piston and a transverse wall of said body, a push rod connected to said piston for movement therewith and extending axially out of said body through an end thereof remote from said transverse wall, and control means cooperating with said push rod so as to be operative to cause said piston to move towards said transverse wall in response to pivotal movement of said arm in one direction.

21. An actuator according to claim 20, wherein said control means includes a cam and a cam follower, said cam is secured to a support structure relative to which said arm moves when moving about said pivot axis, and said cam follower is connected to the end of said push rod which is remote from said piston.

22. An actuator according to claim 21, wherein said cam includes a cam surface, said cam follower includes a roller which is mounted on said push rod for rotation about an axis extending substantially parallel to said pivot axis, and said roller engages and tracks along said cam surface during said pivotal movement of the arm.

23. An actuator according to claim 21 or 22, wherein a slide

» block is provided at the end of said push rod which is remote from said piston, and said block slidably engages against a surface of said arm to guide the movement of said push rod.

24. An actuator according to claim 23 when appended to claim 22, wherein said roller is mounted on said slide block.

25. An actuator according to any one of claims 20 to 24, wherein said cylinder body is formed separate from said arm, and connecting means releasably attaches said cylinder body to said arm.

26. An actuator according to claim 25, wherein said arm has a recess therein and said cylinder body is located within said recess.

27. An actuator according to claim 25 or 26, wherein said cylinder body is a body of a cylinder according to any one of claims 1 to 17.

28. A fluid pressure system including an actuator according to any one of claims 20 to 27, wherein said cylinder body is the body of a master cylinder, a fluid reservoir and a slave cylinder are each connected to the pressure chamber of said master cylinder, and means is provided for temporarily disconnecting said reservoir and said master cylinder pressure chamber as a consequence of movement of said piston towards said transverse wall.

29. A system according to claim 28, wherein said arm is the arm of a foot operated pedal.

30. A coupling for use in a fluid system including a male part and a female part, a passage within each said part, said female part having a frangible diaphragm which is arranged to prevent flow of fluid through the female part passage, and said male part having a probe which is insertable into said female part and is adapted to penetrate through said diaphragm in the course of said insertion so as to thereby provide communication between the two said passages, the arrangement being such that said probe penetrates through said diaphragm when the two parts are in cooperative engagement and the penetrated diaphragm is thereby flexibly distorted to sealingly engage against an outer surface of said probe.

31. A coupling according to claim 30, wherein the passage of said male part extends axially through said probe.

32. A coupling according to claim 30 or 31, wherein said female part includes a bore which receives said probe, the passage of said female part communicates with said bore, and said diaphragm extends over an outer end of said bore before penetration by said probe.

33. A coupling according to claim 32, wherein said diaphragm is formed by a flexible cap member which snap engages over portion of said female part.

34. A coupling according to claim 33, wherein said male part includes a cylindrical body which surrounds said probe with clearance therebetween, said body is receivable over said female part portion and is engageable with portion of said flexible cap member so as to produce a fluid tight seal between said male and female parts.

35. A coupling according to any one of claims 30 to 34, wherein said probe constitutes an outer probe, a frangible diaphragm wall is provided within said outer probe to prevent flow through the male part passage, and an inner probe is provided on said female part and is arranged to enter into said outer probe and penetrate through said diaphragm wall when the two said parts are being moved into said cooperative engagement.

36. A coupling according to any one of claims 30 to 35, wherein releasable fastener means is operative to hold said parts in said cooperative engagement.

37. A fluid system according to any one of claims 18, 19, 28 and 29, including a coupling according to any one of claims 30 to 36.

38. A fluid system according to claim 37, wherein the connection between said master and slave cylinders includes two conduit parts, one said conduit part has respective opposite ends thereof connected to said master cylinder and one of said coupling parts, and the other said conduit part has respective opposite ends thereof connected to said slave cylinder and the other said coupling part.

39. A fluid system including two conduit parts and a coupling according to any one of claims 30 to 36, wherein one said conduit part has an end thereof connected to one of said coupling parts, and the other said conduit part has an end thereof connected to the other said coupling part.

40. A cylinder substantially as herein particularly described with reference to any one of the embodiments shown in the accompanying drawings.

41. An actuator substantially as herein particularly described with reference to any one of the embodiments shown in the accompanying drawings.

42. A fluid pressure system substantially as herein particularly described with reference to any one of the embodiments shown in the accompanying drawings.

43. A coupling substantially as herein particularly described with reference to what is shown in the accompanying drawings.