GB1600503A - Hydraulic motors for use in hydrostatic remote control systems - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO HYDRAULIC MOTORS FOR USE IN HYDROSTATIC REMOTE CONTROL SYSTEMS (71) We, CLAYTON DEWANDRE COMPANY LIMITED, a British Company, of Titanic Works, Lincoln, LN5 7JL, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to an improved hydraulic motor or so-called slave cylinder, for use in a hydrostatic remote control system. Such systems are used for engine throttle actuation and similar purposes.

According to the invention a hydraulic motor or so-called slave cylinder, for use in a remote control system incorporating a hydraulic power boost derived from fullpower hydraulic system and providing servo-assistance, comprising a working chamber and a valve chamber generally coaxially alligned with the working chamber, a slave piston in the working chamber for connection to the device to be actuated, a hydrostatic input port to the working chamber, a balancing piston which is also responsive to the hydrostatic input pressure, an input port for high pressure hydraulic fluid tapped from the full power hydraulic system and leading to the valve chamber, and valve means in the valve chamber adapted to be opened by displacement of the balancing piston to cause high pressure fluid to act on a plunger having operative connection with the slave piston the high pressure fluid also acting on the balancing piston in opposition to the hydrostatic pressure to cause said piston to move and allow the valve means to close.

The invention will now be more fully understood from the following description of two preferred embodiments crosssectional views of which are shown respectively in Figures 1 and 2 of the accompanying drawings.

Referring to Fig. 1, the improved slave cylinder comprises an elongated body or housing 10 having a stepped bore 12 therethrough, said bore defining successively a smaller working chamber or cylinder 14, an intermediate boost chamber 16 and a larger valve cylinder. A slave piston rod 20 displaceable in the smaller bore 14 is integral with a control rod 21 which extends beyond the end of the bore, and in use is connected to the engine throttle or other member (not shown) to be actuated.A balancing piston 22 is also disposed in the smaller bore with a hydrostatic input port 24 between the two pistons connected in use to a master cylinder actuated by an accelerator pedal such that hydrostatic pressure conducted to the bore 14 acts on the slave piston 20' which is in the form of a bush encircling the rod 20 abutting a shoulder provided by the control rod 21 to urge it in the direction to actuate the engine throttle and simultaneously on the front face of the balancing piston 22 to urge it in the opposite direction. A tubular fitting 30 within the larger bore section 18 includes a transverse wall 48 dividing the interior of the tubular fitting into a valve chamber 54 and an inlet chamber 52.A full power hydraulic inlet port 50 is connected to the inlet chamber 52 whilst in the valve chamber 54 a ball valve element 56 located radially in an end of an exhaust extension 58, referred to more fully hereafter, and axially by a transverse pin 60 fixed in the tubular fitting 30, co-acts with a cup-shaped valve seat member 62 which is spring-loaded towards the ball 56 and has a hollow stem 64 extending through said transverse wall 48 of the tubular fitting 30 with a sealed sliding fit. Disposed in the intermediate chamber and abutting the balancing piston at its rear side is a seat element 66 having a sealed sliding fit with the slave piston rod or plunger 20, which passes through it, and being formed with an inturned flange 70.Normally abutting said flange 70 on the seat element 66 is a tubular extension 58 to form an exhaust valve controlling the flow of fluid to the exhaust port and which at its other end has a reduced portion 59 extending with a sealed sliding fit through the end wall of the tubular fitting 30 and connected to the cupshaped member 62 by means such as a rollpin or circlip, the reduced portion being apertured to clear or by-pass the transverse pin 60 and the aperture 72 being large enough to allow the pin 60 and thereby the ball valve 56 to travel.

In the second embodiment also the elongated body or housing 110 also has a stepped bore 112, defining a small working chamber or cylinder 114, an intermediate boost chamber 116 and a large valve chamber 118. The slave piston 120' displaceable in the smaller bore 114 is socketed to receive a separate control rod 121 which extends beyond the end of the bore and in use is connected to the engine throttle or other member (not shown) to be actuated.A balancing piston 122 is disposed in the intermediate bore section or boost chamber and a hydrostatic input port 124 connected in use to a master cylinder actuated (for example) by an accelerator pedal, leads to the junction between the smaller and intermediate bore sections such that hydrostatic pressure conducted to the bore acts on the slave piston 120' to urge it in the direction to actuate the engine throttle and simultaneously on the front face of the balancing piston 122 to urge it in the opposite direction. A tubular fitting 130 within the larger bore section includes an end wall 132 separating the bore section from the boost chamber and a further transverse wall 134 dividing the interior of the tubular fitting 130 into a valve chamber 154 and an inlet chamber 152.A full power hydraulic inlet port 150 is connected via a filter 151 to the inlet chamber 152 whilst in the valve chamber 154 the ball valve element 156 located in a recess in a fixed support co-acts with the cup-shaped valve seat member 162 which is spring-loaded towards the ball 156 and has a hollow stem 164 extending through the transverse wall 148 of the tubular fitting 130 with a sealed sliding fit. Abutting the balancing piston 122 at its rear side is a tubular exhaust seat element 166 having an inturned flange 170 providing an exhaust seat area and contiguous with this element and normally abutting the flange 170 is a tubular exhaust extension 158 which at its other end extends with a sealed sliding fit through the end wall of the tubular fitting 130 and engages a stirrup 160 in abutment with the valve seat member 162.A plunger or piston rod 120 extends axially through the balancing piston 122, exhaust seat element 166 and exhaust extension 158 and is guided for axial movement therein, its outer end being seated in a socket in the slave piston 120'. Seals are provided at both sides of the balancing piston 122 and each embodiment of the slave cylinder operates as follows:: When the master cylinder is actuated hydrostatic pressure is transmitted to the slave cylinder and acting upon the slave piston 20', 120' displaces it and the control rod 21, 121 to actuate the engine throttle At the same time the hydraulic pressure displaces the balancing piston 22, 122 in the opposite direction and, through the exhaust seat element 66, 166 and exhaust extension 58, 158 (and the stirrup l6Fig. 2), moves the valve seat member 62, 162 away from the ball valve 56, 156 so admitting high pressure fluid through the bore of the valve seat member 62, 162 and through the valve chamber 54, 154 to the bore of the exhaust extension 58, 158 where it then acts on the exhaust seat area of the exhaust seat element 66, 166 to blance out the input hydrostatic force whereby the balancing piston 22, 122 then moves back and allows the inlet valve to close.The high pressure fluid within the exhaust extension also acts over the area of the rod 20, 120 contained by either an annular seal on the inner side of the balancing piston 22 or 122 and produces a force on the rod 20, 120 which is transmitted through the slave piston 20' 120' (and control rod 21, 121) to augment the force of the hydrostatic pressure acting on the slave piston 20', 120'. When the sum of the hydrostatic and the boost forces now acting on the control rod 21, 121 overcomes the load the control rod moves and the piston assembly in the housing 10, 110 follows, the increasing volume behind the piston assembly being met by additionai fluid introduced from the master cylinder.

The balancing piston 22, 122 will continue to balance as the assembly travels, maintaining the boost pressure on the plunger in a fixed ratio to the hydrostatic pressure.

Where the exhaust extension passes through the end of the tubular fitting 30, 130 it is sealed by a ring which is subjected on its outer face to the high pressure fluid and which in the embodiment of Figure 2 is of slightly smaller area than the exhaust seat area, this slight imbalance serving to bias the exhaust extension towards the inlet end and thereby ensure opening of the exhaust. In the preferred embodiment of Figure 1 the relative sizes of the corresponding areas are chosen so as in use, to bias the exhaust extension towards the exhaust and not the inlet, this being possible because the exhaust extension is fixed to the valve seat member.In an alternative construction of the Figure 2 embodiment the exhaust extension 158, the stirrup 160 and the valve seat member 162 are rigidly interconnected for unified movement and with such construction the need for controlled balancing of the exhaust extension sealing ring and the exhaust seat area does not arise. Yet another possibility is to provide a stop for the exhaust extension 158 so that the extension can be biased away from the inlet whilst the stop ensures opening of the exhaust valve. Unfortunately this solution requires there to be motion between inlet closing and exhaust opening.

Thus it will be seen that the above described embodiments provide a hydraulic throttle control system with full hydraulic power boost to the slave cylinder whilst retaining the direct travel sensitivity of a hydrostatic system and the maintained availability of the hydrostatic system in the event of a power failure. Other features of the described construction are the valve actuating means allowing a simple concentric layout of components without additional drillings, and floating valve elements whereby relatively coarse concentricity tolerances can be accepted.

WHAT WE CLAIM IS: 1. A hydraulic motor or so-called slave cylinder, for use in a hydrostatic remote control system incorporating a hydraulic power boost derived from a full-power hydraulic system and providing servo.

assistance, comprising a working chamber and a valve chamber generally co-axially aligned with the working chamber, a control link for connection to a device to be actuated and movable by a slave piston in the working chamber, a hydrostatic input port to the working chamber, a balancing piston which is also responsive to the hydrostatic input pressure, an input port for high pressure hydraulic fluid tapped from the full power hydraulic system and leading to the valve chamber, and valve means in the valve chamber adapted to be opened by displacement of the balancing piston to cause high pressure fluid to act on a plunger having an operative connection with the control link, the high pressure fluid also acting on the balancing piston in opposition to the hydrostatic pressure to cause the piston to move and allow the valve means to close.

2. A hydraulic motor according to Claim 1 wherein the valve means comprises a ball valve element and a cup-shaped valve seat, the seat being movable in response to displacement of the balancing piston to open the valve.

3. A hydraulic motor according to Claim 2 comprising an exhaust valve seat element axially movable with the balancing piston to close one end of tubular exhaust extension engageable by the exhaust valve seat and to operate the valve, and into which high pressure fluid is admitted when the valve is open.

4. A hydraulic motor according to Claim 3 wherein the exhaust extension is apertured to clear or by-pass a fixed transverse locating pin which holds the ball on the cup-shaped seat in one position of the exhaust extension and to allow movement of the ball to open the valve, in another position, of the extension.

5. A hydraulic motor according to Claim 2 or Claim 3 wherein the plunger comprises a rod which extends axially through the balancing piston into the interior of the tubular exhaust extension.

6. A hydraulic motor according to any one of Claims 3 to 5 wherein the exhaust extension is, in use, biased in the direction Df closing the said valve means.

7. A hydraulic motor for use in a hydrostatic remote control system and constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Figure 1 or Figure 2 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. balancing of the exhaust extension sealing ring and the exhaust seat area does not arise. Yet another possibility is to provide a stop for the exhaust extension 158 so that the extension can be biased away from the inlet whilst the stop ensures opening of the exhaust valve. Unfortunately this solution requires there to be motion between inlet closing and exhaust opening. Thus it will be seen that the above described embodiments provide a hydraulic throttle control system with full hydraulic power boost to the slave cylinder whilst retaining the direct travel sensitivity of a hydrostatic system and the maintained availability of the hydrostatic system in the event of a power failure. Other features of the described construction are the valve actuating means allowing a simple concentric layout of components without additional drillings, and floating valve elements whereby relatively coarse concentricity tolerances can be accepted. WHAT WE CLAIM IS:

1. A hydraulic motor or so-called slave cylinder, for use in a hydrostatic remote control system incorporating a hydraulic power boost derived from a full-power hydraulic system and providing servo.

assistance, comprising a working chamber and a valve chamber generally co-axially aligned with the working chamber, a control link for connection to a device to be actuated and movable by a slave piston in the working chamber, a hydrostatic input port to the working chamber, a balancing piston which is also responsive to the hydrostatic input pressure, an input port for high pressure hydraulic fluid tapped from the full power hydraulic system and leading to the valve chamber, and valve means in the valve chamber adapted to be opened by displacement of the balancing piston to cause high pressure fluid to act on a plunger having an operative connection with the control link, the high pressure fluid also acting on the balancing piston in opposition to the hydrostatic pressure to cause the piston to move and allow the valve means to close.

2. A hydraulic motor according to Claim 1 wherein the valve means comprises a ball valve element and a cup-shaped valve seat, the seat being movable in response to displacement of the balancing piston to open the valve.

3. A hydraulic motor according to Claim 2 comprising an exhaust valve seat element axially movable with the balancing piston to close one end of tubular exhaust extension engageable by the exhaust valve seat and to operate the valve, and into which high pressure fluid is admitted when the valve is open.

4. A hydraulic motor according to Claim 3 wherein the exhaust extension is apertured to clear or by-pass a fixed transverse locating pin which holds the ball on the cup-shaped seat in one position of the exhaust extension and to allow movement of the ball to open the valve, in another position, of the extension.

5. A hydraulic motor according to Claim 2 or Claim 3 wherein the plunger comprises a rod which extends axially through the balancing piston into the interior of the tubular exhaust extension.

6. A hydraulic motor according to any one of Claims 3 to 5 wherein the exhaust extension is, in use, biased in the direction Df closing the said valve means.

7. A hydraulic motor for use in a hydrostatic remote control system and constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Figure 1 or Figure 2 of the accompanying drawings.