The present invention relates to an integrated hydro-pneumatic cylinder with controlled pressure rate arrangement. More specifically, it relates to a device for overriding a hydraulic line, and even more specifically preventing the overrun of an automobile engine.
Background
The overrun of an automobile engine is defined as damage caused to the engine due to the high-speed rotation of said engine for an extended period of time. As the fuel of the engine is ignited in the combustion chamber, a piston is configured to generate rotational force to a crank shaft while linearly reciprocating in the cylinder. This piston reciprocates at a high speed inside the cylinder, with the cylinder having an airtightness to efficiently convert the combustion energy into mechanical rotational energy. This results in a high amount of friction that is mitigated by the use of engine oil.
Typically, the engine has a preferred range of operating speeds at which the engine can be continuously operated smoothly with the presence of such a lubricant. However, if this is exceeded, the lubrication action is reduced due to a decrease in the viscosity of the lubricant. Furthermore, insufficient cooling of the lubricant can lead to the engine overheating.
As such, continuous excessive engine operation must be prevented. The range of appropriate engine speeds is usually displayed on an instrument panel, allowing the operator to ensure the engine speed is in a predetermined and acceptable level. However, there are cases in which the operator may not notice an occasion where a fault means the engine speed is being forced higher than instructed or a scenario in which the engine speed must be reduced.
When said instrument panel is disregarded, a gear shift from a higher to a lower gear takes place, the vehicle travels downhill (especially in a lower gear), or a fault is developed, the engine speed will be increased. Not only will this cause

the life of the engine to be lowered, but also the speed of a vehicle will be increased, potentially increasing the risk of a traffic accident.
The prevention of engine over-run is traditionally accomplished by the manual disengagement of a clutch system. A schematic representation of this system is shown in Figure 1. In this system 10, a clutch pedal 20 is used to activate a clutch master cylinder 30 via a push rod 22. The clutch master cylinder 30 is fed by a clutch master cylinder reservoir 32 and is connected to a clutch slave cylinder 40 via a hydraulic line 34. The clutch slave cylinder 40 then disengages a clutch plate assembly 50 via a clutch fork 52.
As such, the system 10 can prevent the over-run of an engine. However manual activation is required. As discussed previously, manual activation has the potential for issues such as the incorrect usage of the system by the user or the presence of a fault in the system meaning the system does not work as intended.
The present invention seeks to overcome or at least mitigate the problems described above. However, that is not to say that the invention is limited to these situations and more generally seeks to provide a system in which a hydraulic and pneumatic system can be integrated with a controlled and measured pressure rate relationship.
Summary
A first aspect of the invention provides a pressure override device, the device comprising: a solenoid; a hydraulic valve assembly having a cylinder with a piston and a non-return valve arranged therein, with the hydraulic valve assembly having an open position and a closed position, the hydraulic valve assembly also comprising a hydraulic inlet and hydraulic outlet, the hydraulic inlet being blocked by the non-return valve in the closed position; and a pneumatic valve assembly having a cylinder with a piston arranged therein, the pneumatic valve assembly having an open position and a closed position, the pneumatic valve assembly also comprising a pneumatic inlet and pneumatic outlet, the pneumatic outlet comprising a variable flow restrictor; wherein the

hydraulic piston is operably connected to the pneumatic piston; wherein the solenoid is arranged to actuate the pneumatic piston to the open position upon reception of a signal; and wherein the actuation of the pneumatic piston to the open position actuates the hydraulic piston to the closed position.
The provision of such a device allows for the overriding of a hydraulic line, the conversion of pneumatic pressure into hydraulic pressure, and the regulation of the pressure between the pneumatic and hydraulic lines.
The hydraulic valve assembly and the pneumatic valve assembly may be formed within a single body. In this way, the device can be formed in a compact and space saving manner. This allows the device to be incorporated into existing systems without significant changes to these systems. The single body may be formed of two parts. In this way, the device can be easily assembled and disassembled for ease of manufacture, maintenance, and repair.
At least one of the hydraulic valve assembly and pneumatic valve assembly may further comprise at least one integrated spring. These springs provide resistive force to components of said valve assemblies to return to pistons to their open position and in order to produce a consistent and controlled hydraulic and pneumatic pressure-pressure relationship. Adjusting the stiffness of the spring allows for control of said relationship. In some embodiments, the hydraulic valve assembly and pneumatic valve assembly share at least one of the integrated springs, further allowing the device to be provided in a compact and simple manner.
The piston of the hydraulic valve assembly and the piston of the pneumatic valve assembly may have a single shared shaft. In this way, the device can further be provided in a compact and simple manner. Furthermore, by using a single shared shaft, a direct relationship between the movement of the two pistons can be achieved.
The piston of the hydraulic valve assembly and the piston of the pneumatic valve assembly may have piston faces, and the piston faces may be substantially circular. The pneumatic piston face may have a larger diameter

than that of the hydraulic piston face. In this way, the required pneumatic and hydraulic pressure-pressure relationship can be achieved. By altering the relative sizes of these faces, the pneumatic and hydraulic pressure-pressure relationship can be adjusted and tuned.
The non-return valve may be arranged to block the hydraulic inlet via a pin that slidably fits into a slot in the hydraulic piston. In this way, the hydraulic piston can have a relatively long range of travel whilst the device remains compact and engages the non-return valve as required. The pneumatic outlet may comprise a variable flow restrictor. This allows for the pressure-time relationship of the hydraulic outlet to be controlled.
The device may further comprise receiving means for receiving the signal to actuate the solenoid. In this way, a cut-off signal can be received by the device in order to override the hydraulic line.
The pneumatic inlet may have an air filtration system, allowing blockages of the pneumatic valve assembly to be reduced and the reliability of said valve assembly to be increased by removing damaging particulates from the air inlet flow. Likewise, the hydraulic inlet may have a blockage prevention device, ensuring blockages of the hydraulic valve assembly are reduced and the reliability of said valve assembly is increased by removing damaging particulates from the hydraulic inlet flow.
A second aspect of the invention provides a pressure override system, the system comprising the pressure override device described above; an input device; an output device; and a pressure regulation device; wherein the input device is connected to the solenoid; wherein the output device is hydraulically connected to the hydraulic outlet; wherein the pressure regulation device is pneumatically connected to the solenoid; and wherein the pressure regulation device and variable flow restrictor control the relationship between the input device and the output device.
The provision of such a system provides a consistent pressure-time relationship between the input and output devices and allows for the overriding of the outlet

device. It also provides a pressure conversion system for converting pneumatic pressure into hydraulic pressure, as well as a system for regulating the pressure between the input and output devices. The pressure regulation device allows the pressure throughout the system to be controlled as required, in order to control the output from the device.
The input device may be an engine control unit or other monitoring means, the output device may be a clutch or other hydraulic control means, and the activation of the input device may cause the activation of the output device. In this way, the system can be utilised as an engine cut-off device through engagement or disengagement of the clutch or activation or deactivation of other hydraulic control means via activation of the pressure override device in response to a signal from the engine control unit or other monitoring means.
A third aspect of the invention provides a method for overriding the pressure of a system, the method comprising steps of: a) providing a system comprising: a pressure override system described above; and a control unit arranged to monitor the function of the system; b) registering, in the control unit, an undesirable condition of the system; c) sending, from the control unit, a signal to the solenoid of the pressure override device; d) the pressure override system receiving the signal; e) actuating the solenoid to move the pneumatic valve assembly to the open position via the pressure override device, this in turn actuating the hydraulic valve assembly to the closed condition; f) the closed condition of the hydraulic valve assembly resulting in a high-pressure condition in the output device; and g) the high-pressure condition resulting in the overriding of the output device.
The provision of such a method provides a cut-off (or override) mechanism between the input device and output device after the receipt of a signal of an undesirable state of the system. In this way, the undesirable state can be managed and prevented.
Brief Description of the Drawings

Embodiments will now be described, by way of example only, with reference to the accompanying figures, in which:
FIGURE 1 is a schematic view of a clutch system of the prior art;
FIGURE 2 is a perspective view of a device according to the present invention;
FIGURE 3 is a side view of the device of Figure 2;
FIGURE 4 is a cross-section view of the device of Figure 2 according to the line A-A shown in Figure 3;
FIGURE 5 is a partial cross-section view of the device of Figure 2 according to the line B-B shown in Figure 3;
FIGURE 6 is a schematic view of the device of Figure 2 in a 1st state;
FIGURE 7 is a schematic view of the device of Figure 2 in a 2nd state;
FIGURE 8 is a schematic view of the device of Figure 2 in a 3rd state; and
FIGURE 9 is a graph of the pressure-time relationship produced by the device of Figure 2.
Detailed Description of Embodiments
Figure 2 shows a device 110 according to the invention. The device 110 comprises a housing 120. Affixed to a first end 122 of the housing 120 are a solenoid 130 and a pressure regulating device 140. The housing 120 has ports 121 formed therein.
The arrangement of the solenoid 130 and the pressure regulating device 140 on housing 120 can further be seen in Figure 3. A pneumatic inlet 152 and a pneumatic outlet 154 are provided through the housing 120, whilst a hydraulic

inlet 162 and a hydraulic outlet 164 are provided through a second end 124 of the housing 120 (the hydraulic outlet 164 not visible in Figure 2).
The housing 120 is further comprised of a first part 126 and a second part 128. The first part 126 is proximate the first end 122 and the second part 128 is proximate the second end 124. In other embodiments (not shown), the housing 120 is formed of a single part.
Figure 4 shows a section view of the device 110 along the line A-A as shown in Figure 3. Meanwhile, Figure 5 shows a further adjusted side section view of device 110 taken along the line B-B as shown in Figure 3. This section view is adjusted so that a central section view of both of the solenoid 130 and pressure regulating device 140 can be shown in the same figure. In this view, the pressure regulating spring 142 located within pressure regulating device 140 can be seen.
As can be seen in Figures 4 and 5, a pneumatic valve assembly 150 is provided proximate to the first end 122 of housing 120, whilst a hydraulic valve assembly 160 is provided within the housing 120 proximate the second end 124 of said housing 120.
Pneumatic valve assembly 150 comprises the pneumatic inlet 152 and pneumatic outlet 154, both being pneumatically connected to pneumatic cylinder 156. Pneumatic cylinder 156 has pneumatic piston 158 arranged therein.
Similarly, hydraulic valve assembly 160 comprises the hydraulic inlet 162 and the hydraulic outlet 164, both being hydraulically connected to hydraulic cylinder 166. The hydraulic cylinder 166 has a hydraulic piston 168 arranged therein.
A non-return valve 167 is arranged to cooperate with the hydraulic piston 168, this valve 167 being hydraulically connected to the inlet 162. The valve 167 is in the form of a seal shaped to block the flow from hydraulic inlet 162. The

valve 167 is arranged to cooperate with the hydraulic piston 168 via a pin 167a that slidably fits into a slot 167b in the hydraulic piston 168.
The pneumatic inlet 152 is fed through a pneumatic air filtration device (not shown), whilst the hydraulic inlet 162 is fed through a hydraulic port blockage prevention device (not shown). These devices increase the efficiency and lifespan of the pneumatic and hydraulic valves 150, 160 respectively. The pneumatic outlet 154 also has a variable flow restrictor 155 that blocks the flow through the outlet 154.
Within the housing 120, pneumatic cylinder 156 and hydraulic cylinder 166 are connected such that they form a single chamber. Said chamber is formed from the meeting of the first and second parts 126, 128 of the housing 120. The pneumatic cylinder 156 is larger than that of hydraulic cylinder 166. Furthermore, pneumatic piston 158 and hydraulic piston 168 are formed of the same component. That is, they share the same shaft 170, the shaft ending in pneumatic piston head 159 and hydraulic piston head 169 at opposing ends of said shaft 170. A gap 174 is formed between the pneumatic piston head 159 and the second part 128 of housing 120.
Furthermore, the pneumatic piston 158 and hydraulic piston 168 share a single spring 172. Seals 180 are provided in order to provide adequate sealing throughout the pneumatic valve assembly 150 and the hydraulic valve assembly 160, to ensure no leakage between the hydraulic and pneumatic systems.
In other embodiments (not shown), the pneumatic cylinder 156 and hydraulic cylinder 166 form separate chambers. In further additional embodiments (also not shown), pneumatic piston 158 and hydraulic piston 168 are formed of separate components that are operatively connected. In this way, pneumatic piston 158 and hydraulic piston 168 have distinct shafts. In some additional embodiments, there are multiple springs present. This may be spring 172 and an additional spring in gap 174, or may be multiple springs if the pneumatic cylinder 156 and hydraulic cylinder 166 form separate chambers.

The pneumatic valve assembly 150 and the hydraulic valve assembly 160 are arranged such that, when the hydraulic piston 168 moves towards the second end 124 of housing 120 (resisted by the spring 172), the non-return valve 167 gradually blocks the hydraulic inlet 162.
The movement of the pneumatic piston head 159 compresses or expands gap 174. To prevent this compression of expansion producing resistive forces against the movement of the pneumatic piston head 159 (and more generally the shaft 170), the port 121 in the housing 120 allow air to pass between the external surrounds of the housing 120 and the gap 174.
The pneumatic valve assembly 150 is fed by a pneumatic reservoir 151 that is connected to pneumatic inlet 152. Likewise, the hydraulic valve assembly 160 is fed by a hydraulic reservoir (not shown) which is connected to hydraulic inlet 162.
The solenoid 130 and the pressure regulating device 140 are both pneumatically connected to the pneumatic valve assembly 150. The solenoid 130 is connected to the system 10 of the prior art by way of an engine control unit (not shown) that identifies when the engine is in an overrun condition. In this way, the device 110 is hydraulically connected to the input of whether the clutch pedal 20 has been pressed or not via the slave cylinder 40.
The solenoid 130 allows for the activation of the device 110 upon reception of a signal from an engine control unit 190, as will be discussed in greater detail below. The pressure regulating device 140 is arranged between the pneumatic inlet 152 and the solenoid 130. However, in other embodiments (not shown), the pressure regulating device 140 pneumatically precedes the pneumatic inlet 152.
With the aid of Figures 6 to 8, it shall now be described how the device 110 is operated.
Figure 6 shows a schematic view of the device 110 when the clutch pedal 20 has not been pressed and there is no overrun condition. Both the hydraulic

inlet 162 and hydraulic outlet 164 are in a low-pressure condition, whereby the hydraulic cylinder 166 allows the hydraulic fluid to move freely from said inlet 162 to said outlet 164. As such, the low pressure in the hydraulic outlet 164 means the clutch system 10 is not activated and the engine is allowed to run under normal operating conditions.
Figure 7 is similar to Figure 6, but shows the device 110 when the clutch pedal 20 is pressed (but the overrun prevention system is still inactive). In this case, the pressure in both the hydraulic inlet 162 and the hydraulic outlet 164 is high, but the hydraulic fluid can still move through the hydraulic cylinder 166 between said inlet 162 and said outlet 164. The high pressure of the hydraulic outlet 164 disengages the clutch via system 10, as was requested by the user via clutch pedal 20.
In Figure 8, an overrun condition has been identified by the engine control unit 190, but the clutch pedal 20 has not been pressed. In this case, the solenoid 130 has been activated upon receiving a signal from the engine control unit 190 indicating that the overrun condition is present and that the clutch pedal 20 has not been pressed. This actuation of the solenoid 130 opens the inlet 152 of pneumatic valve assembly 150, increasing pressure within the first end 122 of the housing 120, inside of the pneumatic cylinder 156. This causes the pressure in the side of the pneumatic cylinder 156 to increase and to be greater than the resistive force provided by the spring 172. This moves the shaft 170 in the direction towards the second end 124 of housing 120. Pin 167a slides within slot 167b, allowing pneumatic piston 168 to move towards the second end 124 without engaging non-return valve 167. As the pin 167a reaches the end of slot 167b, the non-return valve 167 begins to be engaged. This causes a higher pressure within the second end 124 of the housing 120, inside of the hydraulic cylinder 166, by gradually blocking the hydraulic inlet 162 via the non-return valve 167 and preventing hydraulic fluid flow through the hydraulic cylinder 166. As such, although the hydraulic inlet 162 is at a low pressure, the hydraulic outlet 164 is at a high pressure. This high pressure results in the clutch being disengaged via system 10. In this way, the overrun condition is prevented.

If the clutch pedal 20 is then depressed, the solenoid 130 is returned to its original position and the device 110 returns to the state shown in Figure 7. The pressure in the pneumatic valve assembly 150 releases uniformly, resulting in the resistive force by the spring 172 uniformly returning the shaft 170 to its original position. This gradually opens the non-return valve 167 producing a uniform reduction in pressure in the hydraulic valve assembly 160. This uniform pressure drop over time, shown in Figure 9, provides the same proportional effect that the usual clutch system 10 would have provided.
By modifying the various aspects of the device, this pressure/time relationship can be adjusted as required. The rate of this pressure drop is controlled by the air passing through the pneumatic inlet 152 and outlet 154. The volume of air passing through the pneumatic inlet 152 in a given time is controlled by the stiffness of pressure regulating spring 142 in the pressure regulating device 140. The volume of air exiting the device 110 in a given time via the pneumatic outlet 154 is controlled by the variable flow restrictor 155. As such, by modifying the stiffness of the pressure regulating spring 142 and the functioning of the variable flow restrictor 155, the pressure/time relationship can be controlled.
Likewise, the relationship between the pneumatic pressure and hydraulic pressure can be adjusted by tuning the relative sizes of the pneumatic piston head 159 and the hydraulic piston head 169, and by adjusting the stiffness of spring 172.
Whilst it has been described that the override condition has been detected and acted upon when the clutch pedal 20 has not be pressed (and as such no input has been received), there is also envisioned a version of the methodology wherein device 110 is activated when such an input has been received.
It is also envisioned that this device 110 could be applied to any other situation in which a pressure cut-off or override device is required, or in which a hydraulic/pneumatic pressure conversion device is needed.

I/We Claim:

1. A pressure override system, the system comprising:
a pressure override device, the device comprising: a solenoid;
a hydraulic valve assembly having a cylinder with a piston and a non-return valve arranged therein, the hydraulic valve assembly having an open position and a closed position, the hydraulic valve assembly also comprising a hydraulic inlet and hydraulic outlet, the hydraulic inlet being blocked by the non-return valve in the closed position; and
a pneumatic valve assembly having a cylinder with a piston arranged therein, the pneumatic valve assembly having an open position and a closed position, the pneumatic valve assembly also comprising a pneumatic inlet and pneumatic outlet, the pneumatic outlet comprising a variable flow restrictor; wherein the hydraulic piston is operably connected to the pneumatic piston;
wherein the solenoid is arranged to actuate the pneumatic valve assembly to the open position upon reception of a signal; and
wherein the actuation of the pneumatic valve assembly actuates the hydraulic valve assembly to the closed position; an input device; an output device; and a pressure regulation device;
wherein the input device is connected to the solenoid; wherein the output device is hydraulically connected to the hydraulic outlet;
wherein the pressure regulation device is pneumatically connected to the solenoid; and
wherein the pressure regulation device and variable flow restrictor control the relationship between the input device and the output device.

2. The pressure override system of claim 1, wherein the hydraulic valve assembly and the pneumatic valve assembly are formed within a single body.
3. The pressure override system of claim 2, the single body being formed of two parts.
4. The pressure override system of any of the preceding claims, wherein at least one of the hydraulic valve assembly and pneumatic valve assembly comprise at least one integrated spring.
5. The pressure override system of claim 4, wherein the hydraulic valve assembly and pneumatic valve assembly share at least one of the integrated springs.
6. The pressure override system of any of the preceding claims, wherein the piston of the hydraulic valve assembly and the piston of the pneumatic valve assembly have a single shared shaft.
7. The pressure override system of any of the preceding claims, wherein the piston of the hydraulic valve assembly and the piston of the pneumatic valve assembly have piston faces, the piston faces being substantially circular.
8. The pressure override system of claim 7, wherein the pneumatic piston face has a larger diameter than that of the hydraulic piston face.
9. The pressure override system of any of the preceding claims, wherein the non-return valve is arranged to block the hydraulic inlet via a pin that slidably fits into a slot in the hydraulic piston.
10. The pressure override system of any of the preceding claims, further comprising receiving means for receiving the signal to actuate the solenoid.
11. The pressure override system of any of the preceding claims, the pneumatic inlet having an air filtration system.

12. The pressure override system of any of the preceding claims, the hydraulic inlet having a blockage prevention device.
13. The pressure override system of any of the preceding claims, wherein the input device is an engine control unit or other monitoring means.
14. The pressure override system of any of the preceding claims, wherein the output device is a clutch or other control means.
15. The pressure override system of any of the preceding claims, wherein the activation of the input device causes the activation of the output device.
16. A pressure override device, the device comprising:
a solenoid;
a hydraulic valve assembly having a cylinder with a piston and a non-return valve arranged therein, the hydraulic valve assembly having an open position and a closed position, the hydraulic valve assembly also comprising a hydraulic inlet and hydraulic outlet, the hydraulic inlet being blocked by the non-return valve in the closed position; and
a pneumatic valve assembly having a cylinder with a piston arranged therein, the pneumatic valve assembly having an open position and a closed position, the pneumatic valve assembly also comprising a pneumatic inlet and pneumatic outlet, the pneumatic outlet comprising a variable flow restrictor; wherein the hydraulic piston is operably connected to the pneumatic
piston;
wherein the solenoid is arranged to actuate the pneumatic piston to the
open position upon reception of a signal; and
wherein the actuation of the pneumatic piston to the open position
actuates the hydraulic piston to the closed position.
17. The pressure override device of claim 16, wherein the hydraulic valve assembly and the pneumatic valve assembly are formed within a single body.

18. The pressure override device of claim 17, the single body being formed of two parts.
19. The pressure override device of any of claims 16 to 18, wherein at least one of the hydraulic valve assembly and pneumatic valve assembly comprise at least one integrated spring.
20. The pressure override device of claim 19, wherein the hydraulic valve assembly and pneumatic valve assembly share at least one of the integrated springs.
21. The pressure override device of any of claims 16 to 20, wherein the piston of the hydraulic valve assembly and the piston of the pneumatic valve assembly have a single shared shaft.
22. The pressure override device of any of claims 16 to 21, wherein the piston of the hydraulic valve assembly and the piston of the pneumatic valve assembly have piston faces, the piston faces being substantially circular.
23. The pressure override device of claim 22, wherein the pneumatic piston face has a larger diameter than that of the hydraulic piston face.
24. The pressure override system of any of claims 16 to 23, wherein the non-return valve is arranged to block the hydraulic inlet via a pin that slidably fits into a slot in the hydraulic piston.
25. The pressure override device of any of claims 17 to 24, wherein the pneumatic outlet comprises a variable flow restrictor.
26. The pressure override device of any of claims 17 to 25, further comprising a pressure regulation device.
27. The pressure override device of any of claims 17 to 26, further comprising receiving means for receiving the signal to actuate the solenoid.

28. The pressure override device of any of claims 17 to 27, the pneumatic inlet having an air filtration system.
29. The pressure override device of any of claims 17 to 29, the hydraulic inlet having a blockage prevention device.
30. A method for overriding the pressure of a system, the method comprising steps of:
a) providing a pressure override system comprising:
a pressure override device, the device comprising: a solenoid;
a hydraulic valve assembly having a cylinder with a piston and a non-return valve arranged therein, the hydraulic valve assembly having an open position and a closed position, the hydraulic valve assembly also comprising a hydraulic inlet and hydraulic outlet, the hydraulic inlet being blocked by the non-return valve in the closed position; and
a pneumatic valve assembly having a cylinder with a piston arranged therein, the pneumatic valve assembly having an open position and a closed position, the pneumatic valve assembly also comprising a pneumatic inlet and pneumatic outlet, the pneumatic outlet comprising a variable flow restrictor; wherein the hydraulic piston is operably connected
to the pneumatic piston;
wherein the solenoid is arranged to actuate the
pneumatic valve assembly to the open position upon
reception of a signal; and
wherein the actuation of the pneumatic valve
assembly actuates the hydraulic valve assembly to the
closed position;
an input device;

an output device; and
a pressure regulation device; wherein the input device is connected to the solenoid;
wherein the output device is hydraulically connected to
the hydraulic outlet;
wherein the pressure regulation device is pneumatically
connected to the solenoid; and
wherein the pressure regulation device and variable flow
restrictor control the relationship between the input
device and the output device; and
a control unit arranged to monitor the function of the system;
b) registering, in the control unit, an undesirable condition of the system;
c) sending, from the control unit, a signal to the solenoid of the pressure override device;
d) the pressure override system receiving the signal;
e) actuating the solenoid to move the pneumatic valve assembly to the open position via the pressure override device, this in turn actuating the hydraulic valve assembly to the closed condition;
f) the closed condition of the hydraulic valve assembly resulting in a high-pressure condition in the output device; and
g) the high-pressure condition resulting in the overriding of the
output device.