GB2031118A - Fluid flow control valves - Google Patents

Abstract

A pressure responsive, fluid flow control valve, particularly for a truck gear box shifter, for controlling flow of one fluid such as air in response to the pressure of another fluid such as liquid. The valve comprises a body 12 with a longitudinal passage 14 containing a valve seat 34 cooperating with a ball valve 36 to control communication between an inlet 18 from an air source 20 and an outlet 24 to the gear box shifter. The position of the ball valve is controlled by a rod 58 the position of which is controlled by a spring 70 and the pressure of the hydraulic fluid in the clutch slave cylinder applied to a piston 50. When the ball is seated on the seat the gear box shifter is vented through passages 60, 60' in the rod and a vent passage 26. Thus the gear box cannot be shifted except when the clutch pedal is depressed. <IMAGE>

Description

SPECIFICATION Fluid flow control valves This invention relates to fluid flow control valves and to vehicles incorporating such valves. According to one aspect of the present invention, a fluid flow control valve comprises: a body having an elongate passage therein with a pressure port having means for connecting the passageway with a first pressurized fluid, a second port serving as an inlet port to the passageway for a second pressurized fluid and an outlet port in the body from the passageway intermediate the pressure and inlet ports; a valve element and a valve seat in the passageway between the inlet port and the outlet port, and a spring for biasing the valve element against the seat; a piston reciprocatable in the passage and a rod extending in the passageway from one side of the piston toward the valve, the other side of the piston being in communication with the pressure port; biasing means for biasing the piston and rod away from the valve, and the piston and rod being shiftable toward the valve element by fluid pressure at the pressure port to engage, at a predetermined fluid pressure, the valve and shift it off the seat to allow the second fluid to flow from the entry port to the outlet port.

Certain vehicles such as heavy duty trucks employ a multiple speed gear box with high and low ranges. The shift mechanism for this often involves the use of pressurized air. It has been found desirable to control the conditions under which the vehicle driver is allowed to shift the gear box between low and high range.Valves constructed in accordance with the first aspect of the invention are particularly suitable for this purpose and, according to a second aspect of the present invention, a vehicle has an engine and, between the engine and a road wheel, a clutch operated by a hydraulic motor and a gear box having a pneumatically operable shift mechanism for shifting the gear box from one range of gear ratios to another, a pneumatic pressure source, and a fluid flow control valve according to the first aspect of the invention, the means for connecting the passageway with a first pressurized fluid being connected to hydraulic input to the hydraulic motor, the inlet port being connected to the pneumatic pressure source, and the outlet port being connected to the pneumatic input of the shift mechanism.Thus, for example, shifting of a transmission gear box between low and high ranges is allowed only upon vehicle clutch conditions, particularly clutch hydraulic fluid pressure, reaching a predetermined value.

Thus, for example, the driver may be able to preselect the shift range such as from low to high, but he can shift between ranges only if the clutch hydraulic fluid reaches a preset pressure such as 1 80 psi or above.

According to a third aspect of the present invention, a vehicle has an engine and, between the engine and a road wheel, a hydraulically operated pedal-controlled clutch and a gear box having a pneumatically operable shift mechanism for shifting the gear box from one range of gear ratios to another, and a fluid flow control valve between a pneumatic pressure source and the shift mechanism, the control valve having operating means connected to be controlled by the hydraulic pressure operating the clutch to open the control valve when the hydraulic pressure exceeds a first predetermined pressure to provide communication between the source and the shift mechanism and to close the control valve and connect the shift mechanism to a vent when the hydraulic pressure falls below a second predetermined pressure which is not higher than the first.

The invention may be carried into practice in various ways but one fluid flow control valve and the manner in which it may be used to control the shift mechanism of a truck gear box will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a sectional, enlarged elevational view of the fluid flow control valve; and Figure 2 is an end view of the valve shown in Fig. 1 taken in the direction ll-ll.

The fluid flow control valve 10 depicted includes an elongated housing 1 2 having a passageway 1 4 extending the length thereof, from one end to the other. At one end of the housing is a connector cap 1 6 threadably connected to the housing, and having a threaded socket 1 8 for connection to a pressurized air source to communicate with the passageway 1 4 through a pressurized air inlet port 18'. At the opposite end of the housing and passageway from port 18' is an inlet port 22 for hydraulic fluid. Intermediate the ends of the housing and communicating with the passageway is an air outlet 24. Also extending from passage 1 4 at a position toward the end containing the inlet port 22 is a vent opening 26 to the ambient atmosphere.

Above the inlet port 22 is threaded connecting means 28 for connection of the valve housing to a coupling containing hydraulic fluid from the clutch slave cylinder located on the pressure side of the clutch allowing the port 22 to be exposed to the pressure of the clutch hydraulic fluid contained in the clutch control system.

Intermediate the ends of the passage 14 is a sleeve 32 having a central opening and including a valve seat 34 on one end thereof around this central opening. Positioned at this valve seat is a ball valve element 36. The valve element 36 is normally biased into engagement with the valve seat 34 by a compression coil spring 38 extending be tween a cup 40 abutting the valve element 36 on one end of the spring and an annular fixed retainer 44 and filter element 42 both of which are retained by the housing 1 2 at the other end of the spring.

At the end of the housing containing the inlet port 22 is a shiftable piston 50. It includes an annular seal such as an O-ring 52 therearound engaging the cylindrical portion of the passage in which this piston is rectili nearly shiftable axially of the valve. A retain ing ring 54 limits outward movement of the piston toward the port 22, while a shoulder 56 in the valve housing limits inward move ment of the piston in the direction toward the valve element 36.

Extending axially from the piston 50 is a piston rod 58, the outer end of which includes an axial internal passage 60. This end of the piston rod extends up through the central opening of the sleeve 32 with clear ance between the sleeve and the piston rod for air flow except at the end of the sleeve toward the piston where an O-ring seal 64 is positioned. The axial passage 60 extends along the piston rod. One end is at the axial end of the piston rod adjacent the ball valve element 36 where the ball valve is cooperative to close the passage under controlled conditions. The passage extends to the opposite side of the seal 64 where it leads into an outlet 60' communicable with the vent passage 26.The opposite end of the passage 60 is communicable, when not closed by the valve element 36, with the passage 24 to the conventional gear box shifter 25 (shown schematically) by way of the part of the passage 14 between the ball 36 and the seal 64.

Extending around the piston rod 58 from the piston 50 to a retaining shoulder fixed in the housing is an elongated compression coil spring 70 which biases the piston 50 and the piston rod away from the valve element 36.

In operation, when the hydraulic fluid pressure at the inlet port 22 is low, i.e. insufficient to overcome the bias of the compression spring 70, the piston 50 will be at its position toward the stop ring 54. That is, the piston rod 58 is biased away from engagement with the ball valve element 36. The compression spring 38 under these conditions will cause the ball valve 36 to be biased into engagement with its annular seat 34 so as to prevent any flow of pressurized air from the pressurized air source 20 through the port 18'.

Further, the piston rod 58, being biased away from the ball valve 36, will allow venting of any pressurized air in the gear box shifter 25 through the port 24, through the open end of passage 60 adjacent the ball 36, out of the lateral port 60' to the lower end of the passage 14 and out of the vent passage 26.

As the pressure of the hydraulic fluid at port 22 increases, the piston 50 is shifted increasing amounts against the bias of the spring 70, moving the piston rod 58 and its upper end toward and ultimately into engagement with the ball valve element 36 to close off the passage 60. This prevents further venting of the gear box shifter. Increased pressure then lifts the ball valve 36 by the piston rod 58 off the valve seat 34 against the bias of the compression spring 38 to allow pressurized air from the source 20 through the port 18' through the filter 42 and past the ball 36 to the passage portion 14' to port 24 and ultimately to the gear box shifter 25 to allow the operator to shift the gear box selector as from low range to high range. When the clutch pedal is released, the hydraulic fluid pressure at port 22 will decrease to a point where the compression spring 70 again shifts the piston 50 to allow the ball valve 36 to drop into engagement with its seat 34, thereby preventing further pressurized air from flowing through the gear box shifter. Further decrease in hydraulic pressure will retract the piston rod 58 away from the ball 36 to open the passage 60 and allow the gear box shifter to vent as explained previously.

Claims (5)

1. A fluid flow control valve comprising: body having an elongate passage therein with a pressure port having means for connecting the passageway with a first pressurized fluid, a second port serving as an inlet port to the passageway for a second pressurized fluid and an outlet port in the body from the passageway intermediate the pressure and inlet ports; a valve element and a valve seat in the passageway between the inlet port and the outlet port, and a spring for biasing the valve element against the seat; a piston reciprocatable in the passage and a rod extending in the passageway from one side of-the piston toward the valve, the other side of the piston being in communication with the pressure port; biasing means for biasing the piston and rod away from the valve, and the piston and rod being shiftable toward the valve element by fluid pressure at the pressure port to engage, at a predetermined fluid pressure, the valve and shift it off the seat to allow the second fluid to flow from the entry port to the outlet port.

2. A control valve as claimed in Claim 1 which includes a vent in the housing and a passage in the rod between the valve element and the vent to allow venting of the second fluid.

3. A fluid flow control valve substantially as described herein with reference to the accompanying drawings.

4. A vehicle having an engine and, between the engine and a road wheel, a clutch operated by a hydraulic motor and a gear box having a pneumatically operable shift mechanism for shifting the gear box from one range of gear ratios to another, a pneumatic pres sure source, and a fluid flow control valve as claimed in any of the preceding claims, the means for connecting the passageway with a first pressurized fluid being connected to hydraulic input to the hydraulic motor, the inlet port being connected to the pneumatic pressure source, and the outlet port being connected to the pneumatic input of the shift mechanism.

5. A vehicle having an engine and, between the engine and a road wheel, a hydraulically operated pedal-controlled clutch and a gear box having a pneumatically operable shift mechanism for shifting the gear box from one range of gear ratios to another, and a fluid flow control valve between a pneumatic pressure source and the shift mechanism, the control valve having operating means connected to be controlled by the hydraulic pressure operating the clutch to open the control valve when the hydraulic pressure exceeds a first predetermined pressure to provide communication between the source and the shift mechanism and to close the control valve and connect the shift mechanism to a vent when the hydraulic pressure falls below a second predetermined pressure which is not higher than the first.