GB2038417A - Fluid Control Valve and Ram Containing Same - Google Patents

Abstract

A valve especially for controlling the flow of fluid to and from a ram cylinder 10 comprises a housing 13 having a tubular valve member 14 mounted therein and arranged to have a limited axial movement, the bore of the tubular valve member being in communication with a main port 23 in the housing and being selectively connectible to an exhaust port 17 and an inlet port 16. Movement of the member 14 from the limit position to the other is effected by selective pressurisation of chambers 19, 20 on opposite sides of a piston 15 on the outside of the tubular member. A valve may be mounted at each end of a ram, the valve member thereof being arranged so that at one end the bore of that tubular member communicates with the exhaust port and at the other end the bore of the other tubular member communicates with the inlet port. A signal applied to both valve members simultaneously will cause them to change the direction of the ram. <IMAGE>

Description

SPECIFICATION Fluid Control Valve and Ram Incorporating Same This invention relates to a valve for controlling fluid flow and also to a ram incorporating same.

The invention is particularly concerned with a pneumatically or hydraulically operated ram incorporating a valve according to the invention but clearly is not limited thereto as it may relate to the valve per se.

Firstly with regard to known pneumatic or hydraulic valves there is generally a problem in that the valve is required to operate against the pressure of the fluid being controlled. For example, a conventional poppet valve must be forced open against the pressure and this necessitates an initial force far in excess of the force required once the valve commences to open. In a situation wherein a poppet valve is used to control a large volume flow, that is the valve has a large cross-sectional area, at a high pressure, the force required to open the valve may be extremely high necessitating expensive fluid control equipment.

Secondly with regard to known pneumatic or hydraulic rams the fluid circuitry for controlling operation is relatively complex and costly.

Generally a control circuit is adapted to operate a main control valve or switch, associated with each ram, to switch high pressure fluid to each ram for each direction of movement of the ram.

Thus in large machinery where many rams are used at spaced locations the amount and complexity of the vast array of high pressure pipes, connectors and fittings necessary to transmit high pressure fluid to the rams is costly to provide and maintain. The problem could be avoided to some extent by arranging the control valve or switch on its associated ram, or forming it integral therewith. Mounting the valve or switch on the ram reduces the amount of high pressure pipe but not the fittings. Forming the valve or switch integral with the ram in the case of conventional control valves or switches introduces further problems. For example, the complexity and cost of the ram is greatly increased and the versatility of the ram is reduced due to the increase in physical size and bulk of the ram.

Thus it may be an object of this invention to provide an improved fluid control valve which avoids or at least reduces the aforementioned problem of known fluid control valves.

A further object of the invention may be to provide an improved pneumatic or hydraulic ram having one or more fluid control valves formed integral therewith, which ram does not suffer the aforementioned problems of known rams.

Accordingly one broad form of the invention which may be preferred provides a fluid control valve comprising a housing having a tubular valve mounted therein for limited axial sliding movement, said valve member being open at its ends and the bore thereof communicating with a main outlet port in the housing, a main inlet port and an exhaust port in said housing arranged such that said sliding movement in one direction closes said inlet port from communication with said bore and opens said exhaust port for communication with said bore whereas said sliding movement in the other direction opens said inlet port for communication with said bore and closes said exhaust port from communication withs said bore, said housing and said valve member cooperating to define first and second control chambers, said chambers being separated such that a difference in control fluid pressure between said chambers causes said axial sliding movement and first and second control ports in said housing communicating respectively with said first and second chambers for facilitating connection of control fluid to said chambers.

According to one more particular form of the invention which may be preferred said valve member is cylindrical, said inlet ports are arranged adjacent opposite ends of said cylinder, said first and second control chambers are annular chambers extending along the outer side of the valve member and are separated by an annular protrusion extending around the outer surface of said cylindrical valve member.

According to an alternative more particular form of the invention which may be preferred said valve member is cylindrical said inlet and exhaust ports are axially spaced between the ends of said valve member and a hole is arranged through the wall of said valve member such that said sliding movement in said one direction aligns said hole with said exhaust ports whereas said sliding movement in said other direction aligns said hole with said inlet port and said and second control chambers are mutually opposed annular chambers respectively arranged at opposite ends of said valve member, said chambers being closed by respective ends of valve member such that pressure in said chambers causes a force on respective end faces of said annular valve member.

Preferably, said outlet port is co-axial with, and substantially the same diameter as said bore of said cylindrical valve member.

According to another broad form of the invention which may be preferred there is provided a pneumatic hydraulic ram having a fluid control valve incorporated in one end of the ram, said valve comprising a tubular valve member mounted in an end housing of the ram for a limited axial sliding movement, said valve member being open at its ends and the bore thereof communicating with the bore of the ram, a main inlet port and an exhaust port in said housing arranged such that said sliding movement in one direction closes said inlet port from communication with the bore of said member and opens said exhaust port for communication with the bore of said member whereas said sliding movement in the other direction opens said inlet port and closes said exhaust port, said housing and said valve member co-operating to define the first and second control chambers, said chambers being separated such that a difference in fluid pressure between said chambers causes said axial sliding movement and first and second control ports in said housing communicating respectively with said first and second chambers for facilitating connection of control fluid to said chambers.

According to one more particular form of the invention which may be preferred said valve member is spring biased in said one direction such that in the absence of said contol fluid pressure said ram is able to retract and is thus a mono-stable ram.

According to a still further particular form of the invention which may be preferred a further similar fluid control valve is incorporated in the other end of the ram so as to provide a double acting ram.

In the case of said double acting ram one said fluid control valve may have its valve member spring biased in said one direction and the other said fluid control valve may have its valve member spring biased in said other direction so as to provide a monostable double acting ram.

Preferably said bore of said valve member is co-axial with said bore of said ram.

In order that the invention may be more readily understood, particular embodiments will now be described in detail with reference to the accompanying drawings wherein, Figure 1 is a schematic sectional representation of a double acting pneumatic ram according to one embodiment of the invention and Figure 2 is a similar view to Figure 1 of a further embodiment of the invention.

In the drawings like reference numerals designate like or similar parts as between the two embodiments.

From the drawings it can be seen that the ram generally comprises a ram cylinder 10 having a piston member 11 slidably arranged therejn and connected to a rod 12 for transferring movement by the piston to an external member (not shown).

Each end of the ram cylinder 10 is closed by means of an end housing 13. Each end housing 13 incorporates a fluid control valve for controlling movement of the piston 11 within the cylinder 10.

Referring now to Figure 1 each control valve consists essentially of a sleeve member 14 slidably arranged within the respective housing 13. The sleeve member is cylindrical and has an outwardly protruding annular portion 1 5 extending therearound. The sleeve 14 is arranged in a suitable cavity in the housing 13 and is adapted to slide axially a limited amount as will be described below.

A fluid inlet port 16 and a fluid exhaust port 1 7 are arranged in the end housing 13 to communicate with the bore of the sleeve member 14 depending upon its axial location within the housing. A number of ring type seals 1 8 are arranged in the housing to form a seal between the housing and the sleeve member 14.

The end housing 13 is shaped internally to cooperate with the sleeve member 14 to provide first and second control chambers 1 9 and 20 respectively. The control chambers 1 9 and 20 are annular chambers which extend around the outside of the sleeve member 14 and communication with each chamber is via a fluid control port 21 and 22 respectively.

A main air supply (not shown) is provided at each fluid inlet port 16 by means of suitable pipe (not shown). The main air supply to the inlet ports 1 6 is a permanent supply. In other words the air supply pressure is present at-each inlet port at all times when the system isin operation. in a situation where a number of the rams are arranged at spaced intervals in a machine a main air line may be arranged to pass by each ram with a suitable tee piece therein to provide a line to each inlet port. In this manner the complexity of the main air supply is considerably reduced.

An outlet port 23 is arranged in each endhousing 13 and provides communication between the bore of the sleeve member 14 and the bore of the ram cylinder 10. As it is clear in Figure 1 with the sleeve members 14 in position shown, air from the inlet port 16 at the left hand end of the diagram is to flow through the centre of the sleeve member 14 and into the ram cylinder 10 on the left hand side of the piston thus causing the piston to move in the direction of the arrow.

Air on the right hand side of piston is forced out of the exhaust port 1 7 of the control valve at the right hand end of the cylinder. During this period the exhaust port in the control valve at the left hand end is blocked as is the inlet port 1 6 of the right hand end.

Movement of the sleeve members 14 is achieved by a low pressure fluid control circuit (not shown) which is connected to the respective control valves in a manner represented by the dotted lines in the drawing. As shown a low pressure fluid control signal 24 is connected by a suitable line to the control port 21 of each valve.

Similarly a low pressure control signal 25 is connected-to the other control port 22 of each valve. A signal on 24 will cause the ram to extend whereas a signal on 25 will cause the ram to retract.

Reference should now be made to Figure 2 of the drawings. Similar to the Figure 1 embodiment air-line pressure is connected to port 1 6 in both cylinder end caps. Ports 1 7 are open to atmosphere either directly or through flow controls (not shown). Inside each end-cap is a sleeve 1 4a and half-way along the axial length of each sleeve 1 4a is a series of radial holes or slots 36 connecting the outside of the sleeve with the inside. The sleeve is carried in a cartridge 35 which has similar through-holes aligning with ports 16 and 1 7. Also passing through the cartridge are connect-holes for pilot or control ports 21 and 22. By means of suitable seals 31, 32, 33 and 34 the pilot zones or control chambers 1 9 and 20 at each end of the sleeve are sealed off from the main flow ports 16 and 17. Similarly a suitable seal 30 prevents communication between ports 1 6 and 1 7 when the sleeve 1 4a is in either end position. During transition of the sleeve 1 4a there is a brief moment when both ports 1-6 and 1 7 communicate with holes or slots 36 but this does not adversely affect operatipn of the device.Similarly it may be preferred to position ports 16 and 17 so that during transition of sleeve 1 4a communication is prevented between said ports 1 6 and 1 7 and holes or slots 36 thereby giving a sealed mid-position to sleeve 14a. The outer edges of the holes or slots 36 have a slight chamfer to allow the seal 30, which may be a rubber '0' ring, to glide thereover.

When a pressure signal is applied to port 21 it passes into chamber 1 9 and provided chamber 20 is exhausted or at a lower pressure than the signal iin port 21, the sleeve 14, in each end-cap is drivenjfrom left to right as shown in Figure 2. This opens the inside of the ram cylinder 10 on the left hand side of piston to atmosphere (via hole 36 and port 17) and simultaneously opens the inside of cylinder 10 on. the right hand side of the piston 11 to line pressure via port 1 6 and hole 36. This causes the piston to move to the left as shown by the arrow.

Similarly by exhausting ports 21 and applying a pressure control signal, which can be of short duration because the valve is bi-stable, the sleeves 14 will be driven to the left hand side and the piston 11 will be driven to the right.

By placing a suitable spring in zones 19 in each end-cap, the valves will become mono-stable and when no pilot signals are present the piston 11 will move to the left. Similarly by placing sutiable springs in zones 20 the piston 11 will move to the right in the absence of pilot or control signals.

The advantage of a cartridge type valve is that it can be installed and removed as a complete unit, thus change-over, should failure occur, can be accomplished easily and quickly.

It will be evident to those skilled in the art that the rams described above provide a significant improvement over the prior art. Firstly the incorporation of a control valve in each end of the ram obviates the need for a separate directional control valve (DCV) and the associated pipes and fittings. Secondly the simplicity of the valve facilitates production of a ram which may not cost substantially more than a conventional ram to produce. The simplicity of the valve also enables the size of the ram to meet specifications as it does not greatly increase the length of the ram and since there is not protrusion beyond the normal diameter of the ram, other than fittings, the ram does not become less versatile than conventional rams.

Thirdly the use of sleeve valves according to the invention completely eliminates return lines between the ram cylinder and the DCV which would exist with conventional rams. Exhaust is direct to atmosphere or via flow controls and thus quick exhaust valves are not required.

Fourthly, the invention provides for a potentially faster operation of a pneumatic or hydraulic ram since there are less complications and obstructions to fluid flow and main air pressure is immediately available at the ram. This latter feature is due to the fact that air is not forced out of the one end of the ram back into the supply line and through the DCV to exhaust to atmosphere when the ram piston returns. This removes the necessity to fill the supply line at the commencement of the next operation with pressurized air, as occurs with conventional rams, thus also provides for a saving in compressed air which could become significant.

Fifthly, the use of small return springs in the sleeve or control valve of the invention enables provision of a mono-stable ram without the need for a heavy spring on the piston as occurs with conventional rams. Thus the main actuating force does not have to act against a heavy spring and the length of the ram may be less as there is no need to account for the compressed length of the heavy spring.

Of course the invention is not limited to double acting rams as described and could be applied to a single acting ram having a control valve, as described above, incorporated in one end. Also the invention may comprise of a sleeve valve per se.

It is desirable, but not essential, to make the bore of the sleeve member 14 or 1 4a of the same diameter as the inlet supply line and then the valve member does not restrict the fluid flow in any significant way. The sleeve member 14 or 1 4a may be conveniently formed by normal engineering production methods from a wide variety of materials including plastics. According to some modifications of the invention the sleeve may be a tube other than of cylindrical section and the ports may be differently oriented provided sliding movement of the sleeve serves to block the inlet port and open the exhaust port, or vice versa.

Since modifications within the spirit and scope of the invention may be readily effected by persons skilled in the art it is to be understood that the invention is not limited to the particular embodiments described, by way of example, hereinabove.

Claims (4)

Claims

1. The valve, when incorporated in either end of a ram, serves a number of functions normally covered by individual pieces of conventional equipment, the two main ones being the directional control valve and a quick exhaust valve.

2. Pipe work is considerably reduced requiring only a fluid upply and two small signal tubes.

These may be normally only 1/16 inch bore.

Because the main supply lines do not have to return the fluid as the ram reverses, the exhaust going to atmosphere in the case of pneumatic operation or via a return line in the case of hydraulics, a higher operating speed is achieved.

3. Flow control valves may be used in the exhaust ports giving speed control, these being a simple screw type or a fixed orifice type when no adjustment is required. The latter being more desirable in certain conditions as it offers protection against accidental or unauthorised misuse.

4. The cost of the valve components should not increase the ram by any appreciable amount, and definitely not as much as the total cost of a ram and a suitable conventional control valve.