IL29867A - Pneumatic control system - Google Patents

Description

PNEUMATIC CONTBOL SYSTEM This invention relates to a pneumatically operable control system for the programmed control of working and switching operations.

Compressed air has recently been used in control systems as a means for transmitting control commands. For instance, when the piston of a working cylinder moves in one direction, an actuating element connected to the piston may actuate a spring-loaded valve in such a manner that the movement of the. piston is stopped or reversed. Such a control function can be relatively easily performed by conventional means and with a small control equipment expenditure. The provision of conduits connecting the control system units does not involve any difficulties, A different situation will be obtained if a plurality of working cylinders are used for different operations, which are interdependent or interrelated. In this case, the number of control system units is also much larger and the conduit system connecting them becomes more complicated. The conduit system must have numerous Junctions and the multiplicity of conduits may become so entangled that even a person skilled in the art is confused in the case of a fault.

In a known system, the valves for controlling the working air are actuated by an air stream which is under very low pressure, „e.g. , 100-300 millimeters water. This results in a laminar flow in the conduits so that the air stream can flow past two opposite openings without escaping laterally. When a transverse stream enters one. of the lateral openings* however* the weak. ir . stream will be destroyed by turbulence and the air will escape into the, open through the other lateral opening.

Similar means are used for redirecting the actuating air at Junction. A . pulse . of air supplied in a suitable manner , directly to the junction may cause a change of the lamina flow of actuating air from one direction to the other.

The low-pressure system which has been described has the advantage that only few mechanical parts are required, but has also a disadvantage* which may cause frequent troubles. In this system too, a large number of conduits are required* depending oh the nature of the oontrol operations* .and the conduit systems are even more complicated. Besides, the actuating air pressure is so low that even a weak external air draft can cause a failure of the control system.

All control systems which have been described hereinbefore have the disadvantage that a change of the workin program requires numerous changes in the connections of the system. These changes require much time and expenses. ....

It is an object of the Invention to provide . a pneumatically operable control system which is free of the disadvantages which have been pointed out and requires only a minimum conduit expenditure and a clearly arranged conduit system* and enables a change of the conduit system to different conditions required for a change of the working program without the need for a structural alteration of the conduit system and without a loss of time.

According to the present invention, there is provided a pneumatic control system comprising a plurality of inlet conduits extending in one direction and a plurality of outlet conduits extendin in a second direction and crossing the inlet conduits at crossing points wherein transfer connections between the inlet and outlet conduits are provided, inlet valves for controlling the flow of air into the inlet conduits, and transfer control means for selectively opening and closing the transfer connections to control the flow of air in the outlet conduits in dependence upon the flow of air in the inlet conduits.

In order to avoid a return flow of air from the outlet conduits into the inlet conduits, a check valve may be incorporated in each transfer connection.

A special advantage of the system according to the invention resides in that it enables a desired circuit arrangement to be set up within very short time. For this purpose, a transfer control valve may be provided at each crossing and may be arranged to close the transfer connection in one limit position which may be assumed by simply moving in an actuating member, whereas in the other limit position, e.g., when the actuating member is withdrawn, they open a path for the flow of the air from the inlet conduit valves may foe actuated by pneumatic double acting actuators and when open, allow the flow of air into the inlet conduits. In such an arrangement* an Incoming air pressure pulse can be used to move the eliding control valve into an open position to open a path for a continuous flow of actuating air. In a different arrangement these sliding control valves derive an air pressure pulse from a continuous air stream. Thus, the continuously supplied air flowing through the sliding control valve may act on the latter so on to close the valve.

The sliding control . valves may be replaced by valves of different type, such as valves provided with d&phragms, sealing discs, etc. Solenoid valves may be provided at the inlet ends of the inlet conduits to enable electrical control to be employed.

The pressure and rate of the air flowing in the duifclet conduits may not be sufficient for the performance of operations involving a substantial amount of work. For this meason the outlet conduits can be connected to relay valves which are actuated by the air in the outlet conduits and control the working air which operates the working devices.

It will be understood that the control system according to the invention inay be used in low-pressure systems. In this case, all the outlet conduits may be connected to a single supply conduit. The low-pressure air flows through the supply conduit and the outlet conduits to relay valves, which are provided at the end of the outlet conduita and closed under the. action of the weak air stream* Die outlet conduits are provided at each crossing with. a port which lies opposite the transfer connection. When the transfer control valve is open. the. turbulence created by the air which is blown from the inlet conduit across the outlet conduit to the port will destroy the weak air stream so that pressure- is no longer applied to the associated relay valve. The relay valve thus opens to supply working air to the working device controlled thereby.

The invention will be described in more detail , by way of example, with reference to the accompanying drawings, in whicht ' Fig. 1 is a diagrammatic view showing the control block of a pneumatic control system.

Fig. 2 shows the crossing between one inlet conduit and two outlet conduits of the control system in Fig, 1 in section, Figs. 3 and k are diagrammatic views showing different eliding control valves of the control system.

Fig. 5 is a diagrammatic view showing a control system in combination with a functional, diagram of a fully automatic deep-drawing press, and Fig. 6 is a diagrammatic view, showing a control system for a modified mode of operation.

The diagrammatic Fig. 1 shows a housing 1, which is formed from a solid block having a plurality of parallel , horizontal ducts spaced one above the other( having the same length and constituting inlet conduits 2. Vertical ducts of the same length are arranged behind the inlet conduits 2 and constitute outlet conduits 3» which are spaced from the inlet conduits 2 and cross them. Inlet valves ¾ are provided at the inlet ends of the inlet conduits 2 and outlet valves consisting of relay valves 5 · ,are provided at the outlet ends of the outlet conduits.

Fig. 2 shows the crossing points between one inlet conduit and two outlet conduits. At each crossing point there is provided >a transfer connection 11 which can be closed by a transfer control valve 7· The left-hand valve 7 is shown in closed and the right-hand valve is shown open. Each transfer control valve 7 has a head 8 for manual operation thereof and, is guided in a bushing 10. Each transfer connection 11 between an inlet conduit 2 and an outlet conduit 3 is also provided with a check valve 13t which is loaded by a spring 12 to allow air flow only from the inlet conduit to the outlet conduit. The check valve 13 can be installed by removing a rear cover plug 4, In the embodiment of Fig. l air enters any inlet conduit 2 whose inlet valve is open and flows rom any such inlet conduit to any outlet conduit communicatin therewith via an open transfer control valve, thereby opening the .corresponding relay valve or valves 5. The actuated relay valves pass air ' from a supply valve indicated schematically at 6 to whatever devices are connected to be controlled by the relay valves.

Figs. 3 and k show sliding salves 20 and 2 which may be used as the inlet control valves ¾ or as the relay valves 5· T e sliding control valve 20 which is shown in Fig. 3 comprises a spool 21, which is smaller in diameter than the piston 25 integral therewith and is axially guided in three sealing rings 22 and formed with an annular groove 23 which, when the spool is moved to the le t by :an air pulse P, connects the incoming air conduit ^ to. the outgoing air conduit 2¾b. The spool Is moved back to the right to shut off the connection by an air pulse applied at Q.

In this arrangement, the sliding control valve 20 serves to deliver a continuous air fstream in response to an air pressure pulse acting on the surface of the piston 25.

The sliding control valves 26 according to Fig* ¾ has the same design as the sliding control valve 20 in Fig. 3 but has a different function as a result of a different arrangement of the incoming and outgoing conduits. The sliding control valve 26 in Fig. is so arranged that in its open position (as illustrated) air supplied in conduit 30 flows in the annular grovve 31 into the conduit 32 and from the latter through a branch conduit 33 to the piston face 3^. ' This causes position and to deliver only a pulse rather than a continuous stream* A plurality of, valves as shown in Fig. 3 can be connected in cascade so that, as each valve is opened the air flowing in the valve outlet conduit 2 b nnt only flows to the corresponding inlet conduit 2 ( ig. l) but also shuts the preceding inlet control valve.

In Pig. 5» a control system 51 comprises open transfer control valves 53 and closed transfer oontrol valves 2 controlling the flow paths for the air in accordance with the embodiment of Fig. 1. Conduits 6 connects relay valves 5^» 55, o a cylinder 57» which contains a double acting piston 58 for feeding the stock contained in a magazine 59· A rod 60 of the piston 58 has a stop 6l cooperating with limit valves 73 and ¾, A second cylinder 62 is supplied with air through conduits 63» which are connected to relay valves 64, 65. A piston 66 in the working cylinder 62 has also a stop 67 cooperating with a limit valves 75 and 76. Conduits 68 connect inlet valves 69, 70, 71» 72 to the limit valves 73. 7 , 75. 76.

The function of a deep-drawing press provided with a control system according to the Invention will be described with reference to Fig, 5.

When the piston 58 is retraoted in the feeding cylinder 57 the stop 6l actuates. the limit valve 73 and the inlet valve 72 is opened. Air flows through this valve and causes the relay valve 6 to open so At the end of this movement, the stop 67 actuates the limit valve 75» opening the valve 71 and closing the valve 72. The air entering through the inlet valve 71 opens the relay valve 6h so that the piston 66 of the cylinder 62 returns upwardly until the limit valve 6 is actuated. The valve 71 is closed and the valve 70 opened, whereby air flows through the inlet valve 70 to open the relay valve 51* so that the piston 8 of the cylinder 57 moves forwardly and feeds one blank from the magazine 59 ready for the next drawing operation. The limit valve 7^ is actuated at the same time eo that the inlet valve 69 initiatee the opening of the relay valve 55» the valve 70 closes, and the piston 58 of the cylinder 57 returns to its initial position.

The valves 69 to 7 can be connected in cascade as mentioned above so that, as each is opened by the associated limit valve, it closes the preceding inlet valve.

Manually operable valves 79 and 80 can be used to open and shut respectively a valve 77 which controls the supply of compressed air to the limit valves and inlet valves, whereby the press can be started and stopped.' The control system shown in Fig. 6 is actuated by compressed air under low pressure. Inlet conduits hz provided in a housing ¾1 are again crossed by outlet conduits which in this case are connected to a common supply conduit hh for producing the stream of low-pressure air from a source o supply. .

At each crossing point, the outlet conduit is connected to the. inlet conduit kz by a transfer connection, which can be. closed by a transfer ' control valve, not shown. Opposite. he. transfer - connection, a port extends from the outlet conduit to atmosphere. When none of the transfer .control valves associated with an outlet conduit, is open, air flows through that conduit, to close a corresponding relay valve When any transfer control valve is open arid the inlet control valve , h of the corresponding inlet conduit ¾2 is open, ir blows across the outlet conduit from the transfer connection to the port opposite and deflects the weak air stream. The corresponding relay valve ¾5 thus opens, The inlet and outlet conduits need not be provided in a unitary block as in the embodiments of Figs. 1 and 6. Standard transfer valve units. ca be assembled to make up the structure of csurssing conduits.

Claims (11)

WHAT IS CLAIMED ISt

1. A pneumatic control system comprising a plurality of register like arranged inlet conduits extending in one direction and a pluralit of outlet conduits extendin in a second direction and crossing in distance the inlet conduits at crossing points wherein transfer connections between the inlet and outlet conduits .are provided, inlet valves for controlling the flow of air into the inlet conduits, and transfer control means for selectively opening and closing the transfer connections to control the flow of air in the outlet conduits in, dependence upon the flow of air in the inlet conduits*

2. A system according to claim 1, wherein the transfer control means.are transfer valves each of which, when open, allows air to flow from the correspondin inlet conduit into the corresponding outlet conduit.

3. A system according to claim 2, wherein each transfer connection is further provided with a check valve which prevents air flowing from the corresponding outlet conduit into the corresponding inlet conduit.

A system according to claim 2 or 3, wherein each outlet conduit is connected to a relay valve which is controlled by the air in the outlet conduit.

5· . A system according to claim , wherein the relay valves are opened by the air pressure in the outlet conduits.

6. A system according to claim 1, wherein the outlet conduits. are connected to a common supply of air for establishing an ai stream therethrough and wherein each outlet conduit has a port opposite each transfer connection, the arrangement, being suc that, when air flows from an inlet conduit through ah open transfer connection, it blows across the corresponding outlet conduit to the port opposite the transfer connection. and destroys the air stream flowing through the outlet conduit.

7» A system according to claim 6, wherein each outlet conduit is connected to a relay valve which is closed by the air stream flowing through the outlet conduit and opened when the air stream is destroyed.

8. A system according to any o claims 1 to 7t wherein the inlet valves are sliding valves which either respond to a actuating air pulse to supply a continuous air stream to the corresponding inlet conduit or respond to a continuous air stream supplied thereto to supply a pulse of air to the corresponding inlet conduit.

9· A system accordin to claim 8, wherein the inlet valves are so interconnected in sequence that* when one inlet valve is opened it causes the preceding inlet valve to close.

10. A system according to any of claims 1 to 9» wherein the inlet conduits* outlet conduits and transfer connections are formed in a unitary block.

11*. A pneumatic control system substantially as hereinbefore described with reference to and as illustrated in Fig. 1 of the accompanying drawings. 12· A pneumatic control system substantially as hereinbefore described with reference to and as illustrated in Pig, 6 of the accompanying drawings S