US3786836A

US3786836A - Pneumatic timer

Info

Publication number: US3786836A
Authority: US
Inventors: L Kleven
Original assignee: UNIFLO SYSTEMS CO
Current assignee: UNIFLO SYSTEMS CO
Priority date: 1972-06-02
Filing date: 1972-06-02
Publication date: 1974-01-22
Anticipated expiration: 1991-01-22

Abstract

A pneumatic timer which provides a pneumatic signal for a preselected length of time for use in operation of pneumatic systems and which includes means for varying the timer period of the timer in response to an external signal.

Description

United States Patent 1 Kleyen Jan. 22, 1974 PNEUMATIC TIMER 3,530,890 9 1970 Bird 137/624.14 [75] Inventor: Lowell A. Kleven, Bloomington, 82:3:

Minn

[73] Assignec: Uniflo Systems Company, Edina, Primary Examiner A|an Cohan Attorney, Agent, or I"irm- Dugger. Johnson & 221 Filed: June 2, 1972 Westman [21] Appl. No.: 259,169

[57] ABSTRACT [52] U.S. Cl. 137/624.2 [51] Int. Cl. Fl6k 31/365 A neumatic timer which provides a pneumatic signal Fleld of Search 137/624-1 for a preselected length of time for use in operation of 137/6 235/201 pneumatic systems and which includes means for varying the timer period of the timer in response to an ex- [56] References Cited ternal signal.

UNITEDSTATES PATENTS 3,326,237 6/1967 Frick 137/624.l4 14 Claims, 5 Drawing Figures TIME PERIOD SET POINT PRESSURE SIGNAL OUTPUT OF TIMER TlM ER START PRESSURE SIGNAL PATENTED JAN22 I974 saw 2 or 2 PDnEIDO WU-N k PNEUMATIC TIMER BACKGROUND OF THE INVENTION 1. Field of the Invention.

In the present invention it is in relation to fluid actuated pneumatic timers.

2. Prior Art.

In the use of levitated vehicle systems, it has been found that where the controls for the vehicle are all track mounted, the speed control of the vehicle can be controlled automatically through the use of appropriate time periods for controlling thrust to the unit. The present device relates to a unique timer for controlling pneumatic timing periods.

SUMMARY OF THE INVENTION The present invention relates to a fluid actuated or pneumatic timing system which utilizes a basic diagram swept volume chamber and'for delivering a fluid pressure signal during the time necessary to sweep the volume of the chamber, and which includes means for varying the time necessary for sweeping the volume of the chamber.

In one form of the invention, the amount of air being supplied to the swept volume chamber is changed so that the sweep time period is changed correspondingly. In a second form of the invention, the pressure of the air supplied tothe swept volume chamber is varied in accordance with preselected signals to change the necessary time to sweep the chamber. The swept volume chamber is also referred to as a pneumatic capacitor. The present timer is used primarily in combination with levitated vehicles, as shown in US. Patent applica- BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a part schematic representation of a timing device made according to the present invention;

FIG. 2 is a sectional view of a typical shuttle valve arrangement used with the device of FIG. 1;

FIG. 3 is a sectional view taken as on line 33 in FIG. 1 showing a typical valve assembly used with the present invention;

FIG. 4 is a part schematic representation of a modified form of the present invention showing a pressure regulator means for varying the time period of the timer; and

FIG. 5 is a sectional view of a temperature compensating variable size orifice used with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The timers of the present invention are designed primarily for use in connection with levitated vehicle speed control, but function for universal use as timers in pneumatic systems.

The timers have a normal time period and this time period can be varied within a range from a longer than normal time period to a less than normal time period in relation to a signal, called a set point signal, which will cycle the time across the variable time period. If the timer is activated during this variable time period the timer output signal will be either longer or shorter than the normal time period, depending on conditions when the timer is tripped. The variable time period expires on a time basis after the set point signal has started the variable timer period cycling.

Referring now to FIG. 1, an example of a specific timer module is shown part schematically.

The timer is shown in its rest or unactivated position and is composed of a pneumatic monostable multivibrator (which is a one shot), the input from a timer starting device, the output line of the timer to supply a pressure signal and the signal line for starting the variable time sequence (set point signal) together with the associated mechanism for varying the time of the one shot. The one shot is composed of two inverting valves, three diaphragm swept volume chambers, which may be referred to as pneumatic capacitors, an OR gate, and the necessary bleeds, orifices and check valves. This is a fully pneumatic timer.

The basic timing diaphragm swept volume timer housing is shown at 25 and comprises a housing having a diaphragm 26 extending thereacross, forming two chambers and having a first input line or conduit 27 and a second line or conduit 28 leading therefrom. The line 28 has a restriction orifice 29 at one end thereof, and this orifice is open to duct pressure, or in other words to a pressure source higher than atmospheric pressure. Duct pressure inputs are indicated by P and atmospheric pressure inputs are designated A on the drawings. In use in a levitated vehicle track, the timers will be located inside a duct having a pressure of about 1 to 2 PSI gage. In addition, the line or conduit 28 is connected into a line containing a restriction orifice 30 that leads to atmospheric pressure (indicated as A) at its outer end. Line 28 also opens to a control valve housing 31 that has a diaphragm 32 dividing the base of the housing into two chambers, and the chamber on the side of the diaphragm 32 opposite from the opening through line 33 (which is connected into line 28) is open to atmospheric pressure through a passageway 34. Diaphragm 32 is attached to control a sliding valve 34A, which is shown typically in FIG. 3, that seals around an opening 36 leading to duct or plenum pressure. It should be noted that when the timer is used in apressurized duct these openings can merely be open right to the duct. In the quiesent or at rest stage of the timer, the valve 34A is held closed by the pressure on diaphragm 32 set up by the ratio of orifice or restriction 29 to restriction 30. The output line or conduit 39 of the timer leads from the chamber 37 in which the valve head 35 operates.

A further control of the timer is a valve housing 40, which has a first chamber 41 and a port or passageway 42 leading from duct pressure into this chamber 41. Flow through the passageway 42 is controlled by valve 43, and the line 27 to the basic timer housing 25 is connected to chamber 41 to carry the pressure coming through the passageway 42 to the basic timer housing when the valve is open. In its quiesent stage, as shown, the valve 43 is open, and this seals off a passageway so that fluid under pressure cannot flow into the second chamber 44 of the housing 40. Second chamber 44 is divided with a diaphragm 45, and on one side of the diaphragm 45 there is a passageway 46 leading to atmospheric pressure. On the opposite side of the diaphragm 45 from the valve 43, there is a shuttle valve or OR gate" illustrated generally at 47 in a chamber 44A formed by the diaphragm 45. The shuttle valve is typical of a form of OR gate used. As shown typically in FIG. 2, the timer start pressure signal line or conduit 38 and a second line or conduit 48 are aligned axially in chamber 44, and each has

small guide knobs

49 and 50, respectively, adjacent their ends. A small solid disc 51 mounted onto a shaft 52 that is slidably mounted in the ends of and is guided by the

knobs

49 and 50. The disc or button 51 can thus slide axially relative to the tube ends to close the opening to either tube or line when fluid under pressure flows into chamber 44A from the other tube.

Just by way of example, when fluid under pressure comes in through the line 38 from the item delivering a timer start signal the timer, buttom 51 would slide to the left as shown in FIGS. 1 and 2 close off the opening to the tube 48, and cause pressure to rise in chamber 44A and act on the diaphragm 45 moving the valve 43 upwardly so that the head of the valve 43 closes off the passageway 42. The line 48 in turn is open through .a check valve 53 at its opposite end to a diaphragm formed chamber which will be more fully explained. The line 48 also joins output line 39.

In the at rest stage, however, as shown in FIG. 1, the pressure input through line 38 is atmospheric, and the valve 40 through line 27 is high, moving the diaphragm 26 in the basic timer housing 25 all the way to the end of its movement. The basic time period of the timer is controlled by movement of diaphragm 26 and its effect on valve 34A.

Varying the time period for diaphragm 26 to sweep across the chamber of timer housing 25 is accomplished as shown with a pair of housings having sweep diaphragm chambers that are connected to the line 28. As shown, a line 57 is open to the line 28, and a restrictive orifice 58 is contained in this line. This orifice 58 can be of any usual or suitable design as desired. The line 57 leads directly into a chamber 59 formed in a housing 60 having a sweep diaphragm 61. An additional branch line 62 is connected to the line 57, and has a restrictive orifice 63 therein. The line 62 leads into a chamber 64 of a housing 65 which has a sweep diaphragm 65A and a spring 66 between the bottom of the housing and the diaphragm 65A in the chamber 64. The chamber 64 is also connected through a check valve 67 and a tube or line 68 to a time period set point pressure signal line or conduit 75 from a signal device 76. This signal device in a levitated vehicle system may be a vehicle detector on a track section. The line 75 opens through a check valve 69 to a chamber 70 which is on the opposite side of the diaphragm 61 from the chamber 59. Also, it should be noted that the line 48 is open through check valve 53 to this chamber 70, and a restrictive orifice 71 is provided leading from the chamber 70 to atmospheric pressure. The check valves here are shown merely as hinged gates over the ends of the tubing or lines utilized, but could be any desired check valve.

The line 48 is connected into the tube or line 39 so that the pressure output of the chamber 37 is felt both at line 48, and the OR gate 47, as well as being delivered through the line 39 as an output pressure signal for the timer.

The typical valve construction is shown in FIG. 3 and shows how the shanks of the valves are made to permit flow of fluid along the valve shanks when the head is lifted so it does not seal around the opening for the shank. The shank of valve 34A fits through the opening in the valve body and when the valve head is in position as shown in FIG. 1 fluid can flow past the shank and between the chambers in the valve. For an initial examination of the operation of the timer, the restriction or orifice 58 is assumed closed. Also assume for the first discussion that the check valve 53 is held closed to prevent the output of chamber 37 from entering the housing 60. When a pressure signal or sustained pressure along line 38 appears as a start signal this starts the timer running. The OR gate disc 51 will close against the end of tube 48 and the diaphragm 45 will be actuated to lift the valve 43 and close off the passageway 42 leading from duct pressure. The output of fluid under pressure through line 27 is thus reduced to zero and the diaphragm 26, which has been in the position shown in FIG. 1 starts to move toward the end of tube 27 because of pressure coming in through restrictive orifice 29. The pressure then in tube 28 actually reduces substantially to zero from duct pressure which had built up in the tube 28 through orifice 29 and at this stage there is essentially no flow in the orifice 30.

This reduces the pressure on diaphragm 32 because of the connection through the tube 33, so that the valve head 35 moves away from position closing off the passageway 36, and letting duct pressure flow through chamber 37, and into line 39 and line 48. The head 35 seals off the chamber 37 on the valve side of diaphragm 32 to lock on the OR gate 47 through line 48 and hold valve 43 closed if the pressure signal on line 38 was only a pulse. This would move the disc 51 against the end of tube 38, assuming that the signal in line 38 was no longer present, and would hold the valve 43 closed because of the pressure coming from chamber 37 through line 48.

All this action is occurring while diaphragm 26 is moving toward tube 27. After the diaphragm 26 reaches the extent of its travel toward line 27, the pressure in line 28 will rise immediately, as will the pressure in line 33, causing the diaphragm 132 to move the valve head 35 up against the passageway 36 to close off the output from chamber 37. As soon as this output from chamber 37 is removed from the line branch 48 leading to the OR gate 47, if there is no longer any signal on line 38, the valve 43 will open and the output from chamber 41 will again go to duct pressure causing the diaphragm 26 to return to its solid line position. The time during which there is an output from the chamber 37, or in other words the time the valve 35 is away from or opens the passageway 36, is the time interval. It should be noted that the diaphragm 26 of timer housing 25 will not be reset even through the output from chamber 37 is low, if there is still a signal on line 38, until this signal is removed to permit the valve 43 to move to its solid line position so that duct pressure is applied through the tube 27 to the diaphragm 26.

The operation of the unit is much the same with the time

period changing housings

65 and 60 added into the pneumatic circuit. In the pneumatic circuit, the restriction 58 prevents large increases in pressure at tube 28 from movements of the diaphragms in housings 60 tube 57 which is in the chamber 59. The diaphragm 61 is shown in its normal set point position, in other words in position for the nominal time for sweepof the basic timer housing 25. When the output through check valve 53 moves the diaphragm 61 toward the tube 57,

there is a flow across restriction 58 and this flow is added into the chamber of hou'sing 25 and helps to move the diaphragm 26 toward the tube 27 faster. The effective volume of housing 611 is normally l th to l/5th of the volume of housing 25 so that the diaphragm 26 has not finished its travel when diaphragm 61 has finished its travel, but movement of the diaphragm 26 is initially speeded up. The restriction orifree 58 prevents the input pressure from diaphragm 61 acting on diaphragm 26 from increasing too much, which would actuate the valve 34 to close.

The position of the diaphragm 61 and the diaphragm 65A is determined by time. As shown in solid lines the set point pressure signal from device 76 has been removed from line 75, a sufficient length of time so the diaphragm 61 moved to its normal position before actuation of the timer. Any pressure in set point line 75 will cause diaphragm 61 to be moved toward tube 57 and if the diaphragm 61 has not moved back to its normal solid line position before the signal from line 18 appears (the signal from line 48 appears as soon as the timer start signal appears) the diaphragm 61 will provide less air to housing 25 than it does normally.

Thus, if the diaphragm 61 has been displaced toward the end of tube 57 by pressure in the set point line 75 at the time that the pressure appears on the line 38 to trigger the timer, the time of operation for the diaphragm 26 will be a longer period of time than normal because there will be less air supplied by the movement of diaphragm 61 through housing 611 urging the diaphragm 26 to move. If the position of the diaphragm 61 is displaced toward tube 57 from its normal at rest position the time period of basic timer 25 is longer than normal.

The housing 65 and internal diaphragm 65A are used for speeding up the time period of the diaphragm 26. v

The outer surface of diaphragm 65A is open to duct pressure (P and once the set point pressure signal is removed from the line 75 (and therefore also from line 68) the check valve 67 closes, (as does the check valve 69 in housing 66) and the duct pressure acting on diaphragm 65A will tend to force or bleed any additional air in chamber 641 through the

restrictions

63, and 58 and out through restriction 311. However, if the timer is triggered by a signal in line 38 before the diaphragm 65A returns to its normal position, the diaphragm 65A adds air to the chamber in housing 25 and makes the diaphragm 26 sweep faster than normal to thus cause a faster or shorter than normal time period.

The recovery time for the diaphragm 61 to move to its normal position is determined by the restriction 71 and the pressure in line 26 because the check valve 53 will operate to close when output from chamber 37 is atmospheric pressure and diaphragm 61 moves toward normal position. The recovery time for the diaphragm 65A is determined by the orifice 63 and the pressure in line 28. The time for full recovery of the diaphragm 65A is relatively long.

Thus, where the pressure signal from line is present, the diaphragm 61 immediately moves to position with the diaphragm 61 extended toward the tube 57, and the diaphragm 65A also is extended out from normal. As soon as the pressure signal from line 75 is removed the diaphragm 61 moves toward its normal position. It reaches its normal position before the diaphragm 65A reaches its normal position. Thus initial movement of diaphragm'61 from position adjacent the end of tube 57 toward its normal position takes air away from housing 25 to make diaphragm 26 move slowly. After the diaphragm'61 reaches its normal position it adds air to housing 25' when the timer is tripped, and diaphragm 65A also adds air to housing 25 until the diaphragm 65A reaches its normal position. Additional variation in the time period of basic timer 25 can be made by other regulation of input pressures, if desired.

The variable time period thus is initially slower than normal andthe time period gradually increases to a faster than normal period as a function of time from removal of the set point signal and then returns to its normal time period. When the effect of the offsettling of

diaphragm

61 and 65A from their solid line position is no longer present.

In FIG. 4, a modified form of the invention is shown, and for means of illustration, conduits or lines leading to duct pressure are labeled P and conduits or lines leading to atmospheric pressure are labeled A.

In this form of the invention the timer is shown at its at rest or quiescence stage again, and this timer includes a main timing capacitor housing 11111 that is an annular housing defining interior chamber and having a diaphragm 1111 mounted thereacross and dividing the chamber. The diaphragm 1111 is movable from its at rest position which is shown against the end of a conduit 1112, to a position at the opposite side of the chamber as shown in dotted lines. A control valve housing 1115 is utilized in combination with the timing capacitor 1011, and has interior passageways, as shown, and a conduit 1116 leading from duct pressure is open to an internal passageway in housing 1115 that leads through a valve opening 1117 to a conduit 16% that in turn is open to the interior chamber of the timing capacitor housing 11111. In the at rest stage, it can be seen that an internal shuttle valve 169 inside the housing 1115 and a shuttle valve 1111, together forming an OR gate, are in position so that duct pressure is present in the conduit 16% through passageway 1117 in the valve housing 1115. This pressure moves the diaphragm 1111 to its solid line position. The shuttle valve 1119 is controlled by a diaphragm 1119A in a control chamber, and shuttle valve 116 is controlled by a diaphragm 1111A.

A control signal conduit 112 earring a timer start pressure signal is connected to the housing 1115 and is open to the chamber in which diaphragm 1111A is connected. Conduit 112 carries the timer start signals, and when a pressure signal comprising the timer start signal appears on line 112 the pressure acts against the diaphragm 1111A and moves the shuttle valve 1111 to position wherein the opening 1117 is closed off and duct pressure is no longer present in the conduit 1113. The

conduit 108 is then connected through the opening surrounding the shank of the shuttle valve 110 to an output conduit 113 leading to atmospheric pressure. Pressure from conduit 108 is bled through conduit 113 and from the interior of the housing 100.

The conduit 102 is connected to a source of regulated pressure coming through an output conduit 115 from a pressure regulator indicated generally at 116. The pressure in conduit 115 is restricted in its flow to the conduit 102 by an orifice 117. The operation of the pressure regulator 116 will be explained, but the pressure in conduit 115 is above atmospheric pressure and normally is controlled to be some percentage of the duct pressure. The pressure level in conduit 115 is controlled to adjust the time period of the timer.

Conduit 102 is connected to a shuttle valve housing 118 that has a shuttle valve 119 mounted therein, and a control diaphragm 120 is used for this shuttle valve. The pressure present in line 102 when the valve is in its quiescence stage with the diaphragm 101 in its solid line position acts against diaphragm 120 and moves the shuttle valve 119 upwardly to seal an opening 121 in the housing 118 connected to line or conduit 122. Conduit 122 connects to line 115 and closes the opening 121 to insure that pressure from line 115 does not pass through the conduit 122. The opening 121 opens to a chamber 123 in the housing 120 which connects to a conduit 124 that is the output signal conduit for the timer.

As soon as the pressure in conduit 108 drops as previously explained the pressure in conduit 102 will drop substantially because of the movement of diaphragm 101 toward its dotted line position, and because of the presence of the orifice 117. The pressure on diaphragm 120 therefore also drops causing the shuttle valve 119 to move to its opposite position. It should be noted that the opposite side of the diaphragm 120 from conduit 102 is also connected to atmosphere as shown. This then moves the shuttle valve 119 away from the opening 121 and connects the chamber 123 with the conduit 122 thereby providing the regulated pressure from conduit 115 to the conduit 124 and providing an output pressure signal along the conduit connection 124A. This output pressure signal at 124A also acts through a branch conduit 1248 against the diaphragm 109A to move the shuttle valve 109 to position to close off conduit 106 and in effect keep the pressure on line 108 connected to atmosphere regardless of whether or not the timer start signal on line 112 continues or drops out.

Housing 105 therefore serves the OR gate function and will connect line 108 to atmosphere until the time period expires. The passageway through opening 107, and around the shank of valve 109 to the chamber above diaphragm 110A and to conduit 113 to atmosphere is shown in the drawings.

A check valve 127 is provided in a branch conduit 128 which connects to the conduit 102 and also to the regulated pressure conduit 115. Check valve 127 will move to its closed position and prevent passage of fluid through the conduit 128 to the conduit 102 so that the only air or fluid supplied for moving the diaphragm 101 to its dotted line position is through the orifice 117. Check valve 127 does provide for reverse flow from conduit 102 to line 115 when there is a pressure differential. Orifice 117 therefor controls the rate of movement of the timer diaphragm 101 by controlling the flow of air to the chamber in housing 100. The amount of flow through the orifice 117 is dependent on the pressure in line 115, and by regulating the pressure in line the speed of movement of the diaphragm 101 can be changed, thereby changing the time period.

When the timer diaphragm 101 reaches its dotted line position, it will be seen that the pressure in line 102 will then immediately rise, moving the shuttle valve 119 to its solid line position because of the pressure acting on the diaphragm 120 (it is in opposite position during the sweep of diaphragm 101), closing off the opening 121 and venting the conduit 124 to atmosphere past the shank of valve 119 and through the provided conduit in the housing 118. The lines 124A and 12413 are then returned to atmospheric pressure. Thus the timer output signal is no longer present, and the diaphragm 109A is not subjected to pressure. The duct pressure through conduit 106 then is permitted to move valve 109A to its solid line position and the duct pressure is again present in conduit 108 (assuming that the timer start signal on line 112 has ceased). The pressure in conduit 108 then immediately moves the diaphragm 101 to its solid line position. The check valve 127 in conduit 128 opens to permit diaphragm 101 to its solid line position very quickly. The rate of return depends on the ratio between regulated pressure on line 115 and duct pressure in conduit 108.

Reference is now made to regulator 116. While many different kinds of pressure regulators can be utilized, a specific form which is automatically operated is shown by way of example. The regulator 116 includes a housing divided into several different chambers and control valve assemblies. An input duct pressure conduit 136 is connected to a chamber 137 in which a control valve 138 is mounted. The control valve is formed with a shank much like the shuttle valves in the previous forms of the invention, and has a control finger 139 that extends therefrom. The control valve 138 controls flow between the duct pressure chamber 137 and a regulated pressure chamber 140. The conduit 115 which is the output conduit is connected to the chamber 140.

The finger 139 for valve 138 extends through a wall of the housing, into a chamber divided by a balancing diaphragm 142 that controls movement of the flow control valve 139. The balancing diaphragm 142 forms a chamber 143 on the upper side thereof and a chamber 144 on the lower side. The chamber 144 is at atmospheric pressure. A spring 146 is positioned between the diaphragm 142 and a large control pressure diaphragm 145. The diaphragm also is open to a lower chamber 147 in the housing 135. The pressure in the chamber 147 as well as the pressure in chamber 143 and spring 146 determine the position of the flow control valve 138 and therefore the pressure in chamber 140. It should be noted that when the spring 146 and diaphragm 145 are bottomed against the bottom wall of the chamber 147, and the pressure in chamber 143 is low the spring 146 is designed so that it will still urge the control valve 138 to where the pressure in chamber 140 will be approximately one-fourth to one-half the pressure in chamber 137. This assumes a small flow out from the chamber 140, and may be provided with a small bleed orifice 180 so that there is some small flow through the pressure regulator in order to make it function properly.

The chamber 140 is connected to the chamber 143 with orifices 150 that are selected in a manner that will be described. A conduit 151 is connected to chamber 140. Conduit 151 has a restriction orifice 152 therein, and a check valve 153 is also provided in the conduit on the opposite end of orifice 152 from chamber 140. The conduit 151 connects to a control valve housing 154. The housing 154 includes a shuttle valve 155 that controls flow from a conduit 156 which is connected to duct pressure. The shuttle valve 155 is controlled by a diaphragm 157 that in turn is subject to pressures from a line 158. The line 158 carries a set point pressure signal from a set point pressure signal source indicated at 159. When there is a set point pressure signal, the shuttle valve will be moved to close off the conduit 156, and connect the conduit 151 to atmosphere past the shank of valve 155 and through a conduit 154A open to the second chamber of the housing 154. A branch conduit 162 is connected to conduit 151 between the housing 154 and the check valve 153 and this branch conduit 162 leads to a valve housing 163. The conduit 162 is open through an orifice 164 to a chamber 165. The chamber 165 also opens to the conduit 162 through a check valve 166 so that fluid can freely flow out of the chamber 165 through the check valve 166 into the conduit 162 when the check valve opens, but flow into the chamber through check valve 166 is prevented. A diaphragm 167 separates chamber 165 from a valve member 168, and the diaphragm 167 controls movement of the valve member 166 in relation to a spring 169 that biases the valve 165 away from its solid line position. The valve 168 opens and closes an opening in the hous ing 163 leading to a conduit 170. The valve 168 controls the communication of this conduit 170 with atmospheric pressure coming from a conduit 171 through the provided chambers in the housing 163. The conduit 170 is connected through an orifice 172 to the chamber 143. The conduit 1711 does not connect to conduit 151. The valve 154 is used for changing the length of the time period of the timer in relation to a set point signal. In the case where a levitated vehicle is moving along a track, and a timer is used for controlling the thrust provided to the vehicle, the set point signal would indicate that a vehicle had passed over a particular valve a certain distance ahead of the valves controlled by this timer. If a set point pressure signal was present on 159 or had been removed within a short while previously then the timer shown in FIG. 2 would be adjusted for a time period longer than normal and this would slow down the vehicle.

Therefore, assuming that the set point signal is present, the valve 155 would closeoff duct pressure from conduit 156 and the conduit 151 would communicate with atmosphere. This would permit conduit 152 to communicate with atmosphere and the spring 169 would move the valve 168 immediately away from the opening in housing 163 by dumping air through check valve 166 to atmosphere. This also would permit a flow to atmosphere through orifice 152 from the chamber 140 and through check valve 153 out the conduit 154A of valve 154. Because the pressure in chamber 147 would also then drop to atmospheric, the diaphragm 145 would move to its fully relieved position (adjacent the far wall) and the spring 146 would exert a small pressure on the control valve 136. The pressure in the chamber 143 would be determined by the ratio between orifice 150 and orifice 172 which is then connected to atmosphere. As long as the set point signal waspresent in 159, the pressure regulator 116 would be at a minimum pressure setting so that the pressure in line would be a minimum, for example onequarter the duct pressure, and this would increase the length of the time period for movement of timer diaphragm 101 between its extreme positions so that a signal would be present on line 124A for a longer than normal length of time.

Once the set point signal 159 disappears, the valve 155 would move to its solid line position presenting duct pressure in conduit 151. This would close check valve 153, and duct pressure would flow into conduit 162 through the orifice 164.

As soon as the duct pressure is present in conduit 151, the check valve 153 closes, and the fluid from chamber will bleed through orifice 152 and a conduit 152A to the chamber 147 to raise the pressure on the control pressure diaphragm 145. At the same time, duct pressure bleeding through orifice 164 starts to move the valve 168 toward its solid line position at a rate dependent on the size of the orifice 164 and the size of the spring 169.

Fluid from chamber 140 bleeds slowly through the orifice 152 and conduit 152A into the chamber 147. The conduit 1711 continues to be connected to atmosphere for a time, depending on rate of closure of valve 165, and fluid from chamber 141) will flow out orifice 150, orifice 172 and to atmosphere while valve 168 is open. As the pressure builds up in the chamber 147 the amount of opening of the valve 138 will regulate the pressure so that the pressure in chamber 140 and in conduit 115 increases until diaphragm is seated. The pressure in conduit 115 remains fixed at higher than nominal pressure until valve 168 closes at a later time. Of course the higher the pressure in the chamber 140, and in conduit 115, the shorter the time period for the timer capacitor diaphragm 101 to sweep the volume of the capacitor 160. The timer capacitor thus starts out at a long time period upon release of the set point signal and this time period gets shorter down to a limit upon the passage of time until the valve 168 closes returning the time period to nominal.

The time required for the valve 168 to close, after removal of the set point pressure signal is released to permit valve to open conduit 151 to duct pressure, can be varied by regulating the sizes of orifice 164 and spring 169. When the valve 168 closes, the conduit is closed and no longer opens to atmosphere. The pressure in chamber 143 will build up because of the overspeed control orifices 1511. As the pressure in chamber 153 builds up, the regulator valve 135 will then move until it reaches an equilibrium point. The pressure in chamber 146 will be reduced from its maximum value until an equilibrium is established for the valve 136. The normal time period is when the pressure in conduit 115 is at the equilibrium pressure.

Thus the time period for this timer can be changed from a maximum length time period, which is the time period in force when the set point signal 159 is on, and when the pressure in chamber 140 is at a minimum, to a minimum time period which is just at the time after diaphragm 145 is at maximum upward travel and before the valve 166 closes the conduit 1711. The pressure regulator reestablishes itself at a midpoint pressure which represents the pressure for a normal period of timer capacitor 100.

The orifices used for control may be constructed to overcome the normal temperature dependance of the orifices. In FIG. an orifice construction which is not temperature dependent is shown. The orifice works on the difference in temperature coefficient of aluminum and plexiglass.

FIG. 5 shows a typical block in which orifices are mounted, for example, the critical time period orifices 29, and 117. The block 176 has an internal chamber and a line opening 177 open thereto. A chamber 178 is also provided and is connected to a conduit in which the orifice is located.

The orifice assembly includes an outer mount or tube 179 that is made of aluminum. The end wall 179A has openings 179B therethrough for fluid passage and an adjustment screw 180 is threadably mounted in this end wall.

The open end of the tube 179 is used to mount an internal sleeve 181 made of plexiglass or some other material that has a temperature coefficient of expansion different from the material of the tube 179. The outer edge of the inner tube is fluidly sealed to the inner surface of the outer tube. The inner end of sleeve 181 mounts an orifice plate 182 that has a central orifice opening 183 that is aligned with the tapered point on adjusting screw 180. The plate 182 can be made of brass for example. Fluid passing through the orifice assembly between openings 177 and 178 must pass through the small opening 183.

The variable orifice, which compensates for normal temperature dependency of orifices in fluids, operates so that the effective area changes with temperature. As the orifice assembly heats up, the

tubes

179 and 181 expand at different rates and the plate 182 is moved over the conical point screw 180. The point tends to decrease the area of the opening so the orifice area decreased with temperature increase, the rate of change can be set by the angle or shape of the conical point. The point in the present application is on the screw for adjustment to obtain the desired time period, although a fixed point also can be used.

Thus two ways of regulating the time period of a pneumatic timer have been shown, and this feature can be used for varying the time period between two extremes as desired.

What is claimed is:

l. A fluid timer device having an output means for delivering a timer output signal comprising a housing having an interior chamber, diaphragm means dividing said chamber into sections, first and second fluid pressure signal means open to said chamber on opposite sides of said diaphragm respectively, said diaphragm means being movable from a first position adjacent said first fluid pressure signal means to a second position adjacent the second fluid pressure signal means and movable between said first and second positions, said first pressure signal means normally maintaining said diaphragm means in said first position, said second fluid pressure signal means providing pressure at a lower pressure level than said first fluid pressure signal means, third means connected to said second fluid pressure signal means to provide an output signal whenever the pressure in said second fluid pressure signal means drops below a preselected level, timer start signal means operatively connected to said first pressure signal means, and means to cause reduction of the pressure of said first fluid pressure signal means in response to a timer start signal from the timer start signal means and to maintain said first pressure signal means at a pressure level lower than the pressure level of said second fluid pressure signal means until said diaphragm means moves from said first to said second position.

2. The combination as specified in claim 1 wherein the second fluid pressure signal means is open to a source of fluid under pressure, and an orifice means restricting the flow of fluid to said second fluid pressure signal means from said fluid pressure source.

3. The combination as specified in claim 1 wherein said third means comprises valve means responsive to the pressure in said second fluid pressure signal means .to control flow of fluid from a pressure souce to an output of said fluid timer whenever said diaphragm means is moving away from said first position.

4. The combination specified in claim 1 and OR gate means connected to said timer start signal means and to the output means of said timer including means to maintain said first fluid pressure signal means at a pressure that is lower than the pressure of said second fluid pressure signal means regardless of the removal of the timer start signal during time of movement of said diaphragm from said first to said second positions.

5. The combination as specified in claim 1 and means to regulate the flow of fluid to and from said chamber in response to a separate time period adjustment signal.

6. The combination specified in claim 1 and means to regulate the flow of fluid to said second fluid pressure signal means in response to a separate time period adjustment signal comprising a pressure regulator regulating the pressure of fluid supplied by said second fluid pressure signal means.

7. The combination specified in claim 1 and means to regulate the flow of fluid supplied by said second fluid pressure signal means in response to a separate time period adjustment signal comprising means to supply different quantities of fluid to said second fluid pressure signal means.

8. The combination specified in claim 7 wherein said means to supply different quantities of fluid to said second fluid pressure signal means comprises a second housing member having an outlet connected to said second fluid pressure signal means, a second diaphragm mounted in said second housing member, and means to control movement of said second diaphragm toward and away from said outlet in response to said separate signal, movement of said second diaphragm thereby adding to or subtracting from the fluid supplied by said second fluid pressure signal means.

9. A fluid pressure timerassembly comprising means defining a chamber and movable means inside said chamber movable between a first normal position and a second position and responsive to fluid pressure differentials in said chamber on opposite sides of said movable means, first and second fluid pressure signal means open to said chamber on opposite sides of said movable means in said chamber, means to normally maintain the fluid pressure at said first fluid pressure signal means greater than the fluid pressure at said second fluid pressure signal means to cause said movable means to move to said first normal position, means to reduce fluid pressure at the first fluid pressure signal means to a pressure level below said second fluid pressure signal means, and means responsive to movement of said movable means from said first to said second position to deliver a timer output signal during the time required for said movable means to move from said first to said second position while the fluid pressure at said first fluid pressure signal means is reduced.

10. The combination as specified in claim 9 and regulator means to regulate the pressure differential between said first and second fluid pressure signal means when the pressure at said first fluid pressure signal means is reduced below the pressure of said second fluid pressure signal means.

11. The combination as specified in claim 9 and means to reset said movable means to its first position.

12. The combination as specified in claim 9 and means to vary the time necessary for said movable means to move from its first to its second position comprising pressure regulator means open to said second fluid pressure signal means and means responsive to an external signal to first decrease the pressure supplied to said second fluid pressure signal means through said pressure regulator and subsequently to increase the pressure supplied to said second fluid pressure signal means by said pressure regulator on a time elapsed basis, and then to return the pressure of said second fluid pressure signal means to a normal value.

13. The combination of claim 9 including means providing a separate time period adjust signal, and means to vary the time required for said movable means to move from its first to its second position including means to adjust the fluid flow relative to said chamber in response to said time period adjust signal.

14. The combination of claim 9 and orifice means controlling fluid flow from said second pressure signal means, said orifice means comprising a temperature compensated orifice including a housing having a passageway defined therein; a mounting block in said housing having fluid passageway means therethrough, a support mounted on said mounting block and being made of a material having a different coefficient of thermal expansion than said mounting block, said support having means defining an orifice opening means therein, said orifice opening means defining the sole fluid passage through said housing, and means cooperating between said means defining said orifice opening means and said mounting block to cause alteration in the size of said orifice opening means when the mounting block and support differentially move under temperature changes.

Claims

1. A fluid timer device having an output means for delivering a timer output signal comprising a housing having an interior chamber, diaphragm means dividing said chamber into sections, first and second fluid pressure signal means open to said chamber on opposite sides of said diaphragm respectively, said diaphragm means being movable from a first position adjacent said first fluid pressure signal means to a second position adjacent the second fluid pressure signal means and movable between said first and second positions, said first pressure signal means normally maintaining said diaphragm means in said first position, said second fluid pressure signal means providing pressure at a lower pressure level than said first fluid pressure signal means, third means connected to said second fluid pressure signal means to provide an output signal whenever the pressure in said second fluid pressure signal means drops below a preselected level, timer start signal means operatively connected to said first pressure signal means, and means to cause reduction of the pressure of said first fluid pressure signal means in response to a timer start signal from the timer start signal means and to maintain said first pressure signal means at a pressure level lower than the pressure level of said second fluid pressure signal means until said diaphragm means moves from said first to said second position.

3. The combination as specified in claim 1 wherein said third means comprises valve means responsive to the pressure in said second fluid pressure signal means to control flow of fluid from a pressure souce to an output of said fluid timer whenever said diaphragm means is moving away from said first position.

9. A fluid pressure timer assembly comprising means defining a chamber and movable means inside said chamber movable between a first normal position and a second position and responsive to fluid pressure differentials in said chamber on opposite sides of said movable means, first and second fluid pressure signal means open to said chamber on opposite sides of said movable means in said chamber, means to normally maintain the fluid pressure at said first fluid pressure signal means greater than the fluid pressure at said second fluid pressure signal means to cause said movable means to move to said first normal position, means to reduce fluid pressure at the first fluid pressure signal means to a pressure level below said second fluid pressure signal means, and means responsive to movement of said movable means from said first to said second position to deliver a timer output signal during the time required for said movable means to move from said first to said second position while the fluid pressure at said first fluid pressure signal means is reduced.