Патент USA US2130458код для вставки
Patented Sept. 20, 1938 2,139,453 UNi'i‘ED 2,130,458 POWER CONTROL FOR PNEUMATIC CON VEYER- SYSTEMS Herman Busch, Long Island City, N. Y., assignor to Airmatic Systems, Inc, New York, N. Y., a corpcration of New York Application February 29, 1936, Serial No. 66,504 Renewed August 1, 1933 15 Claims. (Cl. 243-15) This invention relates to power ‘or motive ?uid controllers for pneumatic conveyer systems and more particularly to the general type of controll ers, the purpose of which is to reduce the total 5 amount of motive ?uid or power required to op erate such systems. An early prior art controller of this type is disclosed in Patent No. 968,576 granted to Libby on August 30, 1910. In the Libby type of controller a main motive l0 ?uid valve opens for aperiod during which trans mission is accomplished and closes at the end of the period, remaining closed until transmission is again desired. During this period of no trans mission a so called minimum flow of ?uid is 15 maintained in the transmission line by means such as a by-pass around the main valve. For accomplishing the opening of the valve at the be ginning of a transmission period, pneumatic means, designed to respond to pressure changes ‘30 in the transmission line, opens a port to admit operating fluid to a motor which in turn opens the main ,valve. When the main valve reaches full open position, the pressure responding means is rendered inoperative whereupon the main valve termined by leakage of the operating ?uid from the motor. As the main valve reaches‘ closed position, the response means is reconditioned or 30 ' Heretofore the construction of a control mech anism in which the sequence of operation just described would be carried out with just the right interval and overlap to assure stable perform ance of the valve over long periods has been 35 fraught with great dif?culties. A particularly dif ?cult sequence to carry out in the operation of this mechanism has been to close the main valve and restore the response mechanism without the latter responding to the transmission line pres 40 sure existing just prior to the complete closure of this valve, causing it to be reopened before complete closure. The primary object of this invention is to pro vide a power control apparatus which will carry 0 out sequences of operation required in the Libby type of valve with certainty and over long periods of operation without readjustment. Another object is to provide a means of restor 50 ing the pressure response control valve to re sponding condition in a manner such that it will - not respond to reopen the main valve before it has completely closed. Another object is to produce a control valve 55 in which a very low minimum flow may be em~ Another object is to produce a control device employing a very low minimum ?ow and yet which is very sensitive to-the insertion of articles 6. to be conveyed which do not completely ?ll the conveyer line such as loosely ?tting or badly worn carriers in a carrier system. Still another object is to provide a control valve with means for quickly closing the same at the 10 end of its stroke. A further object is to provide a control valve with means for increasing its speed of travel dur ing the latter part of its closing stroke. A further'object is to produce a control valve 15 which will operate as e?ectively and economical ly on long lines as so called “carrier closed” valves, that is, closed by means responding to pressure variations incident upon carrier discharge. A still further object is the construction of a 20 control mechanism of the type to which this'in vention relates ~in which the various operating parts are so located on the structure as to ‘func tion in the best manner and at the same time pro vide a structure which is simple, having few parts, 25 25 closes by movement over a time interval de restored for the next transmission cycle. ployed so that the power saving will be increased to a maximum. and presenting a pleasing appearance. These and other objects will be apparent from the following description taken in connection with the accompanying drawings in which: Fig. 1 is diagrammatic view of a single conveyer‘ 30 line showing where the control mechanism is usu ally placed therein; Fig. 2 ' is a sectional view showing the parts when the main valve is in closed position; Fig. 3 is a sectional view showing the parts in 35 the position they assume when the main valve is in full open position; and, - Fig. 4 is a fragmentary View showing a modi ?ed form. . _ While the use of this invention is not necessarily restricted to conveyer systemsof the pneumatic carrier type employing a tube through which car riers are transmitted by the ?ow of an air cur rent through the line either under pressure or vacuum, this invention will be described for illustrative purposes as applied to the vacuum type of pneumatic carrier systems. Referring now to Fig. 1 of the drawings, that portion of a pneumatic carrier system pertaining to a single conveyer line is diagrammatically illustrated. From a central station desk ill dispatch lines extend out to various substations. A single line employing a control device comprises a send ing tube H having a dispatch terminal l2 and a return tube l3 provided with the usual delivery ‘10 45 50 ‘55 2 2,130,458 terminal l4. From the latter terminal an ex tension tube l5 passes down through the central desk l6 and connects with the power control de vice |6 at what will hereinafter be referred to as the transmission line side of the device. From the suction line side of the device |6 a suction tube |'| connects with the usual suction or header H3 in which a vacuum is continuously maintained by means of a suitable exhauster, not shown. In 10 other words, the exhauster is the common power source and the device |‘6 controls the power ex pended in a single line. A continuous air pas sage or conduit is formed by the parts enumerated from the dispatch terminal I2 through the dis 15 patch and return tubes II and I3 and the con troller I6 to the exhauster. Referring to Figs. 2 and 3, the controller I6 comprises a casing 2| divided by a septum 22 into two chambers, 23 and 24. Chamber 23 is in com munication with the transmission line and cham ber 24 is in communication with the suction header. The septum 22 is provided with two ports, a large port 25 which is controlled by a main valve 26 and a small port 21 which is con trolled by an auxiliary valve 28. The auxiliary valve is opened by a screw threaded stem 29 and is set normally off its seat to provide a small air passage through which is maintained acontinu ous stream of air ?owing from the transmission 30 line. This continuous ?ow of air will be herein after referred to as the “minimumflow”. A motor 30 having a housing 3| is provided at the side of casing 2| for operating the main valve 26. This motor is comprised of diaphragm 35 32 connected to the main valve by means of a stem 33 which the motor reciprocates through a bearing 34 in the inner wall of the motor hous ing. The housing 3| comprises a saucer shaped base section 35 and a similar shaped cap 36 at 40 tached to the base with the rim of the diaphragm 32 held between these two elements. The diaphragm divides the housing into inner and outer chambers 31 and 38. The inner cham ber 31 communicates freely with the suction or 45 low pressure chamber 24 through a relatively large unrestricted opening 39. The chamber 38 communicates with chamber '31 through restrict ed ports 4| and 42. The size of the opening of port 4| is regulated by needle valve 43. This port 50 constitutes a continuous leakage connection be tween chambers 31 and 38 by means of which the closing time of the main valve is determined as will hereinafter appear. The auxiliary port 42 and a connecting passage 55 44 provides a supplementary leakage connection between these two chambers. The passage 44 ex tends inwardly of the stem 33 from the outer end through the. diaphragm 32. This passage is formed at its outer end to admit a plug 45 which 60 carries a reciprocating valve 46. Several air pas sage ways 41 extend through the plug to permit the passage 44 to communicate with the chamber 38 when the valve 46 is open but which are closed by the valve when it is seated upon the inner face of the plug. A spring 48 urges the valve toward seated position. The valve is opened when its the outer end of the stem have been omitted. The port 42 is opened and closed by becoming covered and uncovered as it moves back and forth through bearing sleeve 34. The port 42 is positioned along passage 44 at a point such that during the closing stroke of the valve it will pass out at the right end of the bearing sleeve 34 at the point in the stroke where it is desired that increase in closing speed is to begin. This point may be varied by adjusting the sleeve 34 10 longitudinally in its supporting boss in wall 35. As already indicated the stem 33 extends through the main valve 26. At its outer end the stem is carried in the central opening of a boss member 52 disposed at what is the rear of the structure viewed as it is ordinarily installed in service. This boss, as will presently be described, forms the base or seat element of a pilot valve which is employed to condition the mechanism for proper sequence of operation. The inner face 20 of boss 52 carries a recess in which is seated the outer end of compression spring 53. The inner end of the spring is secured to stem 33 and ex er'ts a force su?icient to hold valve 26 normally on its seat. ed according to this invention for experimental use the shoulder moves out a distance of about 1/8 of an inch or less. At the outer face of plate 55 is secured a disc 51 which surrounds the re duced portion of the stem. In the normal posi 40 tion of plate 55 this disc is positioned at the outer end of sleeve 54. When the stem moves outward ly, the disc is engaged by shoulder 56 moving plate 55 out a distance corresponding to the protrusion of the'shoulder portion 56. The outer 45 end of the stem extends beyond disc 51 and car ries an adjustable collar 58. This collar is set so that when the main valve 26 is moved to its seat, the plate 55 is brought against the face of the boss 52. It will be noted that shoulder 56 and collar 58 form a lost motion connection between the stern and plate 55. A spring pressed plunger 56 set in one side of plate 55 bears upon sleeve 54 to form a friction bearing for the plate to pre vent accidental movement thereof when in its 55 outer position as shown in Fig. 3. The valve opening movement of motor 36 is determined by a control valve 6| disposed to nor mally close a passage 62 leading from atmos phere (see Fig. 1) through valve seat 63 to cham 60 ber 38. However, it might be spring loaded to vary gravity action or it might be so positioned that gravity does not act upon the valve at all. The valve is lifted by auxiliary motor 64. This motor comprises a casing which is divided into 65 two chambers 65 and 66 by means of a small stem 49 engages the inner face of the adjusting diaphragm 6?, the latter being connected through screw 5|. Although the supplementary leakage a suitable operating stem to valve 6|. The lower chamber 66 is continuously open to means is shown in stem 33 it could as well be lo cated elsewhere and the valve 46 operated in ac cordance with the movements of the motor dia phragm in some other ‘manner. .~ 7 In Fig. 4 a modi?ed form of the supplementary leakage connection between chambers 31 and 38 is shown. In this form the valve and plug at 25 The central opening of boss 52 forms a bearing for the outer end of stem 33 which extends through a sleeve 54 formed at the outer facing of the boss. A plate 55 is mounted to recipro cate upon this sleeve. The outer end of the stem 30 33 is turned down to a smaller diameter to form shoulder 56 thereupon. When the stem moves to its extreme left position, the shoulder 56 moves outwardly beyond the end of sleeve 54 a short distance as shown in Fig. 3. In valves construct 35 the atmosphere through ports 68. The upper 70 chamber 65 has two passages ‘H and 12 leading therefrom. The passage 1| connects through tube 13 with chamber 23 on the transmission line side of the valve, communicating the pressure in chamber 23 to chamber 65. Adjustable restric 75 3 2,130,458 tion of this passage is provided by means of screw 14. The other passage 12 is connected by means of a tube 15, which may be a ?exible hose such as rubber, and nipple T6 to a recess TI provided in boss 52. This recess has an atmospheric port which is preferably faced with a soft resilient ring 18 which may be live rubber or the like. The ring is preferably of su?icient thickness to valve 6| closed cutting off the atmospheric pres be slightly compressed when plate 55 is brought in the present case, the speed of the entire closing stroke is slowed down by the employment of timed 10 closing. When the pilot valve is moved by the 10 into engagement with the face of the boss. Plate 55 acting as the valve and ring 18 acting as the valve seat on the atmospheric port form the pilot valve for opening and closing passage 12 in ac cordance with the position given to plate 55 by the movement of'valve stem 33 as already de scribed. The pilot valve will be designated gen erally as 19. It is here to be noted that with the relatively large passage and valve opening, a very small movement of the valve face plate 55 is re 20 quired to give full opening to the passage. It may be even less than 1A; inch, already given as the distance employed in experimental controllers. Having described the construction of a con troller embodying the invention, it is believed that 25 a better understanding will be had of how this invention not only makes such a simple construc tion and operation thoroughly practical but also highly desirable by now examining the di?iculties sure to the main motor. Furthermore it is to be noted that the full open position is not a critical one and whether it is completely attained will not affect the functioning of the valve. on the other hand, as already pointed out the primary di?iculties in prior controllers accom pany the closing stroke, particularly where, as main valve means, as it approaches the end of its closing stroke, the main valve is still partly open and even though the carrier has been dis charged, su?icient air is passing through the main valve to keep the pressure at the trans mission side of the valve considerably below the minimum flow pressure. It should be noted that, even though in a decreasing amount, this low or sub-minimum-flow pressure continues until the main valve is-closed. And also that the increas ing restriction upon the passage of atmospheric air through the pilot takes place reaching com plete cut-oif as the pilot valve closes. However, in these closure movements, as soon as the 25 amount of air entering chamber 55 through pas sage 72 becomes less than that withdrawn through passage ll, the pressure in chamber 65 tends in substantially all arrangements where a por tion of the main valve movement is employed to to fall to the sub-minimmn-?ow obtaining on the transmission side of the main valve. Since 30 the restriction of flow through the pilot valve varies between full flow and zero flow, and since provide the movement of the pilot valve, these dif?culties may be amply illustrated by pointing the point at which the flow through pilot valve becomes less than that leaving the auxiliary motor heretofore encountered. While the dimculties of 30 simple direct operation of the parts are inherent 35 them out with relation to the type of valve chosen as the embodiment of this invention. This means, of course, that for this purpose the auxili ary leak port 42 with its associated closing ap paratus and the special form of the pilot valve are to be considered as absent from the structure. The operating difficulties grow primarily out of the inherent characteristics of the main valve of the prior art controllers to slow down in its travel as it approaches closed position. This is particu 45 larly true of the double chamber positive action type of motor where the chambers are separated by the movable operating wall or diaphragm and both chambers are normally under reduced pres sure or vacuum and the forward stroke of the 50 motor takes place upon the controlled admission of atmosphere or high pressure operating ?uid to one chamber and the return stroke controlled in accordance with the resumption of equal pres sures in both chambers accomplished by means of 55 a controlled leak p-ort between the two chambers. The falling off of the closing speed at the end of the stroke is due to the decreased ?ow capacity of the leak port as the pressures on the opposite sides of the port approach the point of equaliza 60 tion. This follows the well known laws of ori?ce ?ow. On the other hand, it should be pointed out that the main valve is opened by admitting sub stantially full pressure atmospheric air for the 65 entire opening stroke. Consequently, the main valve is opened with a relatively quick movement. Yet, even though the pilot valve when opened directly must begin to admit atmospheric air to the operating chamber 65 of auxiliary motor 64 70 before the end of the stroke is reached, the time required to ?ll chamber 65 with the differential remainder of air from that admitted over that withdrawn through passage "H is quite suf?cient to permit the main valve to reach full open posi 75 tion before the auxiliary motor drops the control chamber 55 is at some intermediate point of the 35 pilot valve closing, therefore this point will be reached before. the valve is entirely closed; that is while it is still open and while the trans~ mission side is still at sub-minimum-fiow pres sure. The auxiliary valve does not open, how 40 ever, simultaneously with the reaching of this point. On account of the reservoir effect of op erating chamber of the auxiliary valve motor a moment is required for this “sub” pressure to accumulate. Now if the response of the auxiliary 45 or control motor is made sensitive, as it must be if the amount of minimum ?ow is to be kept low so that a real saving is made by the use of power controllers, the control valve 6! will be opened up by the “sub” pressure before the main 50 valve is completely closed, causing it to repeat edly open and never come to rest at closed posi tion. ‘ It is to be noted that the relation of the ?ow ' capacity of evacuating passage ‘H and ?lling pas 55 sage l'Z can be modi?ed by an adjustable restric tion means such as screw ‘it to change the point at which the “sub” pressure is transferred to the chamber of the auxiliary motor.‘ However, for the opening portion of the main valve cycle it is 60 desirable to have the evacuating passage ‘ll rela tively wide open so that the diiferential build-up of atmospheric pressure takes place slowly in or der to permit the main valve to open wide be fore the control valve closes. On the other hand, 65 for the closing portion of the main valve cycle it is desirable that the evacuating passage it be considerably restricted in order to delay the build-up of the transmission iine pressure. It will be seen therefore that the adjustments favor 70 ing‘ the two portions of the main valve cycle are in the opposite direction. It is primarily because of these difficulties that a large number of the designs employed for mini mum ?ow power controllers have proven di?i 75 4 2,130,458 been accomplished primarily by the provision sion line begins to be reduced and, as the valve opens, is rapidly reduced by an amount su?i cient to draw the carrier through the transmis sion line. The reduced pressure in the transmission line, due to the opening wide of valve 26, draws air of the supplementary leak port 42 opened as the valve approaches the end of its closing stroke through passage 'H from the chamber 65 and would become established to hold the valve 6| cult of adjustment and maintenance and have become inefficient and obsolete from the stand point of practical operation. These di?iculties have been overcome by valves constructed according to this invention. It has thereby overcoming the tendency of the valve 10 to slow down and instead speeding up the travel during this part of the stroke. By this means the passages controlling the auxiliary motor may be set for a median of adjustment, and no di?'i culties be encountered with a sensitively bal 15 anced control valve and motor. When fast clos ing of the main valve is provided, it has been found that the flow capacity of these passages may be adjusted to favor either the opening or closing stroke and still employ a sensitive con 20 trol valve with ample margin of stability. The operation of the controller constructed according to this invention including the auxil iary leak port, also the simple form of pilot valve, and its placement will now be set forth. When the system is in operation, chambers 24, 31, and 38 are all subjected to the vacuum pressure in the suction header l8. This is due to the fact that when no air is entering chamber 38, ‘an equalization of pressures in chambers 37 and 38 30 is maintained through the port 4! and these chambers are in communication with the suction side of the valve through the large opening 39. Under normal conditions the valve parts take the position shown in Fig. 2. The minimum. ?ow of air through the transmission line takes place through the by-pass port 21 and is regulated by valve 28. As already stated the control Valve SI and its operating motor '64 are so designed and balanced 40 as to be very sensitive or, in other words, respon sive to a relatively small vacuum. For the usual conditions it may be designed to respond to a vacuum of 3 to 31/2 inches of water. The mini mum ?ow may then be regulated to a vacuum 45 of from 1 to 2% inches of Water according to the type of line. At such minimum flow pres sures it is obvious that the volumetric flow of air is small and that a real saving in power is ac complished. Although the minimum ?ow pres sure is low and the margin of sensitivity of the control valve small, the control has proven to be very stable when adapted to widely varying con ditions and has continued to function as set over considerable periods of time without readjust 55 ment. The proper adjustments having been made ac cording to line conditions, as soon as the head of a carrier enters the mouth of a terminal, it blocks the entrance of air to the line. There 60 upon the air ahead of the carrier is exhausted through minimum flow opening 21 reducing the pressure in the transmission line and in cham bers 23 and 55. As soon as a small pressure re duction occurs in chamber 65, diaphragm 61 acts 65 to lift the valve SI from its seat admitting a rush of atmospheric air through the passage 62 into chamber 33. The rate of entrance of air through this passage exceeds by a considerable amount the rate of air leakage through both the leak 70 ports 4! ‘and 42. As the air ?lls chamber 38, diaphragm 32 and attached stem 33 are forced quickly to the left, moving main valve 26 to full open position and pilot valve plate 55 to the po sition shown in Fig. 3. As soon as the main 75 valve cracks open, the pressure in the transmis continuously open but for provisions to admit air to the chamber through passage 12. How 10 ever, to provide the timed closing of the main valve, control valve 6| must be closed to cut off atmospheric airto chamber 38 after the main valve has opened. This is accomplished by the. opening of passage '52 by means of the pilot valve 15 :9 provided at the rear of the valve casing. The pilot valve is opened as the main valve approaches open position. The valve stem 33 near the end of its stroke moves the disc 55 slightly to the left uncovering the port in the bushing ring 18, there 20 by admitting a ?ow of atmospheric air through the pilot valve to chamber 65. It is to be noted that due to lost motion connection between stem 33 and plate 55 the latter is not moved until the very last portion of the opening stroke of the 25 main valve. By providing a restriction in passage ‘it through the medium of screw 14, air entering chamber 65 will not be exhausted through the passage into the valve casing as rapidly as it en ters through passage 12. This differential of ?ow causes pressure in chamber 65 to rise within a short lapse of time to substantially atmospheric and since the pressure below the diaphragm is also atmospheric, the valve 6| will quickly close, due to gravity. During the above lapse of time, 85 however, the main valve continues to move to ward full open position. However, when the valve ‘6| has dropped upon its seat, and the ad mission of atmospheric air to chamber 38 has terminated, the opening movement of the main valve 26 ceases. It is preferable to so time the operation of the various elements that the main valve ceases its opening movement before it comes against any limiting stop member, thus giving the effect of cushioned opening. The atmospheric passage to motor chamber 38 having been closed, the pressures in chambers 31 and 38 begin to equalize and at a rate determined by the setting of needle valve 43 controlling port M. As the pressure in chamber 38 drops, spring 53 acts to close the main valve by moving the stem 33 and parts having connection therewith toward their normal or closed position. To offset the tendency of the travel of the main valve to slow down during the latter part of the stroke the auxiliary leak port 42 is opened up near the end of the stroke. The port is opened by the stem 189 of the leak valve (is striking the inner end of screw 5! or by the uncovering of the port in the modi?ed form. The point in the travel of the main valve 26 and the motor diaphragm 32 at which the auxiliary port is opened is determined by the length of the stem 49. This point may be varied by the interchange of valves of various stem lengths. The same effect may be accom plished by setting the screw 5i (shown in Fig. 3) 40 45 50 55 60 65 in or out. Any desired characteristic of closure of the main valve may be had by varying the size and how capacity of the auxiliary leak port and inter 70 connected passage and by determining the point in the closing stroke at which the port will be opened up. These may be chosen as just su?i cient to overcome the tendency of the valve to slow down at the end-of the stroke so that the 75 5. 2,130,458 speed of the closing travel' will be substantially period as if there were no intermediate valve the same for the entire stroke or they may be chosen so as to speed up the travel at the end of the stroke. In order that the controller may be in readiness at the end of a transmission cycle for a succeed closure. While at the same time the cuttingo? of the air ?ow shortly after carrier delivery is assured. art di?iculties, the point at which the‘ pressure been placed in front or on top, very vulnerable ' It is to be observed that a controller has been provided with assured operation under all con ing cycle the auxiliary valve 6! and its motor 64 ditions and having a wide latitude of application must be restored to its normal condition of sen~ and yet which is simple in structure and marked sitiveness to a drop of pressure in the transmis“ 1 by an absence of a large number of interlocking and coacting parts. Further, due to the sim 10 sion line below minimum flow pressure. This .is accomplished by the main valve during the latter piicity of its operation, it has been possible to part of its stroke acting to close the pilot valve. shift the pilot valve and its operating parts to the As already explained in the examination of prior rear of the casing, whereas heretofore they have 15 in the operating chamber 65 of auxiliary motor M begins to assume the pressure in chamber 23 is when the air entering chamber 65 through pas positions for accidental damage to the parts. 15 This arrangement also gives a more pleasing ap pearance to the eye. ' sage ‘F2 is restricted by the pilot valve to an amount less than that leaving through passage 20 ‘H. It was also pointed out that the point at It is to be understood that the form of the structure shown is merely illustrative and that while the invention has been shown in but two 20 forms, it will be apparent to those skilled in the art that it may be embodied in many other forms and modi?cations without departing from the tion with a large aperture seat 78 and large faced 25 valve moving normal to the seat, the restricture of the ?ow therethrough takes place with a very small movement of the valve. This would take place in about one-half or less of the travel given the valve as shown in Fig. 3. With a pilot valve having the above character 30 istics combined with the feature of increased speed of travel of the main valve at the end of the ‘stroke, no dii?culty is experienced with. the aux iliary motor building up to its condition of sensi 35 tivity to pressures on the transmission side of the main valve before the latter has completely closed spirit thereof and it is desired, therefore, that only such limitations shall be placed thereon as are imposed by the prior art or by the appended which this begins is reached before completed closure of the pilot valve. However, when the pilot valve is constructed according to this inven and the transmission line pressure has come up to the normal minimum ?ow pressure. In this manner complete closure of the main valve is 40 assured at the end of each cycle and repeated opening or “pumping” of the valve will not occur when there is no carrier in the transmission line. The result of the fast closure of the main valve is that a simple form of pilot valve may be em 45 ployed and may be operated directly from the stem of the main valve and yet stable and certain operation be assured and maintained over long periods of time. Fast closing of the main valve enables the tim 50 ing function to be restricted to the ?rst portion of the stroke or the portion in which the valve has little or no restrictive effect on the flow of transmission line motive ?uid. 0n the other hand, the restrictive portion of the stroke is 55 traversed relatively quickly. This is advantageous in cases where the carrier is heavily loaded or worn or, for some other reason does not traverse the transmission line in the normal period re quiring two or more time cycles to complete the 60 transmission. In such a case the shortness of the restrictive travel time of the main valve causes only a slight hesitation of the carrier instead of a substantially complete stoppage with its attenci~ ant delay. These features of the power control give it op erating characteristics equalling the so called “carrier closed” valves. It is well recognized that for short lines time control is adequate, the in frequent unusual condition being taken care of 70 by a reopening of the valve. On the other hand, for long lines the valve may be set for two or more time cycles for the required travel period of the average carrier and the carrier will travel with substantially undiminished speed and be 75 delivered in within substantially the same time 25 claims. What I claim is: . 1. Power control apparatus of the minimum ?ow type for a pneumatic conveyer line having 30 a transmission line tube and an exhaust line tube and a main valve between said tubes for con trolling carrier propelling'airv?ow through the line, means for establishing a minimum ?ow of air through the line when the main valve is closed, means for opening the main valve in response to ’ the presence of a carrier in the transmission line, and time controlled means for closing the valve, said response means including a pneumatic with a diaphragm constantly exposed on one side to 5.1.0 atmospheric pressure and means for sensitizing it to the presence of a carrier in the transmission line by normally exposing its other side to trans mission line pressure, and means for desensitiz ing said diaphragm after a response including 45 means for establishing atmospheric pressure on ' said other side of the diaphragm at the opening stroke of the main valve and ing the said pressure until the end of closing stroke of said valve. 2. Power control apparatus of the end of the maintain the timed minimum ?ow type for a pneumatic conveyer line having a transmission line tube and an exhaust line tube 50 and a main valve between said tubes for con trolling carrier propelling air flow through the 55 line, means for establishing a minimum ?ow of air through the line when the main valve is closed, means for opening the main valve in response to the presence of a carrier in the trans mission line, and means for closing the valve 60 after a period of time has elapsed, said response means including a pneumatic with a diaphragm continuously exposed on one side to aconstant pressure, means for sensitizing it to the presence f a carrier in the transmission line by normally exposing its other side to transmission line pres- ' sure, and means for desensitizing said diaphragm after a response including means for establishing a pressure equal to said constant pressure on the other side of the diaphragm at the end of the .70 opening stroke of the main valve and maintain ing said pressure until the end of the timed clos ing stroke of said valve. 3. Power control apparatus for pneumatic con veyer lines of the vacuum minimum ?ow type 7.5 6 2,130,458 having a transmission line tube and an exhaust line tube and a main valve between said tubes for controlling carrier propelling air ?ow through the line, means for establishing a minimum ?ow of air through the line when the main valve is closed, a main pneumatic for opening the main valve, an auxiliary pneumatic embodying a con trol valve for initiating the opening and closing action of the main pneumatic and a diaphragm for operating the control valve, said diaphragm and valve being biased toward the normal posi tion of the valve, one side of said diaphragm being constantly exposed to atmospheric pres sure, means for normally exposing the other side to transmission line pressure, said control valve being arranged so that a pressure drop due to the presence of a carrier in said line operates the control valve to cause said main valve to open, and means operated by movement of said main 20 valve for establishing atmospheric pressure on said other side of the diaphragm at the end of the opening stroke of the main valve for equaliz ing the pressures on opposite sides of said dia phragm so that said bias means will restore the 25 control valve to normal position and cause the main valve to close. 4. Power control apparatus of the minimum ‘ ?ow type for a pneumatic conveyer line having a transmission line tube and an exhaust line tube 30 and a main valve between said tubes for con trolling carrier propelling air ?ow through the line, means for establishing a minimum flow of air through the line when the main valve is closed, a main pneumatic for opening the main 35 valve and including means for timing the closing of the valve, an auxiliary valve for controlling the operating ?uid ?ow to the main pneumatic, an auxiliary pneumatic comprising two chambers separated by a diaphragm movable to operate 40 said auxiliary valve, one of said chambers being constantly open to the atmosphere, ?rst and sec ond passages leading to the other chamber, the ?rst passage being in constant communication with the transmission line, the second passage 45 being normally closed, and means for opening the second to atmosphere at the end of the open ing stroke of the main valve and for closing the same at the end of its closing stroke. 5. Power control apparatus of the minimum ?ow type for a pneumatic conveyer line having a 50 transmission line tube and an exhaust line tube and a main valve between said tubes for control ling carrier propelling, air?ow through the line, means for establishing a minimum flow. of air 55 through the line when the main valve is closed, a main pneumatic for opening the main valve and including means for timing the closing of the valve, an auxiliary valve for controlling the oper ating ?uid flow to the main pneumatic, an aux 60 iliary pneumatic comprising two chambers sep arated by a diaphragm movable to operate said auxiliary valve, one of said chambers being con stantly open to the atmosphere, ?rst and second passages leading to the other chamber, the ?rst 65 having a determined flow area, the second hav ing a flow area larger than the ?rst, the ?rst passage being in constant communication with to hold said valve closed, a ?uid motor arranged to open the valve against the action of said resil ient means; said motor comprising a housing em bodying a motive ?uid chamber having a movable side wall and means for operatively connecting said wall and the valve, a controlled inlet port for admitting motive ?uid to said chamber for opening the valve, a continuously open regulata ble leak port for bleeding the motive ?uid out of said chamber at a determined rate for permitting the valve to close, a valve closed leak port and a rod reciprocated by the movement of the main valve for opening said port valve as the main valve approaches closed position to increase the determined leakage rate and closing the valve at 15 increased speed, and an adjustable stop for the rod for determining the point in the closing stroke of the main valve at which the pOrt valve opens. 7. In a power controlling apparatus for a pneumatic conveyer line, a pneumatic motor hav 20 ing a chamber provided with a movable wall, a stem extending from said wall to said valve for operating the latter, a normally closed control valve in said stem arranged to provide a vent to said chamber for modifying the operation of said motor, and means operative by the inward movement of said wall and stem for opening said control valve. 8. In a power control apparatus for a pneu matic conveyer line, a main valve for controlling the flow of motive ?uid in the line, means for opening and closing the main valve, an auxiliary valve for controlling the main valve, a pilot valve, opened and closed in accordance with the move ments of the main valve, for conditioning the auxiliary valve, means for increasing the speed of travel of the main Valve as it approaches the end of its closing stroke, and means operated by the main valve for causing the pilot valve to be closed in accordance with the modi?ed move ment of the main valve. 9. Power control apparatus for a pneumatic conveyer line having a main valve for controlling the line ?uid ?ow, meansfor opening and clos ing the main valve, a diaphragm normally sensi 45 tive to the pressure incident to the introduction of a carrier in the line for controlling the main valve opening means, a chamber enclosing one side of the diaphragm, means providing a pilot port in communication with said chamber for 50 controlling the sensitivity of said diaphragm, means operated in accordance with the opening movement of the main valve at the end of its opening stroke for opening said port and desensi tizing said control diaphragm, and means acting 55 at the end of the main valve closing stroke in cluding the portion in which the pilot port is closed to import a relatively quick movement to the main valve while the pilot port valve is being closed. ’ 60 10. In a power control apparatus for a pneu matic conveyer line, a control valve disposed to travel between extreme open and closed positions for releasing and restraining the flow of motive fluid in the conveyer line, said valve being ar 65 ranged so that in a ?rst portion of its travel, which lies between an intermediate position and said open position, substantially no restraining e?ect of the fluid ?ow occurs, while in a second portion’ of its travel, which lies between said 70 the transmission line, the second passage being normally closed, and means for opening the sec 70 ond to atmosphere at the end of the opening stroke of the main valve and for closing the same at the end of its closing stroke. 6. In combination, a valve for controlling the flow of motive ?uid through a pneumatic con a motor having a motive ?uid chamber including a wall movable between extreme positions by mo 75 veyer line or the like. a resilient means tending tive ?uid, means for coupling the wall and the 75 intermediate position and said closed position, substantially all of the restraining e?ect occurs, 7 2,130,458 valve for moving the valve through its travel, said chamber being provided with regulated ports for the escape of the motive ?uid for timing the closing of the valve, one of said ports being open a regulated amount throughout the closing stroke of the valve, an auxiliary valve for opening and closing another of said ports for speeding up the closing travel of the main valve, means for open ing said auxiliary valve during the latter part of 10 the closing stroke of said main valve, said valve opening means being adjustable so that the open~ ing of the auxiliary may be regulated to include said second portion of its closing travel. 13. In a power control for a pneumatic con veyer line having a housing, a main pneumatic, a reciprocating stem extending therefrom and protruding through one side of the housing, a , sleeve extending from said housing parallel with the protruding portion of the stem, a disk pilot valve surrounding the sleeve, lost motion‘con a valve casing being interposed therebetween, a nections between the stem and the pilot valve for giving a limited movement to the valve along the sleeve, a pilot port eccentric of said sleeve and 10 arranged to be covered by the face of said disk at one extreme position of the valve; and means for providing frictional engagement between the pilot valve and the sleeve for restricting the movement of the valve to that‘ imparted to it through said lost motion connections. motor for operating the valve and a controller therefor carried by the casing, a pilot valve for 14. In a power control apparatus for a pneu matic conveyer line, a motive ?uid power source, conditioning the controller, said pilot valve being a valve casing being interposed therebetween, a motor for operating the valve and a controller 20 therefor carried by the casing, a pilot valve for 11. In a power control apparatus for a pneu 15 matic conveyer line, a motive ?uid power source, embodied in a boss disposed at the rear of the casing and carrying a rearwardly extending sleeve, said boss having a port formed in its outer face and arranged to provide the seat portion of the pilot valve, a disc ?tted to reciprocate upon 25 said sleeve, the inner face of said disc being ar ranged to form the pilot valve face and acting when brought against the outer face of the boss to close said port by seating upon'the rim of the same, and a lost motion connection between said conditioning the controller, said pilot valve being embodied in a boss disposed at the rear of said casing and carrying a rearwardly extending sleeve, said boss having a port formed in its outer face, said port having a rim of resilient material and arranged to provide the seat portion of the pilot valve, a disc ?tted to reciprocate upon said ~ sleeve, the inner face of said disc being arranged 1 30 disc and said motor for operating the pilot valve. 12. In a power control apparatus for a pneu to form the pilot valve face and acting when 30 brought against the outer face of the boss to close matic conveyer line, a motive ?uid power source, a valve casing being interposed therebetween, a motor for operating the valve and a controller 35 therefor carried by the casing, a pilot valve for said port by seating upon and slightly compres-v sing the material forming the rim of the same, conditioning the controller, said pilot valve be and a lost motion connection between said disc and said motor for operating the‘ pilot valve. ing embodied in a boss disposed at the rear of veyer line having a housing, a, main pneumatic, said casing and carrying a rearwardly extending sleeve, said boss having a port formed in its outer 40 face and arranged to provide the seat portion of the pilot valve, a disc being arranged to form the pilot valve face and acting when brought against the outer face of the boss to close said port by a'reciprocating stem extending therefrom and seating upon the rim of the same, a lost motion connection between said disc and said motor for operating the pilot valve, and means for apply ing a restraining friction between the disc and sleeve for guarding against untimely movement of the disc. 35 15. In a power control for a pneumatic con protruding through one side of the housing, a sleeve surrounding the protruding portion of the 40 stem, a pilot valve surrounding the sleeve and arranged to slide thereupon, means to set up fric tional resistance to the sliding of said valve upon said sleeve for holding the valve in slid position and lost motion connections between the stem and 45 the pilot valve for sliding the latter upon said SIGGVE. ' HERMAN BUSCH.