Abstract:
A blower assembly for a pneumatic tube system sequences start of two pneumatic sources, such as blowers, to pneumatically position passive closure devices, such as spools, that shift the blower assembly between pressure and vacuum modes. Thereafter, both blowers are cooperatively operated. Use of two blowers whose combined output achieves the desired pneumatic performance avoids the increased cost of having one or more blowers that only operate only for one mode of either pressure or vacuum. The passive closure devices reliably and rapidly position to enhance performance, especially as compared to electrically actuated closure devices.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of, and hereby incorporates by reference in its entirety, the commonly owned U.S. Provisional Application Serial No. 60/296,216 that was filed on Jun. 6, 2001 by Kieran P. Nickoson: entitled: “AIR VALVE.” 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to a pressure regulation apparatus ideally suited for controlling transportation of materials in either of at least two directions, and more particularly to a bi-directional (pressure-vacuum) single tube pneumatic system.  
         BACKGROUND OF THE INVENTION  
         [0003]    Pneumatic tube systems are well known for transporting capsules or carriers to one of several locations and back by selectively using pressure or vacuum to propel the carrier through a tube. Thereby, transactions requiring paper documentation may be conducted across barriers erected for security or across distances between parties.  
           [0004]    Single tube installations are generally preferred as being simpler to install and use. Carriers are selectively transported in either direction within the single tube. To this end, blower assemblies are incorporated into a main station of the pneumatic tube system for selectively generating the pressure or vacuum. Much development has been performed in making blower assemblies that rapidly transfer the carrier yet slow the carrier at each station.  
           [0005]    A challenge for known blower assemblies is to rapidly switch between pressure and vacuum modes in an economical and reliable manner. One technique is to provide two separately assigned blowers, either at opposite ends of the pneumatic tube system or within a blower assembly. Each blower is configured to propel a carrier in a direction opposite to the other. One blower assembly is unused during each operation, either from main station to remote station or remote to main station. Thus, such known separately assigned blower assemblies suffer from an undesirable requirement for having two large blowers with half of the pneumatic power unused.  
           [0006]    In an attempt to overcome the advantages of separately assigned blowers, it is also known to have an electrically actuated air valve to selectively couple the intake or the exhaust of a single blower to the pneumatic tube system. Thereby, the full pneumatic power available is used during each operation. However, in addressing the excess pneumatic power disadvantage, such actuated blower assemblies introduce problems associated with the electrically actuated air valve. Specifically, the electrically actuated air valve reduces the overall reliability of the blower assembly by adding an component that can fail or that requires additional periodic servicing.  
           [0007]    In addition, although reducing the per unit cost of the blower assembly by eliminating a second blower, the economic cost of using the pneumatic tube system is increased by the electrically actuated air valve. This increased economic cost is due to the delay in switching by the electrically actuated air valve as compared to separately assigned blower assemblies. The additional time in seconds for each customer transaction means that the pneumatic tube assembly can perform fewer customer transactions over a period of time. Thus, additional pneumatic tube assemblies have to be installed for additional capacity or customer-waiting time has to be increased.  
           [0008]    Thus, a significant need exists for a blower assembly for a pneumatic tube system that rapidly switches between pressure and vacuum modes, yet does not leave half of the blower capacity unused during each operation.  
         BRIEF SUMMARY OF THE INVENTION  
         [0009]    The invention overcomes the above-noted and other deficiencies of the prior art by providing an apparatus and method for providing selectively switched pressure and vacuum to a pneumatic tube system that uses at least two pneumatic sources to cooperatively provide the required amount of pressure or vacuum during each operation. In particular, passive air valves, such as air spools, are positioned by sequencing the order in which the two pneumatic sources are activated to switch between pressure and vacuum. The passively switched air valves tend to be low cost, reliable, and rapidly positioned.  
           [0010]    As an additional benefit, commercially available blowers tend to have a purchase price that is disproportionate to their pneumatic power capacity. In particular, it tends to be more economical to generate the same amount of pneumatic power with two smaller blowers than with one larger blower. Consequently, the approach of sequencing two smaller blowers that cooperate in achieving the desired pneumatic power capacity has an additional advantage over separately assigned blower assemblies.  
           [0011]    In one aspect of the invention, a method is described for selectively providing pneumatic pressure and vacuum to a system manifold with an air shifter that communicates between an atmosphere port and the system manifold. For a selected one of pneumatic pressure and vacuum, the air shifter is pneumatically positioned by activating a first pneumatic source first. After a delay for the pneumatically positioning of the air shifter, a second pneumatic source is started to increase the selected one of pneumatic pressure and vacuum to the system manifold. Thereby, a reliable and rapid switching of the mode of the blower assembly is accomplished by pneumatically positioned elements.  
           [0012]    In another aspect of the invention, a blower assembly is described for a pneumatic tube system that uses pneumatic pressure and vacuum to propel a carrier through a pneumatic carrier tube. The blower assembly shifts pressure or vacuum between a system manifold, which communicates with the pneumatic tube system, and an atmosphere port. The blower assembly accomplishes this shifting by including an intake passage and an exhaust passage that both communicate between the system manifold and the atmosphere port. The blower assembly includes two pneumatic sources that intake air from the intake passage and expel air into the exhaust passage. An intake closure device in the intake passage and an exhaust closure device in the exhaust passage are positioned to pressure mode when the one of the pneumatic sources is activated first and are positioned to vacuum mode when the other pneumatic source is activated first.  
           [0013]    In yet a further aspect of the invention, a pneumatic tube system employs a blower assembly that includes an air shifter that pneumatically responds to a first blower being started before a second blower to provide pressure to a pneumatic carrier tube. The blower assembly further responds to the second blower being started before the first blower to provide vacuum to the pneumatic carrier tube. Thereby, all of the blower capacity is used for both providing pressure or vacuum to the pneumatic carrier tube, avoiding the uneconomical cost of dedicating one or more blowers to each mode of operation.  
           [0014]    These and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0015]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and, together with the general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention.  
         [0016]    [0016]FIG. 1 is a perspective view of a pneumatic tube system having a main station and a remote station, the main station partially cut away to expose a blower assembly consistent with the present invention.  
         [0017]    [0017]FIG. 2 is a perspective view of a blower side of a chassis of the blower assembly of FIG. 1 showing intakes and exhausts of two blower chambers.  
         [0018]    [0018]FIG. 3 is a perspective view of an air shifter side of the blower assembly of FIG. 2 exposed and to show air spools positioned for pressure mode.  
         [0019]    [0019]FIG. 4 is a perspective view of FIG. 3, annotated to show the initial conditions of switching to vacuum mode.  
         [0020]    [0020]FIG. 5 is a perspective view of FIG. 4 with a floating plate of an exhaust spool moved by activation of the second blower to close the exhaust port of the second blower to the system manifold.  
         [0021]    [0021]FIG. 6 is a perspective view of FIG. 5 with the exhaust spool fully translated to close the exhaust passage to the system manifold.  
         [0022]    [0022]FIG. 7 is a perspective view of FIG. 6 with the intake spool switched by the second blower to both open the intake passage to the atmosphere port and to close the intake passage to the system manifold.  
         [0023]    [0023]FIG. 8 is a flow diagram of operating the pneumatic tube system of FIG. 1 illustrating sequenced activation of the two blowers of the blower assembly to selectively provide pressure or vacuum. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    With reference to the Drawings, wherein like numbers refer to like components through the several views, FIG. 1 depicts a blower assembly  10  of a pneumatic tube system  12  that rapidly conveys and returns a capsule or carrier  14  between a main station  16  and a remote station  18 .  
         [0025]    A housing of the main station  16  is removed in FIG. 1 to expose the blower assembly  10  as well as the pneumatic connections to a pneumatic tube  20  that transports the carrier  14  between stations  16 ,  18 . In addition, portions of the blower assembly  10  are exposed to show a first pneumatic source, depicted as an upper blower  22 , and a second pneumatic source, depicted as a lower blower  24 . It will be appreciated that an outer cabinet  26  of the blower assembly  10  provide an air-tight barrier with the exception of a system manifold  28  that communicates with the pneumatic tube  20  and an atmosphere port  30  that is open to the ambient environment.  
         [0026]    It will be understood that the pneumatic connections to the pneumatic tube  20  provide for starting a carrier  14  upward when being sent and for slowing a carrier  14  when returned. In addition, the remote station  18  also includes an atmosphere port (not shown) for exhausting air when receiving a carrier  14  and for an intake of air when a carrier  14  is returned.  
         [0027]    Components of a control system  32  of the pneumatic tube system  12  are depicted in diagram fashion. A controller  34  of the control system  32  receives a pressure command signal from a SEND button  36  on the main station  16  for initiating pressure to convey the carrier  14  to the remote station  18 . The controller  34  also receives a vacuum command signal from a SEND button  40  on the remote station  18  for initiating vacuum to return the carrier  14  from the remote station  18 . Based on the order in which the blowers  22 ,  24  are activated, the blower assembly  10  performs a selected one of the two modes through the action of a pneumatically switched air shifter  46 , described in greater detail below. The controller  34  activates the upper and lower blowers  22 ,  24  for a preset duration sufficient for the to distance to be traversed by the carrier  14 , although it will be appreciated that closed-loop feedback of carrier position may be used for some applications.  
         [0028]    In the illustrative embodiment, the controller  34  includes a Siemens LOGO! Programmable Logic Module Model 24RC, which is installed in the remote station  18 . Motor control signals close power relays (not shown) in the main station  16  to actuate the two blowers  22 ,  24 . However, it will be appreciated that the controller  34  may be implemented with various analog or digital components capable of sequentially activating the two blowers  22 ,  24 . In addition, although only two stations  16 ,  18  are shown, it will be appreciated that aspects of the invention have application to pneumatic tube systems  12  employing additional stations.  
         [0029]    In addition, in the illustrative embodiment, each blower  22 ,  24  is a two-stage throughflow vacuum motor Model 115923 by AMETEK Lamb Electric of Kent, Ohio. The combined pneumatic power capacity of the two blowers  22 ,  24  is sufficient to propel a carrier  14 . Consequently, the more costly alternatives are avoided.  
         [0030]    [0030]FIG. 2 depicts a chassis  48  of the blower assembly  10  shown from a similar perspective as FIG. 1 with the upper and lower blowers  22 ,  24  removed to illustrate an upper blower chamber  50  and a lower blower chamber  52 . These chambers  50 ,  52  are in pneumatic communication through four ports  54 - 60  with the air shifter  46  on an opposite side of the chassis  48 . In particular, an upper intake blower port  54  communicates with an upper intake portion  62  of the upper blower chamber  50 . An upper exhaust blower port  56  communicates with an upper exhaust portion  64  of the upper blower chamber  50 . The upper blower  22  (not shown in FIG. 2) separates the upper intake and exhaust portions  62 ,  64  of the upper blower chamber  50  and draws air from the upper intake blower port  54  and expels air through the upper exhaust blower port  56 . Similarly, a lower intake blower port  58  communicates with a lower intake portion  66  of the lower blower chamber  52 . A lower exhaust blower port  60  communicates with a lower exhaust portion  68  of the lower blower chamber  52 . The lower blower  24  (not shown in FIG. 2) separates the lower intake and exhaust portions  66 ,  68  of the lower blower chamber  52  and draws air from the lower intake blower port  58  and expels air through the lower exhaust blower port  60 .  
         [0031]    [0031]FIG. 3 depicts a side of the blower assembly  10  approximately opposite to that shown in FIG. 2 to illustrate the air shifter  46  responding to the blowers  22 ,  24  (not shown in FIG. 3) to operate in either pressure or vacuum mode. An airtight panel  70  is transparently depicted to expose an intake passage  72  that communicates between the atmosphere port  30  and the system manifold  28 . An exhaust passage  74  also communicates between the atmosphere port  30  and the system manifold  28 , but otherwise is isolated along its length from the intake passage  72 . The upper and lower intake blower ports  54 ,  58  communicate with the intake passage  72  and the upper and lower exhaust blower ports  56 ,  60  communicate with the exhaust passage  74 .  
         [0032]    An intake passage closure device, depicted as an intake spool  76 , vertically translates within the intake passage  72  to form an intake chamber  78  that selectively closes the upper and lower intake blower ports  54 ,  58  to the system manifold  28  or to the atmosphere port  30 . The intake spool  76  is comprised of an upper plate  80  connected to a lower plate  82  via a long connecting rod  84 . The intake spool  76  shaped to vertically translate within the intake passage  72  with lower plate  82  forming a seal to walls  86  of the intake passage  72 . In particular, without any pressure from the blowers  22 ,  24 , the upper plate  80  of the intake spool  76  rests upon an intake passage valve seat  88 , sealing the intake blower ports  54 ,  58  from the system manifold  28 . In this lower position, the lower plate  82  is positioned below the atmosphere port  30 , exposing the intake blower ports  54 ,  58  to the atmosphere port  30 . In this lowered position, the lower plate  82  also closes the atmosphere port  30  to a lower manifold  90 .  
         [0033]    An exhaust passage closure device, depicted as an exhaust spool  92 , forms an exhaust chamber  94  in the exhaust passage  74  that selectively closes the upper and lower exhaust ports  56 ,  60  to the system manifold  28  or to the atmosphere port  30 . The exhaust spool  92  is comprises of an upper floating plate  96  that slides on a short connecting rod  98  that is connected to a lower fixed plate  100 . The floating plate  96  is constrained to slide on the connecting rod  98  between an upper Cotter pin  102  and a lower Cotter pin  104 . The exhaust spool  92  is shaped to vertically translate within the exhaust passage  74  with each plate  96 ,  100  sealing to walls  106  of the exhaust passage  74 . In particular, without any pressure from the blowers  22 ,  24 , the fixed plate  100  rests upon a lower exhaust valve seat  108 , sealing the upper and lower exhaust blower ports  56 ,  60  from the lower manifold  90 , and thus to the atmosphere port  30 . Also, the floating plate  96  rests on the lower Cotter pin  104 , positioned to expose all of the upper exhaust blower port  56  and most of the lower exhaust port  60  to the system manifold  28 .  
         [0034]    Air flow is depicted that illustrates how the above-described positions of the intake spool  76  and exhaust spool  92  are maintained by first activating the upper blower  22  (not shown in FIG. 3) and then activating the lower blower  24  (not shown in FIG. 3). Thereby, the blower assembly  10  performs in pressure mode, drawing in air from the atmosphere port  30  that is expelled through the system manifold  28 . In particular, when the upper blower  22  is activated, air flows as depicted at arrow  110  between the atmosphere port  30  and the upper intake blower port  54 . The air flows in the exhaust passage  74  as depicted at arrow  112  from the upper exhaust blower port  56  to the system manifold  28 .  
         [0035]    The air pressure in the system manifold  28  and exhaust chamber  94  above both spools  76   92  is allowed to increase for a period such a half of a second before activating the lower blower  24 . Then the lower blower  24  is activated to cooperatively increase the pneumatic capacity of the blower assembly  10 . The additional air flow is depicted at arrow  114  between the atmosphere port  30  and the lower intake blower port  58 . The additional air flow in the exhaust passage  74  is depicted at arrow  116  from the lower exhaust blower port  60  to the system manifold  28 . It will be appreciated that the half-second delay before activating the lower blower  24  is illustrative. The amount of delay may vary for different applications, accommodating factors such as the spool up time of a blower, inertia and friction of a given air shifter, and other considerations.  
         [0036]    FIGS.  4 - 7  depict a sequence as the air shifter  46  switches to vacuum mode. FIG. 4 depicts the air shifter  46  of the blower assembly  10  beginning to switch to the vacuum mode.  
         [0037]    Initially with both blowers  22 ,  24  (not shown in FIG. 4) inactive, both spools  76 ,  92  rest in their downward, pressure mode state. Vacuum mode begins with the lower blower  24  being activated. Air flow, as depicted at arrow  118 , is drawn into the lower blower intake blower port  58  from the atmosphere port  30 . The air flow, as depicted by arrows  120 ,  122 , is then expelled from the lower exhaust blower port  60  on both the top and bottom respectively of the floating plate  96  of the exhaust spool  92 .  
         [0038]    [0038]FIG. 5 depicts the floating plate  96  of the exhaust spool  92  shifting upward along the connecting rod  98  until contacting the upper Cotter pin  102  (not shown in FIG. 5) due to the air flow from the lower exhaust blower port  60 , as depicted by arrow  124 . The floating plate  96  develops sufficient momentum before contacting the upper Cotter pin  102  to raise the entire exhaust spool  92 , thereby causing the fixed plate  100  to unseat from the exhaust passage valve seat  108 . Air flow from the lower exhaust blower port  60  thus increases air pressure below both spools  76 ,  92  in the lower manifold  90 .  
         [0039]    [0039]FIG. 6 depicts the exhaust spool  92  having been raised to its upper limit by the air flow from the lower exhaust blower port  60 , as depicted by arrow  126 . In particular, the exhaust spool  92  is lighter than the intake spool  76  due to the lighter weight of the short connecting rod  98  as compared to the long connecting rod  84 . Thus, the exhaust spool  92  is switched to its upper limit first, causing both upper and lower exhaust blower ports  56 ,  60  to be closed to the system manifold  28 .  
         [0040]    [0040]FIG. 7 depicts the intake spool  76  switched to its upper limit due to the air flow from the lower exhaust blower port  60 . In particular, the increased air pressure in the lower manifold  90  against the lower plate  82  of the intake spool  76  causes the upper plate  80  to unseat from the intake passage valve seat  88 . In this state, air flows, as depicted at arrow  128 , from the system manifold  28  into the lower intake blower port  58 . The expelled air flows, as depicted at arrow  130 , from the lower exhaust blower port  60  the blower assembly  10  through atmosphere port  30 . With the air shifter  46  switched to the pressure mode, the upper blower  22  is now activated to cooperatively increase the vacuum capacity of the blower assembly  10 . Air flows into the upper intake blower port  54  from the system manifold  28 , as depicted at arrow  132 , and is expelled from the upper exhaust blower port  56  to the atmosphere port  30 , as depicted at arrow  134 .  
         [0041]    With reference to FIG. 8, the operation of the blower assembly  10  is described in another way by a sequence of steps, or routine  200 . Initially, both blower motors  1  (upper) and  2  (lower) are off (block  202 ). Air pressure is equalized within the blower assembly, allowing the exhaust spool to be relaxed in a down position, allowing blower exhaust ports  1  and  2  to communicate with the system manifold (block  204 ). In addition, the intake spool is relaxed in a down position, allowing the blower intake ports  1  and  2  to communicate with the atmosphere port (block  206 ).  
         [0042]    With the blower system in its default, inactive state, a determination is made as to whether pressure mode has been selected (e.g., carrier is at the main station and is to be sent to the remote station) (block  208 ). If so, then the blower motor  1  (upper) is turned on (block  210 ). Thereafter, a delay state is used with blower  1  on, thereby increasing the air pressure above the intake and exhaust spools to hold them down in the pressure mode state (block  212 ). With the spools thus held, the blower motor  2  (lower) is turned on to increase pressure to the system (block  214 ). With both blowers on, a determination is made as to whether the capsule or carrier has reached the remote station (block  216 ).  
         [0043]    This determination may be made by referencing a timer to see if sufficient time has elapsed, by referencing a sensor triggered by the carrier, or by a manual operator input indicating successful transfer. If not at the remote station, then block  216  repeats. Else, blower motors  1  and  2  are turned off (block  218 ), wherein generally an air cushion at remote station slows the carrier.  
         [0044]    If at block  208  pressure was not selected, then a determination is made as to whether vacuum has been selected (block  220 ), such as to return the carrier from the remote station to the main station. If selected, then the blower motor  2  (lower) is turned on (block  222 ). A delay is imposed in this state to allow for the spools to switch to the vacuum mode (block  224 ). In particular, the floating plate of the exhaust spool is raised with sufficient momentum to raise the exhaust spool off of its valve seat. The expelled air from blower motor  2  thereafter raises the exhaust spool to its fully raised (upper) position, allowing export ports of both blower motors to be in communication with the atmosphere port. The expelled air from the blower motor  2  (lower) also causes the intake spool to raise, causing the intake ports of both blower motors to be closed with respect to the atmosphere port and open with respect to the system manifold. With the blower assembly thus configured for vacuum mode, the blower motor  1  (upper) is turned on (block  226 ) to increase vacuum to the system. With both blowers on, a determination is made as to whether the capsule or carrier has returned to the main station (block  228 ). This determination may be made by referencing a timer to see if sufficient time has elapsed, by referencing a sensor triggered by the carrier, or by a manual operator input indicating successful transfer. If not at the main station, then block  228  repeats. Else, blower motors  1  and  2  are turned off (block  230 ), wherein generally an air cushion at the main station slows the carrier and the spools are allowed to relax to their default pressure mode state.  
         [0045]    In use, an air shifter  46  is used to pneumatically switch a blower assembly  10  between pressure and vacuum modes for a pneumatic tube system  12  based upon the sequence in which two blower motors  22 ,  24  are activated. In particular, each blower motor positions spools  76 ,  92  in the air shifter  46  to the appropriate mode (pressure, vacuum) before the other blower is activated to increase pneumatic capacity. By virtue of the foregoing, a highly reliable passive air shifter  46  increases the operating speed and durability of the blower assembly  10  while allowing cost effective smaller blower motors to be used in cooperation to achieve the desired pneumatic capacity.  
         [0046]    While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications may readily appear to those skilled in the art. For example, the illustrative embodiment described herein includes a specific arrangement of air passages  72 ,  74 , an arrangement of ports  54 - 60  in these passages  72 ,  74 , and two pneumatically positioned spools  76 ,  92  to selectively switch the communication of the ports  54 - 60 . It will be appreciated that various arrangements of spools, ports, and passages may be arranged in order to accomplish a similar effect consistent with aspects of the present invention. For example, the blower assembly  10  may have a default position of vacuum mode wherein the spools are switched for pressure mode. As an additional example, selecting either mode causes the spools to switch.  
         [0047]    It will further be appreciated that additional blower motors used in parallel or serially with the blower motors described herein may be employed to further increase the pneumatic capacity or to allow the use of smaller blower motors.