Abstract:
A blower unit is provided which is suitable for use in a pneumatic transmission system. The blower unit includes a housing having at least two inlet/outlet openings through which air can flow. Disposed within the housing are one or more blower motors, each blower motor for moving a volume of air from one of the at least two inlet/outlet openings to another. Also disposed within the housing are one or more bypass paths, each bypass path providing a route by which air can flow without flowing through an associated blower motor. A valve element is disposed within at least one of the bypass paths for substantially blocking air-flow through that bypass path when the associated blower motor is active.

Description:
FIELD OF THE INVENTION 
     The present invention is directed generally to a blower assembly suitable for use with a pneumatic transmission system. Specifically, this invention relates to a blower assembly which includes a blower motor and a bypass path. The bypass path provides an alternate route through the blower assembly, so that air may flow through the bypass path rather than the blower motor for reduced path resistance and therefore improved overall efficiency. In one aspect, the invention relates to a pneumatic transmission system with a blower unit having a blower motor and a bypass path. 
     BACKGROUND OF THE INVENTION 
     Blower assemblies where air flow can be selectively directed in either direction are commonly used in pneumatic transmission systems, which are widely known and are used to transmit articles from a first point to a second point, which is remote from the first point. Pneumatic transmission systems usually include at least two stations, a tube or conduit extending between the two stations, and a carrier which can be positioned within the tube so that it can be transmitted from one station to another. 
     A common example of a pneumatic transmission system is in drive-in bank teller facilities where business is conducted via a carrier transmitted between the bank and the remote drive-in terminal. Other examples include pneumatic transmission systems used for sending documents between different floors in a building or between offices which are located some distance apart. 
     Typical blower assemblies include two opposing blowers for selectively providing air-flow in opposite directions in the tube or conduit connecting the two stations. FIG. 1 shows an example of a pneumatic transmission system having this type of a conventional blower assembly. The blower assembly  10  includes a pair of vacuum cleaner blower motors  15 A and  15 B positioned in a blower tube  20  in pneumatic series with each other, meaning the vacuum cleaner blower motors  15 A and  15 B are within the same air flow path. Furthermore, the vacuum cleaner blower motors  15 A and  15 B are spatially separated from each other within the blower tube  20 . The blower tube  20  and the vacuum cleaner blower motors  15 A and  15 B are disposed within a blower housing  25 . The blower tube  20  is substantially open on one end and closed on the other end except for communication with a vent/inlet  30 , which is for supplying or exhausting air. The blower assembly  10  communicates with a transport tube  35  via a conduit  40 . The conduit  40  is attached at one end to the blower housing  25  and at its other end to a check/relief valve  45 . The check/relief valve  45  controls air-flow between the conduit  40  and the transport tube  35  such that air may flow between the transport tube  35  and the conduit  40  or, alternately, air may flow between the conduit  40  and a second conduit  50 . The second conduit  50  is connected at one end to the check/relief valve  45  and at its other end to a station  55 . The transport tube  35  is connected to the station  55  at one end and to a second station  60  at its other end, and is of sufficient internal diameter such that a carrier  65  can be transmitted therethrough. 
     During normal operation, either the first blower motor  15 A or the second blower motor  15 B is activated based on a desired direction of travel for the carrier  65  through the transport tube  35 . In a case where the first blower motor  15 A is activated, air is pulled into the blower tube  20  through the vent/inlet  30  and pushed out of the blower tube  20  through the second blower motor  15 B, then through the blower housing  25 , the conduit  40 , the check/relief valve  45 , and the second conduit  50  to the station  55 . In a case where the second blower motor  15 B is activated, air is pushed out of the blower tube  20  through the first blower motor  15 A to the vent/inlet  30 , and pulled into the blower tube  20  through the blower housing  25 , the conduit  40 , and the check/relief valve  45  from the transport tube  35 . 
     One disadvantage of a pneumatic transmission system that includes a conventional blower assembly having opposing blower motors is that since the path of air-flow includes a non-activated blower motor, a path resistance of the pneumatic transmission system is increased. Thus, an additional amount of force is required for the air to travel through the pneumatic transmission system due to the path resistance encountered at the non-activated blower motor, reducing the distance a given blower motor can cause a driven member such as a carrier to travel. This additional amount of force also results in an increased amount of work for the activated blower motor over time, which decreases the efficiency of the pneumatic transmission system. Such inefficiency can result in an increase in the cost of operation as well as increased wear on the blower motors. For the foregoing reasons, there is a need for a pneumatic transmission system that has a reduced path resistance for air flow and can therefore operate more efficiently and with an increased transmission range. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a blower assembly suitable for use with a pneumatic transmission system wherein the blower assembly provides a path having a reduced path resistance for air flow. 
     Another object of the present invention is to provide a pneumatic transmission system having an increased range over which a carrier may be transmitted and an improved operating efficiency by reducing the pneumatic resistance of the system. 
     A pneumatic transmission system having features of the present invention comprises at least a first and a second station, each for sending or receiving a carrier, a transport conduit connected between the first station and the second station, wherein the transport conduit permits a transfer of the carrier between the first station and the second station, and a blower assembly. In one embodiment of the invention, the blower assembly comprises a housing and a blower, a bypass path, and a bypass valve all disposed within the housing. The housing is connected to the first station such that air can flow between the housing and the first station. The blower has an inlet/outlet opening which can serve as both an air inlet for providing air from the atmosphere through the housing to the pneumatic transmission system and an air vent for exhausting the air from the pneumatic transmission system through the housing to the atmosphere. The blower is for moving a volume of the air through the transport conduit. The bypass path provides a path through which air can flow without flowing through the first blower. The bypass valve is for blocking the flow of the air through the bypass path when the blower is active. 
     In another embodiment of the invention, a pneumatic transmission system is provided comprising a first station and a second station, both for sending or receiving a carrier, a transport conduit connected between the first station and the second station for permitting a transfer of a carrier between the first station and the second station, and a blower assembly. The blower assembly includes a housing and a first interior wall, a first blower, a second interior wall, a second blower, and a valve assembly all disposed within the housing. The housing is connected to the first station such that air can flow between the housing and the first station. Also, the housing has an inlet/outlet opening which can serve as an air inlet for providing air from atmosphere through the housing to the pneumatic transmission system and can serve as an air outlet for exhausting air from the pneumatic transmission system through the housing to the atmosphere. The first interior wall has a blower aperture and a bypass aperture. The first blower is mounted through the blower aperture of the first interior wall, while the bypass aperture of the first interior wall provides a path through which the air can flow without flowing through the first blower. The second interior wall has a blower aperture and a bypass aperture. The second blower is mounted through the blower aperture of the second interior wall, while the bypass aperture of the second interior wall provides a path through which the air can flow without flowing through the second blower. The first blower is for moving a volume of air through the transport conduit in a first direction, whereas the second blower is for moving a volume of the air through the transport conduit in a second direction. The valve assembly operates to allow air to pass through the bypass aperture of the second interior wall while the first blower motor is operating and operates to allow air to pass through the bypass aperture of the first interior wall while the second blower motor is operating. 
     A bypass valve suitable for use in a blower assembly having features of the present invention may include a valve guide, a valve rod slidably engaged with the valve guide, and a blocking member attached to an end portion of the valve rod. Such a bypass valve may be constructed such that the valve rod is capable of sliding with respect to the valve guide in a direction to block the flow of air through a bypass path with the blocking member, and in a second direction to allow the flow of air through the bypass path. If a second bypass path is present, a second blocking member may be attached to a second end portion of the valve rod. In this case, the bypass valve may be constructed such that the valve rod is capable of sliding with respect to the valve guide in a direction to block the flow of air through a bypass path with the blocking member while allowing the flow of air through the second bypass path, and in a second direction to allow the flow of air through the bypass path while blocking the flow of air through the second bypass path with the second blocking member. 
     Alternately, a bypass valve suitable for use in a blower assembly having features of the present invention may be an electromechanically operating valve which operates based on a control signal to selectively block or allow air to pass through one or more bypass paths. 
     Finally, the present invention can be implemented in a pneumatic transmission system having a plurality of stations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
     FIG. 1 is a block diagram illustrating a conventional pneumatic transmission system; 
     FIG. 2 is a block diagram of a pneumatic transmission system embodying features of the present invention; 
     FIGS. 3A and 3B are views of a blower assembly used in the pneumatic transmission system of FIG. 2 showing alternate positions of a valve included in the blower assembly; and 
     FIG. 4 is a block diagram of another version of a pneumatic transmission system embodying features of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2 illustrates a pneumatic transmission system containing an embodiment of a blower assembly in accordance with the present invention. The present system comprises a first station  100  and a second station  105  connected by a substantially air tight transport tube  110 , which is open to the atmosphere at the second station  105 , with a blower assembly  115  being positioned within a supply/exhaust branch  120  which is connected to the first station  100 . The supply/exhaust branch  120  includes a conduit  125  which is substantially airtight and a muffler  130  which is open to the atmosphere and can provide air from the atmosphere to the pneumatic transmission system or can allow the exhaust of air from the pneumatic transmission system to the atmosphere. Conduit  125  does not have to be of a similar internal diameter as the transport tube  110  because no carrier is transported therethrough, only air. Conduit  125  is attached at one end to a first blower-housing port  135  in a blower housing  140  and at its other end to check/relief valve  145 . A second conduit  150  connects the check valve  145  to the first station  100 . The check valve  145  also communicates with the transport tube  110  directly, through a conduit port  155 , and comprises a leaf  160 , which is adapted to cover the conduit port  155  in certain air flow situations. The blower assembly  115  is comprised of a substantially air tight blower housing  140 , shown in phantom, which has the first blower-housing port  135  in a first end portion and a second blower-housing port  165  in a second end portion opposite the first end portion. A solenoid valve  170  is mounted to the first end portion of the blower housing  140  such that, when actuated, the solenoid valve  170  operates to block the first blower-housing port  135  with a valve disk  175 , preventing air flow through the first blower-housing port  135 . The present invention, however, is not limited to a solenoid valve. A first interior wall  180 A and a second interior wall  180 B are positioned in the blower housing  140  such that they partition the blower housing  140  into a first chamber I between the first end portion of the blower housing  140  and the first interior wall  180 A, a second chamber II between the first and second interior walls  180 A and  180 B, and a third chamber III between the second interior wall  180 B and second end portion of the blower housing  140 . Each of the first and second interior walls  180 A and  180 B includes a blower motor aperture  185 A and  185 B, respectively, and a bypass aperture  190 A and  190 B, respectively. A first blower motor  195 A is positioned in the first blower motor aperture  185 A, and a second blower motor  195 B is positioned in the second blower motor aperture  185 B. A bypass valve  200  is positioned in the second chamber II of the blower housing  140 . The bypass valve  200  includes a valve guide  205  and a valve rod  210  slidably mounted to the valve guide  205 . The valve guide  205  is preferably fixed in position relative to the blower housing  140  and the first and second interior walls  180 A and  180 B. The bypass valve  200  also includes a first blocking member  215 A and a second blocking member  215 B. The first blocking member  215 A is fixed to a first end portion of the valve rod  210  such that, in a first position, the bypass valve  200  operates to block the first bypass aperture  190 A with the blocking member  215 A, substantially preventing air flow through the first bypass aperture  190 A. The second blocking member  215 B is fixed to a second end portion opposite the first end portion of the valve rod  210  such that, in a second position, the bypass valve  200  operates to block the second bypass aperture  190 B with the blocking member  215 B, substantially preventing air flow through the second bypass aperture  190 B. The supply/exhaust branch  120  is connected to the first station  100  at one end and open to the atmosphere at the muffler  130  for supplying or exhausting air. The first station  100  can be a closed station, meaning that it can be sealed by closing a door  220  so that, except for the supply/exhaust branch  120 , it is substantially closed to the atmosphere during transport of a carrier  225 . The second station  105  can be either a closed station with a vent or a station which is open to the atmosphere during transport of the carrier  225 , but it is shown as an open station. The carrier  225  is capable of being filled with items to be transferred and is inserted at either station for transfer to the other station. 
     The transport tube  110 , which is connected to the first station  100  at one end and to the second station  105  at its other end, is of sufficient internal diameter such that the carrier  225  can be transmitted therethrough. The transport tube  110  can have any spatial orientation and can include curved portions, straight portions, vertical portions, and horizontal portions, dependent upon the circumstances under which the system is going to be used. For example, the approach leg  230  is shown as a curve from a horizontal direction to a vertical downward direction. However, this approach leg  230  can also remain horizontal or curve in a vertical upward direction as it connects with the second station  105 . The transport tube  110  and the carrier  225  can have nearly any desired dimension and cross-section, dependent on the system needs. The transport tube  110  can include any transmission line of any cross-sectional form having a pneumatic channel formed therethrough. 
     To send the carrier  225  from the first station  100  to the second station  105 , the second blower motor  195 B is activated to intake air through the muffler  130  and to apply pressurized air to the carrier  225 , which creates a ΔP across the carrier  225  and moves the carrier  225  upwardly, out of the first station  100 , and then horizontally through the transport tube  110  toward the second station  105 . The second blower motor  195 B can generate approximately 5 psig behind the carrier  225 . Likewise, to send the carrier  225  from the second station  105  to the first station  100 , the first blower motor  195 A would be activated instead of the second blower motor  195 B, to exhaust air through the muffler  130 , thereby creating at least a partial vacuum in the transport tube  110  on the first station  100  side of the carrier  225 , while the second station  105  side of the carrier  225  remains at 0 psig because it is open to the atmosphere. This ΔP across the carrier  225  generates a force moving the carrier  225  in the opposite, or first station  100  direction. 
     In order to send the carrier  225  from the first station  100  to the second station  105 , the carrier  225  is placed in the transport tube  110  and the door  220  is shut and sealed. The second blower motor  195 B is then activated. This can be done by an operator actuating a first-station switch  235 , which is coupled to a controller  240 . The controller  240  is coupled to the first and second blower motors  195 A and  195 B for selective activation of the first and second blower motors  195 A and  195 B. When the first-station switch  235  is actuated, the first-station switch  235  sends a control signal to the controller  240 . The controller  240  receives the control signal from the first-station switch  235  and provides a control signal to the second blower motor  195 B, to thereby activate the second blower motor  195 B. The controller  240  is also coupled to a sensor  245  which is positioned near or on the transport tube  110 . The sensor  245  does not need to be in physical contact with the transport tube  110 , but it must be positioned such that it is able to sense the carrier  225  as the carrier passes a predetermined location in the transport tube  110  related to the approach of the carrier  225  to the second station  105 . The present invention is not limited to an electrical coupling, or even a physical connection between the controller  240  and its peripherals. 
     The operation of the second blower motor  195 B causes the bypass valve  200  to move to a position wherein the second blocking member  215 B blocks the second bypass aperture  190 B. A more detailed explanation of the operation of the bypass valve  200  is provided below in conjunction with FIGS. 3A and 3B. The second blower motor  195 B blows air through the conduit  125  and into the check/relief valve  145 . The air flow into the check/relief valve  145  exerts pressure onto the leaf  160 , thereby causing the leaf  160  to cover the conduit port  155 . With the conduit port  155  blocked, air flows out of the check/relief valve  145 , through the second conduit  150 , to the first station  100  and creates a ΔP across the carrier  225 , thus moving it towards the second station  105 . The blower motors  195 A and  195 B used in this embodiment can be standard vacuum cleaner blower motors such as Model No. 115923 manufactured by Ametek. The first and second blower motors  195 A and  195 B are substantially equal in size and in output capacity, although mounted in opposite directions. The first and second blower motors  195 A and  195 B are capable of operating at approximately 23000 RPM and of generating approximately 124 CFM. 
     As the carrier  225  moves through the transport tube  110 , it reaches the portion of the transport tube  110  where it is detected by the sensor  245 . The sensor  245  detects the presence of the carrier  225  as it passes a predetermined location in the transport tube  110  and provides a control signal to the controller  240  indicative of that detection. The controller  240  receives this control signal from the sensor  245  and provides a control signal to the second blower motor  195 B to thereby deactivate the second blower motor  195 B, to the solenoid valve  170  to thereby actuate the solenoid valve  170  thus blocking the first blower-housing port  135  with the valve disk  175 , and to start a timer  250 . The timer  250  can be an external peripheral device or it can be integrated in the controller  240 . In this embodiment, the timer  250  is preferably a Model No. RTE B21 manufactured by IDEC. An air block is created in the conduit  125 , and thus in the transport tube  110 , by the blocking of the first blower-housing port  135  by the valve disk  175 . 
     Once the air block is on, a finite amount of air remains in the transport tube  110  between the carrier  225  and the first station  100  because no additional air can get by the solenoid valve  170  and through the first blower-housing port  135  in either direction. As the carrier  225  continues to move through the transport tube  110  towards the second station  105 , the volume of the portion of the transport tube  110  between the air block and the carrier  225  increases, and as that volume increases, the air pressure in the transport tube  110  behind the carrier  225  decreases because the amount of air between the air block and the carrier  225  remains substantially constant. The pressure on the second station  105  side of the carrier  225 , however, is substantially constant at 0 psig because the second station  105  is open to the atmosphere. Therefore, as the pressure between the air block and the carrier  225  decreases as the carrier  225  moves through the final approach section  230  of the transport tube  110 , the carrier  225  slows down due to the decreasing ΔP across the carrier  225 . In this embodiment, the carrier  225  reaches a point along the transport tube  110  where the pressure behind the carrier  225  decreases to a value less than the 0 psig in front of the carrier  225 . This reversal of the ΔP across the carrier  225  creates a force in the direction of the first station  100 , thereby further slowing the carrier  225  as the carrier  225  approaches the second station  105 . When the predetermined time has elapsed, as noted by the timer  250 , the controller  240  deactivates the solenoid valve  170 , thereby opening the first blower-housing port  135  and allowing free flow of air through the conduit  125 , the second conduit  150  and the transport tube  110 . Upon opening of the solenoid valve  170 , the leaf  160  in the check/relief valve  145  is free to open, thereby allowing free flow of air through the conduit port  155 . 
     In order to send the carrier  225  from the second station  105  to the first station  100 , an operator activates the first blower motor  195 A. This activation is accomplished by an operator actuating a second-station switch  255 , which is coupled to the controller  240 . When the second-station switch  255  is actuated, the second-station switch  255  sends a control signal to the controller  240 . The controller  240  receives the control signal from the second-station switch  255  and provides a control signal to the first blower motor  195 A, to thereby activate the first blower motor  195 A. The operation of the first blower motor  195 A causes the bypass valve  200  to move to a position wherein the first blocking member  215 A blocks the first bypass aperture  190 A. A more detailed explanation of the operation of the bypass valve  200  is provided below in conjunction with FIGS. 3A and 3B. The first blower motor  195 A intakes air from the transport tube  110  and exhausts that air through muffler  130  which lowers the pressure in the transport tube  110  and creates a ΔP across the carrier  225  moving it towards the first station  100 . Air propelled by the first blower motor  195 A entering the check/relief valve  145  from the transport tube  110  holds the leaf  160  in the check/relief valve  145  open, thereby allowing free flow of air through the conduit port  155 . Virtually no air flow occurs through the transport tube  110  between the conduit port  155  and the first station  100 , through the first station  100 , or through the second conduit  150 , since the air flow will find the path of least resistance, which is through the conduit port  155 . 
     As the carrier  225  moves through the transport tube  110 , it reaches the portion of the transport tube  110  where the conduit port  155  is located. After the carrier  225  passes the conduit port  155 , the pressure in the transport tube  110  on the first station  100  side of the carrier  225  increases, thereby decreasing and preferably virtually eliminating, the ΔP across the carrier  225 . The carrier  225  free falls into the first station  100 . 
     FIGS. 3A and 3B illustrate the blower assembly  115  used in the pneumatic transmission system of FIG. 2 showing alternate positions of the bypass valve  200  included in the blower assembly  115 . The valve guide  205  of the bypass valve  200  is fixed in position relative to the blower housing  140 . The valve rod  210  is slidably mounted to the valve guide  205  such that it may move between the position shown in FIG.  3 A and the position shown in FIG.  3 B. 
     Assuming a situation where the bypass valve  200  and the valve disk  175  are each in the position shown in FIG. 3B upon activation of the first blower motor  195 A, then air is pulled into the blower housing  140  through the first blower-housing port  135 . As a result, air from the first chamber I of the blower housing  140  is urged into the second chamber II of the blower housing  140  through the first blower motor  195 A. This causes a vacuum at the first bypass aperture  190 A, urging the air from the second chamber II of the blower housing  140  to the first chamber I of the blower housing  140 . This vacuum pulls air in the vicinity of the first blocking member  215 A, causing the valve rod  210  to slide relative to the valve guide  205  such that the bypass valve  200  moves to the position shown in FIG.  3 A. Once the bypass valve  200  has reached the position shown in FIG. 3A, the path through the second bypass aperture  190 B becomes available since it is no longer blocked by the second blocking member  215 B. The second bypass aperture  190 B now provides a path of least resistance compared to passing through the second blower motor  195 B, so air flows from the second chamber II of the blower housing  140  to the third chamber III of the blower housing  140  through the bypass aperture  190 B, then the air exits the blower housing  140  through the second blower-housing port  165 . Once this process of the bypass valve  200  moving from the position shown in FIG. 3B to the position shown in FIG. 3A is complete, as long as the first blower motor  195 A remains activated, the path of air flow through the blower housing  140  will begin at the first blower-housing port  135 , pass through the first blower motor  195 A, then through the second bypass aperture  190 B, then exit the blower housing  140  through the second blower-housing port  165 . Virtually no air flow occurs through the second blower motor  195 B between the second and third chambers II and III of the blower housing  140 , since the air flow will find the path of least resistance, which is through the second bypass aperture  190 B. Also, as long as the first blower motor  195 A remains activated, the bypass valve  200  will remain substantially at the position shown in FIG.  3 A. This is because the force created by the combination of the vacuum pulling the first blocking member  215 A to the first bypass aperture  190 A and the air pushing the first blocking member  215 A towards the first bypass aperture  190 A will be greater than the force created by the air pushing the second blocking member  215 B towards the second bypass aperture  190 B. 
     Assuming a situation where the bypass valve  200  and the valve disk  175  are each in the position shown in FIG. 3A upon activation of the second blower motor  195 B, then air is pulled into the blower housing  140  through the second blower-housing port  165 . As a result, air from the third chamber III of the blower housing  140  is urged into the second chamber II of the blower housing  140  through the second blower motor  195 B. This causes a vacuum at the second bypass aperture  190 B, urging the air from the second chamber II of the blower housing  140  to the third chamber III of the blower housing  140 . This vacuum pulls air in the vicinity of the second blocking member  215 B, causing the valve rod  210  to slide relative to the valve guide  205  such that the bypass valve  200  moves to the position shown in FIG.  3 B. Once the bypass valve  200  has reached the position shown in FIG. 3B, the path through the first bypass aperture  190 A becomes available since it is no longer blocked by the first blocking member  215 A. The first bypass aperture  190 A now provides a path of least resistance compared to passing through the first blower motor  195 A, so air flows from the second chamber II of the blower housing  140  to the first chamber I of the blower housing  140  through the bypass aperture  190 A, then the air exits the blower housing  140  through the first blower-housing port  135 . Once this process of the bypass valve  200  moving from the position shown in FIG. 3A to the position shown in FIG. 3B is complete, as long as the second blower motor  195 B remains activated, the path of air flow through the blower housing  140  will begin at the second blower-housing port  165 , pass through the second blower motor  195 B, then through the first bypass aperture  190 A, then exit the blower housing  140  through the first blower-housing port  135 . Virtually no air flow occurs through the first blower motor  195 A between the second and first chambers II and I of the blower housing  140 , since the air flow will find the path of least resistance, which is through the first bypass aperture  190 A. Also, as long as the second blower motor  195 B remains activated, the bypass valve  200  will remain substantially at the position shown in FIG.  3 B. This is because the force created by the combination of the vacuum pulling the second blocking member  215 B to the second bypass aperture  190 B and the air pushing the second blocking member  215 B towards the second bypass aperture  190 B will be greater than the force created by the air pushing the first blocking member  215 A towards the first bypass aperture  190 A. 
     FIG. 4 illustrates a pneumatic transmission system containing a second embodiment of a blower assembly in accordance with the present invention. This pneumatic transmission system is substantially the same in structure and operation as the first embodiment shown in FIG.  2  and described above, except that the blower assembly  115  has been replaced with a blower assembly  115 ′, which includes an electromechanical bypass valve  200 ′ in place of the bypass valve  200 . Also, a signal path is provided from the controller  240  to the electromechanical bypass valve  200 ′. As stated above, the present invention is not limited to an electrical coupling, or even a physical connection between the controller  240  and its peripherals. 
     As mentioned above, the structure of the pneumatic transmission system shown in FIG. 4 is substantially the same as that of the pneumatic transmission system shown in FIG.  2 . However, the blower assembly  115 ′ in the pneumatic transmission system shown in FIG. 4 includes the option of an electromechanically operated bypass valve, in this case the electromechanical bypass valve  200 ′. The electromechanical bypass valve  200 ′ includes a solenoid  260  having an armature  265  extending therethrough, projecting from opposing ends of the solenoid  260 . The electromechanical bypass valve  200 ′ also includes a first blocking member  215 A fixed to a first end portion of the armature  265  such that, in a first position, the electromechanical bypass valve  200 ′ operates to block the first bypass aperture  190 A with the first blocking member  215 A, substantially preventing air flow through the first bypass aperture  190 A. The electromechanical bypass valve  200 ′ further includes a second blocking member  215 B fixed to a second end portion of the armature  265  such that, in a second position, the electromechanical bypass valve  200 ′ operates to block the second bypass aperture  190 B with the second blocking member  215 B, substantially preventing air flow through the second bypass aperture  190 B. 
     The operation of the pneumatic transmission system shown in FIG. 4 is substantially the same as that of the pneumatic transmission system shown in FIG. 2, except for the differences due to the use of the electromechanical bypass valve  200 ′. In this embodiment, in order to send the carrier  225  from the first station  100  to the second station  105 , the carrier  225  is placed in the transport tube  110 , the door  220  is shut and sealed, and both the second blower motor  195 B and the electromechanical bypass valve  200 ′ are then activated. This can be done by an operator actuating a first-station switch  235 , which is coupled to a controller  240 . The controller  240  is coupled to the first and second blower motors  195 A and  195 B for selective activation of the first and second blower motors  195 A and  195 B, and to the electromechanical bypass valve  200 ′ for activation of the electromechanical bypass valve  200 ′ such that the armature  265  is selectively positioned at one of the first and second positions. When the first-station switch  235  is actuated, the first-station switch  235  sends a control signal to the controller  240 . The controller  240  receives the control signal from the first-station switch  235  and provides a control signal to the second blower motor  195 B, to thereby activate the second blower motor  195 B. The controller  240  also provides a control signal to the electromechanical bypass valve  200 ′ to thereby activate the solenoid  260  such that the armature  265  is moved to the second position as shown in FIG.  4 . Once the armature  265  is in the second position, the second blocking member  215 B will block the second bypass aperture  190 B, substantially preventing air flow through the second bypass aperture  190 B, while at the same time distancing the first blocking member  215 A from the first bypass aperture  190 A, allowing air flow through the first bypass aperture  190 A. 
     In order to send the carrier  225  from the second station  105  to the first station  100 , an operator activates the first blower motor  195 A and the electromechanical bypass valve  200 ′. This activation is accomplished by an operator actuating a second-station switch  255 , which is coupled to the controller  240 . When the second-station switch  255  is actuated, the second-station switch  255  sends a control signal to the controller  240 . The controller  240  receives the control signal from the second-station switch  255  and provides a control signal to the first blower motor  195 A, to thereby activate the first blower motor  195 A. The controller  240  also provides a control signal to the electromechanical bypass valve  200 ′ to thereby activate the solenoid  260  such that the armature  265  is moved to the first position (not shown). Once the armature  265  is in the first position, the first blocking member  215 A will block the first bypass aperture  190 A, substantially preventing air flow through the first bypass aperture  190 A, while at the same time distancing the second blocking member  215 B from the second bypass aperture  190 B, allowing air flow through the second bypass aperture  190 B. 
     While the second embodiment has been described as comprising an electromechanical bypass valve  200 ′ which includes a single solenoid  260  and a single armature  265 , the electromechanical bypass valve  200 ′ is not limited to this configuration. Rather, there are many well-known types of electromechanical devices which could be readily substituted without departing from the spirit and scope of the invention. For example, a pair of solenoids may be mounted back to back such that an armature of each solenoid may be selectively activated by a control signal to block or not block a respective bypass aperture with a respective blocking member. Also, a bypass valve other than the ones described with the embodiments herein may be selected without departing from the spirit and scope of the invention. For example, a suitable bypass valve may be constructed using a hydraulic, pneumatic, electrical or other type of controllable actuating device. 
     Finally, while the blower assembly of the present invention has been shown for use with the pneumatic transmission systems shown in FIGS. 2 and 4, the blower assembly of the present invention is not limited to use with such pneumatic transmission systems. Rather, the blower assembly of the present invention is suitable for use in any type of pneumatic transmission system in which it is desirable to forcibly move air in one or more directions. Moreover, the blower assembly of the present invention is suitable for any other type of application in which it is desirable to forcibly move air in one or more directions. 
     While preferred embodiments of the present invention has been described, with respect to certain preferred aspects, it should be apparent to those skilled in the art that it is not so limited. Various other modifications may be made without departing from the spirit and scope of the invention. It is intended that the following claims be interpreted to embrace all such variations and modifications.