Patent Publication Number: US-11654441-B2

Title: Temperature-controlled tramp metal separation assembly

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to devices for removing tramp metals from a stream of raw materials, and more particularly to a tramp metal separation assembly that can automatically control and adjust the operating temperature thereof. 
     2. Description of the Related Art 
     A typical prior art device for removing tramp metals from a stream of raw materials is disclosed in U.S. Pat. No. 8,132,674. This tramp metal separation device, in brief, uses a number of actuators for moving a magnet assembly in and out of a housing provided with a wiper plate so that the device can remove continuously the tramp metals captured on the magnet assembly. A primary disadvantage of this device is that the continuous friction between the magnet assembly and the wiper plate will increase the operating temperature of the magnet assembly such that the magnetic force of the magnet assembly will be significantly reduced. 
     A prior art magnetic separator for removing tramp metals from a stream of raw materials is disclosed in Chinese Utility Model Pat. 204,602,393. The magnetic separator includes a plurality of magnetic sets mounted on a frame. Each magnetic set is composed of a magnetic rod and two shafts connected respectively to each end of the magnetic rod. The magnetic separator further includes a sleeve tube sleeved outside the magnetic rod in a way that the sleeve tube is moveable between the magnetic rod and the shaft for capturing and discharging the tramp metals of raw materials. Since the sleeve tube of the magnetic separator moves back and forth on the surface of the magnetic rod and the shaft, the operating temperature of the magnetic separator will also increase due to friction, resulting in a decrease in the magnetic force of each magnetic rod. 
     Thus, it is need to configure a tramp metal separation assembly while the tramp metal separating process is operated efficiently, automatically and continuously, the operating temperature can be maintained at an acceptable level. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages in the related art in a temperature-controlled tramp metal separation assembly comprising a core rod and a magnetic set. The core rod is made of non-magnetic materials and includes a longitudinal axis, a chamber, a first end with at least an air inlet, a second end with at least an air outlet. The magnetic set includes a plurality of magnetic members and a plurality of spacers made of a material having a high magnetic permeability or a high saturation magnetization. Each of the spacers is disposed between the two adjacent magnetic members. The magnetic set is nested in the chamber along the longitudinal axis in way that an air path is formed therein so that an external cooling air flow can be introduced from the air inlet, and then discharged from the air outlet via the air path. Thus, the present invention provides the advantage of the operating temperature of the tramp metal separating process being maintained at an acceptable level, preventing the magnetic force of the magnet set from being reduced. 
     In a preferred embodiment, the chamber of the core rod has a first part and a second part. The magnetic set is nested in the second part to form a magnetic section. The first part forms a non-magnetic section. 
     The present invention also provides for the temperature-controlled tramp metal separation assembly further comprising a sleeve tube made of non-magnetic materials and having a length less than that of the core rod. The sleeve tube is sleeved outside the core rod in a way that it is moveable to and fro along the longitudinal axis of the core rod and between a first position, wherein the sleeve tube corresponds to the magnetic section to capture tramp metals of the raw materials, and a second position, wherein the sleeve tube corresponds to the non-magnetic section to discharge tramp metals captured thereon. 
     In another preferred embodiment, the temperature-controlled tramp metal separation assembly further comprises a housing and a cooling air transmitting unit. The housing includes a first discharging area, a second discharging area and a feeding area between the first discharging area and the second discharging area. The sleeve tube includes a first portion, a second portion, a longitudinal length less than the longitudinal length of the core rod and an axial hole with an inner diameter larger than the outer diameter of the core rod. The chamber of the core rod has a first part, a second part and a third part. The first part forms a first non-magnetic section, the second part forms a magnetic section by nesting the magnetic set, and the third part forms a second non-magnetic section. The core rod is mounted on the housing in a way that the first and second non-magnetic sections correspond respectively to the first and second discharging areas and the magnetic section corresponds to the feeding area. The cooling air transmitting unit is coupled with the core rod in a way that an external cooling air flow is to introduced from the air inlet, and then discharged from the air outlet via the air path. 
     In a further preferred embodiment, the housing includes a front wall, a rear wall, a first side wall, a second side wall, a first inner plate and a second inner plate. The front and rear walls combine with the first and second side walls to define a receiving space within the housing. The first inner plate and the second inner plate are respectively disposed between the first side wall and the second side wall to divide the space into the first discharging area, the second discharging area and the feeding area. The core rod is adapted to pass through the first inner plate and the second inner plate and secures respectively each of ends thereof on the front and rear walls. The sleeve tube is also adapted to pass through the first inner plate and the second inner plate in a way that it is moveable to and fro between the first and second positions. The temperature-controlled tramp metal separation assembly further comprises a temperature sensor mounted on a part of the first side wall located in the feeding area of the housing and coupled with the cooling air transmitting unit in a way that when the operating temperature of the housing is equal to or greater than a first predetermined temperature, the temperature sensor will produce a first signal to actuate the air introducing device for introducing external air into the air path, and when the operating temperature of the housing is equal to or lower than a second predetermined temperature, the temperature sensor will produce a second signal to stop the air introducing device from introducing external air to the air path. 
     In a further preferred embodiment, the temperature-controlled tramp metal separation assembly further comprises a plurality of the core rods and a plurality of the sleeve tubes. The core rods and the sleeve tubes are divided into a plurality of groups. Each of the groups is arranged in a way that each of the core rods and the sleeve tubes thereof is parallel to each other in a horizontal plane. Each of the horizontal planes is spaced apart such that the core rods and the sleeve tubes are provided in a staggered configuration to ensure contact of the raw materials with the first and second portions of the sleeve tubes. The cooling air transmitting unit includes an air input member connected with external cooling air suppliers, an air diverter having a plurality of output ends connected respectively to the air inlet of each of the core rods, and a controlling member operatively connected to the air input member and the air diverter respectively. 
     In a further preferred embodiment, the temperature-controlled tramp metal separation assembly further comprises a first driving plate, a second driving plate and a linear actuator. The first driving plate is fixedly connected to a first end of each of the sleeve tubes and disposed in the first discharging area. The second driving plate is fixedly connected to a second end of each of the sleeve tubes and disposed in the second discharging area. Each of the driving plates is configured to be moveable along the core rod. And the linear actuator is connected with one of the driving plates for actuating the sleeve tubes to move back and forth between the first position and the second position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above, as well as other advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which: 
         FIG.  1    is a longitudinal sectional view of a temperature-controlled tramp metal separation assembly according to a first preferred embodiment of the present invention; 
         FIG.  2    is a longitudinal sectional view of a temperature-controlled tramp metal separation assembly according to a second preferred embodiment of the present invention; 
         FIG.  3    is a perspective view of a temperature-controlled tramp metal separation assembly according to a third preferred embodiment of the present invention; 
         FIG.  4    is a top side view of the embodiment of the present invention shown in  FIG.  3   ; 
         FIG.  5    is a longitudinal sectional view of a core rod of the embodiment of the present invention shown in  FIG.  3   ; 
         FIG.  6    is a longitudinal sectional view of a sleeve tube of the embodiment of the present invention shown in  FIG.  3   ; 
         FIG.  7    is an exploded view of the core rod and the sleeve tube of the embodiment of the present invention shown in  FIG.  3   , showing that the sleeve tube is sleeved outside the core rod; 
         FIG.  8    is a perspective view in partial portion of the embodiment of the present invention shown in  FIG.  3   ; 
         FIG.  9    is a lateral side view showing a part of  FIG.  8   , where the sleeve tube is in a first position; 
         FIG.  10    is a lateral side view showing a part of  FIG.  8   , where the sleeve tube is in a second position; 
         FIG.  11    is a longitudinal sectional view taken along the direction  11 - 11  of  FIG.  9   ; 
         FIG.  12    is a longitudinal sectional view of a temperature-controlled tramp metal separation assembly according to a fourth preferred embodiment of the present invention; and 
         FIG.  13    is a cross-sectional view taken along the direction  13 - 13  of  FIG.  12   . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring firstly to  FIG.  1   , it shows a temperature-controlled tramp metal separation assembly  10  configured according to a first preferred embodiment of the present invention. The temperature-controlled tramp metal separation assembly  10  generally includes a core rod  12  and a magnetic set  14 . The core rod  12  is made of non-magnetic materials, such as stainless steel, titanium alloy, copper alloy or aluminum alloy, etc. The core rod  12  includes a longitudinal axis X-X′, a chamber  120 , a first closed end  122  with at least an air inlet  124 , a second closed end  126  with at least an air outlet  128 . The magnetic set  14  includes a plurality of magnetic members  140  and a plurality of spacers  142 . In this embodiment, the magnetic set  14  has five magnetic members  140  made of NdFeB magnets and four spacers  142  made of high magnetic permeability or high saturation magnetization materials such as pure iron, low carbon steel or iron-cobalt alloy. Each of the spacers  142  is respectively disposed between the two adjacent magnetic members  140 . 
     The magnetic set  14  is nested in the chamber  120  along the longitudinal axis X-X′ in way that an air path  16  is formed therein. In this embodiment, each of the magnetic members  140  includes a first bore  160  and each of the spacers  142  includes a second bore  162  coaxial with the first bore  160  so that a part of the air path  16  is formed thereby. In this way, as shown in the direction of the arrow in  FIG.  1   , an external cooling air flow is introduced by a cooling air transmitting unit  18  from the air inlet  124 , then passes through the air path  16 , and finally is discharged from the air outlet  128  so that, during operation, the operating temperature of the temperature-controlled tramp metal separation assembly  10  can be reduced. 
     Next, referring to  FIG.  2   , it shows a temperature-controlled tramp metal separation assembly  20  configured according to a second preferred embodiment of the present invention. The temperature-controlled tramp metal separation assembly  20  includes a core rod  22 , a magnetic set  24 , a sleeve tube  26  and a non-magnetic inner tube  28 . The core rod  22  is also made of non-magnetic materials and includes a longitudinal axis Y-Y′, a chamber  220 , a first closed end  222  with at least an air inlet  226 , a second closed end  224  with at least an air outlet  228 . The chamber  220  has a first part  230  and a second part  232 . The magnetic set  24  also includes a plurality of magnetic members  240  and a plurality of spacers  242 . Each of the spacers  242  is respectively disposed between the two adjacent magnetic members  240 . The first part  230  of the chamber  220  is adapted to be a non-magnetic section  202 . The second part  232  of the chamber  220  is adapted to be a magnetic section  204  by nesting the magnetic set  24  therein. Each of the magnetic members  240  includes a first through hole  270  and each of the spacers  242  includes a second through hole  272  coaxial with the first through hole  270 . The sleeve tube  26  is also made of non-magnetic materials and has a length d 1  less than the length d 2  of the core rod  22 . In this embodiment, d 1  is about one-half of d 2 . The sleeve tube  26  is sleeved outside the core rod  22  in a way that it is moveable to and fro along the longitudinal axis Y-Y′ of the core rod  22  and between a first position, wherein the sleeve tube  26  corresponds to the magnetic section  204  to capture tramp metals of the raw materials, and a second position, wherein the sleeve tube  26  corresponds to the non-magnetic section  202  to discharge tramp metals captured thereon. The non-magnetic inner tube  28  is disposed within the first part  230  of the chamber  220  and abuts against one end of the magnetic set  24  so that the strength of the core rod  22  can be reinforced and the magnetic set  24  can be firmly arranged in the second part  232  of the chamber  220 . In addition, the temperature-controlled tramp metal separation assembly  20  further includes an air path  27  composed of the first through hole  270 , the second through hole  272  and a hollow interior  280  of the non-magnetic inner tube  28 . In this way, an external cooling air flow similarly is introduced by a cooling air transmitting unit  29  from the air inlet  226 , then passes through the air path  27 , and finally is discharged from the air outlet  228  so that, during operation, the operating temperature of the temperature-controlled tramp metal separation assembly  20  can be reduced. 
     Referring now to  FIGS.  3 - 11   , it shows a temperature-controlled tramp metal separation assembly  30  configured according to a third preferred embodiment of the present invention. The temperature-controlled tramp metal separation assembly  30  comprises a housing  40 , a plurality of core rods  60 , a plurality of magnetic sets  70 , a plurality of sleeve tubes  90 , a control means  200 , a cooling air transmitting unit  300 , a temperature sensor  400  and a pair of linear actuators  500 . 
     The housing  40  comprises a front wall  42 , a rear wall  44 , a first side wall  46  and a second side wall  48 . The front and rear walls  42 ,  44  combine with the first and second side walls  46 ,  48  to define a generally elongate receiving space  50  within the housing  40 . The housing  40  further comprises a first inner plate  52  and a second inner plate  54 . The first inner plate  52  and the second inner plate  54  are respectively disposed between the first side wall  46  and the second side wall  48  to divide the space  50  into a first discharging area  57 , a second discharging area  58  and a feeding area  56  between the first discharging area  57  and the second discharging area  58 . The feeding area  56  has a feeding inlet  560  into which a raw material containing tramp metals is introduced and a feeding outlet  562  from which the raw material is discharged. The first and second discharging areas  57 ,  58  respectively have a first discharging outlet  570  and a second discharging outlet  580  disposed in the bottom side thereof. 
     The core rod  60 , as shown in  FIG.  5   , is also made of non-magnetic materials and includes a first longitudinal axis Z-Z′, an axial extending chamber  62 , a first closed end  63  with an air inlet  630  and a second closed end  64  with an air outlet  640 . The chamber  62  sequentially divides into a first part  620 , a second part  622  and a third part  624 . In this embodiment, each part has approximately the same length. The second part  622  forms a magnetic section  702  by being filled with the magnetic set  70 . The first part  620  and the third part  624  respectively form a first non-magnetic section  704  and a second non-magnetic section  706 . Each of the magnetic sets  70 , in this embodiment, includes five magnetic members  72  made of NdFeB magnets, and four spacers  74  made of high magnetic permeability or high saturation magnetization materials such as pure iron, low carbon steel or iron-cobalt alloy. Each of the spacers  74  is respectively disposed between the two adjacent magnetic members  72 . Each of the magnetic members  72  includes a third through hole  720  and each of the spacers  74  includes a fourth through hole  740  coaxial with the third through hole  720 . 
     The temperature-controlled tramp metal separation assembly  30  further comprises a first non-magnetic inner tube  100  and a second non-magnetic inner tube  102 . The first non-magnetic inner tube  100  is disposed within the first part  620  of the chamber  62  and abuts against a first side of the magnetic set  70 , and the second non-magnetic inner tube  102  is disposed within the third part  624  of the chamber  62  and abuts against a second side of the magnetic set  70 . The first and second non-magnetic inner tubes  100 ,  102  are not only used to reinforce the strength of the core rod  60 , but also used to abut on both sides of the magnetic set  70  so that the magnetic set  70  can be firmly arranged in the second part  622  of the chamber interior  62 . 
     The sleeve tube  90 , as shown in  FIG.  6   , is also made of non-magnetic materials and includes a first portion  902 , a second portion  904 , a longitudinal length d 1 , and an axial hole  903  with an inner diameter larger than the outer diameter of the core rod  60 . The first portion  902  has the same length as the second portion  904 . The longitudinal length d 1  of the sleeve tube  90  is approximately equal to the sum of the length d 2  of the magnetic section  702  and the length d 3  of the first non-magnetic section  704  or the second non-magnetic section  706 . 
     In this embodiment, the temperature-controlled tramp metal separation assembly  30  further includes an air path  32  composed of a first hollow interior  104  of the first non-magnetic inner tube  100  which is a first portion of the air path  32 , the third through hole  720  and the fourth through hole  740  of the magnetic set  70  which are a second portion of the air path  32  and a second hollow interior  106  of the second non-magnetic inner tube  102  which is a third portion of the air path  32 . In this way, an external cooling air flow can be introduced by the cooling air transmitting unit  300  from the air inlet  630 , then passes through the air path  32 , and finally is discharged from the air outlet  640  so that, during operation, the operating temperature of the temperature-controlled tramp metal separation assembly  30  can be reduced. 
     As shown in  FIGS.  8 - 11   , in this embodiment, the first inner plate  52  has a plurality of first bores  520  and the second inner plate  54  has a plurality of second bores  540 . The first bores  520  and the second bores  540  are coaxial and have the same diameter. In combination, the core rod  60  passes through the first bore  520  and the second bore  540  and secures each of the closed ends  63 ,  64  thereof on each of the front and rear walls  42 ,  44  of the housing  40  in a way that the first non-magnetic section  704  and the second non-magnetic section  706  correspond respectively to the first and second discharging area  57 ,  58 , and the magnetic section  702  corresponds to the feeding area  56 . In this embodiment, each of the closed ends  63 ,  64  is respectively secured on the front and rear walls  42 ,  44  by bolts (not shown in the drawings). 
     The sleeve tube  90  is sleeved outside the core rod  60  by the axial hole  903  thereof and also extends through the first bore  520  and the second bore  540  in a way that it is moveable along the first longitudinal axis Z-Z′ of the core rod  60  and between a first position, as shown in  FIG.  9   , wherein the first portion  902  corresponds to the magnetic section  702  and the second portion  904  corresponds to the second non-magnetic section  706 , and a second position, as shown in  FIG.  10   , wherein the first portion  902  corresponds to the first non-magnetic section  704  and the second portion  904  corresponds to the magnetic section  702 . In this embodiment, the periphery of the first bore  520  and the second bore  540  respectively are disposed a first bushing  522 ,  542  thereon so that the sleeve tube  90  can move smoothly between the first position and the second position. 
     In addition, in this embodiment, as shown in  FIG.  6   , the sleeve tube  90  includes a convex ring  92  disposed between the first portion  902  and the second portion  904  and a plurality of flanges  94  for dividing the surface of the sleeve tube  90  into a plurality of receiving regions  96 . The width and the outer diameter of each of the flanges  94  are less than that of the convex ring  92  so that when the first portion  902  or the second portion  904  of the sleeve tube  90  corresponds to the magnetic section  702  of the core rod  60 , each of the receiving regions  96  can evenly capture tramp metals, and during reciprocating movement, the tramp metals captured thereon will not be scraped off by the inner plates  52 ,  54 . Furthermore, each end of the sleeve tube  90  is respectively sleeved with a second bushing  906 ,  908  for maintaining the core rod  60  located at the center of the axial hole  903  and reducing the friction between the sleeve tube  90  and the core rod  60 . 
     In this embodiment, as shown in  FIGS.  3 ,  4  and  8   , the temperature-controlled tramp metal separation assembly  30  includes seven core rods  60 , which are divided into a first group and a second group. The first group has four core rods  60  being secured between the front and rear walls  42 ,  44  in a way that the four core rods  60  are parallel to each other and in a first horizontal plane. The second group has three core rods  60  being also secured between the front and rear walls  42 ,  24  in a way that the three core rods  60  are parallel to each other and in a second plane horizontal spaced apart the first horizontal plane. All of the core rods  60  are provided in a staggered configuration to ensure contact of the raw materials with the magnetic section  702  of each of the core rods  60 . The tramp metal separation assembly  30  also includes seven sleeve tubes  90 , each of which is combined with each of the core rods  60  respectively as the way mentioned above. When each of the sleeve tubes  90  is located at the first position, as shown in  FIG.  9   , the first portion  902  corresponds to the feeding area  56  such that each of the receiving regions  96  will capture the tramp metals of the raw materials, and the second portion  904  corresponds to the second discharging area  58  such that the tramp metals captured on each of the receiving regions  96  will automatically leave therefrom and fall to the second discharging outlet  580 . When each of the sleeve tubes  90  is located at the second position, as shown in  FIG.  10   , the second portion  904  corresponds to the feeding area  56  such that each of the receiving regions  96  thereof will capture the tramp metals of the raw materials, and the first portion  902  corresponds to the first discharging area  57  such that the tramp metals captured on each of the receiving regions  96  will automatically leave therefrom and fall to the first discharging outlet  570 . Thereby, when the sleeve tubes  90  reciprocally move between the first and second positions, the tramp metal separation assembly  30  can automatically and continuously remove the tramp metals from the raw materials. 
     In this embodiment, the tramp metal separation assembly  30  may further comprise a first driving plate  80  fixedly connected to the first end of each of the sleeve tubes  90  and disposed in the first discharging area  57 . The first driving plate  80  has a plurality of third bores  801  for being passed through by the core rods  60 , and a second driving plate  82  fixedly connected to the second end of each of the sleeve tubes  90  and disposed in the second discharging area  58 , wherein the second driving plate  82  has a plurality of fourth bores  821  for being passed through by the core rods  60 . 
     In this embodiment, as shown in  FIGS.  3  and  4   , the cooling air transmitting unit  300  includes an air introducing member  302 , an air diverter  304  and a controlling member  306 . The air introducing member  302  is connected with an external cooling air supplier (not shown in the figures). The air diverter  304  has a plurality of output ends connected respectively to the air inlet  630  of each of the core rods  60  for introducing external air into the air path  32 . The controlling member  306  is operatively connected to the air introducing member  302  and the air diverter  304  respectively to control the amount and period of the external cooling air introduced. The temperature sensor  400  may be a temperature probe or other similar component which is mounted on a part of one of the side walls  46 ,  48  located in the feeding area  56  of the housing  40  and coupled with the cooling air transmitting unit  300  in a way that when the operating temperature of the housing  40  is equal to or greater than a first predetermined temperature, the temperature sensor  400  will produce a first signal to actuate the cooling air transmitting unit  300  for introducing external cooling air flow into the air path  32 , and when the operating temperature of the housing is equal to or lower than a second predetermined temperature, the temperature sensor  400  will produce a second signal to stop the cooling air transmitting unit  300  from introducing external cooling air flow to the air path  32 . The first and second predetermined temperatures are set according to the materials of magnetic members  72 . For example, when each of the magnetic members  72  is made of NdFeB magnets, the first predetermined temperature may be set between 40° C. and 110° C., and the second predetermined temperature may be relatively set between 30° C. and 100° C. And when the first predetermined temperature is set at 40° C., the second predetermined temperature is relatively set at 30° C. 
     In this embodiment, each of the linear actuators  500  is respectively disposed on the housing  40  and connected with one of the driving plates  80 ,  82  or both for actuating the sleeve tubes  90  to move back and forth between the first position and the second position. In this embodiment, each of the linear actuators  500  may be a pneumatic linear actuator that is controlled by a solenoid-operated pneumatic valve assembly, as is well known in the art. Each of the pneumatic linear actuators  500  has a piston  502  coupled to one of the driving plates  80 ,  82  so that all of the sleeve tubes  90  can be actuated at the same time to move reciprocally between the first and second positions. 
     In this embodiment, the tramp metal separation assembly  30  further comprises a pair of guiding rods  84  disposed respectively on each of the side walls  46 ,  48  of the housing  40 . Each of the guiding rods  84  has a second longitudinal axis G-G′ parallel to the first longitudinal axis Z-Z′ of the core rod  60  and passes through a first guiding openings  802  disposed on the first driving plate  80  and a second guiding openings  822  disposed on the second driving plate  82  for guiding the back and forth movement the first and second driving plates  80 ,  82 . The periphery of each of the first and second guiding openings  802 ,  822  is disposed with a third bushing  86  so that the first and second driving plates  80 ,  82  can move smoothly on each of the guiding rods  84 . 
     Furthermore, referring to  FIGS.  12  and  13   , it shows a temperature-controlled tramp metal separation assembly  98  configured according to a fourth preferred embodiment of the present invention. The temperature-controlled tramp metal separation assembly  98  similarly comprises a core rod  980  and a magnetic set  990 . The core rod  980  is also made of non-magnetic materials and includes a first flat surface  981 , a second flat surface  982 , an arc-shaped surface  983 , a chamber  984 , a first closed end  985  with at least an air inlet  987 , a second closed end  986  with at least an air outlet  988 . The first flat surface  981  combines with the second flat surface  982  to form an upper portion of the chamber  984  with an included angle θ less than 90 degrees. The arc-shaped surface  983  combines with the first flat surface  981  and second flat surface  982  to form an arc-shaped lower portion of the chamber  984 . In this embodiment, the included angle θ is 63 degrees so that the chamber  984  can be raindrop-shaped. The magnetic set  990  also include a plurality of magnetic members  992 , and a plurality of spacers  994  made of a material having a high magnetic permeability or a high saturation magnetization. Each of the magnetic members  992  and each of the spacers  994  have a circular-shaped cross section and are nested in the lower portion of the chamber  984  in a way that a part of the upper portion of the chamber  984  forms an air path  996  so that an external cooling air flow can be introduced from the air inlet  987 , and then discharged from the air outlet  988  via the air path  996 .