Abstract:
A pressure control system is configured to precisely tune positive air pressure or vacuum to pneumatic seed meters that are located along a pneumatic metering manifold. The system includes pressure control valves pneumatically located at plural seed meters that adjust the air pressure or vacuum at the seed meters. The system can utilize feedback pressure signals from pressure sensors at each meter to equalize positive air pressure or vacuum at the seed meters to ensure consistent row-to-row seed populations.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    The present invention is directed to vacuum or positive pressure seed meters for a seeding machine. Particularly, the invention is directed to controlling the air pressure applied to seed meters of a seeding machine.  
         BACKGROUND OF THE INVENTION  
         [0002]    Modern seeding machines use plural seed meters spaced apart along a pneumatic manifold corresponding to planting rows. One such seed meter is disclosed, for example, in U.S. Pat. No. 5,170,909 assigned to the assignee of the present invention. Sophisticated seed metering systems for controlling the rate at which seeds are planted use air pressure to control the application of seed to the ground. In some systems, positive air pressure is used. In other systems, negative air pressure in the form of a vacuum is used to meter the seed.  
           [0003]    Positive or negative air pressure is generated by an air pump in the form of a fan. This air pressure from the air pump is directed to a pneumatic manifold. The pneumatic manifold in turn is pneumatically coupled to individual seed meters by hoses.  
           [0004]    The air pressure supplied to different row seed meters is not identical. Such a condition results in uneven seed meter performance, possibly resulting in variations in row-to-row seed population and/or seed spacing along the rows. The positive or negative air pressure is highest at those seed meters pneumatically closest to the source of pressurized air or vacuum.  
           [0005]    The present inventors have recognized the desirability of proving an air pressure seed metering system that compensates for variations in air pressure along the pneumatic manifold to ensure a consistent row-to-row seed population and seed spacing along each row.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention provides a pressure control system that is configured to precisely tune positive air pressure or vacuum to pneumatic seed meters that are located along a pneumatic metering manifold.  
           [0007]    The system includes pressure control valves pneumatically located at plural seed meters that adjust the air pressure or vacuum at the seed meters. The system can utilize feedback pressure signals from pressure sensors at each meter to equalize positive air pressure or vacuum at the seed meters to ensure consistent row-to-row seed populations. Alternatively, the system could utilize seed population measurement as a feedback signal to adjust control valves.  
           [0008]    A seeding machine is provided with a frame having a plurality of pneumatic seed meters. An air pump located on the frame supplies air pressure, positive or negative, depending on the seed meter type, to a pneumatic manifold. The pneumatic manifold in turn is pneumatically coupled to the seed meters by air hoses. Control valves, such as adjustable orifice valves, are pneumatically positioned between the pneumatic manifold and each air connection of the seed meters.  
           [0009]    The pneumatic manifold is provided with radially extending tube stubs that are coupled to air hoses. The controllable pneumatic orifices can be connected to the tube stubs, can be connected at a point along the air hose, or can be connected to the seed meter.  
           [0010]    The adjustable orifice valve of the invention comprises a substantially enclosed housing having a first air connection and a second air connection with a flow pathway therebetween. One or more baffles are arranged within the housing in the pathway between the air connections. An actuator is mounted to the housing and is operable to position the baffle to a controllable degree between the first and second air connections, to restrict flow through the orifice valve. In one embodiment three baffles are used to form an iris which can increase or decrease the orifice opening between the air connections while maintaining orifice concentricity. In another embodiment a single baffle can be used to close off the orifice in the pathway between the air connections in an eccentric manner.  
           [0011]    As an alternative to the separate enclosed housing, the control valve of the invention could be incorporated into the seed meter housing/manifold.  
           [0012]    Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a top view of a row crops planter having a plurality of individual planting units;  
         [0014]    [0014]FIG. 2 is a semi-schematic side view of one planting unit and the pneumatic distribution system;  
         [0015]    [0015]FIG. 3 is a perspective view of an adjustable orifice valve of the present invention;  
         [0016]    [0016]FIG. 4 is a perspective view of the adjustable orifice valve of FIG. 3 with a front cover removed for clarity;  
         [0017]    [0017]FIG. 5 is a perspective view of one of the baffles shown in FIG. 4  
         [0018]    FIGS.  6 A- 6 C are fragmentary plan views of the adjustable orifice of FIG. 3 in progressive stages of closing;  
         [0019]    [0019]FIG. 7 is a perspective view of an adjustable orifice valve according to a second embodiment of the invention with a front cover removed for clarity, but with an actuator shown in position nonetheless;  
         [0020]    FIGS.  8 A- 8 C are fragmentary plan views of the adjustable orifice of FIG. 7 in progressive stages of closing; and  
         [0021]    [0021]FIG. 9 is a schematic, partially sectional view of an alternate embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated.  
         [0023]    [0023]FIG. 1 is a top view of a seeding machine  10 . In the illustrated embodiment, the seeding machine is a row crop planter, however, the present invention could be used on other seeding machines having pneumatic seed meters, including grain drills and air seeders. The planter comprises a frame  12  that can be extended into a working configuration illustrated in FIG. 1 and folded into a transport configuration. A plurality of row crop planting units  20  is mounted to the frame  12 .  
         [0024]    An air pump  40  in the form of a fan creates an air pressure in two air tubes  42  and  43 . The air tube  42  extends between the air pump  40  and the pneumatic manifold  44 . The air tube  43  extends between the air pump  40  and the pneumatic manifold  45 . Each of the pneumatic manifolds  44  and  45  comprises a cylindrical tube that extends along the frame  12 . Each of the pneumatic manifolds  44  and  45  comprises two sections that are coupled together by a flapper coupling  46 . The flapper coupling  46  allows each of the manifolds to be split apart as the planter frame  12  is being folded and to be rejoined when the planter frame is unfolded into its working configuration.  
         [0025]    [0025]FIG. 2 illustrates each of the row crop planting units  20  is provided with a seed hopper  22  that directs seed to a seed meter  24  which meters the seed. The metered seed is directed by a seed tube  26  from the seed meter  24  to a planting furrow formed in the ground by furrow opener  28 . A planting furrow is closed by angled closing wheels  30 . The planting unit may also be provided with a pesticide hopper  32  for carrying pesticides to be applied during the planting process.  
         [0026]    The seed meter  24 , in the illustrated embodiment, is a vacuum meter of the type presently marketed by the assignee of the present application. A vacuum seed meter is disclosed for example in U.S. Pat. No. 5,170,909 herein incorporated by reference. Negative air pressure is used to attract seeds to a seeding disc as it passes through a seed pile or puddle. The seeds remain in contact with the disc until the vacuum is removed and the seeds fall into the seed tube  26 .  
         [0027]    The present invention could also be used with positive pressure systems, wherein a positive air pressure is used to drive the seeds to a seed disc as it revolves through a seed puddle. Removing the positive air pressure releases the seeds from the disc and the released seeds then drop into the seed tube  26 .  
         [0028]    Each of the pneumatic manifolds  44  and  45  are provided with radially extending tube stubs  50  which are coupled to air hoses  52  for directing the air pressure in the pneumatic manifold to the individual seed meters  24 .  
         [0029]    A pressure control valve in the form of an adjustable orifice valve  60  is positioned between the pneumatic manifolds  44  and  45  and an air connection of the row crop planting unit  23 . Each orifice valve  60  comprises a housing  61  having a first air connection in the form of a tube  62  and a second air connection in the form of a tube  63 . The housing  61  includes a front cover  64  fastened to a back plate  65 . The tube  62  is fastened to the front cover  64 . The tube  63  is fastened to the back plate  65 . Within the housing  61 , one or more baffle plates are arranged as described below.  
         [0030]    The first tube  62  is in registry with the second tube  63 . The baffle plate or plates are disposed between the first and second tubes  62 ,  63  to provide an adjustable restriction of airflow between the first and second tubes. An actuator  68  is mounted by fasteners  69  (shown in FIG. 7) onto the cover  64  of the housing  61 . The actuator  68  includes an output shaft  68   a  (shown for example in FIG. 7) which penetrates the housing front cover  64  and which engages one of the baffles. The actuator, depending on an input signal thereto, controls the degree of restriction caused by the baffle or baffles by controllably rotating the baffle or baffles. The actuator is preferably a servomotor, wherein the servomotor can be controlled for precise rotation.  
         [0031]    Since the vacuum pressure is related to the flow rate, and flow rate will change as the flow area changes, changing the baffle location will change the vacuum pressure.  
         [0032]    In the preferred embodiment, the orifice valve  60  is inserted adjacent to, or as part of the meter  24  (see FIG. 9). However, other locations for the orifice valves are possible, such as along the air hose  52 , or at the respective manifold  44 ,  45 .  
         [0033]    Preferably, an orifice valve  60  would be located at each of the seed meters  24 . However, orifice valves  60  could be located only at the seed meters  24  closest to the air tubes  42 ,  43  to restrict the airflow there to more closely match the air pressure to the air pressure at the remaining seed meters  24  farther from the air tubes  42 ,  43 .  
         [0034]    Vacuum pressure can be constantly monitored by pressure sensors P for each row or group of rows. Each sensor can be signal connected to a respective valve  60  to control by feedback the position of the valve and the level of vacuum or positive pressure at the seed meter. Alternately, a controller C, such as a microprocessor, can be signal-connected to all the pressure sensors P. The controller can be signal-connected to the actuators  68  at the orifice valves  60 . The vacuum or positive pressure level at each row is adjusted by the controller C according to feedback from the sensors P and by signal communication to each actuator  68 . For example, where the actuator is a servomotor, the controller, through an appropriate input/output device, can command the servomotor to open the iris slightly by a limited rotation of the servomotor, to increase the vacuum or positive pressure at the particular seed meter  24 , ensuring equal performance of all of the seed meters.  
         [0035]    As an alternate feedback, an optical sensor could be located at each seed meter to detect the number of seeds the meter releases to the ground. Typically, the optical sensor is an infrared light emitting diode (LED) that is used in conjunction with a photocell. The photocell emits a pulse each time the light level from the LED goes below a specified threshold. These pulses correspond to seeds. With this information, and the vehicle travel speed, the rate of seed dispensing at each meter can be sensed and the vacuum at each meter adjusted accordingly by the valve.  
         [0036]    Although orifice valves  60  are utilized in the above-described embodiment, other types of control valves, such as butterfly valves, could be used in place of orifice valves, and are also encompassed by the invention.  
         [0037]    [0037]FIG. 4 illustrates three baffles  82 ,  84 ,  86  that are inter-engaged to form an iris shaped orifice  90  at a center thereof. Each baffle includes a slotted pivot  92 , a cam slot  94  and a pin  96 . Each pin  96  is located to be positioned within a cam slot  94  of an adjacent baffle. Two of the slotted pivots  92  are rotatably received in an opening  102  in the cover  64 . One of the pivots  92  is engaged by the actuator shaft  68   a  (as shown in FIG. 7) of the actuator  68  to be forcibly rotated thereby. Forceful rotation of the pivot  92  causes corresponding mutual rotation of all of the baffles via the pins  96  and cam slots  94 , to either constrict or expand the iris opening  90 . Therefore, rotation of the actuator shaft which is engaged to one of the pivots  92  will constrict the iris opening  90  when rotated in a first direction, and will expand the iris opening  90  when rotated in a second, opposite direction. The back plate  65  further includes threaded openings  106  for receiving fasteners from the cover  64  to fix the plate  65  to the cover  64  to form the enclosed housing  61 .  
         [0038]    [0038]FIG. 5 illustrates a single baffle, such as the baffle  82 . The baffle  82  is offset in two planes which allows for the assembly of the three baffles  82 ,  84 ,  86  in a relatively flat profile.  
         [0039]    As demonstrated in FIGS.  6 A- 6 C an iris-type baffle arrangement can be used to control the open orifice area  90  to conduct flow between the first tube  62  and the second tube  63 . In FIG. 6A, the iris orifice area  90  is completely open allowing full flow between the tubes  62 ,  63 . In FIG. 6B, the iris orifice area  90  is closed to some extent to provide some restriction of flow through the tubes  62 ,  63 . In FIG. 6C, the iris orifice area  90  is further closed to provide an even further increased restriction of flow between the tubes  62 ,  63 .  
         [0040]    [0040]FIG. 7 illustrates a second embodiment wherein the three baffles  82 ,  84 ,  86  of the first embodiment are replaced by a single baffle  120 . The single baffle  120  includes a pivot  92  as previously described. The baffle  120  is substantially flat and curved. The single baffle  120  is rotated by the actuator shaft  68   a  of the actuator  68  in the same manner as in the first embodiment, under control from the controller C as shown in FIG. 2. In this embodiment, an open orifice area  124  is opened and closed to form an eccentric orifice compared to the pathway between the tubes  62 ,  63 .  
         [0041]    As illustrated in FIGS.  8 A- 8 C, wherein the single baffle  120  is used, upon rotation of the baffle  120 , the open orifice area  124  between the tubes  62 ,  63  is progressively constricted. In FIG. 8A, the baffle  120  completely clears and exposes the pathway between the tubes  62 ,  63  for a nearly negligible resistance. In FIG. 8B, a somewhat greater resistance is provided by the position of the baffle  120 . In FIG. 8C, a further flow resistance is provided by a more constricted opening  124 , caused by a further rotation of the baffle  120 .  
         [0042]    [0042]FIG. 9 illustrates an alternate embodiment wherein the valve housing  60 ′ is combined with the seed meter  24 ′ forming one housing  150 . The seed meter  24 ′ can be as described in U.S. Pat. No. 5,170,909 herein incorporated by reference. An air assisted seed distribution device, such as a seed disk  154  distributes seed  152 . The dist  154  and the valve baffle  120  share the common housing  150 . The suction first tube  62  is used but the second tube  64  is not necessary. The single baffle  120  is shown as an example, mounted to an intermediate plate  65 ′. The iris type baffle plate arrangement of FIG. 4, or another type of control valve could be used in the housing of FIG. 9 as well.  
         [0043]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.