Abstract:
A seed planting unit provides a manifold connecting a vacuum to multiple metering disks. The manifold includes valves to sequentially connect the manifold branches to the seed unit so as to moderate the peak air flow necessary to be handled by the vacuum source reducing horsepower drain and cost of the vacuum source itself.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to seed planters for dispensing individual seeds at a controlled rate into a seed furrow, and specifically to seed planters that employ vacuum systems for metering the seeds. 
   Seed planters dispense seeds at a controlled rate into a seed furrow as a planter is advanced along the ground. In a typical arrangement, a tractor is coupled to tow a tool bar to which is attached, in a parallel spaced part relationship, a plurality of planting units. 
   Each planting unit typically includes a seed hopper holding seeds and communicating with a seed meter for dispensing seeds at a controlled rate as the planting unit moves over the ground. The planting unit may include on its lower surface a furrow opening disk for opening a furrow for the seeds, a furrow closing disk for closing the furrow about the seeds, and a trailing wheel that tamps down the earth about the furrow. 
   The seed metering unit must pick individual seeds from the hopper and deliver them between the furrow opening disk and the furrow closing disk at a controlled rate. One method of accomplishing this task with seeds of different sizes and shapes uses a disk with a plurality of openings that rotates past a seed chamber. A vacuum draws air through the openings in the disk to trap individual seeds within each opening for delivery into a second location for release. 
   The vacuum for the seed metering device may be provided, for example, by a blower driven by an hydraulic motor attached to the hydraulic system of the tractor. The motor is sized to provide a sufficient vacuum pressure at an air flow rate that might be anticipated when each disk for each planting unit is empty of seeds, and therefore under a condition of minimum back resistance to the blower. After seeds begin to fill the holes, a lower flow rate is required. 
   BRIEF SUMMARY OF THE INVENTION 
   Some embodiments include a vacuum manifold for a seed planter comprising a series of seed planting units receiving vacuum to pull seeds into pockets within a metering plate, a vacuum source, a manifold attached to the vacuum source to distribute a vacuum to the series of seed planting units through multiple manifold branches, at least a first valve within a manifold branch and an actuator communicating with the first valve to delay opening of the manifold branch with respect to at least one other manifold branch during initial stages of establishing a vacuum in the manifold. 
   In some cases the actuator is a vacuum sensitive actuator communicating with the manifold to actuate the first valve only after a predetermined vacuum level is achieved in the manifold. In some cases the first actuator is a piston movable within a cylinder. In some cases the manifold further includes a spring biasing the valve closed in an absence of a vacuum applied to the cylinder. 
   In some cases the actuator provides a continuous opening of the valve as a function of the manifold pressure. In some embodiments the actuator includes a timer delaying a predetermined time after starting of the vacuum source to infer the predetermined vacuum level. In some cases the manifold includes a second valve within a second manifold branch coordinating with the first valve to delay opening of a second manifold branch with respect to the opening of the first manifold branch. 
   In some cases the second valve has a second actuator coordinated opening the second valve. In some cases the first and second actuators are pistons within cylinders receiving vacuum lines and wherein the second actuator receives a vacuum line through a pressure switch communicating with a vacuum line of the first actuator, the pressure switch being closed until a predetermined pressure is reached and then opening. In some cases the second valve is driven by the actuator through a linkage connecting the first actuator to the first and second valves. In some cases the linkage is a cam plate rotated by the first actuator and driving cam follower on the first and second valves. 
   Other embodiments include a method of planting seeds comprising the steps of (a) providing a series of seed planting units having a metering plate including a series of pockets for receiving seeds, (b) attaching the seed planting units to a manifold communicating with a vacuum source and having multiple manifold branches connected with different seed planting units and including at least one valve in one manifold passage and (c) controlling the valve to sequentially applying a vacuum source to groups of the seed planting units to draw seeds into the series of pockets upon starting of a planting operation to limit a maximum air flow to the vacuum source. 
   In some cases each group is a single seed planting unit. In some cases the step of sequentially applying the vacuum source to groups of the seed planting units controls the valve according to a vacuum level in the manifold. In some cases the valve closes the manifold passage in an absence of a vacuum in the manifold. In some embodiments the valve provides continuously variable restriction of the manifold passage. In some embodiments the valve closes a predetermined time after starting of the vacuum source to infer the predetermined vacuum level in the manifold. In some embodiments the vacuum is sequentially applied through greater than two manifold passages. 
   In some cases each of the valves is sequenced by variations of vacuum sensed within at least one portion of the manifold. In some cases at least one of the valves is sequenced by a timer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a simplified schematic view of a planting system receiving vacuum lines from a manifold driven by a single vacuum source; 
       FIG. 2  is a perspective view of the vacuum source and manifold of  FIG. 1  showing an actuator for sequencing air flow in two manifold branches; 
       FIG. 3  is an elevational cross-section of the manifold and actuator of  FIG. 1  showing the connection of the actuator to an internal plate valve; 
       FIG. 4  is a simplified representation of the manifold of  FIGS. 2 and 3  showing multiple actuators linked with vacuum lines for sequencing of four manifold branches; and 
       FIG. 5  shows four stages of operation of an alternative embodiment of the application of vacuum to four manifold branches. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to  FIG. 1 , a planting system  10  suitable for use with the present invention may provide for a number of planting units  12   a  through  12   d  arrayed along a toolbar  11  towed by a tractor or the like. 
   Each planting unit  12  may include a seed metering unit  14  including a rotating metering disk  16  driven by a drive  17  (e.g., a motor) having a series of circumferentially displaced orifices  18  that may receive seeds  20  drawn into the orifice by a vacuum applied to the opposite side of metering disk  16 . Metering systems of this type are described in U.S. Pat. No. 6,564,730 assigned to the same assignee as the present invention and hereby incorporated by reference. 
   Each of the seed metering units  14  connects via a vacuum line  22  to a manifold  24  connected with one or more vacuum sources  26 . The vacuum sources  26  provide for a discharge of air through a discharge outlet  28  and an application of a vacuum through an inlet  30  to manifold  24 . Generally, the amount of air discharged from discharge outlet  28 , and thus the capacity of the vacuum source  26 , must be sufficient to create a negative pressure (henceforth vacuum pressure) to draw seeds  20  into the orifices  18  when the orifices are completely empty, for example, at the startup of the planting operation. 
   In the present invention, in order to reduce the peak air flow required of the vacuum sources  26 , a series of valves  32   a  through  32   d  are provided located within corresponding branches  36  of the manifold  24  to control the air flow through individual vacuum lines  22 . The valves  32  are rotating plate valves providing a continuous throttling of air flow as a function of rotation of the plates such as may allow smooth control reducing pressure shocks to the system such as may create control or seed retention problems. 
   Referring now to  FIG. 2 , each vacuum source  26  may be a blower  34  powered by a hydraulic motor or the like (not shown) attached to the toolbar  11  to be easily attached to the planting units  12  through vacuum lines  22  formed of flexible hoses or the like. The vacuum source  26  may have a manifold  24  providing for four manifold branches  36  extending radially from a common center at 90 degree increments. In a first embodiment as shown in  FIG. 2 , two of the manifold branches  36   b  and  36   c  are capped with caps  40 , and two of the manifold branches  36   a  and  36   d  are open to provide vacuum lines  22  to one or more planting units  12 . 
   Referring now also to  FIG. 3 , a first open manifold branch  36   a  in this embodiment may have no valve  32  or that valve  32  may be fixed in an open position. The valve  32  in manifold branch  36   d  may be connected by an external actuator arm  44  to a piston shaft  46  of the vacuum cylinder  48 . The cylinder  48  is attached with respect to manifold branch  36   d  so when actuated, it opens valve  32  in branch  36   d.    
   A vacuum line  50  is connected to the vacuum cylinder  48  to decrease the pressure in a distal portion of the cylinder  48  removed from the piston shaft  46  when vacuum is applied to the vacuum line  50 . This negative pressure draws a piston  52  within the vacuum cylinder toward that distal portion and opens valve  32 . Conversely, loss of the vacuum in line  50  causes a return of the piston  52  toward the valve  32  under the influence of a contained spring  54  closing the valve  32 . The spring  54  provides a system that automatically resets upon loss of vacuum. 
   The vacuum line  50  may be connected to manifold branch  36   a  or other convenient location of the manifold  24  so as to allow the piston  52  to be responsive to a predetermined pressure within the manifold  24  to open valve  32 . Thus, upon initial startup, the pressure in the manifold  24  will be low as seeds are drawn into a metering disk  16  associated with branch  36   a  or multiple metering disks. As those metering disks fill up, the vacuum pressure within manifold  24  decreases causing actuation of the cylinder  48  and opening of valve  32 . At this point, a sufficient number of seeds have blocked the orifices of disks attached to manifold branch  36   a  so that the opening of valve  32  will not unduly decrease the vacuum pressure within the manifold  24 . Note that the operation of cylinder  48  is to gradually open valve  32  as the pressure in manifold  24  decreases so as to bring other planting units  12   a  online as soon as practical as pressure capacity warrants. 
   By sequentially engaging the vacuum lines  22  of each planting unit  14 , the peak airflow of the vacuum source is reduced, reducing the necessary size of the motor or the hydraulic power required or reducing the number or size of blowers. In this approach where vacuum in the manifold is sensed, the system may actively respond to periods of vacuum loss for whatever reason and rapidly reengages the planting units when vacuum is obtained. 
   Referring now to  FIG. 4 , the same approach may be extended to each of the branches  36   a  through  36   d  of an arbitrary manifold  24 , and in this particular example, three additional branches. In this embodiment, manifold branch  36   a  has no valve, but a valve  32  and corresponding vacuum cylinder  48  may be associated with each of the branches  36   b ,  36   c , and  36   d  operating generally as described above with respect to manifold branch  36   d  of  FIG. 3 . Branch  36   a  is connected by a vacuum line  50   b  to vacuum cylinder  48   b  and to a vacuum switch  56   a  associated with manifold branch  36   b  and valve  32   b . Vacuum switch  56   a  is a snap action type valve that opens at a predetermined pressure difference. 
   The remaining orifice of vacuum switch  56   a  connects via vacuum line  50   b  to both vacuum cylinder  48   c  associated with manifold branch  36   c  and valve  32   c  and vacuum switch  56   b.    
   The remaining port of vacuum switch  56   b  in turn connects to vacuum cylinder  48   d  associated with manifold branch  36   d  and valve  32   d.    
   In operation, each of the valves  32   b ,  32   c  and  32   d  are initially closed under the influence of internal springs within cylinders  48   b ,  48   c  and  48   d . As pressure decreases in the manifold  24 , vacuum line  50   a  causes the actuation of vacuum cylinder  48   b  opening valve  32   b . The actuation begins at a pressure lower than that which would trigger vacuum switch  56   a . Once valve  32   b  is opened, the pressure begins to drop again as seeds are drawn into the corresponding holes in metering disk  16  blocking the holes until a pressure sufficient to open vacuum switch  56   a  is reached upon which vacuum cylinder  48   c  begins actuation. Vacuum switch  56   a  has a certain degree of hysteresis to accommodate a slight decrease in pressure at manifold  24  as valve  32   c  is opened. 
   After a period of time with valve  32   c  open, the seed metering disk  16  associated with the branch  36   c  begins to fill with seeds, and the pressure again decreases in manifold  24  until a second threshold is reached at which time vacuum switch  56   b  opens activating vacuum cylinder  48   d  to begin opening valve  32   d.    
   In this way, each of the manifolds and/or associated seed metering units  14  may be sequentially brought online without overwhelming the vacuum source  26 . 
   It will be recognized that vacuum cylinder  48  may alternatively be electric actuators such as solenoids or motors communicating with the manifold  24  via a pressure sensor of well-known type providing an electrical pressure signal that may be used to control the vacuum cylinder  48 . Alternatively, a timer may be used to sequentially activate the valves  32  according to a predetermined time delay which approximates the time required to reach the pressures expected without a direct measurement of those pressures. 
   Referring now to  FIG. 5  in an alternative embodiment, a single actuator  65 , in this case a motor, may be triggered by a timer  63  activated by an electrical signal associated with the starting of the planting system  10  or a vacuum gauge in the manifold  24  (not shown). The actuator  65  may rotate a cam  60  communicating with cam followers  62 , serving in lieu of the actuator arm  44 , where the cam followers  62  are spring biased or gravity biased against an outer surface of the cam  60 . The cam  60  rotates about a center of the manifold  24  and has an outer surface that is a constant radius about the center of the manifold  24 . As the actuator  65  rotates the cam  60  to a position shown by cam  60 ′ the cam follower  62  associated with the valve  32   b  of branch  36   b  moves off of the constant radius cam surface allowing the valve  32  to close. Successive rotations to position shown by cam  60 ″ and  60 ′″ allow each of the valves  32  successively to close. 
   In normal field operation, each of the valves  32  will normally be fully opened. 
   It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims. For example, while  FIGS. 1-5  above show a separate valve  32  associated with each seed meter  12   a - 12   d , in at least some embodiments two, three, four or more seed meters may be downstream of each valve  32 . Here, multiple seed meters would be connected to each port of the fan manifold. 
   In addition to the concepts described above, according to another inventive aspect, the seed meters can be controlled to effectively precharge all of the meters with seed and pressure prior to seeding activity. To this end, referring again to  FIG. 1 , if valves  32   b ,  32   c  and  32   d  are initially closed and valve  32   a  is opened to increase pressure in line  22  attached to meter  12   a , if disc  16  continues to be rotated after seed fills holes  18  and pressure builds up therein and during the period when pressure is being built up in the other lines  22  linked to meters  12   b - 12   d , meter  12   a  will drop seed to soil therebelow which will either be wasted or will result in non-uniform seeding (i.e., the row of seed corresponding to meter  12   a  will be longer than the row corresponding to meter  12   b  which will be longer than the row corresponding to meter  12   c  and so on). 
   To avoid this non-uniform seeding problem, in at least some embodiments, after seed is received in the holes  18  of a first disc and pressure builds up, as the valve (e.g.  32   b ) associated with the second seed meter  12   b  is opened, disc  16  corresponding to first meter  12   a  can be halted. 
   After seed is deposited in second disc holes  18  and pressure builds up, as the valve  32   c  associated with the third seed meter  12   c  is opened, disc  16  corresponding to second meter  12   b  can be halted. This process can be continued until pressure is built up in all lines  22  after which all of the meter discs  16  can be driven to rotate and begin seeding. Here, as all discs are precharged with seed and pressure, seed rows can be started at the same locations and seed is not wasted. This percharging concept is also applicable where multiple (e.g., 4) meters are downstream of each valve  32  where each bank of four meters can be rotated while pressure in lines associated therewith is increased and can be halted while other meters and associated lines are charged.