Abstract:
A sealing gasket made of a resilient rubber material or rubber-like material. The sealing gasket is formed as a rotationally symmetric body with a substantially constant cross-sectional profile. The cross-sectional profile includes: a first sealing part located furthest away from a center of rotation of the body and a second sealing part located radially inside the first sealing part, as viewed in the radial direction. An open space is defined by the first and second sealing parts. The second sealing part essentially curves through an angle away from the center of rotation. A seed housing can include such a seal and a seeder can include such a seed housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/003,633 filed Oct. 22, 2013, which is a National Phase of PCT/SE2012/050261 filed Mar. 8, 2012, and claims priority to Swedish Patent Application No. 1150208-5 filed Mar. 9, 2011. The entire contents of each of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present document relates to a sealing gasket for a seed housing of a seeder. The document further concerns a seed housing comprising such a sealing gasket and a seeder comprising such a seed housing. 
         [0003]    The seed housing is particularly suited for sowing seeds to obtain a predetermined number of plants per unit of length, and more specifically for use in a precision seeder of the kind that utilizes an excess air pressure to feed seeds from the seed distributing device to a seed outlet. 
       BACKGROUND ART 
       [0004]    When sowing crops such as maize, sunflowers and soya beans, it is desirable to plant, in each row, single seeds at a predetermined distance from each other. In order to achieve this, a so-called precision seeder, or “planter”, can be used. A precision seeder can comprise a seed hopper, a seed distributing device, a seed feeding tube, a seed furrow opener, a seed knife, a press wheel and a seed furrow covering means. 
         [0005]    An example of a seed distributing device for a precision seeder is disclosed in U.S. Pat. No. 4,047,638. This precision seeder has what is generally referred to as a singulating disc, i.e. a disc that rotates in a cavity where, on one side of the disc, there is an excess pressure and on the other there is a normal pressure. On the excess-pressure side, seeds are supplied from a seed hopper, so that the lower portion of the disc moves through a bulk quantity of seeds. By providing the disc with a number of perforations or holes, through which only air and not seeds is able to pass, the seeds will be “sucked” tight to the holes and lifted out of the bulk quantity of seeds. In another portion of the cavity, the hole can be temporarily obstructed on the normal-pressure side, thus causing the seed to fall by gravity from the disc and into a seed feeding tube through which it is conveyed to the seed knife. 
         [0006]    It is desirable to position the singulating disc inside a seed housing so as to protect it from external damage. 
         [0007]    To optimize the ability of the singulating disc to single out and retain seeds, it is desirable to establish a definite and stable pressure difference between the excess-pressure side of the singulating disc and its normal-pressure side, given an existing air flow and pressure. 
         [0008]    To permit the use of one and the same seeder for several different types of crop, simple switching between different singulating discs is desirable, so that crop of different seed size can be sowed and/or seeds can be planted at different distances. 
         [0009]    Thus, a number of challenges remain as regards the designing of a seed housing for a precision seeder. 
       SUMMARY OF THE INVENTION 
       [0010]    An object of the present invention is to provide an improved design of a seed housing for an excess air pressure driven precision seeder. 
         [0011]    A particular object is to provide a seed housing, in which the singulating disc is arranged so as to be well protected and yet is easily replaceable while ensuring a stable pressure difference between the excess-pressure side and the normal-pressure side. 
         [0012]    The invention is defined by the appended independent claims. Embodiments of the invention will be apparent from the dependent claims and from the following description and the appended drawings. 
         [0013]    According to a first aspect, there is provided a sealing gasket substantially made of a resilient rubber material or rubber-like material. The sealing gasket is formed as a rotationally symmetric body with a substantially constant cross-sectional profile, the cross-sectional profile having a first sealing part, located furthest away from a centre of rotation of the body, and a second sealing part, located radially inside said first sealing part, as viewed in the radial direction. An open space is defined by the first and second sealing parts. The second sealing part essentially curves through an angle away from the centre of rotation. 
         [0014]    Thus, a sealing gasket is provided whose sealing capacity is improved when it is being subjected to an excess pressure in the inner space defined by the sealing parts. 
         [0015]    The second sealing part can be in formed as a sealing lip with a free end, which preferably can have a portion of thicker material. 
         [0016]    The portion of thicker material can contribute to reinforcing the gasket and preventing it from being unintentionally deformed. 
         [0017]    The sealing gasket can have a base portion and the second sealing part, as viewed in the axial direction, can extend further away from the base portion than the first sealing part. 
         [0018]    In this way, sealing between a surface and two surfaces located at different distances can be provided by one and the same sealing gasket. 
         [0019]    The second sealing part can be joined to an end portion of the base portion by way of a rounded portion. The base portion can be substantially plane. 
         [0020]    The space can have an opening and can taper towards the opening. 
         [0021]    The first sealing part can essentially curve through an angle towards the centre of rotation. 
         [0022]    The first sealing part can be formed as a sealing lip with a free end, which can have a portion of thicker material. 
         [0023]    The first sealing part can be joined to an end portion of the base portion, preferably by way of a rounded portion. 
         [0024]    A material thickness of at least part of the base portion and at least part of at least one of said sealing parts can be substantially constant. 
         [0025]    The first sealing part can be in the form of a compressible seal. 
         [0026]    The compressible seal can have a substantially closed and hollow portion. 
         [0027]    Alternatively, the compressible seal can have at least one ridge, but also at least two ridges and an intermediate groove. 
         [0028]    The second sealing part can have a wear protection, which can be formed integrally with the second sealing part. 
         [0029]    The sealing gasket can further comprise an attachment portion, the sealing parts extending from a first side of the main plane and the attachment portion extending from a second side of the main plane. 
         [0030]    The attachment portion can comprise at least two tongues, which extend from the base portion and which can, but need not, be separated by a groove. 
         [0031]    At least one of the tongues can have a locking lug. As a result, its locking action can be improved. 
         [0032]    According to a second aspect, there is provided a seed housing for a seeder, which seed housing is arranged to feed seeds by means of an excess air pressure. The seed housing has first and second seed housing parts, which are adapted to be joined together for forming the seed housing, a singulating disc, which is movably arranged in the seed housing, and a sealing gasket, which is adapted to provide a seal between the seed housing parts as well as between one of the seed housing parts and the singulating disc. 
         [0033]    The sealing gasket can be a sealing gasket according to that which has been described above. 
         [0034]    The first sealing part can be arranged to provide a seal between the seed housing parts and the second sealing part can be arranged to provide a seal between one of the seed housing parts and the singulating disc. 
         [0035]    One of the seed housing parts can have a groove, in which the attachment portion of the sealing gasket is insertable. 
         [0036]    The seed housing parts can include a fixedly mountable base unit and a lid that is removably attachable to the base unit, the sealing gasket being retainable in the lid. 
         [0037]    The sealing gasket can be arranged on a normal-pressure side of the singulating disc. 
         [0038]    According to a third aspect, there is provided a seeder comprising a seed housing according to that which has been described above. 
         [0039]    According to a fourth aspect, use of a sealing gasket according to that which is described above is provided for sealing a seed housing of a seeder. 
         [0040]    The sealing gasket can simultaneously seal between first and second parts of the seed housing and between a part of the seed housing and a singulating disc that is movable relative to the seed housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]      FIG. 1  shows a precision seeder  1  as viewed obliquely from behind. 
           [0042]      FIG. 2  shows a row unit  5   a - 5   h  of the precision seeder in  FIG. 1 . 
           [0043]      FIG. 3  shows a seed housing  53  of the row unit  5   a - 5   h  in  FIG. 2 , as viewed from the front. 
           [0044]      FIG. 4  shows the seed housing  53  in  FIG. 3 , as viewed from behind. 
           [0045]      FIG. 5  is a sectional view of the seed housing  53  in  FIGS. 3 and 4 . 
           [0046]      FIG. 6  shows a detail of the sectional view of  FIG. 5 . 
           [0047]      FIG. 7  shows the inside of a lid  532  for the seed housing of  FIGS. 3-5 . 
           [0048]      FIGS. 8   a - 8   c  show a sealing gasket  540  for the seed housing  53 . 
           [0049]      FIGS. 9   a - 9   h  show alternative embodiments of the sealing gasket  540 . 
           [0050]      FIG. 10  shows a sealing gasket according to  FIG. 9   h  when arranged in a seed housing. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0051]      FIG. 1  is a perspective view of a precision seeder  1 , as viewed obliquely from behind. The seeder  1  comprises a frame with a longitudinal (as viewed in a direction of travel) beam  2   a  and a transverse beam  2   b . At the front end of the longitudinal beam  2   a  there is a connecting device  3  for connecting the seeder to a towing vehicle, such as a tractor. In addition, there is a fan  4 , which is arranged to supply, via a number of tubes, manifolds and hoses, compressed air to a plurality of row units  5   a - 5   h . Along the transverse beam  2   b  there is also a plurality of support wheels  6   a - 6   d . The function of the support wheels is to permit road transport as well as to support the frame during seeding. 
         [0052]    Referring now to  FIG. 2 , each of the row units  5   a - 5   h  basically constitutes a separate seeder, to which compressed air and electricity are supplied, said seeder comprising a seeder frame structure  51 , a seed hopper  52 , a seed housing  53 , a pair of depth-level controlling means  54 , a press wheel  55  and a pair of seed furrow closing means  56 . In addition, the seeder has a seed furrow opener, which can be in the form of a pair of mutually inclined discs, and a seed tube  57 , which conveys the seeds from the seed housing  53  to a seed knife (not shown) or directly to an outlet (not shown) where the seeds are discharged into an opened seed furrow. 
         [0053]      FIG. 3  shows the seed housing  53  as viewed from the front, which is the side from which the seed housing is accessible when mounted on a row unit  5   a - 5   h . The seed housing  53  is formed by a front unit  531  and a back unit  532 . The front unit  532  is removably attachable to the back unit  531  by the intermediary of fastening means  535   a ,  535   b , which can be bayonet fittings, threaded joints, snap-in fittings or the like. 
         [0054]    The seed housing further has an opening  533 , through which the normal-pressure side of the singulating disc  539  ( FIG. 5 ) communicates with the surrounding environment, and an air intake  534 , through which the high-pressure side is connected to the fan  4 . 
         [0055]    Referring to  FIG. 4 , the seed housing further has a seed inlet  536 , through which seeds are fed from the seed hopper  52 . A seed lever  537  can be arranged to control, by displacing it or rotating it, the flow area of the seed inlet  536  and, thus, the rate at which seeds are supplied from the seed hopper  53  to maintain a given level of seeds in the seed housing  53 . The seed hopper can be arranged to feed seeds to the seed housing by gravity only, or by means of a feeding device, such as a scraper, a conveyor belt, a conveyor screw, an agitator or the like. 
         [0056]    The seed tube  57  extends from the seed housing  53  and connects the seed housing to a seed knife (not shown) or a seed outlet (not shown). 
         [0057]      FIG. 5  is a sectional view of the seed housing  53 . A motor compartment  538  holds a seed housing driving mechanism  5380 , which can be in the form of an electric motor, which can be connected to the singulating disc  539 , such that the driving mechanism drives the singulating disc to rotate about a substantially horizontal axis through its centre. 
         [0058]    The singulating disc  539  can be connected to the driving mechanism  5380  by way of a removable joint  5392 , comprising for instance a bayonet fitting, a threaded joint or a snap-in fitting. 
         [0059]    The singulating disc  539  forms a division between a high-pressure side  5310 , which is supplied with pressurized air from the fan  4  via the air intake  534  , and a normal-pressure side  5320 , which communicates with the surrounding air via the opening  533 . 
         [0060]    The singulating disc  539  has a plurality of through holes  5391 , which are each positioned at essentially the same radial distance from the centre of the singulating disc  539  and at essentially the same distance from each other. The holes  5391  can have a cross section that is tapering either towards the high-pressure side  5310  or towards the normal-pressure side  5320 . 
         [0061]    Furthermore, a seal  5393 , which here is in the form of a rubber-covered wheel, can be arranged, at a certain position of rotation of the singulating disc  539 , to block the normal-pressure side of one or more holes  5391 , so as to cause a seed carried adjacent to the hole to be released from the singulating disc  539  and drop into a connecting means  5394  connecting to the seed tube  57 . 
         [0062]    A sealing gasket  540  is arranged in an axially open groove  5321 , which runs along substantially the whole axial connecting portion of the front unit  532 . The groove  5321  can have a substantially constant cross-section. In one embodiment, the groove  5321  has a plurality of protuberances or lugs, which extend inwardly into the groove and which ensure satisfactory attachment of the sealing gasket  540 . 
         [0063]    The sealing gasket  540  has a number of functions. A first function is to provide a seal between the back unit  531  and the front unit  532 , so as to reduce air leakage from the high-pressure side  5310  through the joint between the back unit  531  and the front unit  532 . A second function is to provide a seal between an axial surface of the singulating disc  539 , close to its periphery, and the front unit  532 , so as to reduce air leakage from the high-pressure side  5310  through the interspace between the singulating disc  539  and the front unit  532 . 
         [0064]      FIG. 7  shows a perspective view of the inside of the front unit  532 . Also visible are the fastening means  535   a ,  535   b  and the seal  5393  as well as the air outlet  533 . 
         [0065]    Referring now to  FIGS. 8   a - 8   c , the sealing gasket will be described in greater detail. It will be appreciated that  FIGS. 8   a - 8   c  show the sealing gasket  540  in an unstressed (passive) state, and that  FIG. 6  shows the sealing gasket  540  in a stressed (active) state. 
         [0066]    The sealing gasket  540  consists of an elongate body having a substantially constant cross-section along its whole length. In one embodiment ( FIG. 8   b ), the sealing gasket can have a substantially circular shape. It will be appreciated that the shape of the sealing gasket is suitably adapted to match the shape of the seed housing, or at least to match the shape of the front unit  532  of the seed housing  53 . 
         [0067]    The sealing gasket can be made of a resilient material, such as rubber or a rubber-like material, such as an elastomer (TPE, TPO, TPU). It is also conceivable for the sealing gasket to be made of another polymer material, provided that sufficiently good sealing capacity and strength can be achieved. 
         [0068]    In one embodiment, the sealing gasket can be formed directly in its final mould through injection moulding, compression moulding or die-casting. 
         [0069]    In another embodiment, the sealing gasket can be formed by shaping an elongate sealing strip of the desired profile into the desired structure and joining its ends together. 
         [0070]    A further alternative is to form the sealing gasket as a two-component part, in which the part that makes contact with the seed disc is optimized to resist wear and reduce friction, which occur due to the relative movement between the seed disc and the seal. For example, this part can be made of a harder material than the rest of the sealing gasket. 
         [0071]    Referring to  FIG. 8   c , the cross-sectional profile of the sealing gasket  540  can have a base portion  5401 , which can be substantially plane and have a substantially constant material thickness. A first sealing lip  5402  can be joined to one end of the base portion  5401 . In one embodiment, the first sealing lip  5402  is joined to the base portion  5401  via a curved portion  5406 . This curved portion can, in unstressed state, form an angle of between 30 and 80 degrees to the base portion  5401 . 
         [0072]    The first sealing lip  5402  can have a free end  5404 , which can be provided with a portion of thicker material. 
         [0073]    The first sealing lip can have a length corresponding to approximately 20%-50% of the length of the base portion  5401 , preferably approximately 30%-40% of the length of the base portion. 
         [0074]    A second sealing lip  5403  can be joined to the other end of the base portion  5401 . In one embodiment, the second sealing lip  5403  is joined to the base portion  5401  via a curved portion  5407 . This curved portion can, in unstressed state, form an angle of between 30 and 80 degrees to the base portion  5401 . 
         [0075]    The second sealing lip  5402  can have a free end  5405 , which can be provided with a portion of thicker material. 
         [0076]    The second sealing lip can have a length that approximately corresponds to the length of the base portion  5401  less the length of the first sealing lip  5402 . 
         [0077]    It will be appreciated that the second sealing lip  5403  can have a length corresponding to approximately 50%-80% of the length of the base portion, preferably approximately 60%-70% of the length of the base portion. 
         [0078]    It is not excluded that the sum of the lengths of the first and second sealing lips exceeds or is less than the length of the base portion. For example, the sum of the length of the sealing lips can be 10%-30% greater or smaller than the length of the base portion. 
         [0079]    The sealing lips  5402 ,  5403  enclose, together with the base portion, a space  5412 , which has an opening defined by the free ends  5404 ,  5405  of the sealing lips and which tapers towards said opening. 
         [0080]    The base portion  5401  can be said to define a main plane for the sealing gasket  540 . The sealing lips  5402 ,  5403  are located on a first side of this main plane, and an attachment portion  5408 ,  5409  is located on a second side of the main plane. 
         [0081]    The attachment portion can be designed in a number of ways. In the embodiment shown, the attachment portion comprises a pair of tongues, which extend substantially at right angles to the main plane and, thus, to the base portion  5401 . The tongues  5408 ,  5409  are separated by a groove  5411 . It is conceivable, and possibly advantageous, to form bridges of material between the tongues  5408  and  5409  at regular intervals along the longitudinal direction of the sealing gasket  540  in order to improve the dimensional stability of the tongues. 
         [0082]    One, or both, of the tongues  5408 ,  5409  can be provided with a locking lug  5410 . The locking lug can be shaped to engage with corresponding lugs of the groove  5321 , as described above. 
         [0083]    According to different embodiments, the attachment portion  5408 ,  5409  can be shaped to engage with the groove  5321  in a formfitting manner  5321  only, by force only or through a combination thereof. 
         [0084]    As shown in  FIG. 8   c , the attachment portion  5408 ,  5409  can be offset relative to any one of the ends of the base portion  5401 . It can be offset either towards the end to which the first sealing lip  5402  is joined or towards the end to which the second sealing lip  5403  is joined (as shown in  FIG. 8   c ). The offset distance can correspond to the whole distance to the end, or part of that distance (for example 40%-90%). 
         [0085]    Since the functioning of the seed housing  53  has been previously described above, a further description thereof is deemed unnecessary. 
         [0086]    And so the following description will focus on the functioning of the sealing gasket  540  in the seed housing  53 . 
         [0087]    As mentioned above, the sealing gasket  540  is fixedly attached in the axially open circular groove  5321  of the front unit  532 . The fixation can occur by the sealing gasket being aligned with the groove and then inserted in the groove by means of an axially applied force. 
         [0088]    Subsequently, the front unit  532  is fitted to the back unit by means of associated fitting elements, which, as in the present invention, can be in the form of associated axially open and cooperating grooves, the front unit being pressed against the back unit in such a manner that the first sealing lip  5402  enters into contact with a surface of the back unit  531  (see  FIG. 6 ) and the second sealing lip  5403  enters into contact with an axial surface of the singulating disc  539 . As a result, the free ends  5404 ,  5405  of the sealing lips  5402 ,  5403  will be bent inwardly towards the base portion  5401 , thereby providing a sealing effect relatively to the back unit  531  and the singulating disc  539 , respectively. This condition persists or is further enhanced by actuating the fastening means  535   a ,  535   b  in order to lock the front unit  532  to the back unit  531 . 
         [0089]    When air is supplied by the fan  4  to the high-pressure side  5310  of the singulating disc  539 , some of the air will leak through the gap between the singulating disc and the back unit  531  (See  FIG. 6 ). The air will leak through the opening defined by the free ends  5404 ,  5405  of the sealing lips and into the space  5412 , pressurizing also this space. The pressurization of the space will cause the sealing lips  5402 ,  5403  to be forced outwards towards the back unit edge and the singulating disc  539 , respectively, which will increase the contact pressure of the sealing lips and, thus, their sealing effect. 
         [0090]    It will be appreciated that the sealing gasket  540 , owing to the rotation of the singulating disc, will be subjected to wear. However, since the sealing gasket  540  is fixedly arranged in the front unit  532 , it can be easily replaced, even under on-site conditions. In addition, the fact that the sealing gasket  540  is arranged on the front unit  532  reduces the risk of seeds entering the sealing gasket space  5412  when opening the seed housing, which would impair the functioning of the sealing gasket  540 . 
         [0091]    It will also be appreciated that the fact that the gasket is removed along with the front unit makes it easier to get rid of seeds that have penetrated into the space of the sealing gasket than if the gasket hade been attached to the back unit. 
         [0092]      FIGS. 9   a - 9   c  show alternative sealing gaskets, which all lack an attachment portion. Instead, the base portion  5401  can be fastened by squeezing in a groove in the lid, and/or be provided with an adhesive means, such as tape that is adhesive on both sides. 
         [0093]      FIG. 9   a  shows a sealing gasket which has a base portion  5401  and first and second sealing lips  5402 ,  5403 , the second sealing lip being provided with a wear protection  5413 . The wear protection can be made of plastic, rubber or a thermoplastic elastomer with a higher durability and/or lower friction than the material of which the rest of the sealing gasket is made. For example, the wear protection  5413  can be harder than the rest of the sealing gasket. As a result, the wear caused by the movement of the seed disc  539  relative to the sealing gasket  540  can be reduced and, thus, the service life of the sealing gasket prolonged. The wear protection and the sealing gasket can be formed by so-called two-component moulding of thermoplastics and thermoplastic elastomers. 
         [0094]      FIG. 9   b  shows a sealing gasket where the second sealing lip  5403  has a concave portion  5414 , as viewed from the outside, and thus corresponds to the sealing gasket shown in  FIG. 6  and  FIGS. 8   a - 8   c.    
         [0095]      FIG. 9   c  shows a sealing gasket where the first sealing lip has been replaced by a compressible seal  5425 , which here is in the form of a hollow portion. 
         [0096]      FIG. 9   d  shows a sealing gasket, the second sealing lip of which is drawn out to a considerable degree and extends more than twice (preferably about three times) the distance from the base portion  5401  as compared with the first sealing lip. 
         [0097]      FIG. 9   e  shows a sealing gasket, whose first sealing lip has been replaced by a compressible seal  5416 , which here is in the form of a “comb” having a plurality of ridges and grooves. 
         [0098]      FIG. 9   f  shows an embodiment of the sealing gasket, which is identical to the one in  FIG. 9   a  but provided with an attachment portion  5409 . 
         [0099]      FIG. 9   g  shows an embodiment of the sealing gasket, which is identical to the one in  FIG. 9   b  but provided with an attachment portion  5409 . 
         [0100]      FIG. 9   h  shows an embodiment of the sealing gasket, which is identical to the one in  FIG. 9   c  but provided with an attachment portion  5409 . 
         [0101]      FIG. 10  shows how a sealing gasket with a compressible seal according to  FIG. 9   h  is arranged to seal a seed housing. The compressible seal  5415  here seals between the back unit  531  and the front unit  532  and the second lip  5403  seals between the seed disc  539  and the front unit  532 .