Patent Publication Number: US-7219610-B2

Title: Grate plate arrangement for step plates

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
   This application claims the priority benefit of German Patent Application No. 10 2004 040 048.2 filed on Aug. 18, 2004. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
   Not Applicable. 
   DESCRIPTION OF THE BACKGROUND ART 
   This invention relates to a grate plate arrangement for step grates. Generally, step grates include several grate plates laid out beside each other on one grate carrier to form one grate plate row; several grate plate rows laid out behind each other in the conveying direction form the step grate. The grate plate rows have a stepped arrangement, that is, the front area of each grate plate row rests on the rear area of a following grate plate row in the conveying direction. To convey granulated materials lying on the grate, in general individual grate plate rows are arranged movable in the conveying direction while other grate plate rows remain immovable. 
   Special problem areas of this type of step grates are the end walls of the individual grate plates. On the one hand, the end walls of the grate plates of the movable grate plate rows transport granulated materials in the conveying direction, thus subjecting them to particular wear and tear. On the other hand, the end walls of each grate plate row, together with the following grate plate row moving relative to it, form an open motion gap that prevents damaging friction, which would lead to increased wear and loss of driving power, from occurring in the overlapping area of the grate plate rows moving relative to each other. The motion gap is generally blown free by a flow of cooling air passing through it. It must be dimensioned as narrow as possible so that the proportion of cooling air emerging from the motion gap does not become uncontrolled large. 
   It is already known from EP 0 740 766 B1 that attaching a height-adjustable front plate to the end wall of a grate plate will allow for the precise adjustment of the motion gap. The front plates are fastened using studs which penetrate through oblong holes formed in the front plate and screwed into tapped holes formed in the grate plate. After installation, the studs are welded to the front plate and the front plate itself is welded to the grate plate. This allows the structure to bear the significant loads occurring during operation. The front plates are preferably manufactured from a heat-resistant and abrasion-resistant material. 
   Direct contact with the extremely abrasive material conveyed significantly wears out the bolt heads. If the front plates have to be readjusted after a longer operating period in order to readjust the motion gap increased by wear and tear, then the bolt heads have to be cut off and the shanks of the studs removed and discarded. Another disadvantage of this known arrangement lies in the fact that the studs are exposed to a high-temperature load through direct contact with the hot material, making the use of a high-temperature material necessary. 
   SUMMARY OF THE INVENTION 
   The task of this invention is to create a grate plate arrangement for step grates where the studs are protected from direct contact with the granulated materials and hence from strong wear and tear and thermal stress. According to the invention, this task is accomplished by covering the bolt heads of the studs by a cover. 
   Covering the bolt heads prevents the studs from being directly exposed to the effects of heat through the granulated materials, making the use of studs made of high-temperature material unnecessary. Moreover, the bolt heads are protected against the abrasive effect of the granulated materials and hence from wear and tear, making them easily detachable by normal means using a wrench if and when the front plate has to be readjusted. Another advantage is that the studs can be reused. 
   According to one embodiment of the invention, the bolt heads are each fastened in a recess countersunk into the front plate so that they do not protrude and so that the front plate can be positioned directly against the end wall of the grate plate, which is shown in the exemplary embodiments. 
   Basically, when using several studs one can arrange several or all bolt heads in one common recess and, for example, cover them with one common cover or hold each of them in their own recess and cover them with associated covers. 
   A preferred design of the invention provides for the recess to hold the bolt head to be built into the face of the front plate opposite the end wall of the grate plate. On the base of the recess is a hole for the shaft of the stud penetrating through the front plate. The coverings are formed as one cover sealing the recess. This design permits an especially simple installation where the front plate is installed from the front into the desired position on the end wall of the grate plate and is at least temporarily fixed by tightening the studs. 
   The invention provides for the recess being formed by a dead-end groove extending inwards from one outer edge, preferably the top edge of the front plate, and the cover being insertable into this groove from outside. According to another version of this embodiment, the sides of the groove are each equipped with a guide profile and the cover has the form of a sliding plate inserted into this groove from outside and equipped on its sides with counter-profiles corresponding to the guide profiles of the groove. 
   To be able to remove the cover more easily from the grooves when readjusting the front plate and thus make the bolt heads accessible, it is further provided to have the sides of the groove and, accordingly, the sides of the cover slightly converge in the sliding direction of the cover. In this way, the slots of the groove and the counter-profiles of the cover come out of contact when the cover moves slightly outwards, allowing for easy removal of the cover. 
   According to one favorable mechanical design, the cover has a lip on its rear edge in sliding direction extending towards the end wall of the grate plate. This lip inserts into a corresponding recess in the associated outer edge of the front plate when the cover is installed. On the one hand, the lip can serve as a stop defining the end position of the cover; on the other hand, the lip covers the gap between the opposing surfaces of the cover, on one side, and the front plate, on the other, and hence the recess where the bolt head is located. 
   To protect the cover itself against wear and tear, it is provided to have the cover be flush with the face of the front plate when the cover is installed, and preferably to have the lip on the cover be flush against the outer edge of the front plate as well. 
   To be able to adjust the front plate to different heights, the hole in the front plate is made in the form of an oblong hole extending from top to bottom in a known manner. 
   According to another design, there is an exchangeable, vertically movable sealing lip on the bottom edge of the front plate. This lip is pressed against the top side of the following grate plate by its own weight or, optionally, aided by spring force, thereby keeping the sealing clearance closed. 
   After the cover is inserted in position covering the recess, it is suitably fastened on the front plate. It is preferable to have the cover welded to the front plate. To be able to dismantle the front plate for the purpose of readjustment, one only needs to undo the weld seam between cover and front so that the cover can be removed in the manner described below and the bolt head of the stud becomes accessible. 
   To rule out any undesired loosening of the stud, for example caused by vibrations during operation, another embodiment of the invention provides that the cover exhibit on its inner side, the side toward the stud, lateral steps that engage the wrench flats of the stud to prevent the head from turning. 
   The bolt head must then be designed and installed so that these wrench flats are somewhat parallel to the sliding direction of the cover in order for the side steps of the cover to lie against the wrench flats. 
   According to another mechanical design of the invention, the recess is built into the locating face of the front plate opposite the end wall of the grate plate and basically has the form of a dead-end T-groove extending inwards from one outer edge, preferably the bottom edge of the front plate. The stud is installed before the front plate is placed so that the bolt head keeps a prescribed distance from the end wall of the grate plate in order that the front plate can slide over the bolt head with the T-groove. The bolt head thus forms a sliding block matching the shape of the T-groove. The outward cover of the recess is formed by the rear wall of this recess. 
   In order to allow for rotary fixation of the stud in this design, it is provided to have the sides of the recess positioned against the wrench flats of the bolt head when the front plate slides on. In this configuration the bolt heads have to be suitably designed and aligned during installation so that they lie essentially parallel to the sliding direction of the front plate so that the sides of the recess can align to the wrench flats of the bolt head. 
   To install the front plate, first the studs are installed on the grate plate so that the front plate can be slid onto the bolt heads in close alignment to the end wall of the grate plate. The front plate is then fixed in the desired position and preferably welded to the grate plate. To disassemble the front plate, one only has to undo the weld seam between front plate and grate plate so that the front plate becomes removable. 

   
     BRIEF SUMMARY OF THE DRAWINGS 
     Several embodiments of the invention are shown in the drawings and described in more detail hereinafter. In the drawings: 
       FIG. 1  is a schematic diagram of a partial view of a step grate; 
       FIG. 2  is a perspective exploded view of the end wall area of a grate plate and a front plate to be installed on the end wall; 
       FIG. 3  is a cross-section through a cover along the section line III—III; 
       FIG. 4  is a section approximately corresponding to the section line IV—IV in  FIG. 2 , but in installed condition; 
       FIG. 5  is a perspective exploded view of the end wall area of a grate plate as well as a front plate to be installed on the end wall according to another embodiment of the invention; 
       FIG. 6  is a section corresponding to the section line VI—VI in  FIG. 5 ; 
       FIG. 7–9  are different versions of front plate and coverings; and 
       FIG. 10  is a sectional view of a front plate with sealing lip. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The basic setup of a step grate, to which the present invention relates, is shown in  FIG. 1 . Several grate plates  4  laid out beside each other on a grate carrier  2  form a grate plate row  6 . Several grate plate rows  8 ,  6 ,  10  laid out one after the other form the grate, which as such, is already generally known and therefore not described here in more detail. The grate plate rows  8 ,  6 ,  10  laid out one after the other each have a stepped overlapping arrangement so that the front area of the grate plates of one grate plate row is resting on the rear area of the grate plates of the grate plate row following in the conveying direction  12 . In the example of  FIG. 1 , grate plate row  6  is movable back and forth in the direction of double arrow  14 , while grate plate rows  8  and  10  are stationary grate plate rows. Other arrangements where several movable grate plate rows alternate with several immovable ones are possible. 
   The granulated materials resting on the grate are cooled by the cooling air conveyed, for example, through grate carrier  2  and through the slots  16  formed on the top side of grate plates  4 . The granulated materials are conveyed in conveying direction  12  by the forward and backward motion of movable grate plate row  6  (and is supported by the cooling air blowing, for example, forward obliquely). 
   In the overlapping areas between the individual grate plate rows, that is, for example, between stationary grate plate row  8  and movable grate plate row  6 , on the one hand, and movable grate plate row  6  and stationary grate plate row  10 , on the other, are so-called motion gaps  20  or  22 , that is, the grate plate rows must not come into contact within these areas. Generally, motion gaps  20 ,  22  are blown free by cooling air conveyed from the compartment underneath the grate. The width of the motion gaps must be kept as small as possible so that uncontrolled large amounts of cooling air do not leak out of them. However, one cannot prevent granulated materials from penetrating motion gaps  20 ,  22 , whereby wear and tear expands them during longer operation periods. It is therefore desired to be able to readjust motion gaps  20 ,  22  at specific time intervals. 
     FIG. 1  shows one possible embodiment of a front plate  24  attachable to end wall  18 . Other versions are shown in the other drawings and are described with them. All solutions are common in that they protect the bolt heads from getting in direct contact with the material to be conveyed. 
   Number  24  is a front plate that can be fastened to end wall  18  using stud  26 . The stud  26  penetrates through a hole  28  in the front plate  24  and is screwed into a tapped hole in the grate plate  4 . Either the opening  30  in the end wall  18  is constructed like a tapped hole or the stud  26  penetrates through the opening  30  and is screwed into a tapped hole provided inside the grate plate  4 . 
   The hole  28  is an oblong hole extending from top to bottom so that the front plate  24  becomes height-adjustable. In this manner, any desired motion gap can be adjusted between the bottom edge of the front plate  24  and the respective grate plate following in the conveying direction  12 . 
   As can be seen from  FIG. 1 , the bolt head  32  of the stud  26  is countersunk in a recess  34 , on the face  36  of the front plate  24  opposite the end wall  18  of the grate plate  4 . The recess  34  can be covered on the outside with a cover  38  that can be slid into it from the top so that the bolt head  32  is protected. To fasten the cover  38  to the front plate  24 , it is welded to the front plate  24  and/or the grate plate  4  after installation. 
   If the front plate  24  has to be loosened, for example, in order to readjust the motion gap, one simply has to undo the weld seam between cover  38  and front plate  24  and to remove the cover  38  so that the bolt head  32  becomes accessible and detachable using a suitable tool. This way the front plate  24  can be readjusted several times, with the cover  38  and the stud  26  remaining reusable. 
     FIG. 2  shows in detail the front area (in conveying direction  12 ) of a grate plate  40  as well as a front plate  44  attachable to the end wall  42  of the grate plate  40 . The front plate  44  essentially only differs from the front plate  24  shown in  FIG. 1  in that, instead of one stud, two identical studs  46 ,  48  are used to fasten the front plate  44  to the end wall  42  of the grate plate  40 . In the face  50  of the front plate  44  facing away from the end wall  42  are two recesses  52 ,  54 , in which the bolt heads  56 ,  58 , respectively, can be countersunk. On the base of each recess  52 ,  54  is an oblong hole  60  and  62  extending from top to bottom, through which the associated studs  46 ,  48  penetrate so that they can be screwed to the grate plate  40  in a manner that is not described in detail. The holes  60 ,  62  are constructed as oblong holes to allow for adjustment of the front plate  44  to different height positions and thus for setting any motion gap between the bottom edge of the front plate  44  and the next grate plate. 
   The recesses  52 ,  54  are constructed as dead-end grooves extending downwards from the top edge of the front plate  44 . They can be covered by associated covers  64 ,  66 . Since the recesses  52 ,  54  as well as their respective studs  46 ,  48  and covers  64 ,  66  are designed identically, only the arrangement shown to the left in  FIG. 2  will be described in detail. 
   The sides  68 ,  70  of the recess  52  each have a guide profile  72 . Accordingly, the cover  64  has corresponding counter-profiles  78  on its sides  74 ,  76  so that the cover  64  can be slid into the recess  52  like a sliding plate to cover the recess as well as the bolt head  56  within it. 
   The cover  64  has a lip  80  on its top or rear edge in sliding direction extending out towards the end wall  42 . This lip inserts into a corresponding recess  82  in the top edge of the front plate  44  when the cover  64  is installed. The cover  64  is laid out so that when installed it is flush with the face  50  of the front plate  44  and the lip  80  is flush with the top edge of the front plate  44 . 
   It is preferable to construct the recess  52  as slightly converging in the sliding direction to simplify the removal of the cover  64  from the recess  52 . Once installed, preferably, the cover  64  is welded to the front plate  44  and/or the grate plate  40  and thus fastened.  FIG. 3  shows a cross-section of the cover  64  corresponding to the section line III—III in  FIG. 2 . As can be seen in  FIG. 3 , side lips  84  are built on its inner side facing the bolt head  56 , engaging the wrench flats of the bolt head  56  when installed, and securing the bolt head  56  against turning. 
     FIG. 4  shows a longitudinal section of the cover  64  according to the section line IV—IV in  FIG. 2 , viewed in the direction of the arrow  86 . What can be seen is the end wall  42  of the grate plate  40 , the front plate  44  positioned next to the face  50  of the end wall  42 , the stud  46  fastening the front plate  44  and countersunk in the recess  52 , and the cover  64  covering the recess  52  against the outside. Furthermore, one can see the side lip  84  positioned against one wrench flat of the bolt head  56  opposite the viewer. 
     FIG. 5  shows another embodiment of a front plate  92  attachable to the end wall  88  of a grate plate  90 . In order to fasten the front plate  92 , two studs  94 ,  96  are screwed so far into the end wall  88  that the bolt heads  98  and  100  keep a prescribed distance from the end wall  88 , allowing one to slide the front plate over the bolt heads close to the end wall  88 . 
   In the locating face of the front plate  92  opposite the end wall  88  of the grate plate  90  are two dead-end recesses  102 ,  104  extending upwards from the bottom edge and having a T-groove-like cross-section. The front plate  92  is fastened to the end wall  88  of the grate plate  90  by sliding the recesses  102 ,  104  from the top over the associated bolt heads  98  or  100  respectively. The bolt heads  98 ,  100  are thus covered against the outside by the bottom walls  103 ,  105  of the recesses  102 ,  104 . Afterwards, the front plate  92  is fastened permanently to the grate plate  90 , preferably by welding. To disassemble the front plate, one only has to undo the weld seam between the front plate  92  and the grate plate  90 . The studs  94 ,  96  and the front plate  92  can be used several times in this embodiment as well. 
   The recesses  102 ,  104 , on the one hand, and the bolt heads  98 ,  100 , on the other, are laid out and dimensioned so that sides (e.g.  106 ,  108 ) of the recess  102  rest against wrench flats (e.g.  110 ,  112 ) of the associated bolt head  98  when the front plate  92  is slid on and thus secure the bolt head from turning. 
     FIG. 6  shows a cross-section of the front plate  92  corresponding to the section line VI—VI in  FIG. 5 . One can once again see the shape of the T-groove recess  102  with a lateral surface  106 , which rests against the bolt head  98  and secures it from turning. 
     FIGS. 7 to 9  shows different solutions for the design of the front plate. 
     FIG. 7  shows a front plate  114 , which is fastened to the end wall of a grate plate with two studs (where, to simplify matters, only one stud is shown with the bolt head  116 ). On the front plate  114  is a recess  118  for reception of both bolt heads, which, once the studs are installed, is covered by a cover  120  slid into the recess  118 . In the area of the bolt heads the cover  120  has a similar shape as the covers  64 ,  66  in  FIG. 2 , that is, the recesses  122  holding the bolt heads have side lips  124 , which rest against the wrench flats of the bolt heads aligned accordingly and secure them from turning (this does not need to be shown in more detail again). 
     FIG. 8  shows a front plate  124  with two separate recesses  126 ,  128  for two studs, of which only the bolt head  130  of one stud is displayed. The recesses  126 ,  128  are covered by a cover  134  slid into in a corresponding recess  132  in the front plate  124  to such an extent that the cover  134  is flush with the outer surface of the front plate  124 . 
     FIG. 9  shows a front plate  136  with two recesses  138 ,  140  for two studs, of which only the bolt head  142  of one stud is shown. The recesses are covered by a cover  144  attachable to the outer surface of the front plate  136  and, for example, welded to it. 
   Finally  FIG. 10  shows a cross-section of a front plate  150  in the area of its bottom edge  152 . In one groove  154  in the bottom edge  152  a freely vertically movable sealing lip  156  is arranged, which rests against the top edge  160  of a grate plate  164  following in the conveying direction  162 , for example, only by virtue of its own weight or through the force of spring means  158  in the groove. The sealing lip  156  is, for example, made of a low-wear material and preferably easily exchangeable and replaceable with a new one. 
   While there have been shown and described what is at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention defined by the appended claims.