CA2018120C - Rock picking machine - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An improvement in a rock picking machine having a frame with ground wheels supporting the frame, a table with a grate over which rocks are moved and discharged into a bucket rearwardly pivotally mounted on the frame, and a conveyer forwardly pivotally mounted on the table for moving rocks up the grate. The improvement consists of at least one forwardly and upwardly extending member positioned at a rearward end of the conveyer frame. The member forms a wedge shaped cavity. As large rocks are moved up the grate by the conveyer through the wedge shaped cavity, the rocks engage the member thereby lifting the rearward end of the conveyer frame to provide clearance.

Description

The p:reserl-t inverltiorl relate~ -lo atl imprOVellleIl'l :irl a rock pickirlg machine.

BAC~GROUND OF THE INV~NTION
The pr~serl-t irlve~t:iun relat~s to improveni~rl-ts for a rock picking machine origirlally designed by Johr Schul-te as described irl Canadiarl Pa-terlt 699 748. The Schulte machine i~ ~ubject to "jamming" by rocks and soil retention under certairl conditions. Some of -these 10 conditiorls are outlined in Evaluation Report Number E3880B published by the Prairie Agricultural Machirlery Institute (PAMI) i~ September of 1981. The PAMI
Evaluation Report on page 4 identiEies a "jammirlg"
problem with respect to large rock~; "Rock~ larger the~
15 520mm (20 in.) would not pas~ betweerl -the conveyer cro~smember and the grate.". In ord~r to avoid problems of ~oil retentiorl the P~MI EvaluatioIl RPport made recommerlda-tions wl-th respect to operatirlg depth and field preparation. The suggested operating d~pth wa~

2~ "with the grate just touchiAg the ~oil ~urface". The short comings of this sugge~ted operatiny depth was described on page 4 as ~ollows; "This was adequate for removing rocks lying on the s~rface, howeves par-tially buried fork8 were pu~hed back in-to the soil by the 25 grate.ll The suggested field preparatioII fo;r be~t performance wa~ "in fields with a firm ha~e and a minimum amourlt of tra~h OI' dirt lwnp~." The ~p-plicant ~la~ fourld that opcratincJ a-t the recommerlded operatirlg depth some-t~ te~ -result~ in rock3 jammirtg be-tween the 30 conveyer teeth and the forward edge of the yra-te. Th0 PAMI Evaluation Report al50 indicated some "jamming"
which occurred with ~mall rock~. In mo~t case~ these jammecl rocks could be remcved by revers:iIlg the conveyer.
However small rock~ "sometimes jammed between the 35 conveyer bat tee-th arld the rear of the yrate preve~ti~

a.~

the corlveyer from beincJ reversed". Allo-ther t-ype o~
"jamming" ~oted by the Applicarlt i~ by rock~ which, irnstead of L emaiIling iIl the buc~e-t, are carri~d by the cros~ bar to a positiorL where -they jam -th~ corlveyer.

SUMMARY QF T~E INVE~TION
.
What is re~uired is some modif:;catiorls to the Schulte rock picking machirle which will address one or more of the problems de~cribed.

The Schulte roc~ picking machirle has a frame with grourld wheels suppor-tirlg the frame, and embodyin0 a gra-te over which rocks are moved and discharged into a bucket rearwardly pivotally moun-ted on -the fram~. A
15 -table on which the grate is mourlted is rearwardly pivoted o~ the frame to be movable between a rock picking position in relation to the grownd and a position elevated from the ground. A conveyer is forwardly pivotally mounted on the table for moving 20 rocks up -the grate. The corlveyer includes a frame Wi th sprocket ~heel~ rotatably mounted on the conveyer frame.
Chains are trained over aligned sprocket wheel~ and conveyer cross bar~ are fixed to the chairl~ a-t in terval5 . Tee th Vrl the CY'055 ba-r~ erlgage and move 25 rock~ up the grate. Me~n~ are provided Eor drlvlrly the ~procket wheel~.

Accordirlg to one aspect of th~ inverltiorl there i~
provided an which iS comprised of at least one forwardly 30 and upwardly extending member positioned at a rearward end of the conveyer frame. The member form~ a wedye shaped c~vity. As large rocks are moved up the grate by the conveyer through the wedge ~haped cavity, the rocks engage the member thereby lif-tirlg the rearward end of 35 the conveyer Erame to provide clearance.

~IJ~

Th.is improvemerl-t addresse~ -the proolem which previously exi~-ted ~ith -th~ Schulte r~ck picker of large rocks jamminy be-tweerl -the grate and -the conveyer frame.
The conveyer frame as modified will now be lifted as the 5 large rock passes up the grate to provide ~uch clearance as may be necessary to avoid jamming.

According to another aspect of -the inventiorl there i9 provided an improvemen-t which is comprised of an 10 extensiorl-to -the conveyer which e2cterlds forwardly of the table substantially parallel to the groundsurface when the table is in a rock picking poYition such -that -the cros~bars travel in a ~ubstantially horizontal path prior to encoun-teriny the grate.
This improvement addresses the problem which previously exis-ted of rock~ jammirlg between the teeth and a forward end of th~ grate. The modificatior changes the anyle of a-ttack on -the teeth of the 20 crossbars. A~ modified, th~ teeth draw rock~ from the ground surface in front of the grate toward the grate.
With the 5chulte rock picking machine the teeth -trav01ed alony a pclth dictated by the circumfererlce of th2 sprocket and the contact area between the l:ee~h and the 26 ground surface was l.imited.

According to another a~lpect of the inventiorl there i~ provided an improvemerlt which is comprised of a plurality of forwardly and downwardly extending ground 30 chise.ls pvsîtioned at -the forward end of t~le table. The ground chi~els engage the groundsurface to direct rock~
below the surface -to the grate.

This improvement addres~es the dilemmz presPnted -to t~le operator of t~e Sc~lulte rock pi,cking n~achirle o~
either opera-ting the machine with the grate just -touc,hirlg th~ ~oil ~urEace ~nd h~ve pc~r-tially buried rocks pu~hed back into -the soil by -the gr~te, or 5 OpeI'ating the maChirle Wi t~l the grate se-t belwr~ -t~le soil surface and having an unacceptable quatltity of soil re-tentiorl. The ground chi~els do rlot re-tairl soil, but do direct the rocks partially below the surface to -the grate.
According to a~o-ther ~spec-t of the iIlve~tion there is provided an improvemerlt which iS compri~ed of a wiper blade secured to each end of -the crossb~rs which eXterldS
orward of the teeth, such that the wiper blade directs 15 rocks away from the ends of -the crossbar.

This improvement addresses -the problem of small rocks being jammed be-tweerl the conveyer bat teeth and the grate. As modified, the ~iper blades dir~ct small 20 rocks away froJn -the edges of the yrate where they car become jammed.

According -to another aspect of the iI1ventioIl there is provided an improvement which i~ compri~ed of a 25 plurali-ty of spac~r members seeured -to a side o;f the cro8~ bars opposite the -teeth, thereby preventi}lg rocks o ~ size ~ufficient to c~lu~e a ja~ming of th~ rnachirle ron~ re~-tirlg upon and beirlg lif-ted by the opposed side of the cro~sbars.
This impro~ement addre6~es the problem of rocks being carried by the cross bars into a position where they jam the operation of -t~le conveyer. A5 modified, the spacer b~rs occupy the space on the opposite side of 35 -the cros5 bar so that there i~ siJnply IlO't sllfficient :rooM for a rock which iS of a ~uffic:ierlt ~ize tv c:reate a ja~l.

BRIEF DESCRIPTION OF T~E DRa~IN~S
These and other features of the inventioIl will become more apparent from the ollowing descrip-tion in which reEererlce i~ made to the appended draw:ings, wherei~:
FIGU~E 1 is labell~d as PRIOR ART, and illustrate6 10 the SCHULTE rock picking machine.
FI&URE 2 is a front elevatiorl view of a modified rock picking machine.
FIGVR~ 3 is a sec-tion view -taken alorlg section lines 3-3 of FIGURE 2.
FIGURE 4 is a de-tailed -top plan view o a modification at the rearward end of the convey~r.
FIG~R~ 5 i~ a de-tailed sec-tion view of -the modificatio~ illus-trated in FIGURE 4.
FIGURE 6 is a detailed side elevatioIl view of a 20 modifica-tion on the cro5s bars.
FIGUR~ 7 i~ a de-tailed frorlt elevation v:iew of the ~odificatiorl illustra-ted in ~IGURE 6.
FIGURE 8 is a dqtailed top plan view of a forward extensioIl of the conveyer.
~IGUR~ 9 i~ a dotailed ~:ide elevatioIl view of the forward exterlsion of the conveyer illu~trated in FIGURE
.
FI~URE 10 i~ a detailed front eleva-tiorl view o:E a modification to the forward end of the grate.
FIGUR~ a sec-tion view of the modificatlon to the forward end of the grate illu~-tra-ted in FIGUR~ 10.
FIGUR~ 12 i6 a side eleva-tion view of an end o.~ the grate illustrated in FIG~R~ 10.
FIGURE 13 is a front elevation view of -the end of 35 the grate illustrated in FIG~R~ 12.

~1 B~

~BODIME~T
T}le i~nprovt~n~ t~ will rlo~ be d~scribetl Wi th refererlce tu FIGURES 1 t~lrough 13. The origillal Schul tt3 rock picking machine, a~ illu~tra-ted in FIGUR~ 1 alld labelled a~ PRIOR ART, i~ gerlerally desLgrla-ted by reference numeral 10. In order -that -the siynificance of the modifications which have been maclt- to t~l~ Sohu:L-te rock pickirlg machine will be understood the ba.~ic structure of the Schulte machirle ~ill now be describecl.

Referring to FIGUR~ 1, rock pickincJ machine 10 ha5 a frame 12 with ground wheels 14 supE~ortinc~ frame 12.
gra-te 16 i5 provided over which rocks 18 are moved and discharged into a bucket 20 which i5 rearwardly 15 pivotally mDunted on frame 12. A table 22 iY provided on which grate 16 i9 mounted. Table 22 is rearwardly piv~ted on frame 12 and is mov~ble b~tweell a rock picking position in rela-tion to the ground and a position elevated from the ground. A c;onveyer 24 is 20 Eorwardly pivotally mounted on table 22 for moving rock~
up grate 16. Conveyer 24 has a frame 26 w.ith sprvcket wheel~ 28 rotatably mounted on conveyer ~rame 26.
Chains 30 are trairlt3d ovtlr al:igrled sprocket whe~ 28.
Con~eyer cro~s bar~ 32 are fixed to chaina 30 at 25 intervals. Teeth 34 on cros5 har~ 32 erlgage and move rock~ 18 up yra-te 16. A conveyer drive axle 36 is corlrlected b~ a c,haill 33 to arl axle 40 o;~ one of w~leels 14. A~ axle 40 rotates the link~cJe though Ch~itl 38 cau~es conveyer drive axle 36 to rotate. Conveyer drive 30 axle 36 extends through a pair of sprock~t wheels 28, thereby providing t~le means for driving sprvcket wheels 28. For the purpose of this description rock picklng machine will be considered -to have a -Eorward end 42 and a rearward end 44, and the various p~rts will b~

2~?1~3J ~

;c~ib~d wit~l r~!feI~rlc~ to ~rl o;~ rlt~l-tioIl towcl~cl forward end ~2 or rearward encl ~

One of the problem~, a~ previvu~ly de~cr:i~ed, with rock picking machirle 10 was i-t's inabili-ty to harldle rocks of a diameter yreater -t~lan 20 :inc~le~. The specified diameter was -the ava.ilable cleararlce betweer grate 16 and conveyer Erame 26. ReferriIlg -to FIGUR~5 Z, 3, 4, and 5, the ApplicaIIt has addressed this problem by 10 providing a plurality of forwardly a~d upwardly extending members 46. Member~ 46 are po~itioned at a rearward end 48 of conveyer frame 26 . For purpo~es of reinfurcement of members 46 a tran~verse reinforcemen-t bar 50 is secured to members 46. M~mbers 46 form a 15 wedge ~haped cavity 52. The use and operation of members 46 will now be de~cribed. A5 large ~ocks 18 are moved up grate 16 by conveyer 24 they enter wedge shaped cavity 52. Rocks 18 engaye member 46 thereby lifting rearward end 48 of co~veyer frame 26 -to provide 20 clearance. This is po~sible due to the fac-t that iII
rock pickiny mach:ine 10, conveyer frame 26 i~ forwardly pivotally mounted to table 22.

Another of the problem~ described Wi th respect -to 25 rock pickin~ machine lO, was rock~ jamming between teeth 34 and a furward erld 64 of grate 16. W~lellever rvck~ 1~
are trapped in thi~ po~i-tio~ a rJreat ban~ carl be heard a~ cro~ ~ar 32 i~ carr:ied arourld ~procket 23 until teeth 3~ strike the stationary rock. The Applicant 30 deterrnined tha-t this problem cowld only be corrected by modi~ying the angle of attach o~ teeth 34 with re~pect to grate 16. With rok picking ~achine 10 t~eth 34 travel along a path dictated by the circumference of ~procket 28 and the con-tact area betw~en teet}l 34 and the ground surface is limited. Referring to ~IG~RES 3, 8, and 9, the Applicarlt trcl~ addre~ed this prok)lelll by placirl~ asl ~xterl~;iorl ~i6 orl corlv~3y~r~ 2'~ W~liC~I e2~terlll8 forwa.rclly of -table 22 which supports yra-te 16 and substantially parallel to yrourld~urface 58 wherl table 22 i~ in a rock piCkiI1y posi tion. The ex-tellsion adds two more of spracket wheel~ 28, so that chairl 30 can extend to a forward end 60 of extension 56. When rock pickiny machine 10 is i~ operatio~, exte~sion 56 permit~
cro~sbars 32 travel iIi a substan-tially ~lori~orltal path 10 prior to encountering ~ra-te 16. Thi~ allows teeth 34 -to draw rock~ 18 from yround surface 58 in front of grate 16 toward grate 16. It i~ virtually impos~ible for the pr~viously experierlced jamming of rocks agains-t forward end 54 o~ grate 16.
Another problem descr,ibed with respec-t to rock picking machine 10 was grate 16 pushing partially buried rocks 18 back into cyround ~urface 58. This problem could be addressed by operatiny rock pickins machirle 10 wi-th grate 16 ~e-t be:Low ground surface 58. Th~ PAMI
report indicated that grate 16 could be set below ground ~urace ~8 if "the field wa5 no-t -too firm", but "Caution was needed to preven-t damaye -to the grate and ~rame when workirlg in ~i~lcd~ contalning larye emb~clcl~cl rock~.".
25 However, if ~rate 16 i~ operatecl below ~rourld ~urface 58 an unacceptabl~ quallt:ity r,~f Noil retentiorl urlavc)iclably ocour~. Referring to ~IGUR~S 2, 10, and 11, the Applicarlt address~d this yroblem by having a plurality of forwardly and dc~wrlwardly exterldirlg "T" shaped cJround 3~ chisels 62 positioned at fGrward end 6~l of table 22.
When rock pickiny machine 10 i5 ill operation grourld chisels 62 extend below ground surface 58 to direct rocks 18 below ground surface 5~ to grate 16. It is important to not~ the positicning of ground chi~els 62 35 and why it is preferred -that they be "T" shaped, with a -top po~-tiorl ~5 and a tail ~3uppor-t po~-tior~ ~. Ir1 th~
prior art table 22, upon which gra-te 16 is positionetl, ~k.ims -the yround ~urfact-~ wherl ln t~le rock picking posi-tion. Thi~ leads to a build up of earth, especially in ~iew of the plac~ment of transverse reirl~orceMerlt un the Schulte machine. The pr~sence of grourld chi~el~ 62, permits the Applican-t to op~ra-te his modifiecl rock picking machine with table 22 appro~ima-tely 5 inches above -the groundsurfaGe providiny addi-tional cleararlce 10 for the free passage of dirt arld rocks be-tweerl table 22 and the ground surface. Ground chisels 62 ~L'e positioned approximat~ly 3 inch~ apar-t this leaves sufficient room for -the free passa~e o-~ small rockc3 and dirt. The "T" shape serves an important purpose.
15 Instead of small rocks arld dirt buildiny up between ground chisels 62 which must work its way the entire width of a solid ground chisel the "T" shaped chisel is made out of 3/8 inch plate. The rocks and soil must only wvrk their way a distarlce of 3/8 of an illCh to pass 20 through the obstruc-tion created by -top portiorl 65 ar~d flow around -the balance of -the "T" shape. The "tail"
portions 67 of the "T" shaped chic3els are spaced abou-t 6 inche~ apart. This means that once dir-t clears -the 3/8th of arl inch of steel plate, represerltirlg t:h~
25 thicksless of tup p4rti4ns 65, th~ space ~vailable for dirt flow increaC3e~ from 3 irlches to B inch~ allOW:irlt3 for- the flow of dirt "around" ~rouIld chisels 62. The "T" shape allow~ for ~uf~ic:ie~lt strt~rl~th while avoidirlt3 a build up o-~ eclrth. A related modificatiurl :i~ th~ use 30 of pointed "~plitters" 63 on the for~ard edges ~hlch meet -thc rocks a~ is illustrated în FIGURES 12 and 13.
Split-ters 63 deflect rocks in either directio~ 50 the rock is ~ither in or out. With -the 5chul-te rock pickiny machine, table 22 had supporting "shoes"; rocks had a 35 tendency -to build up ~mder -the shoes thereby lifting ~21 J! 3L ~

the f:rorl-t of the machirle.

Arlo I her problem dE.~ ribed Wi th re~;pec-t -to :rock plcking device 10 wa:3 small rock~3 jammirly bet~veer conveyer teet}1 3~ and the ~:ide~ of grate 16, Referring to ~I~URES 2, 6, and ~, -the Applicar~t ha~ addrf3~sed the problem by securir~ a w.iper blade 66 tv each end 68 of crossbar~ 32. Wiper blades 66 extend -forward of tee-th 34. In order to ma~e this modification the Applicar1-t lO had to cut away part of grate 16 ~o WipeI' blade moved immediately adjacent grate 16 with no room for the er1-try of small rocks. Whe~ rock p:ickil1g machir1e lO is in operation, as cross bars 32 are moved by chains 30 alor1g table 22 which supports grate 16, wiper blade~ 66 direct 15 rocks away from end~ 68 of cr,ossbar 32, and hence away from the edyes of grate 16 where they can become jammed by teeth 34 positioned closest to ends 68 of cross bar 32.

A final problem describt.~d with respect to rock picking machine lO was that of rocks being carried by cross bar~ 32 into a po~itior1 where they jam the opera-tiwn of conveyer 24. Th:i~ jam typically occurred betwee~ cor1veyer drive axl~ 36 and CrC)~6 bar~ 32.
25 Referring to FIGUR~ 7, th~3 Applicant has M~c,urecl a plurality of space:r mf3mbers 70 to a side 72 o:F cro3 ba:r~ 32 oppo~ite te~th 34. Wher1 rock pick.ing machirl~ 10 i~ irl opf3ration, ~pacer bars 70 prev~nt rock~ 18 of a s:ize swffic:if3I1-t to cause a ,jamm:iny of rock picklng 30 machine lO from re~tin~ upon a~d being lif-ted by opposed side 72 of crossbars 32.
Spacer bars 70 occupy the space on opposed ~ide 72 of cros~; bar 32 50 that there i~; ~;imply no-t sufficient room for a rock s~hich i~; OIC a suf f ic:ierl-t size to create a 35 jam.

~IJ~

I t will be appa:rellt to one ~;lci:lled i~ 'che art that modificatiorl~3 may be ma~le to the i~np.rovemerl-t~; de~cribcd wi-tholl-t departi.llg from the ~3pi:~0i t and ~:cop ~ of t~le inverlt ion .

~0

Claims (7)

1. An improvement in a rock picking machine having a frame with ground wheels supporting the frame, and embodying a grate over which rocks are moved and discharged into a bucket rearwardly pivotally mounted on the frame, a table on which the grate is mounted being rearwardly pivoted on the frame to be movable between a rock picking position in relation to the ground and a position elevated from the ground, a conveyer forwardly pivotally mounted on the table for moving rocks up the grate, the conveyer including a conveyor frame, sprocket wheels rotatably mounted on the conveyer frame, chains trained over aligned sprocket wheels, conveyer cross bars fixed to the chains at intervals, teeth on the cross bars for engaging and moving rocks up the grate, and means for driving the sprocket wheels, the improvement comprising:
at least one forwardly and upwardly extending member positioned at a rearward end of the conveyer frame which member forms a wedge shaped cavity, such that as large rocks are moved up the grate by the conveyer through the wedge shaped cavity, the rocks engage the member thereby lifting the rearward end of the conveyer frame to provide clearance.

2. An improvement in a rock picking machine having a frame with ground wheels supporting the frame, and embodying a grate over which rocks are moved and discharged into a bucket rearwardly pivotally mounted on the frame, a table on which the grate is mounted being rearwardly pivoted on the frame to be movable between a rock picking position in relation to the ground and a position elevated from the ground, a conveyer forwardly pivotally mounted on the table for moving rocks up the grate, the conveyer including a conveyor frame, sprocket wheels rotatably mounted on the conveyer frame, chains trained over aligned sprocket wheels, conveyer cross bars fixed to the chains at intervals, teeth on the cross bars for engaging and moving rocks up the grate, and means for driving the sprocket wheels, the improvement comprising:
a fixed extension which extends forwardly of the table substantially parallel to the groundsurface when the table is in a rock picking position, the extension rotatably supporting at least one additional sprocket wheel, the additional sprocket wheels which support the chains to which the conveyor cross bars are fixed such that the teeth on the crossbars travel in a substantially horizontal path prior to encountering the grate.

3. An improvement in a rock picking machine having a frame with ground wheels supporting the frame, and embodying a grate over which rocks are moved and discharged into a bucket rearwardly pivotally mounted on the frame, a table on which the grate is mounted being rearwardly pivoted on the frame to be movable between a rock picking position in relation to the ground and a position elevated from the ground, a conveyer forwardly pivotally mounted on the table for moving rocks up the grate, the conveyer including a conveyor frame, sprocket wheels rotatably mounted on the conveyer frame, chains trained over aligned sprocket wheels, conveyer cross bars fixed to the chains at intervals, teeth on the cross bars for engaging and moving rocks up the grate, and means for driving the sprocket wheels, the improvement comprising.
a plurality of forwardly and downwardly extending "F"
shaped ground chisels positioned at the forward end of the table, such that the ground chisels extend below the ground surface to direct rocks below the ground surface to the grate, each of the ground chisels being generally "T" shaped with a top portion that engages soil bearing rocks and a tail portion, a first clearance space being provided between adjacent top portions, a second clearnance space being provided between adjacent tail portions, the second clearance space being larger than the first clearance space such that once a rock passes through the first clearance space increased clearance is encounted in the second clearance space thereby allowing soil to pass through freely and reducing the likelihood of the rock jamming between the adjacent teeth.

4. An improvement in a rock picking machine having a frame with ground wheels supporting the frame, and embodying a grate over which rocks are moved and discharged into a bucket rearwardly pivotally mounted on the frame, a table on which the grate is mounted being rearwardly pivoted on the frame to be movable between a rock picking position in relation to the ground and a position elevated from the ground, a conveyer forwardly pivotally mounted on the table for moving rocks up the grate, the conveyer including a conveyor frame, sprocket wheels rotatably mounted on the conveyer frame, chains trained over aligned sprocket wheels, conveyer cross bars fixed to the chains at intervals, teeth on the cross bars for engaging and moving rocks up the grate, and means for driving the sprocket wheels, the improvement comprising:
a wiper blade secured to each end of the cross bars which extends forward of the teeth, such that the wiper blade directs rocks away from the ends of the cross bar.

5. An improvement in a rock picking machine having a frame with ground wheels supporting the frame, and embodying a grate over which rocks are moved and discharged into a bucket rearwardly pivotally mounted on the frame, a table on which the grate is mounted being rearwardly pivoted on the frame to be movable between a rock picking position in relation to the ground and a position elevated from the ground, a conveyer forwardly pivotally mounted on the table for moving rocks up the grate, the conveyer including a conveyor frame, sprocket wheels rotatably mounted on the conveyer frame, chains trained over aligned sprocket wheels, conveyer cross bars for engaging and moving rocks up the grate, teeth on the cross bar engaging and moving rocks up the grate and means for driving the sprocket wheels, the improvement comprising:
a plurality of spacer members secured to a side of the cross bars opposed to the teeth, thereby presenting rocks of a size sufficient to cause a jamming of the machine from resting upon and being lifted by the opposed side of the crossbars.

6. An improvement as defined in Claim 2, having a plurality of forwardly and downwardly extending "T" shaped ground chisels positioned at the forward end of the table, such that the ground chisels extend into the ground surface to direct rocks below the ground surface to the grate.

7. An improvement in a rock picking machine having a frame with ground wheels supporting the frame, and embodying a grate over which rocks are moved and discharged into a bucket rearwardly pivotally mounted on the frame, a table on which the grate is mounted being rearwardly pivoted on the frame to be movable between a rock picking position in relation to the ground and a position elevated from the ground, a conveyer forwardly pivotally mounted on the table for moving rocks up the grate, the conveyer including a conveyor frame, sprocket wheels rotatably mounted on the conveyer frame, chains trained over aligned sprocket wheels, conveyer cross bars fixed to the chains at intervals, teeth on the cross bars for engaging and moving rocks up the grate, and means for driving the sprocket wheels, the improvement comprising:
each of the teeth on the cross bars for engaging and moving rocks up the grate being generally "T" shaped with a top portion that engages rocks and a tail portion, a first clearance space being provided between adjacent top portions, a second clearance space being provided between adjacent tail portions, the second clearance space being larger than the first clearance space such that once a rock passes through the first clearance space increased clearance is encountered in the second clearance space thereby reducing the likelihood of the rock jamming between the adjacent teeth.