SELF-PROPELLED STONE CRUSHER

Abstract

 A self-propelled stone crusher constructed so that it can be operated even on the soft ground without lowering of the travelling performance thereof, can remove by itself such a large stone that cannot be crushed therewith, and crush stones as it excavates the superficial earth. This crusher is provided with a blade (17) fixed to the front portion of a crusher body (10), which has a crawler type driving unit (15), in such a manner that the blade (17) can be vertically moved, and a stone crushing unit (20) fixed to the rear end portion of the crusher body (10) with respect to the travelling direction of the stone crusher so that the stone crushing unit (20) can be detached and vertically moved. This unit (20) has a rotary drum (27) which is supported rotatably on both side plates (21a,21a) of a cover member (21) opened toward the ground surface and which is provided with a plurality of bits (29) on the outer circumferential surface thereof; a repulsive plate unit (40), a gra­nulating plate unit (41) and a sorter (42) which are arranged in a mutually spaced manner in the mentioned order in the rotational direction of the rotary drum (27) and fixed to the inner surface of the cover member (21) so that these units can crush stones in cooperation with the rotary drum (27).

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a self-propelled stone crusher for crushing dispersed stones on and under ground during leveling operation of agricultural ground and the like, and more particularly to a self-propelled stone crusher so constructed as to: be operated even on the soft ground without lowering its traveling perform­ance; remove by itself such a large stone that can not be crushed therewith; and crush stones as it excavates the superficial earth of the ground.

[0002] In addition, the self-propelled stone crusher of the present invention also performs the function of leveling the ground after stones are crushed.

DESCRIPTION OF THE PRIOR ART

[0003] As shown in Fig. 1 of the accompanying drawings, known at present is a conventional self-propelled stone crusher such as one made by Willy Bald Co., West Germany, which one is provided with a crusher 2 in its rear end portion with respect to a traveling direction of its wheel type vehicle 1 which pulls the crusher 2 in opera­tion to enable the crusher 2 to crush stones dispersed on and under the ground of agricultural field and the like up to a predetermined depth of the ground.

[0004] In such a conventional self-propelled stone crusher, since the crusher 2 is pulled by the wheel type vehicle 1, the crusher 2 is poor in traveling performance on soft ground, and, therefore can not efficiently crush stones dispersed in the soft ground.

[0005] The crusher 2 is constructed of: an excavator 3 for picking up the stones; and a hammer rotor 4 for hitting the thus picked up stones at a headlong speed to crush the same. When the blades of the excavator 3 are worn, the hammer rotor 4 directly hit large stones dispersed on the ground as it moves downward. As a result, large crushing reaction is produced in the hammer rotor 4 at this time, which reaction must be borne on a rotary shaft 5 of the hammer rotor 4. In other words, the rotary shaft 5 must be firmly mounted in the crusher 2. In addi­tion, in the crusher 2, large stones must be removed manually or by the use of stone picker, which cuts down efficiency in stone crushing operation or work of the crusher 2.

[0006] In addition, penetration depth of the excavator 3 of the crusher 2 is relatively small to make it diffi­cult for the crusher 2 to crush stones having covered with a relatively thick superficial earth of the ground.

[0007] Furthermore, in the crusher 2, since only rota­tional motion of the hammer rotor 4 contributes to stone-­ crushing operation or work of the crusher 2, the crusher 2 is relatively poor in stone-crushing efficiency.

SUMMARY OF THE INVENTION

[0008] In view of such circumstances of the prior art, the present invention was made. It is a first object of the present invention to provide a self-propelled stone crusher so constructed as to: be operated on the soft ground without lowering its traveling performance; remove by itself uncrushable large stones; and crush stones as it excavates the superficial earth of the ground.

[0009] It is a second object of the present invention to provide a self-propelled stone crusher which can levels the ground after the stones dispersed on and under the ground are crushed.

[0010] It is a third object of the present invention to provide a stone crusher which is excellent in stone-­crushing efficiency while detachably mounted on a rear-end portion of a crawler type construction vehicle such as a bulldozer.

[0011] In order to achieve the first object of the pre­sent invention, according to the first embodiment of the present invention, there is provided:
a self-propelled stone crusher vehicle comprising: a blade so mounted on a front portion of a vehicle body of the crusher vehicle as to be vertically movable, the vehicle body being provided with a crawler type traveling portion; and a stone crusher detachably mounted on a rear-end portion of the vehicle body with respect to a traveling direction of the vehicle body so as to be vertically movable.

[0012] In order to achieve the second object of the present invention, according to the second embodiment of the present invention, there is provided;
the self-propelled stone crusher vehicle as set forth in the above first embodiment, wherein: the stone crusher further comprises a sheet of ground leveling means mounted on its rear-end portion.

[0013] Further, in order to achieve the third object of the present invention, according to the third embodi­ment of the present invention, there is provided:
a stone crusher comprising: a cover member so detachably connected to a rear-end portion of a crawler type con­struction vehicle through a connecting means as to be vertically movable; a rotary drum which is rotatably mounted on opposite-side portions of the cover member while detachably provided with a plurality of bits in its outer peripheral surface; repulsive plate means which cooperate with the rotary drum to perform the function of crushing stones, the repulsive plate means being so disposed in an inner surface of the cover member as to be spaced apart from each other and as to be sequentially fixed to the inner surface of the cover member in a rota­tional direction of the rotary drum; a granulating plate means; a sorter means; and a rotary-drum driving mechanism mounted on an outside of the cover member.

[0014] The above objects, other objects, embodiments and advantages of the present invention will be apparent to those skilled in the art from the following description considered in connection with the accompanying drawings, submitted for purposes of illustration of the preferred embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 

Fig. 1 is a schematic side view of an example of a conventional stone crusher;

Figs. 2, 3 and 4 are a schematic side, a plan and a rear view of an embodiment of a stone crusher vehi­cle of the present invention, respectively;

Fig. 5 is a schematic longitudinal sectional view of an embodiment of a stone crusher of the present invention;

Fig. 6 is a schematic longitudinal sectional view of another embodiment of the stone crusher of the present invention, for illustrating an essential part of such another embodiment;

Figs. 7 and 8 are a front and a side view of a rotary drum incorporated in the stone crusher shown in Figs. 5 and 6, respectively;

Figs. 9 and 10 are a schematic longitudinal sec­tional and a schematic side view of a rotary-drum driving mechanism, respectively;

Figs. 11, 12 and 13 are schematic plan views of a repulsive plate, a granulating plate and a sorter mechanism all of which are mounted in the stone crusher, respectively;

Figs. 14 and 15 are schematic perspective views of the repulsive plate means and the granulating plate means, respectively;

Fig. 16 is a longitudinal sectional view of a lever-element mounting portion of the granulating plate means;

Fig. 17 is a longitudinal sectional view of the stone crusher, for illustrating stone crushing operation or work thereof;

Fig. 18 is a schematic perspective view of another embodiment of the present invention, for illustrating a back portion of such another embodiment of the present invention;

Figs. 19A, 19B and 19C are side views of such another embodiment of the present invention shown in Fig. 18, for illustrating action of such another embodi­ment of the present invention;

Fig. 20 is a graph illustrating the entire parti­cle size distribution of an agricultural field before and after execution of work or stone crushing test;

Fig. 21A is a sectional view of the agricultural field, for illustrating conditions of the surface and the interior of the agricultural field before stone crush­ing test is conducted; and

Fig. 21B is a sectional view of the agricultural field, for illustrating conditions of the surface and the interior of the agricultural field after completion of stone crushing test.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinbelow, embodiments of the present invention will be described in detail with reference to the accompa­nying drawings.

[0017] In the first place, as shown in Figs. 2 to 4, a track frame 11 is mounted on each of opposite sides of a vehicle body 10 of a crawler type construction vehi­cle "A". A crawler track 14 runs round an idler wheel 12 and a sprocket wheel 13. These wheels 12 and 13 are disposed in a front and a rear portion of the track frame 11. A crawler type traveling portion 15 of the construc­tion vehicle "A" has the above construction in which the sprocket wheel 13 is connected to an engine (not shown) through suitable transmission gears (not shown) such as a final reduction gear, a steering clutch/brake unit, a speed-change gear and a torque converter.

[0018] A blade arm 16 is so connected to the track frame 11 as to be vertically swingable. A blade 17 is pivotally mounted on a front end of the blade arm 16. A lift cylin­der 18 is so interposed between the blade 17 and a vehicle body 10 as to be rotatably connected therewith. In addi­tion, a fertilizer distributer 19 is detachably mounted on the blade 17.

[0019] The reference numeral 20 denotes a stone crusher which is so detachably mounted on a rear end of the vehi­cle "A" as to be vertically swingable.

[0020] As shown in Fig. 5 in detail, the stone crusher 20 is provided with a cover member 21 which opens to the ground. A bracket 23 is detachably mounted on the cover member 21 by means of bolts 22. On the other hand, another bracket 24 is mounted on a rear portion of the vehicle body 10. Both of a link 25 and a cylinder 26 are so interposed between theses brackets 23 and 24 as to be rotatable relative to them to enable the bracket 23 to vertically swing. Between opposite side plates 21a, 21a of the cover member 21 is rotatably mounted a rotary drum 27 made of iron. As shown in Figs. 7 and 8, a plurality of bit-mounting base members 28 are so fixedly mounted on an outer peripheral surface of the rotary drum 27 as to be spaced apart from each other in both of a circumferential and an axial direction of the rotary drum 27. A conical bit 29 is detachably mounted on each of these bit-mounting base members 28. The rotary drum 27 is connected to a motor 31 through a rotary-drum driving mechanism 30.

[0021] As shown in Figs. 1, 9 and 10, the above rotary-­drum driving mechanism 30 is provided with a case 32 which is mounted on one of the opposite side plates 21a, 21a of the cover member 21. The motor 31 is fixedly mounted on an upper portion of the case 32. A power-output shaft 31a of this motor 31 is connected to a rotary-drum driving shaft 36 through an upper sprocket wheel 33, chain 34 and a lower sprocket wheel 35. Consequently, the rotary drum 27 is rotatably driven by the motor 31 in the direction of the arrow shown in each of Figs. 5 and 8.

[0022] In addition, sequentially mounted in an inner wall of the cover member 21 are : a repulsive plate unit 40, a granulating plate unit 41 and a sorter mechanism 42 so as to be spaced apart from each other in a rota­tional direction of the rotary drum 27, whereby these components cooperate with the rotary drum 27 to perform the function of crushing stones. On the other hand, a cover plate 43 is mounted on a rear portion of the cover member 21.

[0023] Incidentally, shown in Fig. 6 is another embodi­ment of the repulsive plate unit 40 in which: a base plate 40c is inclined upward relative to the ground (so as to be parallel to the cover member 21). A plurality of bits 40d are so fixedly mounted on the base plate 40 as to be directed toward the ground.

[0024] In case that the repulsive plate 40 has the con­struction shown in Fig. 6, stones having been hit at a position of a point D collide against the bits 40d to make it possible to improve stone-crushing efficiency in comparison with the embodiment shown in Fig. 5 in which the stones having been hit collide merely against the flat plate.

[0025] As shown in Fig. 14, the number of the repulsive plate unit 40 shown in Fig. 5 is plural and arranged in a front portion of the inner surface of the cover member 21 with respect to the traveling direction of the vehicle "A". Each of such repulsive plate units 40 is provided with: a mounting plate 44 which is so mounted on the inner surface of the cover member 21 through a plurality of bolts/nuts 46 as to be movable along the inner surface of the cover member 21 over a predetermined wide range in the traveling direction of the vehicle "A" or in a direction counter to the traveling direction; and a repulsive plate 40a a base end of which is fixed to the mounting plate 44 through a longitudinal plate 45 to enable the repulsive plate 40a to be oppositely disposed from a path of each of the bits 29 through a suitable clearance. Incidentally, the above-mentioned predetermined wide range of adjustable distance of the mounting plate 44 depends on a longitudinal diameter of an elongated hole 44a of the mounting plate 44, in which elongated hole 44a is inserted a bolt of the bolts/nuts 46.

[0026] In addition, as shown in Fig. 11, the repulsive plate 44a is provided with a plurality of concave portions 40b in its front-end surface which is oppositely disposed from the rotary drum 27.

[0027] In the repulsive plate unit 40 having the above construction, as is clearly understood from Figs. 5 and 6, when the bolts/nuts 46 are loosened and then an adjust­able screw 47 is rotatably driven clockwise or counter­clockwise, it is possible to move the repulsive plate 40a relative to the cover member 21 as described above, whereby the operator of the vehicle "A" can control the clearances between the paths of the bits of the rotary drum 27 and the repulsive plates 40a according to stone distribution conditions ( stone size, stone particle distribution pattern, stone content and the like ) of the ground.

[0028] As shown in Fig. 12, also in a front-end surface of a granulating plate 41a of the granulating plate unit 41 are formed a plurality of concave portions 41b which are oppositely disposed from the rotary drum 27. Further, as shown in Fig. 5, a base-end portion of the granulating plate 41a is rotatably mounted on the inner surface of the cover member 21 through a pin 48. In addition, in order to make it possible to control the clearances be­tween the paths of the bits 29 of the rotary drum 27 and the front-end surface of the granulating plate 41a, a lever element 49 is so provided as to be vertically movably supported by the cover member 21, a lower end of the lever element 49 being connected to a front-end portion of the granulating plate 41a. By extending or retracting the lever element 49 vertically, the granulat­ing plate 41a is vertically rotated on the pin 48 (in Fig. 5, the lever element 49 is rotated clockwise or counterclockwise) so that the clearances between the paths of the bits of the rotary drum 27 and the front-end surface of the granulating plate 41a are controlled. As shown in Fig. 16, the lever element 49 is mounted on an outer surface of the cover member 21, and extends into the interior of a sleeve element 50 a bottom of which is opened so that an upper-end screw portion 49a of the lever element 49 extends outward from the bottom opening of the sleeve element 50, whereby the upper-end screw portion 49a of the lever element 49 is threadably engaged with a nut 51. As a result, the lever element 49 is resiliently urged downward under the influence of a compression spring 52 which is interposed between the inner surface of the sleeve element 50 and a large-­diameter portion 49b provided in an intermediate portion of the lever element 49. When the nut 51 is rotated, the lever element 49 is vertically moved to enable the granulating plate 41a to rotate on the pin 48 so as to be vertically swung on the pin 48, whereby the clearances between the bits 29 of the rotary drum 27 and the front end of the granulating plate 41a are suitably adjusted.

[0029] As shown in Fig. 13, the above-mentioned sorter mechanism 42 is provided with a plurality of longitudinal levers 42a which are so arranged as to be spaced apart from each other in a direction perpendicular to the trav­eling direction of the vehicle "A".

[0030] Now, stone crushing operation or work of the stone crusher will be described in detail with reference to Fig. 17.

[0031] When the rotary drum 27 is rotatably driven, the bits 29 of the rotary drum 27 crush stones dispersed in the ground. At this time, some of the stones dispersed under the ground are picked up on the ground by the bits 29 as the rotary drum 27 rotates.

[0032] The stones, which are still not crushed under the ground and picked up on the ground, collide against the repulsive plates 40a and also against the bits 29 of the rotary drum 27 again so as to be subjected to a secondary crushing operation or work under the influ­ences of shearing/compression forces and impacts caused by these components.

[0033] At this time, the stones picked up by the bits 29 fixedly mounted on the outer peripheral surface of the rotary drum 27 are prevented from being scattered so that the stones are repeatedly subjected to the shearing/compression forces and impacts caused by the bits 29 and the repulsive plates 40a, whereby the stones are efficiently crushed.

[0034] The stones thus crushed by the repulsive plates 40a and the bits 29 further collide against the granulat­ing plate 41a so as to be directed upward. As a result, the thus crushed stones hit again both of the bits 29 and the repulsive plates 40a to make it possible to re­peatedly crush or granulate the stones between the repul­sive plates 40a and the granulating plate 41a.

[0035] Namely, the granulating plate 41a is substantially horizontally mounted substantially immediately on the rotary drum 27 so as to increase a space between itself and the the repulsive plates 40a to the maximum extent. In addition, the granulating plate 41a so directs the stones having collided against it as to hit again the bits 29 of the rotary drum 27. In this case, the front end of the granulating plate 41a, which front end is oppositely disposed from the rotary drum 27, is curved downward so as to make it complicated to pass the stones, whereby the number of collisions of the stones between the bits 29 and the stones are increased. When the lever element 49 is rotated, the granulating plate 41 is verti­cally swung on the pin 48 provided in its base-end portion to make it possible to adjust the clearances between the paths of the bits 29 of the rotary drum 27 and the front end of the granulating plate 41a according to an amount of the stones being crushed. On the other hand, as shown in Fig. 16, since the lever element 49 is urged downward under the influence of the compression spring 52, the granulating plate 41a performs the function of damping the impacts of the stones when it is hit by the stones. Incidentally, the granulating plate 41a may be vertically swung by means of a suitable cylinder (not shown).

[0036] Then, the thus granulated stones pass rearward through the longitudinal levers 42a, 42a which constitute the sorter mechanism 42 in which the longitudinal levers 42a, 42a are spaced apart from each other at predetermined intervals. At this time, the stones which can not pass through the sorter mechanism 42 collide against the longi­tudinal levers 42a, 42a so as to be rebounded toward the bits 29 of the rotary drum 27. As a result, the thus rebounded stones are hit again by the bits 29 while buried under the ground by the bits 29. Consequently, the granu­lated stones are disposed in an upper layer of the ground, while the stones which are still not sufficiently crushed are crushed again by the bits 29 of the rotary drum 27 and buried in a lower layer of the ground of the agricul­tural field.

[0037] According to further another embodiment of the present invention, as shown in Fig. 18, a ground leveling plate 53 is mounted on a rear end of the cover member 21 of the stone crusher 20.

[0038] In other words, the rear portion cover plate 43 of the stone crusher 20 is vertically swingably mounted on the pin 54 through a bracket. Other brackets 55, 55 are fixed to opposite sides of the cover plate 43. On these brackets 55, 55, the ground leveling plate 53 is vertically swingably mounted through a supporting axle 56. On opposite ends of the supporting axle 56 are fixed a pair of levers 57, 57 each of which extends in the traveling direction of the vehicle "A" along the side portion of the cover plate 43 so as to be disposed at a substantially right angle relative to a pendulous por­tion of the ground leveling plate 53. In a position corre­sponding to an upper position of a front end of each of the levers 57, 57 is extended a front end of each of rods 58 which are fixedly mounted on opposite side portions of an upper surface of the cover plate 43. These rods 58, 58 are connected with the above levers 57, 57 through springs 59, 59 which keep the pendulous portion of the ground leveling plate 53 vertical.

[0039] As a result, as shown in Fig. 19A, in case that the ground is excavated shallowly, the pendulous portion of the ground leveling plate 53 is kept substantially vertical. On the other hand, in case that the ground is excavated deeply as shown in Fig. 19B, the ground leveling plate 53 is rotated on the supporting axle 56 so as to be swung upward ( i.e., so as to be rotated counterclockwise in Fig. 19B) against tensile forces exerted by the springs 59, 59. When a large amount of earth and crushed stones are deposited within the cover member 21 during excavation of the ground, i.e., when the ground leveling plate 53 is subjected to overload, as shown in Fig. 19C, the ground leveling plate 53 is further swung upward to clear a dead point of an assembly of the levers 57, 57 and the springs 59, 59.

[0040] As described above, the ground leveling plate 53 is so swung as to always keep a moment: P x A (see Fig. 19A) constant, which moment acts on the ground level­ing plate 53 having been swingably supported on the sup­porting axle 56 under the influence of the tensile forces of the springs 59, 59. Consequently, an earth pressure distribution in the cover member 21 is kept substantially constant regardless of the amount of the earth and crushed stones deposited within the cover member 21.

[0041] On the other hand, when the large amount of earth and crushed stones are deposited within the cover member 21 to considerably increase a traction load of the vehicle "A", i.e., in overload conditions of the vehicles "A", as shown in Fig. 19C, the ground leveling plate 53 is swung extremely upward to reduce a traction resistance caused by such large amount of earth and crushed stones deposited within the cover member 21.

[0042] Advantages inherent in the stone crushing opera­tion or work conducted by the self-propelled stone crusher of the present invention described in the above in detail are as follows:

[0043] Immediately before the stone crusher 20 conducts its stone crushing operation or work, the superficial earth of the ground is excavated by the blade 17 mounted on the front end portion of the crawler type construction vehicle "A" and uncrushable stones exceeding a predeter­mined size are removed. consequently, stone crushing efficiency of the self-propelled stone crusher vehicle "A" of the present invention is remarkably improved. In addition, in the vehicle "A" of the present invention, there is no fear that the stone crusher 20 is subjected to overload conditions. In addition, the vehicle "A" of the present invention does not require any preparatory work for removing large stones manually or by the use of other construction vehicles, which preparatory work is hitherto required. As a result, the vehicle "A" of the present invention is remarkably improved in operation effectiveness too.

[0044] Furthermore, in the vehicle "A" of the present invention, since its stone crushing operation or work is conducted immediately after the superficial earth of the ground is excavated, it can crush the stones dis­persed in a relatively deep portion of the ground having been covered with a thick superficial earth.

[0045] Results of tests for demonstrating the above advantages of the vehicle "A" of the present invention are shown in Figs. 20, 21A and 21B.

[0046] Fig. 20 is a graph illustrating the entire parti­cle size distribution of the ground of agricultural field before and after execution of work or stone crushing operation. As is clearly understood from this graph, a cumulative weight percentage of stone particle size of from 25 to 150 mm of the ground after execution of work is improved by about 10 % relative to that of the ground before execution of work.

[0047] In Figs. 21A and 21B, there are shown sectional views of the ground of agricultural field: illustrating conditions of the surface and the interior of the ground of agricultural field before stone crushing tests are conducted; and illustrating conditions of the surface and the interior of the agricultural field after comple­tion of stone crushing tests, respectively. As is clear from Fig. 21B, after execution of work or stone crushing operation by the use of the vehicle "A" of the present invention, substantially no stone remains in the superfi­cial earth and the upper layer portion of the ground.

Claims

1. A self-propelled stone crusher vehicle comprising:
a blade so mounted on a front portion of a vehicle body of said crusher vehicle as to be vertically movable, said vehicle body being provided with a crawler type traveling portion; and a stone crusher detachably mounted on a rear-end portion of said vehicle body with respect to a traveling direction of said vehicle body so as to be vertically movable.

2. The self-propelled stone crusher vehicle as set forth in claim 1, wherein: said stone crusher further comprises a ground leveling means which is mounted on its rear-end portion with respect to said traveling direc­tion of said vehicle body so as to be vertically swingable.

3. A stone crusher comprising: a cover member detach­ably connected to a rear-end portion of a crawler type construction vehicle with respect to a traveling direction of said crusher through a connecting means so as to be vertically movable; a rotary drum which is rotatably mounted on opposite-side portions of said cover member while detachably provided with a plurality of bits in its outer peripheral surface; repulsive plate means which cooperate with said rotary drum to perform the function of crushing stones, said repulsive plate means being so disposed in an inner surface of said cover member as to be spaced apart from each other and as to be sequen­tially fixed to said inner surface of said cover member in a rotational direction of said rotary drum; a granulat­ing means; a sorter means; and a rotary-drum driving mechanism mounted on an outside portion of said cover member.

4. The stone crusher as set forth in claim 3, wherein each of said repulsive plate means comprises: a mounting plate which is provided with a plurality of elongated holes so as to be movable over a predetermined distance along an inner surface of said cover member in said trav­eling direction of said vehicle body or in a direction counter to said traveling direction, said mounting plate being mounted on said cover member through a plurality of bolts/nuts inserted into said elongated holes of said mounting plate; and a repulsive plate which has its base end fixed to said mounting plate through a longitudinal plate and has its front-end surface oppositely disposed from paths of said bits mounted on said rotary drum.

5. The stone crusher as set forth in claim 3, wherein said granulating plate means comprises a granulating plate which has its base-end portion mounted rotatably on an inner surface of said cover member through a pin, and which plate is connected to a lower end of a lever element means supported by said cover member so as to have its front-end portion be vertically rotatable on said pin to make it possible that said front-end portion of said granulating plate oppositely disposed from said paths of said bits of said rotary drum is vertically movable.

6. The stone crusher as set forth in claim 3, wherein: said sorter means is constructed of a plurality of longitudinal levers which are spaced apart from each other in a direction perpendicular to said traveling direction of said crawler type construction vehicle.

7. The stone crusher as set forth in claim 4, wherein: said repulsive plate is provided with a plurality of concave portions in its front-end surface.

8. The stone crusher as set forth in claim 5, wherein: said granulating plate is provided with a plural­ity of concave portions in its front-end surface.

9. The stone crusher as set forth in claim 5, wherein said lever element means comprises: a sleeve element mounted on an outer surface of said cover member; a lever element which passes through said cover member and is provided with a screw portion in its upper end extending upward from an upper portion of said sleeve element, a lower end of said lever element being connected to a front-end portion of said granulating plate; a nut means threadably engaged with said screw portion of said lever element; and a compression spring for urging said lever element downward, said compression spring being interposed between an inner surface of said sleeve element and a large-diameter portion of said lever element, which large-diameter portion is formed in an intermediate por­tion of said lever element.

Drawing