AN IMPROVED JAW CRUSHER

Field of the Invention

The present invention relates to the fields of mining and material processing. More

5 specifically, the present invention is an improved jaw crusher for crushing rocks, ores and other materials down to a specific size.

Background of the Invention

A typical jaw crusher comprises a robust, rectangular, high-grade steel main frame, a steel cast moving jawstock, manganese wear plates, and a heat-treated forged steel eccentric drive shaft driven by two large diameter heavy cast iron balanced flywheels. These latter drive components provide the recommended revolutions and kinetic energy necessary to move the jawstock and crush rock.

15 The production capacity of crushed material for known jaw crushers can vary from 1 to 1500 tons per hr (TPH) and the machine may weigh from 10kg to over 100 tonnes. Known jaw crushers have a generally rectangular main frame designed to accept hard lump rock material at a feed size from 25mm to 1 ,5m. The manganese wear plates are normally secured on the jawstock at an angle of between 75 and 90

20 degrees to the back of the main frame. The jawstock swings through a crushing stroke created by the throw on the eccentric drive shaft. A toggle plate is attached to the bottom of the jawstock, which creates a crushing movement as the eccentric shaft revolves.

25 The jaw crusher has a material feed opening defined between upper ends of the fixed and moving crusher jaws and wear cheek plates which are secured on each side wall of the steel fabricated main frame. These components collectively determine the maximum lump size of hard rock that can enter the top feed access of the crusher. The final TPH and required product size of the crushed material are determined by the dimension between the two side cheek wear plates and the close side setting (CSS) of the moving and fixed crushing jaws. Both sides of the main frame are perpendicular, therefore the inside dimensions between the side plates at the top material access position are the same as the discharge opening defined between the bottom ends of the wear plates on the jaws. The maximum TPH

35 produced by any size or model of jaw crusher is determined and regulated by the dimensions of the CSS and width of the discharge opening at the bottom of the crushing jaws.

A 900 X 600mm model jaw crusher has a material feed opening access of 900 X 600mm. The design of the feeder normally used for this application will deliver more run of mine (ROM) material through the 900 X 600mm feed opening than the crusher can process because the production is regulated by the width of the feed and discharge openings and the CSS of crusher jaws at the bottom of the jawstock and frame. Hence, crushed rock production is compromised by the dimensions of conventional jaw crushers.

The standard energy required to drive this 900 x 600mm model of crusher is normally 75KW for a 980 RPM, 3-phase induction slip ring electric motor. With the power and speed of the motor fixed, and the TPH production of the crusher limited by the dimensions of the openings in the frame, there is little flexibility in the apparatus which would allow any kind of improvement in energy efficiency.

Existing jaw crushers are typically driven by these motors via a direct drive, where a number of drive belts are employed to connect a motor drive pulley and a driven flywheel connected to an eccentric drive shaft. A number of drive belts are employed together in this drive arrangement due to the small diameter of the motor drive pulley, and this dictates that the drive pulley and flywheel must have a significant width in order to accommodate this collection of belts. In addition, the belts must be adjusted to a high tension in order to have sufficient grip. These factors have an adverse effect on the manufacturing and maintenance costs of the crusher.

The diameters of the drive pulley and flywheel are designed and manufactured to suit the drive ratio of such direct drive arrangements, with the limits on the diameters consequently limiting the size of the contact patches for the belts on the pulley and flywheel. Limiting the contact patch limits the grip which the belts have on the drive pulley and flywheel, which again has a detrimental effect on the overall efficiency of the machine. Known jaw crushers also use flat wear plates on the jaws themselves. During crushing operations this can result in crushed material remaining towards the centre of the plates and hence the frame itself. This slows the progress of crushed material out of the bottom of the machine, as well as the entrance of new material to be crushed, both of which also have a negative effect on the productivity of these known machines.

It is an aim of the present invention to obviate or mitigate one or more of the aforementioned disadvantages with existing jaw crusher machines.

Summary of the Invention

According to a first aspect of the invention there is provided a jaw crusher, comprising: a frame defining a feed opening at the top of the frame, a discharge opening at the bottom of the frame, and a crushing volume located between the feed and discharge openings; a fixed jaw and a movable jaw located within the crushing volume, each jaw having a top portion and a bottom portion; and an eccentric drive shaft connected to the moveable jaw so as to impart movement thereto, wherein the feed opening has a first fixed width and the discharge opening has a second fixed width which is greater than the first fixed width, and the fixed jaw and moveable jaw taper outwardly whereby their respective bottom portions are wider than their respective top portions.

Preferably, the second fixed width is at least one third greater than the first fixed width. Most preferably, the second fixed width is at least one third wider, and no more than two times wider than the first fixed width.

Preferably, the crushing volume is partially defined by opposing side walls of the frame, wherein each side wall has an upper portion, an intermediate portion and a lower portion, and wherein the intermediate portions have an outward taper of 15-35° in the downward direction. Most preferably, the intermediate portion of each side wall has an outward taper of 20-25° in the downward direction. Preferably, the upper and lower portions of each side wall are substantially vertical. Alternatively, the upper and lower portions of each side wall have an outward taper of 1-3° in the downward direction.

Preferably, the fixed and moveable jaws each include a detachable wear plate mounted to a crushing surface thereof, each wear plate being formed from a plurality of modular wear plate sections. Preferably, each wear plate is formed from a pair of outerwear plate sections and a central wear plate section located between the outer wear plate sections.

Preferably, each wear plate has a plurality of raised crushing elements and at least one of the fixed jaw and moveable jaw includes a central wear plate section having crushing elements which project further from the crushing surface of the jaw than the crushing elements on the pair of outerwear plate sections.

Preferably, the crushing elements are arranged in columns with a groove formed between adjacent columns of crushing elements, and wherein each crushing element tapers inwardly from top to bottom down a column such that the grooves wider at the bottom of the wear plate than at the top.

Preferably the crushing elements on the moveable jaw wear plates are arranged in rows, and each crushing element in one row is taller than the corresponding crushing element in the row immediately below. Most preferably, each crushing element in one row is 5-10mm taller than the corresponding crushing element in the row immediately below.

The jaw crusher may further comprise a drive system including: an electric drive motor having a motor drive shaft; a transmission having an input connected to the motor drive shaft, and an output; a drive wheel connected to the transmission output; first and second flywheels non-rotatably attached to opposite ends of the eccentric shaft; and one or more drive belts connecting the drive wheel and the first flywheel. Preferably, the top portion of the moveable jaw includes a channel adapted to receive the eccentric drive shaft, and the jaw crusher further comprises a shaft cover which is attached to the top portion of the moveable jaw so as to encapsulate the eccentric drive shaft in the channel.

Preferably, the moveable jaw includes a plurality of first locating apertures, and the frame includes a corresponding plurality of second locating apertures, and the jaw crusher further comprises a plurality of locating members adapted to be inserted into the first and second locating apertures so as to selectively fix the moveable jaw relative to the frame.

Preferably, the first locating apertures and locating members include engagement means so as to lock the locating members in the first locating apertures.

According to a second aspect of the present invention, there is provided a jaw crusher comprising: a frame defining a feed opening at the top of the frame, a discharge opening at the bottom of the frame, and a crushing volume located between the feed and discharge openings; a fixed jaw and a movable jaw located within the crushing volume, each jaw having a top portion and a bottom portion; and an eccentric drive shaft connected to the moveable jaw so as to impart movement thereto, wherein the fixed and moveable jaws each include a detachable wear plate mounted to a crushing surface thereof, each wear plate being formed from a plurality of modular wear plate sections.

Preferably, each wear plate is formed from a pair of outer wear plate sections and a central wear plate section located between the outerwear plate sections.

Preferably, each wear plate has a plurality of raised crushing elements and at least one of the fixed jaw and moveable jaw includes a central wear plate section having crushing elements which project further from the crushing surface of the jaw than the crushing elements on the pair of outerwear plate sections. Preferably, the crushing elements are arranged in columns with a groove formed between adjacent columns of crushing elements, and wherein each crushing element tapers inwardly from top to bottom down a column such that the grooves wider at the bottom of the wear plate than at the top.

Preferably, the crushing elements on the moveable jaw wear plates are arranged in rows, and each crushing element in one row is taller than the corresponding crushing element in the row immediately below. Most preferably, each crushing element in one row is 5-10mm taller than the corresponding crushing element in the row immediately below.

Brief Description of the Drawings

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the following drawings where:

Figure 1 is a perspective view of a jaw crusher;

Figure 2 is an end view of the jaw crusher shown in Figure 1 ;

Figure 3 is a section view of the jaw crusher along the line A-A shown in Figure 2;

Figure 4 is a top view of the jaw crusher shown in Figure 1 ;

Figure 5 is a bottom view of the jaw crusher shown in Figure 1 ;

Figure 6 is a side view of the jaw crusher shown in Figure 1 ;

Figure 7 is a section view of the jaw crusher along the line B-B shown in Figure 6;

Figure 8 is a section view of the jaw crusher in the direction represented by the line D-D shown in Figure 6;

Figure 9 is a section view of the jaw crusher in the direction represented by the line E-E shown in Figure 6;

Figure 10 is an exploded perspective view showing certain components of the jaw crusher during assembly;

Figure 11 is an exploded perspective view showing more components of the jaw crusher during assembly.

Detailed Description of the Drawings

An improved jaw crusher for crushing rock, ores and similar materials is shown in the accompanying figures. The jaw crusher, generally designated 100, comprises a steel main frame 2 having a pair of generally longitudinal side walls 5,7. At one end of the frame 2 is a fixed jaw 8 and at the opposite end of the frame is an end wall 3. The frame 2 is consequently generally cuboidal and has a feed opening 4 at the top of the frame and a discharge opening 6 at the bottom of the frame. The frame 2 may sit upon a base 13 having two pairs of support legs 15,17. Extending from the rear of the fixed jaw 8 are a number of generally horizontal support plates 1 which are attached to the side walls 5,7 to provide support to the fixed jaw.

As with known jaw crushers, the present jaw crusher 1 includes a fixed jaw 8 and a moveable jaw, or jawstock, 10. It is the movement of the jawstock 10 relative to the fixed jaw 8 which crushes the material entering the frame 2 through the feed opening 4. Both the fixed jaw 8 and jawstock 10 are covered by replaceable wear plates 9,11. Each wear plate 9,11 may be a single piece but is preferably modular, as will be described in more detail below. The fixed jaw 8 and jawstock 10 define lateral walls of a crushing volume within the frame 2, and a pair of cheek plates 12 are attached to the inside surfaces of the longitudinal side walls 5,7 of the frame so as to define a pair of longitudinal walls of that crushing volume.

The top of the jawstock 10 is attached to a top bearing cover 14 which houses at least one bearing and an eccentric shaft (not shown in Figure 1). At the outer ends of the top bearing cover 14 are a pair of bearing caps 16 which cover respective bearings for the eccentric shaft. Each of the bearing caps 16 is attached to an upper surface of the side walls 5,7.

Connected to either end of the eccentric shaft are first and second flywheels 18,20. The first flywheel 18 is preferably grooved or otherwise adapted to receive one or more drive belts 22. The other end of the, or each, drive belt 22 is wound around a drive pulley 24, which is driven by an electric motor 26 through a transmission, which may take the form of a reduction gearbox or else a countershaft and drive pulley arrangement (neither shown). The motor 26 is preferably mounted on a motor bracket (not shown) which may be fixed to the frame 2. The drive pulley 24 may include a plurality of fan blades 25 which draw or blow cooling air over the motor 26 and gearbox during operation. The motor has been omitted from the remainder of the figures for illustrative purposes only.

Figure 2 is an end view of the jaw crusher shown in Figure 1. This end view illustrates that the fixed jaw 8 and end wall 3 taper outwards from top to bottom. The jawstock 10 and the wear plates 9,11 associated with the fixed jaw 8 and jawstock also taper outwards in the same manner as the fixed jaw such that they are wider at their respective bases than at their tops. The side walls 5,7 and cheek plates (not shown in Figure 2) attached to the interior surface of the respective side walls each have a concave profile so as to cooperate with the tapered end wall 3, the fixed jaw 8, jawstock 10 and wear plates 9,11 inside the frame 2. As can be seen in Figure 2, that concave profile is made up of three portions of the side walls 5,7 and associated cheek plates: an upper portion II, an intermediate portion I and a lower portion L. The upper and lower portions U,L of the side walls and cheek plates may be substantially vertical, but both portions preferably have an outward taper of 1-3° in the downward direction. In other words, the upper and lower portions U,L of the side walls and cheek plates lie at 1-3° relative to the vertical. The intermediate portions I of the side walls 5,7 and cheek plates preferably have an outward taper of 15-35° in the downward direction, i.e. 15-35° relative to the vertical. Most preferably, the intermediate portions I have an outward taper of 20-25° relative to the vertical.

This tapered arrangement means that the discharge opening 6 at the bottom of the frame 2 is wider than the feed opening 4 at the top of the frame. The feed opening 4 will be of a conventional size, such as 900mm wide by 600mm long, or 1100mm by 800mm, for example. The discharge opening 6 may at least one third wider than the feed opening 4. For example, the feed opening may be 900mm wide and the discharge opening may be 1200mm wide. Alternatively, the discharge opening 6 may be at least one third wider, and no more than two times wider, than the feed opening 4.

Figure 3 is a longitudinal section taken through the jaw crusher 100 along the line A- A shown in Figure 2. This section helps illustrate the various components which make up the complete jawstock assembly in particular. As already described, the feed opening 4 and the discharge opening 6 each have a respective fixed width. However the length, or close side setting (CSS), of the feed and discharge openings 4,6 is variable and is dictated by the angular positioning of the jawstock 10. An eccentric shaft bearing seat, or channel, 29 runs across an upper end of the jawstock 10 and the eccentric shaft 30 is located in the seat and encapsulated by the top bearing cover 14. The angle of the jawstock 10 is adjusted via a toggle plate 40, which has one end attached to a first toggle seat 42 in a lower end of the jawstock and the other end attached to a second toggle seat attached to an adjustment block 44. Adjusting the adjustment block 44 adjusts the longitudinal position of the toggle plate 40 relative to the frame 2. With the longitudinal position of the upper end of the jawstock 10 fixed on account of the eccentric shaft 30 this longitudinal adjustment of the toggle plate 40 will adjust the angle of the jawstock 10. This will also vary the CSS and the overall cross sectional area of the discharge opening 6.

A tensioning assembly is also attached to the lower end of the jawstock 10 so as to provide a the necessary tension required to hold the jawstock firmly against the toggle plate 40 when the lower end of the jawstock undertakes a longitudinal swinging motion, which crushes the rock fed into the crusher. The tensioning assembly comprises a tensioning rod 46 having a first end attached to the jawstock 10, and a second end attached to a tension spring 48. The tension spring 48 is sandwiched between adjustment nuts at the second end of the tensioning rod and a fixed part of the frame 2.

Figure 4 is a top view of the jaw crusher described above, illustrating the fixed width feed opening 4 and the wear plates 9,11 housed within the frame 2. Figure 5 is a bottom view of the jaw crusher, illustrating the fixed width discharge opening 6 and the adjustment and tensioning arrangements for the jawstock 10.

Figure 6 is a side view of the jaw crusher 100, looking at the longitudinal side wall 7. Also visible are the first flywheel 18, the tensioning assembly of rod 46 and spring 48, and the lower edges of the fixed jaw 8 and jawstock 10. Also shown is a lower locating member 50 for the jawstock 10, whose purpose will be explained in more detail below. The lower locating member 50 may be a bolt, rod or other suitable member, and there is a lower locating member provided at the same location on both side walls 5,7, with the side walls including corresponding lower locating apertures through which the locating members 50 may extend into the interior of the frame 2. Figure 7 is a vertical section through the jaw crusher 100 along line B-B shown in Figure 6. This section view gives a clear illustration of the eccentric shaft 30 and the flywheels 18,20 at either end thereof. An upper portion of the angled jawstock 10 is also visible, as are a pair of upper locating members 52. Each side wall 5,7 has an upper locating member 52 to go along with the lower locating member 50 visible in Figure 6. The upper locating member 52 may also be a bolt, rod or other suitable member with the side walls 5,7 including corresponding upper locating apertures through which the locating members 52 may extend into the interior of the frame 2.

The internal cheek plates 12 are also visible in Figure 7, attached to the inside surfaces of the side walls 5,7. Part of the toggle plate 40 can also be seen, along with the adjustment block 44 through which the longitudinal position of the toggle plate is adjusted.

Figure 8 is a section view of the jaw crusher 100 in the direction represented by the line D-D shown in Figure 6. This view shows the wear plate 11 mounted on a mounting surface of the jawstock 10 in more detail. As described above the wear plate 11 may be a single plate having a plurality of ridges or blocks formed on a crushing surface thereof, the latter being the surface of the plate 11 which faces in the direction of the fixed jaw 8 during operation. The wear plate 11 has a pair of outer plate sections 11A, 11 C and a central plate section 11 B which lies between the two outer plate sections on the jawstock 10. In the preferred embodiment illustrated the wear plate 11 is modular as this means that the wear plates, or just sections thereof, can be replaced without having to remove the jawstock. Wear plate sections 11A-11C are formed separately and then mounted individually on the jawstock 10. Irrespective of whether the plate 11 is a single piece or modular, crushing blocks 19B formed on the central plate section 11B may project a greater distance from the mounting surface of the jawstock 10 than crushing blocks 19A.19C provided on the respective outer plate sections 11A, 11 C.

The crushing blocks 19A-19C taper inwardly from the base on the wear plate to a top crushing face. Each block 19A-19C also tapers inwardly from top to bottom in a longitudinal direction (i.e. down the wear plate from top to bottom). This creates grooves 11G running down the wear plate 11 between adjacent blocks with the grooves wider at the bottom of the wear plate than at the top. This allows the smaller parts of the crushed material to flow easily through the jaws. Each block in one row of blocks may also have a different height to the corresponding block in the row immediately above or below that row. Most preferably, the heights of the corresponding blocks decrease with each row moving down the wear plate 11. For example, the blocks in each row may be 5-10mm shorter than those which correspond in the row immediately above. In the illustrated example there are four rows of blocks. The top row of blocks on the wear plate 11 may be 75mm tall, whilst the bottom row of blocks may be 60mm with the second and third rows in between being 70mm and 65mm tall. Most preferably, the blocks in each row are 10mm shorter than the row immediately above. Irrespective of which specific height difference is employed between subsequent rows of blocks, the varying heights of the rows of blocks provides a series of serrations on the wear plates which assists in crushing the rock fed into the crusher.

Figure 9 is a section view of the jaw crusher 100 in the direction represented by the line E-E shown in Figure 6. This view shows the wear plate 9 mounted on a mounting surface of the fixed jaw 8 in more detail. As described above the wear plate 9 may be a single plate having a plurality of ridges or blocks formed on a crushing surface thereof, the latter being the surface of the plate 9 which faces in the direction of the jawstock 10 during operation. The wear plate 9 has a pair of outer plate sections 9A,9C and a central plate section 9B which lies between the two outer plate sections on the fixed jaw 8. In the preferred embodiment illustrated the wear plate 9 is modular so that it, or sections thereof, can be replaced without removing the fixed jaw, with the sections 9A-9C being formed separately and then mounted individually on the fixed jaw 8. Irrespective of whether the plate 9 is a single piece or modular, ridges or blocks 21 B formed on the central plate section 9B may project a greater distance from the mounting surface of the fixed jaw 8 than ridges or blocks 21 A, 21 C provided on the respective outer plate sections 9A,9C.

The crushing blocks 21A-21C taper inwardly from the base on the wear plate to a top crushing face. Each block 21A-21C also tapers inwardly from top to bottom in a longitudinal direction (i.e. down the wear plate 9 from top to bottom). This creates grooves 9G running down the wear plate between adjacent blocks with the grooves wider at the bottom of the wear plate 9 than at the top. This allows the smaller parts of the crushed material to flow easily through the jaws. Each row of blocks may also have a different height to the next row. Most preferably, the heights of the blocks decrease the further down the wear plate 9 they are. In the illustrated example there are four rows of blocks. The top row of blocks on the wear plate 9 may be 75mm tall, whilst the bottom row of blocks may be 60mm with the second and third rows in between being 70mm and 65mm tall.

Figure 10 is an exploded perspective view showing certain components of the jaw crusher 100 during assembly. Due to the greater width of the lower portions of the frame 2 and jawstock 10, the jawstock must be introduced into the frame in a specific manner during assembly of the crusher. It is not possible to simply lower the jawstock 10 into the frame 2 in its operational orientation, i.e. substantially perpendicular to a longitudinal axis of the frame 2, as the lower portion of the jawstock is wider than the upper portion of the frame 2. To introduce the jawstock 10 it must therefore be lowered into the frame 2 from above in an orientation which is generally parallel with the longitudinal axis of the frame 2. The jawstock 10 is lowered until its lower portion has cleared the narrower opening in the upper portion of the frame 2. Once this has occurred the jawstock 10 is rotated about its own longitudinal axis into the operational orientation, whereby its crushing surface is facing in the longitudinal direction of the frame 2. With the jawstock now in the correct operational orientation the channel 29 in the upper surface of the jawstock 10 will be aligned with corresponding niches 31 provided in the upper portions of the side walls 5,7. This then allows the eccentric shaft 30 to be installed in the jawstock channel 29 and side wall niches 31.

In order to allow the eccentric shaft 30, toggle assembly and tensioning assembly to be fitted to it the jawstock 10 needs to be held in position. However, holding the jawstock in position using the lifting gear which was used to lower the jawstock into the frame is not practical, as it would get in the way of the installers and the components being installed. Instead, the lower and upper locating means 50,52 on both side walls are used to hold the jawstock 10 in position.

Each side of the jawstock 10 has upper and lower locating apertures whose positions correspond with the previously described upper and lower locating apertures in the side walls 5,7 of the frame 2. When these jawstock and side wall locating apertures are aligned with one another the jawstock is in the correct installation position. The lower and upper locating members 50,52 can then be inserted from outside the side walls 5,7 through the corresponding locating apertures, thereby temporarily securing the jawstock 10 in position. The locating members 50,52 and/or jawstock may be provided with engagement means to ensure that the locating members cannot be easily removed or dis-located from the jawstock. For example, the locating apertures in the jawstock may be threaded, and the locating members 50,52 may be threaded so as to engage with the threaded locating apertures.

Whilst the jawstock is temporarily held by the locating members 50,52 the top bearing cover 14 and bearing caps 16 can be secured to the jawstock 10 and side walls 5,7 respectively using appropriate mechanical fixtures such as threaded bolts 54. Once the cover 14, caps 16, toggle assembly and tensioning assembly have been installed the locating members 50,52 can be removed as the jawstock is now held in the correct position by the combination of the shaft 30, top bearing cover 14 and toggle plate.

Figure 11 is an exploded perspective view showing more components of the jaw crusher 100 during assembly, and specifically the wear plate 9 when in modular form. As described above, the wear plate 9 has a pair of outer plate sections 9A,9C and a central plate section 9B which lies between the two outer plate sections on the fixed jaw 8. In the modular form shown the plate sections 9A-9C are formed separately and then mounted individually on the fixed jaw 8. The two outer plate sections 9A,9C are installed first as shown in Figure 11 , and then the central section 9B is inserted into the gap provided between the two outer plate sections. If the wear plate 11 for the jawstock 10 is also modular its sections 11A-11C will be installed in a similar manner.

The production capacity of a jaw crusher according to the present invention may vary from 1 to 1500 tons per hr (TPH) of crushed material. The improvements provided in the jaw crusher according to the present invention will increase production capacity in TPH of the crusher by 10-100% depending upon the material being processed. The main improvement comes from increasing the width of the discharge opening by outwardly tapering the lower sections of the fixed jaw and jawstock and contouring the cheek plates and side walls of the frame to accommodate the tapered components. For example, a “900 x 600mm” model jaw crusher has a material feed opening of 900mm wide by 600mm long. By tapering the jaw components and contouring the side walls of the frame it is possible to extend the width of the discharge opening by 150mm at each side. This will divert and allow the crushed material to flow easily and spread evenly across the complete 1200mm width of the discharge opening. This will increase the production of hard rock by 25-30%.

The energy required to drive a typical 900 x 600mm model of crusher is normally 75KW, using a 980 RPM, 3-phase induction slip ring electric motor with a direct drive connection to the crusher flywheel. The crusher of the present invention uses a four pole 1440 RPM motor fitted with a reduction planetary gear box connected to the drive pulley. Alternatively, any electric motor from 1440-2200 RPM could be used. The modified RPM motor drive system may have a soft start system to reduce the initial load current required and may also have a variable speed control, which will allow the operator to adjust the RPM of the eccentric shaft. Replacing a direct drive with a gearbox arrangement allows an increase in the diameter of the drive pulley to give superior grip with a minimum number of drive belts without the need for high tension on the belts and bearings. This allows the width of both the drive pulley and crusher flywheel to be reduced. This will not only make full use of the high RPM motor energy that may be required to compensate for the increased production, but will also cut manufacturing and maintenance costs.

It should be noted that the jaw crusher of the present invention will be much lighter and require fewer kilowatts to produce the same tonnes per hour as a standard model of jaw crusher.

Having the central ridges or blocks on one or both wear plates project further than the outer ridges or blocks on the same plate means that material is spread laterally outwards during a crushing operation, which allows the material to be discharged out of the discharge opening with fewer blockages or restrictions forming in the centre of the crushing volume.

One or both of the fixed jaw and moveable jawstock may be tapered from its respective centre to the outside edges thereof. Other modifications and improvements may be incorporated without departing from the scope of the present invention.