Compression crusher having an optimized jaw configuration

A compression type crusher which is adapted to compressingly crush feed material in a crushing chamber formed between movable and stationary crusher plates, the crusher being characterized in that the crushing chamber is shaped such that at least one of the side walls of the crushing chamber defined by the movable and stationary crusher plates inclines away from a vertical line in an inlet region of the crushing chamber and approaches the vertical line in an outlet region of the crushing chamber.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to improvements in compression type crushers such as 
cone crusher, gyratory crusher and jaw crusher, and more particularly to a 
crusher with a crushing chamber of an improved shape which can attain a 
high reduction ratio. 
2. Description of the Prior Art 
The reduction rate in a closed circuit of conventional crushers is at most 
about 5 to 6 owing to overcompression or blocking of material in the 
crushing chamber. The term "reduction ratio" as used in this specification 
means the dimensional ratio of the material before and after the crushing 
operation. In order to obtain a product of a given size, it has been the 
usual practice in the conventional crushing plants to process the material 
progressively through a number of stages, e.g., through first to third 
crushing stages. The improvement of the reduction ratio is a matter of 
great importance to the compression type crusher since it will lead to the 
reduction of the operation time and the enhancement of the operational 
efficiency. The conditions for the improvement of the reduction ratio 
include the fact that: (1) the material should be subjected to sufficient 
crushing forces; (2) the maximum size of the product should be reduced; 
(3) a material of a large size can be fed through the inlet of the 
crushing chamber; and (4) the crushing chamber can be filled with the 
material, permitting the so-called choke feed to ensure stabilized 
operation and higher efficiency. In order to satisfy these conditions, it 
is necessary to design the crushing chamber to be of a shape with a broad 
inlet and a narrow outlet, which is, however, unsuitable for application 
to conventional crushers in consideration of the drop in the production 
speed and the overcompression which would result from blocking of the 
crushing chamber by the feed material. Further, the quantity and speed of 
the oscillatory movement of the crusher plate need to be determined with 
consideration of the behavior of the material in the crushing chamber, in 
appropriate ranges which are contributive to the enhancement of the 
reduction ratio, in relation to the shape of the crushing chamber. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a crusher which can 
overcome the above-mentioned limits of reduction ratio in the conventional 
crushers, and, more specifically, which can attain a reduction ratio 
greater than 12. 
A more specific object of the present invention is to provide a crusher 
with a crushing chamber which is formed in a particular shape determined 
in relation with the quantity and speed of the movable crusher plate and 
the behaviors of feed material in the crushing chamber. 
It is another object of the present invention to provide a jaw crusher with 
a crushing chamber as mentioned above, which is further provided with an 
assembly for fixedly mounting a toggle seat block. 
It is still another object of the present invention to provide a jaw 
crusher with an improved crushing chamber as mentioned above, which is 
further provided with a swing jaw opening mechanism for ejecting stuck 
material from the crushing chamber. 
It is a further object of the present invention to provide a jaw crusher 
with an improved crushing chamber as mentioned above, which is further 
provided with a tension rod spring adjusting mechanism. 
According to a fundamental aspect of the present invention, there is 
provided a compression type crusher which is adapted to compressingly 
crush feed material in a crushing chamber formed between movable and 
stationary crusher plates, the crusher being characterized in that said 
crushing chamber is shaped such that at least one of the side walls of the 
crushing chamber defined by the movable and stationary crusher plates 
inclined away from a vertical line in an inlet region and approaches the 
vertical line in an outlet region of the crushing chamber. 
The above and other objects, features and advantages of the present 
invention will become apparent from the following description and the 
appended claims, taken in conjunction with the accompanying drawings which 
show by way of example some illustrative embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The high reduction ratio attained by the construction according to the 
present invention is firstly explained by comparison with the conventional 
counterpart. Referring first to FIG. 1, there is diagrammatically shown a 
crushing chamber of a conventional cone crusher, including a movable 
crusher plate 1 which is reciprocally oscillated between a solid line 2 
and a double-dot chain line 3 to compressingly crush rocks or other 
material which is fed into the crushing chamber between the movable 
crusher plate 1 and a stationary crusher plate 4 through an inlet 6. The 
crushed material is discharged through an outlet 7 at the bottom of the 
crushing chamber 5. Now, in explanation of the behaviors of the feed 
material, the crushing chamber 5 is divided by a plurality of horizontal 
planes, including a certain horizontal plane Li intersecting the solid 
line 2 at point Pi and a horizontal plane Li-1 containing a point of 
intersection Qi of the chain line 3 with a vertical line extending from 
the point of intersection Pi, defining a level L.sub.0, a level L.sub.1, a 
level Li . . . a level successively from the inlet portion of the crusher 
5. The volume Vi+1 between the levels Li and Li+1 are compressed to Vi by 
the oscillatory motion of the movable crusher plate 1 in the direction of 
the arrow 8, and then dropped between the levels Li-1 and Li by the 
oscillatory motion in the direction of arrow 9. The crusher capacity C 
(e.g., m.sup.3 /h) as determined by the passing rate of the raw material 
which is crushed in the above-described manner has a distribution as shown 
in FIG. 2 at the respective levels of the crushing chamber. The maximum 
value C.sub.M of the crusher capacity C appears slightly inward of the 
inlet 6 of the crushing chamber, while the minimum value Cm exists 
slightly inward of the outlet 7. In order to permit choke feed, the value 
of Cm/C.sub.M has to be greater than 0.77, but experience teaches that it 
becomes difficult to satisfy the condition of Cm/C.sub.M .gtoreq.0.77 if 
the displacement and speed of the oscillatory motion become too large. The 
reason for this is now explained by way of FIG. 3 in which the crushing 
plates 1 and 4 are formed in flat planes for the simplification of 
explanation. In this instance, the stationary crushing plate 4 is 
considered to be disposed in a vertical plane and the movable crushing 
plate 1 is inclined by an angle .theta. with respect to a vertical line. 
The crushing chamber 5 has a width S1 at the level L1 and a width Si at 
the level Li. The levels L.sub.1 and L.sub.0 and the levels Li and Li-1 
are spaced from each other by distances h.sub.1 and h.sub.i, respectively, 
through which the material is dropped by the oscillatory movement of the 
crushing plate 1. More specifically, the material is dropped freely 
through the distance h.sub.i by the oscillatory movement after it is 
crushed at the level L.sub.i, taking a time t.sub.i which has a 
relationship with the distance h.sub.i as expressed by the following 
equation 
##EQU1## 
wherein g is the gravitational acceleration. Therefore, the dropping time 
is 
##EQU2## 
and the speed N of oscillatory motion which can attain the drop of that 
amount is 
##EQU3## 
As seen in FIG. 3, the dropping distances h.sub.1, h.sub.2 . . . in the 
illustrated example are increased stepwise toward the outlet 7 of the 
crushing chamber. Therefore, if the speed of oscillatory motion is 
determined on the basis of the dropping distance h.sub.i at the level Li, 
the material at the level L.sub.1 is gripped again between the crushing 
plates 1 and 4 without dropping by the distance h.sub.1. Accordingly, a 
high speed oscillatory motion will result in a lower crushing capacity 
Cm/C.sub.M at the outlet portion of the crushing chamber. This is the 
reason why the crusher capacity Cm/C.sub.M is lowered when the speed of 
the oscillatory motion is raised an excessive degree. The distance h.sub.i 
is determined by the amount of the radial displacement, namely, the 
oscillatory displacement of the crusher plate 1 about an upper fulcrum 
point 10, the extent of the radial displacement increasing toward the 
outlet of the crusher chamber along with the dropping distance h. Thus, it 
will be easily understood that the increase in the amount of the radial 
displacement reduces the crusher capacity Cm/C.sub.M similarly to the 
speed of oscillatory movement. Consequently, since the production speed is 
determined by neither the speed nor the amount of the oscillatory 
movement, it is disadvantageous to hold them at excessively low values. 
The above-discussed theory relative to the speed and displacement of the 
oscillatory motion is applicable only to a crushing chamber of the shape 
as shown in FIG. 3, and it is considered that the appropriate ranges of 
the speed and amount of oscillatory movement change depending upon the 
shape of the crushing chamber. 
Nextly, considerations are given to the influences of the shape of the 
crushing chamber on the reduction ratio to determine the ideal shape of 
the crushing chamber. The width Si at the level Li of the crushing chamber 
shown in FIG. 3 is 
##EQU4## 
which l.sub.i is the length of the crushing chamber from the fulcrum point 
10 to the level Li. On the other hand, the crusher capacity Ci at the 
level Li is expressed by 
##EQU5## 
while the crusher capacity C.sub.1 at the level L.sub.1 is expressed by 
C.sub.1 =H.S.sub.1.h.sub.1. If the oscillatory speed N in Eq. (i) is set 
at N=60/(t.sub.i /2), h.sub.1 =h.sub.i, and accordingly the ratio 
Ci/C.sub.1 is expressed by 
##EQU6## 
Thus, if the gap width at the outlet of the crusher chamber is narrowed, 
that is to say, if the value of S.sub.1 is minimized for improvement of 
the reduction ratio, the value of Ci/C.sub.1 becomes greater and the value 
of its invested ratio C.sub.1 /Ci becomes smaller. In a case where C.sub.1 
=Cm and Ci=C.sub.M, difficulties are encountered in maintaining Cm/C.sub.M 
.gtoreq.0.77 when the outlet gap width S is reduced, as will be understood 
from the foregoing equation. Therefore, it is conceivable to increase the 
angle .theta. to a value close to 90.degree. to minimize the value of 
Ci/C.sub.1 of the equation given above. However, if it should entail 
minimization of the value S, minimization of the ratio Ci/C.sub.1 becomes 
impossible. The condition of Cm/C.sub.M .gtoreq.0.77 can be attained 
without varying the value of S.sub.1, by increasing the angle .theta. 
toward the inlet of the crushing chamber. Namely, a crushing chamber which 
can comply with these conditions should have be shaped such that its side 
wall surface is inclined away from a vertical line in the inlet portion 
and gradually inclined toward the vertical line in the outlet portion. A 
crushing chamber with such a shape is ideal for the improvement of the 
reduction ratio since it can meet all of the conditions which are required 
in this regard, including a broad inlet, a narrow outlet, the condition of 
C.sub.M /Cm.gtoreq.0.77 which has to be complied with to permit choke 
feed, and application of sufficient crushing force on the feed material. 
FIG. 4 illustrates in section a crushing chamber of a jaw crusher embodying 
the present invention, in which indicated by reference number 11 is a 
movable crusher plate or jaw which is rockable about a fulcrum point 10, a 
stationary crusher plate or jaw 14, and a crushing chamber in the form of 
a gap space 15 defined between the movable and stationary crusher plates 
11 and 14. The side surfaces of the crushing chamber 15, more 
specifically, the side surface 16 on the part of the movable crushing 
chamber 11 and the side surface 17 on the part of the stationary crusher 
plate 14 are shaped such that they are inclined in the inlet region away 
from a vertical line extending through the fulcrum point 10 and gradually 
come closer to each other in the outlet region of the crushing chamber 15. 
In this instance, however, the angle of inclination of the side surface 16 
at the inlet 18 of the crushing chamber should not be too small since 
otherwise the value of CM will become smaller than Cm (Cm&gt;CM), lowering 
the capacity of the crusher itself. Therefore, the angle of inclination 
should be determined in a range which will hold the ratio of Cm/CM at a 
value not smaller than 0.77. To this end, the angle of inclination 
.theta..sub.1 in the inlet region 18 is preferably in the range of 
45.degree. to 55.degree., while the angle of inclination .theta..sub.2 in 
the outlet region 20 is preferred to be in the range of 0.degree. to 
10.degree.. The angle .psi. which is formed between the side surfaces 16 
and 17 on the movable and stationary crusher plates is desired to be 
smaller than 27.degree. from the standpoint of preventing slips of the 
feed material on the side surfaces. 
FIG. 5 shows the relationship between the displacement and speed of the 
oscillatory motion obtained from the results of actual operations of a 
double-toggle type jaw crusher with a crushing chamber of the 
above-defined shape and a mantle diameter of 1200 mm, crushing raw 
material with a size of d.sub.1 =250 mm into a size of d.sub.2 =20 mm, 
thus at the reduction ratio of d.sub.2 /d.sub.1 =12.5. As clear from FIG. 
5, the crusher capacity reaches its peak when the speed of the oscillatory 
motion is in the range of 228-279 rpm, and overcompression occurs at 
higher speeds. The safety device is disrupted due to overcompression if 
the quantity of the oscillatory motion exceeds 30 mm. The optimum value of 
the oscillatory motion is in the range of 12 to 24 mm. In the case of a 
crushing chamber of the conventional shape, the safety device was actuated 
under all of the conditions shown in FIG. 5 to stop the crushing 
operation. Upon studying the appropriate range of the oscillatory 
displacement or the speed of the oscillatory rotation in relation to the 
dimension D corresponding to the mantle diameter, it is understood that 
the oscillatory displacement is in the range of (0.01.times.0.03).times.D 
mm and the speed of the oscillatory rotation is in the range of 
(9650-7600)/.sqroot.D rpm. Although not shown in the drawing, these facts 
were confirmed in other experiments. The above-described shape of the 
crushing chamber according to the invention is applicable to other 
rotational crushers such as the single toggle jaw crusher or the like in 
addition to the double toggle jaw crusher exemplified in the foregoing 
embodiment. The term "dimension corresponding to the mantle diameter" as 
used in this specification means the diameter of the mantle itself in the 
case of a cone crusher, and double the dimension D.sub.0 of FIG. 4 in the 
case of a jaw crusher. 
In addition to the crushing chamber of the above-defined shape, it is 
preferred to provide a toggle seat block fixing construction as shown in 
FIGS. 6 and 7 in the case of a toggle jaw crusher. More specifically, as 
shown in those figures, a toggle seat 109 of a swing jaw 103 and a toggle 
seat 108 of a toggle seat block 106a is linked by a toggle plate 107 the 
rear side of which is abutted against a front vertical surface 112 of a 
back frame 105 or against a spacer 115 provided along the front vertical 
surface 112. Fixedly mounted on the inner surfaces of side plates 110 
which cover the opposite lateral sides of the swing jaw 103 are block-like 
support members 117 which are in abutting engagement with the bottom 
surface 116 of the toggle seat block 106a to support the latter from 
beneath. The upper surfaces of the support members 117 also serve as guide 
surfaces for the back-and-forth movements of the toggle seat block 106a. 
Further, a guide member 118 is fixedly mounted on the inner surface of 
each side frame 110 in a position which is located at a predetermined 
distance L from the upper end of the toggle seat block 106a. The upper 
surface of the toggle seat block 106a which opposes the lower surface of 
the guide member 118 are provided with tapered surfaces 120a at the left 
and right end portions, the tapered surfaces 120a being inclined in the 
leftward and rightward directions, respectively. Fitted between each guide 
member 118 and the tapered surface 120a is a rectangular plate-like wedge 
member 122a which is provided with a tapered surface 121a on its lower 
side, with the same taper angle as that of the opposing tapered surface 
120a of the toggle seat block 106a. Threaded laterally into each wedge 
member 122a are screws 123 which constitute a sort of shifting screw 
mechanism, increasing the distance between the side frame 110 and the 
wedge member 122a upon tightening the screws 123, pushing down the toggle 
seat block 106a against the lower support member 117 by the wedge action 
of the tapered surfaces 120a and 121a. The distance Lo between the upper 
end of the back frame 105 and the lower side of the support member 118 is 
set at a length smaller than the height L.sub.1 of the toggle seat block 
106a. 
Therefore, as the right-hand shift screws 123 are tightened by turning same 
clockwise as indicated by arrows in FIG. 7, the wedge member 122a is 
pressed inward of the machine frame as indicated by arrow 124, bringing 
the tapered surfaces 120a and 121a into sliding contact, and shifted 
toward a position between the tapered surface 121a and the lower surface 
of the guide member 118a, grippingly fixing the toggle seat block 106a 
between the guide member 118a and support member 117 through the wedge 
member 122a. On the other hand, in order to remove the toggle seat block 
106a, the wedge member 122a is pushed in a direction opposite to the arrow 
124 after loosening the shift screws 123a, and removed from the position 
between the toggle seat block 106a and the guide member 118a (the same 
applied to the wedge member 122a which is mounted on the right side of the 
machine). Then, the toggle seat block 106a is lifted up by a crane or 
other suitable means, using the free space of the width lo, to dismantle 
the toggle seat block 106a from the machine. The position of the toggle 
seat block 106a can be adjusted in the forward or rearward direction by 
changing the thickness of the spacer 115. 
In a crushing operation by a jaw crusher, there sometimes occurrs 
difficulty in removing hard rocks which are stuck between the crusher 
plates due to the hardness of rocks far exceeding the crushability of the 
machine, requiring a worker to get into the crushing chamber to remove the 
rocks manually from upper ones. This is very dangerous and uneconomical in 
view of the large time losses which are incurred before restoration of a 
normal operation. In order to facilitate such rock-removing jobs on such 
occasions, a first toggle plate which is connected to a drive rod to 
impart rocking motions to a swing jaw is preferred to be constituted by a 
plurality of separable blocks. More particularly, in an example shown in 
FIGS. 8 and 9 the first toggle plate 214 is constituted by three blocks 
214a to 214c which are connected in series by means of a number of bolts 
220 passing through connecting plates 219a and 219b which are disposed on 
opposite sides of the blocks 214a to 214c. The end faces 221 and 222 of 
the leftmost and rightmost blocks 214a and 214c are provided with a 
concave surface of an arcute shape in section. As is clear from FIG. 9, 
abutted against the curved concave end faces 221 and 222 are projections 
223 and 224 which are provided at the lower fulcrum point 215 of the swing 
jaw 201 and at the lower end 213 of a drive rod 212, respectively. The 
first toggle plate 214 is rockably retained between the projections 223 
and 224 by means of a compression spring 207. Mounted at opposite sides of 
the first toggle plate 214 are a pair of hydraulic piston-cylinders 225 
which are disposed parallel with the axis J of the first toggle plate 214 
and each have one end thereof connected to the swing jaw 201 on the side 
of the lower fulcrum point 215 and the other end to the lower end of the 
drive rod 212. In a case where a pair of hydraulic cylinders are provided 
at opposite sides of the first toggle plate 214 in this manner, the 
pressures of the hydraulic cylinders are applied uniformly when separating 
the blocks by the cylinder operation as will be described hereinlater, 
facilitating the removal of the blocks 214a to 214c. If desired, a single 
piston-cylinder may be provided in alignment with the axis of the first 
toggle plate 214. Although not shown in the drawings, there is no 
necessity for using separable blocks for the second toggle plate. Since 
the blocks 214a to 214c are directly subjected to the compressive force to 
be applied to the feed material, they should have a sufficient thickness t 
from the standpoint of strength, and their joint faces 226 and 227 should 
be disposed at right angles with the top surface 228 to let the 
compressive force act peripendicularly on the joint faces 226 and 227. 
If rocks with a hardness beyond the compressive crushing ability of the 
crusher are fed into the crushing chamber when the swing jaw 201 is driven 
by the eccentric rotation of the drive shaft 210, the prime mover as well 
as the swing jaw 201 is stopped in the middle of the compressing cycle due 
to the inability of breaking the hard rocks. On such an occasion, the 
drive wheel is slightly rotated in a reverse direction by manual operation 
to retract the swing jaw 201 a little to thereby loosen the compressive 
force of the swing jaw relative to the feed material in the crushing 
chamber. Nextly, the bolts 220 which connect the first toggle plate 214 
are loosened in preparation for the disassembling of the toggle plate. In 
this state, the toggle plate 214 is not disassembled due to the 
compressive force of the compression spring 207 acting in the axial 
direction of the toggle plate. Upon actuating the cylinders 225, the swing 
jaw 201 is rocked to a slight degree in the compressing direction since 
the compressive force on the feed material has been slightly loosened, 
releasing the toggle plate 214 from the compressive force to permit the 
operator to lift up and remove the middle block 214b of the toggle plate 
214. At this time, from the standpoint of safety and smooth operation in 
the subsequent stage, it is desirable to suspend the end blocks 214a and 
214c by the use of a pully and a wire or other suitable means to prevent 
them from falling under the force of gravity. After removing the middle 
block 214b in this manner, the swing jaw 201 is fixed in position solely 
by the pressure of the hydraulic cylinders 225, so that it is swung 
backward (in the releasing direction) as the fluid pressure of the 
hydraulic cylinders 225 is gradually lowered, broadening the outlet gap 
width of the crushing chamber to drop off the stuck material. Thus, the 
blocking rocks can be easily removed in an extremely short time period. In 
order to restore the operating condition, the hydraulic cylinders 225 are 
actuated to rock the swing jaw 201 forward in the compressing direction, 
and the middle block 214b is inserted between the end blocks 214a and 214c 
and fixed to the latter by the bolts. The crushing operation may be 
recommenced as soon as the blocks are assembled into a unitary toggle 
plate. 
FIG. 10 illustrates a modified construction of a separable toggle plate 
which can be divided into a couple of blocks. In this case, a projection 
232b is provided on the joining end face of one block 231b while a concave 
surface 232a provided on the opposing joint end face of the other block 
231a for rolling engagement with the projection 232b. By joining the two 
blocks 231a and 231b in this manner, the toggle plate can be folded in the 
middle portion and separated if necessary without changing the positions 
of the rear ends 233 and 234 of the respective blocks. 
Further, in the case of a jaw crusher, it is preferred to provide a tension 
rod spring adjusting mechanism as shown in FIGS. 11 and 12 in order to 
facilitate the adjustment of the tension rod spring. As shown particularly 
in FIG. 11, a tension bolt 316 is loosely fitted in an open hole formed 
horizontally through a fixed plate 319 secured to a machine frame, and a 
tension rod spring 320 is retained in a compressed state between the fixed 
plate 319 and an adjusting plate 318 the position of which is adjustable 
by means of an adjusting nut 317 threaded on a screw portion 322 in the 
rear end portion of the tension bolt 316. 
On the other hand, a cylinder mounting plate 324 which supports vertically 
thereon a pair of hydraulic cylinders 323a and 323b is centrally provided 
with a female screw portion 325 for threaded engagement with the screw 
portion 322 of the tension bolt 316. The cylinders 323a and 323b are 
mounted on the cylinder mounting plate 324 in such positions that, when 
the cylinder mounting plate 324 is threaded on the screw portion 322, the 
piston rods 326a and 326b of the cylinders 323a and 323b are abutted 
against the surface of the adjusting plate 318 according to the extent of 
extension of the respective cylinders. 
The above-described adjusting mechanism is operated in the following manner 
to adjust the biasing force of the tension rod spring 320. In the first 
place, the cylinder mounting plate 324 with the cylinders 323a and 323b is 
threaded into a suitable position on the tension rod 316 as shown in FIGS. 
11 and 12, and then the hydraulic cylinders 323a and 323b are actuated to 
extend the respective piston rods 326a and 326b in the compressing 
direction as indicated by arrow 327, thereby pushing the pressure 
adjusting plate 318 forward to compress the tension rod spring 320. As a 
result, the adjusting nut 317 is freed from the pressure of the tension 
rod spring 320, so that it can be easily turned by application of a small 
force to tighten or loosen the same into an arbitrary position. After 
shifting the adjusting nut to an appropriate position, the fluid pressure 
of the hydraulic cylinders 323a and 323b are lowered, so that the pressure 
adjusting plate 318 is pushed into abutting engagement with the adjusting 
nut 317 by the action of the tension rod spring 320 to set the tension rod 
spring in an appropriate compression length. Where there should arise a 
necessity for removing the tension rod spring 320, the nut 317 is shifted 
rearward in the same manner to weaken the compressive force of the tension 
rod spring, and then the adjusting nut 317 is removed from the screw 
portion 322 to free the tension rod spring 320. 
Although a couple of hydraulic cylinders are employed in the example shown 
in FIGS. 11 and 12, three or more similar hydraulic cylinders may be used 
to ensure that the pressure adjusting plate is supported in a more 
stabilized state by the piston rods. 
As clear from the foregoing description, the crusher according to the 
present invention can attain a high reduction ratio, for example, a 
reduction ratio of 12 by one-stage operation, in contrast to the 
conventional crushers which require two or more crushing stages in order 
to accomplish the corresponding reduction ratio, thus permitting 
simplication of the crushing process and enhancement of the operational 
efficiency. Further, the present invention rationalizes the crusher 
construction by employing, in combination with the crushing chamber of the 
improved shape, the above-described toggle seat block fixing mechanism, 
the swing jaw opening mechanism and/or the tension rod spring adjusting 
mechanism. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.