Electronically controlled electric motor with variable power output

Electric motors which utilize a combination of electromagnets and permanent magnets to effect relative rotation of motor components and have the following characteristics: (1) all of the magnets incorporated in one of the relatively rotatable motor components are permanent magnets, which are provided with power boost windings and are thus optionally convertible to electromagnets, and all of the magnets incorporated in the other of those components are electromagnets; (2) all of the convertible permanent magnets are oriented so that the same pole of each magnet (north or south) faces the air gap between that motor component which includes the convertible permanent magnets and the motor component in which the electromagnets of the motor are incorporated, whether functioning as a permanent magnet or as an electromagnet; (3) the relationship between the number of electromagnets (EM) and convertible permanent magnets (PM) is defined by the equation EM=PM+/-1, but where EM > or equal 3 and PM> or equal 3; (4) the electromagnets are wired in such a way that the poles facing the air gap can be either north or south and are varied in accordance with the predetermined sequences in the operator controlled programs; (5) the energization of the wirings in the electromagnets and in the convertible permanent magnets is controlled by switching electronics and an angle of rotation encoder to achieve predetermined rotational movement; and (6) the number of energized convertible permanent magnets and the number (and polarity) of energized electromagnets is varied to increase or decrease the amount of power output.

The present invention relates to electric motors and, more particularly, 
electromagnetic motors of the type which utilize a combination of 
electromagnets and permanent magnets to effect precisely controlled radial 
rotation between the motor components. 
BACKGROUND OF THE INVENTION 
Electric motors employing a combination of electromagnets and permanent 
magnets for the purposes identified in the preceding paragraph are 
disclosed in a number of previously issued U.S. patents. Those of which I 
am aware are Nos.: 
673,980 issued May 14, 1901, to Engelhardt for ELECTROMAGNET MOTOR; 
722,042 issued Mar. 3, 1903, to Poly Aguirre for ELECTROMAGNETIC MOTOR; 
1,907,221 issued May 2, 1933, to Smulski for ELECTRIC MOTOR; 
1,992,137 issued Feb. 19, 1935, to Zeininger for ELECTRIC MOTOR; 
2,281,081 issued Apr. 28, 1942, to Sheldon for ELECTROMAGNET MOTOR; 
2,404,331 issued July 16, 1946, to Werner for ELECTROMAGNETIC MOTOR; 
2,374,998 issued May 1, 1945, to Hitchcock for PERMANENT MAGNET ELECTRIC 
MOTORS; 
2,864,018 issued Dec. 9, 1958, to Aeschmann for IMPULSE MOTOR; 
2,922,943 issued Jan. 26, 1960, to Rupp for ELECTRIC MACHINE; 
2,968,755 issued Jan. 17, 1961, to Baermann for MAGNETIC MOTOR 
3,072,812 issued Jan. 8, 1963, to Gaddes for PERMANENT MAGNET MOTOR; 
3,331,973 issued July 18, 1967, to McClure for MAGNETIC MOTOR; 
3,670,189 issued June 13, 1972, to Monroe for GATED PERMANENT MAGNET MOTOR; 
4,025,807 issued May 24, 1977, to Clover et al. for ELECTROMAGNETIC MOTOR; 
4,305,024 issued Dec. 8, 1981, to Kuroki for MAGNETIC MOTOR; 
4,357,551 issued Nov. 2, 1982, to Dulondel for D.C. IMPULSION MOTOR; 
4,361,790 issued Nov. 30, 1982, to Laesser et al. for ELECTROMAGNETIC MOTOR 
ROTATABLE IN EITHER DIRECTION; 
4,564,778 issued Jan. 14, 1986, to Yoshida for DC BRUSHLESS ELECTROMAGNETIC 
ROTARY MACHINE; 
A major disadvantage of the prior art of permanent magnet motors is that 
they are unable to vary the amount of rotational power required. As a 
result, the size, and therefore power usage, of a motor is determined by 
the amount of energy required to perform the work at the moment of 
heaviest load. Therefore, energy is wasted at all times other than at the 
moment of heaviest load. 
Also, permanent magnet type motors have been plagued by a low starting 
torque. Another common disadvantage of existing permanent magnet motors is 
the difficulty of stopping the rotor of the motor in a precise position 
with respect to the stator. Additionally, existing permanent magnet motors 
have not been designed to enable the rotor to be locked in a fixed 
position relative to the stator, without using a rachet or other 
relatively quick wearing mechanical device (see the discussion in 
Aeschmann U.S. Pat. No. 2,864,018). 
Another important disadvantage of many existing permanent magnet motors is 
the make-and-break type mechanical switching which is employed to energize 
the electromagnets of the motor in the sequence needed to cause the 
armature of the motor to rotate. These switching devices generate sparks, 
and motors employing them consequently cannot be used in flammable or 
explosive environments unless the motor is encased in an expensive 
explosion proof housing, which makes their use impractical in many 
circumstances. See examples of such mechanical switching devices disclosed 
in Sheldon U.S. Pat. No. 2,281,081; Hitchcock U.S. Pat. No. 2,374,998; 
Rupp U.S. Pat. No. 2,922,943; Baermann U.S. Pat. No. 2,968,755; and 
McClure U.S. Pat. No. 3,331,973. 
SUMMARY OF THE INVENTION 
I have discovered that the above mentioned disadvantages of previously 
proposed motors using a combination of permanent magnets and 
electromagnets can be overcome by a unique motor construction which has a 
relatively rotatable armature (or rotor) and stator and the following 
characteristics: (1) all of the magnets incorporated in one of the 
previously mentioned components are permanent magnets which are 
preferrably augmented with windings so that at the operator's discretion 
these permanent magnets can be converted to electromagnets to provide 
additional power to the motor, and all of the magnets incorporated in the 
other of the components are electromagnets; (2) all of the convertible 
permanent magnets are oriented so that the same pole of each magnet (north 
or south) faces the air gap between that motor components; (3) the 
relationship between the number of electromagnets (EM) and convertible 
permanent magnets (PM) is defined by the equation EM=PM+/-1, where EM is &gt; 
or equal 3 and PM is &gt; or equal 3; (4) the core of each of the 
electromagnets is constructed from permeable material so that when the 
electromagnet is not energized its core will be attracted to the 
convertible permanent magnet on the other motor component; and (5) the 
poles of the electromagnets (as opposed to the convertible permanent 
magnets) are reversible, which allows the poles of all energized magnets 
facing the air gap to be selected as either north or south and therefore 
create either an attraction or a repulsion force relative to the nearest 
convertible permanent magnet located on the other motor component. 
One significant advantage of using this novel arrangement of electromagnets 
and convertible permanent magnets is that the windings can be energized in 
selected numbers and in different sequences, through use of commercially 
available position encoders and controllers, to vary the number and 
direction of interacting magnetic poles and therefore the power of the 
motor. This process results in multiple controllable levels of power 
output at the same speed of rotation (up to six in the motor demonstrated 
in the drawings which are part of this application). 
Another advantage of using this novel arrangement of electromagnets and 
convertible permanent magnets is that a smooth running motor can be 
obtained. When the rotor of a motor employing this principle is rotating, 
power is constantly being applied to multiple electromagnets, creating a 
smooth source of constant power rather than a source which is being 
interrupted by the change in polarity of the electromagnets at least once 
during each rotation, as is done in many motors currently available. 
Another advantage is that motors employing this novel arrangement have an 
extremely high start-up torque and accordingly can be started up under 
heavier loads than motors using conventional methods. 
Another advantage of these novel motors is that they can be made to operate 
over a wide range of speeds simply by varying the elapsed time over which 
the electromagnets are energized and deenergized. Still another advantage 
of this new arrangement is that the direction of rotation of the motor can 
be reversed and it will still operate with the same ease, power, control, 
and functionality. 
Still another advantage of the novel motors I have invented and disclosed 
herein is that the rotating component of the motor may be stopped in any 
one of a large number of precise relationships relative to the stationary 
component of the motor. This makes my novel motor particularly useful as 
stepping and oscillating motors and in robotic and other applications 
where precise manipulation of a robotic arm or other mechanism is 
required. 
Related advantages of these motors are that the capabilities which allow 
them to start under high torque also allow them to stop quickly and to 
brake or hold a load in a slow moving or stopped position. They can 
accordingly be used to advantage in applications requiring braking by the 
motor. 
Versatility is another significant advantage of the novel electric motors 
disclosed herein. They may be manufactured in a variety of diameters with 
different power outputs, and/or multiple segments, each including two 
relatively rotatable magnet bearing components, axially aligned and 
drive-connected together to provide a motor with a higher power output. 
These new motors may be operated from either a.c. or d.c. power sources. 
The motors I have invented are also efficient and are comparable to a 
synchronous motor in this respect. However, at the same time these motors 
are comparable in performance to, and have all the advantages of, a 
brushless d.c. motor. But, unlike the latter, they can be used in an 
explosive or flammable environment without use of an explosion proof 
casing. This is a significant economic advantage because of the high cost 
of explosion proof motors. 
OBJECTS OF THE INVENTION 
From the foregoing it will be apparent to the reader that one important and 
primary object of this invention resides in the provision of novel, 
improved, electric motors. 
Other important, yet related, objects of my invention are the provision of 
electric motors which: 
contain multiple levels of power output at the same speed of rotation; 
are smooth running; 
have a high start-up torque and can be started under full load; 
are reversible and have a wide range of operating speeds; are particularly 
suited for use as stepping motors and in robotic and other applications 
requiring that the mechanism operated by the motor be manipulated with a 
high degree of precision; 
are particularly suited for use in applications in which a braking function 
is required; 
are efficient and economical to operate; 
are versatile in that they can be produced in a wide range of sizes and 
power outputs; 
are flexible in that they can be operated from either an a.c. or d.c. 
electrical current; 
employ convertible permanent magnets in one of two relatively rotating 
motor components and electromagnets in the other of those components with 
the number of electromagnets being either one less or one more than the 
number of convertible permanent magnets (but greater than three) and all 
the convertible permanent magnets being oriented with the same pole facing 
the air gap between the two components of the motor and with the core of 
the electromagnets constructed of a permeable material which, when the 
electromagnet is deenergized, will be magnetically attracted to the 
convertible permanent magnet nearest it; 
are simple and economical to produce. 
Other important objects and features and additional advantages of my 
invention may become apparent to the reader as he studies the above list, 
the detailed description, the related drawings, and the accompanying 
claims.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings, FIG. 1 depicts a permanent magnet motor 
constructed in accord with, and embodying, the principles of the present 
invention. 
One major component of motor 10 is a casing 12. Housed within that casing 
are a stationary component or stator 14 and a relatively rotatable 
component 16, which also may be referred to as a rotor or armature. The 
rotor is mounted on a shaft 18 which is rotatably supported in appropriate 
bearings (not shown) at opposite ends of motor casing 12. 
Seated in blind recesses 20 spaced equiangularly and circumferentially 
symetric around the periphery 22 of rotor 16 are a series of eight 
flush-mounted, permanent magnets 24. These magnets are oriented with their 
major axes lying along radii of rotor 16, and they are oriented so that 
the same pole of each magnet (north in the illustrated motor) faces the 
air gap 26 between the rotor 16 and the stator 14 of the motor. They are 
wrapped with windings 27 through which electric current can pass thereby 
converting the permanent magnets to electromagnets to boost the power 
output. As electromagnets they are more powerful and generate more torque 
than when operating as permanent magnets. The ability to convert these 
magnets from permanent to electromagnets and back produces part of 
variable power output feature, which greatly increases the flexibility and 
usefulness of the motor. 
Samarium-cobalt magnets or other highly effective magnetic material may be 
employed to maximize the power output-to-size ratio of motor 10. However, 
these magnets are relatively expensive. Consequently, when size and weight 
are not controlling criteria, magnets fabricated from a less expensive 
material such as an Alnico (aluminum-nickel-cobalt) alloy can be employed 
instead at a considerable savings in cost. 
Cooperating with convertible permanent magnets 24 to effect rotation of 
armature 16 is a series of nine electromagnets 28, each consisting of a 
winding 30 on a core 32. Like convertible permanent magnets 24, 
electromagnets 28 are spaced equiangularly and circumferentially symetric 
around the stator 14 and are each oriented with their major axes lying 
along radii originating on the axis of rotation 34 of motor 10. The core 
32 of each electromagnet 28 extends to the air gap 26 between the rotor 16 
and stator 14 of motor 10, and the cores are fabricated from a permeable 
material such as soft iron, which will become demagnetized when the 
electromagnet is deenergized. 
Electromagnets 28 are mounted on the stator 14 of motor 10. 
It will be noted from the foregoing that the number of electromagnets 28 in 
motor exceeds the number of convertible permanent magnets 24 by one. Thus 
motor 10 fulfills the requirement expressed above that the relationship 
between the number of electromagnets and convertible permanent magnets 
satisfy the equation 
EQU EM=PM+/-1, in which EM &gt; or equal 3 and PM is &gt; or equal 3 
where EM is the number of electromagnets in the motor, and PM is the number 
of convertible permanent magnets. 
The operation of motor 10 at power output level number 6 will now be 
described. Associated with the mechanical or structural components of 
motor 10 discussed above is a system for so energizing the windings 30 of 
electromagnets 28 that those magnets will cooperate with the rotor mounted 
convertible permanent magnets 24 to bring about the rotation of rotor 16 
in the manner and modes described and illustrated in FIGS. 8 through 12. 
To this end, the windings 30 of the electromagnets 28 are so energized 
that any energized electromagnet will have a pole of the same polarity as 
convertible permanent magnets 24 (north in the illustrated exemplary 
motor) facing the air gap 26 between the rotor 16 and stator 14 of motor 
10. 
One exemplary system for controlling the operation of motor 10 in the 
manner just described in illustrated in FIG. 6 and identified by reference 
character 37. The major components of control system 37 include a position 
encoder 38 for continuously detecting the position of rotor 16 to stator 
14, an electronic switching circuit 40 for energizing the windings 30 of 
electromagnets 28 in a predetermined sequence which will further the 
purposes discussed above, and a microprocessor-based or other solid state, 
sequencing controller 42. Sequencing controller 42 transmits triggering 
signals to the various switches in curcuit 40 to effect the closing and 
opening of those switches in a sequence and pattern dictated by 
information regarding the position of rotor 16 relative to stator 14 
supplied to controller 42 by position encoder 38. 
Optical encoders may be employed to advantage in control system 37 to 
detect the position of rotor 16. Suitable optical encoders are available 
from Litton Industries, Honeywell, Inc., and other sources. Appropriate 
controllers which can be employed to operate the switches in switching 
system 40 in the appropriate sequence and as rotor 16 reaches specific 
angular positions relative to stator 14 as reported by position encoder 38 
are also commercially available. 
For the exemplary motor 10 with its nine electromagnets 28, a switching 
circuit 40 with nine pairs of transistorized or other solid state power 
switches S1 and S2, S3 and S4 . . . S17 and S18 is employed. The switch 
pairs are connected in parallel across an a.c. power source 43 by main 
leads L44 and L46 and branch leads L48 . . . L64 as shown in FIG. 2. The 
two switches in each pair are located on each side of a center tap (a . . 
. i in FIGS. 2 and 3)--for example, electronic switches S1 and S2 are 
located on opposite sides of the center tap a from branch lead L48. 
It will be apparent from FIGS. 2 and 3 that with either of the two switches 
in a lead L48 . . . L64 closed, the winding 30-1 . . . 30-9 connected to 
that lead by way of the associated center tap a . . . i will be energized. 
For the exemplary motor 10 with nine electromagnets 28 shown in FIG. 1, 
operating in power output level number six, as shown on FIG. 9, four of 
the electromagnet windings 30-1 . . . 30-9 are energized at any one time 
for a continuously running motor. The switches are closed in the sequence 
shown in exemplary part in FIG. 8 and in a time relationship such that the 
current flowing through the windings 30-1 . . . 30-9 will be 40 degrees 
(360/9) out-of-phase. The waveforms (idealized) are shown in FIG. 7 and 
identified by the same number as those appended to the reference 
characters identifying the electromagnet windings as suffixes; i.e., the 
numerals 1 through 9. 
One switch in each pair (e.g., S1) will be closed when the voltage across 
a.c. power source 43 is one polarity, and the other switch in that pair 
(S2 in the example) will be closed when the polarity changes, if it is 
appropriate for the position of rotor 16 detected by encoder 38 that the 
associated winding (here, 30-1) remain energized over a period which 
embraces a change in polarity. This ensures that the polarity of the 
energized electromagnet remains unchanged while it is energized as is 
essential to the intended operation of motor 10. 
To describe the operation of motor 10 in power output level number six as 
described in FIG. 9, it will first be assumed that the motor is stopped. 
This can be done with rotor 16 precisely located relative to stator 14 and 
effectively locked against rotation with respect to stator 14 by 
energizing the windings 30 of an appropriate pair of two adjacent 
electromagnets 28. 
For example, to stop rotor 16 in the position shown in FIG. 1 and/or to 
lock the rotor in that postion, the windings 30-8 and 30-9 of those 
electromagnets 28 identified as Nos. 8 and 9 are energized with 
convertible permanent magnet 6 at, or approaching, the illustrated 
position midway between those electromagnets. This provides strong, 
equally balanced, oppositely directed forces repelling convertible 
permanent magnet 6 away from each of the two electromagnets 28 between 
which it is equidistantly positioned. The forces attracting the remaining 
convertible permanent magnets 24-2 . . . 24-8 toward the cores 32 of the 
remaining eight electromagnets 28-2 . . . 28-9 are balanced. Consequently, 
rotor 16 will tend to remain precisely in this designated position even if 
it is under load. 
Because motor 10 has eight convertible permanent magnets and nine 
electromagnets, there are 72 (9.times.8) positions 5 degrees (360/72) 
apart in which rotor 16 can be precisely oriented relative to stator 14 by 
virtue of the just-described attraction between convertible permanent 
magnets 24 and electromagnets 28. This makes motor 10 eminently suitable 
for applications requiring a stepping motor and in computer disc drives, 
industrial robot, and other applications where precise advance of the 
electric drive motor is required. 
In applications such as those described in the preceding paragraph, pulsed 
current may be employed to step the rotor 16 of motor 10. In that case, a 
controller 42 capable of triggering switching circuit 40 in a manner that 
will supply pulses of current of an appropriate duration and in an 
appropriate sequence to the windings 30 of electromagnets 28 can be 
employed. Or, if more versatility in the operation of motor 10 can be 
utilized advantageously, one may employ a sequencing controller that can 
be programmed to cause switching system 40 to supply either pulsed current 
to the electromagnet windings 30 to provide a stepping motor type of 
operation or continuous current to provide a type of operation emulating 
that of a synchronous motor and a brushless d.c. motor. 
With the rotor 16 or motor 10 so halted that convertible permanent magnet 
24-1 is opposite electromagnet 28-1 and the current to the motor then 
turned on, the sequencing controller 42 will cause the apropriate switches 
S1 . . . S18 to be closed in the manner required to energize the windings 
30-1, 30-7, 30-8, and 30-9 of electromagnets 28-1, 28-7, 28-8, and 28-9 
with north poles of those electromagnets facing the air gap 26 between 
rotor 16 and stator 14 (in the illustrated, exemplary motor 10 with its 
nine electromagnets, four of those electromagnets are energized at any 
given time during the continuous rotation mode of operation, and the other 
five windings are deenergized). 
As is apparent from FIGS. 1 and 8, this will create strong, though 
progressively smaller, forces of repulsion between: (a) convertible 
permanent magnet 24-1 and electromagnet 28-1, (b) convertible permanent 
magnet 24-8 and electromagnet 28-9, (c) covertible permanent magnet 24-7 
and electromagnet 28-8, and (d) convertible permanent magnet 24-6 and 
electromagnet 28-7. These several forces of repulsion all tend to drive 
the rotor 16 of motor 10 in the counterclockwise direction identified by 
arrows 66 and 68 in FIG. 1. 
Also, because the remaining four convertible permanent magnets 24-2 . . . 
24-5 .are nearer the four unenergized electromagnets 28-5, 28-4, 28-3 and 
28-2, the forces of attraction between those four convertible permanent 
magnets and the soft iron cores 32 of the just-identified electromagnets 
will be greater than the forces of attraction between the same convertible 
permanent magnets and the unenergized electromagnets on the opposite side 
of those convertible permanent magnets (28-3, 28-4, 28-5, and 28-6). 
Consequently, the net forces of attraction available when motor 10 is 
started from the rotor position under discussion also act to displace 
rotor 16 in the direction identified by arrow 66 and 68. 
This same combination of forces of repulsion and forces which will turn 
rotor 16 in the direction indicated by arrows 66 and 68 is also available 
as rotor 16 continues in that direction, and the electromagnets of the 
rotor are energized in an appropriate pattern for each subsequent 5 degree 
apart position of the rotor. The sequence of patterns in which the 
electromagnets is energized is shown for the first nine of those positions 
in FIG. 8. 
It will be apparent from the drawing and the foregoing that the speed of 
motor 10 can be varied over a wide range by varying the frequency with 
which the windings 30 of electromagnets 28-1 . . . 28-9 are energized. 
When this frequency reaches the switching time (pulse width modulation or 
similar methods) of the current on which motor 10 in operated, the 
operation of the motor will essentially duplicate that of a synchronous 
motor, providing the efficiency and other advantages which that type of 
motor has. At the same time and as it does over its entire speed range, 
motor 10 will continue to operate as a brushless d.c. motor; and it will, 
therefore, also have the advantage which that type of motor provides 
including large starting torque, ruggedness, high efficiency, and ease 
with which the speed of the motor can be controlled. 
It was also mentioned above that a motor as shown in the drawing is capable 
of being run in reverse. The foregoing discussion of that motor will make 
it apparent to those skilled in the relevant arts that this can be easily 
and readily accomplished merely by changing the sequence in which the sets 
of four electromagnets are energized (and, perhaps, the electromagnets in 
each of those sets). Again, this is a capability which would typically be 
possessed by the conventional microprocessor-based or comparable type of 
solid state controller that is preferably utilized to control electronic 
switching system 40. 
As is referred to above, this new motor 10 includes the novel concept of 
multiple levels of power output from the same motor. As shown in FIG. 9, 
there are two combinations of energization of windings 30, which provides 
two of the levels, and three combinations of energization of windings 27 
around the convertible permanent magnets, which provides the total of six 
combinations. The three combinations for energizing the windings 27 of the 
convertible permanent magnets of the illustrated motor 10 are: (1) no 
windings energized, (2) four windings energized to convert alternate (even 
or odd numbered) magnets into electromagnets having the same magnetic pole 
(north or south but north in the illustrated motor 10) facing the airspace 
26 between the rotor 16 and the stator 14 as the permanent magnet 24, and 
(3) all eight windings energized to convert all permanent magnets to 
electromagnets as described in (2). The wiring of windings 27 are 
illustrated in FIG. 5. There are two separate wiring systems, one for even 
numbered magnets 72 and one for odd numbered magnets 71. These systems may 
be controlled through the same controller system that operates the 
electromagnets 28 on the stator 14 or through a separate but much simpler 
system in which the changing of power output levels is accomplished 
through a dual toggle switching system (not illustrated) wherein a switch 
for each system is either in an "on" or and "off" position, thereby 
determining whether the wirings of the convertible permanent magnets are 
energized. 
Many physical variations of the illustrated motor are of course within the 
scope of my invention. For example, the inner rotor 16 may be designed as 
the stationary component and the outer component 14 allowed to rotate 
about that now stationary component. Or, at the expense of its "brushless" 
characteristics, the illustrated motor may be redesigned with 
electromagnets carried by its moving rotor and convertible permanent or 
permanent magnets carried by its stationary stator, and, as long as the 
relationship EM=PM+/-1, but &gt;3 is maintained, the number of convertible 
permanent magnets and electromagnets can be increased or decreased to the 
optimum number for a particular application of the invention. 
Also, variations may be made in the system by which a motor embodying the 
principles of my invention is controlled without exceeding the scope of 
that invention. FIG. 4, for example, depicts a switching system 70 which 
can be utilized to operate a motor as disclosed herein on d.c. power. 
Switching circuit 70 resembles the circuit 40 of that character described 
above except that the number of switches (identified as S-19 . . . S-27) 
is halved, a simplification made possible because there is no need to 
accommodate the reversal in the direction of current flow appurtenant to 
the operation of the motor on a.c. power. 
Switching curcuit 70 can be operated by the same type of controller as 
switching circuit 40; and, like the latter, it functions to control the 
flow of current to the windings 30-1 . . . 30-9 of electromagnets 28 at 
the proper time and in the proper sequence. 
It will be apparent from the preceding paragraph that the invention may be 
embodied in other specific forms without departing from the spirit or 
essential characteristics thereof. The present embodiment is therefore to 
be considered in all respects as illustrative and not restrictive, the 
scope of the invention being indicated by the appended, claims rather than 
by the foregoing description; and all changes which come within the 
meaning and range of equivalency of the claims are therefore intended to 
be embraced therein.