U.S. patent number RE29,090 [Application Number 05/583,192] was granted by the patent office on 1976-12-28 for coin selector utilizing a coin impeller.
This patent grant is currently assigned to Mars, Inc.. Invention is credited to Guy L. Fougere.
United States Patent |
RE29,090 |
Fougere |
December 28, 1976 |
**Please see images for:
( Certificate of Correction ) ** |
Coin selector utilizing a coin impeller
Abstract
A coin selector which utilizes a coin impeller is disclosed, the
impeller comprising .[.magnetic field means.]. .Iadd.a magnetic
field generator .Iaddend.for accelerating the coin. Coin velocity
sensing .[.means .]. .Iadd.photodetectors .Iaddend. located
downstream from the coin impeller and associated circuitry serve to
compare the coin's acceptance ratio with predetermined values for
acceptable coins. .Iadd.
Inventors: |
Fougere; Guy L. (Lincoln,
MA) |
Assignee: |
Mars, Inc. (McLean,
VA)
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Family
ID: |
40456463 |
Appl.
No.: |
05/583,192 |
Filed: |
June 2, 1975 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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423220 |
Dec 10, 1973 |
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858351 |
Sep 16, 1969 |
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Reissue of: |
120652 |
Mar 3, 1971 |
03701405 |
Oct 31, 1972 |
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Current U.S.
Class: |
194/324;
453/32 |
Current CPC
Class: |
G07D
3/14 (20130101); G07D 5/08 (20130101) |
Current International
Class: |
C08K
7/00 (20060101); C08K 7/12 (20060101); G07D
3/00 (20060101); G07D 9/00 (20060101); G07F
003/02 () |
Field of
Search: |
;194/1E,1K,99,1R,1A,101,41 ;133/1 ;209/111.8 ;294/65.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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139,554 |
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Jun 1934 |
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DT |
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22,891 |
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Dec 1967 |
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JA |
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151,897 |
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Feb 1961 |
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SU |
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Primary Examiner: Reeves; Robert B.
Assistant Examiner: Rolla; Joseph J.
Attorney, Agent or Firm: Davis, Hoxie, Faithfull &
Hapgood
Parent Case Text
This application is a continuation of reissue application Ser. No.
423,220, filed Dec. 10, 1973, now abandoned, .Iaddend.and a
continuation-in-part of Patent Application Ser. No. 858,351 filed
Sept. 16, 1969, now abandoned.
Claims
I claim:
1. A device for determining the denomination of a coin comprising a
coin passageway .Iadd.including a track for supporting a coin on
its edge, .Iaddend.means for admitting a coin to the passageway, an
impeller of electrically conductive coins adjacent to the
.[.passageway.]. .Iadd.coin support track, .Iaddend.the impeller
comprising means for generating a magnetic field traveling relative
to a coin .[.in the passageway.]. .Iadd.on the coin support track,
.Iaddend.the generated magnetic field inducing eddy currents in the
coin and interacting with the magnetic fields associated with the
induced eddy currents to impel the coin .Iadd.along the coin
support track .Iaddend.in the direction of the traveling magnetic
field, and means for examining a velocity related property of the
coin .Iadd.while the coin is still supported by the track and
.Iaddend.after the coin has been exposed to at least a portion of
the generated magnetic field.
2. A device for comparing characteristics of a coin with
characteristics of a genuine coin of given denomination comprising
a passageway for conducting the coin along a predetermined path, a
magnetic field generator so positioned in proximity to the
passageway that a coin in the passageway may be brought within its
field, means associated with the generator to apply to a coin in
the field a force having a component aligned with the path by
moving the field relative to the passageway, and means for
comparing .[.a characteristic representative of the velocity of.].
.Iadd.the time for .Iaddend.the coin which has been acted upon by
the field .Iadd.to travel a known distance .Iaddend.with the
corresponding .[.characteristic of.]. .Iadd.time for .Iaddend.a
genuine coin of the given denomination.
3. A method of determining the denomination of a
.Iadd.non-ferromagnetic electrically conductive .Iaddend.coin
comprising the steps of generating a traveling magnetic field,
directing a coin to .Iadd.a coin support track in .Iaddend.the
magnetic field so that the field impels the coin in a desired
direction .Iadd.along the coin support track, .Iaddend.and
examining a velocity related characteristic of the coin when the
coin has been impelled .Iadd.along the coin support track and while
it is still supported by the track.Iaddend. .
4. A method as defined in claim 3 wherein the traveling magnetic
field is generated by moving a plurality of magnets relative to the
coin in the direction in which it is desired to impel the coin.
5. A method as defined in claim 3 including the step of arresting
the movement of the coin .[.as.]. .Iadd.along the coin support
track immediately before .Iaddend.the coin .[.approaches.].
.Iadd.is subjected to .Iaddend.the traveling magnetic field.
6. A method as defined in claim 3 including the steps of arresting
movement of a coin by impelling the coin in a first direction
.Iadd.along the coin support track .Iaddend.causing the coin to
abut a stationary member and then impelling the coin in a second
direction .Iadd.along the coin support track .Iaddend.opposite to
the first direction.
7. A method as defined in claim 3 wherein the .[.impeller.].
.Iadd.traveling magnetic field .Iaddend.is .Iadd.generated by an
.Iaddend.electrically operated .Iadd.impeller .Iaddend.and
including the step of sensing the impeller coil temperature and
regulating the impeller supply voltage as a function of the
impeller coil temperature.
8. A method as defined in claim 3 wherein the velocity related
property is examined while the coin is under the magnetic influence
of the traveling magnetic field and including the step of varying
the magnitude of the magnetic field by an amount based upon a
predetermined .[.program.]. .Iadd.function .Iaddend.related to the
denomination of the coin.
9. A method as defined in claim 3 wherein .Iadd.the coin support
track along which .Iaddend.the coin is impelled .[.along.].
.Iadd.is .Iaddend.an inclined track.
10. A method as defined in claim 3 including the steps of examining
a chordal dimension of the coin, examining the velocity related
characteristic while the coin is under the influence of the
traveling magnetic field and comparing the coin's chordal dimension
and velocity related characteristic with predetermined values to
determine the denomination of the coin.
11. A method as defined in claim 10 including the step of varying
the magnitude of the magnetic field by an amount based upon a
predetermined .[.program.]. .Iadd.function .Iaddend.related to the
denomination of the coin.
12. A method as defined in claim 3 wherein the traveling magnetic
field is generated by supplying a variable current to a plurality
of longitudinally spaced coils such that the current through
adjacent coils has a phase shift relationship.
13. A method as defined in claim 12 wherein the .[.impeller is.].
.Iadd.coils comprise an .Iaddend.electrically operated
.Iadd.impeller .Iaddend.and including the steps of sensing the
current supplied to the impeller, producing a signal dependent upon
a velocity related characteristic of a coin, comparing that signal
with predetermined signals characteristic of acceptable coins, and
accounting for variations in the current from a predetermined
standard during the comparison step.
14. A method as defined in claim 12 including the steps of
arresting the movement of the coin in said direction .Iadd.along
the coin support track, .Iaddend.sensing the arrival of a coin
.Iadd.on the coin support track .Iaddend.and supplying the variable
current to the coils in response to a signal from the coin
sensor.
15. A method as defined in claim 14 including the steps of causing
the coin to move in a first direction .Iadd.along the coin support
track .Iaddend.and abut against a stationary member and then
impelling the coin in a second direction .Iadd.along the coin
support track .Iaddend.opposite to the first direction.
16. A device for determining the authenticity of a
.Iadd.non-ferromagnetic electrically conductive .Iaddend.coin
comprising a coin passageway .[.having.]. .Iadd.including
.Iaddend.an entrance for the reception of a coin .Iadd.and a coin
support track for supporting a coin on its edge, .Iaddend.a coin
accelerating impeller adjacent to the .[.passageway.]. .Iadd.coin
support track, .Iaddend.the impeller comprising means for
generating a magnetic field having a component traveling along a
region of the .[.passageway.]. .Iadd.coin support track,
.Iaddend.the magnetic field component being arranged to impel a
coin along the .[.passageway.]. .Iadd.coin support track,
.Iaddend.and means for examining a function dependent upon the
velocity of the coin .Iadd.while it is still supported by the track
and .Iaddend.after the coin has passed .Iadd.along the coin support
track .Iaddend.through at least a portion of the region.
17. The device of claim 16 wherein the .[.coin passageway includes
a.]. a coin support track .[.having.]. .Iadd.has .Iaddend.a slope
greater than 0.degree. and less than 5.degree. to the
horizontal.
18. The device of claim 16 including coin arrival sensing means for
sensing the arrival of a coin in the device and means actuated by
the arrival sensing means for actuating the impeller.
19. The device of claim 16 including means for reversing the
direction in which the magnetic field travels.
20. The device of claim 16 including .[.a coin support across the
passageway onto which a coin entering the device drops and.]. a
coin stop adjacent to the coin support .Iadd.track, .Iaddend.means
for initially directing .[.the.]. .Iadd.a coin .Iaddend.entering
.[.coin.]. .Iadd.the device .Iaddend.toward the coin stop .[.and
means to impel.]. .Iadd.wherein the impeller impels .Iaddend.the
coin away from a position of rest against the coin stop toward the
velocity dependent function examining means.
21. A device as defined in claim 16 wherein the impeller is
electrically operated and including means for regulating the
impeller supply voltage as a function of the impeller temperature
so that the impeller provides a relatively constant magnetic flux
as the impeller temperature varies.
22. The device of claim 16 wherein the velocity dependent function
examining means provides an output signal related to the velocity
of the coin while the coin is under the magnetic influence of the
impeller, first circuit means for comparing the output signal with
predetermined signals characteristic of acceptable coins and for
providing a resultant signal indicative of the coin's denomination,
means .[.sensitive.]. .Iadd.responsive .Iaddend.to the resultant
signal to modify the traveling magnetic field in order to spacially
separate the coins in accordance with their velocity dependent
function.
23. The device of claim 16 .[.wherein the coin passageway includes
a coin support track adjacent to the impeller and.]. wherein the
impeller provides a magnetic field region across the passageway
which varies in location height above the coin support track along
at least a portion of the length of the coin support track.
24. The device of claim 16 including means providing a first signal
dependent upon the chordal dimension of the coin and wherein the
velocity dependent function examining means provides a second
signal related to the velocity of the coin as the coin passes said
examining means and means for comparing the first and second
signals with predetermined signals characteristic of acceptable
coins.
25. The device of claim 16 wherein the impeller comprises at least
one magnet having a component of motion in the direction in which
it is desired to impel the coin.
26. The device of claim 25 .[.wherein the coin passageway includes
a coin support track and.]. wherein the magnet is arranged for
rotation about an axis positioned with relation to the passageway
as to dispose in proximity to the support track a magnetic field
having a major component in the desired direction of coin travel
along the support track.
27. A device as defined in claim 16 wherein the impeller is
electrically operated and wherein the velocity dependent function
examining means provides an output signal dependent upon the
velocity of the coin as the coin passes the examining means and
including a first circuit means for comparing the output signal
with predetermined signals characteristic of acceptable coins,
means .[.sensitive.]. .Iadd.responsive .Iaddend.to the impeller
current and operatively connected to the first circuit means to
modify the operation of the first circuit means to compensate for
variations in the impeller current.
28. A device as defined in claim 27 wherein the examining means
includes a pair of coin presence sensors and wherein the first
circuit means includes a pulsating signal source, a pulse counter,
and gate means for gating the pulsating signal to the counter in
response to .Iadd.a .Iaddend.signal from the coin presence sensors,
and wherein the pulsating signal source frequency is controlled by
the impeller current sensitive means.
29. The device of claim 16 wherein .[.the coin passageway includes
a first coin support track adjacent to the coin accelerating
impeller, said.]. .Iadd.the coin support .Iaddend.track
.[.sloping.]. .Iadd.slopes .Iaddend.upwardly in the direction in
which the magnetic field travels.
30. The device of claim 29 .[.including.]. .Iadd.wherein the coin
passageway includes .Iaddend.a second coin support track and a
second impeller adjacent to the second coin support track, the
second coin support track and second impeller being located below
one end of the .[.first.]. coin support track whereby coins leaving
said one end of the .[.first.]. coin support track drop onto the
second coin support track adjacent to the second impeller.
31. The device of claim 16 including means for arresting movement
of the coin .Iadd.along the coin support track immediately
.Iaddend.before the impeller impels the coin toward the velocity
dependent function examining means.
32. The device of claim 31 wherein the movement arresting means
includes .[.a coin support across the passageway onto which the
coin is directed, the coin support having.]. an initial section
.Iadd.of the coin support track .Iaddend.inclining from one end
thereof and a second section declining from the other end of the
first section, a coin stop adjacent to said one end and means for
directing a coin entering the device toward the initial section
whereby the coin rests against the coin support .Iadd.track
.Iaddend.and coin stop.
33. The device of claim 32 wherein the inclining and declining
sections are each at an angle of between 0.5.degree. and 5.degree.
from horizontal.
34. The device of claim 16 wherein the velocity dependent function
examining means provides an output signal related to the velocity
of the coin, first circuit means for comparing the output signal
with predetermined signals characteristic of acceptable coins and
for providing a resultant signal indicative of the coin's
denomination, means .[.sensitive.]. .Iadd.responsive .Iaddend.to
the resultant signal to modify the velocity of the coin in order to
spacially separate the coin from other coins examined in accordance
with the differences in their velocity dependent functions.
35. The device of claim 34 wherein the means .[.sensitive.].
.Iadd.responsive .Iaddend.to the resultant signal are arranged to
further impel the coin an amount dependent upon the coin's
denomination.
36. The device of claim 35 wherein the means .[.sensitive.].
.Iadd.responsive .Iaddend.to the resultant signal is arranged to
impel the coin in a direction different from the coin's direction
when the coin is exposed to the velocity dependent function
examining means.
37. The device of claim 16 wherein the impeller comprises a
plurality of coils spaced in the desired direction of coin travel
and an electrical power source for supplying a variable current to
the coils in a manner such that a phase shift relationship exists
between adjacent coils providing a magnetic field traveling in one
direction.
38. The device of claim 37 including means for actuating the
impeller at a predetermined point in the wave form of the variable
current.
39. The device of claim 37 wherein each of the coils are wound
around a pole piece and are located on one side of the coin
passageway and including magnetic shunt means on the side of the
passageway opposite the coils.
40. The device of claim 39 wherein the dimensions between two
adjacent pole pieces is no greater than the diameter of the
smallest coin which the device is designed to accept.
Description
This invention relates to coin selectors which determine the
authenticity and denomination of coins and, more particularly, to
magnetically impelling coins in a coin selector.
Coin operated devices, such as vending machines, coin changers and
toll booths have universal acceptance and are widely used. These
coin operated devices must have the capability of accurately and
rapidly determining the authenticity and denomination of coins
entering the device.
The coin impellers of this invention induce a wide velocity range
between coins of different denominations making it easier to test
and sort coins accurately. By virtue of the fact that the motion
given to the coin through the coin selector system is effected
primarily by the coin impeller rather than by gravity, the velocity
variance for any given coin is extremely small, in the order of
.+-.2 percent. Reliability and effectiveness of the coin selector
of this invention is high because of the minimal variation in coin
velocity.
Accordingly, it is one objective of this invention to provide a
coin selector and method of coin selection utilizing a magnetic
impeller of coins in order to substantially improve the reliability
and effectiveness of a coin selector in sensing the authenticity
and denomination of coins.
Another objective of this invention is to provide a coin selector
which is both unaffected by the velocity imparted to a coin as it
is inserted into the coin selector relatively independent of coin
wear.
In the drawings:
FIG. 1 is a schematic, elevational diagram of a device for
determining the authenticity and denomination of a coin, the device
including a rotary coin impeller formed in accordance with a first
embodiment of this invention which utilizes permanent magnets.
FIG. 2 is a schematic plan view of a coin selector including a
rotary coin impeller formed in accordance with a second embodiment
of this invention which utilizes electromagnets.
FIG. 3 is a schematic illustration of a linear motor coin impeller
formed in accordance with a third embodiment of this invention.
FIG. 4 is a schematic elevational diagram of a coin selector
utilizing the linear motor impeller of FIG. 3.
FIG. 5 is a diagram of a circuit enabling the use of D.C. to
energize a linear motor impeller while FIG. 5A is a table and FIG.
5B is a logic voltage time plot showing the operation of the
circuit of FIG. 5.
FIG. 6 is a schematic elevational diagram of a coin selector formed
in accordance with a fourth embodiment of this invention.
FIG. 7 is a schematic elevational diagram of a coin selector formed
in accordance with a fifth embodiment of this invention utilizing a
pair of linear motor impellers.
FIG. 8 is a schematic elevational diagram of a modification of the
fifth embodiment of FIG. 7.
FIG. 9 is a schematic elevational diagram of a coin selector formed
in accordance with a sixth embodiment of this invention utilizing a
plurality of inclined impellers and coin support tracks.
FIG. 10 is a schematic elevational diagram of a coin impeller
formed in accordance with a seventh embodiment of this invention
utilizing a tapered linear motor impeller.
FIG. 11 is a schematic elevational diagram of a modification of the
seventh embodiment of FIG. 10.
DETAILED DESCRIPTION
Coin Selector
Throughout this specification and in the appended claims, the term
"coin" is intended to mean genuine coins, tokens, counterfeit
coins, slugs, washers, and any other item which may be used by
persons in an attempt to use coin-operated devices. Furthermore,
throughout this specification, for simplicity, coin movement is
described as rotational motion; however, translational motion also
is contemplated.
With reference to FIG. 1, there is illustrated, in schematic form,
a coin selector 10 for electrically conductive coins comprising, in
part, a coin support track 12, coin arrestor means 14, a magnetic
coin scavenger 15, a coin impeller 16, a brake magnet 18 and means
20 for sensing functions dependent upon properties of a coin to
determine the coin's authenticity and denomination.
A coin, after entering the coin selector device 10, passes through
a coin arrestor means 14. In FIG. 1, the arrestor means comprises a
meander path which absorbs most of the coin's kinetic energy and
reduces the coin's velocity in the horizontal direction to an
insignificant value. Any magnetic coin scavenger 15, such as one of
the types illustrated in U.S. Pat. Nos. 1,956,066 and 3,168,180 is
located in the path of coin travel to extract coins made of
ferromagnetic material from the coin selector 10. It is desirable
to remove such coins when permanent magnets are located elsewhere
in the system to avoid having ferromagnetic coins trapped by those
magnets. Alternatively, one or more of the other magnets could
serve as a magnetic coin scavenger if additional means are provided
to clear the magnets of a magnetic coin which is adhered thereto.
As the coin approaches the coin impeller 16, it passes an arrival
sensing device 22 which senses the presence of a coin in the
system. While many sensing devices are suitable, such as
microswitches or inductive switches, a preferred sensor is a
photoelectric device such as a photocell operating in combination
with a light source, and the coin being directed between the light
source and photocell. The signal from the photocell indicating coin
presence, through an amplifier 24, energizes a start control system
26 for purposes to be described below.
The coin, illustrated by the phantom lines 28, reaches the coin
support track 12 where it is brought into proximity with the coin
impeller 16. The track 12 forms the bottom of coin passageway 29
and primarily serves as a support for the coin 28. The track 12 is
not provided with a sufficient slope to cause the coin to roll with
significant velocity. While the track can be horizontal, it is
preferred that the track have a slight slope, in the order of
2.degree. and not greater than 5.degree.. A slight downward slope
toward the property sensing means 20 is preferred; so that in the
event that an electrically non-conductive coin, such as a plastic
disc, is inserted into the coin selector 10 and is unable to be
propelled by the coin impeller 16 the slignt slope of the track 12
will cause the coin to roll through the system at a slow speed.
This will prevent the coin from remaining near the impeller 16 and
eliminate the chance that the coin will accelerate to a velocity
equal to the velocity of an acceptable coin. Alternatively, the
track 12 can be oriented downwardly away from the property sensing
means 20 toward a coin rejection chute (not shown).
Rotary Coin Impeller - (FIG. 1)
The coin impeller 16 is formed in accordance with the first
embodiment of this invention includes a rotor 30 formed of a
non-magnetic material such as plastic which has a plurality of
permanent magnets 32 mounted around the periphery thereof, three
such magnets (six pole faces) being illustrated in FIG. 1. The
magnets are mounted so that the polarity of adjacent magnets
alternate between north and south. The rotor 30 is mounted so that
the coin 28 is located on one side of a diametrical line 33
parallel to the coin support track 12. This is accomplished by
keeping the center of rotation of the rotor 30 below the plane of
the support track 12. The purpose for this is to ensure that the
coin is subjected to a magnetic flux having a horizontal component
only in the direction in which it is desired that the coin travel,
namely, from left to right in FIG. 1 when the rotor rotates
clockwise.
An arriving coin passes through the meander path 14 and occludes
the photocell 22 which, through the signal generated by the
occlusion of the sensor, signals the start control 26. The start
control 26 includes, among other things to be discussed below,
switch control means for energizing the motor to rotate the rotor
30. When the coin arrives at the impeller 16 the rotating magnets
(rotating in the clockwise direction as illustrated in FIG. 1)
produce a rotating magnetic field having a horizontal component
above the coin support track 12 in the direction toward the
property sensing means 20. The rotating magnetic field induces eddy
currents in the coin 28 producing an associated magnetic field
which interacts with the rotating magnetic field to produce a force
on the coin in the direction of movement of the traveling magnetic
field, namely from left to right in FIG. 1. The coin's acceleration
and ultimate velocity are dependent upon the coin's acceptance
ratio, which is its electrical conductivity divided by its
density.
The impeller 16 normally is sufficient to provide enough of a
velocity differential between coins having different coin
acceptance ratios to permit coin discrimination. However, with some
coin sets it may be desirable to supplement the impelled velocity
differential by utilizing an eddy magnetic current brake. A
stationary permanent magnet 18 is located on one side of the coin
support track 12 and a second magnet or plate (not shown) of
ferromagnetic material such as mild steel, is located directly
opposite the magnet 18 in order to provide a constant field across
the coin passageway. As the coin passes through the region of the
stationary magnetic field eddy currents are induced in the coin and
the associated magnetic fields, which oppose the field inducing the
eddy currents, interact with the stationary magnetic field to
create a retarding force. In other words, the resultant force on
the coin is in the direction from right to left in FIG. 1. The
magnitude of the coin's deceleration is dependent upon the coin's
acceptance ratio, as well as the velocity of entry of the coin into
the stationary magnetic field and the area of the coin and the
magnetic field region.
Coin Acceptance Ratio Sensor
The coin leaving the stationary magnetic field supplied by the
permanent magnet 18 enters the region of sensing means 20 which
together with a combinational circuit are provided to examine the
property of the coin related to velocity. A particular apparatus
used is described in detail below with reference to FIG. 4. The
sensing means together with the combinational circuit provide a
signal to a solenoid controlled inclined platform 36 indicative of
the acceptability of the coin. If, the coin is unacceptable it
rolls off the track 12 and is directed into a rejection chute 34 by
the platform 36. If the coin is determined to be acceptable a
solenoid (not shown) is actuated and retracts the platform 36 from
the path of the coin allowing the coin to fall into an acceptance
chute 38.
Electromagnetic System (FIG. 2)
The first embodiment described above employs permanent magnets 32
as part of the impeller 16 and a permanent magnet 18 as the
magnetic brake. Alternatively, electromagnets can be used either
for the impeller or for the magnetic brake or for both.
An electromagnetic coin impeller 50 is illustrated in FIG. 2 and
includes a non-magnetic rotor 52 on which are mounted a plurality
of C-shaped iron cores 54 (only one of which is illustrated). The
cores are mounted on the rotor 52 so that only the pole faces 56,
58 extend through and face the coin support track 12. A wire coil
60 is wound about the central portion of the iron core 54, one end
of the coin being connected to a slip ring 62 mounted on a shaft 64
leading from the rotor 52 to a driving motor 66. The other end of
the coil 60 is electrically connected to a second slip ring.
Electricity from a source 70, shown as alternating current (A.C.)
but which could be direct current (D.C.), is conveyed to the coil
60 through the slip ring 62 and shaft 64 in any conventional
manner, such as by shoes 72, 74. If A.C. is used, the rate of
rotation of the rotor 52 and the frequency of the current should be
chosen to avoid minimum magnetic field strength when the magnet is
above the track 12 such as might be caused if the relationship of
frequency and rotation is such that one or more of the
electromagnet poles is subject to an A.C. zero crossing while the
pole is above the track 12. A low reluctance magnetic shunt such as
a plate 75 of ferromagnetic material is mounted opposite the upper
half of the rotor 52 to affect a constant field across the coin
passageway so that a coin's movement is influenced relatively
uniformly regardless of which side of the track the coin is on.
If a magnetic brake is used, any conventional electromagnet can be
utilized as the brake magnet 76. A D.C. electromagnet is preferred
because the transit time of a coin through the field generated by
the brake magnet 76 is comparable to or less than the frequency
period of conventional current, namely 60 cycles. If A.C. current
is used, the braking experienced by a coin is dependent upon the
timing of its entry into the magnetic field relative to the phase
of the current supply. To avoid this problem and to establish
satisfactorily high levels of braking, a substantial current is
passed through the electromagnet coil resulting in the generation
of, and the need to dissipate a substantial amount of heat. Because
of these problems, a D.C. electromagnet is preferred. A
ferromagnetic plate 77 is mounted opposite to the brake magnet 76
to provide a constant magnetic braking field across the coin
passageway.
It will be recalled that as the coin 28 enters the system and
approaches the coin impeller, it passes an arrival sensor 22 which
senses the presence of the coin and actuates a start control 26.
The start control, through switch means, actuates the coin impeller
50 and the eddy current brake electromagnet 76 for a prescribed
time interval which is long enough to permit the slowest acceptable
coin to pass through the system, after which the switches are
opened inactivating the coin impeller 50 and electromagnet 76.
Since this system utilizes electromagnets which can be rendered
substantially neutral by cutting off the current supply, there is
no need to use a ferromagnetic coin scavenger. If a coin of
ferromagnetic material is inserted into the system, it will be
trapped by one of the electromagnets, probably the impeller magnet.
After the current through the magnets is terminated, the
ferromagnetic coin will roll slowly down the coin support track 12
under the influence of gravity. The ultimate departure velocity of
the ferromagnetic coin will be extremely low due to the slight
slope of the track 12 and due to the residual magnetism of the
electromagnets, thereby permitting distinction between
ferromagnetic coins and other coins which have a low velocity.
Instead of relying merely on the track slope and the residual
magnetic field to ensure a very low velocity for ferromagnetic
coins, a third magnet 78 having a very low flux density can be
utilized downstream from the brake magnet 76.
It is also important, in order to produce consistent and reliable
results, for the magnitude of the current switched into the
electromagnets to be controlled within limits, preferably less than
.+-.1/2 percent. This can be accomplished by conventional
rectifying, filtering and regulating circuitry not illustrated or
described herein but which is well known in the art.
Linear Motor Impeller (FIGS. 3 & 4)
In place of the rotary coin impeller described above in connection
with the first and second embodiments, it is preferred to use
stationary means for producing a traveling magnetic field. Such can
be accomplished by using a linear motor which is similar to a
stator of a conventional cylindrical electric motor which has been
cut along a radial plane and unrolled out flat. As is illustrated
in FIG. 3, such an impeller 80 comprises two series of coils, a
first series including coils 82 and 84 and a second series
including coils 86 and 88. While only two coils per series are
illustrated, a greater number of coils is preferred, for example,
about four per series. The coils are wound around a low carbon
steel impeller core 90 having projecting pole pieces or core
fingers 92-95 spaced longitudinally along the desired direction of
coin travel. A low reluctance magnetic shunt or magnetic return
path 98 is placed at the side of the coin track 99 opposite the
impeller 80 to provide a uniform magnetic field across the coin
passageway. The magnetic shunt may be made of a low carbon steel
plate. It is desirable in the case of high flux densities that the
core 90 be laminated steel.
In order to produce the effect of a traveling magnetic field, it is
necessary for adjacent fields to have a phase shift relationship.
FIG. 3 illustrates a circuit which is suitable for providing
approximately a 90.degree. phase shift between adjacent core
fingers. It can be seen that the first series of coils 82, 84 is
wound in alternating fashion, in other words, coil 82 is wound in a
counterclockwise direction about core finger 92 while coil 84 is
wound clockwise about core finger 94. The second series of coils
86, 88 similarly is wound in alternating fashion, namely coil 86 is
wound counterclockwise about core finger 93 while coil 88 is wound
clockwise about core finger 95.
Either the first series or the second series of coils can be
individually selectively connected directly to a source of
cyclically varying current, for example, chopped D.C. or single
phase sinusoidal A.C. current source 100, such as by AND gate 102
and AND gate 104 respectively, which are controlled by signals from
start control circuit 106. In the case where single phase
sinusoidal AC current is used, the two series are connected in
parallel through a capacitor 108 thus placing the capacitor in
series with the coil series not directly gated on. The capacitor
108 provides a 90.degree. phase shift between the two series of
coils. Because of the reversed direction of windings of adjacent
coils within a series and the phase shift between the coil series
provided by the capacitor 108, the magnetic field is effectively
traveling in one direction. For example, at one instant of time
assuming the polarity of the first coil 82 is north, the polarity
of coil 86 is north plus 90.degree., the polarity of coil 84 is
south and the polarity of coil 88 is south plus 90.degree.. The
thrust direction of impeller 80 is reversed by merely enabling the
presently disabled AND gate and vice versa. This permits selection
of a desired thrust direction for purposes described below.
To provide consistent coin velocities, it is preferable to activate
the impeller 80 each time at the same fixed point in the impeller
current wave form. In this way the resultant coin velocity is not
dependent upon the particular moment of time when the coin is first
exposed to the magnetic field of the impeller. The zero crossing
detector 109 is designed to detect the zero crossing of the
impeller current in the direction providing desired initial
polarity. The zero crossing detector 109 includes a saturation
amplifier, a diode and differentiator to select the desired
direction of transition and a latching relay operated by the output
of the differentiator.
Coin Selector System
Turning now to FIG. 4, a coin selector system 110 for
nonferromagnetic coins, utilizing a linear motor impeller 80, is
schematically illustrated. A coin entering the system through an
entrance slot 112 drops vertically downward through an entrance
meander section 114 which slows the coin and removes most of its
energy. The coin passes an arrival sensor 116 such as a photocell
which senses the presence of the coin in the system and, through an
amplifier 118, energizes a start control system 120 which in turn
energizes the impeller 80 after a slight delay. After passing the
arrival sensor 116 the coin drops onto a coin support track
122.
The support track is designated with an initial short section 124
having an inclined slope of between 0.5.degree. - 5.0.degree.,
preferably approximately 1.5.degree., followed by a declining
longer portion having a declination of approximately the same
slope. The coin drops onto the initial portion 124 and, due to the
inclination, rolls rearwardly (toward the left in FIG. 4) until it
comes to rest against a wall 128. The system is designed with a
delay in energizing the impeller such that the impeller is
energized after sufficient time has elapsed for the coin to come to
rest against the wall 128. The impeller is located with respect to
the track 122 such that portions of at least two pole faces are
adjacent the resting place of the smallest coin desired to be
accepted by the coin selector. Once the impeller is energized, the
coin, if electrically conductive and para or dia-magnetic, will be
caused to move along the track 122 by rolling up the inclining
portion 124 and then down the declining portion 126. The coin
movement is produced by eddy currents induced in the coin which
produces an associated magnetic field. The interaction between the
induced magnetic field in the coin and the field of the forwardly
adjacent coil of the impeller causes the coin to move toward that
coil. The acceleration and velocity of the coin as it leaves the
impeller 80 is determined by the coin's acceptance ratio for the
reasons discussed above. The impeller is turned off by a signal
from the sensors indicating that the coin has left the
impeller.
If a ferromagnetic coin is inserted into this system, it will be
attracted to the impeller and retained in place. After a
predetermined period of time, which is based upon the longest
period of time that would be required for an acceptable coin to
traverse the support track 122, the impeller is turned off and the
ferromagnetic coin remains at the initial section 124 of the track.
By operation of any conventional coin rejection system the
ferromagnetic coin is forced to drop off the track 122, into a coin
rejection receptacle. Similarly, if an electrically nonconductive
coin, such as a plastic slug, is inserted into the system, the coin
will not be impelled by the impeller 80 and will be removed by the
coin rejection system.
In order to insure proper impelling of nonferromagnetic
electrically conductive coins, of the impeller poles are spaced so
that any acceptable coin will be influenced by the fields of two
poles simultaneously, so that the coin feels the effect of the
traveling magnetic field. This may be accomplished by designing the
impeller so that the dimension between corresponding points of
adjacent pole pieces is no greater than the diameter of the
smallest acceptable coin. To avoid a high loss factor and heating,
the spacing between adjacent poles of the impeller should be more
than the effective air gap between the impeller 80 and the magnetic
shunt 98. The effective air gap between the impeller 80 and the
magnetic shunt actually is twice the distance between the impeller
and the shunt because the effective gap is based upon the entire
magnetic path and, therefore, includes the gap twice, once at the
north pole and once at the south pole. It can be seen that in
constructing the impeller, the two design parameters just discussed
define the lower and higher limits for the spacing between adjacent
coils. If a compromise is needed in order to satisfy these design
parameters, the loss factor and heating caused by distance between
the poles being less than the air gap can be tolerated within
limits.
As described above, the coin support track 122 is provided with an
initial inclined portion 124 for the purpose of bringing the
incoming coin to rest at a predetermined position. One alternative
to this design is to utilize a track having a continuous surface
declining from the wall 128 at an angle of approximately
11/2.degree.. When the coin enters the system and passes the
arrival sensor 116, the impeller is initially energized to impel
the coin in a rearward direction or, in other words, toward the
wall 128. After a short period of time with the impelling force
continually being exerted on the coin toward the wall 128 the coin
will be brought to rest against the wall at which time the
direction of the magnetic field is reversed and the coin is
impelled forwardly away from the wall 128. This insures that all
coins start from rest and from a fixed position and provides the
desired consistency of performance.
Electronic Coin Acceptance Ratio Sensing System
The impeller 80 causes the coins to move along the track 122 with a
velocity which is dependent upon the coin's acceptance ratio. It
now is necessary to determine if the coin is acceptable. This is
accomplished by coin presence sensors and associated combinatorial
circuitry described hereinafter or, for example, by those devices
disclosed in copending applications assigned to the assignees of
this application: Ser. No. 91,871, filed Nov. 23, 1970, Ser. No.
172,922 filed Aug. 16, 1971, and Ser. No. 219,327, filed Jan. 20,
1972.
For purposes of the discussion below it is assumed that the coin
selector 110 is designed to accept coins of only one denomination,
although it is clear that the coin selector is capable of
distinguishing several different coins by employing the disclosed
techniques.
The coin, being impelled by the impeller 80 toward the right in
FIG. 4 passes a pair of conventional sensors or detectors such as
inductive switches, photoelectric devices, etc. In this discussion,
photocells are used as sensors. Light sources (not shown) and
photocells 132, 133 are mounted on opposite sides of the track 122,
the photocells being located close together and in close proximity
to the impeller 80. As the coin leaves the impeller 80 it occludes
the first sensor 132 which sets a flip flop 136 enabling an AND
gate 138. When the coin occludes sensor 133, the flip flop 136 is
reset, disabling the AND gate 138. The interval during which the
flip flop 136 is set is inversely proportional to the coin velocity
and, therefore, is inversely related to the coin's acceptance
ratio.
The output pulses of timing oscillator 140 are fed to the enabled
AND gate 138 from which they are gated into a counter 144. The
output of the counter, which is fed to a decoding matrix 146, is
inversely proportional to the velocity of the coin. The output of
the decoder 146 is fed to flip flop 150. A flip flop is set by the
count representative of the lower limit of acceptable velocity for
the particular coin denomination which the flip flop represents and
is reset by the count representative of the upper limit of velocity
of that particular coin. If a coin having a velocity within the
range of an acceptable coin passes through the system, flip flop
150 will be set indicating that a coin which has passed through the
system has a velocity within a range equal to the velocity range
that an acceptable coin would have after acceleration by the
impeller.
An accurate examination of a coin's velocity may not be sufficient
to accurately determine the authenticity and denomination of a
coin. It has been found that the information obtained from
conducting both an examination of a chordal dimension of the coin
and an examination of its velocity provides sufficient information
to confidently determine the coin's authenticity and
denomination.
One method of determining whether a coin's diameter or other chosen
chordal dimension is within an acceptable range is illustrated in
FIG. 4. A pair of sensors 132, 135 corresponding to each acceptable
coin is employed in combination with a primary sensor 133, the
sensor 135 closer to the primary sensor checking the minimum
acceptable dimension and the sensor 132 further from the primary
sensor checking the maximum acceptable dimension. The distance
between the pair of sensors 132, 135 is equal to the acceptable
dimensional variation of a particular coin and the distance between
the sensor 135 and the primary sensor 133 is equal to the minimum
acceptable dimension for that coin. The inverted output from the
sensor 132 and the output from the sensor 135 are fed to separate
inputs of an AND gate 139. The primary sensor 133 is connected
through a capacitor 143 to the input of an inverting gate 147. A
source of power sufficient to operate gate 147, in this case 5
volts, is also connected to the same input through a resistor 145.
The output of gate 147 is connected to an input of AND gates 139.
When the primary sensor 133 is first obscured, capacitor 143,
resistor 145 and the voltage applied through resistor 145 produce a
short pulse at the input of AND gate 139. If a coin passing through
the coin selector 110 has a particular dimension larger than the
distance between the primary sensor 133 and the nearest sensor 135
but smaller than the distance between the primary sensor 133 and
the furthest sensor 132, and flip flop 150 is set when sensor 133
is first occluded, then AND gate 139 is enabled when the coin first
occludes sensor 133 and a flip flop 141 is set indicating that a
coin of acceptable dimension and velocity has passed through the
selector.
Since each pair of sensors 132, 135, each AND gate 139 and each
flip flop 141 represents one coin, the number of these elements
used equals the number of denominations of coins the coin selector
110 is designed to accept. Also, each acceptable coin has a
corresponding coin velocity flip flop (for example flip flop 150)
and the output from this flip flop can be fed to the AND gate 139
for that coin so that when the flip flop 141 is set it indicates
that both the chordal dimension and coin acceptance ratio dependent
velocity of the coin passing through the coin selector 110 is the
same as those properties of a particular acceptable coin.
Impeller Current Control of Clock Oscillator Frequency
The acceleration of the coin is proportional to the current through
the impeller coils. The coil current is dependent on the magnitude
of the exciting or source voltage and the impedance of the impeller
windings. Conventional A.C. supply voltage varies by at least
.+-.10 percent and the resistance of the windings changes by a
similar amount due to temperature, manufacturing variances and
minor variations in wire diameter. Because the coin velocity is
dependent upon the strength of the impeller's magnetic field, and
the magnetic field strength is dependent upon the voltage supply,
supply voltage variations cause a resultant change in coin velocity
and, therefore, a change in the elapsed time during which coins of
the same denomination pass between the two sensors 132, 133. If the
clock oscillator 140 which feeds pulses into the counter 144 has a
constant frequency regardless of the impeller coil current, the
number of clock pulses gated into the velocity counter 144 will
vary with changes in impeller current for identical coins and could
indicate unacceptability of a coin which actually is
acceptable.
To overcome this problem a feedback signal derived from the
impeller current source 100 is applied to the clock oscillator 140
by the circuit 152. The impeller 80, including the coils and phase
shift capacitor, receives its current from the supply 100 and a
current sampling resistor 154 is placed in series with the impeller
80. The clock oscillator 140 is a voltage controlled oscillator and
the control voltage is supplied by means of a transformer coupling
156 the primary of which is across the current sampling resistor
154. The oscillator current is caused to be of the proper polarity
by circuit 152 so that as the impeller current increases thus
increasing the coin velocity and reducing the time interval during
which the clock pulses are gated into the counter 144, the
oscillator frequently is increased. The higher oscillator frequency
provides a greater number of pulses to the counter 144 to
compensate for the shorter gate time. Conversely, when the impeller
current decreases and the coin velocity decreases, the oscillator
frequency is decreased to gate fewer pulses into the counter during
the longer gate time. Therefore, while the coin's actual velocity
varies considerably because of supply voltage variations, the
apparent velocity is normalized to within 1 percent or 2 percent by
this system.
Switched Direct Current Energization of Impeller (FIG. 5)
Instead of using power line frequency A.C. to energize the impeller
80, in some instances, it is advantageous to use switched D.C. The
circuit illustrated is FIG. 5 is one technique which can be
utilized. There is illustrated two dual clocked R--S flip flops
160, 162 whose operation is described by means of the table shown
in FIG. 5A and the logic voltage diagram 5B. The dual flip flops
are interconnected in a manner which, at the frequencies involved
(e.g.: under 4,000 Hz) eliminates the possibility of ambiguity
associated with simultaneous similar logic states at the "S" (set)
and "R' (reset) inputs of each dual flip flop. The dual clocked
R--S flip flops 160, 162 do not change state until a positive input
pulse is received. Flip flop 160 is readied to change state by a
coin entering the system such as by means of the start control
system 120. When the first positive clock input pulse is received
transition takes place (t.sub.1) and the change of state of Q.sub.1
and Q.sub.1 readies flip flop 162 for a change of state, which
change occurs at the next positive clock pulse (t.sub.2). When
Q.sub.2 and Q.sub.2 change state flip flop 161 is readied for a
change of state which occurs at the next successive positive clock
(t.sub.3) and so on.
The outputs of the flip flops 160, 162, which have a quadrature
phase shift relationship, are used to drive pairs of full-wave
switches 164, 165 and 166, 167 respectively to enable alternate
excitation of center-tapped windings 168, 169 of a two phase
impeller by a D.C. source 170. This produces a quadrature phase
shift in the impeller windings 168, 169 effecting a traveling
magnetic field.
The D.C. resistance of the impeller windings changes with changing
winding temperature which, therefore, effects the magnetic flux
magnitude. Compensation for these changes can be made by regulating
the impeller supply voltage. This is accomplished by placing
temperature sensitive elements, such as nickel wire resistor 172,
173 in physical contact with the impeller windings 168, 169
respectively and wiring it into a conventional voltage divider 174.
Temperature changes are experienced concurrently by the impeller
windings and the temperature sensitive elements 172, 173. This
circuit provides a sufficient voltage regulation to maintain an
approximately constant impeller flux over the expected temperature
range, the flux being sufficiently constant for the purposes for
which it is used.
Fourth Embodiment (FIG. 6)
The use of an electronic or photoelectric sensing system as
described above for sensing the properties of a moving coin
provides an immediate determination of the acceptability of a coin.
Furthermore, also as described above, it is a simple matter to
reverse the direction of magnetic field travel produced by the
impeller. In this fourth embodiment, illustrated in FIG. 6, the
sensors 132, 133 are located within the magnetic field region, for
example, within the pole pieces or between adjacent coils
intermediate the ends of an impeller 200. Several opportunities to
utilize the impeller for additional functions are provided by the
capability for reversing the direction of a coin drive at a
suitable moment during the coin's travel past the impeller 200 and
determining the acceptability as well as the denomination of
acceptable coins at an instant when the coin remains under the
influence of the impeller. For example, the length of coin travel
can be reduced by decelerating the coin through reversal of
magnetic field direction immediately after determination of the
coin's authenticity and denomination. A substantial spacial
separation of differing coins also can be achieved by selected use
of coin deceleration or acceleration dependent upon the results of
the determination of the coin's authenticity and denomination. In
this manner, all rejected coins can be directed to a rejection
chute while acceptable coins can be individually directed to an
appropriate receptacle for the coin's particular denomination.
One construction for conserving space which can be utilized is
schematically illustrated in FIG. 6 where a wall 202 is spaced
downstream from an impeller 200 and coin support track 203 a
distance slightly greater than the diameter of the largest coin
which can be admitted to the coin selector. After the coin leaves
the impeller 200, the coin abuts the wall 202 and tends to rebound
toward the impeller 200; however, gravity prevents the coin from
returning to the coin track. The coin therefore drops downwardly
between the impeller 200 and the wall 202 toward a solenoid
controlled inclined platform 204. If the coin is determined to be
acceptable by logic circuitry of the type illustrated in FIG. 4, a
control solenoid (not shown) is actuated to retract the platform
204 from the path of the coin allowing the coin to fall into an
acceptance chute 206. If the coin is not acceptable, either because
it is not authentic or because it is of an improper denomination,
the control solenoid is not actuated and the coin strikes the
platform 204 and bounces into a rejection chute 208. The amount of
space required for this coin sensing device is minimized by
elimination of the space normally alloted to accommodate the coin's
trajectories.
Impeller Series (FIG. 7-9)
Some of the advantages of placing the sensors within the impeller
region as described above can be achieved by using a second
impeller located downstream from the sensors. Turning now to FIG.
7, there is schematically illustrated a coin selection system 220
having a primary impeller 222 which, as described earlier with
reference to FIGS. 3 and 4, accelerates electrically conductive
coins. The velocity and chordal dimension of the coin are examined
by the sensors, shown as a unit 218, located immediately after the
impeller 222 and the determination of coin acceptability and
denomination is made by a combinatorial circuit as described
earlier. A secondary impeller 226 is located immediately after the
sensor unit 218 and, depending upon the determination already made
of the coin's acceptability and denomination, the secondary
impeller either decelerates or accelerates the coin at a
predetermined magnitude so that the coin may be propelled into a
proper chute such as chute 227 for rejected coins, chute 228 for
nickels or chute 229 for dimes.
An alternative to this latest embodiment is illustrated in FIG. 8
wherein the primary impeller 222 additionally serves as a secondary
impeller. After the coin is accelerated by the impeller 222 and
passes the sensor unit 218, it rolls up a curved inclined portion
of the coin support track 230 and eventually is returned by gravity
toward the sensor unit 218 and the impeller 222. During the first
pass of the coin by the sensor unit 218, the sensor unit, with
associated logic circuitry such as shown in FIG. 4, compares the
coin's velocity and chordal dimension with respective properties of
acceptable coins so that by the time the coin returns, the coin
analysis is complete. Depending upon the results of the
examinations of the velocity and chordal dimension of the coin,
during the return pass of the coin by the impeller 222, it
accelerates the coin at different rates. This system sorts
acceptable coins from the unacceptable coins and also separates the
acceptable coins by denomination. Because the initial portion of
the track 230 also serves as the exit a removable wall or stop 232
is provided. As a coin enters the system, it is forced to rest
against the stop 232 by the impeller 222. The field direction of
the impeller is then reversed and the coin is impelled toward the
sensor unit 218. A solenoid (not shown) retracts the stop 232 out
of the coin passageway to permit the coin to move off the track
into the appropriate chute 227, 228 or 229. The stop 232 returns to
its initial position after a predetermined time interval.
It is possible to reduce the number of sensors required and
simplify the logic circuitry needed to perform coin discrimination
by the use of a plurality of small impellers and coin support
tracks. Such a system is illustrated in FIG. 9 wherein three
inclined coin tracks 270, 272, 274 and three corresponding
impellers 276, 278, 280 are employed. The tracks and impellers are
located such that a set of one track 272 and one impeller 278 is
immediately below the lower end of the first impeller 276 and track
270 and the third impeller 280 and track 274 are located below the
higher end of the first impeller 276 and track 270. The slope of
each of the tracks depends upon the particular coin set with which
the system is intended to be used. Three solenoid control stops
282, 284, 286 and three arrival sensors 288, 290, 292 are provided,
one stop and one arrival sensor for each of the impellers 276, 278,
280.
A coin introduced to the system through an entrance slot 294 passes
through a meander path 296 and by an arrival sensor 288 and
eventually falls onto the first track 270 where it rests against a
stop 282. Since the track 270 is inclined, the coin will roll
toward the stop 282 and come to rest and there is no need for the
impeller to move the coin toward the stop 282. After a
predetermined period of time sufficient to allow all coins to come
to rest the impeller 276 is energized as described above and,
concurrently, the solenoid controlled stop 282 is removed from the
path of the coin to prevent interference with the movement of the
coin. The coin, depending upon its diameter, acceptance ratio and
weight either will roll down the track 270 falling off the lower
end thereof or roll up the track 270 falling off the upper end
thereof. In this manner, the first track 270 has performed an
initial sorting function.
A coin which rolls off the lower end of the support track 270
passes the coin presence sensor 290 and falls onto the second coin
track 272 where it comes to rest against the solenoid controlled
stop 284. After sufficient time has elapsed the impeller 278 is
energized and the stop 284 is removed by a solenoid (not shown) and
a secondary discrimination is performed. Those coins which can be
impelled up the track 272 by the impeller 278 roll off the upper
end of the track in a spacial pattern dependent upon the coin's
acceptance ratio, weight and diameter and are collected in the
chutes 294. Similarly, those coins which cannot be impelled up the
track 272 will roll off the lower end of the track in a spacial
pattern similarly representative of their acceptance ratio, weight
and diameter and are collected in chute 295. A similar
discrimination is performed by the third roll track 274 and
impeller 280. In this fashion, at least four separations are
available, namely, at the upper and lower ends of the tracks 272
and 274. Because of the spacial separation pattern which coins take
due to the different velocities attained while on the tracks, a
greater number of discriminations are available. FIG. 9 illustrates
two chutes 294 at the upper end of each of the tracks 272, 274 and
two chutes 295 at the lower end of these tracks for receiving eight
categories of coins.
A particularly appropriate application for a coin sensor utilizing
this structure is as a denominational sorter of legitimate coins
for use by coin collector entities such as vending companies,
banks, supermarkets, etc., where the incidence of counterfeit and
totally unacceptable coins is low because the coins are given an
initial visual or coin sensor screening. A typical user would be
the operator of some of the many vending machines which have a coin
sensor which does not separate the acceptable coins by
denomination, but merely places them in a common collection
receptacle.
If desired, coin presence sensors such as photocells 296 may be
located at the entrance to each of the coin chutes 294, 295 which
receive the coins leaving the impellers with the output of the
sensors being directed to a totalizer for calculating and recording
the value of coins sorted.
Inclined Impeller (FIGS. 10 and 11)
It has been found that often coins of two different denominations
having the similar composition and only marginally differing
diameters are accelerated to similar velocities by an impeller
aligned parallel to the support track. In order to induce a greater
velocity separation between such coins of different denominations,
an impeller 300 having a tapered pole structure may be used. As can
be seen in FIG. 10, the height of the impeller is varied from a
dimension approximately equal to the diameter of the smallest
acceptable coin 302 at one end 304 of the impeller to a dimension
approximately equal to the diameter of the largest acceptable coin
306 at the other end 308 of the impeller. The smaller coin
experiences an almost uniform flux throughout the length of the
impeller 300 while the larger coin experiences a flux whose
magnitude is a function of position along the impeller.
In addition to the variation in flux magnitude experienced by coins
of different sizes, the location of the flux relative to the coin
support track 310 also varies and plays an important part in the
acceleration of the coins. The point about which the coins rotate
as they roll down the track is the point of contact of the coin
with the track. Given equal forces on the coin tending to make it
rotate, the higher the force is located on the coin with respect to
the track the more effective the force will be since the moment arm
about the point of rotation will be greater. Looking at the coins
at the beginning of the track 310 in FIG. 10, it can be seen that
the forces on the small coin 302 are exerted over the entire height
of the coin whereas the forces exerted on the larger coin 306 are
exerted on the lower half of the coin. Because of the moment of
inertia of a coin is a function of its diameter and because the
coin acceleration is a function of the distance from the
application of the moving force to the point of rotation of the
coin, it can be seen that the acceleration of the coins will vary
significantly depending upon the coin's diameter and the slope of
the tapered impeller 300. As with the previous embodiments, after
the coin leaves the impeller 300 its chordal dimension and velocity
are examined by a sensor array 309 and associated combinatorial
circuitry.
A similar result can be achieved by using a rectangular inclined
impeller 312 as illustrated in FIG. 11. It can be seen that the
smaller coins can be exposed completely to the magnetic field at
the beginning of the coin support track 314 while only a small
lower portion of the larger coin 306 is exposed to the magnetic
field at the beginning of the coin track. As the coins progress
down the track, a smaller percentage of the small coin 302 is
exposed to the magnetic field while the point of application of the
magnetic field on the larger coin 306 rises providing a larger
torque and resulting in increased acceleration of the larger coin.
Since the acceleration of coins of different sizes vary as the coin
proceeds down the track 314 it is desirable to sense coin
acceleration between two points along the path of coin travel. This
is accomplished by locating two spaced apart photocells 316, 318 so
that the coins pass the photocells while they are under the
influence of the impeller 312. By using circuitry of the type
described above with respect to FIG. 4, the time interval which the
coin moves from the first photocell 316 to the second photocell 318
is recorded by a counter and, through the use of comparative
circuitry, such as flip flops, a determination is made concerning
the authenticity and denomination of the impelled coin.
* * * * *