US2052397A - Coin controlled mechanism - Google Patents

Description

Aug. 25, 1936. R. M. HALL 2,052,397

COIN CONTROLLED MECHANISM Filed Dec. 22, 1934 4 Sheets-Sheet 1 Aug. 25, 1936. R HALL 2,052,397

COIN CONTROLLED MECHANISM Filed Dec. 22, 1954 4 Sheets-Sheet 2 INVENT Y M. HALL,

R0 BY ATTO NEY Aug. 25, 1936. R 2,052,397

COIN CONTROLLED MECHANISM Filed Dec. 22, 1934 4 Sheets-Sheet 3 I INVENTOR Row Hm,

Aug. 25, 1936. R HALL 2,052,397

COIN CONTROLLED MECHANISM Filed Dec. 22, 1934 4 Sheets-Sheet 4 INVENTOR Patented Aug. 25, 1936 UNITEDSTATES PATENT OFFICE 2,052,397 COIN CONTROLLED MECHANISM Roy M. Hall, Jackson'Heights, N. Y.

Application December 22, 1934, Serial No. 758,781

18 Claims.

This invention relates to coin controlled mechanism and has for its object to provide a device of this class which is more selective and better able to reject slugs than have been existing mechanisms. Another object .is to provide such a mechanism ;capable of automatically rejecting slugs of less than the desired degree of hardness.

A further object is to make a coin controlled apparatus which is capable of automatically rejecting slugs of magnetic material. Yet another object is to provide a coin controlled mechanism which, in addition to testing for hardness, and magnetic material, also tests and selects only those coins or checks which are of intended size, andweight.

Referringto the drawings: Fig. 1 shows one embodiment of this invention applied to a gasoline pump.

.' Fig. 2 is a rear view'of the coin handling mechanism.

Fig. 3 is a cross section of the coin slot with the hardness tester.

Fig. 4 is a-front view of the device of Fig. 2.

Fig. 4a shows the gate 33 clear of the channel.

Fig. 4b is a view on the line 4b-4b of Fig. 9.

Fig. 5 shows the weighing mechanism in position for passing a coin.

Fig. 6 showsa wiring diagram of the electrical connections.

Fig. '7 shows the hardness responsive gate blocking the passage of coins through the channel.

Fig. 8 is a detail corresponding to Fig. 4, but with the coin in position'to release the locking mechanism, just prior to actuation of the dispensing mechanism.

Fig. 9 is a top plan view of the plunger and slide in normal position. n

Fig. 10 is a side view of the channel through which the coin moves. showing the extracting magnets in position.

Fig. 11 is a diagrammatic outline of this invention applied to a telephone coin box.

Fig. 12 is a rear view showing hardness gate resetting mechanism.

The gasoline pump shown in Fig. 1 is adapted to be operated by a coin inserted in the slot l0. On pushing in the plunger II the dispensing mechanism is unlocked so that by rotating the handle l2, in a clockwise direction, the gasoline lights on moving in the plunger l I. A bull's-eye l4 enables an operator to see signal lights inside the housing of the mechanism and also permits observation of the coin slot or channel to determine whether the same is clogged.

In Fig. 4, a coin l 5 is shown entering the channel"; along which the coin moves. there being a gate ll closing the channel below the gate to coins of less than the desired weight. The gate I1 is pivoted to the ball bearing support for movement about its axis. A mercoid or other type liquid level switch I9 is carried by the outer portion of the ball bearing l8,'and is so arranged that on tilting the circuit is closed through the lamp 20. .Fig. 5 shows a coin beingpassed by the gate I1. In returning to its normal position, the gate II has attached thereto a hammer 22 which strikes the bell 2| signalling the movement of a coin past the gate.

A hardness tester for coins comprises a rotatably mounted tool having a sharp edge 23 like a diamond cutter. This tool normally projects slightly into the coin channel so that it may engage an edge or peripheral portion of a coin. If a slug of soft material is passed, the tool 23 cuts into the edge portion of the slug and is not retracted or moved out of the channel, as is the case when a genuine coin of desired hardness moves past the tool. On passage of a genuine coin, the tool 23 is moved to the left in Fig. 3, moving the rod 24 and compressing the spring 24a. This motion is transmitted to the lever 25 pivoted at 26, causing the lower end 21 of the lever to swing to the right in Fig. 4, and as viewed from the back in Fig. 2 the movement is to the left, swinging the lever 28 pivoted at 29 so that its opposite end portion 30 raises the sliding bar 3|. The upward movement of the bar 3| causes the pin 32 to be engaged with the result that the gate 33 to which the pin 32 is connected is swung in a counter-clockwise direction in Fig. 2 and a clockwise direction in Fig. 4, so that the gate 33 clears the channel along which the coin passes. The gate 33 is pivoted at 34 and carries a counterweight portion 36. The gate 33 also has an arm 35 which projects into the coin channel when the gate 33 is open. With the gate closed, as shown in Fig. 4, soft slugs, which are heavy enough to move the gate l1, engage thegate 33 andv are directed out the ejecting channel 39 shown in Fig. 4 as leading to the right for either discharging the soft slugs into a special compartment within the housing or discharging them to the outside. When a genuine coin of requisite hardness is inserted into the slot, the gate 33 is rotated in a clockwise direction by the lever mechanisms just described, to clear the slot, as shown in Fig. 4a.

While the "gate 33 .clears the channel or slot, the arm 35 extends into the channel into the path of the moving coin and as the genuine coin passes the arm 35, the gate 33 is rotated back into position closing the channel again. v

If a slug or coin of less than the necessary weight is inserted into the channel, the gate I! does not fully open, and the lightweight coin or slug is held in the channel by the gate H. However such a light weight object will unbalance the scale or weight arm I! closing the circuit through the signal light 20 which is located close enough to the bull's-eye l4 to illuminate the same at night. A buzzer 45 is included in the lamp circuit and provides an audible signal indicating that another coin should not be inserted until after the housing has been unlocked and the lightweight coin manually cleared. If, however, another coin should be inserted on top of a lightweight one clogging the channel, the combined weight of both may enable them to pass the gate H, but the first one engaging the arm 35 causes the gate 33 to be rotated into a position closing the channel and holding both coins from passing through, as is shown in Fig. '7. Such a, condition is visible through the bulls-eye I4, and requires an operator to manually clear the channel by opening the front of the housing. The signal light 20 and the buzzer 45 will have been actuated by the presence of the lightweight coin until such time as the second coin is added to clear the gate IT, and this signal in addition to the coins being seen through the bulls-eyewhen clogged as shown in Fig. '7 is sufiicient to warn a customer not to insert any additional coin. Full directions for operating the device will be found printed upon the front of the housing.

In manually clearing the coins from the position of Fig. '7, the upper coin 38 is held in a slightly elevated position while the lower coin 31 is allowed to rotate the arm 35 sufliciently to pass through the mechanism.

For ejecting slugs of magnetic material which may be of the requisite weight and hardness, magnets 40 and M are arranged as shown in Fig. 10 for the purpose of tilting the iron slug out from the main channel into an auxiliary channel 44 on the back of the device, from which the magnetic slugs may be either ejected to the outside or discharged into a separate compartment within the housing. The upper magnet 40 has a pole piece 42 of the shape illustrated in Fig. 4, while the lower magnet has a pole piece 43. Having the lower pole piece provided with a greater flux density and of the shape illustrated prevents an iron slug from being held fast and clogging the channel, since it is permitted to move down across the faces of the pole pieces into the channel 44. As shown in Fig. 6, these magnets are in circuit'with the lamp 20 and the buzzer 45, all being actuated by the switch l9 through a step-down transformer 46. Inasmuch as the magnets are located at about the height at which the gate I1 is when it clears the channel, it will be appreciated why the magnets will be satis factorlly energized, when it is remembered that the gate l1 must rise to the position shown in Fig. 4 with the switch l9 horizontal, before the circuit is opened, see the wiring diagram in Fig. 6

After passing the arm 35, a genuine coin then moves down the channel until it is held between the end portion 41 of the plunger II and the end portion 48 of a slide 50.

In this position, the coin is shown in, dotted lines in Fig. 4. On pushing the plunger I l to the left in Fig. 4 and moving the coin laterally to the left, the slide 50 also moves to the left. This slide carriesa cam 5| with which is engaged a roller 52 on the end of a member 53 so that the member 53 is raised as the cam 5| and slide 50 move to the left. Upward movement of the member 53 causes the lever 54 to be engaged and swung upwardly about its pivot 55 until the latch 56 is clear of its cooperating recess. The end portion 51 of the lever 54 is secured to a switch 58 which closes a circuit through the lamp l3 in the upper portion of the storage tank to enable the customer to see clearly in pumping and draining the gasoline.

The handle i2 is connected to its shaft through a slipping clutch 64, and on this shaft is mounted the gear 60 meshing with the gear 6|. The gear 6! carries the cam 62 and is provided with the locking recess in which the latch 56 engages. The handle shaft also carries a gear 63a meshing with the gear 65 to drive the pump or other dispensing mechanism, The gears 63a and 65 are preferably changeable in size so that with a change in the price of gasoline there may be a corresponding change in quantity of material which can be pumped or dispensed for one coin, such as a quarter.

As long as the latch 56 engages the recess in the cam portion 62, none of the gears 69, 6!, 63a or 65 are enabled to turn, but as soon as the latch 56 is moved up enough to clear the recess, these gears may then be turned by the handle. The slipping clutch 64 safeguards these gears against having their teeth broken under heavy impact, for example on the handle member.

The plunger II is provided with a recess 59 as shown in Fig. 9, and this recess becomes aligned with the channel l6 when the plunger has been moved to the left, so that if any coin should be inserted while the plunger is to the left, it will pass through the machine without being able to operate the dispensing mechanism. To guard against this the switch to be later described actuates a lamp which is visible through the bulls-eye.

On pushing the plunger II to the left against the action of the spring 49, an extension 66 pivotally secured at 63 to an arm of a bell crank lever pivoted at 61 is actuated thereby. The other arm of this bell crank lever is arcuate in shape, as shown at 69. A spring 10 tends to move the lever 69 in the same direction that the spring 49 tends to move the plunger. The lever arm 69 may either be arranged in front or behind the gear 60, and shaped so as to clear this shaft.

0n movement of the slide 50 to the left, a switch member H engages the contacts I2 to close a circuit through a lamp 13 arranged close enough to the bulls-eye for its light to be visible. This lamp I3 is preferablyof a different color from the lamp 20, and on illumination of this signal means 13 an operator is informed that the plunger and slide are not in position to receive another coin, so that this other coin should not be inserted until after the signal light 13 has been extinguished.

On the under side of the portion of the slide 50 engaged by the spring plungers 14, are a plurality of shallow recesses into which one or both of these plungers may engage for the purpose of 75 I, a 7 ,059,897- retaining the slideiin such position. A unit spring 15 tends to move the slide to the rights, as shown'in Fig. 8, but this spring 15 is notstrong enough to pull the slide out of positions where held by plungers 14. i When the latch-56 unlocks the gear 6|, the

handle l2 may be rotated in a clockwise direc- I tion causing a rotation of the gear 8| in a eoun-= tar-clockwise direction. As the cam 62 rotates about 90 degrees, more or less, it engages the lever arm 69 moving the same to clear the cam. This movement of the lever 69 shifts the plunger to the right by meansofithe' bell crank lever 68, and alsocauses the slide 50 which engages the right end of the lever 39 to be moved slightly to the right, but not all the way, due to the plungers 14 holding the slide in another position.- When the cam 62 has-rotated, about three-quarters of a revolution or less, the cam directly engages the slide 50 to fullyretum' the same to its initial position. I i

When a coin is-inserted between the ends 41 and 48 of the plunger and slide, it rests on these ends, and movement of the plunger to the left moves the coin and the slide. Unless the coin is of the desired diameterfl; the slide will not be moved far enough for the latch 56 to clear its recess and unlock the dispensing mechanism. When it does clear such/recess the handle I2 is then permitted to pump gasoline into the tank. When the cam 62;en'gages the lever arm 69 and the plunger is returned to its original position, the coin is no longer held and is then free to roll down the support 16 which has a decided slope downward to the right'until the coin enters the partment in theibottom' of the housing, or is carried to-any desired point outside the mecha- ,nism. The channel 11 is substantially in concontaining the bulls-eye-'is mounted on hinges [19, whereas the portion over the coin compartment is mounted on hinges 80 and adapted to be opened only after the front 18 has been unlocked. i

In Fig. 11 is shown -a diagrammatic representation of thisinvention applied to a telephone coin box. 'mme slot for nickels is arranged the weight responsive gate "a, the magnetic extraction means-having the pole pieces 12a and 43g. abovethe gate 33a operated in response to the hardness testing tool 23a, as was described more in detail in the preceding figures of the drawings. Similar devices are located in the slots for dimes and quarters. Below the coin channels for each: denomination is located a common channel 8| 'into which a coin of each denomination maygenter A gate 32 is pivoted to swing lnone direction for depositing the coin within the, machine when it moves down the channel 83. When thegate 82 swings in an op-' posite direction, the-coin contained therein is delivered through the channel 84 to be returned a While this invention has been illustrated in connection with a gasoline pump. and a telephone ,coi-nbox, it will be understood that such a coin controlled mechanism is adapted for use withv dispensing apparatus of a wide variety of types and materials.

Among the advantages of this invention may bementioned the testing and rejecting of coins .or slugs of less than a standard degree of, hardness. By adjusting the tension of the spring 24a and the screw 25a, the degree of hardness may be varied, or, in other words, the amount of.

movement of'the tool 23 and its resistance to movement may be controlled.

Another advantage is. the testing and rejecting of coins, or slugs according to their magnetic properties, those of magnetic material being extracted without clogging the coin passage. A noteworthy feature is the location and arrangement of the magnet pole pieces so that a slug of magnetic material is not held fast, but is enabled to roll and slide in tilting into a branch passage. The'weight testing is another desirable feature in the combination illustrated. The use of signals in connection with these testing means is an advantage. The stronger magnet being located below the weaker causes the magnetic material to continue its movement and not be stopped. The cam M on the slide 50 does not raise the latch 56 the desired amount unless a coin of thenecessary diameter is within the space between the slide and plunger. The plunger only has a certain amount of movement and if there is a smaller coin in place, the full movement of the plunger will not be transmitted to the slide, and therefore the dispensing mechanism will not be unlocked. The plunger may or may not be returned under the action of the springdB. The movement of the plunger away from thecoin before the slide is returned gives ample time for the coin to roll back and into the channel 16. For this reason, the two step movement of the slide is of advantage.

While Fig. 6 shows a preferred diagram of the electrical connections, other arrangements with or without a transformer may be found convenient.

The opening at the entrance to the coin channel I6 is of a width and length just sufiicient for coins of the intended denomination so that larger coins or thicker coins will be excluded. If the lightweight coin which is stopped by the gate H, as wellas the subsequent coin, are both of soft material, then the gate 33 will not have been swung clear of the channel l6 with the result that both coins will be deflected by the gate 33 and the channel 39 in the same manner, as will be the case with any soft slug. In other words, the condition illustrated by Fig. 7 does not arise unless at least one of the two coins is of the requisite degree of hardness.

After the cam 62 has returned the slide 50 to its initial position the latch 56, being no longer held up by the cam 5!, falls into contact with the cam 62 and is raised by the cam 62 until it comes into cooperation with its recess, at which time the latch 56 falls into the recess, locking the dispensing mechanism until another coin is inserted and the plunger moved to the left. In this way no more than one coins worth of material is dispensed at a time.

The channel 44, along which slugs of magnetic, material are ejected, extends in the opposite direction to the channel for rejecting soft slugs, although, of course the direction of these ejecting channels is relatively unimportant, so long as the selection and extraction of slugs for weight, hardness, and magnetic material, is made possible.

The latch 58 and its cooperativerecess are preferably made dove-tail in shape, inasmuch as this has been found advantageous in order to avoid danger of the latch being accidentally jarred out of its recess to unlock the dispensing mechanism. As shown in Figs. 4 and 8, the lagging side of the latch recess is made higher than the leading side, in order that the possibility of the latch not falling into position as the cam 82 is turned, may be minimized. In other words, having the lagging side of the cam 82 higher insures the gear 6| being turned only through'one revolution.

A counter 85 may be visible through the housing in order to record the number of revolutions made by the dispensing gear 80.

Having the right end of the lever arm 69 arranged in position to be engaged by the cam 62, after the cam has cooperated with the left end of this lever arm, as shown in Fig. 4, is an additional insurance against the plunger ll being again moved to the left, should an effort be made to do so before the coin has had a chance to roll away from the slide and down the channel 11. As previously described, the plunger H is returned to its original position when the cam 62 engages the left end of the lever arm 68. Just before the cam 62 engages the slide, it engages the right end of the lever arm 69 to insure the plunger being moved to its original position and to prevent the same coin being again used to release the latch 56.

It has been found that the use of two spring plungers l4 engaging their cooperative recesses on the under side of the portion 50 are effective in delaying the return movement of the slide 80 as to insure the coin being returned to the channel 11.

In Fig. 11, the various outlet channels for slugs of magnetic material and for slugs of soft mate- 'rial have not been shown, but it will be understood that such are provided. There may be one outlet channel for slugs of magnetic material from all three coin channels, and also there may be one outlet channel for soft slugs from all three coin channels, or, if desired, there may be separate slug outlet channels for each of the main coin channels in Fig. 11.

If a hard iron slug is inserted in the coin slot it will open the gate 33 just as would a good coin, but is pulled out by the magnets 40 and 4| and discharged down the channel 44. As previously described there is nothing to reset the gate 33 which remains open so that if a soft slug is inserted after the hard iron slug has been ejected it would be able to pass the open gate 33, and enable the dispensing mechanism to be operated. To avoid this possibility the mechanism for resetting the gate 33 is shown in Fig. 12. As the hard slug passes down the channel 44 it passes over the lever 86 pivoted at 81, causing the right end of this lever to be swung down and the left end which is generally shorter and provided with a counter-weight 88, is swung up causing the lever 89 to be slightly rotated in a counter-clockwise direction engaging the pin 32 and moving it down effecting a closing of the gate 33 to the position shown in Fig. 4. The weight of the hard slug passing along channel 44 is sufflcient to accomplish this reclosure of the gate 33. After gate 33 is closed there is then no danger of a soft slug being able to actuate the dispensing mechanism. The weight 88 is sufficient to raise the right end of lever 88 above the position shown in Fig. 12 ready to be tilted down again by another hard slug. When a hard slug or coin is inserted it opens gate 33 as first described and in raising the pin 32 the lever 89 is moved without contacting with thelever 88 since the left end of 83 is normally maintained in a lower position than that shown in Fig. 12. The counter-weight 88 is just heavy enough to raise the right end of lever 86 in Fig. 12. The levers 88 and 89 have not been shown in any of the other figures for the sake of simplicity but it will 7 be understood these levers are present in all embodiments of the invention including that shown in Fig. 11, in order to make the apparatus fool proof.

I claim:

1. A coin controlled mechanism having therein a channel along which a coin is passed, a gate for ejecting soft slugs from said channel, means for closing said gate, and means actuated by the movement in said channel of a coin of predetermined hardness for moving said gate clear of said channel, said last-mentioned means being substantially unaffected by a coin of the same size and of less hardness than a genuine coin.

2. In a coin controlled mechanism, a hardness tester comprising a tool located adjacent the input end of a slot through which a coin is inserted and arranged to roll on the edge of a coin as same is being inserted into said slot, means for holding said tool, yieldable means pressing said tool into said slot whereby the edge will cut into a soft slug but not intoa coin of predetermined hardness, and means responsive to a predetermined movement of said tool and holding means for ejecting a soft slug.

3. In a coin controlled mechanism, a hardness tester comprising a tool located adjacent the input end of a slot through which a coin is inserted and arranged to roll on the edge of a coin as the same is being inserted into said slot, means for holding said tool, yieldable means pressing said tool into said slot whereby its edge will cut on a soft slug but not on a coin of predetermined hardness, a channel along which a coin passes after entering said slot, a gate closing said channel, mechanism responsive to movement of said tool and holding means for opening said gate to allow passage of a coin through said channel, and means for closing said gate in response to movement of a genuine coin through said channel.

4. In a coin controlled mechanism, a hardness tester comprising a tool located adjacent the input end of a slot through which a coin is inserted and arranged to roll on the edge of a coin as the same is being inserted into said slot, means for holding said tool, yieldable means pressing said tool into said slot whereby its edge cuts into a soft slug but not on a coin of predetermined hardness, a channel along which a coin passes after entering said slot, a gate closing said channel, and mechanism responsive to a predetermined movement of said tool and holding means for opening said gate to allow passage of a coin through said channel, and means independent of said tool and responsive to movement of a genuine coin through said channel for automatically closing said gate after such a coin has passed along the portion of the channel adjacent said gate.

5. A coin controlled mechanism having therein a channel along which a coin is passed, a gate for ejecting soft slugs from said channel, means for opening said gate when a hard coin or slug is inserted in said channel, magnetic means for ejecting a hard coin of magnetic material, and

means responsive to the discharge of a slug of magnetic material for closing said gate;

6. A coin controlled mechanism having therein a channel alongwhich a coin is passed, a gate for closing said channel for ejecting a soft slug therefrom, means adjacent the entrance of coins into said channel which is adapted to move when actuated by the passage of a coin of predetermined hardness, means actuated by the movement of said first means for moving said gate to open said channel, and means for closing said gate after only one genuine coin has passed through said channel, said gate opening means being substantially unaffected by a coin of the same size and of less hardness than a genuine coin.

7. A coin controlled mechanism having therein a channel along which a coin is passed, a branch channel along which soft slugs are moved, means adapted to be actuated by a coin of predetermined hardness and means actuated by move- 7 I automatically resetting said gate after its movement by said first means, said gate opening means being substantially unaffected by a coin of the same size and of less hardness than a genuine coin.

9. A coin controlled mechanism having having therein a channel along which a coin is passed, a gate for closing said channel for ejecting a soft slug therefrom, means actuated by the passage of a coin of predetermined hardness, means actuated by the movement of said first means for moving said gate to open said channel, and means responsive to movement of a hard coin through said channel for closing said gate after: ward, said gate opening means being substantially unafiected by a coin of the same size and of less hardness than a genuine coin.

'10. A coin controlled mechanism having therein a channelalong which a coin is passed, a gate for closing-said channel for ejecting a soft slug therefrom, means adapted for movement in response to the passage of a coin of predetermined hardness, means responsive to the movement of said first means for moving said gate to open said channel, meansfor ejecting a slug of magnetic material from said channel, and means responsive to the ejection of a magnetic slug for closing said gate after, it has been opened by a magnetic slug of predetermined hardness.

11. A coin controlled mechanism having theresaid channel, means for ejecting a slug of magnetic material from said channel, and means for automatically closing said gate in response to either a hard coin of non-magnetic material through said channel or a hard slug of magnetic material as it is ejected.

12. A coin controlled mechanism having therein a channel along which a coin is passed. a gate for closing said channel for ejecting a soft slug therefrom, means adjacent the entrance of coins into said channel which'is adapted to move in response to the passage of a coin of predetermined hardness and means responsive to the movement of said first means for moving said gate to open said channel, said gate being shaped to allow the passage of only one coin past it through said channel.

13. A coin controlled mechanism having therein a channel along which a coin is passed, a

a slug of magnetic material from said channel, both of said last-mentioned means being located between the branch channel for soft slugs and the coin entrance to said main or first-mentioned channel.

14. In a coin controlled mechanism, a channel along which a coin moves to actuate said mechanism, means for closing said channel to a coin of less than predetermined weight while allowing a coin of at least such weight to pass through said channel, a signal responsive to at least partial movement of said means for indicating the presence of a light weight coin in said channel and means for ejecting a slug of magnetic material from said channel, said last-mentioned means being responsive to movement of the firstmentioned means.

l5. In a coin controlled mechanism, a channel along which a coin moves to actuate said mechanism, a branch channel ,along which a slug of magnetic material is moved, magnetic means having a plurality of pole pieces of different flux densities acting on a slug of magnetic material at, substantially the same time, located adjacent the junction of said branch channel with the main or first-mentioned channel, said pole pieces being of such shape as to be capable of withdrawing a slug of magnetic material from said main channel without holding the same and i with slight rotation of the slug about an axis posed to cooperate with a face of a magnetic sing to eject such a slug without stopping the same, a weak pole piece cooperating with a magnetic slug first and a stronger pole piece cooperating with the slug later, said pole pieces acting at substantially the same time on a slug of magnetic material. I

1'7. In a coin controlled mechanism a channel along which a coin moves to actuate said mechanism, a branch channel through which a slug of magnetic material is adapted to be ejected and magnetic means having pole pieces adjacent the junction of said branch channel with the main or first-mentioned channel, said pole pieces being of unequaled strength'and angulariy disposed to cooperate with a flat side of a magnetic slug to eject such a magnetic slug without stopping the same, a weak pole piece cooperating with a magnetic slug first and a stronger pole piece cooperating with the slug later, the adjacent edges of said poie pieces being disposed at an angle to the axis of each channel and said pole pieces acting at substantially the same time on a slug of magnetic material.

amass? ROY M. HALL.

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