US3337125A

US3337125A - Coin escrow device

Info

Publication number: US3337125A
Application number: US522190A
Authority: US
Inventors: Helmer B Nielsen
Original assignee: Eddy Match Co Ltd
Current assignee: Eddy Match Co Ltd
Priority date: 1965-12-30
Filing date: 1966-01-21
Publication date: 1967-08-22
Anticipated expiration: 1984-08-22
Also published as: DE1474832A1; GB1110988A

Description

Aug. 22, 1967 H. B. NIELSEN COIN ESCROW DEVICE 2 Sheets-Sheet 1 Filed Jan. 21, 1966 VENTOR ATENI' A 2, 1967 H. B. NIELSEN 3,337,125

com ESCROW DEVICE I 2 Sheets-Sheet Filed Jan. 21. 1966 United States Patent Claims. 61. 232-575 This invention relates to a coin escrow device, and more particularly, to a mechanism for delaying and controlling the travel of coins in a vending machine.

In coin controlled vending machines, such as pay telephones or any equipment adapted to render services or dispense goods in response to the insertion of coins or tokens, it is frequently desirable to retain the coins or tokens at a certain location for a time and to then direct the coins along one of two paths. For example, in a vending machine equipped with a sorting device, which directs authentic coins separated into their denominations into a coin totalizer, it is desirable to collect the coins passing through the totalizer and to hold them in escrow before letting them fall into ,a coin collection box of the vending machine. With this arrangement, the collected coins are permitted to fall along one path into the coin collecting box during the vending cycle of the machine or at least on the completing of the vending cycle, but if the totalizer detects that the wrong amount of coinage has been inserted, for example, the coinage can be directed to another path into a coin return chute.

For the sake of economics, it is preferable, of course, to use a compact, efiicient device of simple construction to carry out the above-described escrow function, and it is the purpose of this invention to provide such a device.

According to the present invention, there is provided an open top hopper which includes a pair of opposed side walls with a tiltable, normally horizontal bottom plate therebetween. The bottom plate has a pair of opposite side edges juxtaposed one each on the side Walls and there is provided a first pair of aligned stub projections extending transversely from the opposite side edges of the bottom plate to form one axis of pivot of the bottom plate and a second pair of aligned stub projections parallel to and horizontally spaced from said first pair of stub projections, the second pair also extending transversely from the opposite side edges of the bottom plate to form another axis of pivot of the bottom plate. Each side wall is provided with a pair of supporting ledges extending from spaced inner ends horizontally in opposite directions along the wall, the supporting ledges of each side wall normally carrying one each of the stub projections on the juxtaposed side edge of the bottom plate. Means are also provided for horizontally shifting the bottom plate in either direction a distance suflicient to permit one of the pairs of the stub projections to slide off the inner end of the supporting ledges and thereby allow the bottom plate to pivot downwardly about the axis of pivot provided by the other pair of stub projections on the supporting ledges.

More specifically, the present invention provides for means arranged to bias the bottom plate to its normal horizontal position.

In a preferred embodiment of the present invention, the bottom plate has an additional projection extending from one of the side edges between and parallel to the pairs of stub projections, and the means for shifting the bottom plate comprises a normally vertical arm connected to one of the side walls for pivoting about an axis parallel to and spaced from the additional projection, the arm having an inverted V-shaped opening normally 3,337,125 Patented Aug. 22, 1967 receiving the additional projection at the apex thereof, and solenoid means connected to the arms and arranged to pivot the arm back and forth in either direction from the vertical.

In the accompanying drawings, which show one embodiment of the present invention, by way of example:

FIGURE 1 is a front elevational view of the escrow device;

FIGURE 2 is a back elevational view of the same device shown in FIGURE 1;

FIGURE 3 is an end view as seen from the right hand end of FIGURE 1;

FIGURE 4 is a view similar to FIGURE 1 but showing the bottom plate in two different coin dispensing positions, one in full lines and the other in chain dotted lines; and

FIGURE 5 is a perspective view of the bottom plate.

In FIGURES 1 to 3, the reference numeral 10 denotes generally the coin escrow device of the present invention. The device 10 includes front and back vertical side walls 11, 11, which are spaced and parallel and a pair of slanted walls 12, 12 which converge downwardly between walls 11, 11. Side walls 11, 11 and slanted walls 12, 12 form an open top hopper, the bottom of which is normally closed by a bottom plate 13. The bottom plate 13 is movable, however, to tilt in two different directions when shifted by an actuating means 14 as will be described in more detail below.

As may be seen in the drawings, the front and back side walls 11, 11 which are rectangular plates, are much bigger than slanted walls, 12, 12 so that they extend well below bottom plate 13. The slanted walls 12, 12 which converge downwardly are rectangular plates and have sides edges abutting inside surfaces 16, 16 of side walls 11, 11. Side walls 11,11 are held tightly against slanted Walls 12, 12 by screws 17 which pass through walls 11, 11 and are threaded into posts 18. The side edges of slanted walls 12, 12 each have a pair of square projecting lugs 19 which are received in matching openings 20 in walls 11, 11 so that the four walls forming the hopper are locked together. The lower edges of side Walls 12, 12 are horizontally spaced to form the bottom opening of the hopper.

The bottom plate 13 is also rectangular in shape having a pair of opposite parallel side edges 22, 22, juxtaposed one each of the inside surfaces 16, 16 of side walls 11, 11. Adjacent one end edge of bottom plate 13 there is provided a first pair of aligned cylindrical shaped stub projections 23, 23 extending transversely from the opposite side edges 22, 22 of the bottom plate 13 to form one axis of pivot for the bottom plate (FIGURE 5). At the other end edge of the bottom plate 13 there is provided a second pair of aligned stub projections 24, 24 extending transversely from the opposite side edges 22, 22 to form another axis of pivot parallel to the first formed by projections 23, 23. The projections 23, 23 and 24, 24 are preferably no greater in length than the thickness of each of the side walls 11, 11. Midway between projections 23, 23 and 24, 24, i.e., on the transverse centre-line of the. bottom plate 13, an additional pair of aligned stub projections 25, 25 are provided extending transversely from side edges 22, 22 and parallel to the axes provided by the other two pairs of stub projections. The stub projections 25, 25 are longer than the other stub projections as is most readily apparent in FIGURES 3 and 5.

Identical patterns 27, 27 are formed in each of front and back side walls 11, 11. Each pattern 27, which is symmetrical about its vertical centre-line receives the stub projections 23, 24, 25 on one side edge 22 of the bottom plate 13 with each projection 25 extending to the outside of the side wall 11 because of its greater length. Each pattern 27 includes a pair of short horizontal slots 28, 28 extending outwardly from spaced inner ends 29, 29 to outer ends 30, 30. The slots 28, 28 of each pair are thus spaced to form supporting ledges for the stub projections 23 and 24 of each side edge 22 of the bottom plate 13 under the lower edges of the walls 12, 12. The stub projections 23 and 24 are normally received and rest in the horizontal slots 28, 28 between the inner end 29 and outer end 30 of the slots as shown in full lines in FIGURES 1 and 2. For reasons which will become apparent later, the distance between the inner end 29 of each slot 28 and the outer end 29 of the other slot 28 in the same pair is equal to the distance between the stub projections 23 and 24. A downwardly extending arcuate slot 31 communicates with the inner end 29 of each horizontal slot 28, each arcuate slot 31 being struck about the outer end 30 of the other horizontal slot 28 in the same pattern on a radius equal to the distance between stub projections 23 and 24. Midway between each pair of horizontal slots 28, 28 and on the same horizontal plane is another horizontal slot 32 through which stub projection extends. Each end of slot 32 is spaced from the outer end of the adjacent slot 28 a distance equal to the distance between stub projection 25 and either of stub projection 23 or 24. A downwardly extending slot 32 communicates with each end of slot 32, each slot 33 being struck about the outer end of the adjacent slot 28 in the same pattern on a radius equal to one-half the distance between stub projections 23 and 24.

At the back of the device 10, the stub projection 25 is slidably received in an elongated ring 35 as may be observed in FIGURES 2 and 3. The elongated ring which is parallel to the wall 11 and elongated in the vertical direction is suspended between two coil springs 36 and 37 under tension. The spring 36 is connected at its lower end to the upper end of elongated ring 35 and at its upper end to the back side wall 11 by a pin 38 while the spring 37 is connected at its upper end to the lower end of elongated ring 35 and at its lower end to the back side wall 11 by bottom screw 17. The screw 17 and pin 38 are on the vertical centre-line of the pattern 27 so that the elongated ring 35 biases stub projection 25, and therefore, bottom plate 13 to a central position.

The actuating means 14 which is attached to the front side wall 11 includes a normally vertical arm 40 and two electrical solenoids 41 and 42 fixed to front side wall 11. The arm 40 is pivotally connected to front side wall 11 by a horizontal pin 43 which extends perpendicular to front side wall 11 above and on the centre-line of pattern 27. At the lower end of the main part of arm 40 there is formed two diverging legs 44, 44' forming an inverted V-shaped opening or recess defined by camming surfaces 45, 45. The camming surfaces 45, 45 straddle the stud projection 25 at the front of device 10, and where arm 40 is in its normal vertically depending position, the stud projection 25 is situated in the apex of inverted V-shaped formation.

The top of the arm is bent over to form a horizontal portion 46 and then down to form a short depending portion 47 out in front of and parallel to the main part of the arm. The short depending portion 47 terminates in two downwardly and inwardly arcuate lugs 48, 48. The lugs 48, 48 each extend between a bifurcated portion 49 formed in the outer end of armature 50 of one of the solenoids 41 and 42. Each bifurcated outer end portion 49 of the armatures has a transverse pin 51 holding the arcuate lug 48 therein. Each of the solenoids is adapted to be wired into the circuitry of the vending machine in which the device 10 is to be installed, so that either before, during or after the vending cycle, one or the other of the solenoids 40, 41 is energized, and each solenoid is of the type in which the armature 50 is retracted upon energization.

A coil spring 52 has one end connected to stub projection 25, and its other end connected to the pin 43 above the stub projection 25. The spring 52 is under tension so that an upward biasing force is applied to bottom plate 13.

In operation, the coin escrow device 10 is located in the coin operating mechanism of a vending machine. For example, the device 10 may be located immediately below a coin totalizer (not shown), so that after a custorners coinage has been totalized it falls into device 10 and is collected therein. The coins thus collected rest on bottom plate 13 until one or the other of the solenoids 41 and 42 is momentarily energized by an electrical signal established in the circuitry of the vending machine. On energization of one of the solenoids 41 and 42, the bottom plate 13 is tilted in one of two directions, as will be described below, so the coins resting in the device are dumped in one of two chutes (not shown). One of the chutes which leads to the coin collection box has its mouth opening under one side of the device 10, say, for example, in the space under the device 10 to the right of the bottom screw 17 as viewed in FIGURE 4, and the other chute which leads to a coin return receptacle has its mouth opening under the other side, say, for example, under the bottom of device 10 to the left of the bottom screw 17 as viewed in FIGURE 4.

If a customer inserts the proper coins into the vending machine, the coins pass through the totalizer and rest on bottom plate 13 in the escrow device 10 of the present invention, and the totalizer signals the vending machine to vend. This same signal may be utilized, for example, to momentarily energize solenoid 41. When solenoid 41 is energized its armature 50 is retracted to pull arm 40 through an arc to the left as indicated by arrow 55. As this takes place the camming surface 45 of leg 44 at the outer end of the arm 40 pushes on the stub projection 25 at the front side edge of bottom plate 13 to thereby shift the bottom plate horizontally to the left as viewed in FIG- URE 4. The bottom plate 13 shifts to the right until stub projections 23, 23, reach the outer ends 30, 30 of their slots 28, 28 at which time stub projections 24, 24 and 25, 25, are over arcuate slots 31, 31 and 33, 33 com-municating with their slots 28, 28 and 32, 32, respectively. Accordingly, with further movement of arm 40 in the direction of arrow 55, stub projection 25 is cammed downwardly in arcuate slot 33 by the camming surface 45 of leg 44 as the bottom plate pivots downwardly about the axis provided by stub projections 23, 23 at the outer ends 30, 30 of their slots 28, 28 in the front and back side walls 11, 11. As bottom plate 13 pivots stub projections 24, 24 move downwardly in arcuate slots 31, 31 in the front and back side walls 11, 11. The solenoid is arranged to pull the arm 40 until it reaches the position shown in FIGURE 4 at which time the bottom plate 13 is tilted as shown to permit the coins resting thereon to slide off into the chute leading to the coin box.

As indicated above, the solenoid is only energized rnomentarily so that the arm 40 is soon permitted to return to its normally vertical position. As the arm returns, the bottom plate 13 is biased back to its normal horizontal and central position by spring 53 and also springs 36 and 37 acting on stub projections 25, 25. To return the bottom plate to its horizontal position, i.e., to pivot it up about stub projections 23, 23, spring 53 contributes most of the force as it pulls up on stub projection 25 at the front, although springs 36 and 37 contribute considerable force on the stub projection 25 at the back. When the bottom plate 13 reaches the horizontal position, it is shifted back to the central position by the force exerted by springs 36 and 37 as elongated ring 35 is always biased to the centreline of the pattern 27.

When the coinage collected in the escrow device 10 is not acceptable for some reason such as the wrong coins have been inserted, solenoid 42 is energized by some means such as a return button on the outside of the machine, and arm 40 is swung in the direction of arrow 56 to the position shown in chain dotted lines in FIGURE 5.

As this takes place, the bottom plate 13 is pivoted downwardly exactly as described above, but in the opposite direction about the axis provided by stub projections 24, 24 to the positon shown by chain dotted lines. Thus, the coins resting on bottom plate 13 slide off and into the other chute leading to the coin return receptacle.

Although the pattern 27 of slots shown is preferable, it is psosible to use a less intricate design. For example, all of the material shown between slots 31 and 32 in each pattern could be omitted as slots 33, 33 are not absolutely necessary. The important slots in the pattern 27 are 28, 28 in each of side Walls 11, 11 as it is these slots which receive stub projections 23 and 24. The bottom edges of slots 28, 28 thereby define supporting ledges on which the stub projections rest to hold the bottom plate 13 in its horizontal position, and as described above, an essential feature of these supporting ledges is that they are properly spaced to permit one of the pairs of stub projections 23, 23 and 24, 24 to slide oif the inner end of the supporting ledges to thereby allow the bottom plate to pivot downwardly about the axis of pivot provided by the other pair still resting on the other supporting ledges.

It is also believed apparent that instead of slotting the front and back side walls 11, 11 with the pattern 27 the inside surfaces 16, 16 could be embossed to provide necessary ledges and ridges for supporting and guiding the stub projections 23, 23 and 24, 24.

These and other modifications obvious to those skilled in the art can be made to the disclosed embodiment of the present invention without departing from the spirit of the invention as defined in the appended claims.

I claim:

1. A coin escrow device for a vending machine, said device comprising a first pair of vertical, spaced, parallel Walls and a second pair of spaced walls extending perpendicularly between said first pair and defining an open top, coin receiving hopper therewith, a normally horizontal bottom plate extending beneath said second pair of walls and having opposite side edges one each juxtaposed said first pair of walls for closing the bottom of said hopper, a first pair of aligned stub projections extending transversely from the opposite side edges of said bottom plate and forming one axis of pivot for said bottom plate, a second pair of aligned stub projections parallel to and horizontally spaced from said first pair of stub projections and also extending transversely from the opposite side edges of the bottom plate to form another axis of pivot for said bottom plate, an additional projection extending from one side edge of said bottom plate between and parallel to said pairs of stub projections, each wall of said first pair having a pair of horizontally spaced slots formed therein on a common horizontal plane with each pair of slots in each wall receiving one each of the stub projections of the first and second pair of stub projections on a common edge of the bottom plate for thereby supporting said bottom plate in the horizontal position, each of the Walls of said first pair having an opening below and communicating with inner ends of said slots, a normally vertical arm connected to one of said side walls for pivoting about an axis parallel to and spaced from said additional projection, said arm having an inverted V-shaped opening normally receiving said additional projection at the apex thereof, and solenoid means connected to said arm and arranged .to pivot said arm back and forth in either direction from the vertical for shifting said bottom plate in either direction a distance su'fiicient to permit one of the pairs of stub projections to slide out of the slots and down into the openings and thereby allow the bottom plate to pivot downwardly about the axis of pivot provided by the other pair of stub projections in the slots.

2. A coin escrow device for a vending machine, said device comprising a first pair of vertical, spaced, parallel walls and a second pair of spaced walls extending perpendicularly between said first pair and defining an open top, coin receiving hopper therewith, a normally horizontal bottom plate extending beneath said second pair of walls and having opposite side edges one each juxtaposed said first pair of walls for closing the bottom of said hopper, a first pair of aligned stub projections extending transversely from the opposite side edges of said bottom plate and forming one axis of pivot for said bottom plate, a second pair of aligned stub projections parallel to and horizon tally spaced from said first pair of stub projections and also extending transversely from the opposite side edges of the bottom plate to form another axis of pivot for said bottom plate, each wall of said first pair having a pair of horizontally spaced slots formed therin on a com. mon horizontal plane with each pair of slots in each wall receiving one each of the stub projections of the first and second pair of stub projections on a common edge of the bottom plate for thereby supporting said bottom plate in the horizontal position, each wall of said first pair having an opening therein between said spaced slots, a third pair of aligned stub projections extending transversely from said opposite side edges of said bottom plate between and parallel to said first and second pairs of stub projections, each stub projection in said third pair having a portion projecting through said opening between said spaced slots, each of the walls of said first pair having an opening below and communicating with inner ends of said slots, a normally vertical arm pivotally connected to one wall of said first pair above the portion of one of the stub projections of said third pair, said arm having a pair of diverging legs at the bottom thereof providing camming surfaces in inverted V-shaped formation straddling said portion, and solenoid means for selectively swinging said arm from the vertical in either direction parallel to said first pair of walls and thereby cause said camming surfaces to cam said one stub projection of said third pair for shifting said bottom plate in either direction sufficient to permit one of the pairs of stub projections to slide out of the slots and down into the openings communicating with the slots and thereby allow the bottom plate to pivot downwardly about the axis of pivot provided by the other pair of stub projections in the slot.

3. An escrow device as defined in claim 2, wherein spring means is attached tothe other wall of said first pair and engages the portion of the other stub projection of said third pair for biasing said bottom plate to a centralized closed position.

4. A coin escrow device for holding coins in a vending machine and subsequently directing the coins to one of two different paths, said device comprising an open top, coin receiving hopper defined by two pairs of walls, one pair of walls being vertical, spaced, parallel plate-like members and the other pair extending between the parallel walls and converging downwardly to spaced lower edges defining a bottom opening of the hopper therebetween, with the parallel walls having lower portions protruding below the lower edges of the converging walls, a normally horizontal, rectangular bottom plate having a first pair of opposite edges each juxtaposed one of the parallel walls and a second pair of opposite edges normally immediately below the lower edges of the converging walls for closing the bottom opening, said bottom plate having two pairs of stub projections one each adjacent and parallel to said second pair of edges for providing two pivot axes for said bottom plate, the stub projections in each pair being aligned and extending transversely from said first pair of edges and into a slot pattern formed in the lower portion of each of the parallel walls, the slot pattern in each of the parallel walls including a first pair of spaced horizontal slots under the lower edges of the converging walls, said slots being on the same horizontal plane and normally carrying between inner and outer ends thereof one each of said stub projections to thereby hold said plate in a central position for closing said bottom, and a pair of converging arcuate slots extending downwardly one each from the 7 horizontal slots, each arcuate slot communicating with the horizontal slot adjacent the inner end of the horizontal slot and being struck about the outer end of the other horizontal slot on a radius equal to the spacing between the two pairs of stub projections, and actuating means for shifting said bottom plate selectively in either direction parallel to the parallel walls for sliding one pair of stub projections to the outer ends of the horizontal slots and thereby permit the other pair of stub projections to slide downwardly into the arcuate slots as the bottom plate pivots downwardly about said one pair of stub projections.

5. An escrow device as defined in claim 4, wherein said bottom plate has a third pair of aligned stud projections midway between and parallel to the other two pairs; wherein each slot pattern includes an additional horizontal slot spaced midway between said pair of horizontal slots, and an additional pair of arcuate slots communicating with and diverging downwardly from opposite outer ends of said additional horizontal slot, each additional arcuate slot being struck about the outer end of the adjacent horizontal slot on a radius equal to one-half the distance between the said two pairs of stub projections, the additional horizontal slots in the two slot patterns normally receiving the third pair of stub projections with a portion of the third pair of stub projections protruding outwardly of said parallel walls; and wherein the actuating means comprises a solenoid actuated member arranged to engage and force one of the protruding portions of the stub projections along the additional horizontal slot and down either one of said additional arcuate slots.

6. An escrow device as defined in claim 5, wherein said solenoid actuated member comprises an arm connected to the outside of one of said parallel walls above the additional horizontal slot, said arm having a pair of diverging legs at the lower end thereof defining a pair of camming surfaces in an inverted V-shaped formation, said one protruding portions of the stub projections being arranged to be cammed from a normal position at the apex of the formation sideways in the additional horizontal slot and then downwardly in one of the additional arcuate slots as the arm is swung -from a normal vertical position.

7. An escrow device as defined in claim 6, and further comprising a pair of solenoids connected to said hopper, one on either side of said arm, each solenoid being connected to said arm and being arranged to pull said arm on energization thereof.

8. An escrow device as defined in claim 6, and further comprising a coil spring member connected under tension at a lower end to said one protruding portion of the stub projection and at an upper end to the wall to thereby bias said bottom plate upwardly.

9. An escrow device as defined in claim 5, and further comprising a spring means engaging the other protruding portion of the stub projections for biasing said bottom plate to the central position.

10. An escrow device as defined in claim 9, wherein said spring means comprises a ring member elongated in the vertical direction and slidably receiving said other protruding portion, and upper and lower springs, said upper spring being connected under tension at a lower end to the upper end of the elongated ring and at an upper end to the hopper above the additional horizontal slot, said lower spring being connected under tension at an upper end to the lower end of the elongated ring and the lower end to the hopper below the additional horizontal slot.

References Cited UNITED STATES PATENTS 262,267 8/ 1882 Alexander et a1 232-59 969,597 9/ 1910 Bucknam et al. 232-58 1,932,234 10/1933 Sengebusch 232-575 2,166,639 7/1939 Peek 232-595 2,665,791 l/1954 Caruso 232-575 FOREIGN PATENTS 620,677 10/ 1935 Germany.

FRANCIS K. ZUGEL, Primary Examiner.

DAVID J. WILLIAMOWSKY, Examiner.

Claims

1. A COIN ESCROW DEVICE FOR A VENDING MACHINE, SAID DEVICE COMPRISING A FIRST PAIR OF VERTICAL, SPACED, PARALLEL WALLS AND A SECOND PAIR OF SPACED WALLS EXTENDING PERPENDICULARLY BETWEEN SAID FIRST PAIR AND DEFINING AN OPEN TOP, COIN RECEIVING HOPPER THEREWITH, A NORMALLY HORIZONTAL BOTTOM PLATE EXTENDING BENEATH SAID SECOND PAIR OF WALLS AND HAVING OPPOSITE SIDE EDGES ONE EACH JUXTAPOSED SAID FIRST PAIR OF WALLS FOR CLOSING THE BOTTOM OF SAID HOPPER, A FIRST PAIR OF ALIGNED STUB PROJECTIONS EXTENDING TRANSVERSELY FROM THE OPPOSITE SIDE EDGES OF SAID BOTTOM PLATE AND FORMING ONE AXIS OF PIVOT FOR SAID BOTTOM PLATE, A SECOND PAIR OF ALIGNED STUB PROJECTIONS PARALLEL TO AND HORIZONTALLY SPACED FROM SAID FIRST PAIR OF STUB PROJECTIONS AND ALSO EXTENDING TRANSVERSELY FROM THE OPPOSITE SIDE EDGES OF THE BOTTOM PLATE TO FORM ANOTHER AXIS OF PIVOT FOR SAID BOTTOM PLATE, AND ADDITIONAL PROJECTION EXTENDING FROM ONE SIDE EDGE OF SAID BOTTOM PLATE BETWEEN AND PARALLEL TO SAID PAIR OF STUB PROJECTIONS, EACH WALL OF SAID FIRST PAIR HAVING A PAIR OF HORIZONTALLY SPACED SLOTS FORMED THEREIN ON A COMMON HORIZONTAL PLANE WITH EACH PAIR OF SLOTS IN EACH WALL RECEIVING ONE EACH OF THE STUB PROJECTIONS OF THE FIRST AND SECOND PAIR OF STUB PROJECTIONS ON A COMMON EDGE OF THE BOTTOM PLATE FOR THEREBY SUPPORTING SAID BOTTOM PLATE IN THE HORIZONTAL POSITION, EACH OF THE WALLS OF SAID FIRST PAIR HAVING AN OPENING BELOW AND COMMUNICATING WITH INNER ENDS OF SAID SLOTS, A NORMALLY VERTICAL ARM CONNECTED TO ONE OF SAID SIDE WALLS FOR PIVOTING ABOUT AN AXIS PARALLEL TO AND SPACED FROM SAID ADDITIONAL PROJECTION, SAID ARM HAVING AN INVERTED V-SHAPED OPENING NORMALLY RECEIVING SAID ADDITIONAL PROJECTION AT THE APEX THEREOF, AND SOLENOID MEANS CONNECTED TO SAID ARM AND ARRANGED TO PIVOT SAID ARM BACK AND FORTH IN EITHER DIRECTION FROM THE VERTICAL FOR SHIFTING SAID BOTTOM PLATE IN EITHER DIRECTION A DISTANCE SUFFICIENT TO PERMIT ONE OF THE PAIRS OF STUD PROJECTIONS TO SLIDE OUT OF THE SLOTS AND DOWN INTO THE OPENINGS AND THEREBY ALLOW THE BOTTOM PLATE TO PIVOT DOWNWARDLY ABOUT THE AXIS OF PIVOT PROVIDED BY THE OTHER PAIR OF STUB PROJECTIONS IN THE SLOTS.