First-in First-out Storing Device For Postal Documents

Abstract

A movable carriage adjacent the input end of a stack of postal documents having a pivoted spring-urged stacking head in contact with the stack, which head both feels and feeds the documents in the stack and operates a pair of micro switches on the carriage to move the carriage toward or away from the stack to maintain substantially the same pressure by the head on the stack regardless of the number of documents fed to or removed from the stack.

Parent Case Text

This application is a continuation-in-part of U.S. application Ser. No. 826,922, filed May 22, 1969, and now abandoned.

Description

BACKGROUND OF THE INVENTION

This invention relates to a stacking-device for temporarily storing postal documents, such as letters and the like in an intermediate stack, with a view to further automatic treatment. Conventional intermediate stacking-devices of this type possess a carriage allowing the introduction of the letters and their formation into a stack.

These stacking carriages must be movable in order to make room for the stack to be formed. The movement is controlled by means of a lever which records the place of the last letter introduced. This recording is electrically converted into a movement from or to the stack. The lever, however, must also have a normal position intermediate between the two switching positions, in order to avoid oscillating of the carriage. The resulting hysteresis is increased further by the mass of the carriage, which causes too slow a reaction in comparison with the rapid movements of the incoming letters. The slow reaction of the carriage leads to much variation in the stack pressure, which results in difficulties in the stacking and taking-off actions. If the pressure in the stack is too high the leading edges of limp letters will be creased; and if the pressure is too low cards will rebound after having reached the stop-plate, thus causing trouble at the removing end.

Because the stacking-devices have smooth bottom and side surfaces, the letters must be supported to prevent them from falling over. At the supplying end, the carriage must keep the letters upright; while at the removing end this is done by the removing device. If the length of the stack does not exceed about 20 centimeters a minimal pressure will suffice to support the stack, but if the stack has a length of more than 30 centimeters the stack pressure required to prevent the stack from falling becomes inconveniently large necessitating a different adjustment of the pressure of the feeler against the incoming letters. In such a case the feeler not only determines the place of the letter, but also the stack pressure, and this larger stack pressure impedes the correct introduction and removal of the letters.

SUMMARY OF THE INVENTION

In order to distribute the stack pressure as favorably and as evenly as possible, the stacking-device according to this invention has a stacking-head pivotally mounted on a movable carriage, which head is kept in contact with the rear of the stack by a spring. In the normal state, of no supply and no removal, the stacking-head is kept in a state of equilibrium by the spring and its carriage stands still. However when documents are introduced into the stack, the stacking-head pivots backwardly out of its state of equilibrium until it closes a first contact, which starts a transport device to move the carriage backward until the stacking-head is returned to its state of equilibrium and the contact is opened to stop the carriage. When documents are being removed at the front or other end of the stack, the stacking-head pivots forwardly out of its state of equilibrium until it closes a second contact, which starts the transport device to move the carriage forward until the stacking-head is returned to its state of equilibrium, and the second contact is opened to again stop the carriage. These operations take place in such a way that the stacking-head only swivels through a small angle, and the pressure in the stack is kept practically constant.

Accordingly, the carriage supports a very lightly hinged stacking-head instead of a feeling lever, which head always pushes with the same adjusted force against the stack, because it mainly reacts to differences of pressure arising during the stacking operations. The position of the stacking-head determines whether the carriage must move, but the front of the stacking-head does not move with the carriage, it remains stationary while the spindle or pivot for the stacking head moves with the carriage, so that during movements of the carriage the pressure on the stack remains unchanged. Thus, since the pressure of the incoming letters against the stacking-head is practically constant, They are not creased and they are all conveyed up to their stop-plate.

BRIEF DESCRIPTION OF THE VIEW

The above mentioned and other features, objects and advantages and the manner of attaining them are described more specifically below by reference to an embodiment of this invention shown in the accompanying drawing, wherein:

The FIGURE is a schematic plan view of a first-in first-out stacking device according to a preferred embodiment of this invention, with parts of its supporting table broken away.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The device is shown herein mounted on a top of a table TA along which a carriage Stw may be moved by a chain CH driven by a gear and reversible motor mechanism or transfer device TD. The letters L which enter the carriage Stw are pinched between two belts B 1 and B 2 and first move past five rollers I through V on the carriage before they reach the roller A on the pivotal axis of the mounting for the pivoted stacking-head Stk, at which roller A they approach the end of their pinching between the two belts B 1 and B 2. The belt B 1 may be directly driven by a motor M mounted on the carriage Stw, and it may drive the belt B 2 by frictional contact therewith and the letters L fed between these two belts. These letters L thus completely emerge from the pinching belts B 1 and B 2 only when their trailing edges have left the roller V.

When the leading edge of each letter L will have arrived approximately at the roller C on the pivoted stacking-head Stk, it is pulled by friction with the stacking belt S over the input end of the stack as far as the stop-plate T mounted on the stacking-head Stk, which plate T is adjacent the stack holding means H which may include a rotating worm like WT described below. The stacking belt S may be driven by a belt SS between the stacking head pivot roller A and roller B to insure that belts B 1, B 2 and S all travel at the same speed, and also to avoid the weight of having a separate drive motor on the stacking head for the belt S.

In the meantime, owing to the propulsive action of the rotating worm W, the trailing edge of each letter L is pushed toward the stack, in order to make room as rapidly as possible between the letter that has just arrived and the next letter, particularly if there is only a very small interval between these two successive letters. Similar parallel worms WT may be provided along the top of the table TA under the stack to insure movement of the stack against the letter removing device RM.

The small increase of the pressure between the stacking-head Stk and the letter L that has just arrived, which increase is due to the thickness of this letter, causes the stacking-head Stk to move away from the stack. This is possible because the stacking-head Stk swivels around the spindle of the roller A under the influence of a spring VV between the head Stk and the carriage Stw until an equilibrium is reached. A cam SN which is fixed to the stacking-head Stk, moves the lever of the microswitch SI fixed on the carriage Stw until this switch closes. This then causes the carriage Stw to be moved backwardly, such as on its wheels Wh which roll on the top of the table TA, by means of the chain CH coupled to the gear and reversible motor mechanism of the transport device TD. During this movement the stacking-head Stk, which carries the cam SN, remains in its place resting on the stack, whereas the microswitches SI and SII move along with the carriage Stw. This movement of the carriage Stw continues until the microswitch SI opens again to stop further movement of the carriage Stw.

When the stack starts moving under the action of the worms WT and a removing device RM for the letters L at the removing end, the stacking-head Stk is moved along with the withdrawing stack by the spring VV. Again the carriage Stw remains stationary until the cam SN actuates or closes the microswitch S II, which now causes the carriage Stw to move along with the stack until the microswitch S II is opened which is when the stacking-head Stk reaches the state of equilibrium again, and the carriage Stw is stopped.

While there is described above the principles of this invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of this invention, such as other types of driving means may be used for the carriage, removing device, belts, etc.

Claims

I claim:

1. A first-in first-out stacking device for postal type documents comprising:

a. means (H) for holding a stack of the documents,

b. a carriage means (Stw) adjacent the input end of the stack,

c. means (TD) for moving said carriage means toward and away from said input end of the stack,

d. stacking means (Stk) pivotally mounted on said carriage means for movement relative to said carriage means and for successively feeding documents onto the input end of the stack,

e. means (B 1, B 2) on said carriage means for successively feeding documents to said stacking means,

f. means (RM) fixed at the output end of said holding means and the stack for successively removing documents from the stack,

g. spring means (VV) between said carriage means and said stacking means for urging said stacking means against the input end document in the stack, and

h. a pair of spaced limit switch means (S I, S II) mounted on said carriage and controlled by the position of said stacking means with respect to said carriage means to operate said means for moving said carriage to maintain said carriage means within the spacing of said limit switch means at a predetermined distance from the input end of the stack.

2. A device according to claim 1 wherein said stacking means includes a stop plate (T) at the input end of the stack.

3. A device according to claim 1 wherein said means for moving said carriage means includes a reversible motor means.

4. A device according to claim 1 wherein said stacking means comprises a friction belt for moving the documents, and rollers around which said belt rotates.

5. A device according to claim 1 wherein said stacking means also includes worm means for feeding the trailing portion of a document toward the stack to be out of the way of the next succeeding document fed to said stacking means.

6. A device according to claim 1 wherein said feeding means on said carriage means comprises a pair of pinching belts between which the documents are fed and a plurality of rollers for backing up said belts.

7. A device according to claim 6 wherein said stacking means includes a pivot coaxial with one of said rollers.

8. A device according to claim 1 wherein said pair of limit switch means include a cam means mounted on said stacking means.