EP0043262B1

EP0043262B1 - Apparatus for bottom feeding articles from a stack

Info

Publication number: EP0043262B1
Application number: EP19810302913
Authority: EP
Inventors: Nicholas Danchak, Jr.
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1980-06-27
Filing date: 1981-06-26
Publication date: 1985-01-23
Also published as: DE3168460D1; CA1156274A; EP0043262A1; JPS5727843A

Description

The invention relates to apparatus for bottom feeding articles, such as sheets of paper, envelopes or magazines, from a stack of unseparated such articles, as specified in the first portion of claim 1. Specifically, the invention is concerned with a normal force applicator for such apparatus which ensures a reliable feed to an article separator of the apparatus. The article separator may be, for example, a conventional friction retard device using a friction retard pad. The individual article thus separated is fed to the next processing station.
There are numerous applications in which a bottom feeder to feed articles serially from an unseparated stack of articles can be used, for example, to feed sheets of paper serially to a printer or copier, or to feed envelopes to a printer or labeler. Obviously, many more examples could be given. One aspect common to all bottom feeders is the difficulty experienced in reliably driving and feeding but one article from the set of stacked articles. The reliability of bottom feeders can be affected by variations in the height of the stack of articles. For example, where only a few lightweight articles, such as sheets of thin paper, are in the stack, there may not be enough weight, that is, normal force, on the stack to make the feeder work properly. To alleviate such problems, a normal force applicator can be used.
Conventional normal force applicators are designed to press down on the top of the stack of articles to hold the stack down and to provide sufficient engagement force between the bottommost article of the stack of articles and the bottom feeder. The normal force applicators can be a weighted or spring-loaded plate, bail bar or the like. One problem with such normal force applicators is that they must be removed or lifted out of the way before more articles can be added to the top of the stack. Also, where the stack is relatively large, a larger force may be required where the force is applied through the entire stack to ensure proper feeder operation.
US-A-3 838 851 (Kolibas) discloses a bottom sheet feeder using as a normal force applicator a heavy spring-biased large-diameter idler roller resting on the top of a stack of sheets to be fed. The upright face of a support for a retard member holds most of the stack in place, permitting the bottom few sheets to become shingled and then fed seriatim through the gap between the retard member and a cylindrical feed roller or a feed belt, respectively. Bearing as it does on the top sheet of the stack, the Kolibas device inevitably removes the downward bias every time fresh sheets are added to the stack, thus interfering with the smooth feeding of sheets from the stack.
The present invention aims at overcoming this problem by the features specified in the characterising portion of claim 1. Thus, the normal force applicator roller is caused to bear on only the lowermost few sheets of the stack, so that sheet-feeding is not affected by the addition of sheets to, or extraction of sheets from, that part of the stack which extends above the region of contact between the stack and the normal force applicator roller.
One way of carrying out the invention is described in detail below with reference to drawings, which illustrate only one specific embodiment, in which:

Figure 1 is an end view looking into the normal force applicator from the direction of article input.
Figure 2 is a side-sectional view of the normal force applicator of this invention taken along lines 2-2 of Figure 1 and in addition shows a typical friction retard separator.
Figure 3 is a partial side-sectional view of the normal force applicator of this invention, which shows how the normal force applicator interacts with the stack of articles to be fed, the feed belt and the friction retard assembly.
Figure 4 is a top view of the frame for the normal force applicator of this invention.
Figure 5 is a top view of the friction retard pad support frame for use with the present invention.

Referring now to the Figures, an input tray 1 is provided on which a stack of articles 3 (see Figure 3) is provided. The stack of articles 3 may be, for example, a stack of paper or envelopes or any suitable article that it is desired to feed serially to a work station. Protruding through a slot 9 in the input tray 1 in feeding relationship to the stack of articles 3 is driven feed belt 5. Driven feed belt 5 is driven in the direction shown by the arrows (see Figures 2 and 3) by driven feed belt pulleys 7. The means for driving driven feed belt pulleys 7 is not shown although obviously one of the driven feed belt pulleys 7 could be, for example, mounted on the shaft of a motor; or, as another example, the driven feed belt 5 could be driven by frictional contact with a third pulley, and pulleys 7 would not be driven.
The normal force applicator generally designated as 11 includes a roller support frame 13, which is connected by bolts 15 to base 17. Roller support frame 13 has formed therein slot 19 (see Figure 4) and aperture 21, both of which traverse the complete height of roller support frame 13 as shown in Figure 2. Slot 19 acts as a guide for normal force applicator roller support 23, which is mounted for slidable movement in the space defined by slot 19 and base 17 when it is attached to base 17. Normal force applicator roller support 23 has formed thereon roller support arms 25 (see Figure 1) between which normal force applicator roller 27 is mounted for rotation. Normal force applicator roller support 23 is urged downwardly against driven feed belt 5 by normal force applicator spring 29 to form a rolling nip 28 therewith. Normal force applicator spring 29 in this instance is attached to pin 31 in slot 33 on normal force applicator roller support 23 and to pin 35 in slot 37 on roller support frame 13. Also attached to base 17 is separator generally designated as 16, which in this instance comprises friction retard pad support frame 39 (see Figure 5). Friction retard pad support frame 39 has a depression or slot 41 and an aperture 43 formed therein. Friction retard pad support frame 39 is bolted by bolt means (not shown) to base 17. Friction retard pad support 45 is mounted for sliding motion in the space formed by slot 41 when it is attached to base 17. Attached to the bottom of friction retard pad support 45 is friction retard pad 47. Friction retard pad 47 is urged downward into contact with driven feed belt 5 by friction retard pad spring 49, which is held in aperture 43 of friction retard pad support 39 by shoulder 51.
In operation a stack of articles 3 is placed in input tray 1. Article guide means 53 (see Figure 3) is positioned such that none of the articles can rest above a centerline 55 of the normal force applicator roller drawn parallel to the direction of feed of the articles. This encourages the articles to be drawn into the rolling nip 28 formed between normal force applicator roller 27 and driven feed belt 5. When it is desired to feed an article, the driven feed belt 5 is driven by means (not shown) in the direction of travel of the fed articles as shown by arrow 59 (see Figure 3). The movement of driven feed belt 5 in the direction shown by the arrow 57 (see Figure 3) causes normal force applicator roller 27 to turn in the direction shown by arrow 61 (see Figure 3). Normal force applicator spring 29 urges normal force applicator roller 27 downward against the top of the articles present (usually two or three) in the rolling nip 28 formed by normal force applicator roller 27 and driven feed belt 5. The normal force applicator spring 29 is adjusted so that it will allow a few articles to be brought into nip 28 under the influence of a moving feed belt 5. The coefficient of friction between driven belt 5 and the bottom article of the stack of articles 3 and the rolling motion of normal force applicator roller 27 causes two or more articles from the stack of articles 3 to be drawn into the rolling nip 28 formed between normal force applicator roller 27 and driven feed belt 5. Since normal force applicator roller 27 is pressed against only a few of the bottom articles in the stack of articles 3, very little force is required to ensure feed of an article, even an article whose leading edge may not lie flat. Similarly, since normal force applicator roller 27 applies a force to only a few of the bottom articles in a stack of articles 3, the top of the stack of articles 3 is unencumbered allowing the addition of more articles to the stack of articles 3 even while the feeder is operating. The articles in the stack of articles 3, which are moved into the rolling nip 28 formed between normal force applicator roller 27 and driven feed belt 5 by the movement of driven feed belt 5, are then brought into contact with friction retard pad 47. The coefficient of friction between driven feed belt 5 and the bottom article of the stack of articles 3 is chosen to be higher than the coefficient of friction between friction retard pad 47 and the same article so that the article can be moved between the friction retard pad 47 and driven feed belt 5 when driven feed belt 5 is operating. The friction retard pad 47 applies sufficient force to block the feed of the article next above the bottom article causing the friction retard pad 47 to act as an article separator.
Other types of separators may also be used with the present normal force applicator concept. It has been found that the present normal force applicator will operate reliably feeding ordinary sheets of paper or envelopes with no adjustments being required. Also, typically only 100 to 150 grams of force are required for a normal force applicator roller measuring about 1/4 inch in diameter and about 3/8 inch in length.

Claims

1. Apparatus for feeding articles from the bottom of a stack of articles, comprising an input tray (1) for supporting a stack of articles (3) and having in it a slot (9) through which projects a driven feed belt (5) so as to be in contact with the bottom article; a separator (16) positioned downstream of the contact region between the feed belt (5) and the stack, and spaced from the feed belt (5) so as to allow the passage of only one article at a time between the feed belt (5) and the separator (16), and a normal force applicator roller (27), biased towards the feed belt (5) and spaced therefrom to form a nip big enough to grip more than one article at a time, characterised by

the normal force applicator roller (27) being spaced from the separator (16) longitudinally and upstream of the feed belt (5), and

means (53) for guiding only a few of the lowermost articles in the stack (3) to the nip whereby the roller (27) bears on only the shingled edges or upper surfaces of the respective lowermost articles.

2. Apparatus according to claim 1, wherein the guiding means (53) is positioned to direct articles (3) against the periphery of said normal force applicator roller (27) at a point below a centerline (55) of said roller (27) drawn parallel to the direction of feed of an article.

3. Apparatus according to claim 1 or 2, wherein the normal force applicator roller (27) is biased toward said driven feed belt (5) by a spring (29).

4. Apparatus according to any preceding claim, wherein said separator (16) comprises a friction retard pad (47) biased towards the feed belt (5) sufficiently to allow the passage of only one article at a time between the friction retard pad (47) and the feed belt (5).