The present invention relates to a device for cyclically rearranging a

* stack of substantially rectangular sheets, e.g. photographic prints. Such devices are disclosed in in the documents WO 89/04991 and WO 89/09947 and

^* DE-A-41 18 390. The present invention is an improvement of these known devices which shall be referred to as "photo changer". With respect to certain details, the document WO 87/03106 will be referred to, too.

The known photo changers comprise a housing and a slider, the latter being reciprocable between an inner end position within the housing and an outer end position. Upon slider withdrawal, an individual print of a stack of photo prints is retained in the housing by retaining means and drawn free of the remaining prints which are transported out of the hou¬ sing by a stack transporter provided on the slider whereby the retained individual print is overrun by the remaining stack and its transporter. With the slider in its outermost position, the individual print in the housing is completely overrun by the stack and the transporter so that its transverse end edge adjacent the stack transporter is released. A transfer system displaces now the individual print in the housing to the other end of the stack, and when the slider is pushed in, the individual sheet will be placed on the other stack end. While the individual print passes through a return gap between the stack transporter and the housing its second transverse end edge finds support on print stops in the hou¬ sing.

The known photo changers operate satisfactorily in most cases. However, sometimes it has been observed that a withdrawn individual print in the housing is crunched upon the slider's being pushed inwards thereby bloc¬ king further slider movement with the result that the changer with its contents was damaged.

It is an object of the present invention to improve the known photo chan-

* gers such that such a fatal event is prohibited.

According to the invention, catching means are provided to assure that the inner transverse edge of the individual print is aligned with the stops. "Alignment" means in this context the position of the inner trans¬ verse edge in direction of the slider movement; whether or not the trans¬ verse edge really engages the stops will depend upon the conditions to which the other, outer transverse edge is subjected.

In fact, it has been found that the fatal event described above is due to fact that the outer transverse edge of the individual sheet — that is the edge which is last overrun by the stack transporter ~ had not been released either because the user pushed the slider home from an interme¬ diate position instead from the outer end position, or because the trans¬ porter had "lost" a second print upon withdrawal, said second print lay¬ ing across the outer transverse edge of the individual sheet to be ex¬ changed thereby prohibiting the proper function of the transfer system. The stack transporter then tends to push inwards the one or two prints held clamped by the transporter so that at least the to-be-exchanged print is placed with its inner transverse edge beyond the stops. A print so positioned cannot reach again the proper stack end and is crunched. If, however, the inner transverse edge of that print has been transferred a sufficient amount to confront the stops the print will also be crunched: A print which is held clamped between the stack transporter and the housing adjacent the outer transverse print edge must neither engage the stops nor become displaced beneath the stops. It will be recognized that under the conditions of such a malfunction a print exchange is impossible; instead, the individual sheet must be added to the stack end again from which it had just been withdrawn. The catch means according to the invention assure that the "released" transverse edge of the individual print remains in alignment with the stops and that therefore the rearrangement cycle may be restarted upon the next slider reciprocation.

Embodiments of the present invention are illustrated in the attached drawings and will be explained in detail hereunder. Therein, the very operation of the photo changer will be only briefly recapitulated; for further details, the documents cited above are referred to, the disclo-

sure thereof being included herein by reference.

Fig. 1 illustrates a photo changer according to the invention in a section view parallel to the planes defined by the prints to be re¬ arranged, the photo changer, however, being shown without prints,

Fig. 2 through 5 illustrate the changer of Fig. 1 in successive phases of operation in a section view of line A-A of Fig. 1,

Fig. 6 through 9 illustrate in analog form the normal function of a photo changer of a second embodiment of the invention,

Fig. 10 through 12 illustrate the malfunction due to false handling or double print removal,

Fig. 13 shows isometrically the assembly of the watch springs,

Fig. 14 shows the allocated portion of the stack holder, and

Fig. 15 is a section view of the watch springs.

Fig. 1 shows the photo changer in plan view with its top shell removed, the top shell being provided with a display window. One will recognize the- slider 40 having skids 49 and a stack holder in the form of a sepa¬ rator bar 16 while rails 1 are mounted on the housing bottom and are supported by springs 11 (see Fig.2). Rails 1 each carry a retainer tape 14 and rockers 4 provided with hooks 5 which serve as retaining means for an individual print to be separated from the stack. The transfer system of the photo changer includes lifting brackets 46 having transverse legs 48 and control legs 50. Pairs of ribs 78, 80 contribute to the separation of that individual print from the stack. When a print stack is placed on the slider and the latter is withdrawn hooks 5 will retain that print which is placed directly on the rails while the separartor bar pushes the remaining prints of the stack outwards. In the outer end position of the slider the separator bar has passed or overrun the outer transverse end edge of the individual print retained in the housing; the lifting brackets engage under that individual print and lift it off the rails so that its other, inner transverse end edge is placed in front of stops 66 while its outer transverse end edge is positioned in front of a return gap, defined by the separator bar and the housing top shell. Upon the slider's being pushed in again, the separator bar slides beneath the individual print which when the slider reaches its.inner end position is

placed on top of the stack. In other word, the print which was the lowermost in the stack has become the topmost upon slider reciprocation.

This is briefly the manner in which the changer operates, and so far, the design of the changer is identical to that of the changers of the prior art as referred to above.

According to the present invention, the bottom 90 of the housing carries two symmetrically disposed sockets 92 molded thereto. Each socket 90 sup¬ ports a leaf spring 94 rivet-fastened to the socket at 96. These springs extend parallel to the slider withdrawal direction and opposite thereto, and they have angled free ends 98. The fastened ends also have angled bends 100 which serve to position the springs on the sockets 90. Once the springs 94 have been so assembled to the housing bottom, the lifting brackets 46 are snap-fitted into bearings 102 such that the transverse bracket leg 48 engages between the springs 94 and a stack of prints placed on the rails. With the slider fully pushed in, its skids have overrun the control legs 50 of the brackets so as to depress them, and the bracket, in turn, will depress the leaf springs 94 which in this manner lie "sunk" with respect to the stack; cf. Fig. 2.

Fig. 3 shows the slider in an intermediate position on its way from the inner towards the outer end position. Let us assume that the slider, instead of being fully withdrawn, is pushed in again: The hooks formed by the angled free ends 98 of leaf springs 94 will "catch" the inner transverse end edge of the individual print 32 and will prevent that the latter is pushed beyond and beneath the stops 66; instead, the inner end edge will remain aligned with the stops.

Fig. 4 clearly shows that short of the fully withdrawn position of the slider the inner lifting bracket has already lifted the inner transverse end edge of print 32 in front of the stops 66, leaf springs 94 in this situation having assumed their relaxed or almost relaxed status. With the slider fully withdrawn, the print 32 has come free, and its outer trans¬ verse end edge is lifted to confront the return gap 7 by means of lifting springs 52 (indicated in Fig. 5 only) which are mounted on the slider

skids. Upon the slider's return stroke (Fig. 5), print 32 passes through the return gap 7. With the slider moving inwards, the leaf springs 94 are more and more depressed by the inner bracket and would tend to take along the inner transverse end edge of print 32. However, the latter is held clamped in the return gap so that the spring ends will eventually release print 32 which finds support on the stops 66 over the remainder of the slider inward motion.

It will be understood that the angled ends of the leaf springs 94 are ex¬ pected to safely retain and support the inner transverse end edge of print 32. On the other hand, these spring ends are expected to easily release the same edge as soon as they begin to be depressed in order to avoid damage of the print edge. In result, the manufacturing tolerances of such a design are necessarily quite strict so that it does not appear to be suited for mass production. There is a further risk: Even if the apparatus is properly operated, that is, the slider is fully withdrawn to reach its outer end position, the stack holder somewhere on its way outwards may "loose" a second print adjacent the individual one retained in the housing. If now the slider is pushed in, the push forces or thrust transmitted to the individual print may be so high that the leaf springs 94 will yield downwards, and the individual print will be curved upwards and ultimately be crunched.

For the reasons described above, the second, improved embodiment of the invention is preferred. It is to a great extent similar to the first one so that the same reference numerals will be used to designate correspon¬ ding elements. They will be discussed again only if their design and/or function are different.

The print changer of the first embodiment is completed by a stop spring arrangement 200 which will be referred to hereinafter as a sensing or watch spring. It is mounted in the top shell of the housing as will be explained later, and located in the area of the plane of symmetry between the rails. The free spring end extending into the housing interior is the active portion of the watch spring.

Fig. 6 through 9 illustrate the events upon a "normal" rearranging opera¬ tion without malfunction or improper handling. In the start position, Fig. 6, the slider is in its inner end position and has deflected the free end of watch spring 200 out of way. Upon slider withdrawal the free spring end relaxes and returns into its rest or watch position as shown in Fig. 7. Fig. 8 illustrates the relative position of the various ele¬ ments shortly after begin of the inwards movement of the slider. It is to be noted that the watch spring has a bend 202 and is positioned, seen in direction of inward slider movement, in front of the angled ends or catch hooks 98 of leaf springs 94. The print 32 which undergoes the exchange is already in the return gap and finds support on the watch spring. The bend 202 causes the inner transverse end edge of print 32 to be displaced up¬ wards where the watch spring, by its nature, is least deflectable. Fig. 9 shows that the leaf springs 94 are depressed again by the inner bracket 46 without having had contact with said inner edge of the print when the slider approaches its inner end position.

Fig. 10 illustrates the malfunction of a so-called double removal where the stack holder has "lost" a second print on its way outwards. This may happen if the photo prints bond together due to high friction so that such a second print will, at the beginning of the slider withdrawal, be overrun together with the individual print 32. However, only the latter is really retained in the housing by the hooks 5 while the former is eventually released from print 32 and taken along with the slider over a certain length. As may be seen in Fig. 10, even if the slider is fully withdrawn, the outer transverse end edge of print 32 cannot be lifted from the rails because the superposed second print 204 held clamped be¬ neath the separator bar forms an obstacle. The inner transverse end edge of print 32, on the contrary, has been lifted already to an extent that it confronts watch spring 200 in a manner similar to that which is shown in Fig. 8.

As mentioned above, under such conditions an extremely high thrust force is transmitted to print 32 upon beginning of the slider return stroke, and that force has, in addition, a downwardly directed component. In re¬ sult, the resistance of the watch spring 200 is insufficient to support

the inner transverse end edge of print 32, and spring 200 begins to yield, cf. Fig. 12. That edge slides along watch spring 200 downwards and is caught by the catch hooks 98 of leaf springs 94 which will pull the print edge downwards. It was mentioned above that under normal opera¬ tional conditions, these hooks do not contact the print edge. Under the conditions of malfunction or improper handling, however, these hooks must not release the edge (contrary to the first embodiment), and this permits to provide these hooks with an overbend or undercut and to make them so high that they may even catch a plurality of print edges.

In the second embodiment just described, the fixed stops 66 are not su¬ perfluous because in the inner slider end position of Fig. 6 the watch spring is inactive so that, without stops.66, the print 32 could remain with its end between the separator bar and the top wall of the housing. It would be unsuitable to provide the separator bar with a large and deep recess permitting passage of watch spring 22 because the separator bar is subjected to high stress. The small recesses which permit passage of the equally small stops 66, on the contrary, are tolerable.

Fig. 13 shows isometrically, and Fig. 15 shows in section how watch spring 200 is mounted in the top shell 206. The watch spring is comprised of two superposed individual springs 200a, 200b each having a depression 208 which cooperates with a recess 210 of the top shell to position the watch spring assembly. The free spring ends extend through an additional recess 212 of the top shell. The top face of spring 200a is flush with the top face of an inner frame 214 of the top shell which is masked by a passepartout 216 (shown partly broken away) and is ultimately covered by a transparent display window 218 (shown partly broken away) which is snap-fitted from the exterior.

The use of two individual springs 200a, 200b permits them to yield back¬ wards while sliding along one another but nevertheless they develop suf¬ ficient resistivity to support print 32.

It will be recognized that in the second embodiment of the invention there is provided a sensing system to detect whether the print engaging

spring arrangement 200 is engaged by a print properly positioned in the return gap so as to transmit only small forces to the spring arrangement in direction of the slider return, or whether the engaging print is held clamped beneath the separator bar so as to transmit high forces in that direction.