Transport Device for Individual Sheets to Be Combined Into a Stack

The present application relates to a commonly assigned application Ser. No. 345,242, now U.S. Pat. No. 4,447,053, entitled "Device For Separating Individual Sheets Combined Into A Stack" and filed of even date herewith.

The invention concerns a device for handling individual sheets to and from a stack, particularly, film sheets for x-ray devices, in which each individual sheet of the stack is transferred between a lateral plane defining the top of the stack and sheet transport roller means.

A known problem in existing film exchanges, particularly in connection with x-ray installations, is the separation of individual sheets of flat film stacked in a feeder magazine in such a manner that only one sheet is transported to the exposure station of the film exchanger. Delivery of a plurality of sheets simultaneously would make an exposure impossible.

One known type of feeder magazine utilizes a sheet drive or transport means in which an upper drive roller forms a nip with a lower running lower so that the sheet conveyed to the drive roller is seized between the drive and running rollers, enabling the drive roller to pass the sheet to or from a storage housing. The running roller is intermittently swiveled into the plane of the drive roller to form the transport nip. A disadvantage of this known arrangement occurs in the rapid transporting of film sheets since when the running roller is pivoted against the drive roller it can rebound and continuity of film transport may be disrupted. Under certain circumstances, the rebound effect on the running roller can result in several film sheets being transported together. In addition, when the running roller strikes the drive roller, vibrations arise in the film exchanger device which can ultimately lead to disturbances in sensitive components, as well as possibly disrupt picture quality in the film exchanger connected to the transport device.

The present invention calls for film transport means for use in a film sheet storage mechanism that can assure the transport of individual sheets one at a time regardless of the transport velocity and avoids detrimental vibrations resulting in the drive roller.

A film sheet magazine in which individual film sheets of a stack are received or transmitted in a film exchanger installation includes at least one rotary screw device for guiding the sheets one at a time into or out of the magazine. The thread pitch of the screw (the thread pitch referring to the spacing of adjacent grooves of the screw threads) is greater than the thickness of a respective sheet in the stack. Sheet transport means are disposed in the magazine overlying the uppermost sheet of the stack. The transport means include a main drive roller disposed in one plane and a running roller disposed in a plane parallel to and beneath the first plane, with both the rollers being arranged for rotation about parallel axes. A sheet being transported to or from the stack is pressed through a nip formed between the drive roller and running roller during movement of the sheet into and out of the magazine. The running roller is mounted on a rotary member, preferably connected to or being part of the rotary screw, for movement away from the drive roller and movement to a position underlying the drive roller for formation of the transport nip. The rotary member containing the running roller rotates about a vertical axis perpendicular to the rotational axis for the drive roller, such that an improved gripping of the individual film sheet in the transport nip occurs and vibrations usually caused by rebounding of the running roller against the drive roller are avoided. In accordance with the invention, the film transport action of the rollers may be synchronized with any randomly chosen film delivery frequency.

The rotary part on which the running roller is disposed is formed with an annular thread-like groove for engaging and guiding the lateral edges of each sheet running through the transport nip formed by the rollers. Along the side of the rotary part opposite from the running roller, the groove leads into the screw threads formed on the screw member. Rotation of the screw serves to vertically conduct sheets within the magazine separated from one another in the stack by virtue of the thread pitch. Accordingly, film sheets are always individually conveyed into or out of engagement with the transport means one after another for delivery to or receipt from the film exchanger.

FIG. 1 is side cross-sectional view of a sheet film magazine for a film changer having an individual sheet separating device and transport device in accordance with the present invention.

FIG. 2 is a broken-away plan view of the sheet film magazine of FIG. 1.

FIGS. 1 and 2 show transport roller means 1 used for conducting individual flat film sheets to or from a magazine housing 2 in a film exchanger system, such as an x-ray installation. The individual film sheets 3 are arranged in a vertical stack one on top of the other within the housing. The housing 2 is constructed with a substantially horizontally directed first end and an opposed upwardly curved end 4 which is bent so that the film sheets 3 are fixed in a curved stack within the housing. The upwardly curved end 4 of the housing provides for a compact spatial arrangement.

The transport means 1 includes laterally spaced apart drive rollers 5 disposed for rotation about a laterally directed axle 6 which is driven by a suitable reversible rotary motor 7. The drive rollers 5 are disposed in a plane overlying the top of the sheet stack within the housing. The transport means 1 further includes a pair of running rollers 8 respectively secured to two rotary members 9 positioned laterally outward of the drive rollers 5. The rotary members 9 turn on axles 10 having vertical axes which intersect perpendicularly with the laterally disposed axle 6.

Each rotary member 9 is formed with a downwardly sloping or thread-like lateral groove 11 for receiving and guiding individual film sheets 3 upwardly for engagement with the drive rollers 5 as further described below. The groove 11 is formed of a thread pitch which corresponds to at least the diameter of the running roller 8. At that side of the rotary member 9 substantially opposed from the running roller 8, the groove 11 connects to annular screw threads 13 formed on a screw member 12 forming the lower portion of the rotary part 9. The screw 12 serves to individually separate the film sheets 3 in the stack and the threads 13 of the screw are connected substantially without interruption to the lower end of the groove 11, such that corresponding side edges of each sheet may be passed between the screw threads 13 and the groove 11 in continuous fashion. The thread pitch of the screw 12 corresponds from two up to ten times the thickness of an individual film sheet 3, but is preferably substantially less than the pitch of the groove 11. In accordance with the preferred embodiment, the rotary part 9 is a one-piece member containing the groove 11 and the screw portion 12. The rotary part 9 is connected for rotation about its vertical axis via a shaft 10 driven by a suitable reversible rotary motor 14.

The laterally spaced apart portions of the transport means 1 serve to act upon opposed sides of each film sheet during transport of the sheet to and from the magazine 2 and are synchronously operated.

As shown in the Figures, the magazine 2 is loaded with a stack of film sheets and arranged for feeding to a film exchanger 18. The magazine may alternatively be connected to a suitable loading device not shown to permit loading of the film sheets into the housing. It is intended that the magazine housing 2 be mounted so as to be removable from connection with the film exchanger 18.

During loading of the magazine housing 2, the drive rollers 5 are turned in the direction of arrow 15 at a suitable constant speed. The sheet of film 3 is then inserted into a slot-like opening 16 laterally formed along the horizontally disposed end of the magazine housing to the extent that the opposed sides of the film sheet are received and guided in the groove 11 until an upper surface portion of the sheet engages with the lower ends of the drive rollers 5. The rotary motors 14 are then switched on so that the rotary parts 9 turn about shafts 10 until the running rollers 8 are placed substantially beneath the drive rollers 5 as shown in the Figures. In this manner, the film sheet 3 is pressed within a transport nip formed between the drive rollers 5 and the running rollers 8. The motors 14 are then switched off, such that the running rollers retain this position, and the film sheet is conveyed fully into the magazine housing by virtue of rotation of the drive rollers 5 until the tail end of the sheet reaches the position within the housing as shown in FIG. 2. The motors 14 are again turned on such that the rotary members 9 along with the screws 12 are now turned in the direction of the arrows 20 and the sheet of film loaded into the housing is conducted by the grooves 11 to the beginning of the threads 13 of the screws.

When the running rollers 8 again stand beneath the drive rollers 5, a successive film sheet may have already been fed through the slot 16 in the manner of the first sheet for engagement against the lower circumferential surfaces of the drive rollers 5. Due to the rotary motion of the rotary members 9, the first sheet of film is transported downwardly within the housing along the threads 13 of the screws 12. The speed of the rotary members 9 and of the screws 12 connected thereto can thus be controlled as a function of the desired transport frequency of the film sheets 3. The process described above is repeated until the magazine 2 is filled with a completed stack.

After the magazine has been loaded, it is re-connected to the film exchanger 18. In order to conduct individual sheets of film out of the magazine housing, the loading operation is carried out in reverse sequence. The drive rollers 5 are turned in the direction of the arrows 19 at a suitable constant speed. The rotary members 9 along with the screws 12 are turned in the direction of arrows 17, so that the uppermost sheet of the stack is conveyed up to the drive rollers 5 by means of the grooves 11. The underlying sheets of the stack are simultaneously passed upward along the screw threads 13. When the running rollers 8 are substantially beneath the drive rollers 5 to form the transport nips, the uppermost film sheet is pressed in the nips between the rollers and this sheet is conveyed out of the magazine 2 through the lateral slots 16 into the film exchanger 18 for exposure. During a further rotation of the rotary members 9, the next adjacent film sheet of the stack is conveyed to the drive rollers 5 and delivered to the film exchanger in the manner described above.

After exposure in the exposure station, each film sheet is transported to a collector magazine connected to the film exchanger 18. The transfer of sheets of film 3 into the collector magazine may correspond to the operation described above in connection with the loading of the magazine 2. The collector magazine having a stack of exposed film sheets may be connected to a developing device and the sheets of film of the stack may be successively transported out of the collector magazine in accordance with the manner described above in connection with the discharge of sheets from the magazine housing 2.

Although various minor modifications may be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted herein all such modifications as reasonably and properly come within the scope of my contribution to the art.