Sheet Registration and Clamping Apparatus

This invention relates generally to sheet registration and clamping apparatus, and more particularly, to apparatus which sequentially registers a sheet at a registration location, clamps such sheet at such location, and guides such sheet as it is moved from such location.

In certain reproduction apparatus, such as printers or duplicators, copies of information are reproduced on cut sheets of paper. Typically, the paper sheets are fed seriatim to a support where they are registered and clamped to the support. The support retains the sheet in its registered location while an operation is carried out on such sheet. For example, the support may be moved into engagement with a printing platen where marking particles or ink, in an imagewise pattern corresponding to information to be reproduced, are transferred to the sheet. The sheet is thereafter transported from the support to apparatus for fixing the transferred pattern to the sheet to form the desired reproduction.

Prior reproduction apparatus employ many different mechanisms for registering and clamping a sheet to the support. Most commonly, the mechanisms include a plurality of clamps mounted on the support, each clamp having a registration portion and a portion extending from the registration portion in a direction upstream of the travel of a sheet toward the registration portion. As a sheet is registered against the registration portions, the extending portions are moved to clamp the lead edge of the registered sheet between such extending portions and the support. Such mechanisms are generally effective to carry out their intended registration and clamping functions. However, if there is significant curl in the lead edge of a sheet being registered, the extending portions of the mechanisms can interfere with movement of the sheet toward the registration portions. Moreover, the lead edge of a registered sheet must somehow be lifted over the extending portions on transport of the sheet away from the mechanism after the work operation (e.g., image transfer) is performed on the registered sheet.

This invention is directed to apparatus for sequentially registering a sheet, movable along a travel path, relative to such travel path, clamping such sheet at its registered location and guiding such sheet as it moves from its registered location. Such apparatus, which overcomes the aforementioned difficulties associated with prior sheet registration and clamping mechanisms, comprises an elongated member having a sheet registration portion, a sheet clamping portion, and a sheet guiding portion. The elongated member is sequentially moved relative to the sheet travel path to first, second and third positions. In the first position, the registration portion intercepts and stops a moving sheet at a registration location to effect registration of the sheet, and the sheet clamping portion and sheet guiding portion are inoperative. In the second position, the sheet clamping portion secures the registered sheet at such registration location. In the third position the clamping portion releases the registered sheet, and the sheet guiding portion guides the sheet as it moves away from the registration location.

The invention, and its objects, and advantages, will become more apparent in the detailed description of the preferred embodiment presented below.

In the detailed description of the preferred embodiment of the invention, reference is made to the accompanying drawings, in which:

FIG. 1 is a plan view of the sheet registering, clamping and guiding apparatus according to this invention,

FIG. 2 is a side elevational view, partly in cross-section, of the sheet registering, clamping and guiding apparatus of FIG. 1, taken along lines 2--2 of FIG. 1.

FIG. 3 is a graphical representation of the movement of the sheet registering, clamping and guiding apparatus according to this invention plotted as the vertical movement of such apparatus (h) vs. the angle of rotation of such apparatus (.theta.);

FIGS. 4A through 9A and 4B through 9B are plan views and side elevational views respectively of the sheet registering, clamping and guiding apparatus according to this invention taken at sequential stages in the operation of such apparatus.

Referring now to the accompanying drawings, the sheet registering, clamping and guiding apparatus is generally designated by the numeral 10. As best shown in FIGS. 1 and 2, the apparatus 10 comprises an elongated member 12 including a sheet registration portion defined by a shank 14 of substantially circular cross-section. The shank 14 is supported in bearings 15 for reciprocation along, and rotation about, its longitudinal axis L. A rotary motor 16 has an output shaft 18 operatively coupled to end 14a of the shank 14 to selectively rotate the shank about its longitudinal axis L. The opposite end 14b of the shank 14, defining a sheet guiding portion, is formed as a planar surface oriented at an angle .alpha..sub.1 to the longitudinal axis of such shank. A sheet clamping portion, defined by member 20, is connected to the shank 14 adjacent to the end 14b at its highest point. The member 20 extends substantially radially from the shank 14 and lies in a plane intersecting the longitudinal axis of the shank at an angle .alpha..sub.2, for example, substantially equal to the angle .alpha..sub.1 of surface 14b. While the apparatus 10, according to this invention, is described as comprising a single elongated member, it is, of course, apparent that any appropriate member number of similarly constructed elongated members may be utilized in the apparatus.

The elongated member 12 is located to extend through an opening 22 in a plate 24 having a surface 24a for supporting a sheet and defining a sheet travel path. The plate 24 may be, for example, a sheet support of a printer or duplicator and as such may be planar or curvi-linear. The longitudinal axis L of the shank 14 of the elongated member is substantially perpendicular to the plane of the sheet supporting surface 24a and intercepts the travel path of a sheet movable along such surface. A stationary pin 26 extends from a support member 28 fixed to the undersurface of the plate 24. The pin 26 is received in a circumferential groove 30 formed in the shank 14. The groove 30 has a profile such that, on rotation of the shank 14 about its longitudinal axis L, the cooperation of the pin 26 and groove 30 causes the shank to reciprocate along its longitudinal axis relative to the plane of surface 24a for the purpose to be explained hereinbelow. FIG. 3 graphically shows a plot P of the reciprocation of the shank 14 of the elongated member 12 as the shank rotates about its longitudinal axis. That is, the plot P represents the vertical movement, designated as h, of the topmost portion of surface 14b relative to the plane of surface 24a at the corresponding angular positions of the shank, designated .theta., starting from its position shown in FIG. 4.

In the operation of the apparatus 10, the shank 14 of the elongated member 12 is rotated by the motor 16 to its initial position as shown in FIG. 4A. This is the position where .theta. equals 0.degree. in FIG. 3, with the surface 14b being located at its maximum elevation h.sub.max above the plane of surface 24a. At the initial position, the shank 14 intercepts the travel path of a sheet S delivered to the plate 24 and traveling along a path in the direction of arrow A along the surface 24a of plate. On engagement of the sheet with the shank, the sheet is stopped at a registration location. Moreover, in such initial position, the clamping member 20 and the surface 14b are significantly above the plane surface 24a and directed relative to the sheet travel path so as to be in an inoperative relation to such path. Therefore, the clamping member does not interfere with sheet movement to its registration location (i.e., into engagment with shank 14).

A sensor 32, such as a photoelectric device or a mechanical switch, detects the lead edge of a sheet moving into engagement with the shank 14 and generates a signal upon such detection. Such. signal is used to actuate motor 16. Thus, in response to the movement of a sheet S along the surface 24a into engagement with the shank 14 of the elongated member 12, the motor 16 is actuated to rotate the shank from the initial position (in a counterclockwise direction when viewing FIGS. 4A through 9A). As described above, on rotation of the shank, the stationary pin 26 cooperates with the groove 30 to reciprocate the shank along its longitudinal axis L according to the profile of the groove. Rotation of the shank 14 to the position of FIGS. 5A, 5B (.theta. equals 45.degree.) brings the clamping member 20 over such lead edge at an elevation significantly above the sheet on the plate 24. The clamping member is thus prevented from damaging the lead edge of the registered sheet. Continued rotation of the shank to the position of FIGS. 6A, 6B (.theta. equals 90.degree.) results in the clamping member 20 being reciprocated toward the plate 24 to secure (clamp) the sheet S at its registration location. After clamping is effected, the motor 16 is deactuated and rotation of the shank is interrupted. Due to the profile of groove 30, reciprocation of the shank to its clamping position (designated h.sub.CL in FIG. 3) is rapidly and smoothly accomplished to assure proper clamping of the sheet without damage to such sheet. Thereafter, any required operation on the sheet, (for example, image transfer to such sheet) can then be effected with the sheet remaining in its registered location clamped to plate 24.

Subsequent to such operation on the sheet, the motor 16 is reactuated to further rotate the shank 14 of the elongated member 12 in the same (counterclockwise) direction. During such further rotation to the position of FIGS. 7A, 7B (.theta. equals 180.degree.), the groove profile ensures that the shank is reciprocated in an upward direction to its maximum elevation above plate 24 (designated h.sub.max in FIG. 3) to move the clamping member 20 rapidly out of engagement with the sheet and release the sheet. When the clamping member 20 has fully cleared the lead edge S of the registered sheet (when viewed from above), further rotation of the shank to the position of FIGS. 8A, 8B (.theta. equals 225.degree.) reciprocates such shank in a downward direction relative to the plate 24. In such position, the shank 14 is oriented about its longitudinal axis L to position the clamping member on the opposite side of the shank from the registered sheet, thereby preventing the clamping member from interfering with movement of the sheet from its registration location.

On rotation of the shank 14 to the position of FIGS. 9A, 9B (.theta. equals 270.degree.), the profile of groove 30 causes such shank to be reciprocated to an elevation (designated h.sub.REL in FIG. 3). At such location, the surface 14b extends from below the level of surface 24a to above the level of such surface in the direction of travel of a registered sheet from its registration location. The motor 16 is again deactuated to interrupt rotation of the shank so that such shank remains in this position. The sheet is then moved downstream in the direction of arrow B away from its registered location. The surface 14bb serves as a guide surface for the sheet to assure the sheet clears the elongated member 12 without interference and without having to lift the sheet clamping members as required in prior mechanisms. After the sheet has cleared the elongated member 12, the motor 16 is reactuated to rotate shank 14 to return it to its initial position of FIGS. 4A, 4B (.theta. equals 0.degree.). The elongated member 12 is thus ready for sequentially registering, clamping and guiding the next sheet delivered to the plate 24.

The invention has been described in detail with particular reference to a preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.