Image forming apparatus with sheet handling device

Abstract: An image forming apparatus includes a drum gear (33) having a first guide slot (33a) and a cam (33b), a clamp (35) having a first interlocking pin (35a) inserted into the first guide slot (33a) and a cam pin (35b) interlocked with the cam (33b), a release lever (37) to be elastically biased counter-clockwise on a support plate (34) on which a shaft (32) of a drum (31) is supported, and a lifter (38) whose one end has a second guide slot (38a) coupled to the first interlocking pin (35a) and whose other end has a second interlocking pin (38b) interlocked with the release lever (37). Thus, the apparatus can shorten the overall printing time by reducing the time required from outwardly ejecting a sheet of paper.

Description: BACKGROUND OF THE INVENTION The present invention relates to an image forming apparatus with the features in the preamble of the claim. Referring to FIG. 1, the operation of such a conventional image forming apparatus will be described. When a sheet of paper 2 is fed via an inlet 1, a clamp 5 clamps the entered paper 2 by the elasticity of a spring 6 while a bracket 4 rotates around a hinge by means of a pin 4a operated along a cam 3. Then, as a drum 7 rotates counter-clockwise along with clamping sheet of paper 2, three colors, i.e., yellow, magenta and cyan, are consecutively printed on the paper. Thereafter, during outwardly ejecting the printed sheet of paper 2, drum 7 rotates clockwise to release the clamping of paper 2 in a manner counter to the clamping operation. Successively, when the leading edge of sheet of paper 2 faces an outlet 8, drum 7 rotates counter-clockwise to force the sheet of paper out of outlet 8. That is, in the conventional image forming apparatus constructed as above, while a drum rotates clockwise upon completion of the printing, the clamping of a sheet of paper is released. Then, the drum rotates counter-clockwise, forcing the paper out. For this operation, it takes additional time to outwardly eject the paper, which in turn lengthens the overall printing time by as much. Accordingly, the image forming apparatus of the prior art has difficulty in high-speed printing. SUMMARY OF THE INVENTION Therefore, it is an object of the invention to provide an image forming apparatus with a paper clamping mechanism which allows a printing sheet to be transported towards the ejection outlet at the same time as the last colour is being printed whereby the print throughput is increased by reducing the sheet ejection time. To achieve the above object of the present invention the image forming apparatus as set forth above is characterised by the features of the characterising part of the claim. According to the present invention the overall printing time can be curtailed by that amount of time by which the time required for outwardly ejecting the paper is reduced. BRIEF DESCRIPTION OF THE DRAWINGS The above objects and other advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which: FIG. 1 is a partially cutaway side view showing a conventional image forming apparatus; FIG. 2 is a partially cutaway side view showing an image forming apparatus according to the present invention; FIG. 3 is a partially cutaway side view of the image forming apparatus, taken along line III-III of FIG. 2; FIG. 4 is a partially cutaway side view showing the clamping operation of the present image forming apparatus shown in FIG. 2; FIG. 5 is a partially cutaway side view showing the initial stage of printing operation in the present image forming apparatus shown in FIG. 2; and FIG. 6 is a partially cutaway side view showing the ejecting operation of the present image forming apparatus shown in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGs. 2 and 3, an image forming apparatus according to the present invention is constructed in such a manner that, a drum gear 33 is installed on a rotary shaft 32 of a drum 31. The drum gear is provided with a first guide slot 33a and a cam 33b. The rotary shaft 32 of drum 31 is rotatably supported by a support plate 34. Also, rotary shaft 32 is coupled with one end of a clamp 35 having both a first interlocking pin 35a inserted into first guide slot 33a and a cam pin 35b interlocked with cam 33b of drum gear 33, in such a manner that clamp 35 can rotate and rectilinearly move along radii of the drum. Clamp 35 is elastically biased clockwise by means of a first spring 36. A release lever 37 which is elastically biased counter-clockwise by a second spring 37a, is rotatably installed on support plate 34. A lifter 38 is rotatable on rotary shaft 32 of drum 31, wherein one end of lifter 38 has a second guide slot 38a receiving first interlocking pin 35a of clamp 35 and the other end thereof has a second interlocking pin 38b interlinked with release lever 37. A reference numeral 39 designates a sheet of paper, 40 is a paper-feed roller, 41 is a thermal transfer head, 42 is an ink-ribbon, and 43 is a paper-output roller. Hereinbelow, the operation of the image forming apparatus according to the present invention will be described. To begin with, when paper 39 is supplied by means of paper feed roller 40 as shown in FIG. 2, release lever 37 rotates clockwise to thereby rotate second interlocking pin 38b of lifter 38 counter-clockwise. Accordingly, lifter 38 rotates counter-clockwise. Due to the counter-clockwise rotation of lifter 38, first interlocking pin 35a of clamp 35 which is coupled to second guide slot 38a of lifter 38 is rotated counter-clockwise. By this operation, cam pin 35b of clamp 35 becomes projected from the outer circumference of drum 31 as shown in with the solid-lined shape of FIG. 4, while moving along cam 33b of drum gear 33. Upon the placement of paper 39 at a predetermined position, release lever 37 rotates counter-clockwise, and clamp 35 is released so as to fall into a position illustrated by the virtual line of FIG. 4, by the restoring force of first spring 36, so that paper 39 is clamped. When the clamping of the paper is completed, drum 31 rotates counter-clockwise, which transfers clamp 35 to its initial printing position as shown in FIG. 5. By the transfer of clamp 35 to the initial printing position, thermal transfer head 41 rotates to thus press ink-ribbon 42 onto paper 39. Under this state, while drum 31 rotates counter-clockwise, two colors, i.e., yellow and magenta, are successively printed on paper 39. When the two-color printing is completed, release lever 37 rotates clockwise to thereby rotate first interlocking pin 35a of clamp 35 counter-clockwise. Thus, along with the projection of clamp 35 from the outer circumference of drum 31 while being rotated counter-clockwise by both cam pin 35b formed thereon and cam 33b formed in drum gear 33, the paper is released from being clamped as shown in FIG. 6. Additionally, drum 31 rotates counter-clockwise, resulting in simultaneously printing cyan on paper 39 and outwardly ejecting the sheet of paper by means of output roller 43. In the image forming apparatus as described above, the color cyan, which is printed last, is printed simultaneously as the paper is outwardly ejected As a result, the time required for forcing the paper out can be shortened as compared with the conventional apparatus wherein the paper is ejected after printing has completed, thereby enabling high-speed printing.

Claims: An image forming apparatus comprising a drum (31); a clamp (35) for releasably clamping a sheet of paper to the drum (31); a first spring (36) for providing clamping force to said clamp (35); and a release lever (37) for releasing the clamping force of said clamp (35), characterized by a drum gear (33) installed on a rotary shaft (32) of said drum (31), and provided with a first guide slot (33a) and a cam (33b); said clamp (35) coupled to said rotary shaft (32) of said drum (31) to be rotatable and rectilinearly reciprocative, one end of the clamp (35) having a cam pin (35b) interlocked with said cam (33b) in a paper clamp position of the clamp and having a first interlocking pin (35a) coupled to said first guide slot (33a) and spaced radially inward from the cam pin (35b); said release lever (37) capable of swinging on a support plate (34) on which said rotary shaft (32) of said drum (31) is supported, and elastically biased counter-clockwise by means of a second spring (37a); and a lifter (38) rotatably coupled to said rotary shaft (32) of said drum (31), one end having a second guide slot (38a) into which said first interlocking pin (35a) of said clamp (35) is inserted and the other end having a second interlocking pin (38b), whereby for upwardly moving said clamp (30) from said drum (31) the release lever (37) is in engagement with the second interlocking pin (38b) in a paper supply position of the drum and in engagement with the first interlocking pin (35a) in a paper ejecting position of the drum.

Inventors: PARK GEUN-YONG, PARK, GEUN-YONG
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1993
Main classification: B41J13
IPC codes: B41J13, B41J2, H04N1