Image forming device with variable paper feeding capacity

Abstract: An image reproduction device is described, including a housing 10 including engagement means for a paper cassette 90, 90' and a paper feeding device for feeding papers from the paper cassette. Two paper cassettes, a relatively shallow, relatively low capacity paper cassette and a relatively deep, relatively high capacity paper cassette, are provided. Each cooperates with the engagement means so as to be retained beneath the housing. Removable height compensating members cooperate with the base of the housing to raise the housing, and hence the cassette mounting portion, allowing the high capacity paper cassette to be used.

Description: BACKGROUND OF THE INVENTION The present invention relates to an image forming device which uses paper from a paper cassette and in particular to such a device with variable paper feeding capacity. As shown in FIG. 1, in a conventional laser beam printer, a photosensitive drum 2 receives a light signal from a light source 1 and forms from it an electrostatic latent image. When the photosensitive drum 2 rotates, toner T is moved to the electrostatic latent image, by electrostatic forces, from a developing roller 3 to which the toner is adhered. Paper P in a paper cassette 9, which maintains a fixed feeding pressure against a pick up roller 4 using the resilient force of a spring 9a, is fed one sheet at a time through operation of the pick up roller 4, delivered to a register roller 5 and conveyed while in contact with the surface of the photosensitive drum 2, to accord with the latent image of the photosensitive drum 2 at the proper time. A high voltage, greater than the electrostatic potential of the photosensitive drum 2, is applied across a transfer device 6, to convey the latent image onto the paper. The paper which is pigmented by the toner, is then conveyed to a fixing device 7, and the toner is fused to the paper by heating. A laser beam printer using such principles and operation includes a paper feeding device 8 for feeding the paper P one sheet at a time, and the paper feeding device 8 also comprises a paper cassette 9 which is filled with multiple sheets of paper P. When a certain model of the printer is selected, it is usually limited to only one paper cassette 9. Accordingly, the paper cassette 9 cannot offer paper continually. However, the paper feeding capacity of the paper cassette 9 has a very important role to play in accordance with the environment in which the printer is used. When a person uses a laser beam printer at home, the paper cassette usually holds fewer than 100 sheets of paper. But when several people require greater quantities of paper in the office, the paper cassette should hold more than 500 sheets of paper, to supplement the paper in the paper cassette. Accordingly, paper cassettes have hitherto been manufactured to hold 150 to 250 sheets of paper, and only one of them is used, depending upon the use to which the printer will be put. Consumers are apt to purchase printers with low capacity paper cassettes for use at home and, on the other hand, printers with paper cassettes for holding more paper tend to be used in office. However, it is not always the case that less paper is used at home and more paper in the office. Rather, the amount of paper used is determined by the usage requirements of the users. Conventional laser beam printers employ a paper cassette for holding either 150 or 250 sheets of paper, irrespective of the usage requirements. However, when few sheets of paper are used by a printer with a high capacity paper cassette, the printer takes up an unnecessarily large amount of space, due to the large sized paper cassette. On the other hand, when more sheets of paper are used by a printer with a low capacity paper cassette, paper must frequently be supplemented. To solve this problem, a separate optional second cassette has been proposed, which holds multiple sheets of paper, as described in Korean patent application no. 96-3501. This second cassette operates separately, so that its cost is high. The size of the second cassette is very large, as compared with its paper holding capacity so that it is not economical and efficient for general printer users. EP-A-121,908 ("MITA") describes a copying machine that having a housing including, on the bottom of the housing, a paper feeding device for feeding papers from a paper cassette, a plurality of bases or side walls of a first height defining a first space between them, and a cassette mounting portion including engagement means for the paper cassette. A relatively shallow, relatively low capacity paper cassette and a relatively deep, relatively high capacity paper cassette can be used with the device and to this end, each of the bases or side walls is provided with a fixed leg that raises the copying machine higher off the ground. Thus, the device is at all times capable of accommodating either cassette. SUMMARY OF THE INVENTION The object of the present invention is to provide an improved image forming device, such as a laser printer, with variable paper feeding capacity. Accordingly, the present invention provides an image-forming device comprising: a housing including, on the bottom of the housing, a paper feeding device for feeding papers from a paper cassette, a plurality of bases of a first height defining a first space between them, and a cassette mounting portion including engagement means for the paper cassette; and a relatively shallow, relatively low capacity paper cassette and a relatively deep, relatively high capacity paper cassette, each being adapted to cooperate with the engagement means so as to be retained beneath the housing; characterised in that: the engagement means comprises cassette mounting rails; the low capacity paper cassette has first cassette channels adapted for sliding engagement with the cassette mounting rails to retain it beneath the housing and is of a height substantially equal to the said first height and adapted to occupy the said first space when so retained beneath the housing; the high capacity paper cassette has second cassette channels adapted for sliding engagement with the cassette mounting rails to retain it beneath the housing and is of a second height greater than the said first height and adapted to occupy a second space greater than the said first space when so retained beneath the housing; and the device further includes removable height compensating means adapted to cooperate with the bases of the housing to raise the cassette mounting portion of the housing by an amount substantially equal to the difference between the said first and second heights and provide additional space substantially equal to the difference between the said first and second spaces, thus allowing the high capacity paper cassette to be used. There may be a cassette mounting rail on each side of the cassette mounting portion of the housing and each of the paper cassettes may include on each side a channel along which the corresponding cassette mounting rail slides. As usual, each of the paper cassettes may include a resiliently biased paper support plate. The height compensation means may comprise one or more height compensation members adapted for attachment to the base of the housing on both sides of the cassette mounting portion. It may be adapted to be fixed to the housing with screws or hooks. Two separate height compensation members may be provided, adapted for attachment to the base of the housing on respective sides of the cassette mounting portion. Alternatively, two height compensation members may be provided, adapted for attachment to the base of the housing on respective sides of the cassette mounting portion, the two height compensation members being connected to each other by means of a connecting piece to form a single member. The housing and the height compensation means preferably include position determination projections and recesses position them correctly with respect to one another BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS The present invention will now be described by way of example with reference to the accompanying drawings in which: FIG. 1 is a schematic diagram of one side of a conventional laser beam printer; FIG. 2 is a side view of the conventional laser beam printer; FIG. 3 is an exploded perspective view of important portions of a laser beam printer according to the present invention; FIG. 4 is an exploded perspective view of important portions of a laser beam printer according to a first preferred embodiment of the present invention; FIG. 5 is a frontal view of a printer, which shows a section of an important portion of the printer where a first cassette is mounted, according to the present invention; FIG. 6 is a frontal view of a printer which shows a section of an important portion where a second cassette is mounted, according to the present invention; FIG. 7 is a sectional view taken along the lines A-A of FIG. 6; FIG. 8 is an exploded perspective view of important portions of a laser beam printer according to a second preferred embodiment of the present invention; FIG. 9 is a frontal view of a printer, which shows a section of an important portion of the printer where a cassette with large paper holding capacity is mounted, according to the second preferred embodiment of the present invention; FIG. 10 is an exploded perspective view of important portions of a laser beam printer according to a third preferred embodiment of the present invention; FIG. 11 is a sectional view of an important portion of the third preferred embodiment of the present invention, which explains the fixation of a height control member; and FIG. 11B is a sectional view of an important portion of the printer where the height control member is mounted, according to the third preferred embodiment of the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENT FIGs. 3 through 7 show the first preferred embodiment of the present invention. A cassette mounting portion 11 is formed at the base of a housing 10 and housing bases 12 and 12' are formed at both sides of the cassette mounting portion 11. As shown in FIG. 3, a cassette mounting rail 13 is provided inside the housing bases 12 and 12'. When one of the paper cassettes 90 and 90' is inserted into the cassette mounting portion 11, the cassette mounting rail 13 mates with a channel 19 which is formed at both sides of the paper cassette 90 or 90'. After one paper cassettes 90 or 90' is mounted in the cassette mounting portion 11, the cassette mounting rail 13 is interrupted by the channel 91, so that the paper cassette 90 or 90' itself is supported by the housing 10. At least two paper cassettes 90 and 90' are provided to be selectively mounted at the cassette mounting portion 11, in the present invention. The paper cassette 90 or 90' comprises a paper supporting plate 93 which is biased by a spring 92, and a handle by which they are inserted into or pulled out of the housing 10. Additionally, a paper holding portion 94 is formed at the top of the paper supporting plate 93, where paper P is accumulated. The paper cassettes 90 and 90' of the present invention have paper holding portions 94 whose sizes are different from each other. Referring to FIG. 3, the length and breadth of the paper holding portions of the two paper cassettes 90 and 90' are the same, but their heights h and H are dissimilar. The dimensions ha and Ha where the channel 91 stands, are the same, at both sides of the top of the paper cassettes 90 and 90'. The dimensions hb and Hb from the channel 91 to the base of the paper cassettes 90 and 90' are different. Accordingly, there is a difference between the dimensions h and H of the paper holding portions so that their paper holding capacities differ. The cassette with the lower height and fewer sheets of paper will be referred to as a low capacity paper cassette and the cassette of greater height H and more sheets of paper will be referred to as a high capacity paper cassette. As depicted in FIG. 5, if the low capacity paper cassette 90 is fixed to the cassette mounting portion 11 of the housing 10, the housing base 12 and 12' is flush with that of the low capacity paper cassette 90. When the low capacity paper cassette 90 is taken out of the cassette mounting portion 11 before the high capacity paper cassette 90' is inserted, the height H of the high capacity paper cassette 90' is greater than that of the cassette mounting portion 11 which is formed in the housing 10, so that the high capacity paper cassette 90' cannot be accommodated. Accordingly, when the high capacity paper cassette 90' is selected, height compensation members 100 and 100' are provided for the housing base 12 and 21', to increase the height of the cassette mounting portion 11 of the housing 10. The height compensation members 100 and 100' take the same shape as the base of the housing 12 and 12' and have the same height as the height difference between the low capacity paper cassette 90 and the high capacity paper cassette 90'. The height compensation members 100 and 100' are fixed to the base of the housing 12 and 12' by multiple fixing screws 14. A position determination projection 15 of the housing base 12 and 12' is inserted into a position determination recess 101 so that the housing base 12 and 12' and the height compensation members 100 and 100' are correctly positioned. Supporting projections 16 and 110 are formed at the front and back of the housing base 12 and 12' and the height compensation members 100 and 100' respectively. A rubber support 111 is fitted in the front supporting projection 110 of the height compensation members 100 and 100'. The rubber support 111 has a high friction coefficient and therefore serves to prevent the housing 10 from slipping. It is no matter whether or not the support 111 is provided. This is because the weight of the housing 10 itself is considerable. Therefore, the weight of the housing 10 itself can prevent the slipping of the housing 10 unless any external force is applied to the housing 10. FIG. 6 shows the high capacity paper cassette 90' inserted into the cassette mounting portion 11, according to the present invention. The low capacity paper cassette 90 is pulled out of the cassette mounting position 11, before the housing 10 is laid on its side. The height compensation members 100 and 100' are coupled with the housing base 12 and 12' by the fixing screws 14. Accordingly, the height of the cassette mounting position is increased. The housing 10 which is laid on its side is then righted before the high capacity paper cassette 90' is fixed in the cassette mounting position 11 whose height has been increased. Accordingly, the base of the high capacity paper cassette 90' is flush with that of the height compensation members 100 and 100'. On the other hand, the high capacity paper cassette 90' can be taken out of the cassette mounting portion 11, to be replaced with the low capacity paper cassette 90, before the housing 10 is laid on its side. The screws 14 are loosened to separate the height compensation members 100 and 100' from the housing 10, before the low capacity paper cassette 90 is inserted into the cassette mounting portion 11 whose height has once more been decreased. FIGs. 8 and 9 show a second preferred embodiment of the present invention. The second preferred embodiment differs from the first preferred embodiment in the structure of the height compensation members 100 and 100'. The height compensation members 100 and 100' form the respective housing bases 12 and 12' at both sides of the cassette mounting portion 11, and thus should be in pairs. If the height compensation members 100 and 100' are parts which are independently made, as in the first preferred embodiment of the invention, one of them may be lost and the high capacity paper cassette 90' then cannot be used. Accordingly, the height compensation members 100 and 100' are connected to each other with a connecting piece 120 and form one part. A separate member may connect the height compensation members 100 and 100' using some form of fixing means, but the height compensation members 100 and 100' and the connecting piece 120 are preferably integrally moulded, because the height compensation members 100 and 100' are fabricated in the same material as the housing 10. The integrally formed height compensation members 100 and 100' take up more storage space, but the danger of losing them is considerably reduced. The members have the same structure and operation as those according to the first preferred embodiment so that no explanation of that is required here. FIG. 10 and FIGs. 11A and 11B show the third preferred embodiment of the present invention. The height compensation members 100 and 100' are coupled to the base of the housing 12 and 12' by means of hooks, not the fixing screws of the first and second preferred embodiments. Fixing screws 14, being separate small parts, are apt to be lost. It is troublesome to tighten up and loosen the screws. Multiple hooks 130 are formed on the top of the height compensation members 100 and 100'. As shown in FIGs. 11A and 11B, the hooks 130 are inserted into apertures 17 formed on the base of the housing 12 and 12', so that the height compensation members can be coupled with the base of the housing. The height compensation members 100 and 100' with the hooks 130 are pushed toward the housing bases 12 and 12' to be coupled and pulled away to be disassembled. Here, the height compensation members 100 and 100' are held, pulled and separated from the apertures 17, with some considerable force. The height compensation members 100 and 100' can be coupled with the base of the housing bases 12 and 12', through any fixing means as well as the fixing screws 14 and hooks 130. As described above, users selectively employ a paper cassette with proper paper feeding capacity, in accordance with the required usage of the printer, so that the printer can be efficiently used. The paper cassettes with different paper feeding capacity are simply and easily replaced with each other, if necessary. The reliability of products is enhanced, with the relatively simple structure and variable paper feeding capacity. The present invention is applied not only to laser printers, but also to duplicating (photocopying) machines and facsimiles which operate through the same principle and have the same paper feeding device as laser printers.

Claims: An image-forming device comprising: a housing (10) including, on the bottom of the housing, a paper feeding device for feeding papers from a paper cassette (90, 90'), a plurality of bases (12, 12') of a first height defining a first space between them, and a cassette mounting portion (11) including engagement means (13) for the paper cassette (90, 90'); and a relatively shallow, relatively low capacity paper cassette (90) and a relatively deep, relatively high capacity paper cassette (90'), each being adapted to cooperate with the engagement means (13) so as to be retained beneath the housing (10); characterised in that : the engagement means comprises cassette mounting rails (13); the low capacity paper cassette (90) has first cassette channels (19) adapted for sliding engagement with the cassette mounting rails (13) to retain it beneath the housing (10) and is of a height substantially equal to the said first height and adapted to occupy the said first space when so retained beneath the housing (10); the high capacity paper cassette (90') has second cassette channels (19) adapted for sliding engagement with the cassette mounting rails (13) to retain it beneath the housing (10) and is of a second height greater than the said first height and adapted to occupy a second space greater than the said first space when so retained beneath the housing (10); and the device further includes removable height compensating means (100, 100') adapted to cooperate with the bases (12, 12') of the housing (10) to raise the cassette mounting portion (11) of the housing (10) by an amount substantially equal to the difference between the said first and second heights and provide additional space substantially equal to the difference between the said first and second spaces, thus allowing the high capacity paper cassette (90') to be used. A device according to claim 1 in which the engagement means comprises a cassette mounting rail (13) on each side of the cassette mounting portion (11) of the housing (10) and each of the paper cassettes (90, 90') includes on each side a channel (19) along which the corresponding cassette mounting rail (13) slides. A device according to any preceding claim in which each of the paper cassettes (90, 90') includes a resiliently biased paper support plate (93). A device according to any preceding claim in which the height compensation means (100, 100') comprises one or more height compensation members (100, 100') adapted for attachment to the bases (12, 12') of the housing (10) on both sides of the cassette mounting portion (11). A device according to any preceding claim in which the height compensation means (100, 100') is adapted to be fixed to the housing with screws or hooks. A device according to any preceding claim in which two separate height compensation members (100, 100') are provided, adapted for attachment to the bases (12, 12') of the housing (10) on respective sides of the cassette mounting portion (11). A device according to any one of claims 1-6 in which two height compensation members (100, 100') are provided, adapted for attachment to the bases (12, 12') of the housing (10) on respective sides of the cassette mounting portion (11), the two height compensation members (100, 100') being connected to each other by means of a connecting piece (120) to form a single member. A device according to any preceding claim in which the housing (10) and the height compensation means (100, 100') include position determination projections and recesses to position them correctly with respect to one another. A device according to any preceding claim which is a printer.

Inventors: CHO WON-MO, CHO, WON-MO
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1997
Main classification: B41J13
IPC codes: B41J13