Transmission of power in a printing device

Abstract: Modules, such a paper tray (21), are stacked under a printer (3). Power to drive the paper feed originates from the printer. A housing (9; 27) carries a shaft (17; 33) which is keyed to turn with the housing. The shafts have abutment surfaces (47) which mesh with abutment surfaces on the housing (29). A thrust bearing (51) supporting the housing has a configured bottom to permit limited adjustment by rotation of the housing around a gear (35) at the opposite end of the housing. The tops of the modules under the printer extend past their general frame and have a conical guide surface (23) to direct an entering shaft. The bottom of the modules has an opening (19e) to receive the extended part from a module on which it is stacked.

Description: This invention relates to the mechanical transmission of power between separate modules which are brought together in a printing system. In a printing system a number of optional modules may be stacked together to form a printing station with selected features. Typically, paper or other sheets must be fed from or through all of such modules. When the paper feed motor is in the printer, a mechanical transmission is required to bring power to the other modules. Gear trains are impractical for such extended transmission distances because of a large number of parts and low mechanical efficiency. Also, preferably the modules are brought together with automatic linking between the transmission mechanisms of the options. U.S. Patent No. 5,392,710 discusses a printer and a modular feeder brought together with such automatic linking by a clutch and pin mechanism. The present invention employs a drive shaft. The following disclose generally similar drive shafts, but not with automatic linking: U.S. Patents Nos. 2,079,688, 2,115,975, 3,087,353, 3,473,410 and 3,599,966. U.S. Patent No. 4,541,625 employs a spring mounted drive shaft to assist in linking. The following disclose spring mounted drive shafts, but not in combined modules: U.S. Patents Nos. 1,631,236, 2,567,127, 3,815,380, 4,270,367 and 5,098,343. GB 2141520A discloses a separable drive shaft connector for use in a withdrawable paper tray unit. The connector comprises a cone shaped male member and a cooperating female member having a recessed end to receive the male member. DE 3920162 A1 discloses a printing system apparatus including, for power transmission: an enlongate housing having along the longitudinal axis of said housing a cavity; a gear integral with said housing with it axis concentric with said longitudinal axis of said housing; a shaft partially inserted in said cavity; a resilient member mounted between said shaft and said elongate housing to push said shaft longitudinally away from said housing, and an abutment surface on the end of said shaft away from said housing. The present invention is characterised over DE 3920162 A1 in that the apparatus further comprises a bearing supporting said elongate housing at a position spaced from said gear, said bearing having extensions on opposite sides which rest on a frame of said apparatus, said extensions having curved bottoms to permit limited rotation of said housing generally around a pivot point located at said gear, said bearing being free for such limited movement. Various aspects of the present invention are set forth in the appended claims. In a preferred form of the invention a first module or apparatus is the basic printer, which is of form and weight to permit a person or persons to lift it and stack it on the other modules. The other modules or apparatus are typically paper drawers or a duplexer for printing on two sides. The printer module includes the drive motor, which drives a gear encircling an elongate housing, having a noncircular central hole. A shaft is partially inserted in the hole and has a cross section keyed to the hole in the housing. The shaft is spring mounted downward. The bottom of the shaft has a vertical face to abut the vertical face of a member on which it is stacked to transmit rotary force. The other modules are similar except they have no drive gear and the top of the elongate member has a vertical face for abutment. The printer is always the top member of a stack. If more than one of the other modules are to be stacked, at least the middle ones are small and light enough to be lifted and stacked manually. The lower modules have one transmission member extending past the general outside surface and an opening in the other side to receive such an extending member, to permit the transmission members of two modules to connect. An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which:- Figure 1 is an isometric view, partially cut away, of the transmission elements of a printer and a lower module, specifically a paper drawer; Figures 2a and 2b illustrate the cross section of a drive transmission shaft and cavity for receiving the same; Figure 3 illustrates the main elements of the transmission train of the printer and one lower module; Figure 4 is an isometric view, partially cut-away showing further details of the lower module; Figure 5 is an isometric view of a thrust bearing; and Figure 6 is a side view of the thrust bearing. Referring to Figure 1, the top elements of a printer system are shown for clarity as only frame plates 1. In fact, the top elements are part of the basic printer module 3. A motor 5 is linked through a bevel gear 7 to drive bevel gear 8. A gear box suitable for driving the driven bevel gear of this apparatus is the subject of our European Patent Application No. EP-A-0 821 186. Gear 8 surrounds and is integral with elongate housing 9, which turns within bushing 11. Compression spring 13 is compressed between the elongate housing 9 and a ledge 15 which encircles shaft 17, to exert downward force on shaft 17. Shaft 17 has an upper cross section as shown in Figure 2b and the lower region of elongate housing 9 has a hole 9a of the same cross section as shown in Figure 2a. These cross sections are noncircular, substantially in the form of a letter D. The upper end of shaft 17 is inserted in hole 9a. Accordingly, shaft 17 is keyed to the housing 9 so that it must rotate with it. Shaft 17 is free to move longitudinally within housing 9 a limited amount. As shown by broken away view in the circled enlargement, shaft 17 has a toothed latch 18 which limits its longitudinal movement. (Latch 18 resiliently yields inward to enable the shaft to be inserted with pressure from the bottom of hole 9a.) A top frame 19 in the upper surface of a separable paper drawer 21 has a tapered conical guide surface 23 which is integral with and converges toward an internal bushing 25 (see Figure 1), in which a lower elongate housing 27 is held. Reference is now made to Figure 3 to show a simplified elevation view of the main elements of a printer module 3 mounted on paper drawer 21. Frame 1 supports gear 7 which drives bevel gear 8. As previously mentioned, gear 8 is integral with elongate housing 9, which has shaft 17 partially inserted in its internal cavity 9a. Shaft 17 is biased downward by spring 13 and is movable upward if forced in that direction by the lower surface of the shaft not finding the lowest surface match with the top of the elongate housing 27 of the paper drawer 21. Reference is now made to Figure 4 for a more detailed description of the elements of the paper drawer 21. Figure 4 illustrates the abutment surfaces at the end of elongate housing 27. These are two vertical surfaces 29a, 29b on opposite sides, which have ramp surfaces 31a, 31b leading to them. This configuration is the same at the bottom ends of shaft 17 and shaft 33 in paper drawer 21, so that upon rotation of the shafts, vertical faces 31a, 31b and their equivalent surfaces on the shafts 17, 33 come into contact for subsequent rotational driving. Elongate housing 27 has a bevel gear 35 integral with it, which meshes with a bevel gear 37 to drive sheet feed roller 39. Spring 41 surrounds shaft 33 and acts between a ledge 45 on shaft 33 and elongate member 27 to permit limited movement of shaft 33 within member 27, all the same as described above for member 9, shaft 17 and spring 13. Figure 3 best illustrates that the bottom end of shaft 33 has vertical surfaces 47a (one shown) and ramps 49a, 49b, like shaft 17. A thrust bearing 51 for supporting housing 27 has extensions 51a, 51b which rest on ledges 19a, 19b of frame 19. This permits sliding for limited automatic adjustment of the location of shaft 33 when shaft 33 is placed on a lower module for power transmission to that lower module. Bearing 51 is shown in more detail in Figures 5 and 6. It supports housing 27 at a location well spaced from bevel gear 35. Extensions 51a and 51b have curved bottom surfaces 51a' (Fig. 6, the bottom surface of 51b being identical). Bearing 51 has an integral, T-shaped neck 52. The curvature of the bottom surfaces of 51a and 51b is at a curvature defined by an arc with its centre at the level of bevel gear 35, directly above the extensions 51a and 51b (illustrated as R in Fig. 3). This allows bearing 51 to roll on ledges 19a, 19b and the elongate housing 27 to rotate around the center of bevel gear 35. This has a minimal effect on the meshing of the gears 35 and 37, yet allows housing 27 to move enough to take up variations in the next module, since the gear 35 is close to the pivot point and therefore moves less than housing 27. The T-shaped neck 52 of the bearing 51 fits between posts 19c, 19d of the frame to allow the bearing to move horizontally a limited amount, but to prevent it from turning. Since the stacked units such as tray 21 may be significantly offset or not perfectly matched, some free movement as provided by bearing 51 is necessary. Since bearing 51 is a separate piece, it can be economically fabricated from wear-resistant material. The primary frame material may be chosen for strength. Elongate housing 27 and guide surface 23 extend above the general outline of frame 19 and are surrounded by an outer wall 53 (shown with the left side broken away in Figure 4). Similarly, the bottom of frame 19 has an opening 19e (again shown by break away in Figure 4) surrounded by a inner, curved wall 54. Opening 19e will receive outer wall 53 of a lower module, thereby permitting modules having similar structure to be stacked with the shaft 33 of one engaging the elongate housing 27 of the other. In operation the modules are simply picked up by an operator and stacked vertically. The printer 3 is always on top. During a sheet feed operation, motor 5 is started and kept running. As shaft 17 turns, its ramp surfaces (identical to 49a, 49b, Fig. 3) move smoothly under pressure from spring 13 on the ramp surfaces 31a, 31b of elongate member 27 until the abutments surfaces of shaft 17 (identical to 47a) meet abutment surfaces 29a, 29b of elongate member 27 to then transmit rotation from the top module 3 to the lower module 21. Timing and picking of paper are by other mechanisms forming no part of this invention. Several modules basically the same in power transmission to module 21 may be stacked, with power transmitted from the top of printer 3 through each module in the same manner as described.

Claims: Printing system apparatus including, for power transmission: an elongate housing (27) having along the longitudinal axis of said housing a cavity (9a) ; a gear integral (35) with said housing with its axis concentric with said longitudinal axis of said housing; a shaft (33) partially inserted in said cavity; a resilient member (41) mounted between said shaft and said elongate housing to push said shaft longitudinally away from said housing, and an abutment surface (47) on the end of said shaft away from said housing, characterised in that the apparatus further comprises: a bearing (51) supporting said elongate housing at a position spaced from said gear, said bearing having extensions (51a,51b) on opposite sides which rest on a frame of said apparatus, said extensions having curved bottoms (51a') to permit limited rotation of said housing generally around a pivot point located at said gear, said bearing being free for such limited movement. Apparatus as claimed in claim 1, wherein said cavity (9a) is of non-circular cross section and located at one end of said housing (27). Apparatus as claimed in claim 2, further comprising a bushing (25) mounted in said apparatus and in which said elongate housing (27) is mounted. Apparatus as claimed in claim 3, the apparatus having along the longitudinal axis of the housing (27) an abutment surface (29) at the opposite end to said cavity (9a) and a tapered guide surface (23) at the opposite end, converging around said bushing. Apparatus as claimed in claim 4, in which said opposite end of said elongate housing has a ramp surface (31) leading to said abutment surface (29). Apparatus as claimed in claim 4 or 5, which is of form and weight to permit manual lifting and positioning of said apparatus. Apparatus as claimed in any of claims 4 to 6, in which the end of said shaft away from said elongate housing has an abutment surface (47) generally parallel to said longitudinal axis for engaging an abutment surface (29) of a power transmission mechanism in a second apparatus on which said apparatus may be placed. Apparatus as claimed in any of claims 4 to 7, in which said resilient member is a coil spring (41) encircling said shaft (33) and mounted between said elongate housing (27) and a ledge (45) on said shaft. Apparatus as claimed in any preceding claim, said elongate housing extending above the general top surface (19) of said apparatus said shaft being within the general outline of said apparatus and the general outline of said apparatus having an opening (19e) to receive the part of said elongate housing extending above the general top surface so that the shaft of one such apparatus can engage the elongate housing of another such apparatus. Apparatus as claimed in any preceding claim and mounted to a printing system apparatus of a form and weight to permit manual lifting and positioning of said apparatus, including, for power transmission: an elongate housing (9) having along the longitudinal axis of said housing a cavity (9a) of noncircular cross section, a gear (8) integral with said housing with its axis concentric with said longitudinal axis of said housing, a motor (5) to drive said gear, a shaft (17) partially inserted in said cavity and having a cross section where said shaft is inserted in said cavity for keying said shaft for rotation with said housing while said shaft is free to move a limited amount longitudinally within said cavity, a resilient member (13) mounted between said shaft and said elongate housing to push said shaft longitudinally away from said housing, and an abutment surface (47), generally parallel to said longitudinal axis, on the end of said shaft away from said housing, for abutment against an abutment surface (29) of a second printing system apparatus to transmit power from said motor through said shaft to said second printing system apparatus. Apparatus as claimed in claim 10, in which said end of said shaft (17) has a ramp surface (49) leading to said abutment surface (47). Apparatus as claimed in claim 10 or 11, wherein said resilient member (13) is a coil spring encircling said shaft (17) and mounted between said elongate housing (9) and a ledge (15) on said shaft. A stacked printing system comprising a first apparatus as claimed in any of claims 10 to 12 mounted on a third apparatus as claimed in any of claims 4 to 9 with said abutment surface (47) of said shaft (17) of the first apparatus positioned to engage said abutment surface (29) of said elongate housing (27) of the third apparatus for transmission of power from said motor (5) of the first apparatus to the third apparatus. A stacked printing system comprising a system as claimed in claim 13 with said third apparatus mounted on a second apparatus as claimed in-any of claims 4 to 9 with said abutment surface (47) of said third apparatus positioned to engage said abutment surface (29) of said elongate housing (27) of said second apparatus for transmission of power from said motor (5) of the first apparatus to said third apparatus and from said third apparatus to said second apparatus.

Inventors: BAHRAMI HASSAN, MLEJNEK DANIEL GEORGE, PORTIG HARALD, SEMAN RICHARD ANDREW JR, BAHRAMI, HASSAN, MLEJNEK, DANIEL GEORGE, PORTIG, HARALD, SEMAN, RICHARD ANDREW, JR.
Applicants: LEXMARK INT INC, LEXMARK INTERNATIONAL, INC.
Application year: 1997
Main classification: B41F13
IPC codes: B41J23, B41F13, F16D1