Paper pressing arrangement for typewriters

Abstract: The paper pressing arrangement 11 comprises a paper guide plate (14) for guiding a sheet of paper (16) around a platen roller 12 towards the typing line. The paper guide plate 14 comprises two conveyor modules (17 and 18) each of which supports three paper pressing rollers (66) and is provided with a pivot element 22, 23 projecting from the barycentre of the triangle joining the mid-­ points of the three rollers. A control mechanism (32), in an operative position, transmits by means of a rocker lever 33 pivotally connected to the pivot elements 22 and 23 the action of a spring (44) to urge the conveyor modules (17 and 18) against the roller (12). The control mechanism (32) comprises a lever (47) for positioning the two conveyor modules (17 and 18) in an inoperative position to permit insertion of the sheet of paper (16). Each conveyor module (17,18) defines a first axis (67) for rotation of two front paper pressing rollers (69 and 71, 72 and 73) and a second axis (68) spaced from the first axis (67) for rotation of a rear roller (74, 76) disposed intermediate each pair front rollers (69 and 71; 72 and 73). The paper pressing rollers (66) have a rotary shaft (79) of plastics material and a covering of rubber. Each conveyor module (17 and 18) comprises, for each paper pressing roller (66) two depressed seats (77 and 78) for accommodating the shaft (79) without force, and a through slot (83) positioned between the two depressed seats (77 and 78). The through slot (83) is of a width which is slightly less than the diameter of the paper pressing roller (66) so that, in mounting, the rubber covering on each roller has to be slightly forced into the slot (83) to permit the ends (81,82) of the shaft (79) to reach the seats 77 and 78. Each paper pressing roller (66) then remains restrained between the two seats (77 and 78) and the respective slot (83) and will be capable of slight axial and radial movements until it is positioned against the platen roller (12).

Description: The present invention relates to a paper pressing arrangement for typewriters having a platen roller, the paper pressing arrangement including a paper guide plate for guiding a sheet of paper towards the typing line, said plate including at least two conveyor modules, paper pressing rollers carried by said conveyor modules for holding the sheet of paper against the roller, and a control mechanism having spring means for urging the conveyor modules into an operative position in which said conveyor modules are held against the platen roller parallel thereto. Other paper-pressing arrangements of this general type is to be found in document DD245401 A1. This document also describes an arrangement in which there is provided a paper guide plate having paper-pressing rollers and a mechanism for urging the conveyor modules carrying the paper-pressing rollers into an operative position in which the conveyor modules are held against the platen roller and parallel thereto. Italian Patent No. 1 159 359 discloses a paper pressing arrangement of this type, in which each plate is pivotally mounted on a control shaft of a control mechanism, parallel to the axis of the roller and capable of preventing transverse movements of the plate with respect to the roller. A leaf spring of the control mechanism co-operates with a cam on the plate to hold the paper pressing rollers pressed against the platen roller. The control shaft comprises opening cams co-operable with the leaf springs to disengage the leaf springs from the respective cams and permit radial displacement with respect to the roller of the respective plate, so that the paper pressing rollers are disengaged from the roller to permit a sheet of paper to be introduced. This paper pressing arrangement is reliable, functional and well suited to being mounted on typewriters of standard type. However the structure thereof is excessively expensive for portable typewriters in the medium-low range, in which costs must be kept as low as possible. The technical problem that the present invention seeks to solve is therefore that of providing a paper pressing arrangement which is simple, easy to use and of very moderate cost. The paper pressing arrangement according to the invention is characterised in that its control mechanism comprises a pivot element on each conveyor module disposed in a substantially barycentric position with respect to the paper pressing rollers, a rocker lever having two ends pivotally connected to the pivot elements of two conveyor modules and a central pivot between its two ends; and an actuating member connected to said spring means and capable of co-operating with the central pivot of the rocker lever so as to hold the two conveyor modules in said operative position, uniformly distribute the action of the spring means to the paper pressing rollers. A preferred embodiment of the invention is set forth in the following description which is given by way of non-limiting example and with reference to the accompanying drawings in which: Figure 1 is a side view of part of a paper pressing arrangement according to the invention, Figure 2 is a partial side view showing some details from the arrangement illustrated in Figure 1, Figure 3 is a partial longitudinal view of the arrangement shown in Figure 1 on a different scale from Figures 1 and 2, and Figure 4 is a partial plan view in section taken along line IV-IV in Figure 1. Referring to Figures 1, 2 and 3, a paper pressing arrangement according to the invention is generally identified by reference numeral 11 and is applied to a typewriter having a conventional platen roller 12 rotatable with a shaft 13 on a frame structure 10 of the machine in a manner which is known per se but not described and illustrated in order not to complicate the present description. The paper pressing arrangement 11 comprises a paper guide plate indicated at 14 for guiding a sheet of paper 16 around the roller 12 towards the typing line. The paper guide plate 14 comprises two conveyor modules 17 and 18 which are positioned below the platen roller 12 and which are identical to each other and in which each conveyor module 17,18 comprises a main body formed by a thin wall of substantially semicylindrical shape, connected at one end to a flat wall 19,21. Each conveyor module 17 and 18 has a pivot element as indicated at 22 and 23, projecting from a central position on the opposite side with respect to the platen roller 12. The pivot element comprises in particular a pin 29, 31 which is rigidly fixed between two limbs 24 and 26, and 27 and 28 respectively, which are fixed with respect to the modules 17 and 18. A control mechanism indicated at 32 comprises a rocker lever 33 having two ends 34 and 36 which are pivotally connected by means of a press-type coupling to the pins 29 and 31 of the two conveyor modules 17 and 18. The rocker lever 33 comprises a central limb 37 between the two ends 34 and 36, having the free end of semicylindrical shape capable of being accommodated in a semicylindrical seat 38 of an actuating member 39 of the control mechanism 32. The actuating member 39 comprises a lever guided by a slot 40 in the frame structure 10 and is pivoted at an intermediate point thereof on a fixed pin 41 and has a first end 42 which defines the seat 38 and a second end 43 which carries the forces of spring means 44 of the control mechanism 32. The spring means 44 comprise a coil spring which is tensioned between the first end 43 and the frame structure 10 and which, by means of the actuating lever 39, loads the rocker lever 33 to hold the two conveyor modules 17 and 18 in an operative position in which the two conveyor modules 17 and 18 are pressed against the platen roller 12 parallel thereto. A fixed fork 45 guides and prevents transverse movements of the rocker lever 33 and the end 42 of the actuating lever 39. The control mechanism 32 comprises an opening assembly indicated at 46 for displacing the two conveyor modules 17 and 18 from the operative position in which the two conveyor modules 17 and 18 are against the platen roller 12, as shown in continuous lines in Figure 1, to an inoperative position in which the two conveyor modules 17 and 18 are spaced from the platen roller 12 to permit insertion of the sheet of paper 16, as indicated by the dash-dotted lines in Figure 1. The opening assembly 46 (Figures 1, 2 and 3) comprises an opening lever 47 which is pivotally mounted on the shaft 13 of the platen roller 12 and a link 48 connected between the opening lever 47 and the actuating lever 39 of the control mechanism 32. The link 48 has one end 49 with a semicylindrical seat 51 capable of engaging with a pin 52 on the opening lever 47 and another end 53 with a suitably shaped slot 54 for accommodating with clearance the second end 43 of the actuating lever 39. The opening lever 47 is rotatable on the shaft 13 from a rest position shown in solid line in Figure 2 to an operative position shown in dash-dotted lines by way of an intermediate neutral position. In its rest position the lever 47 does not act on the lever 39 and the spring 44 holds the two conveyor modules 17 and 18 in the operative position against the platen roller 12. In its operative position the lever 47, by way of the link 48, acts on the end 43 of the lever 39, against the force of the spring 44, holding the two conveyor modules 17 and 18 in the inoperative position in which they are spaced from the platen roller 12 while the spring 44 holds the opening lever 47 arrested against a fixed stop 56, as described in greater detail hereinafter. Each conveyor module 17 and 18 is normally supported and arrested against a respective fixed guide or support 57 (Figures 1, 2, 3 and 4) when it is in the inoperative position and comprises on the surface 58 which faces towards the platen roller 12, a series of mutually parallel sliding ribs 59 disposed in planes perpendicular to the platen roller 12 to limit the area of contact between the sheet of paper 16 and the respective conveyor modules 17 and 18. Each conveyor module 17 and 18 further comprises two forks 61, 62 and 63, 64 respectively which project on the side of the pivot element 22, 23 and which are parallel to each other and to the pivot element 22, 23. The two conveyor modules 17 and 18 being substantially identical, they are interchangeable with each other and each is formed by a single piece of plastics material. The two forks 61 and 62, 63 and 64 are positioned at the ends of the respective conveyor modules 17 and 18 to receive with play the rocker lever 33 and, when the conveyor module 17 and 18 is in the inoperative position, also the actuating lever 39 and also for accommodating the respective fixed guide 57 which guides and prevents transverse movements of the respective conveyor module 17, 18 with respect to the roller 12. Each conveyor module 17 and 18 rotatably carries a group of paper pressing rollers which are indicated generally at 66 to hold the sheet of paper 16 clinging to the platen roller 12. The paper pressing rollers 66 are disposed along two axes 67 and 68 which are spaced from each other and which are parallel to the platen roller 12. The first axis 67 is positioned at a front angular position which is more closely adjacent to the typing line while the second axis is positioned at a rear angular position which is further away from the typing line. The paper pressing rollers 66 of each conveyor module 17 and 18 comprise two first rollers 69 and 71, 72 and 73 disposed along the first axis 67 and spaced from each other, and a second roller 74, 76 disposed along the second axis 68 at an intermediate position between the position of the first rollers 69 and 71, and 72 and 73 respectively. Therefore the conveyor module 17 rotatably carries two front rollers 69 and 71 and a rear roller 74 and the conveyor module 18 rotatably carries two front rollers 72 and 73 and a rear roller 76. Each conveyor module 17 and 18 has for each roller 69, 71, 72, 73, 74 and 76, guide support means comprising two seats 77 and 78 which are depressed with respect to the surface 58 facing towards the platen roller 12. The two depressed seats 77 and 78 are positioned along the two front and rear axes 67 and 68 and each seat 77, 78 is of a semicylindrical shape open upwardly towards the platen roller 12 and defining the axis 67 or 68. Each paper pressing roller 69, 71, 72, 73, 74 and 76 is of elastomeric material, mounted on a shaft 79 of plastics material and having the ends 81 and 82 projecting from the roller, being capable of being accommodated with play in the respective seats 77 and 78. Finally each conveyor module 17 and 18 is provided, for each paper pressing roller 69, 71, 72, 73, 74 and 76, with a through slot 83 positioned between the two seats 77 and 78 and being of a length which is slightly less than the external diameter of the respective paper pressing roller 69, 71, 72, 73, 74 and 76 in such a way that, in the mounting seats, each paper pressing roller 69, 71, 72,73, 74 and 76 has to be slightly forced into the respective slot 83 in order subsequently to be able to engage with the ends 81 and 82 of the shaft 79 in the respective seats 77 and 78. Each paper pressing roller 69, 71, 72, 73, 74 and 76, when fitted to the respective conveyor module 17,18 is thus restrained with respect to the module but can move with slight axial and radial movements with respect to the two seats 77 and 78 and the respective slot 83. That permits the two conveyor modules 17 and 18 to be positioned in the operative position in which the paper pressing rollers 69, 71, 72, 73, 74 and 76 are against the external surface of the platen roller 12. The six paper pressing rollers 69, 71, 72, 73, 74 and 76 are substantially identical to each other and can be mounted on each conveyor module 17, 18 either at the front or at the rear. The mode of operation of the paper pressing arrangement 11 is as follows: In the rest position of the opening lever 47, the tension of the spring 44 of the control mechanism 32, by means of the actuating lever 39, holds the rocker lever 33 in a raised position and the two conveyor modules 17 and 18 are in the operative positions in which the paper pressing rollers 69, 71, 72, 73, 74 and 76 are against the external surface of the platen roller 12. When the sheet of paper 16 is to be inserted, the operator manually rotates the opening lever 47 in the anti-clockwise direction from the rest position to the operative position. Due to the effect of that selection, the link 48 raises the end 43 of the actuating lever 39 against the force of the spring 44 until the neutral point of the spring 44 on the lever 47 is reached, and the lever 39 is rotated in the anti-clockwise direction and moves its end 42 downwardly. That is followed by downward movement due to the force of gravity of the rocker lever 33 and the two conveyor modules 17 and 18 with a radial motion with respect to the platen roller 12. In that way the front paper pressing rollers 69, 71, 72 and 73 and the rear paper pressing rollers 74 and 76 are disengaged from the platen roller 12 until the two conveyor modules 17 and 18 stop against the fixed support 57 in the inoperative position. When the neutral position has been exceeded, the operator can release the lever 47 and the spring 44 will in fact urge the opening lever 47 by means of an anti-clockwise rotary movement into its operative position in which it is arrested against the fixed stop 56. The operator can now introduce the sheet of paper 16 and move the opening lever 47 from the operative position to the rest position. When the neutral position has been exceeded, the tension of the spring 44 now causes the actuating lever 39 to rotate in the clockwise direction, whereby the rocker lever 33 is raised. The two conveyor modules 17 and 18 are again moved into the operative position in such a way that the front paper pressing rollers 69, 71, 72 and 73 and the rear paper pressing rollers 74 and 76 can hold the sheet of paper 16 against the platen roller 12. The machine is thus again ready for typing. The action of the spring 44, by means of the actuating lever 39 and the rocker lever 33 which is pivotally connected by the ends 34 and 36 to the pins 29 and 31 of the pivot elements 22 and 23, is converted into a pressure force which is distributed in equal amounts to the two conveyor modules 17 and 18 and from those is applied to the platen roller 12, equally distributed among the front paper pressing rollers 69, 71 and 72, 73 respectively and the rear paper pressing rollers 74 and 76. For that purpose the pivot element 23 is substantially aligned along a line E perpendicular to the axis 13 of the roller 12, with the barycentre D of the triangle which connects centres A, B and C of the respective front paper pressing rollers 69, 71, 72 and 73 and the rear paper pressing rollers 74 and 76, as shown in dash-dotted lines in Figure 4. In particular the centres A and B are on the front axis 67 and the centre C is on the rear axis 68, as shown by the dash-dotted line, and the axis E in Figure 1 is substantially perpendicular to the plane IV-IV joining the points A, B and C and on which the barycentre D is disposed. With that structure the pressure force is applied to a barycentric position between the paper pressing rollers. The fact that each conveyor module 17 and 18 has only three paper pressing rollers, two front rollers 69 and 71 and 72 and 73 respectively, and a rear roller 74, 76 respectively, ensures uniform distribution of the pressure, even in the event of slight misalignments in respect of the two depressed seats 77 and 78 with respect to the theoretical axes 67 and 68. It will be appreciated that the above-described paper pressing arrangement 11 may be the subject of various modifications and additions of parts without departing from the scope of the present invention.

Claims: A paper pressing arrangement for typewriters having a platen roller (12), the paper pressing arrangement including a paper guide plate (14) for guiding a sheet of paper (16) towards the typing line, said plate (14′) includingatleast two conveyor modules (17,18), paper pressing rollers (66) carried by said conveyor modules (17,18) for holding the sheet of paper (16) against the roller (12) and a control mechanism (32) having spring means (44) for urging the conveyor modules (17,18) into an operative position in which said conveyor modules (17,18) are held against the platen roller (12) parallel thereto, characterised in that said control mechanism (32) comprises: a pivot element (22,23) for each conveyor module (17,18) disposed in a substantially barycentric position with respect to the paper pressing rollers (66); a rocker lever (33) having its two ends pivotally connected to the pivot elements (22,23) of the two conveyor modules (17,18) and a central pivot (37) between its two ends, and an actuating member (39) connected to the spring means (44) and capable of co-operating with the central pivot (37) of the rocker lever (33) so as to hold the two conveyor modules (17,18) in said operative position and uniformly distribute the action of the spring means (44) to the paper pressing rollers (66). A paper pressing arrangement according to claim 1 characterised in that the actuating member (39) comprises a lever pivoted on a fixed pin (41) and actuated by the spring means (44). A paper pressing arrangement according to claim 2 characterised in that the central pivot (37) of the rocker lever (33) comprises a semicylindrical surface capable of being accommodated in a corresponding seat (38) defined in a first end of the actuating lever (39), and that said spring means (44) comprise a spring connected to a second end of said actuating lever (39). A paper pressing arrangement according to claim 3 characterised in that each conveyor module (17,18) is positioned beneath the platen roller (12) and is of a substantially semicylindrical shape, said pivot element (22,23) is disposed between two limbs (24,26,27,28) projecting from a central portion of the conveyor module (17,18), on the opposite side thereof to said platen roller, (12) and wherein said pivot element (22,23) is pivotally coupled to one of the two ends of said rocker lever (33) and is substantially aligned with the barycentre with respect to a line perpendicular to the axis of said platen roller (12) which passes through said barycentre of a triangle which connects the centres of the paper pressing rollers (66). A paper pressing arrangement according to claim 1 characterised in that said control mechanism (32) further comprises an opening assembly (46) comprising an opening lever (47) for moving the two conveyor modules (17,18) from the operative position through a neutral position of the spring means (44) on said opening lever (47) to an inoperative position in which the two conveyor modules (17,18) are spaced from the platen roller (12) to permit the insertion of a sheet of paper (16). A paper pressing arrangement according to claims 3 and 5 characterised in that the opening lever (47) is pivoted on the shaft (13) of the platen roller (12) and the opening assembly (46) comprises a link (48) disposed between said opening lever (47) and said actuating lever (39) and wherein said opening lever (47) is movable from a reset position in which the spring means (44) holds said two conveyor modules (17,18) in the operative position to an operative position in which said conveyor modules (17,18) are held in the inoperative position and the spring means (44) holds said opening lever (47) arrested against a fixed stop (56). A paper pressing arrangement according to claim 6 characterised in that said link (48) has a first end (49) with a seat (51) capable of engaging with a pin (52) of the opening lever (47) and a second end (53) with a slot (54) for accommodating with play the second end (43) of said actuating lever (39). A paper pressing arrangement according to any preceding claim characterised in that said pivot element (22,23) comprises a notched pin (29,31) having a portion of reduced cross-section and in which the ends of said rocker lever (33) each comprise a circular seat (34,36) connectable to said notched pin (29,31) and provided with an opening for said portion of reduced cross-section to pass therethrough. A paper pressing arrangement according to any preceding claim characterised by a fixed fork (45) for guiding movement of said rocker lever (33) and said actuating lever (39). A paper pressing arrangement according to any preceding claim characterised in that each conveyor module (17,18) comprises two forks (61,62,63,64) one on each side of projecting the pivot element (22,23), aligned with each other and with said pivot element, and positioned adjacent the ends of the conveyor module (17,18), and wherein a first fork (62,63) of each conveyor module (17,18) is capable of accommodating with play said rocker lever (33) and, when each conveyor module (17,18) is in the inoperative position, also said actuating member (39). A paper pressing arrangement according to claims 3 and 4, 9 and 10 characterised in that a second fork (61,64) of each conveyor module (17,18) is co-operable with a fixed pin (57) to define a plane of movement of said modules (17,18), passing through the axis of the platen roller (12). A paper pressing arrangement according to claim 11 characterised in that the two conveyor modules (17,18) are substantially identical and interchangeable with each other. A paper pressing arrangement according to any preceding claim, characterised in that said conveyor modules (17,18) are of plastics material and each paper pressing roller (66) comprises a shaft (79) and an clastomeric covering and wherein each conveyor module comprises for each roller (66) two seats (77,78) which are depressed with respect to a surface facing the platen roller (12) and which are capable of accommodating with play said shafts through slot (83) positioned between the depressed seats (77,78), the slots being of a width which is slightly less than the diameter of the paper pressing roller, (66) in such a way that in mounting in the seats (77,78) each roller has to be slightly forced into the respective slot (83), deforming the elastomeric covering to permit the ends (81,82) of the shaft to engage in the respective depressed seats (77,78). A paper pressing arrangement for typewriters having a platen roller (12), a paper guide plate (14) for guiding a sheet of paper (16) towards the typing line and paper pressing rollers (66) for holding the sheet of paper (16) against the platen roller (12); said paper guide plate (14) comprises conveyor modules (17,18) disposed beneath the platen roller (12), and each conveyor module (17,18) carries a group of said paper pressing rollers (66) which are mounted for rotation and disposed along two axes (67, 68) spaced from each other and parallel to said platen roller (12); and wherein a control mechanism (32) urges each conveyor module toward the platen roller (12) with a given pressure force, characterised in that said group of rollers (66) comprises two single rollers (69, 71; 72, 73) which are spaced from each other and positioned along one (67) of said two axes and a single roller (74; 76) positioned on said other axis (68); the single roller and each one of the two single rollers include a respective centre point (A, B and C) lying on the one axis (67) and the other axis (68), respectively and defining a geometrical triangle (ABC) with a given barycentre (D); the control mechanism comprises an actuating member defining a pressure force perpendicular to the axis of said platen; and there is provided a pivot element (22,23) of the conveyor module for receiving said pressure force, wherein said pivot element projects from the conveyor module such that said pressure force is directed along an axis (E) including said barycentre (D) to apply the pressure force to a barycentric position between the paper pressing rollers (69, 71, 72, 73; 74; 76). A paper pressing arrangement according to claim 14, characterised in that the one (67) of said two axes is disposed forwardly of the roller, adjacent the typing line, and the other axis is disposed beneath the roller, remote from the typing line. A paper pressing arrangement according to claim 14 or 15, characterised in that each conveyor module (17,18) comprises support and guide means (77,78) positioned along said two axes (67,68) to support and guide said two single rollers (69, 71; 72,73) and said single roller (74; 76) and that said support and guide means comprises for each roller two seats (77,78) which are depressed with respect to the surface facing the platen roller (12). A paper pressing arrangement according to claim 15, characerised in that each paper pressing roller is mounted on a shaft (79) of plastic material having the ends (81,82) projecting from the roller, wherein said ends are capable of being accommodated with play in said two recessed seats (77, 78), and wherein each recessed seat is of a shape which is open towards said platen roller (12).

Inventors: GILLIO CLAUDIO, GILLIO, CLAUDIO
Applicants: OLIVETTI & CO SPA, ING. C. OLIVETTI & C., S.P.A.
Application year: 1990
Main classification: B41J13
IPC codes: B41J13