A braking device for the bar supporting the roll of paper or the like in printers

Abstract: A braking device for the bar supporting the roll of paper or the like in printers. The device is applicable to a bar for supporting a roll of paper or other print medium and comprises, arranged at one end of the bar carrying the roll of paper or print medium, a hub (18) with a stainless steel casing which is acted on by at least one pair of braking shoes (6,20) disposed in diametrally opposed positions on the hub and acted on by opposing springs (30,31) in a transverse arrangement whereas, at the opposite end, the bar carrying the print roll is acted on solely by the axial effort of a spring incorporated in the housing of the end of the said bar.

Description: The present invention relates to a device for the permanent braking of a bar for supporting a roll of paper or other print medium used in printers. The application of permanent braking to the bar supporting the roll of the medium which is to receive the printing in printers achieves automatic correction of misalignments of the print medium, constituted by paper or print medium of another type. This eliminates the need to realign the print medium after its initial loading and alignment which are carried out manually at the start of the printing operation. In computer-controlled printers of this type in which the print medium is supplied from the front portion of the machine and in which there are drive means for entraining the medium and passing it through the interior of the printer in order to receive the printing and finally extracting the printing media, devices have previously been disclosed for applying a certain amount of braking to the print medium, particularly by means of an arm which is made of plastics material and which, owing to a spring effect, acts on the braking surface of an element in the form of a hub associated with the bar supporting the roll of paper or the like. In the said known device, the same plastics material is used for the casing body, the arm and the braking surface. However, in the previously-known devices, control of the taughtness was not very precise, which constitutes a disadvantage, particularly in the case of printers which use rolls of considerable dimensions for print media of various types. Moreover, in the previously known designs having braking devices on both ends of the bar, the braking action was more difficult to control and less foreseeable in its effects, for which reason said braking action was somewhat different from one printer to another. At the same time, as the material in contact with the braking hub was of similar characteristics to this latter, this being determined by the fact of being of the same material than that of the oscillating carrying arm, the braking effect was different at the initial stage of rotation of the hub in comparison to the normal or stabilised stage of said rotation. DE 86 06 662.5 U discloses a braking system comprising a braking shoe and a hub coupled at one and of the support bar. A principal object of the present invention is to achieve a uniform braking effect and hence uniform tautness of the print medium for the various phases of the rotation of the bar supporting the roll of paper or similar print medium. Another object of the present invention consists of the disclosure of means for enabling the braking of the bar supporting the roll of paper or the like to be carried out solely from one end of the said bar. Another object of the present invention consists of the achievement of a more favourable coefficient of friction owing to the configuration of the novel braking device. Another additional object of the present invention consists of the provision of a device for braking a bar carrying a roll of paper or the like which is structurally simpler and less expensive than currently-known devices. Objects of the present invention are solved by the features of claim 1. In one aspect, the invention provides for the formation of a braking assembly which can be applied to only one end of the bar carrying the roll of paper or the like, on which end a hub is provided, the hub having a covering casing of a metal, preferably stainless steel acted on by at least a pair of shoes made of synthetic material, disposed opposite one another on respective shoe-holders which are acted on by opposing elastic means, preferably springs in order to bring about a uniform braking effect on the hub coupled to the end of the support bar. The braking shoes are housed in the shoe-holders so as to be movable axially in housings of matching shape of the said shoe-holders, the shoes being retained by means of resilient tabs which may be formed integrally with the shoe-holders and which have axial retaining teeth. Clearly, if desired, more than one pair of shoes, also diametrally opposed, may be provided. In order to achieve better braking, the shoes have respective regions of contact with the hub coupled tc the support bar, these regions being situated close to the ends of the shoe, separated by a recessed region which does not establish contact with the hub. Moreover, by constituting the braking shoes in form of separate elements of a material which does not depend on the material for the carrying arms, it is possible to select the most adequate materials to obtain the desired friction coefficient. In order that the effort from the elastic means, preferably springs, acting on the shoe-holder arm does not impose offset efforts, said elastic means will act on parallel directions, on both sides of the median plane of the shoe- holder arm, in order that the resulting effort be substantially contained on said medium plane avoiding any offsetting of the effort. At the other end, the bar carrying the print roll is acted on solely by the axial effort of a spring incorporated in the housing receiving the end of the bar. For a better understanding, some drawings of a braking device which can be applied to a bar carrying a roll of paper or the like in printers and which incorporates the present invention are appended by way of non-limiting example. Figure 1 shows the general arrangement of the support bar carrying the roll of paper in a printer which incorporates the braking system of the present invention. Figure 2 is a perspective view similar to Figure 1 showing the support arms and the support heads of the support bar with the covers removed. Figure 3 is a front elevational view of the same assembly of the two heads with the bar mounted therein. Figure 4 is a schematic plan view showing the arrangement of one of the arms for supporting the bar carrying the roll and the spring acting axially in the other head. Figure 5 is a front elevational view of the arm corresponding to the head carrying the axial spring. Figure 6 is a view showing the arrangement of the braking shoes. Figure 7 is a cross-section showing the axial fixing of the braking shoes. The present invention is applicable to a copier having a bar 1 which is intended to support the roll of print medium, paper or the like and is coupled between two end heads 2 and 3 which are formed integrally with respective support arms 4 and 5 and are intended to receive the ends of the said bar 1, a braking mechanism being disposed in one of the heads, that is, the head 3 in the embodiment shown, solely an axially acting spring 23 being disposed in the other, opposite head, that is, the head 2. Springs 30 and 31 keep shoes 6 and 7 applied to a hub 18. According to the present invention, at least one pair of braking shoes 6 and 7 made of a semi-resilient synthetic material is disposed in the head 3, the first shoe being incorporated in a pivoting arm 8 pivotable on a bar 9 and having a circular-arc-shaped region 10 which is coupled with a fixed hub or cylindrical body 11 and which has, as a geometric axis, the above-mentioned bar 9. Both the shoe 6 and the shoe 7 are centred purely axially in respective shoe-holders 12 and 13, the specially shaped ends 14 and 15 being housed in respective housings of matching shape in the shoe-holders. The said braking shoes are retained axially by respective tabs 16 and 17 which are formed integrally with the respective shoe holders 12 and 13 at one end and which also have respective teeth for the axial retention of the shoes. Moreover, the shoes have respective central arcuate regions with a smaller radius than that of the hub 18 of the bar 1 to be braked, defining contact regions disposed substantially at the ends in order to bring about the braking effect in two well-defined regions. This characteristic, which is the same for both shoes 6 and 7, has been shown for the shoe 7 with the central portion 19 with a smaller radius of curvature than that of the hub 18 and with the opposite end portions 20 and 21 which exert the braking effect on the periphery of the hub 18 which has a stainless-steel outer covering or casing 29. This arrangement achieves a braking effect directed onto the support bar, the braking effect being exerted at only one of the ends of the bar carrying the roll of print medium, achieving a well controlled friction without noticeable noise, as well as very satisfactory wear characteristics. At the same time, given the construction of the shoe and shoe-holder system, the system can easily be modified to serve other machines with similar characteristics. Moreover, the provision of the braking at only one of the ends of the bar reduces the number of parts of the braking system with a consequent reduction in costs. The head 2, which can be seen with the cap or cover removed in Figure 2 and in an elevational view in Figure 4, has a moulded housing 22 for the opposite end of the bar of the roll of paper to the hub 18, no braking shoes being included at the said end because they are not necessary given the high degree of effectiveness of the braking system of the present invention which permits operation with a single braking system at one end of the bar. However, a spring 23 is incorporated in the said head 2 and acts axially on the end of the bar 1, helping to retain and centre it. In the case of a desk-top embodiment of the printer, it preferably has lower pads for bearing on the desk or location in which the printer is placed. The drawings show the pads 24 and 25 for the arm 4 as well as the pads 26 and 27 for the arm 5. The roll of paper or other print medium is mounted on hubs 32 and 28 coupled close to the ends of the bar 1.

Claims: A braking device for a support bar (1) for supporting a roll of paper or print medium in a printer, comprising a hub (18) coupled at one end of the support bar, at least a pair of braking shoes (6,7) and a biasing means (30,31); wherein the biasing means (30,31) is arranged in use to continuously bias the braking shoes (6,7) against the hub (18) with a substantially constant force and at a substantially constant radial position relative to the hub (18) and the hub (18) and the shoes (6,7) are respectively composed of different materials, the materials being a metal and a synthetic material chosen to provide in use a substantially uniform tautness of the print medium for the various phases of rotation of the bar (18). A braking device according to claim 1, in which merely one end of the support bar for the printing media receives a substantial braking action. Braking device according to claim 1 or claim 2, in which the pair of braking shoes (6, 7) are diametrically opposed in relation to the hub of the support bar to provide a braking action on said hub. A braking device according to any preceding claims in which the braking shoes of the pair are removably assembled on respective shoe holders (12, 13). A braking device according to any preceding claim, in which the hub is made out of stainless steel. A braking device according to any preceding claim, in which the second end of the support bar for the printing media roll receives the action of an elastic means (23) acting in the axial direction of said support bar. A braking device according to claim 6, in which the elastic means acting axially on the support bar for the printing media roll is an axial spring. A braking device according to claim 4 or anyone of claims 5 to 7 when dependent thereon, in which the biasing means biases the braking shoes substantially towards each other, substantially along the diameter of the hub. A braking device according to any preceding claim, in which the biasing means comprises one or more springs. A braking device according to anyone of claims 4 to 9 dependent thereon, characterized in that the braking shoes are mounted coaxially in housings of matching shape in the shoe-holders, and are retained by means of resilient tabs (16, 17) which act on the front ends of the respective shoes by means of corresponding retaining teeth. A braking device according to any preceding claims characterized in that the braking shoes are made of a semi-resilient synthetic material. A braking device according to any preceding claim 4, characterized in that the braking shoes have respective regions of contact (20, 21) with the hub, the contact regions being situated close to the ends of theshoe and separated by a recessed region (19) in the shoe which does not contact the hub. A braking device according to claim 1, characterized in that one of the shoe-holders is formed in a pivoting arm (8) acted on by the biasing means.

Inventors: BRUGUE JOAQUIM, CANO EMILIO, BRUGUE, JOAQUIM, CANO, EMILIO
Applicants: HEWLETT PACKARD CO, HEWLETT-PACKARD COMPANY
Application year: 1997
Main classification: B65H23
IPC codes: F16D65, F16D59, F16D49, B65H23