WO1990002892A1

WO1990002892A1 - Power transmitting device with a driving shaft and a driven shaft

Info

Publication number: WO1990002892A1
Application number: PCT/DK1989/000202
Authority: WO
Inventors: Alfred Susanka
Original assignee: Mercante Systems A/S
Priority date: 1988-09-02
Filing date: 1989-09-01
Publication date: 1990-03-22
Also published as: DK490688A; DK490688D0; EP0454673A1

Abstract

A driving shaft (2) is through a drive wheel (5) and a transmission (6) connected with a transmission wheel (7) for a driven shaft (8). The transmission wheel (7) is floatingly journalled in a supporting member (4) and includes a hub (9) having a central boring accommodating a coupling means for releasably connecting the driven shaft and the hub (9) and which at the side of the hub (9) facing away from the member (4) merges into a guide surface for centering the hub in relation to the shaft (8). The driven shaft is in its axial direction displaceable between a position in which the shaft is pulled clear of the hub (9) and a position in which the shaft end is inserted into the coupling means. Due to the floating bearing of the transmission wheel and the self-centering of the hub in relation to the shaft (8) when inserted into the hub the shaft may be journalled at comparatively coarse tolerances.

Description

Power transmitting device with a driving shaft and a driven shaft.

The invention relates to a device for power transmission from a driving shaft to a driven shaft in which the shafts are substantially mutually parallel and in which a transmission wheel associated with the driven shaft is connected with the driving shaft through a chain or belt drive and is floatingly carried in a supporting member, the hub of the wheel having a central bore for receiving the driven shaft.

Power transmissions of this type are disclosed in US patent No. 2 537 120 in which the hub of the transmission wheel is formed as a spherical member journalled in a cup which to a certain degree is laterally displaceable in associated slide guides. Due to this floating bearing with limited movability the transmission system may absorb a limited degree of permanent obliquity between the shafts. The power transmission is intended for permanent mounting on the shafts. The central bore is quadrangular or has any other non-circular form intended to be positioned on the associated gudgeon having a corresponding shape.

If said shaft is installed in a sub-unit that is exchangeable for repair or overhaul, it is frequently time-consuming to dismount or mount the shaft in relation to the chain or belt drive, particularly if the space around the drive is confined.

Electrophotographic printers which are for instance disclosed in DK patent No. 151 414 include various driven shafts operated intermittently in order to feed sheet printing material through the individual processing steps. A photo conductor mounted on a shaft, sheet feeding rollers, toner conveying mechanisms or similar rotating members may be involved. When it is desired to drive a number of such shafts mutually inde pendently from the same driving motor, a coupling must be inserted between one or more of the shafts and the common belt or chain drive, said coupling ensuring such a sufficiently quick and accurate cutting-in of the shaft concerned that the pertaining function is effected in exactly timed relation to the movement of the device for transferring a picture to the printing material.

The device according to the invention is characterized in that the central bore has a substantially circular cross-section and continues at the side of the wheel facing the driven shaft into a guide surface for centering the hub in relation to the driven shaft, and in that the hub accommodates a coupling means for releasably connecting the driven shaft with the associated hub.

This provides for obtaining a particularly simple design of the device which allows not only extremely coarse tolerances in the mutual positioning of the shafts when the driven shaft has been introduced into the hub and has aligned the hub but it also allows the driven shaft and/or the hub to be journalled at very coarse tolerances in relation to the supporting member, the shaft and the hub being reciprocally selfcentering when assembled because the gudgeon by the longitudinal displacement towards the hub will primarily engage the guide surface, thereby centering the hub in relation to itself, following which it may be inserted into the central bore and the coupling means. This provides for obtaining simple, easily produced and inexpensive designs of the structures of which the device forms part.

Due to the fact that the central bore has a circular cross-section the shaft and the boss do not need to be in a specific mutually angular position when being assembled, meaning that the axial displacement and the coupling altogether may be effected quite independently of the mutual angular position of the shafts.

The combination of low tolerance requirements, simple design and completely free option re the coupling timing without the need of complicated control systems makes the device according to the invention very appropriate for use in electrophotographic printers or similar apparatuses.

In a preferred embodiment of the invention the coupling means is a radial bearing with an outer bearing race secured and centered in relation to the hub and with rolling bodies in the form of rollers or needles capable of catching the driven shaft to move it in the driving direction but which permits the shaft to be freely rotatable in the opposite direction. This free wheeling clutch is particularly advantageous when two sets of shafts are to be rotated intermittently in opposite directions of rotation via a common transmission, in that the one set of shafts may be inserted into the associated hub or hubs having the one direction of rotation as drive direction while the other set of shafts is driven in the opposite direction so that the rotational movement of the shafts is solely time- controlled by the common driving motor. Moreover, the free wheeling clutch is largely noiseless upon cuttingin and cutting-out which is particularly advantageous when the device is applied in apparatuses, such as printers and sorting devices normally positioned in noise-sensitive environments.

A further embodiment of the invention for use in connection with electrophotographic printers comprising independent sub-units with a respective driven shaft and in which the bearing of the driving shaft and the supporting member of the driven shaft are fixedly mounted in relation to the framework of the apparatus is characterized in that the driven shaft with a view to cutting-in and cutting-out is displaceable in its longitudinal direction between a position in which the shaft end is inserted into the coupling means, and a position in which the shaft is pulled clear of the hub. This makes it possible to drive a plurality of sub-units by a single drive, the sub-units being released from the driving shaft for periods of a working cycle during which the actual units are inactive.

In case the driven shaft is mounted in a subunit which with a view to inspection and upkeep must be releasable from the surrounding apparatus, the device according to the invention may advantageously be designed so that the hub extends through a hole in the supporting member and has a substantially smaller outer diameter at its portion passing through the member than the diameter of the hole therein and that the driven shaft is longitudinally displaceable in guides fixed in relation to the supporting member. This entails the simplest possible bedding of transmission wheels and hubs. When the apparatus is stopped and the sub-unit pulled out, the hub will be pulled laterally by the transmission belt to a rest position in abutment on the edge of the hole of the supporting member. When the sub-unit is then pushed into the operative position the driven shaft will centre the hub as described above and carry it in a "floating" position in which the hub passes freely through the supporting member without touching the edge of the hole.

An embodiment of the device according to the invention will be described in more detail in the following with reference to the very schemtical drawings, in which

Fig. 1 is a perspective view of an embodiment of the invention with only one driven shaft,

Fig. 2 is a perspective view on a larger scale of a hub in the device in Fig. 1, Fig. 3 is a longitudinal section on a larger scale through the hub in Fig. 2, and

Fig. 4 is a longitudinal section through a second embodiment of a hub according to the invention.

The drawings only illustrate the parts necessary to understand the invention.

Fig. 1 is an illustration of the drive 1 for power transmission from a driving shaft 2 connected with a drive motor 3 which for instance may be a step motor receiving control signals from a control unit not shown. Shaft 2 is journalled in a supporting member 4 and carries a drive wheel 5 for a transmission 6 shown in dot-and-dash lines and which may for instance be a chain or belt transmission, e.g. a toothed belt. The transmission 6 is in driving connection with a transmission wheel 7 for a driven shaft 8. For the sake of clarity, only a single transmission wheel is shown, but it is obvious that one and the same driving motor 3 may be in connection with a plurality of transmission wheels via one or more chain or belt transmissions.

Transmission wheel 7 is secured on an associated hub 9 "floatingly" journalled in supporting member 4 in such a manner that the hub is allowed to move somewhat in relation to the supporting member in directions transverse of its axis of rotation. As shown in Fig. 2, the hub 9 may principally be passed through member 4 in a hole 10 having a larger diameter than the hub. When shaft 8 is in engagement with the hub, the shaft will centre the hub so that it is freely floating in hole 10 without touching the edge thereof. Embodiments may be provided in which direct contact between the rotating hub and the stationary member 4 is prevented, thereby preventing undesired wear on the hub and the member, respectively. The hub may e.g. be supported in a radial bearing which per se is floatingly carried in member 4. The driven shaft 8 is journalled in a sub-unit not shown in such a manner that the shaft is displaceable in its axial direction between a position in which the shaft extends into a central hole 11 in hub 9, and a position in which the shaft is pulled clear of the hub. It is also possible that shaft 8 is axially secured in a sub-unit that is longitidinally displaceable in slot guides extending parallel to the longitudinal direction of driving shaft 2. The sub-unit may for instance be a sheet feeding unit in an electrophotographic printer the one lateral wall of which may be opened for inspection and overhaul of the individual sub-units driven by the device according to the invention, said device being accommodated in the framework at the lateral wall opposite relative to the openable lateral wall. If malfunction occurs in a sub-unit or the printing material is getting jammed during the feeding, the sub-unit concerned may after opening of the lateral wall be pulled out of the printer, the driven shaft being concurrently pulled clear of hub 9. Upon remounting the sub-unit, shaft 8 will abut on a guide surface 12 in the hub, thereby centering it when being re-inserted into hole 11. Due to the floating carrying of the hub and the self-centering thereof in relation to shaft 8 the sub-unit may be bedded at coarse tolerances in relation to hub 9.

Alternatively, the driven shaft 8 may be axially displaceable in in the sub-unit so that the cutting-in and cutting-out of the shaft may be effected as part of the normal working of the apparatus in which the device is used. Advantage may be taken, on one hand, of the already mentioned low requirements for axial alignment between the shaft and the hub and, on the other hand, of the low-noise cutting-in and cutting-out.

Fig. 2 illustrates the situation immediately before the cutting-in step. Driven shaft 8 is displaced against hub 9 along its axis of rotation 13 which is largely perpendicular to supporting member 4. Due to the loading from transmission 6 hub 9 is shifted and inclined in relation to the shaft so that the symmetrical axis 14 of the hub is warped in relation to axis 13. When the end of shaft 8 hits guide surface 12 that is formed as a frustoconical surface, the symmetrical axis of which is coaxial with axis 14, the guide surface will due to the continuously axial displacement of the shaft centre the hub after the shaft until this shaft is displaced into hole 11.

As it will appear from Fig. 3 in which the hub is illustrated in connection with transmission wheel 7, guide surface 12 merges smoothly into hole 11 leading into a central bore 15 with a larger diameter. Bore 15 accommodates a coupling means in the form of some sort of radial bearing 16 without inner bearing race and with rollers or needles 17 positioned in wedge-shaped recesses and springbiassed for movement towards the axis of rotation and towards the narrow end of the recess so that the needles may be pressed towards the external surface of a shaft inserted into bearing 16 and act as friction bodies which lock the shaft in relation to the bearing by rotation thereof in one direction of rotation but which allows for freewheeling of the shaft by rotation in the opposite direction of rotation. A washer 18 and a subjacent gasket 19 sealing against dust are provided between bearing 16 and the shoulder at the transition into hole 11.

In the illustrated, structurally very simple type of floating journalling of transmission wheel 7 in supporting member 4 the hub is on the side of the member facing away from wheel 7 provided with a flange 20 with a larger diameter than hole 10. In order to limit the tilting movement and the axial move ment of the hub in relation to member 4 when shaft 8 has been pulled clear of the hub, a Seeger circlip 21 is inserted in a groove on the external surface of the hub. The axial and tilting movement of the hub are restricted by circlip 21 and the abutment of flange 20 on member 4.

Member 4 may be composed of more mutually connected parts that are only to be capable of maintaining such a mutual distance between driving wheel 5 and transmission wheel 7 that transmission 6 is sufficiently tight to present the desired transfer of movement from wheel 5 to wheel 7.

Guide surface 12 must further be of such a sufficient extent that shaft 8 always lands on the guide surface irrespectivce of the lateral displacement and inclination of the hub.

Fig. 4 illustrates a second embodiment in which only one hundred is added to the reference numeral for details with the same function as described above. As regards these details reference is made to the preceding description.

The transmission wheel and the hub 109 are manufactured integrally as a unit which may for instance be provided by the processing of a cast blank. Teeth 120 intended to engage with a transmission transferring toothed belt, not shown, are provided on the outside of the hub at the one end, and at the other end an encircling recess is performed, into which a

Seeger circlip 121 is inserted which in the direction to the left of the figure prevents hub 109 from being passed through the hole 110. The movement of the hub to the right of the figure is limited by a stop 122 than may be mounted on the supporting member 104 or may constitute an independent wall in the actual apparatus. A Seeger circlip could alternatively be used as in Fig. 3. In Fig. 4 the hub occupies a position as if the hub was carried on the driven shaft (not shown). The hole 110 has a substantially larger diameter than the outer diameter of the hub so that the hub positioned on the shaft will not touch the supporting member irrespective of whether the shaft extends obliquely with respect to member 104 or is positioned eccentrically in relation to the hole. This makes it possible to produce the members of which the hub and the shaft form part at extremely coarse tolerances; member 104, stop 122 and the shaft supporting unit being for instance produced from punched and bent thin plate assembled by spot welding.

The diameter of the driven shaft is attuned to the free wheeling clutch 116 that is a prefabricated standard unit. The bore 115 may have such a diameter that the free wheeling cluth may just be pressed into the bore but the coupling is prevented from being unintentionally pressed out. Alternatively, the coupling may be secured in the bore by an adhesive or by a Seeger circlip inserted into an annular groove formed in the periphery of the bore.

If the coupling member is formed as a free wheeling clutch there are, as indicated above, two different forms of cutting-out. When the shaft is inserted into the coupling means 116, the cutting-in and cutting-out are rapidly and noiselessly effected in that the hub is made to rotate in one or the other direction of rotation. Longer lasting cutting-outs may be effected in that the shaft is pulled clear of at least the free wheeling clutch 116.

When the driven shaft is mounted in a sub-unit displaceable in the longitudinal direction of the shaft the sub-unit may be provided with longitudinal flanges facing sideways and sliding in U-shaped lateral guides fixed in relation to the supporting menber and extend ing in parallel to the shaft. Such guides are well known from electrophotographic printers and similar apparatuses.

Claims

P A T E N T C L A I M S

1. A device for power transmission from a driving shaft (2) to a driven shaft (8) in which device the shafts are substantially mutually parallel and in which device a transmission wheel (7) associated with the driven shaft is connected with the driving shaft through a chain or belt drive (6) and is floatingly carried in a supporting member (4, 104), the hub (9, 109) of the wheel having a central bore (11, 15; 111, 115) for receiving the driven shaft, characterized in that the central bore (11, 15) has a substantially circular cross-section and continues at the side of the wheel facing the driven shaft (8) into a guide surface (12, 112) for centering the hub in relation to the driven shaft, and in that the hub accommodates a coupling means (16, 116) for releasably connecting the driven shaft (8) with the associated hub (9).

2. A device as claimed in claim 1, characterized in that the guide surface (12, 112) is a frustoconical face.

3. A device as claimed in claim 1 or 2, characterized in that the coupling means is a radial bearing (16, 116) with an outer bearing race secured and centered in relation to the hub (9, 119) and with rolling bodies in the form of rollers or needles (17, 117) capable of catching the driven shaft (8) to move it in the driving direction but which permit the shaft to be freely rotatable in the opposite direction.

4. A device as claimed in any of claims 1 to 3 and used in connection with electrophotographic printers or similar apparatuses comprising independent subunits with a respective driven shaft and in which the bearing of the driving shaft and the supporting member of the driven shaft are fixedly mounted in relation to the framework of the apparatus, characterized in that the driven shaft (8) with a view to cutting-in and cutting-out is displaceable in its longitudinal direction between a position in which the shaft end is inserted into the coupling means (16, 116), and a position in which the shaft is pulled clear of the hub (9, 119).

5. A device as claimed in any of claims 1 to 3, characterized in that the hub extends through a hole (110) in the supporting member (104) and has a substantially smaller outer diameter at its portion passing through the member than the diameter of the hole therein, and in that the driven shaft is longitudinally deplaceable in guides fixed in relation to the supporting member.