GB2271153A - Emergency bearing. - Google Patents

Abstract

A machine device comprises a running surface 102 and a rotable component 103 of a given contact diameter to run in contact therewith. The component is rotatable about an axle 104 or bearing, the distance of the axis of which from the running surface is prevented by a protector 105 from falling below a minimum substantially equal to one half of the contact diameter of the rotatable component upon such running contact. The protector connected to said axle or bearing surface is of a size and position that during normal operation it is out of contact with the running surface but will come into contact upon failure of the rotatable component to maintain the minimum contact diameter. The protector is of a material (eg mild steel) which wears preferentially to the material of the running surface (eg hardened steel) in contact therewith. <IMAGE>

Description

i 2271153 MACHINE PROTECTOR This invention relates to a machine protector

of the type which aims to prevent or reduce consequential damage occurring to a machine device following the failure of a running component thereof and to that extent renders the machine device failsafe.

According to the present invention there is provided in a machine device comprising a running surface and a rotatable component of a given contact diameter to run in contact therewith during normal operation of the device, said component being rotatable about an axle or bearing surface, the distance of the axis of which from said running surface is prevented by a protector from falling below a minimum substantially equal to one half of the contact diameter of the rotatable component upon such running contact, the protector connected to said axle or bearing surface being of such size and position that during said normal operation it is always out of contact with the running surface but comes into contact with that surface on failure of said rotatable component to maintain the aforementioned minimum, characterised in that the protector itself is rotatable or fixed relative to the said axle or bearing surface and, at least when fixed, is at least partially comprised of a material which in relative moving frictional contact with the running surface wears preferentially to the material of the running surface in contact therewith.

The running surface may be the surface of a rail or track and the rotatable component may be a wheel or roller or for example the outer race of a composite roller, ball or other bearing assembly.

1 2 In precision machine devices the use of roller, ball or other bearing races arranged to run on guide surfaces is often necessary or desirable to minimise friction and achieve smooth running.

Further, the freedom of choice for a rotatable component for machine devices is sometimes limited by space, weight, cost and other considerations and the need to optimise performance against such considerations can lead to the occasional failure of a rotatable component and consequential serious damage in prior art machine devices.

During operation of prior art machine devices, the hardness of the axle or bearing material can lead to serious damage of the surface in running contact therewith if the axial distance of the wheel or other assembly mounted on the axle falls below the predetermined minimum to cause such contact.

In known machine devices, the running surface will often be of hardened material to resist wear and will often be otherwise of high specification and the cost of production or replacement correspondingly high. Accordingly, it is highly desirable to protect such a running surface which would not only be costly to replace in itself but also costly through excessive machine down-time and loss of machine output during repair. It will be appreciated that damage to the machine device consequential to failure of the rotatable component may also result from misalignment caused by the failure. Accordingly, protectors of this invention may be of such size, shape and position to minimise such misalignments in the event of the component failure and thereby minimise this type of damage to the machine device.

The protector of this invention permits a wider choice of rotatable components and the construction of machines which are adequately proportioned without undue risk of serious machine damage or unacceptable repair down-time.

The protector of this invention may be any device connected directly or indirectly to the axle or bearing surface about which the rotatable component may rotate and may itself be rotatable or be rigidly fixed.

2 3 Connection of the protector to the axle or bearing surface is preferably by way of a releasable fastening such as by bolting, circlip or other known releasable fastening. Such releasable fastening may permit adjustment or replacement of the protector and also servicing or replacement of the rotatable component of the machine device.

It will be appreciated that if the protector gets worn, i.e. due to the axial distance of the rotatable component falling below the predetermined minimum or the protector getting otherwise damaged, the protector may be so designed e.g. in its symmetry, that in such an event a fresh surface of the protector is brought adjacent to the running surface in readiness for a possible future rotatable component failure. Such fresh surface may be so positioned by adjustment of the protector and/or the axle or bearing surface to which it is connected e.g. by provision of releasable fasteners.

The size and shape of the protector is such that it does not interfere with normal running contact between the rotatable component and the running surface and is such that it does not contact the running surface during such normal running.

If the protector is rotatable it may comprise a wheel or bearing race which may be rotatable about an axis coincident with that of the rotatable component or parallel thereto.

If the protector is rigidly fixed it may comprise a plate attached to the axle of the rotatable component.

The protector is preferably dimensioned and positioned adjacent the rotatable component whereby in the event of failure of the rotatable component consequential debris therefrom, is largely retained.

In a machine device wherein the rotatable component rotates about a vertical axis it is preferred that the protector is situated directly above and/or directly below the rotatable component with its major plane at right angles to the axis of rotation of the rotatable component. One or more protectors may be employed for a component. Suitably dimensioned, the protector may serve to prevent 3 4 or reduce release of debris from a failed component but also the ingress of foreign matter with a view to preventing such failure, as well as fulfilling its primary protection function according to this invention.

If the protector is not rotatable it is particularly preferred that at least the area that contacts the running surface on and during failure of its associated rotatable component is comprised of material softer than that of which the running surface is comprised whereby the latter surface is prevented from serious damage from such contact.

It has been found that in a machine device comprising a running surface of hardened steel, a protector comprising a circular mild steel or brass plate rigidly fixed to the axle of the rotatable component is particularly effective. It will be appreciated that depending on external influences such as temperature of operation of the machine device, the choices of materials may not be restricted to metals but may include non-metals such as plastics and rubbers. Plastics may include ptfe and nylon for example.

In so far as at least the fixed protectors of this invention should be at least partially comprised of a material which in relative moving frictional contact with the running surface will wear preferentially, such protectors may be termed "sacrificial protectors". The statement that the protector, at least when fixed, is at least "partially comprised of a material" which in relative moving frictional contact with running surface wears preferentially to the material of the running surface is meant to cover situations where say a disc of e.g. hardened steel having a brass or a polymeric tyre or other such protectors are used and in which only the portion or portions positioned adjacent the running surface (e.g. the tyres) are of the preferentially wearing material.

Protectors according to this invention have been found to be particularly effective and beneficial when employed in transport apparatus and stretching apparatus such as those of the types described in our British Patent Specifications 1371741, 1374574 and

1442113 incorporated herein by reference. Such apparatus may 4 incorporate large numbers of rotatable components running in contact with rail surfaces in the manner of the machine devices with which this invention is concerned. Protectors according to the present invention may be economically and effectively incorporated.

The following specifically described embodiment of this invention is given by way of illuttration only and should not be construed as limiting the scope thereof in any way.

Figure 1 is a drawing of a machine device provided with a machine protector according to this invention.

Figure 2 shows a portion of a web stretching machine as described in our British Patent Specificalton 1442113 incorporating machine devices as shown in Figure 1 to at least some of the rotatable components of which machine protectors such as shown in Figure 1 may be fitted.

is The machine device indicated generally by 101 in Figure 1 comprises a running surface 102 and a rotatable component 103 in running contact therewith. Rotatable component 103 is rotatable about shaft 104 through bearings and a bearing surface thereon (not shown). Fixed to axle 104 is machine protector 105.

Running surface 102 is a rail surface of hardened steel consisting of nitrided steel having a hardness of 1160+5 HRC on which runs component 103 which comprises the outer surface of the race of a ball bearing race assembly mounted on axle 104 via the tapered fitting thereon of the inner race comprising the bearing surface (not shown). The ball bearing race assembly has inner and outer races of hardened steel.

Machine protector 105 comprises a circular disc of mild steel secured to the axle 104 by two counter-sunk bolts 106. A washer between the bearing and the protector provides adequate clearance between the protector and component 103. The protector may be reliably fixed to the axle by alternative known means. Such means are preferably such as to prevent rotation of the disc relative to the axle which can otherwise require the use of additional bearings or incur problems of self-loosening or tightening.

In an example where rotatable component 103 had a diameter (ie 6 contact diameter) of 32 mm a machine protector of diameter 30 mm and thickness 3 mm was found to be very suitable.

If it is required to incorporate a protector on the side of the rotatable component remote from the free axle end for example, it will be appreciated that this may be done through suitably machining the shaft and protector centre to provide cooperating surfaces, including locking or lockable surfaces, if desired, in known manner.

With reference to Figure 2; it will be appreciated that wheels 14, 22a, 22b, 22c in running contact with rail 10 and wheels 11 in running contact with secondary guide means 12, and alternatively on rail 10, comprise rotatable components of machine devices. Further wheels could of course be incorporated to run on such or additional surfaces to form additional machine devices. In one modification for example wheels 19 may be arranged to come into running contact with rail 10 simultaneously with wheels 11.

While protectors of this invention may be fitted for wheels situated in recesses, as are wheels 22a and 22b, through say pins locating holes in the axle ends for example, of greater importance are those wheels subjected to high loads namely 22c, 14 and 11 and those which are particularly exposed such as wheels 19 in the above- mentioned modification.

Accordingly, in the preferred machine at least all the rotatable components of machine devices incorporated and having an exposed side are provided with protectors of this invention particularly as illustrated with reference to Figure 1.

6

Claims (1)

1. Claims: 1. In a machine device comprising a running surface and a

   rotatable component of a given contact diameter to run in contact therewith during normal operation of the device, said component being rotatable about an axle or bearing surface the distance of the axis of which from said running surface is prevented by a protector from falling below a minimum substantially equal to one half of the contact diameter of the rotatable component upon such running contact, the protector connected to said axle or bearing surface being of such size and position that during said normal operation it is always out of contact with the running surface but comes into contact with that surface on failure of said rotatable component to maintain the aforementioned minimum, characterised in that the protector itself is rotatable or fixed relative to the said axle or bearing surface and, at least when fixed, is at least partially comprised of material which in relative moving frictional contact with the running surface wears preferentially to the material of the running surface in contact therewith. 2. A protector as claimed in Claim 1 wherein the running surface of the machine device is the surface of a rail or track.

   3. A protector as claimed in either Claim 1 or Claim 2 wherein the rotatable component of the machine device is a wheel, roller or the outer race of a composite roller, ball or other bearing assembly. 4. A protector as claimed in any one of the previous Claims which is rigidly fixed directly or indirectly to the axle or bearing surface.

   7 8 5. A protector as claimed in any one of the previous Claims comprising a plate situated directly above or directly below the rotatable component with its major plane at right angles to the axis of rotation of the rotatable component.

   6. A protector as claimed in any one of the previous Claims which is dimensioned and positioned to prevent or reduce release of debris from a failed rotatable component. 7. A protector as claimed in any one of the previous Claims wherein the machine device is incorporated in a web stretching apparatus.

   8. A protector as claimed in Claim 7 wherein the running surface comprises hardened steel and the protector is a plate comprising mild steel at least in the area that contacts the running surface on failure of the running component. 9. A protector as claimed in Claim 7 comprising a mild steel disc having a diameter of 30 mm and a thickness of 3 mm and wherein the rotatable component of the machine device has a contact diameter of 32 mm. 10. A protector as claimed in any one of the previous claims positioned on one side of the-rotatable component wherein a second such protector is positioned on the other side of the rotatable component. 11. A protector as claimed in any one of the previous Claims connected to the axle or bearing surface of a rotatable component of a machine device incorporated in a machine wherein all the rotatable components of all the machine devices incorporated in said machine and having an exposed side have a protector as claimed in any one of the previous Claims connected to their respective axle or bearing surface. 12. A protector as claimed in any one of the previous Claims which is releasably connected to the axle or bearing surface. 13. A protector as claimed in any one of the previous Claims which is adjustable in relation to the running surface.