The present invention relates to mechanical connection of wear parts to underlying structures and has been created in relation to the connection of ground engaging tools to buckets of earth-moving equipment but could be used to attach a shroud for wear protection to any type of carrier.
Ground engaging tools (GET), for earth-moving equipment, such as those used in mining operations, operate in a highly abrasive environment, are subjected to high impact forces and therefore wear out or become damaged through use. GET, such as teeth used on the front lip or edges of a bucket of the earth moving equipment, therefore require regular replacement.
Traditionally, GET are welded onto the lips of buckets. When the GET come to the end of their useful life, they can be cut from the bucket, and new GET welded in their place.
It will be appreciated that such cutting and re-welding operations are complex, time-consuming and relatively expensive. Further, they must generally be done in a workshop to ensure the cutting off and welding is done correctly, requiring the bucket to be transported away from the earth-moving equipment.
Various mechanical attachment methods have been proposed in an attempt to alleviate these problems. Many of the methods involve the use of bolts and similar fastening devices, inserted within the lip of the bucket. In general, such devices have proved to be of limited use. The insertion of a bolt or similar within a bucket lip can lead to undesirable stress concentrations within the lip, resulting in cracking of the bucket lip. Even where this is avoided, the large forces to which GET are exposed have a tendency to deform connecting bolts, thus making difficult their subsequent extraction using mechanical tools. Indeed, in some cases the deformation can be so severe that the GET must be cut away, completely negating any advantage of mechanical connection.
In response to these issues, the applicant has devised a number of mechanical connection means which overcome these problems. Examples of the applicant's devices are detailed in U.S. Pat. No. 7,219,454, in U.S. Pat. No. 7,472,503 and in U.S. patent application Ser. No. 13/133,213 (also published as International PCT publication number WO 20 0/065990), the contents of all of which are included herein by reference.
These connection means involve the use of a shroud which mounts about a lug or boss on the lip of an excavator bucket; a locking device which locates between the shroud and the boss; and the application of an external compressing force to maintain the relative position of the shroud, locking device and boss.
Although these connection means have proved far less susceptible to deformation than previous mechanical connectors, there have nonetheless been occasions where the connection means have had one or more problems.
Sometimes failure of the GET or connection means can occur when the GET is in use due to a load being applied which is higher than the means can bear. The number of individual components forming the connection means can make fitting/refitting a GET time consuming. Other times, when it is necessary to remove the GET, the connection means is troublesome to undo to release the GET from the bucket, or, even if the connection means is released, the GET does not readily remove from the bucket lip, usually because of dirt and/or deformation of the connection means and/or GET preventing removal.
In response to these challenges, the applicant has devised in WO2014037780A1 a locking assembly for releasably locking a shroud to a carrier by which removal and preferably application of the GET to the carrier of earthmoving equipment is improved.
However, it has been found that large forces and general abuse of the shroud and carrier in use sometimes deform or damage the connection means/locking assembly such that detachment of the shroud is difficult or impossible.
Accordingly, an object of the invention is to provide an improved locking assembly for releasably locking a shroud to a carrier.
According to a first aspect, this object is achieved by a locking assembly as defined in appended claim 1 with alternative embodiments defined in the dependent claims. Specifically, the locking assembly is for releasably locking a shroud to a carrier and comprises a piston and a main body provided with a through central recess for receiving the piston such that the piston is movable back and forth along a longitudinal axis of the recess with an outer end portion of the piston extending outside the recess of the main body. The locking assembly further comprises a bolt provided within the central recess, wherein the bolt comprises a shank and a gripping portion extending through a first end opening of the central recess such that the zo gripping portion is accessible from outside the main body for rotation of the bolt. Also, at least a portion of the shank is provided with a thread engaging a corresponding thread of the piston. The bolt is provided with a first bearing surface facing a corresponding second bearing surface of the main body, wherein the first and second bearing surfaces are configured such that when the bolt is rotated to force the piston out of the central recess, the first bearing surface of the bolt bears against the second bearing surface of the main body thereby preventing movement of the bolt in a first direction along the longitudinal axis. The locking assembly 1 further comprises a retaining means for preventing movement of the bolt in a second direction opposite the first direction. The retaining means is provided in the central recess with an outer surface of the retaining means facing an inner surface of the central recess.
The outer surface of the retaining means is provided with a first recess extending at least partly around the circumference of the retaining means, wherein the inner surface of the central recess is provided with a second recess extending at least partly around the circumference of the inner surface of the main body. The first recess and the second recess jointly define an intermediate space for receiving a plurality of balls distributed about the longitudinal axis such that the balls limit movement of the retaining means in the second direction relative to the main body. The retaining means is either a) integrated with the bolt, or b) provided as a separate part positioned around the shank of the bolt and adapted to limit movement of the bolt relative to the retaining means in the second direction.
The locking assembly is designed to work on the same principles as the prior art locking assembly PA-110/PA-30 shown in
The first recess and the second recess may be shaped and positioned to allow the balls a predetermined amount of axial movement along the longitudinal axis relatively the main body and/or relatively the retaining means, such that the balls are not axially loaded when the first bearing surface touches the second bearing surface.
By so providing for a predetermined amount of axial play, the balls remain substantially axially unloaded such that large forces are absorbed by the first and second bearing surfaces at feeding of the piston out of the main body when locking the shroud to the carrier.
When configured according to alternative b) above, the retaining means and the bolt may be configured to allow a predetermined axial play between the bolt and the retaining means when the first bearing surface touches the second bearing surface. As indicated above, it may be desirable to keep the stress on the retaining means low in order not to damage the retaining means at extension of the locking assembly. Generally, the amount of stress that can be handled by the first and the second bearing surfaces is higher than the stress that the retaining means is able to handle without deforming or being damaged. Hence, a further mechanism for ensuring the main stresses at extension of the locking assembly are kept away from the retaining means is to make the retaining means movable with respect to the bolt and ensure there is an axial play between the bolt 6 and the retaining means 12 when the first bearing surface 9 touches the second bearing surface 10. After the balls have been introduced into the intermediate recess as described above, the amount of axial relative movement between the retaining means and the main body is governed by any play around the balls. However, with the current configuration in which the retaining means is not integrated with the bolt but provided as a separate part, the bolt is freely movable away from the retaining means into the housing until the first bearing surface abuts the second bearing surface. From there, the bolt is again freely movable a predetermined distance outwards of the main body along the longitudinal axis of the main body until some portion of the bolt hits the retaining means. From there, the mechanical interference between the retaining means and the bolt prevents further movement outwards of the bolt such that the bolt can be still used to pull the piston back into the main body upon rotation of the bolt.
The main body or the bolt is provided with a passage connecting the intermediate space to the outside of the locking assembly such that the plurality of balls are movable into the intermediate space through the passage. The passage provides a means for getting the balls into the intermediate space whilst preferably also enabling the balls to be moved out of the intermediate space for disassembly, inspection and maintenance of the locking assembly.
The passage may be provided with a closure means for closing the passage.
The provision of such a closure means ensures the balls are kept in the intermediate space and prevents dust and dirt from entering the intermediate space, thereby improving reliability of the locking assembly.
The main body and the piston may be provided with corresponding guide means configured such that the piston is guided for movement along the longitudinal axis and such that the piston is prevented from co-rotating with the bolt.
The provision of such a guide means prevents the piston from rotating about the longitudinal axis and thus enables a rotation of the bolt to cause the threads to move the piston along the longitudinal axis. Hence, such a configuration enables installation and removal of the shroud without use of a special tool for preventing rotation of the piston.
The guide means may comprise at least one protrusion provided on the piston and extending radially outwards from the piston, wherein the main body is provided with at least one support surface or recess extending parallel to the longitudinal axis, wherein the support surface or recess is configured to guide the protrusion along the longitudinal axis and to prevent rotation of the piston.
The protrusion and the support surface together provide a simple means for preventing rotation of the piston about the longitudinal axis whilst allowing the piston to move back and forth along the longitudinal axis.
According to a second aspect, this object is also achieved by a shroud system comprising a shroud, a locking assembly as described above, and a lug or boss attachable to the carrier to provide a means for the piston of the locking assembly to engage such that the main body moves relative to the lug or boss upon rotation of the bolt.
A locking assembly 1 according to a first embodiment will hereinafter be described with reference to the appended drawings.
As for example shown in
The locking assembly 1 is for releasably locking the shroud 2 to a carrier 3. Mounting of the shroud to the carrier using the locking assembly is illustrated in
The locking assembly 1 comprises a piston 4 and a main body 5 provided with a through central recess for receiving the piston 4 such that the piston 4 is movable back and forth along a longitudinal axis 11 of the central recess with an outer end portion of the piston 4 extending outside the central recess of the main body 5. The locking assembly 1 further comprises a bolt 6 provided within the central recess, wherein the bolt 6 comprises a shank and a gripping portion 7 extending through a first end opening 8 of the central recess such that the gripping portion 7 is accessible from outside the main body 5 for rotation of the bolt 6. At least a portion of the shank is provided with a thread engaging a corresponding thread of the piston 4. Also, the bolt 6 is provided with a first bearing surface 9 facing a corresponding second bearing surface 10 of the main body. The first 9 and second 10 bearing surfaces are configured such that when the bolt 6 is rotated to force the piston 4 out of the central recess, the first bearing surface 9 of the bolt bears against the second bearing surface 10 of the main body 5 thereby forcing the main body in a first direction D1 along the longitudinal axis 11. The locking assembly 1 further comprises a retaining means 12 (see
The retaining means 12 and the bolt 6 are configured to allow a predetermined axial play between the bolt 6 and the retaining means 12 when the first bearing surface 9 touches the second bearing surface 10. The play ensures that the retaining means 12 is not loaded when the locking assembly 1 forces the shroud 2 onto the carrier 3 upon mounting of the shroud 2 to the carrier 3.
The main body 5 or the bolt is provided with a passage 15 connecting the intermediate space 13 to the outside of the locking assembly 1 such that the plurality of balls 14 are movable into the intermediate space 13 through the passage 15 for assembly of the locking assembly 1. After the balls 14 have been inserted into the intermediate space, the passage 15 has been provided with a closure means 18 for preventing balls 14 from leaving the intermediate space 13 through the passage 15. The closure means 18 is shown in
As shown in
Instead of, or in addition to, providing a predetermined axial play between the retaining means 12 and the bolt 6, the first recess and the second recess may alternatively be shaped and positioned to allow the balls 14 a predetermined amount of axial movement along the longitudinal axis 11 relatively the main body 5 and/or relatively the retaining means 12, such that the balls 14 are not axially loaded when the first bearing surface 9 touches the second bearing surface 10.
In an embodiment according to the second aspect, a shroud system is provided, wherein the shroud system comprises the shroud 2, the above described locking assembly 1, and a lug or boss 18 attachable to the carrier 3 to provide a means for the piston 4 of the locking assembly 1 to engage such that the main body 5 moves relative to the lug or boss 18 upon rotation of the bolt 6. The lug or boss 18 is shown in cross-section in
At mounting of the shroud 2 to the carrier 3, the shroud 2 is first moved onto the carrier 3 as shown in
Sometimes it is necessary to remove the shroud 2 for replacement or service. Merely loosening the locking assembly 1 by reducing its length by rotation of its bolt 6 would not release the shroud 2 which is typically held in place by substantial frictional forces. An advantage of the present locking assembly 1 is that it can be used to force the shroud 2 off the carrier 3. The outer portion of the piston 6 engages the lug or boss 18 and the retaining means 12 keeps the bolt 6 inside the main body 5 at rotation of the bolt 6. This enables the locking assembly 1 to force the main body 5 towards the lip of the carrier 3 until the main body 5 eventually forces the shroud 2 outwards as shown in
Plastic, rubber or elastomer covers may be mounted on the shroud for protection of the locking assembly. The provision of such covers lowers the risk of having foreign particles, such as dust and dirt, entering the locking assembly 1 and also protects the gripping portion of the bolt 6 from external abuse. Altogether, this improves lifetime of the locking assembly 1 whilst still being easy to remove such that the gripping portion can be operated for dismounting the shroud 2 from the carrier 3.
Filing Document | Filing Date | Country | Kind |
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PCT/EP2020/055133 | 2/27/2020 | WO |