The invention relates to an arrangement for locking a nut on a pin bolt, the nut being arranged to abut against an end face of a bearing collar arranged on a conical portion of the pin bolt, and the nut being in engagement with a first threaded portion of the pin bolt.

Preventing a nut from loosening from its abutment against an element which is held together with an adjacent element by means of said nut and an associated threaded bolt or the like has been sought to be solved by means of a great number of arrangements, among other things by increasing the friction between the threads of the nut and of the bolt. The most obvious prior art is forming the nut as a clamp nut; that is to say, at least parts of an outward-facing end portion of the nut rest more tightly against the threads of the bolt than the threads of the nut do, typically by the nut being provided with an oval collar portion. A so-called nylock nut includes an integrated synthetic ring, with a smaller diameter than the threads of the nut, at its outward- facing end portion. Further known arrangements for locking a nut include the use of a locking element which engages with both the nut and the bolt, for example a locking pin which has been passed through a radial bore in the bolt and engages with recesses in a so-called castellated nut, or a locking disc which engages, in a rotation-preventing manner, with an axial groove in the bolt, for example, and is bent into abutment against the polygonal jacket of the nut.

Especially to secure large bolt connections, for example pin bolts of the kind described in NO302053 Bl, it is impractical to use the arrangements that are described above, as the locking means will be difficult to manufacture or heavy to handle.

It is also known to use a co-called counter-nut, that is to say a second nut being screwed into abutment against a first nut. The counter-nut may have a dimension identical to or smaller than the main nut.

WO9320359A1 discloses a bolt for a swivel link, in which a conical sleeve has been pushed into abutment against a bore and against the conical portion of the bolt by means of a nut, which engages with a threaded end portion of the bolt and with an internal groove of the conical sleeve. A locking plate rests against an end face of the sleeve and is fixed by means of a screw arranged radially offset from the periphery of the sleeve, to prevent the sleeve from rotating and the nut from loosening.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.

The object is achieved through the features that are specified in the description below and in the claims that follow.

The invention provides an arrangement for locking a nut on a bolt by a nut-locking element being arranged to releasably engage with the bolt and the nut that is in engagement with a first threaded portion of the bolt, especially on a pin bolt on which a nut is resting against a bearing collar arranged on a conical portion of the pin bolt, in order thereby to expand the bearing collar into abutment against a bore in an element in which the pin bolt is to be held. The bolt includes a second threaded portion, which is concentric with the first threaded portion and has a thread pitch, which is smaller than the thread pitch of the first threaded portion of the bolt. The second thread portion may be formed as internal threads in a bore in an end portion of the bolt or as external threads on a stepped end portion of the bolt. The nut-locking element includes a friction portion which, when resting against a portion of the nut, prevents the nut from rotating independently of the nut-locking element. The friction portion may be formed as an externally cylindrical portion surrounding a conical section of the end portion of the bolt and being expandable, by the abutment of an internal conical portion against the conical section of the bolt end portion, into abutment against a portion of the threads of the nut. Alternatively, the friction portion may be formed on a flanged end portion of the nut-locking element, wherein the friction portion is brought to rest against an external portion of the nut. In this embodiment, the friction portion of the nut-locking element may be formed as an annular collar end face lying in a plane arranged perpendicularly to the centre axis of the nut, or as a conical inward- facing surface. The friction portion may possibly be formed of a circular transition portion between the end face of the collar and an inward-facing collar face, which, in this embodiment variant, may be cylindrical. Correspondingly, the external abutment portion of the nut may be an annular end-portion surface lying in a plane arranged perpendicularly to the centre axis of the nut or being formed as an outward-facing conical surface of the end portion of the nut, or, possibly, the abutment portion consists of a circular transition portion between the end-portion surface of the nut and the outward- facing conical surface, possibly between the end-portion surface of the nut and an external cylinder face of the nut. The nut-locking element includes a coupling portion arranged in the outward-facing end portion of the nut-locking element for releasable connection to a tool, for example in the form of an external, polygonal end portion or a centric recess with a polygonal cross section.

The invention is defined by the independent claim. The dependent claims define advantageous embodiments of the invention.

The invention relates, more specifically, to an arrangement for locking a nut on a pin bolt, the nut being arranged to abut against an end face of a bearing collar arranged on a conical portion of the pin bolt, and the nut being in engagement with a first threaded portion of the pin bolt, characterized by a nut-locking element being provided with a threaded portion arranged to engage with a second threaded portion of the pin bolt, the second threaded portion being concentric with and having a smaller thread pitch than the first threaded portion, and the nut-locking element being provided with a friction portion arranged to rest supportingly against the nut.

The second threaded portion may be arranged externally on a stepped end portion of the bolt and may be separated from the first threaded portion by a conical portion, and the nut-locking element may be provided with an internal conical surface which is arranged to rest against the conical portion, and may be encircled by a cylindrical face which, by radial expansion, is arranged to rest supportingly against an encircling part of the nut.

The second threaded portion may alternatively be arranged in a centric, axial recess in the end portion of the bolt, the threaded portion of the nut-locking element may be arranged externally on a pin provided with a flanged end portion, and the friction portion may be arranged near the periphery of the flanged end portion.

In this alternative, the friction portion may be formed as an annular collar end face lying in a plane that is perpendicular to the centre axis of the nut, possibly as an internal conical surface of the flanged end portion, possibly as an edge between two faces of the flanged end portion.

A coupling portion, which is arranged to receive a spanner, may be formed as an end portion with an externally polygonal cross section, or as an end portion with an internally polygonal recess. The nut may be provided with an abutment portion for receiving the friction portion of the nut-locking element, the abutment portion being formed as a stepped or conical end portion of the nut.

In what follows, examples of preferred embodiment are described, which are visualized in the accompanying drawings, in which :

Figure 1 shows an axial section through a portion of a bolt with a nut that is locked by means of a first embodiment of a nut-locking element;

Figure 2 shows an axial section through a portion of a bolt with a nut which is locked by means of a second embodiment of the nut-locking element;

Figure 3 shows an axial section through a portion of a bolt with a nut which is locked by means of a further variant of the second embodiment of the nut-locking element;

Figure 4 shows an axial section through a portion of a bolt with a nut which is locked by means of yet another variant of the second embodiment of the nut-locking element; and

Figure 5 shows an axial section through a portion of a bolt with a nut which is locked by means of still another variant of the second embodiment of the nut-locking element.

In the figures, the reference numeral 1 indicates a pin bolt provided with a conical portion 11 arranged to receive a radially expandable bearing collar 2 of a kind known per se for mounting in a supporting bore 51 in an element 5. The mounting of the bearing collar 2 is done by it being displaced axially onto the conical portion 11 by a nut 3, which, with a threaded portion 31 of the nut 3, engages with a first threaded portion 121 of an end portion 12 of the pin bolt 1, bearing against an end portion 21 of the bearing collar 2.

A nut-locking element 4 is arranged on the end portion 12 of the pin bolt 1. The nut- locking element 4 engages with a second threaded portion 122 of the end portion 12. The second threaded portion 122 has a smaller thread pitch than the first threaded portion 121. When the nut-locking element 4 has been screwed into abutment against the nut 3, the difference in thread pitch will prevent the nut 3 and the nut-locking element 4 from rotating together in such a way that the abutment of the nut 3 against the bearing collar 2 ceases to exist by the nut 3 loosening . The connection between the nut 3 and the nut-locking element 4 may be provided in various ways.

Reference is first made to figure 1, in which a first exemplary embodiment is shown. Here, the end portion 12 of the pin bolt 1 is stepped, and the second threaded portion 122 is arranged outside the first threaded portion 121 and with a smaller diameter than the first threaded portion 121. A conical transition portion 123 is formed between the first and second threaded portions 121, 122 and provides an abutment surface for an internal conical surface 412 of the nut-locking element 4. An external cylinder face 412a encircling the internal conical surface 412 forms a friction portion 41 which, by radial expansion, is arranged to rest against an encircling portion of the threaded portion 31 of the nut 3. The expansion is made possible by the nut-locking element 4 being formed from an elastic material and possibly by one or more splits directed axially (not shown) cutting through the friction portion 41.

In this embodiment, adjacent to the friction portion 41, the nut-locking element 4 is provided with a coupling portion 42 encircling a threaded portion 43 arranged to engage with the threaded portion 122 of the stepped part of the end portion 12. In this embodiment, the coupling portion 42 is provided with an externally polygonal end portion 421.

Reference is now made to figures 2, 3, 4 and 5, in which variants of a second embodiment of the invention are shown. Common to the variants of this embodiment are that the second threaded portion 122 of the end portion 12 of the pin bolt 1 is formed internally in a centric recess 124, and that the nut-locking element 4 includes a flanged, circular end portion 411 which, when the nut 3 is being locked, is resting against a circular abutment portion 32 of the nut 3. In this embodiment, the threaded portion 43 of the nut-locking element 4 is provided on a cylindrical pin 44 arranged centrically.

In figure 2, the flanged end portion 411 of the nut-locking element 4 is provided with a friction portion 41 formed as an internal conical surface 411b which rests against a circular edge 32d of an outward-facing stepped abutment portion 32 on the end of the nut 3.

In figure 3, the flanged end portion 411 of the nut-locking element 4 is provided with a friction portion 41 formed as an annular collar end face 411a which lies in a plane perpendicular to the centre axis of the nut-locking element 4 and which abuts against an end face 32a of the outward-facing stepped abutment portion 32 of the nut 3. In figure 4, the flanged end portion 411 of the nut-locking element 4 is provided with a friction portion 41 formed of an edge 411d between an annular collar end face 411a and an internal cylinder face 411c, the edge 411d resting against an external conical abutment surface 32b of the outward-facing stepped abutment portion 32 of the nut 3.

In figure 5, the flanged end portion 411 of the nut-locking element 4 is provided with a friction portion 41 formed as an internal conical surface 411b resting against an external conical abutment surface 32b of the outward-facing stepped abutment portion 32 of the nut 3.

The nut-locking elements 4 according to the embodiments shown in figures 2, 3 and 4 are provided with a coupling portion 42 for a spanner (not shown), shown here as an externally polygonal end portion 421. In figure 5, the coupling portion 42 is formed as an internally polygonal end-portion recess 422 arranged centrically in the nut-locking element 4.

When the bearing collar 2 has been fixedly mounted in the supporting bore 51 by means of the nut 3, and the nut-locking element 4 has been fixedly mounted against the nut 3, the smaller thread pitch of the second threaded portion 122 of the pin bolt 1 and the corresponding threaded portion 43 of the nut-locking element 4 will ensure that the nut-locking element 4 is further tightened against the nut 3 if the nut 3 has a tendency to become screwed away from its abutment against the bearing collar 2. Thereby the invention has provided simple and effective securing of the abutment of the nut 3 against the bearing collar.

It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art may construct many alternative embodiments without departing from the scope of the attached claims. In the claims, reference numbers in brackets are not to be regarded as restrictive. The use of the verb "to comprise" and its different forms does not exclude the presence of elements or steps that are not mentioned in the claims. The indefinite article "a" or "an" before an element does not exclude the presence of several such elements.

The fact that some features are indicated in mutually different dependent claims does not indicate that a combination of these features cannot be used with advantage.