GB2480643A

GB2480643A - A structure including a tension rod

Info

Publication number: GB2480643A
Application number: GB201008780A
Authority: GB
Inventors: Terence William Mair; Carl Francis Watts
Original assignee: T A Savery and Co Ltd
Current assignee: T A Savery and Co Ltd
Priority date: 2010-05-26
Filing date: 2010-05-26
Publication date: 2011-11-30
Anticipated expiration: 2030-05-26
Also published as: GB201008780D0; GB2480643B

Abstract

The structure (10) includes at least one elongate, rotatable tension rod with a head (22) and is captive relative to the structure (10). A mechanism for preventing undesirable rotation of the rod includes a locking plate (38) that is secured relative to the structure (10) and has formed therein or thereon at least one locking plate formation (39), and the or each head (22) and a said locking plate formation (39) are connected by a key member (34) that is connected non-rotatively to the head (22) and the locking plate formation (39). The key member (34) has a hexagonal formation to seat in a like recess in the rod head (22) and a circular end to receive the plate (38), the formation (39) being able to contact and deform the transition zone of the key member (34) to prevent movement. There is a circular array of tension rods coupling two concentric cylinders of the structure which is used to couple two railway vehicles, the tension rods acting to absorb impact forces during vehicle coupling.

Description

A STRUCTURE INCLUDING A TENSION ROD

The invention relates to a structure including at least one tension rod.

Many structures exist in engineering in which a tension or tie rod extends between two rigid parts, typically but not necessarily inside a hollow interior, for the purpose of transferring strain-inducing loads.

Usually such a tension rod is an elongate, solid cylinder made of a metal such as a steel and formed with a screw thread at one end. At an opposite end the tension rod includes a screw head that engages part of a structure to or from which a load is to be transferred.

The end of the tension rod including the screw thread is screwed into another part of the structure and the tightening torque adjusted in order to achieve a desired load-transferring characteristic in the structure.

A known problem in the use of tension rods of the kind described above is that the loads they transfer tend to cause unscrewing of the thread. This reduces the tension in the rods with the result that their ability effectively to transfer loads as intended diminishes, sometimes dangerously.

A particular example of this effect arises in the case of a coupler used to couple railway vehicles together to form trains.

A known coupler design includes a pair of hollow cylinders one, smaller one of which is of lesser external diameter than the interior diameter of the other, larger cylinder such that one end of the former is received inside one end of the latter. Two non-adjacent ends of the cylinders are secured together inside the larger one by way of (in the prior art) a single, relatively large diameter tension rod extending centrally.

At the external ends of the resulting structure the coupler is shaped so that it may be linked to coupling parts in turn attached to the railway vehicles.

The objective of the internal features of this design acting in concert with the cylindrical shapes of the main parts is to create a coupler that under normal circumstances rigidly interconnects an adjacent pair of railway vehicles, with the tension rod assisting the cylinders to transfer the loads that are created. When however a high load arises that exceeds a threshold determined by the design of the coupler the structure deforms in an essentially controlled manner so as to absorb the energy in question in a predictable fashion. Such high loads can result from uncontrolled impacts involving the vehicles.

Clearly it is important to the correct functioning of the coupler for any torque applied to the tension rod when assembling it into the structure to be correctly maintained so that the coupler performs in the manner expected over a long period, notwithstanding the usage duty of the coupler. If however the aforementioned tendency of tension rod to unscrew causes the torque to alter from its pre-set value the coupler may not deform as intended and may indeed become positively dangerous in use.

It is an aim of the invention to overcome or at least ameliorate one or more disadvantages of known structures, especially but not exclusively railway vehicle couplers, as set out above.

According to the invention in a broad aspect there is provided a structure including at least one elongate, rotatable tension rod and an anti-rotation mechanism therefor, the or each tension rod including a head and being captive relative to the structure, the anti-rotation mechanism including a locking plate that is secured relative to the structure and has formed therein or thereon at least one locking plate formation, and the or each head and a said locking plate formation being connected by a key member that is connected non-rotatively to the head and the locking plate formation.

In a preferred embodiment of the invention the key member engages the material of the locking plate formation so as to cause rotation-inhibiting deformation of the key member and/or the locking plate on rotation of the tension rod.

Preferably the locking plate formation is or includes a recess in which the key member is non-rotatively received.

Advantageously the use of a key member, that is distinct from the tension rod, and a locking plate permits an assembly technique of a structure including tension rods of using the sockets of the tension rods to achieve a desired torque in the rods, and then locking them in position using the sockets and locking plate so that rotation will not occur and the desired torque thereby is maintained.

Preferably the key member engages the material of the locking plate so as to cause rotation-inhibiting deformation of the key member and/or the locking plate on rotation of the tension rod or rods.

Such deformation advantageously may be achieved by making the material of one of the key member and the locking plate softer than the other, for example by manufacturing one of the aforesaid components from mild steel and the other from a more highly alloyed steel.

The deformation is strongly desirable since it causes the key member and the locking plate to bind together and thereby prevent any unscrewing rotation, of the rods, other than the least amount.

Conveniently the socket defines a polygonal recess in the tension rod and the key member received therein is of complementary exterior shape to the polygonal recess.

In a particularly preferred embodiment the key member in the vicinity that is, in use, received in the socket is of hexagonal cross-section. Such a shape is easy to manufacture and also easy to insert into the socket during assembly of the structure.

In a preferred embodiment of the invention the or each tension rod includes a screw thread that is threadedly engaged in a respective bore in the structure, the socket being a recess of hexagonal cross-section and being capable in the absence of the key member of receiving a hexagonal tool for tightening and loosening of the screw thread.

The foregoing features render the structure of the invention straightforward to assemble and adjust since the hexagonal tool may readily be attached to a torque wrench or a similar device for the purpose of assuring that tightening of the or each tension rod takes place to the desired extent.

Conveniently the screw thread extends at one end of the tension rod and the tension rod recess is formed at an opposite end thereof.

These features render the preferred embodiment of the invention suitable for use as a railway vehicle coupler. However in other embodiments of the invention variations are possible, including but not limited to forming the screw thread part-way along the shank of the tension rod.

Preferably the key member is at a first end of polygonal external shape and at a second end of circular external shape of a diameter less than that of a circle inscribing the polygonal shape, the polygonal shape and the circular shape blending into one another along the length of the exterior of the key member.

A key member of this kind may be manufactured using straightforward machining techniques and yet is very effective at providing the binding effect mentioned. This is because the portion at one end of the key member of circular shape may easily be received in a circular locking plate recess, into the side wall of which the apices of the hexagonal shape may bind on securing of the locking plate relative to the structure. This in turn causes the material of the locking plate recess side wall in each case to engage the polygonal portion of the associated key member and thereby lock it against rotation.

In a particularly preferred embodiment of the invention the structure is constituted as a coupler having first and second hollow cylinders that are joined together by way of one or more of the tension rods, the first cylinder being open at a first end and receiving therein a closed end of the second cylinder so as to define a single centre axis of the cylinders, the or each tension rod connecting the said closed end and a second part of the first cylinder remote therefrom and the or each bore being formed in the said closed end.

It is also preferable that the internal diameter of the first cylinder at the first end is greater than its internal diameter at the second part so as to cause deformation of the structure on the compressive load it experiences exceeding a threshold value.

The foregoing features render the structure of the invention highly suitable for use as a railway vehicle coupler in which the tension rods resist tensile loads and engagement between the cylinders resists compressive loads unless the latter exceed the threshold value (in which case controlled deformation of the structure occurs so as to absorb the energy involved).

However as desired the structure may be configured to serve other purposes than coupling railway vehicles together.

Preferably the structure includes a plurality of the tension rods arranged in a circular pattern that is concentric with the cylinders.

This arrangement means that the load-transferring effect of the tension rods is distributed evenly among a number of them constituting the circular pattern. This in turn means that a high tensile load level may be accommodated without the requirement that would arise in the case of a coupler having a single, central tension rod, to torque the rod to a high level. On the contrary, the presence of multiple rods means that the tightening of the tension rods into the bores in order to pre-Joad the coupler may be achieved without any requirement for expensive manufacturing equipment that would be needed in order to load the rod in a single-rod design.

Further in this regard, conveniently the circular pattern additionally includes a central tension rod defining an axis that coincides with centre axis of the cylinders.

This feature assists in creating an even load distribution that does not rely on a requirement to apply a high torque to any individual tension rod.

Optionally the second part of the first cylinder is or includes an opening having received therein the locking plate.

Furthermore optionally the locking plate is a circular disc having formed therein a pattern of circular recesses corresponding to the tension rod pattern.

The foregoing features render the structure of the invention easy to assemble reliably.

In a practical embodiment of the invention preferably the first cylinder includes at least one rod guide plate spanning the interior of the first cylinder and having formed therein one or more through-going apertures (a) defining a pattern corresponding to the tension rod pattern and (b) respectively having a said tension rod extending therethrough.

The presence of at least one guide plate assures the correct spacing of the rods and moreover limits the ability of the rods to bow when the structure is compressed.

In embodiments of the invention preferably includes first and second rod guide plates secured respectively at the open end of the first cylinder adjacent the closed end of the second cylinder, and at the end of the first cylinder opposite thereto. More particularly, the second rod guide plate at the end of the first cylinder that is remote from the closed end of the second cylinder preferably includes formed therein a recess for receiving the locking plate.

The foregoing features provide for a reliable device.

Preferably the locking plate is fastened to the second rod guide plate. Such fastening may be achieved for example through the use of threaded screws that are received in an adjacent guide plate thereby providing a robust, secure construction.

The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

There now follows a description of preferred embodiments of the invention, by way of non-limiting example, with reference being made to the accompanying drawings in which: Figure 1 is a side elevational view of a structure, according to the invention, in the form of a railway coupler; Figures 2a and 2c respectively are end elevational views of the Figure 1 coupler taken from each end, and Figure 2b is a longitudinally cross-sectioned view of the same; Figure 3 is a perspective view of part of the Figure 1 coupler showing in exploded form certain steps in the process of assembling it; Figure 4 is a longitudinally cross-sectioned view of the Figure 3 components, showing their relationship in more detail; and Figure 5 is an enlargement of part of the Figure 2c view, further illustrating the interrelationship between the parts visible in Figure 4.

Referring to the drawings a structure that in the preferred embodiment shown is a railway vehicle coupler 10 includes a plurality of elongate tension rods 11 within a hollow interior 14 defined by a first hollow cylinder 12 that effectively is closed off by a closed, first end 19 of second hollow cylinder 13 made of a rigid material such as one or more steels or other alloys.

In the embodiment illustrated seven rods 11 are provided six of which are arranged in a hexagonal pattern as indicated by the pattern of holed 17 formed in a rigid (typically metal) closing plate 18 of a first end 19 of second cylinder 13. The seventh rod 11 occupies a position that is equidistant from the other six rods 11 and therefore is concentric with a longitudinal centre line 21 of the structure 10. Closing plate 18 is firmly fastened inside the otherwise open end 19.

Other patterns and numbers of the rods 11 are possible within the scope of the invention.

It is however preferred that the rod pattern includes a circular arrangement of the rods (of which the hexagonal pattern shown is an example, the rods lying on a constant diameter "pitch circle") since this assists in evenly distributing the forces to be transmitted by the coupler 10.

The rods 11 are retained captive inside the hollow interior by reason of being threaded at one end as signified by numeral 16. The threads 16 are received in the bores 17 in closing plate 18, which bores are formed with threads of complementary profile to the threads 16. Consequently the rods 11 may on assembly of the coupler 10 be screwed into the closing plate 18. The significance of this aspect of the invention is explained hereinbelow.

Each of the rods 11 passes through an 24 aperture in a first rod guide plate 23, spanning the interior 14, that is secured inside the interior 14 of cylinder 12.

Guide plate 23 is formed from a rigid material, such as a metal, as a tapered plug having formed in it a pattern of the through-going apertures 24 that corresponds to and is aligned with the bores 17 formed in closing plate 18. The rods 11 therefore pass directly through the first guide plate and are a sliding fit therein.

Further features of the first guide plate 23 are described hereinbelow.

At the end opposite to the threads 16 each tension rod 11 is formed including a screw head 22.

As illustrated most clearly in Figure 3, the screw heads 22 are circular and are of enlarged diameter compared with the remainder of the rods 11. The heads lie on the exterior side of a rigid second guide plate 26 that is visible in Figure 2b.

Second guide plate 26 spans and closes off the otherwise open end of first cylinder 12 that is remote from second cylinder 13.

Second guide plate 26 is formed in the manner of a bung a spigot 27 of which fits snugly inside the end 28 of first cylinder 12 and a circular flange 29 of which overlies and engages the end 31 of the wall from which cylinder 12 is formed. The second guide plate 26 includes a pattern of through-going bores in alignment with the rod pattern such that the rods extend through the second guide plate from one side to the other.

In consequence of this arrangement tightening of the rods 11 by screwing their threads 16 into the bores 17 causes the second guide plate to be driven firmly into the end 28 of first cylinder 12.

Such tightening of the rods 11, which in practice resemble elongate bolts in the embodiment shown, also draws the end 19 of second cylinder 13 into the interior 14 of first cylinder 12.

This causes second cylinder 13 to engage the side of first guide plate 23 that is closest to the exterior of first cylinder 12.

As is visible in Figure 2, first guide plate 23 tapers between a relatively wide section 23a adjacent second cylinder 13 and a relatively narrow, essentially constant diameter section 23b. The sections 23a and 23b are interconnected by a smoothly tapering portion 23c.

The wall of first cylinder 12 in the vicinity of first guide plate 23 is tapered in an essentially complementary manner to that described above such that the guide plate "nests" against the interior wall of the first cylinder 12. The purpose of this is to assist in providing uniform deformation of the structure, when required, in a manner described below.

Since the second cylinder 13 as described engages the first guide plate the action of screwing the rods 11 into the bores 17 draws the second cylinder tightly into engagement with the first guide plate such that the two cylinders 12, 13 effectively are rigidly joined together on assembly of the structure.

Over a short length adjacent end 19 the walls of the cylinders 12, 13 overlap with one another and are mutually spaced by way of a sealing arrangement 32 that also serves as a movement guide guiding movement of the second cylinder 13 inside the first cylinder 12 in the event of the controlled deformation occurring.

As a result of the aforementioned aspects of the coupler 10 following its assembly the rods are pre-tensioned so as to give rise to a particular compressive failure characteristic as determined principally by the presence of the first guide plate 23 and the tapered shape of the wall of first cylinder 12. A description follows of the nature of this failure characteristic.

The preferred coupler illustrated is used for joining railway vehicles such as carriages or wagons together in a load-transferring manner. Therefore it must be very strong in tension since any tensile failure of such a coupler could have disastrous consequences.

On the other hand the failure performance of the coupler in compression is different and is designed to meet certain design criteria, as follows: Up to a certain threshold force value the coupler must be rigid and must transfer compressive loads effectively. Once the threshold force value, corresponding to an unacceptable level magnitude of impulse representing a collision or other undesirable event, is exceeded however the coupler must deform in a way that results in dissipation of energy. The deformation ideally should occur without rupturing of the structure, so that it remains essentially integral during the compression process.

This is achieved by reason of, during absorption of such impact, etc., energy the first guide plate 23 being driven under a force transferred by the cylinders more deeply inside the interior 14 of the first cylinder 12, causing the tapered portion of its wall to extend, by reason of stretching of the metal from which it is formed, along the cylinder 12 towards the end 28. The deformation of the metal of the wall dissipates the energy of the impulse, etc. The fact that the components employed are circular in transverse cross-section means that such dissipation takes place uniformly (or essentially uniformly) about the circumference of the structure 10.

In order to provide the desired compression characteristics as explained the tension rods 11 are pre-tensioned during assembly of the coupler 10. Also as stated however the rods 11 during normal use tend to loosen such that the benefits pre-tensioning might become lost without any visible change in the outward appearance of the coupler. Since this could result in failure of the coupler to perform as required in an emergency (impact) situation it therefore is very important to counteract the loosening tendency of the rods 11.

This is achieved by anti-rotation features of the coupler 10 as described in the remainder

of this specification.

The heads 22 of the rods 11 are each formed in the preferred embodiment illustrated including a respective socket 33 that as shown is hexagonal and extends inwardly into the material of the head 22 away from its free end. Other polygonal shapes for the sockets are possible, but the hexagon shape is preferred.

The sockets 33 are sized and shaped so as to be suitable for receipt therein during assembly of the coupler 10 of a hexagon (or other polygon) wrench for the purpose of screwing the tension rods 11 into the bores 17 as described above.

The rods may be tightened in sequence to a predetermined torque level corresponding to a desired degree of pre-load. Figure 3 schematically shows the rods 11 after such tightening has taken place. As explained, the use of multiple rods 11 means that no single one of them needs to be tightened to an extent that would require special equipment.

A respective locking key member 34 thereafter is inserted into each socket 33.

At one end 36 each of the key members 34 is hexagonal in cross-section and dimensioned to fit snugly, by way of manual pressure, into an associated socket 33. The process of insertion of the key members 34 is shown partly completed in Figure 3.

When inserted as described each of the key members protrudes outwardly beyond the extent of the heads 22. The key members 34 therefore protrude from the sockets in a pattern corresponding to that of the rods 11.

At its protruding end each of the key members tapers smoothly to a circular cross -section portion 37. The hexagonal and circular cross-section portions therefore blend one into another in the key members 34.

A locking plate 38 in the form of a rigid, perforated, circular disc includes formed therein a pattern of recesses in the form of through-going, circular apertures 39 that are aligned with the protruding key member portions 37. The size of each aperture is such that the apertures may be fitted over the circular cross-section portions 37. The second guide plate 26 includes formed in its free end a circular recess 41 that is sized to accommodate the locking plate 38 so that the latter may lie flush with the end of the coupler 10.

The locking plate includes in the embodiment shown three screw holes 42 by means of which the plate 38 may be fastened to second guide plate 26 using conventional screws 43 as illustrated.

During assembly of the coupler 10 therefore the locking plate is placed over the protruding key members 34 and the screws 43 tightened. This causes the apertures 39 to engage the material of the key members at the end of the transition between the circular portion 37 and the hexagonal cross-section portion 36. As a result of either the key members 34 being made of a softer metal than the locking plate 38 or vice versa this causes the material of the locking plate 38 and the key members 34 to bind together at the apices of the hexagonal shapes by reason of deformation of the material of one or other of the parts. This effect is identified by numeral 44 in Figures 4 and 5.

The described arrangement amounts to a rotation-inhibiting connection between the key members 34 and the locking plate 38 and any tendency of the key members 34 to rotate would cause the binding of the parts together to become more tight and thereby more strongly inhibit the rotation.

Since the key members by reason of their complementary shape at ends 36 to the sockets 33 are drivingly engaged with the sockets 33 the binding effect described above locks the rods 11 in their pre-tensioned (as assembled) positions and prevents them from rotating towards looser (lower tension) positions notwithstanding the use to which the coupler might be put.

The screws 43 are used temporarily to retain the locking plate 38 in place, after assembly of the coupler 10. In use the coupler 10 would be clamped against a flange similar to flange 29 that would bear against plate 38, retaining it in position. Before such clamping is effected therefore the bolts 43 would be removed.

Although the principles of this invention have been described with reference to the particular embodiment of a railway vehicle coupler they may be applied in a range of other applications in which it is required to prevent unwanted rotation of pre-tensioned, rotatable (especially threaded) parts.

Moreover although the parts of the device are described herein as being made from metals, especiafly steels, they may in other embodiments of the invention be made from a variety of rigid materials including other metal alloys, naturally occurring materials and synthetic materials such as but not limited to composites such as carbon fibre composite materials.

Claims

CLAIMS1. A structure including at least one elongate, rotatable tension rod and an anti-rotation mechanism therefor, the or each tension rod including a head and being captive relative to the structure, the anti-rotation mechanism including a locking plate that is secured relative to the structure and has formed therein or thereon at least one locking plate formation, and the or each head and a said locking plate formation being connected by a key member that is connected non-rotatively to the head and the locking plate formation.
2. A structure according to Claim I wherein the key member engages the material of the locking plate formation so as to cause rotation-inhibiting deformation of the key member and/or the locking plate on rotation of the tension rod.
3. A structure according to Claim 2 wherein the locking plate formation is or includes a recess in which the key member is non-rotatively received.
4. A structure according to Claim I or Claim 2 wherein the head includes a socket defining a polygonal recess in the tension rod and the key member received therein is of complementary exterior shape to the polygonal recess.
5. A structure according to any preceding wherein the or each tension rod includes a screw thread that is threadedly engaged in a respective bore in the structure, the socket being a recess of hexagonal cross-section and being capable in the absence of the key member of receiving a hexagonal tool for tightening and loosening of the screw thread.
6. A structure according to Claim 4 wherein the screw thread extends at one end of the tension rod and the socket is formed at an opposite end thereof.
7. A structure according to any preceding claim wherein the key member is at a first end of polygonal external shape and at a second end of circular external shape of a diameter less than that of a circle inscribing the polygonal shape, the polygonal shape and the circular shape blending into one another along the length of the exterior of the key member.
8. A structure according to Claim 4 or any preceding claim depending therefrom when constituted as a coupler having first and second hollow cylinders that are joined together by way of one or more of the tension rods, the first cylinder being open at a first end and receiving therein a closed end of the second cylinder so as to define a single centre axis of the cylinders, the or each tension rod connecting the said closed end and a second part of the first cylinder remote therefrom and the or each bore being formed in the said closed end.
9. A structure according to Claim 7 wherein the internal diameter of the first cylinder at the first end is greater than its internal diameter at the second part so as to cause deformation of the structure on the compressive load it experiences exceeding a threshold value.
10. A structure according to Claim 7 or Claim 8 including a plurality of the tension rods arranged in a circular pattern that is concentric with the cylinders.
11. A structure according to Claim 9 wherein the circular pattern additionally includes a central tension rod defining an axis that coincides with centre axis of the cylinders.
12. A structure according to any of Claims 7 to 10 wherein the second part of the first cylinder is or includes an opening having received therein the locking plate.
13. A structure according to Claim 8 or any preceding claim depending therefrom wherein the locking plate is a circular disc having formed therein a pattern of circular recesses corresponding to the tension rod pattern.
14. A structure according to any of Claims 7 to 10 wherein the first cylinder includes at least one rod guide plate spanning the interior of the first cylinder and having formed therein one or more through-going apertures (a) defining a pattern corresponding to the tension rod pattern and (b) respectively having a said tension rod extending therethrough.
15. A structure according to Claim 13 including first and second rod guide plates secured respectively at the open end of the first cylinder adjacent the closed end of the second cylinder, and at the end of the first cylinder opposite thereto.
16. A structure according to Claim 14 wherein the second rod guide plate at the end of the first cylinder that is remote from the closed end of the second cylinder includes formed therein a recess for receiving the locking plate.
17. A structure according to Claim 15 wherein the locking plate is fastened to the second rod guide plate.
18. A structure generally as herein described, with reference to and/or as illustrated in the accompanying drawings.