EP0177598A1

EP0177598A1 - Retaining ring

Info

Publication number: EP0177598A1
Application number: EP19850902076
Authority: EP
Inventors: David Anthony Bates
Original assignee: George Salter and Co Ltd
Current assignee: George Salter and Co Ltd
Priority date: 1984-04-24
Filing date: 1985-04-23
Publication date: 1986-04-16
Also published as: WO1985004934A1; GB8410385D0; GB2157786A; AU4219885A; GB2157786B

Abstract

Une attache à emboîtement (1) possède trois pattes ou dents (2) équidistantes et dirigées radialement vers l'intérieur. Les dents (2) possèdent des surfaces extrêmes arquées (3) pour engager la périphérie circulaire de l'arbre. Chaque patte ou dent (2) est conçue de sorte que l'attache (1) puisse supporter des charges importantes. Dans un autre mode de réalisation, la bague de retenue est une attache à enfoncement.An interlocking fastener (1) has three legs or teeth (2) equidistant and directed radially inwards. The teeth (2) have arcuate end surfaces (3) to engage the circular periphery of the shaft. Each leg or tooth (2) is designed so that the fastener (1) can support heavy loads. In another embodiment, the retaining ring is a push-in fastener.

Description

RETAINING RING

Technical Field

This invention relates more particularly but not exclusively to a retaining ring of a type which is referred to in the art as a 'push-on fix' and which may be introduced axially onto a shaft to firmly grip the shaft (hereinafter referred to as Of the type specified').

Background Art

Push-on fixes of the type specified are designed to fulfill certain performance requirements and to withstand axial forces which may be exerted on the fix (in a direction reverse to the introduction direction of the fix on the shaft) after it has been attached onto a shaft. The axial force which can be exerted on a push-on fix when attached to a shaft of appropriate size without the fix 'yielding' and then being urged off the shaft will vary somewhat depending upon the hardness value of the shaft. The push-on fix may be of carbon spring steel, beryllium copper, phosphor bronze or stainless steel. Shafts of high hardness value include cold-rolled steel shafts. Hitherto pushr-on fixes have been made which have a yield point somewhere around IKN. This level of yield point limits the applications where push-on fixes can be employed. Similarly the yield point level of retaining rings referred to in the art as 'push-in fixes' (a fix which is introduced axially into a bore or hollow shaft) may possibly limit the applications where push-in fixes can be employed.

It is an object of the present invention to provide an improved push-on or push-in fix having a higher yield point than hitherto achieved.

Disclosure of Invention

According to the present invention there is provided a retaining ring comprising a plurality of radially inwardly directed legs or teeth to grip onto a shaft and thereby attach the ring to the shaft on introducing the ring generally axially onto the shaft, the thicknesses of the legs or teeth being so selected relative to their radial extent - and the relative dimensions of the retaining ring being so selected relative to shaft size that the ring is adapted to withstand an axial force in the direction reverse to the introduction direction of the ring on the shaft of at least 4KN before yielding.

_Q Further according to the present invention there is provided a retaining ring comprising a plurality of radially inwardly directed legs or teeth to grip onto a shaft and thereby attach the ring to the shaft on introducing the ring generally axially onto the shaft, the thicknesses of the legs or teeth being so selected relative to their 5 radial extent that the inequality L/t² < 4 applies, where L = radial extent of a leg or tooth and t = material thickness of the legs or teeth.

The push-on fix may be such that the yield force lies in the 0 range 4KN to about 9KN and/or the ratio L/t² may have a value less than 1.5.

The thickness of the push-on fix may be about 0.9 mm (in the order of twice the thickness of conventional push-on fixes which may 5 vary from 0.23mm up to 0.5mm over the whole size range of fixes) and/or the radial extent of each tooth may be about 1.1 mm (in the order of 1/3 radial extent of teeth of most conventional fixes). The external diameter of the push-on fix may be 20mm (conventional tooth length for a fix of this size is about 0.38mm). 0

The push on fix may be provided with three equiangularly spaced teeth or legs and/or the legs may extend at an angle of about 45° (± 5°) to the general plane of the push-on fix.

5 The shaft may have a Vickers hardness value of 250 to 300 and/or the ring may be fitted on the shaft with an interference fit of 0.38mm.

Further according to the present invention there is provided a retaining ring comprising a plurality of radially outwardly directed legs or teeth to grip into a bore and thereby attach the ring to the bore on introducing the ring generally axially into the bore, the thicknesses of the legs or teeth being so selected relative to their radial extent that the inequality L/t² _ 4 applies, where L = radial extent of a leg or tooth and t = material thickness of the legs or teeth.

Still further according to the present invention there is provided a retaining ring comprising a plurality of radially outwardly directed legs or teeth to grip into a bore and thereby attach the ring to the bore on introducing the ring generally axially into the bore, the thicknesses of the legs or teeth being so selected relative to their radial extent and the relative dimensions of the retaining ring being so selected relative to bore size that the ring is adapted to withstand an axial force in the direction reverse to the introduction direction of the ring into the bore of at least 4KN before yielding.

The material of the bore may have a Vickers hardness value of 250 and /or or each leg or tooth may be provided with an arcuate end surface.

In general, the legs or teeth will be of the same material thickness and dimensions and equiangularly spaced; the material thickness will be the same as the material thickness of the ring.

Brief Description of the Drawings

An embodiment of a retaining ring in accordance with the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIGURE 1 shows a plan or axial view of the retaining ring; FIGURE 2 shows a front or radial view of the retaining ring;

FIGURE 3 shows a detail cross sectional view taken on line III— III of FIGURE 1;

FIGURE 4 shows an experimental graph of a load test done on the retaining ring;

FIGURE 5 shows a theoretical graph of the variation in push-off yield ffoorrccee wwiitthh tthhee rraattiioo L/t (L = radial extent of a leg or tooth and t = material thickness),

FIGURE 6 shows a theoretical graph of the variation in push-off yield force with L for a constant t and also the variation of push-off yield force with t for a constant L,

FIGURE 7 shows a theoretical graph of variation in push off yield force with material thickness for a range of tooth lengths, and

FIGURE 8 shows a theoretical graph of variation in push off yield force with tooth lengths for a range of material thickness.

Mode for Carrying Out the Invention

FIGURES 1 to 3 show a retaining ring or push-on fix 1 of carbon spring steel having three equidistantly spaced radially inwardly directed legs or teeth 2. FIGURES 1 and 2 are drawn twice full size and the external diameter of the push-on fix is 20 mm. FIGURE 3 is drawn four times full size. The push-on fix is designed to be attached to a generally cylindrical shaft (not shown) of diameter 11.76 mm. Each tooth 2 is provided with an arcuate end surface 3 which engages the circular periphery of the shaft. Each tooth 2 gradually tapers radially inwardly and has a mean tooth width b (see FIGURE 2). The thickness of the fix 1 is designated t and the radial extent of each tooth is designated L. The push on fix 1 was attached to the shaft by using a standard assembly tool (not shown) to introduce the fix generally axially onto the shaft in the direction of arrow A (see FIGURE 2). Next, a standard load test was carried on the push on fix 1 whilst attached to the shaft and as can be seen from FIGURE 4 the push-on fix withstood a force of 8.7 KN in a direction reverse to arrow A before 'yielding' and then becoming detached from the shaft. The teeth 2 are effectively pulled inside out or over centre during the test and a further lesser force is required to push the fix 1 off the shaft once lø the fix has 'yielded' or failed (yield point). This figure of 8.7 KN represents approximately ten times the yield force of a standard conventional push on fix of similar external diameter when applied to a similar shaft! FIGURE 4 shows a graph of the push-off force applied P (plotted along the vertical axis) and displacement (initially of the

15 outer portions of the fix only until the yield point) is plotted along the horizontal axis. As shown the outer parts of the fix 1 are displaced somewhat until the fix yields at the peak of the graph at 8.7 KN. The fix 1 is then pushed along the shaft by a lesser force until it is pushed off the shaft at the trough of the graph. 0

The thicknesses of the teeth 2 of the push on fix 1 may be selected relative to their radial extent and the relative dimensions of the shaft so selected that the push-on fix engagement with the shaft can withstand much greater axial forces than conventional push- 5 on fixes.

A theoretical study has been done on the behaviour of push-on fixes and according to the theory:-

F 0 ^di = . - ω bv flT

3 (2-^) d 4L³ 1 ₅ ^F = ^{+ +} »

4 TΓ t(D-d)E E b t ³ bv/T^" Mean tooth width = b Young's Modulus for fix material = E

Number of teeth = n Poisson's ratio = ^~\)

Material thickness = t Total Length (extent of tooth in radial direction) = L (for steel, E = 2.068 x 10⁵

N/mm² and . = 0.3) Outside diameter = D Tooth root diameter = d

Vicker's hardness number Force inwards for a single tooth = F for shaft material = V

Interference between fix and shaft = i Depth of identation in shaft = dj Coefficient of friction between shaft material and fix = JUU

When forced onto a shaft, three main types of deformation of the push-on fix are possible:

1) Bending of the teeth; 2) Coning of the fix, in the manner of a Bellville Washer and 3) Expansion of the fix as a ring with internal pressure

In equation (2): the deflection due to coning is:

3 (2 - .

4 TT t (D-d) E

the deflection due to tooth bending is _4L 3 and

E bt³

the depth of dig-in of the tooth on the shaft is 1

bvj ^" The radial deformation due to the combination of coning, tooth bending and depth of dig-in is equal to the interference between the push-on fix and shaft. The expansion of the fix as a ring under pressure was found to be negligible compared with other effects and therefore equation 2 is generated.

Now the push-off load P (force urging the fix axially off the shaft) is given by the equation.

P = n b d i x UTS + n . F - (3)

(assuming the shaft material fails in shear before the pressure fix fails)

_ . P ^~^ F

where n = number of teeth on push-on fix and UTS = ultimate tensile strength of shaft material

will be between 0 and 1.

Now, maximum stress in the teeth due to bending is given by stress C = 6M where M = bending moment

bt²

cr = 6 F L

(When applied to elastic bt bending only)

Once the yield stress is reached, the teeth will take a set and interference between the fix and the shaft will be lost.

The force to just produce yield stess is given by: Fy = bt^ώ ~ where ~T^~. = yield stress

^■3

6L

Once this force Fy is reached, equation (2) no longer applies. It is a more accurate assumption to assume that F = Fy for all interference values greater than the value which just causes yielding.

So if

3(2 - _. ) d 41? b t

- >

4'TTt (D-d)E Ebt³ bv]T 6 L

Then F = bt² C

6L

For the large interferences, the push on fixes in accordance with the present invention will still operate in the elastic mode, but a conventional fix will take a set.

For earlier conventional ranges of push-on fix, the tooth deflection is of the same order as the dig-in on the shaft and the deflection due to coning is relatively small. As the ratio L/_t becomes small, tooth deflection becomes small in comparison with dig- in. For a shaft hardness number around 300, a value of _t close to unity gives a tooth deflection only 1% of the dig-in value. Thus the main mode of operation depends in principle on the ratio of tooth length L to thickness t. The above equations were checked against experimental push-off yield force values. Measured values were up to 25% higher than the theoretical values, probably due to the way in which the teeth tend to dig in even deeper as attempts are made to push the fix off. The fix flattens, so gripping the shaft more tightly, and the angle of the teeth (approximately 45°) is such that they tend to dig into the shaft rather than pull off. When the push-on fix 1 is fitted on a shaft , the legs bend and the fix cones in the same way as a Belleville washer. In conventional designs of push-on fix, bending of the legs is the main mode of deflection, and coning is relatively unimportant. In the push-on fix in accordance with the present invention, they are of the same order of magnitude.

The teeth 2 grip the shaft and tend to dig into the shaft material. In the fix 1 there is relatively little deflection of the teeth 2 and so the gripping force is higher and the amount of dig-in larger.

When the fix 1 is pushed off, it flattens, increasing the gripping force on the shaft. This increase is more marked than with conventional push-on fixes because the effects of coning are more important than with conventional fixes.

FIGURE 5 shows a plot of variation of push-off yield force P (in KN) with L/t² according to the theoretical model described. This model is based on the push on fix shown in FIGURES 1 to 3 which has an external diameter of 20 mm, an internal diameter of 11 mm, three teeth and a 0.38 mm interference on the shaft. FIGURE 5 illustrates the dramatic increase in push off yield force (yield force positions lie on the curve shown in FIGURE 5) where the ratio of L/t² * . 4.

By way of a comparison, previously measured yield force values for conventional fixes of varying sizes (plotted for fixes in the series 5115, 7115, 7300 of Salterfix Limited) are marked with crosses on the graph of FIGURE 5. In fact these valves are not a true comparison since these are 'safe' maximum allowable service limits and indeed a truer comparison would be to show these values about 30% higher up the push-off force vertical scale. As shown the lowest value of L/t² is greater than 9 and may be as high as 26. The actual yield force Y is marked on the graph for the push-on fix 1 as well as its safe maximum allowable force in service X by way of comparison. FIGURE 6 shows a theoretical plot of variation of push-off yield force P with LQine A) in which the thickness of the fix basically as shown . in FIGURES 1 to 3 has been kept constant at 0.9 mm with an interference fit of 0.38 mm on the shaft.

Additionally, FIGURE 6 shows a theoretical plot of variation of push-off yield force P with t(line B) in which the length L has been kept constant at 1.1 mm (minimum tooth length for conventional fix of any size) with an interference fit of 0.38 mm on the shaft.

As shown by line A with a thickness of push-on fix twice the order of magnitude of a conventional fix and a tooth length in the order of a conventional fix for a 20mm external diameter, theory predicts that a push-off or yield force of only just over 3 KN could be achieved. Line B predicts that with a tooth length of about 1/3 the order of magnitude of a conventional fix once the thickness has been increased beyond about 1.5 mm (more than four times conventional thickness) the push-off yield force decreases rapidly and when the thickness is in the order of 9 or 10 times the conventional thickness the yield force drops to about 1 KN.

Range X represents the ideal range of push-on fixes; the fix behaves as a coned-washer spring and bending of the teeth is relatively small. Range Y represents the transition range where the teeth will take a set Range Z is the range for conventional push on fixes where tooth bending accounts for most of the interference on the shaft.

FIGURES 7 and 8 have been included to further illustrate the remarkable increase in yield force which can be obtained over the whole range of push-on fixes.

FIGURE 7 once again shows variation in push-off force P plotted against material thickness t but this time over a range of thickness of 0.25mm to 1.0mm. In fact line B' represents an extension of line B in FIGURE 6 over a range of thickness t not shown in FIGURE 6. For a fix of external diameter 20mm the conventional thickness is about 0.38mm and therefore as predicted by line B' the yield force would only be about 0.75KN by reducing the tooth thickness to about 1/3 the conventional order of magnitude without altering the conventional thickness of the fix.

By way of a general comparison line C represents a plot of P v.s.t. where the tooth length L - 25mm (maximum tooth length for a conventional fix). The range X' represents the range in which conventional fixes lie and the shaded area X" represents the area within which various predicted yield points lie for conventional fixes showing that the best yield force achievable in theory for a conventional fix is still less than 3KN which is generally in line with empirical results.

FIGURE 8 shows once again variation in push off force P plotted against tooth length L. Line A' represents a portion of line A in FIGURE 6 drawn to different length scale for comparison with lines D and E. Line D is the plot of P.v.s.L for a material thickness t = 0.5mm (maximum value of t for a conventional fix) and line E is the plot of P.v.s. L for material thickness t = 0.23mm (minimum value of t for a conventonal fix). The shaded area D' E' represents the possible yield point values achievable with conventional fixes showing once again that the theoretical maximum value is still less than 3KN which is generally in line with empirical results.

It is an advantage of the present invention that by selecting appropriate tooth length and material thickness a push-on fix of a given size can be produced which will have a yield force of a chosen value and this value can be a selected value from a range of possible values much higher than can be achieved with conventional push-on fixes. The careful selection of tooth length relative to material thickness allows hitherto unexpected very high yield points to be achieved.

Although the aforegoing empirical results and theory relate only to a push-on fix it is believed that a similar general principle can be applied to push-in fixes in a manner which would readily be envisaged. Therefore, it has not been thought necessary to include further information regarding push-in fixes in accordance with the present invention.

The retaining ring in accordance with the present invention has a much higher yield force and therefore can be used in many applications which have not hitherto been practical. One such application is in the field of adjustable pipe support arrangements and using a push-on fix retaining ring in an adjustable pipe support arrangement advantageously facilitates manufacture and may considerably cut down on costs of other designs of pipe support arrangement.

Technical Field

This invention also relates in a second aspect to an adjustable pipe support arrangement used for supporting a pipe along its length and so that the pipe may, for example, be suspended at a fixed distance from an overhead girder.

Background Art

A previously proposed pipe support arrangement has a long rigid rod of about 40 cm in length. An inherently resilient spring clip or clamping bracket is provided at an upper end of the rod and a one piece pipe bracket is releasably retainable on the lower end of the rod by the use of a locking collar which is slid over free end projections of the bracket. The rod itself is provided with a screw- thread along its entire length and at its upper end is screw threadably engaged with the spring clip; at its lower end it is screw-threadably engaged with a specially shaped elongate nut co- operable with the projections on the pipe bracket so that the pipe bracket is retained to the rod by the locking collar being slid over the projections and nut thereby holding the projections in retaining engagement with the nut. The spring clip is adapted to fasten the pipe support arrangement to an overhead girder or roof section. The distance that the rod extends below the spring clip and therefore the height at which a pipe may be supported in the pipe bracket is variable by way of the screw thread engagement between the clip and rod and by rotating the rod relative to the clip.

Firstly, and most importantly, the spring clip is engaged with the rod by means of a screw-thread on the rod. The cost of providing a long rod with a screw-thread along its length is a considerable cost of the pipe support arrangement but is necessary to give a full range of adjustment of the height of the pipe (i.e. the distance between the girder and the pipe needs to be variable over the rod length). Additionally, the screw-thread engagement between the spring clip and rod tends to be a disadvantage since the rod has to be rotated to move it up or down relative to the clip. Since the rod has to be rotated to adjust the length of rod extending downwardly beyond the clip (and since in general a pipe length will be supported by a plurality of similar pipe support arrangements along its length and attached to an overhead girder) the height of the pipe cannot be conveniently adjusted without disconnecting the pipe bracket from the rod by moving the locking collar to free the end projections of the bracket thereby allowing access to the nut on the rod end for rotation of the rod. This means that the pipe is not supported by the support arrangement while its height is adjusted. The pipe would have to be supported by hand or by other pipe support arrangements along its length during height adjustment and each pipe support arrangement would have to be individually adjusted to raise or lower a whole length of pipe. This also tends to be a disadvantage, particularly where very long lengths of piping are involved and also a large number of pipe support arrangements.

Secondly, and also importantly, the previously proposed pipe support arrangement is provided with a specially shaped nut. The nut is shaped so that its exterior will interlock with the bracket projections when the locking collar is in place to retain the pipe bracket to the rod. The provision of such a nut tends to be a disadvantage because it is so costly to manufacture.

It is an object of the present invention to provide a pipe support arrangement in which at least some of the aforementioned disadvantages are alleviated.

Disclosure of Invention

According to a second aspect of the present invention there is provided an adjustable pipe support arrangement comprising a rod provided at one end with clamping means to clamp onto a fixture, for example a girder, and provided at the other end with a pipe bracket through which the pipe is to extend in use, the pipe bracket being releasably lockable to said other rod end and the rod being longitudinally adjustable relative to the clamping means, said other end of the rod having a retaining ring formed individually from said rod and engaged with said other rod end by a force fit, said bracket having projections which in use embrace the retaining ring and a locking collar which in use surrounds the rod and holds said projections to the rod and retaining ring such that the engagement of the retaining ring on the rod retains the pipe bracket on the rod.

The retaining ring may have any of the features as hereinbefore mentioned.

Also, the adjustable pipe support arrangement may have an advantageous adjustment and further according to the present invention there is provided an adjustable pipe support arrangement comprising a rod provided at one end with clamping means to clamp onto a fixture, for example a girder, and provided at the other end with a pipe bracket through which the pipe is to extend in use, the pipe bracket being releasably lockable to said other rod end and the rod being longitudinally adjustable relative to the clamping means by a movement of the rod in each of opposed longitudinal directions of the rod, the adjustable pipe support arrangement carrying releasable locking means in the form of a swivel plate which locks the rod relative to the clamping means against movement in one of said opposed longitudinal directions and the arrangement being such that on release of the releasable locking means the longitudinal position of the rod relative to the clamping means may be adjusted in each of said opposed longitudinal directions by a linear movement of the rod.

Further according to the present invention there is provided an adjustable pipe support arrangement comprising a rod provided at one end with a clamping bracket to clamp onto a fixture, for example an overhead girder, and provided at the other end with a pipe bracket through which a pipe is to extend in use, the pipe bracket being releasably lockable to said other rod end and the rod being longitudinally adjustable relative to the clamping bracket by a movement of the rod in each of opposed longitudinal directions of the rod, said clamping bracket carrying releasable locking means in the form of a swivel plate which automatically locks the rod relative to the clamping bracket against movement in one of said opposed longitudinal directions but simultaneously allows longitudinal movement of the rod in the other of said opposed longitudinal directions.

The pipe support arrangement as described in either of the two immediately preceding paragraphs may have a retaining ring formed individually from said rod and engaged with said other rod end by a force fit, said bracket having projections which, in use, embrace the retaining ring and a locking collar which in use surrounds the rod and holds said projections to the rod and retaining ring such that the engagement of the retaining ring on the rod retains the pipe bracket on the rod.

Brief Description of Drawings

An embodiment of a pipe support arrangement in accordance with the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:- Mode for Carrying Out the Invention

FIGURE 9 shows a sectional view of a previously proposed pipe support arrangement, and

FIGURE 10 shows a sectional view similar to that of FIGURE 9 but of the embodiment of the pipe support arrangement in accordance with the present invention.

FIGURE 9 shows a previously proposed adjustable pipe support arrangement 1 having a long externally - threaded rod 2 of about 40 cm in length and of generally circular cross section. The upper end of the rod is screw threadably engaged with clamping means in the form of a spring clip or clamping bracket 3 having legs 3a which embrace a fixture such as an overhead girder. The legs 3a are urged apart as the bracket 3 is fitted onto the girder and teeth 3b 'bite' into the girder to secure the bracket 3 to the girder. In this way the pipe support arrangement may be suspended from the girder.

specially shaped elongate nut 4 having a blind internal screw thread and of generally circular cross section is screw-threadably engaged on the lower end of the rod 2 and has a knurled surface 4a around the upper peripheral portion thereof. The knurled surface 4a is to aid in assembling and dis-assembling the nut 4 from the rod 2. As shown in FIGURE 9 the nut 4 is shaped to co-operate with free end projections 5a of a one-piece pipe bracket 5. The lower end of the nut 4 has a portion of diminished diameter and may generally be described as diablo shaped although portion 5b is part spherical.

To attach a pipe to the rod 2 the pipe is introduced into the pipe bracket 5 and a cylindrical locking collar 6 is introduced axially upwardly onto the rod 2 over and beyond the specially shaped nut. The pipe bracket projections 5a are urged more closely together by hand while being arranged to engage and straddle the lower end of the nut 4 and the collar 6 is then moved axially downwardly over the nut 4 and projections 5a so that the projections 5a are held in retaining engagement with the nut 4 by the collar 6. The pipe bracket 5 can be released from the rod 2 simply by moving the locking collar 6 axially upwardly beyond the projections 5a which then spring out of engagement with the nut 4.

In order to conveniently adjust the height of a pipe in the pipe bracket 5 relative to the clamping bracket 3 the projections 5a need to be disengaged from the nut 4 so that access may be gained to the nut 4. The nut 4 may be gripped by the knurled surface 4a to rotate the rod 2 clockwise or anticlockwise to adjust the amount by which the rod extends below the clamping bracket 3 by way of the screw thread engagement between the rod 2 and bracket 3. Once the rod 2 has been adjusted by the desired amount, the projections 5a can be re-engaged with the nut 4 in the manner as aforedescribed and the locking collar 6 moved downwardly to retain the pipe bracket 5 to the rod 2 once again. Since the pipe bracket 5 is actually disconnected from the rod 2 whilst the rod adjustment is made it is necessary to exercise some degree of judgement as to what height the pipe will be at once the bracket 5 is re-connected onto the rod end 2. This may hamper an accurate or fine adjustment of the height of the pipe being made at least on an initial adjustment of the rod.

Usually, such pipe support arrangements would be arranged along a length of pipe and spaced apart from one another by more than a metre. Therefore, in order to adjust the height of the length of pipe each pipe support rod needs to be individually adjusted. The pipes which are supported by such arrangements may be, for example, water pipes or gas pipes and such arrangements are particularly applicable in industrial environments where the pipes which are supported are not necessarily going to be a permanent fixture. In such circumstances the height or incline, for example, of pipes may be important as well as the adjustment height facility.

FIGURE 10 shows a view similar to FIGURE 9 of an embodiment of an adjustable pipe support arrangement 7 in accordance with the present invention. The pipe support arrangement 7 has a generally cylindrical iron rod 8 which has no external screw thread. The upper portion of clamping bracket 9 is similar to that of clamping bracket 3 in FIGURE 9 and, therefore, will not be further described. However, the engagement between the rod 8 and bracket 9 is very different to the screw thread engagement described in relation to FIGURE 9:

A hardened swivel plate 10 has a projection 10a mounted in a slot 11 in one side of the clamping bracket 9. The plate 10 can pivot or swivel about the slot 11 from the position shown as position 'A' in FIGURE 9 (which is the rod locking position) to the position shown as 'B^* in which the plate 10 is shown in chain-dotted lines (position 'B' is the unlocked position). Plate 10 is generally rectangular with a generally central hole 12 passing through the plate 10. Hole 12 is of slightly larger diameter than the rod 8 but when in position 'A' edges 13 and 14 bite into rod 8 as a downward force is applied to rod 8. This restrains downward movement of the rod 8 but simultaneously allows upward movement of the rod since on an upward mvoement of the rod the plate 'swivels' to position B about slot 11 until the axis of hole 12 is aligned with the axis of the rod 8. As soon as the rod 8 is moved back downwardly the action of gravity causes the left-hand end of the plate 10 to rotate downwardly about slot 11 and the edges 13 and 14 once again engage the rod 8 in position A restraining any further downward movement of the rod.

The swivel plate 10 constitutes releasable locking means since the 'released' position corresponds to position B and the plate may be urged to, and held, in this position by a finger or thumb pushing upwardly on the left-hand end of plate 10, which end comprises a finger grip portion extending from the generally rectangular form of the plate 10 and, as viewed in FIGURE 10, in front of the clamping bracket 9.

Thus a simple releasable locking action is provided for.

Instead of a specially shaped nut being provided on the lower end of the rod 8 a retaining ring R generally of the form shown in FIGURES 1 to 3 is applied onto the lower end of the rod 8.

The pipe bracket 5' has free end projections 5a' which are shaped to co-operate with the ring R and a locking collar 6' is provided to lock the end projections 5a' to the ring R and to the rod in a similar manner as described in relation to FIGURE 9.

The provision of the ring R, avoids the necessity and expense of a specially shaped knurled nut and screw thread on the rod 8.

It is to be understood that individual features as aforementioned or as shown or combinations thereof, or functions appertaining thereto, may be patentably inventive and any specific term as used herein should not be construed as unecessarily limiting, the scope of such term should extend to any reasonable equivalent or generic expression.

Claims

1. A retaining ring comprising a plurality of radially inwardly directed legs or teeth to grip onto a shaft and thereby attach the ring to the shaft on introducing the ring generally axially onto the shaft, characterised by the thicknesses of the legs or teeth being so selected relative to their radial extent and the relative dimensions of the retaining ring being so selected relative to shaft size that the ring is adapted to withstand an axial force in the direction reverse to the introduction direction of the ring on the shaft of at least 4KN before yielding.

2. A retaining ring comprising a plurality of radially inwardly directed legs or teeth to grip onto a shaft and thereby attach the ring to the shaft on introducing the ring generally axially onto the shaft, characterised by the thicknesses of the legs or teeth being so selected relative to their radial extent that the inequality L/t -< 4 applies, where L = radial extent of a leg or tooth and t = material thickness of the legs or teeth.

3. A retaining ring as claimed in Qaim 1 in which said force lies in the range 4KN to about 9KN.

4. A retaining ring as claimed in Qaim 2 in which the ratio L/t² has a value less than 1.5.

5. A retaining ring as claimed in any one of the preceding claims in which thickness of the ring is about 0.9 mm, the radial extent of each leg or tooth is about 1.1 mm, the external diameter is 20mm, and in which the ring may be fitted on the shaft with an interference fit of 0.38mm.

6. A retaining ring as claimed in any one of the preceding claims in which the ring is, preferably, of carbon spring steel, and is provided with three equiangularly spaced teeth or legs, and, preferably in which the legs or teeth extend at an angle of about 45° ( £ 5°) to the general plane of the ring, and, preferably, each leg or tooth tapers radially inwardly.

7. A retaining ring comprising a plurality of radially outwardly directed legs or teeth to grip into a bore and thereby attach the ring to the bore on introducing the ring generally axially into the bore, characterised by the thicknesses of the legs or teeth being so selected relative to their radial extent that the inequality L/t² 4 applies, where L = radial extent of a leg or tooth and t = material thickness of the legs or teeth, and, preferably, in which L/t < 1.5.

8. A retaining ring as claimed in any one of the preceding claims in which the shaft or material of the bore, as the case may be, has a Vickers hardness value of 250 to 300.

9. A retaining ring as claimed in any one of the preceding claims in which each leg or tooth has an arcuate end surface.

10. An adjustable pipe support arrangement comprising a rod provided at one end with clamping means to clamp onto a fixure, for example a girder, and provided at the other end with a pipe bracket through which the pipe is to extend in use, the pipe bracket being releasably lockable to said other rod end and the rod being longitudinally adjustable relative to the clamping means, said other end of the rod having a retaining ring formed individually from said rod and engaged with said other rod end by a force fit, said bracket having projections which in use embrace the retaining ring and a locking collar which in use surrounds the rod and holds said projections to the rod and retaining ring such that the engagement of the retaining ring on the rod retains the pipe bracket on the rod.

11. A pipe support arrangement as claimed in Qaim 10 including a retaining ring as claimed in Claim 1 or Claim 2, or in any claim dependent from Qaim 1 or Qaim 2.

12. A pipe support arrangement substantially as herein described with reference to FIGURE 10 of the accompanying drawings.

13. A pipe support arrangement as claimed in Qaim 10 in -which the retaining ring, bracket, locking collar and rod are substantially as herein described with reference to FIGURE 10 of the accompanying drawings.

14. A retaining ring substantially as herein described with reference to FIGURES 1 to 3 of the accompanying drawings.

15. The combination of a retaining ring as claimed in Qaim 1 or Qaim 2 or any claim dependent therefrom and a shaft having a Vickers hardness value of about 250.

16. The combination of a retaining ring as claimed in Qaim 7 or any claim dependent therefrom and a bore in which the material of the bore has a Vickers hardness value of about 250.