GB2025490A - Shock-absorbing tool for a well drilling string - Google Patents

Abstract

A shock-absorbing tool (10) for a well drilling string comprises a tubular barrel (12) and a tubular mandrel (14) telescopically received therein, the barrel and mandrel being arranged for relative longitudinal movement but being fixed in rotation and defining therebetween an annular chamber (16) including resilient shock-absorbing means (82). Means associated with the barrel (12) and mandrel (14) engage and compress the shock-absorbing means (82) upon relative longitudinal movement of the barrel and mandrel in each direction so that the tool functions to dampen longitudinal movement of the mandrel (14) and barrel (12) with respect to one another regardless of the direction of longitudinal movement. In another embodiment, the shock absorbing means may comprise two portions (106, 108, Fig. 4). <IMAGE>

Description

SPECIFICATION Shock-absorbing tool for a well drilling string This invention relates to drilling tools and is concerned with a shock-absorbing tool for use in a well drilling string for cushioning the drill string against longitudinal movement caused by the drill bit.

When drilling a well, the drill bit is constantly moving up and down and if such movements are transmitted to the drill string they result in shock loads being delivered to the drill string, causing an excessive amount of wear on the equipment.

The industry, therefore, has developed tools, known as shock-absorbers or vibration dampers, which are adapted to be connected in a drill string above the drill bit, usually being connected to the base of the drill collar and to the drill bit, such tools being arranged to absorb a large portion of the vertical impacts caused by the drill bit which would otherwise be passed up the drill string.

Canadian Patent Specification No.

1,014,140 discloses one such tool in which a tubular mandrel is telescopically mounted in a tubular barrel, the mandrel and barrel defining therebetween an annular chamber containing a resilient element in the form of a series of elastomeric rings which absorb longitudinal movements upon compression. In order to prevent the resilient element from being preloaded by the high pressures generally present at the base of a well, the annular chamber is filled with a fluid and has at one end a floating seal ring which compresses the fluid in response to the external well pressure while leaving the resilient element uncompressed.

The tool is so arranged that the resilient element is compressed only when the tool contacts on itself so as to telescope close, and not when the tool extends open, and accordingly the only force acting to prevent sudden extension of the tool is the weight of the drill string bearing down on the mandrel.

In accordance with the present invention there is provided a shock-absorbing tool for a well drilling string, comprising a tubular barrel and a tubular mandrel telescopically received therein, the barrel and mandrel being arranged for relative longitudinal movement but being fixed in rotation, the barrel and mandrel defining therebetween an annular chamber including resilient shock-absorbing means, means associated with said barrel and said mandrel being adapted to engage and compress said shock-absorbing means upon relative longitudinal movement of said barrel and said mandrel in each direction.

The tool of the invention is thus adapted to place the resilient shock-absorbing means under compression when the tool is being both extended and contracted, in contrast with prior art tools that do not function in this way.

The engaging and comressing means conveniently comprise two longitudinally spaced members arranged to move with one of said barrel and mandrel and at least one member arranged to move with the other of said barrel and mandrel, said members extending radially into chamber so as to overlap said shockabsorbing means such that upon relative longitudinal movement of the mandrel and barrel in each direction an associated pair of members moving with the mandrel and barrel move towards one another to compress the shock-absorbing means therebetween dampening the longitudinal movement and acting to restore the barrel and mandrel to an equilibrium position.

In one preferred embodiment of the invention, two longitudinally spaced members arranged to move with said barrel extend radially inwardly into said chamber and two radially spaced members arranged to move with said mandrel extend radially outwardly into said chamber, cylindrical shock-absorbing means being located between said pairs of members.

In an alternative embodiment, two longitudinally spaced members moving with said mandrel extend radially outwardly into said chamber and one member moving with said barrel extends radially inwardly into said chamber between said two members, said shock-absorbing means comprising two portions, each located between one of said members moving with the mandrel and said member moving with the barrel.

The chamber is preferably filled with an hydraulic fluid, the lower end of the chamber conveniently being sealed with a floating seal to permit equalization of pressure inside and outside the chamber and thus prevent the resilient shock-absorbing means from being pre-loaded when the tool is used in a high pressure environment.

In preferred embodiments of the invention, the chamber is divided into upper and lower portions by means of a valved chamber divider arranged to permit unrestricted flow of fluid between the upper and lower chamber portions in one direction but to permit only restricted flow of fluid in the opposite direction, the arrangement being such that on relative longitudinal movement of the barrel and mandrel the volume of the upper and lower chamber portions varies so that fluid is caused to flow from one chamber portion to the other chamber portion via the chamber divider, a dashpot effect thus resulting from relative longitudinal movement of the mandrel and barrel in the sense to cause restricted flow of fluid between the chamber portions.

In this way, movement of the hydraulic fluid is used to assist the damping action of the tool.

Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side elevational view, partly in section, of one embodiment of a shock absorbing tool in accordance with the invention; Figure 2 is an enlarged scale sectional view taken along the line 2-2 of Fig. 1 and viewed in the direction of the arrows; Figure 3 is an enlarged scale fragmentary sectional view of a portion of the tool of Fig.

1; Figure 4 is an enlarged scale side elevational view, partly in section, of a portion of a further embodiment of a shock absorbing tool in accordance with this invention, with a modified shock absorbing mechanism; Figure 5is an enlarged scale side elevational view, partly in section, of a portion of a modified form of the tool of Fig. 1; Figure 6 is a sectional view taken along the line 6-6 of Fig. 5 and viewed in the direction of the arrows; Figures 7 to 10 are schematic drawings showing the shock absorbing tool of Fig. 1 in various stages of operation; Figures 11 and 12 are schematic drawings showing the shock absorbing tool of Fig. 4 in two stages of operation; Figure 13 is an enlarged scale front elevation view of a backup ring used to prevent shearing of shock absorbing disc elements of the tool of Fig. 1;; Figure 14 is a side elevational view of the back ring of Fig. 1 3; Figure 15is an enlarged scale sectional view taken along the line 1 5-1 5 of Fig. 1 and viewed in the direction of the arrows; and Figure 16 is a sectional view taken along the lines 16-16 of Fig. 4 and viewed in the direction of the arrows.

Referring to the drawings, the shock absorbing tool 10 illustrated in Figs. 1, 2 and 3 comprises a tubular barrel 1 2 in which a tubular mandrel 14 is telescopically mounted, the mandrel 14 and barrel 1 2 being arranged for limited longitudinal movement with respect to one another so that they cooperate in a telescoping manner. The tool 10 will thus extend or open if the mandrel 14 moves out of the barrel 1 2 or if the barrel 1 2 moves off the mandrel 14, and will contract or close if the mandrel 14 moves into the barrel 1 2 or if the barrel 1 2 moves into the mandrel 14.

The mandrel 1 4 comprises two longitudinal portions joined by a threaded connection: a lower wash pipe 68; and an upper portion 42 that terminates in a box connection 24 adapted for attachment to a drill collar. A central conduit 70 extends along the length of the mandrel 14.

The barrel 1 2 is similarly made up of four longitudinal portions having threaded interconnections: an upper seal sub 30; a drive key housing 56; an intermediate portion 57; and a bottom sub 26 that includes a threaded portion 28 adapted for attachment to a connection box on a drill bit.

The tool 10 may thus be connected between a drill string and drill bit by means of box connection 24 and bottom sub 24, the central conduit 70 of the mandrel 1 4 communicating with the bore of sub 24 and thus providing a continuous central passageway along the length of the tool to permit drilling mud or other fluid to flow therethrough.

The mandrel 14 and barrel 1 2 define therebetween an annular hydraulic chamber 1 6 which contains a hydraulic fluid such as an oil. The hydraulic fluid is added to the chamber 1 6 by means of fill ports 1 8 and 20 in barrel portion 57 and bleed port 22 in seal sub 30 these ports being closed off by lock screws when not in use.

The seal sub 30 is formed adjacent one end thereof with a series of annular recesses containing respectively, an annular wiper 32, an annular mud seal 34, and an annular oil seal 36, all af which serve to seal the annular chamber 1 6 and prevent the ingress of drilling mud and escape of hydraulic fluid during longitudinal movement of the mandrel 14 and barrel 12.

Also located in a further annular recess of the seal sub 30 is a guide ring 38 having a special bearing surface arranged to maintain the mandrel 14 and barrel 1 2 in axial alignment. It is important that the mandrel 14 be maintained in as near as possible perfect vertical alignment with respect to the barrel 1 2 to prevent lateral loads which could jam the barrel 1 2 and mandrel 14 so as to prevent free longitudinal movement or could cause lateral wobble in the tool 10 resulting in a badly aligned drill hole. The guide ring 38 and a pressure equalizing annular piston 40 (to be discussed hereinafter) serve this purpose.

Although the barrel 1 2 and mandrel 14 may move longitudinally relative to one another, it is necessary that they are not capable of relative rotation, so that rotary motion may be imparted to the drill bit through the drill string. In the present embodiment, relative rotation is prevented by a drive key arrangement.

As best shown in Fig. 2, the upper mandrel portion 42 is formed with two pairs of longitudinally extending shoulders 44, 46 and 48, 50 defining two longitudinal keyways in which respective drive keys 52 are located.

The drive keys 52 are fixed in position relative to the barrel 12, extending into associated notches 54 in the drive key housing 56 of the barrel 12, these notches 54 being bounded at one end by the seal sub 30. The drive keys 52 thus fix the barrel 1 2 and mandrel 1 4 in rotation, while permitting relative longitudinal movement of these components with the drive keys 52 travelling in the keyways defined by the shoulders 44, 46, and 48, 50. The drive keys 52 are covered with a suitable compressable, low friction, temperature-resistant material on the sliding drive surfaces.

The ends of the keyways are defined by an annular shoulder 58 and stops 60 on the upper mandrel portion 42. Although neither of these extreme end points would be reached in normal operation of the tool 10, in the event of a breakdown of the tool 10 the stops 60 act to prevent the barrel 1 2 from coming off the mandrel 1 4 as the drill string is lifted from the well; before this can happen the drive keys 52 will engage the stops 60.

Although the above described embodiment has two drive keys 52, it is clear that the tool 10 could alternatively be designed with a different number of drive keys 52.

As a further alternative, the barrel 1 2 and mandrel 1 4 may conveniently be fixed in rotation by means of an interengaging spline arrangement as shown in Figs. 5 and 6. In this modification, the upper mandrel 42' has situated thereon a plurality of longitudinally extending male splines 62 which interengage longitudinally extending female splines 64 projecting from a barrel spline housing 56'.

To permit free flow of the hydraulic fluid throughout the chamber 16, the splines 62 are provided with fluid grooves 66.

Referring now to Figs. 1 and 3, the annular chamber 1 6 is divided into upper and lower portions by means of an annular member of chamber divider 72 which forms a part of the barrel 1 2 wall and extends therefrom encircling the wash pipe 68. As best seen in Fig. 3, the chamber divider 72 is so arranged that only a small restricted annular flow path 74 is present between divider 72 and the adjacent surface of wash pipe 68 so that only restricted flow of hydraulic fluid between the two portions of the chamber 1 6 via path 74 is possible.As shown in Figs. 2 and 3, a plurality of conduits 76 extend through the chamber divider 72, connecting the two portions of the chamber 1 6. Although twenty such conduits are shown, the tool 10 can work with any number of conduits 76 provided at least one is present. Each conduit 76 contains a one-way valve 78 in the form of a spring-biased ball valve comprising a ball urged upwardly towards a closed position in which it rests on a seat 80 by the action of a spring that is held in position by a threaded plug 81. The valves 78 are thus arranged to permit unrestricted flow of fluid in only one direction, from the upper chamber portion to the lower chamber portion, the valves otherwise being held closed.As a result, hydraulic fluid can flow unrestrictedly from the upper chamber portion to the lower chamber portion via conduits 76 and valves 78, but only restricted flow can occur in the opposite direction via flow path 74.

With reference to Fig. 1, a resilient shock absorbing element 82 is located in the lower portion of chamber 16. Element 82 is in the form of a plurality of resilient annular discs which generally define a cylinder in the annular chamber 16, and is capable of absorbing shocks by undergoing compression and deformation and returning to its original form when the force is removed. Situated at each longitudinal end of the element 82 is a respective annular backup ring 84, shown in detail in Figs. 1 3 and 14, which acts to prevent longitudinal movements causing shearing of the annular discs of element 82 as will be explained hereinafter. In order not to hinder fluid flow about the element 82, each backup ring 84 has a plurality of channels 86 therethrough, as can be best seen in Figs. 1 3 and 15.

Other types of shock absorbing elements 82 may also be used in the tool of the invention. For instance, the element 82 may instead comprise a coil spring with end discs thereon equivalent to the backup rings 84 of the present embodiment.

The shock absorbing element 82 is positioned in annular recesses 88 and 90 in the walls of the barrel 1 2 and mandrel 1 4 within the lower portion of chamber 1 6. The recesses 88 and 90 have the same longitudinal length and are generally opposed to one another. The longitudinal ends of the recesses 88 and 90 define annular shoulders 92, 94, 96 and 98. The mandrel annular shoulder 98 is formed by the addition of a stop nut 100 mounted about the wash pipe 68. The shock absorbing element 82 has radial dimensions such that it extends into the barrel and mandrel recesses 88 and 90 and can be engaged by any of the four shoulders 92, 94, 96 and 98.

The barrel shoulders 92 and 94 constitute longitudinally spaced members situated on the wall of the barrel 1 2 which extend radially inwardly so as radially to overlap the shock absorbing element 82 while the mandrel shoulders 96 and 98 constitute corresponding longitudinally spaced members which extend outwardly to engage the shock absorbing element 82. These shoulders 92, 94, 96 and 98 will act to engage and compress the shock absorbing element 82 in response to longitudinal movement in either direction of the barrel 1 2 and the mandrel 14 with respect to one another, as will be more fully discussed hereinafter.

Situated at the lower end of the annular chamber 1 6 is a pressure equalizing annular piston 40 which engages the opposing walls of the barrel 1 2 and the mandrel 14. As mentioned previously, the piston 40 functions as a guide to prevent lateral movement of the barrel 1 2 and the mandrel 1 4 with respect to one another. The piston 40 also functions as a fluid tight chamber seal to prevent drilling mud from entering the annular chamber 1 6 and hydraulic fluid from leaking out; for this purpose the piston 40 is formed with annular recesses containing appropriate annular mud seals 102 and annular hydraulic fluid seals 104.

The piston 40 is, however, freely longitudinally movable with respect to the barrel 1 2 and the mandrel 1 4 and because of this acts to equalize the pressure inside and outside chamber 16, thus maintaining the fluid pressure within the annular chamber 1 6 at the ambient pressure, e.g. of the drilling mud when in use in a well bore. As the tool 10 is lowered into a well and the drill string is placed in operation, the greater pressures of the tool's environment will force the piston 40 inwardly on the chamber fluid, thus maintaining an equivalent pressure in the chamber 1 6.

Without such a floating piston 40, the high external pressures present in a drill environment would act to close or contact the tool 10 partly or completely, thus leaving a reduced amount of or no longitudinal travel available for absorbing shocks, a condition known as "pre-loading". With the piston 40, however, the tool 10 is not subject to pre-loading in this way and the entire load range of the tool 10 is available to absorb shock loads.

As mentioned previously, the upper mandrel portion 42 is formed with annular shoulder 58. When the barrel 1 2 and the mandrel 14 move longitudinally with respect to one another the barrel 1 2 will either travel up over or come off this shoulder 58, while the shoulder 58 blocks a-corresponding movement of the fluid in the chamber 1 6. Thus, the effect of the shoulder 58 is to cause the chamber fluid to remain relatively stationary with respect of the mandrel 14. The pressure equalizing piston 40, being caught between the balanced pressures of the chamber fluid and the drilling mud, is thus constrained to remain stationary with respect to the mandrel 14 or, to view it from the point of view of the barrel 12, to move to and fro with the mandrel 14 relative to the barrel 1 2.

While the hydraulic fluid moves with the mandrel 14, the chamber divider 72 moves with the barrel 12, being part thereof. The effect of this is to cause fluid flow in chamber 1 6 across the chamber divider 72 in relation to changes in relative longitudinal position of the barrel 12 and the mandrel 14. The shoulder 58 acts to change the volume of the upper portion of the chamber 1 6. However, the one-way valves 78 in the conduit 76 across the divider 72 will only open to permit unrestricted flow in one direction, from the upper chamber portion to the lower chamber portion. Fluid flow in the opposite direction will cause the valves 78 to close and limit fluid flow to the restricted annular flow path 74 between the divider 72 and the wall of the mandrel 14.Thus, longitudinal movement of the barrel 1 2 and the mandrel 14 relative to one another closing or contracting the tool 10 will result in unrestricted fluid flow from upper to lower chamber portions through the conduits 76, while longitudinal movement of the barrel 1 2 and the mandrel 14 relative to one another opening or extending the tool 10 will result in only restricted fluid flow through the flow path 74 causing a dashpot effect dampening that longitudinal movement. The divider 72 along with the other elements of the structure make use of the fluid contained in the annular chamber 1 6 to assist in dampening longitudinal movement. With the divider 72 system, longitudinal free play in the tool 10 is cut to a minimum.

Figs. 7 to 10 illustrate the functioning of the tool 10 when being extended and contracted and show how the shock absorbing element 82 will be placed under compression to absorb longitudinal shocks regardless of the direction in which the tool 10 is displaced from equilibrium Fig. 9 represents the configuration of the tool 10 after being placed in position at the base of a well. With the barrel 1 2 connected to the bit resting on the bottom and the mandrel 1 4 under the weight of the drill string, the tool 10 has contracted slightly with the shock absorbing element 82 being compressed by mandrel shoulder 96 and barrel shoulder 94. The valves 78 are closed as no fluid motion is occurring at the moment.

In Fig. 10 the tool 10 is shown responding to a shock contracting it. The shock absorbing element 82 is placed under greater compression by barrel shoulder 94 and mandrel shoulder 96.

Fig. 7 depicts the return of the tool 10 to an -equilibrium position after being contracted.

Although the element 82 is not at this point absorbing the motion, a dampening effect is provided on the longitudinal motion by the closed condition of the valves 78.

Fig. 8 represents the tool 10 being subjected to an extension. In addition to the dash pot effect of the closed valves 78, the shock absorbing element 82 is still being engaged and placed under compression by one mandrel shoulder 98 and one barrel shoulder 92 moving towards one another to dampen the longitudinal movement and return tool 10 to an equilibrium position. However, in this instance the mandrel shoulder 98 and the barrel shoulder 93 are acting rather than their counterparts.

The backup rings 84 located at the ends of the shock absorbing element 82 give the element 82 support to prevent its being sheared as might otherwise happen because each end of the element 82 is compressed by only one shoulder of each of the mandrel 14 and barrel 1 2 when the element 82 is under load.

Fig. 4 illustrates a portion of a further embodiment of a tool 104 embodying the invention, with a modified shock absorbing mechanism in which the shock absorbing element comprses two portions 106 and 108.

This tool 104 also functions to engage and compress a shock absorbing element in response to relative longitudinal movement of the barrel 110 and mandrel 11 2 in both directions and thus provides shock absorption in both cases.

The tool 104 is generally similar in structure to the tool 10, but includes a split retaining ring 114 secured to mandrel 11 2.

The split retaining ring 114 comprises an annular member mounted on the mandrel 11 2 and extending across the annular chamber 11 6 where it makes contact with the wall of the barrel 110 and acts as a bearing surface to assist in preventing relative lateral movement of the mandrel 11 2 with respect to the barrel 110. The ring 114 is split, having a plurality of longitudinal passages 11 8 in the outer surface thereof to permit fluid flow past the ring. The ring 11 4 also has bronze bearing surfaces.

Longitudinally spaced from the ring 11 4 at the lower end of chamber 11 6 is a pressure equalizing piston 1 20 which moves with the mandrel 11 2 relative to the barrel 110 in the manner previously discussed and is used as one member for engaging and compressing the shock absorbing element portions 106 and 108.

Situated on the wall of the barrel 110 between the ring 11 4 and the piston 1 20 is an annular member 1 22 which extends radially inward to overlap radially the two portions 106 and 108 of the shock absorbing element, each of which is generally cylindrical in form.

The barrel annular member 1 22 also radially overlaps the ring 11 4 and the piston 1 20.

The two shock absorbing element portions 106 and 108 are each therefore longitudinally bounded by the barrel wall member 1 22 and a respective member 114, 120 which moves with the mandrel 11 2 relative to the barrel 110 and extends radially outward to overlap the shock absorbing element portion.

Thus, with relative longitudinal movement of the barrel 110 and the mandrel 11 2 clos ing or contracting the tool 104, as illustrated in Fig. 11, the barrel wall member 1 22 and the ring 11 4 will move towards one another resulting in compression of the shock absorb ing element portion 106, causing dampening of the longitudinal movement and returning of the barrel 110 and the mandrel 11 2 to their equilibrium position. Likewise with movement opening or extending the tool 104, the barrel wall member 1 22 and the piston 1 20 will move towards one another, as illustrated in Fig.12, thus compressing the shock absorb ing element portion 108 therebetween to dampen that longitudinal motion.

Claims (17)

1. A shock-absorbing tool for a well drilling string, comprising a tubular barrel and a tubular mandrel telescopically received therein, the barrel and mandrel being arranged for relative longitudinal movement but being fixed in rotation, the barrel and mandrel defining therebetween an annular chamber including resilient shock-absorbing means, means associated with said barrel and said mandrel being adapted to engage and compress said shockabsorbing means upon relative longitudinal movement of said barrel and said mandrel in each direction.

2. A tool according to claim 1, wherein said engaging and compressing means comprise two longitudinally spaced members arranged to move with one of said barrel and mandrel and at least one member arranged to move with the other of said barrel and mandrel, said members extending radially into said chamber so as to overlap said shockabsorbing means such that upon relative longitudinal movement of the mandrel and barrel in each direction an associated pair of members moving with the mandrel and barrel move towards one another to compress the shock-absorbing means therebetween dampening the longitudinal movement and acting to restore the barrel and mandrel to an equilibrium position.

3. A tool according to claim 2, wherein two longitudinally spaced members arranged to move with said barrel extend radially inwardly into said chamber and two radially spaced members arranged to move with said mandrel extend radially outwardly into said chamber, cylindrical shock-absorbing means being located between said pair of members.

4. A tool according to claim 3, wherein said members are constituted by respective annular shoulders at the ends of an annular recess in each of said mandrel and barrel.

5. A tool according to claim 2, wherein two longitudinally spaced members moving with said mandrel extend radially outwardly into said chamber and one member moving with said barrel extends radially inwardly into said chamber between said two members, said shock-absorbing means comprising two portions, each located between one of said members moving with the mandrel and said member moving with the barrel.

6. A tool according to any one of the preceding claims, wherein said chamber is sealed at its upper and lower ends and is filled with an hydraulic fluid.

7. A tool according to claim 6, further comprising means for maintaining the pressure of said hydraulic fluid equal to ambient pressure outside the chamber.

8. A tool according to claim 7, wherein said pressure maintaining means comprise a floating seal at the lower end of the chamber, one side of the seal being exposed to ambient pressure and the other side thereof contacting hydraulic fluid within the chamber.

9. A tool according to claim 8, wherein said floating seal is arranged to move with one of said mandrel or barrel upon relative longitudinal movement thereof.

10. A tool according to claim 9 when dependent on any one of claims 2 to 5, wherein said floating seal constitutes one of said members.

11. A tool according to any one of claims 6 to 10, further comprising a valved chamber divider dividing said chamber into upper and lower portions and arranged to permit unrestricted flow of fluid between the upper and lower chamber portions in one direction but to permit any restricted flow of fluid in the opposite direction, the arrangement being such that on relative longitudinal movement of the barrel and mandrel the volume of the upper and lower chamber portions varies so that fluid is caused to flow from one chamber portion to the other chamber portion via the chamber divider, a dash pot effect thus resulting from relative longitudinal movement of the mandrel and barrel in the sense to cause restricted flow of fluid between the chamber portions.

1 2. A tool according to any one of the preceding claims, further comprising means for preventing shearing of said shock-absorbing means upon relative longitudinal movement of the barrel and mandrel.

1 3. A tool according to claim 12, wherein said means for preventing shearing comprise annular rings positioned at the longitudinal ends of said shock-absorbing means.

1 4. A tool according to any one of the preceding claims, further comprising stop means for restricting relative longitudinal movement of the barrel and mandrel.

1 5. A shock-absorbing tool substantially as herein described with reference to, and as shown in, Figs. 1 to 3, 7 to 10, and 1 3 to 16 of the accompanying drawings.

16. A shock-absorbing tool substantially as herein described with reference to, and as shown in Figs. 4, 11 and 1 2 of the accompanying drawings.

17. A tool according to claim 1 5 or 16, modified substantially as described with reference to, and as shown in Figs. 5 and 6 of the accompanying drawings.

1 8. Any novel feature or novel combination of features disclosed herein.