SE540128C2 - A fuel tank attachment structure for a motor vehicle - Google Patents

Abstract

A fuel tank attaching structure (5) in a motor vehicle having at least one expandable and contractible fuel tank (4) for storing compressed gas mounted thereon, comprising at least one bracket (8) fixed to a vehicle chassis for supporting the at least one fuel tank (4), at least one tensioning strap (7) around the fuel tank (4) and a fastening element (39) between the tensioning strap (7) and the bracket (8). At least one spring means (75) is acting between the fastening element (39) and the bracket (8) whereby a spring load of the spring means (75) applies a holding force of the tensioning strap (7) to the fuel tank (4) regardless of whether the gas tank (4) is expanded or not.

Description

1 A fuel tank attaching structure for a motor vehicleTECHNICAL FIELD The present invention relates to a fuel tank attaching structure for a motor vehicle and a motor vehicle comprising a fuel tank attaching structure according to the claims.BACKGROUND AND PRIOR ART Pressure tanks with pressurized gas are used in many applications. Tanks are usuallymanufactured of materials having high strength against internal and external forces, such as ofmetal or composite materials. Such tanks can be used in vehicles that are driven withcompressed natural gas (CNG). ln vehicles, the tanks may be retained in tank assembliescomprising 2-6, normally 4 cylindrical tanks. A tank assembly may be mounted to a chassis ina heavy vehicle, such as in a truck or a bus. ln the assembly, the tanks may be held together inmounting brackets by means of distance elements filling the space between the tanks andtensioning straps surrounding the tanks. Relatively high holding forces from the tensioningstraps are required to hold the tanks in place in the brackets. ln heavy vehicles it may bedifficult to keep sufficiently high holding forces during driving since the diameter of eachtank varies with the gas pressure in the tank. This is because the tanks eXpands during a gasfilling process when the gas pressure increases and contracts during gas consumption whenthe gas pressure decreases. A consequence of this is that when the tanks are in an eXpandedphase the holding force may be well over what is required to hold the tanks in place but whenthe tanks are in a contracted phase the holding force may be sufficient but relatively weaker.Further, the distance elements may be deforrned or dislocated in course of time which also may have a negative effect on the holding force.

An example of a device for fastening a gas tank by means of a tensioning strap is disclosed byDE 10 2012 004 319 A1. The tensioning strap is wounded round the tank and two ends of thetensioning strap are connected to each other by means of a tensioning element with resilientproperties for shortening the tensioning strap when the tank is in its contracted phase.However, this known device has the disadvantage that the tensioning element has to be quitelong in order to maintain a sufficiently high holding force during the contracted phase and thatit in addition protrudes form the gas tank. A consequence of this is that the tensioning element reduces the space which otherwise would be available for gas tanks. 2 The space available for gas tanks is limited because of legal requirement specifying themaximum perrnissible vehicle width and by the fact that the gas tanks are not allowed toextend under a frame side member of the chassis as this would limit the possibilities ofrational production and service. The height is limited in the upward direction by the fact thatthe highest point of the gas tanks are not allowed to extend above the side frame member,otherwise it is difficult to fit bodyworks such as for examples load carriers to the vehicle andin downward direction by the requirement for adequate ground clearance. Further, the lengthmay be limited by the wheelbase of the vehicle and/or by components such as for examplesilencers and batteries in the event the tanks are mounted along the frame side member between the front wheels and the rear wheels.SUMMARY OF THE INVENTION One object of the present invention is to provide a solution in which the space mentioned isused as effectively as possible. An another object is to provide a fuel tank attaching structurewhich can cope with large diameter changes of the tanks but yet fixedly support them surely.

Those objects and other objects are achieved by the features mentioned in the claims.

The invention relates to a fuel tank attaching structure for a motor vehicle having at least oneexpandable and contractible fuel tank for storing compressed gas mounted thereon, the fueltank attaching structure comprising at least one bracket arranged to be fixed to a vehiclechassis for support of the at least one fuel tank, at least one tensioning strap arranged to bemounted around the fuel tank and at least one holding device arranged to operatively connectthe tensioning strap and the bracket, which holding device comprises a first fastening elementwith portions to extend through mutually opposite apertures in a channel-shaped portion ofthe bracket so as to fix the at least one tensioning strap to the bracket. The shape and size ofthe apertures are such as allow the first fastening element to be moved a distance in alongitudinal direction of the apertures and that the fuel tank attaching structure furthercomprises at least one spring means in the channel-shaped portion arranged to act between thefirst fastening element and the bracket whereby the spring means is arranged to apply aholding force of the tensioning strap to the gas tanks regardless of whether the gas tanks are inan expanded or contracted state by allowing the first fastening element to be moved in the longitudinal direction of the apertures. 3 Since the spring means is arranged in the channel-shaped portion of the bracket it is possibleto use one or several long and powerful spring means to achieve a sufficiently high holdingforce under all operating conditions Without reducing the space for fuel. Since the holdingdevice for the tensioning strap is movable in the longitudinal direction relative to the bracketit follows the diameter changes of the tanks Which results in high holding forces both in theeXpanded and in the contracted phase of the tank.

Preferably, the spring means comprises a number of cup springs stacked on each other. In thisWay it is possible to obtain an attaching structure With high holding forces in a small space.Further, by stacking the cup springs differently and use cup springs of different thickness andnumber it is possible to obtain different holding forces and spring characteristics in an advantageous manner.

Other features and advantages of the invention are apparent from the claims, the description of embodiments and the attached figures. 4BRIEE DESCRIPTION OF THE DRAWINGS The invention Will now be described in greater detail With reference to the appended drawings in which: Fig. l shows a schematic side view of a vehicle comprising a fuel tank attachingstructure.

Fig. 2 shows an end view of the fuel tank attaching structure in fig. l.

Fig. 3 shows a perspective view of a part of the fuel tank attaching structure according toone embodiment of the invention.

Fig. 4 shows a perspective view of a part of the fuel tank attaching structure according toone embodiment of the invention.

Eig. 5 shows a perspective view from the rear of the fuel tank attaching structure in fig 3.

Fig. 6 shows different combinations of cup springs.

DETAILED DESCRIPTION Fig. l shows a schematic side view of a motor vehicle l having a chassis 2 with two elongatedparallel side beams 3 which are connected to each other with a number of cross beams whichare not shown in the figure. At least one expandable and contractible fuel tank 4, in thisexample four gas tanks~4« for storing compressed gas, of which only two are visible from theside view are fastened to one of the side beams 3 by means of a fuel tank attaching structure 5comprising at least one but in this example three brackets 8 fixed to the chassis 2 forsupporting the at least one fuel tank 4 and at least one but in this example three tensioningstraps 7 around the at least one fuel tank 4 for fasten it to respective bracket 8. Eachtensioning strap 7 may be made of metal, preferably of steel. The vehicle l may be a heavyvehicle such as a truck or a bus. The fuel tank attaching structure 5 may also be referred to as a vehicle fuel tank attaching structure 5 or a vehicle fuel tank attachment structure 5.

In Fig. 2 an imaginary boundary line l0 is shown. The boundary line l0 surrounds a space llavailable for gas tanks~«+>š~. The space ll is limited because of legal requirement specifying themaximum perrnissible vehicle width and by the fact that the gas tanks-»äï are not allowed to extend under the side beam 3 as this would limit the possibilities of rational production and service. The height is limited in the upward direction by the fact that the highest point of the as tanks are not allowed to extend above the side beam 3, otherwise it is difficultto fit bodyworks such as for examples load carriers to the vehicle and in downward directionby the requirement for adequate ground clearance. Further, the length may be limited by thewheelbase of the vehicle and/or by extemal components 9 (fig. 1) such as for example silencers and batteries which may be mounted along the side beam 3 between the front wheels 12 and the rear wheels 13.

As can be seen in fig. 2, the outer surfaces 16 of the tanks 4 are supported by distanceelements 17 which fills the space between the tanks 4, between the tanks 4 and the tensioningstrap 7 and between the tanks 4 and the bracket 8. Each distance element 17 comprises a basesurface 18 and two support surfaces 19,20 each of which is adapted to lie against the outersurface 16 of a tank 4. Each distance element 17 is suitably an extruded aluminum profile.Two distance elements 17 are arranged between the tanks 4 in the centre of the space 11 withtheir base surfaces 18 facing each other and with their support surfaces 19,20 facing the outersurfaces 16 of the tanks 4. Four additional distance elements 17 are arranged with theirsupport surfaces 19,20 facing the outer surface 16 of the tanks 4 and their base surfaces 18facing the tensioning strap 7 or the bracket 8. Thus, the fuel tank attaching structure 5comprises six distance elements 17 supporting four tanks 4. In this way a stabile fuel tank structure may be provided.

The fuel tank attaching structure 5 may, which can be seen in fig. 2, include a first holdingdevice 23 which at its one end is engaged with an end portion being a first end loop 24 of thetensioning strap 7 and at its other end is engaged with a first free shank end 25 of the bracket8. The tensioning strap 7 at least partly encloses the tanks which rests on thebracket 8, which may be L-shaped. A second end loop 26 of the tensioning strap 7 opposite tothe one 24 connected to the first holding device 23 may be connected to the one end of asecond holding device 27 which other end is connected to a second free shank end 28 of thebracket 8. The tensioning strap 7 may be divided into a first strap part 14 and a second strappart 15 between which a tensioning device 29 may be arranged in order to draw the first strappart 14 and the second strap part 15 towards each other and thereby applying a holding forceby which the §as tanks are forced against a bearing surface 30 on the bracket 8.The tensioning device 29 may be a threaded connection with for example at least one threaded rod 21 which at its one end may be engaged with an end portion being a third end loop 32 of 6 the first strap part 14 and which at its other end may be engaged with an end portion being aforth end 1oop 33 of the second strap part 15. The threaded rod 21 may at each of its ends beconnected to a third and a forth pin 44,45, preferab1y c1evis pins extending through itscorresponding end 1oop 32,33. Further, spacers 31 e.g. rubber sheets may be arrangedbetween the tanks 4 and the bracket 8 and/or between the tanks 4 and the tensioning strap 7 orarranged to enc1ose at 1east a part of the tensioning strap 7 to protect the tanks 4 from beingchafed and/or to prevent s1ipping of the outer circumferentia1 surfaces of the gas--tan-ks--Åïfgaå taznks.

As can be seen in greater detai1 in Fig. 3, the first end 1oop 24 enc1oses a first pin 34,preferab1y a c1evis pin, which is part of the first ho1ding device 23 and which fits into firstthrough ho1es 35 at the end of a fork-shaped first part 36 of the first ho1ding device 23. Thepin 34 may have thinner portions c1ose to its ends for seating in the ho1es 35 so as to preventthe pin 34 from escaping from the ho1es 35. Locking rings, co11ars or simi1ar can a1so be usedfor this purpose. Further the pin 34 may extend through a second through ho1e 56 in asupporting portion 57 arranged between the ho1es 35 in order to support the pin 34 in its 1ongitudina1 direction.

At an opposite end of the first ho1ding device 23, there is a second part 37 with a third throughho1e 38 being para11e1 to the through ho1es 35 in the first part 36. The ho1e 38 in the secondpart 37 is adapted to receive a first fastening e1ement 39 which is part of the first ho1dingdevice 23 and having a 1ength to extend outside the width of the second part 37 and withportions c1ose to its ends to extend through mutua11y opposite e1ongated apertures 40 in achanne1-shaped portion 54 of the bracket 8 so as to fix the first ho1ding device 23, and thus thetensioning strap 7, to the bracket 8 a11owing the first ho1ding device 23 to pivot around saidfirst fastening e1ement 39. The shape and size of the apertures 40 may be such as a11ow thefirst fastening e1ement 39 to be moved a distance X (fig. 2) in a 1ongitudina1 direction of theapertures 40 and of the bracket 8. In other words, an extension of the apertures 40 in the1ongitudina1 direction exceeds an extension of the first fastening e1ements 39 in the1ongitudina1 direction. Thus, the apertures 40 may be arranged as s1its or s1ots into which thefastening e1ements 39 may be disp1aced. The first fastening e1ement 39 may be a second pin, preferab1y a c1evis pin.

Between the first part 36 and the second part 37 of the first ho1ding device 23, there is an intermediate part 41 which may be band- shaped or have any other e1ongated form suitab1e for 7 the application in point. In one embodiment the intermediate part 41 may be a threaded rodfor example, the one end of which is fastened to a first cylindrical body 34 placed with islongitudinal direction transversely to the longitudinal axis of the rod and which is engagedwith the end loop 24. The other end of the rod may be fastened to the first fastening element39 which may be cylindrical body 39 engaged with the bracket 8.

Fig. 4 shows a perspective view of a fuel tank attaching structure 5 according to secondembodiment of the invention where the tensioning strap 7 is attached to the first fasteningelement 39 without any intermediate part. The end loop 24 encloses the first fastening element39 which constitutes the first holding device 23 and having a length to extend outside thewidth of the tensioning strap 7 and with portions close to its ends to extend through themutually opposite apertures 40 in the channel-shaped portion 54 of the bracket 8 so as to fixthe tensioning strap 7 to the bracket 8 allowing it to pivot around said first fastening element39. The shape and size of the apertures 40 may be such as allow the first fastening element 39to be moved a distance X (fig. 2) in a longitudinal direction of the apertures 40 and of thebracket 8.

It is to be noted that, as can be seen in Fig. 2, there is a slight deviation between a direction ofan imagined plane 42 through the first holding device 23 and/or the end of the tensioningstrap 7 and the direction of an upper horizontal surface 43 of the ge-s--t-ank-s--ßleas tanks. Thecause of the deviation is that the fixing point in the bracket 8 for the first holding device 23 orthe end loop 24 of the tensioning strap 7 is positioned slightly below the upper surface 43 ofthe tanks in order to provide a downwards directed holding force.

As can be seen in fig. 3 and 4, each bracket 8 has an essentially U-shaped cross section and abottom member 5l adapted to face towards the šgas taaäkis, a pair of mutuallyopposite side members 52 perpendicular to the bottom member 5l and a pair of outwardlydirected flanges 53 parallel with the bottom member 5l and adapted to face towards the sidebeam 3. A number of through holes 22 for screws are formed in the flanges 53. Screws, whichare not shown in the figures, are used together with nuts to fix the bracket 8 to the side beam3. The bottom member 5l and the side members 52 forms a channel in the channel- shapedportion 54 which extends in the longitudinal direction of the bracket 8 between its first freeshank end 25 (fig. 2) and its second free shank end 28 (fig 2). The mutually opposite apertures 40 mentioned earlier are formed one in each side member 52. 8 Fig. 5 shows a perspective view from the rear of an fuel tank attaching structure 5. The firstfastening element 39 may be engaged with the first end loop 24 of the tensioning strap 7 as isshown in fig. 4 or with the second part 37 of the first holding device 23 as is shown in fig. 3,but in fig. 5 only the latter embodiment is shown. Further, the first end loop 24 (fig. 4) and thefirst holding device 23 (fig 5) may extend through an opening 47, preferably a U-shapedopening, in the bottom member 5 l. The opening 47 may be formed at the first- or at thesecond free shank end 25,28 of the bracket 8 or at the first- and at the second free shank end25,28 (fig. 2).

The diameter of each gas tank 4 may vary with the gas pressure in the tank 4. This is becausethe tanks 4 expands during a gas filling process when the gas pressure increases and contractsduring gas consumption when the gas pressure decreases. In order to ensure a sufficientholding force under all operating condition of a vehicle at least one second holding device 46is arranged in connection to at least one tensioning strap 7 but preferably in connection to alltensioning straps 7 in the fuel tank attaching structure 5 (fig. l). The second holding device 46may be arranged in the channel- shaped portion 54 of the bracket 8 and may be adapted toextend in its longitudinal direction. As can be seen in fig. 2 a second holding device 46 maybe provided at both the first free shank end 25 and at the second free shank end 28. In analternative embodiment, it is possible to provide a second holding device 46 at one free shank end 25,28 only and a conventional fastening device at the another free shank end 25,28.

Fig. 5 shows that in at least one bracket 8 but preferably in all brackets 8 there is a crosspiece60 extending across the channel-shaped portion 54 between the side members 52 and belowthe first fastening element 39. Although the crosspiece 60 may take the form of a machinedpart, such as for example a clevis pin, it is in this example made by a forging process for goodstrength. The crosspiece 60 may have a thickened middle portion 6l with a through hole 62and a pair of mutually opposite end spigots 63. The end spigots 63 may be adapted to beaccommodated in mutually opposite elongated second apertures 64 in the side members 52.The crosspiece 60 may have a substantially rectangular cross sectional shape and the shapeand size of the second apertures 64 may be such as to allow the crosspiece 60 to be insertedfrom the outside of the bracket 8. The crosspiece 60 can be inserted via said second apertures64, i.e. be inserted through a second aperture 64. According to an embodiment of theinvention the crosspiece 60 may be attached to the side members 52 in any other appropriate way, for example by welding. 9 At least one connector 67, e. g. a screw or a at least partially threaded rod or the like eXtendsdisplaceably through the hole 62 in the crosspiece 60. A first end of the connector 67 may bea U-shaped part 7l having a first shank 68 and a second shank 69 spaced apart from oneanother and arranged essentially parallel, both with through holes 70 through which the firstfastening element 39 is adapted to eXtend with its longitudinal direction transversely to thelongitudinal aXis of the connector 67. In an alternative embodiment, the U-shaped part 7l maybe a separate part that may be threaded onto a threaded rod or a threaded part of a screw 72. Ina further embodiment the upper part of the first- and second shanks 68,69 may be hook-shaped to at least partially enclose the first fastening element 39. The second part 37 of thefirst holding device 23 or the first end loop 24 (fig. 4) are adapted to eXtend through theopening 47 and between the first- and the second shank 68,69.

A second end of the connector 67 has a second fastening element 74 which for example maybe a nut or the head of a screw. At least one spring means 75 is arranged in the channel-shaped portion 54 and is acting between the first fastening element 39 and the bracket 8 whereby a spring load of the spring means 75 applies a holding force of the tensioning strap 7 tothe ”f so' as taraks regardless of whether the f * f . .t,__, f ' g as tarlks are expanded or notby allowing the first fastening element 39 to be moved in the longitudinal direction of theapertures 40. The spring means 75 may be arranged coaxially around the connector 67 andeXtends between the second fastening element 74 and a bottom part 66 of the crosspiece 60.The spring means 75 may for example be a helical spring, e. g. a compression spring, or anumber of cup springs stacked on each other or one or several gas springs. ln an altemativeembodiment, two or more spring means (75) may be arranged in parallel in the channelshaped portion 54. At least one washer 76 may be fitted between the second fastening element74 and the spring means 75 and/or between the spring 75 means and the crosspiece 60. Thespring means 75 may also be referred to as resilient means 75 since any spring-type, elasticelement or resilient element may be used for causing the holding force in the embodiments herein.

When cup springs are used it is possible to obtain an attaching structure with high holdingforces in a small space. Further, by stacking the cup springs differently and use cup springs ofdifferent thickness and number it is possible to obtain different holding forces and springcharacteristics in an advantageous manner. Fig. 6 shows a single cup spring 77, cup springs in parallel 82 i.e. cup springs laid one on the other, cup springs in series 83 i.e. cup springs laid one against another and a combination of cup springs in series and cup springs in parallel 84.All these formations have different spring characteristic. The cup springs in a forrnation maybe of identical dimensions but it is feasible to stack numbers of cup springs with differentthickness in order to achieve a stepped spring characteristic. For example, cup springs with increasing thickness may be stacked to receive progressive spring characteristics.

When cup springs are used in the fuel tank attaching structure in fig. 5 the cup springs may bestacked according to what is shown in fig. 6 or in any other way suitable for the application inquestion. In one preferred embodiment the cup springs may be stacked in series and parallel84 (fig. 6). Such a combination may consist of six packages each including l0 cup springs inparallel which packages are arranged in series. Such a combination may have a length of 40- 500 mm but preferably 40- l00 mm.

Fig 5 shows the fuel tank attaching structure 5 during operation. The tanka arein their contracted phase and are surrounded by the tensioning strap 7 which at its one end isfixed to the second free shank end 28 of the bracket 8 (fig. 2) and at its other end to the firstfastening element 39 via the first holding device 23. The portions close to the end of the firstfastening element 39 extends through the apertures 40 between a first end surface 79 and asecond end surface 80 of the aperture 40 and the end spigots 63 of the cross piece 60 extendsthrough the second apertures 64 and abuts against a third end surface 81 in the aperture 64.The holding force is adjustable by the connector 67, the second fastening element 74 andwhere appropriate by the tension device 29 (fig. 2) so that the spring means 75 is pressedtogether and brings about a suitable holding force in the longitudinal direction of theconnector 67 and of the tensioning strap 7 to the gas tztnks. The holding force maybe 30-45 kN. When the as tanks expands, the portion closed to the ends of thefirst fastening element 39 moves towards the first end surface 79 of the aperture 40 and thespring means 75 is pressed together and absorbs the expansion so that the tensioning strap 7can enlarge its diameter to fasten the sgas “tankas as before the expansion. During gasconsumption the taiilzs contracts and the ends of the first fastening element 39moves towards the second end surface 80 of the aperture 40 by spring force from the springmeans 75 which expands in the longitudinal direction of the connector 67 and tensions the tensioning strap 7 to fasten the tanks as before the contraction.

Claims (13)

1. l. A fuel tank attaching structure (5) for a motor vehicle (l) having at least one eXpandableand contractible fuel tank (4) for storing compressed gas mounted thereon, the fuel tankattaching structure (5) comprising at least one bracket (8) arranged to be fixed to a vehiclechassis (2) for support of the at least one fuel tank (4), at least one tensioning strap (7)arranged to be mounted around the fuel tank (4) and at least one holding device (23,27)arranged to operatively connect the tensioning strap (7) and the bracket (8), which holdingdevice (23,27) comprises a first fastening element (39) with portions to eXtend throughmutually opposite apertures (40) in a channel-shaped portion (54) of the bracket (8) so as tofix the at least one tensioning strap (7) to the bracket (8), characterised in that the shape andsize of the apertures (40) are such as allow the first fastening element (39) to be moved adistance (X) in a longitudinal direction of the apertures (40) and that the fuel tank attachingstructure (5) further comprises at least one spring means (75) in the channel-shaped portion(54) arranged to act between the first fastening element (39) and the bracket (8) whereby thespring means (75) is arranged to apply a holding force of the tensioning strap (7) to the fgeLtanks (4) regardless of whether the tanks (4) are in an eXpanded or contractedstate by allowing the first fastening element (39) to be moved in the longitudinal direction of the apertures (40).

2. A fuel tank attaching structure (5) according to claim l, characterised in that it comprisesa crosspiece (60) arranged to eXtend across the channel-shaped portion (54), at least oneconnector (67) eXtends displaceably through a hole (62) in the crosspiece (60), a first end ofthe connector (67) is connected to the first fastening element (39), a second end of theconnector (67) has a second fastening element (74) and the spring means (75) is adapted to eXtend between the second fastening element (74) and the crosspiece (60).

3. A fuel tank attaching structure (5) according to claim 2, characterised in that the spring means (75) is arranged coaxially around the connector (67).

4. 124. A fuel tank attaching structure (5) according to any one of claims l-3, characterised in that the spring means (75) comprises a number of cup springs (77) stacked on each other.

5. A fuel tank attaching structure (5) according to claim 4, characterised in that the cup springs (77) are stacked in series and substantially in parallel (84) relatively each other.

6. A fuel tank attaching structure (5) according to claim 4, characterised in that the length of the spring means is 40-500 mm.

7. A fuel tank attaching structure (5) according to claim l, characterised in that theapertures (40) are elongated between a first end surface (79) and a second end surface (80)and that the first fastening element (39) eXtends through the apertures (40) between the firstend surface (79) and the second end surface (80).

8. A fuel tank attaching structure (5) according to claim 2, characterised in that thecrosspiece 60 has a pair of mutually opposite end spigots (63) which are adapted to beaccommodated in mutually opposite second apertures (64) in the channel-shaped portion (54) of the bracket (8).

9. A fuel tank attaching structure (5) according to claim 8, characterised in that thecrosspiece (60) has a substantially rectangular cross sectional shape and that the shape andsize of the second apertures (64) are such as to allow the crosspiece (60) to be inserted from the outside of the bracket (8).

10. l0. A fuel tank attaching structure (5) according to claim 2, characterised in that a first endof the connector (67) comprises a U-shaped part (7l) having a first shank (68) and a secondshank (69) spaced apart from one another and arranged essentially in parallel to each other,both with through holes (70) through which the first fastening element (39) is adapted toeXtend with its longitudinal direction transversely to the longitudinal axis of the connector (67).

11. ll. A fuel tank attaching structure (5) according to any one of claim l,2,7 or l0, characterised in that the first fastening element (39) is a pin.

12. l2. A fuel tank attaching structure (5) according to claim 2, characterised in that the second fastening element (74) is a nut.