Patent Description:
Pressure tanks with pressurized gas are used in many applications. Tanks are usually manufactured of materials having high strength against internal and external forces, such as of metal or composite materials. Such tanks can be used in vehicles that are driven with compressed natural gas (CNG). In vehicles, the tanks may be retained in tank assemblies comprising <NUM>-<NUM>, normally <NUM> cylindrical tanks. A tank assembly may be mounted to a chassis in a heavy vehicle, such as in a truck or a bus. In the assembly, the tanks may be held together in mounting brackets by means of distance elements filling the space between the tanks and tensioning straps surrounding the tanks. Relatively high holding forces from the tensioning straps are required to hold the tanks in place in the brackets. In heavy vehicles it may be difficult to keep sufficiently high holding forces during driving since the diameter of each tank varies with the gas pressure in the tank. This is because the tanks expands during a gas filling process when the gas pressure increases and contracts during gas consumption when the gas pressure decreases. A consequence of this is that when the tanks are in an expanded phase the holding force may be well over what is required to hold the tanks in place but when the tanks are in a contracted phase the holding force may be sufficient but relatively weaker. Further, the distance elements may be deformed 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 by <CIT>. The tensioning strap is wounded round the tank and two ends of the tensioning strap are connected to each other by means of a tensioning element with resilient properties 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 quite long in order to maintain a sufficiently high holding force during the contracted phase and that it 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.

The space available for gas tanks is limited because of legal requirement specifying the maximum permissible vehicle width and by the fact that the gas tanks are not allowed to extend under a frame side member of the chassis 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 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 and in downward direction by the requirement for adequate ground clearance. Further, the length may be limited by the wheelbase of the vehicle and/or by components such as for example silencers and batteries in the event the tanks are mounted along the frame side member between the front wheels and the rear wheels.

<CIT> discloses a connecting part intended for a tensioning device for tensioning belts, chains and the like. <CIT> discloses a restraining strap for securing pressure vessels.

One object of the present invention is to provide a solution in which the space mentioned is used as effectively as possible. An another object is to provide a fuel tank attaching structure which 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 one expandable and contractible fuel tank for storing compressed gas mounted thereon, the fuel tank attaching structure comprising at least one bracket arranged to be fixed to a vehicle chassis for support of the at least one fuel tank and at least one tensioning strap arranged to be mounted around the fuel tank and adapted to fasten the fuel tank to the bracket, which tensioning strap comprises a first end and a second end between which a tensioning device is arranged to apply a holding force of the tensioning strap to the gas tank. The tensioning device comprises at least one first fastening element which is adapted to be connected to the first end of the tensioning strap and a crosspiece having a first surface and a second surface, at least one second fastening element which is adapted to be connected to the second end of the tensioning strap and a crosspiece having a first surface and a second surface, the first fastening element and the second fastening element are adapted to be arranged with their first surfaces turned towards each other, at least one connecting element adapted to extend displaceably through a hole in each crosspiece between the first fastening element and the second fastening element, a first fastening member adapted to be connected to a first end of the connecting element, a second fastening element adapted to be connected to a second end of the connecting element and spring means adapted to extend between the first fastening member and the second surface and between the second fastening member and the second surface whereby the spring means is arranged to apply a holding force of the tensioning strap to the gas tanks regardless of whether the gas tanks are in an expanded or contracted state by allowing the first fastening element and the second fastening element to be moved in the longitudinal direction of the connecting element.

Since the spring means is part of the tensioning strap it is possible to achieve a sufficiently high holding force under all operating conditions without reducing the space for fuel. Since the tensioning strap is movable in its longitudinal direction it follows the diameter changes of the tanks which results in high holding forces both in the expanded and in the contracted phase of the tank.

Preferably, the spring means comprises a number of cup springs stacked on each other. In this way 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 and number 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.

The invention will now be described in greater detail with reference to the appended drawings in which:.

<FIG> shows a schematic side view of a motor vehicle <NUM> having a chassis <NUM> with two elongated parallel side beams <NUM> which are connected to each other with a number of cross beams which are not shown in the figure. At least one expandable and contractible fuel tank <NUM>, in this example four gas tanks <NUM> for storing compressed gas, of which only two are visible from the side view are fastened to one of the side beams <NUM> by means of a fuel tank attaching structure <NUM> comprising at least one but in this example three brackets <NUM> fixed to the chassis <NUM> for supporting the at least one fuel tank <NUM> and at least one but in this example three tensioning straps <NUM> around the at least one fuel tank <NUM> for fasten it to respective bracket <NUM>. Each tensioning strap <NUM> may be made of metal, preferably of steel. The vehicle <NUM> may be a heavy vehicle such as a truck or a bus. The fuel tank attaching structure <NUM> may also be referred to as a vehicle fuel tank attaching structure <NUM> or a vehicle fuel tank attachment structure <NUM>.

In <FIG> an imaginary boundary line <NUM> is shown. The boundary line <NUM> surrounds a space <NUM> available for gas tanks <NUM>. The space <NUM> is limited because of legal requirement specifying the maximum permissible vehicle width and by the fact that the gas tanks <NUM> are not allowed to extend under the side beam <NUM> 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 gas tanks <NUM> are not allowed to extend above the side beam <NUM>, otherwise it is difficult to fit bodyworks such as for examples load carriers to the vehicle and in downward direction by the requirement for adequate ground clearance. Further, the length may be limited by the wheelbase of the vehicle and/or by external components <NUM> (<FIG>) such as for example silencers and batteries which may be mounted along the side beam <NUM> between the front wheels <NUM> and the rear wheels <NUM>.

As can be seen in <FIG>, the outer surfaces <NUM> of the tanks <NUM> are supported by first distance elements <NUM> and a second distance element <NUM> which fills the space between the tanks <NUM>, between the tanks <NUM> and the tensioning strap <NUM> and between the tanks <NUM> and the bracket <NUM>. Each distance element <NUM>,<NUM> comprises support surfaces <NUM> each of which is adapted to lie against the outer surface <NUM> of a tank <NUM>. Each distance element <NUM>,<NUM> is suitably an extruded aluminum profile. The second distance elements <NUM> is arranged between the tanks <NUM> in the centre of the space <NUM> with four support surfaces <NUM> facing the outer surfaces <NUM> of the tanks <NUM>. Each of the first distance elements <NUM> is arranged at the edge of the space <NUM> with its support surfaces <NUM> facing the outer surface <NUM> of the tanks <NUM> and with a base surface <NUM> facing the tensioning strap <NUM> or the bracket <NUM>. Thus, the fuel tank attaching structure <NUM> comprises five distance elements <NUM>,<NUM> supporting four tanks <NUM>. In this way a stabile fuel tank structure may be provided. The tensioning strap <NUM> at least partly encloses the gas tanks <NUM> which rests on the bracket <NUM>, which may be L-shaped and which may be divided into a first strap part <NUM> and a second strap part <NUM>. A first end <NUM> of each strap part <NUM>,<NUM> may be engaged with one end of a holding device <NUM> which at its other end is engaged with a free shank end <NUM>,<NUM> of the bracket <NUM>. A second end <NUM> of each strap part <NUM>,<NUM> may be engaged with a tensioner <NUM> which is adapted to draw the first strap part <NUM> and the second strap part <NUM> towards each other and thereby applying a holding force by which the gas tanks <NUM> are forced against a bearing surface <NUM> on the bracket <NUM>. The tensioner <NUM> may be a threaded connection with for example at least one threaded rod <NUM> which at its one end may be engaged with the second end <NUM> of the first strap part <NUM> and which at its other end may be engaged with the second end <NUM> of the second strap part <NUM>. The threaded rod <NUM> may at each of its ends be connected to a pin <NUM>, preferably a clevis pin extending through its corresponding second end <NUM> with is longitudinal direction transversely to the longitudinal axis of the tensioning strap <NUM>. Further, spacers <NUM> e.g. rubber sheets may be arranged between the tanks <NUM> and the bracket <NUM> and/or between the tanks <NUM> and the tensioning strap <NUM> or arranged to enclose at least a part of the tensioning strap <NUM> to protect the tanks <NUM> from being chafed and/or to prevent slipping of the outer circumferential surfaces of the gas tanks <NUM>.

<FIG> shows a perspective view of the first end <NUM> of the first strap part <NUM>. The first end <NUM> of the second strap part <NUM> may be of similar design. The first end <NUM> encloses a first pin <NUM>, preferably a clevis pin, which fits into first through holes <NUM> in a first part <NUM> at the end of the holding device <NUM>. The pin <NUM> may have thinner portions close to its ends for seating in the holes <NUM> so as to prevent the pin <NUM> from escaping from the holes <NUM>. Locking rings, collars or similar can also be used for this purpose. At an opposite end of the holding device <NUM>, there is a second part <NUM> with a third through hole <NUM> being parallel to the through holes <NUM> in the first part <NUM>. The hole <NUM> in the second part <NUM> is adapted to receive a second pin <NUM>, preferably a clevis pin which is part of the holding device <NUM> and having a length to extend outside the width of the second part <NUM> and with portions close to its ends to extend through mutually opposite apertures <NUM> in a channel-shaped portion <NUM> of the bracket <NUM> so as to fix the holding device <NUM>, and thus the tensioning strap <NUM>, to the bracket <NUM> allowing the holding device <NUM> to pivot around said second pin <NUM>. Between the first part <NUM> and the second part <NUM> there is an intermediate part <NUM> which may be band-shaped or have any other elongated form suitable for the application in point. Further, the holding device <NUM> may extend through an opening <NUM>, preferably a U-shaped opening, in the bracket <NUM>. The opening <NUM> may be formed at the first- or at the second free shank end <NUM>,<NUM> of the bracket <NUM> or at the first- and at the second free shank end <NUM>,<NUM> (<FIG>).

It is to be noted that, as can be seen in <FIG>, there is a slight deviation between a direction of an imagined plane <NUM> through the holding device <NUM> and the direction of an upper horizontal surface <NUM> of the gas tanks <NUM>. The cause of the deviation is that the fixing point in the bracket <NUM> for the holding device <NUM> is positioned slightly below the upper surface <NUM> of the gas tanks <NUM> in order to provide a downwards directed holding force.

As can be seen in <FIG>, each bracket <NUM> has an essentially U-shaped cross section and a bottom member <NUM> adapted to face towards the gas tanks <NUM>, a pair of mutually opposite side members <NUM> perpendicular to the bottom member <NUM> and a pair of outwardly directed flanges <NUM> parallel with the bottom member <NUM> and adapted to face towards the side beam <NUM>. A number of through holes <NUM> for screws are formed in the flanges <NUM>. The screws, which are not shown in the figure, are used together with nuts to fix the bracket <NUM> to the side beam <NUM>. The bottom member <NUM> and the side members <NUM> forms a channel in the channel-shaped portion <NUM> which extends in the longitudinal direction of the bracket <NUM> between its first free shank end <NUM> and its second free shank end <NUM> (<FIG>). The mutually opposite apertures <NUM> mentioned earlier are formed one in each side member <NUM> and the opening <NUM> also mentioned earlier is formed in the bottom member <NUM>.

The diameter of each gas tank <NUM> in <FIG> may vary with the gas pressure in the tank <NUM>. This is because the tanks <NUM> expands during a gas filling process when the gas pressure increases and contracts during gas consumption when the gas pressure decreases. In order to ensure a sufficient holding force under all operating condition of a vehicle at least one tensioning device <NUM> is arranged at at least one tensioning strap <NUM> but preferably at all tensioning straps <NUM> in the fuel tank attaching structure <NUM> (<FIG>). Each tensioning strap <NUM> is tensioned by means of the tensioning device <NUM> which is adapted to connect the first end <NUM> and the second end <NUM> of the tensioning strap with each other and which may be adapted to extend in the longitudinal direction of the tensioning strap <NUM>. In the case the tensioning strap <NUM> is divided into a first strap part <NUM> and a second strap part <NUM>, at least one tensioning device <NUM> may be provided at both the first strap part <NUM> and the second strap part <NUM> as shown in the <FIG>. In an alternative embodiment, it is possible to provide at least one tensioning device <NUM> at one strap part <NUM>,<NUM> only. In a further embodiment, at least one tensioning strap <NUM> may extend around the gas tanks <NUM> between two brackets <NUM>. At least one tensioning device <NUM> may in this case be provided at a strap part facing the side beam <NUM> and/or provided at a strap part facing the ground on which the vehicle is placed. Each tensioning device <NUM> may comprise a first fastening element <NUM>, a second fastening element <NUM> and a gap <NUM> between them. The gap <NUM> gets wider when the tanks <NUM> expands and narrower when the tanks <NUM> contracts. This results in that the tensioning strap <NUM> follows the diameter changes of the tanks <NUM> and in high holding forces both in the expanded and in the contracted phase of the tanks <NUM>.

<FIG> shows an exploded view of a the first strap part <NUM>. The second strap part <NUM> (<FIG>) and a strap part facing the side beam <NUM> and/or the ground may be of similar design. Further, <FIG> shows that the tensioning devise <NUM> may comprise at least one first fork-shaped fastening element <NUM> and at least one second fork-shaped fastening element <NUM>. Each fastening element <NUM>,<NUM> may comprise at least two, but in this example four, shanks <NUM> spaced apart from one another and arranged essentially in parallel to each other. The shanks <NUM> are connected to each other by a crosspiece <NUM>. The shanks <NUM> and the crosspiece <NUM> defines a u-shaped space <NUM> through which at least one spring means <NUM> extends. In an alternative embodiment, it is possible to let two or more spring means <NUM> extend side by side in one and the same U-shaped space <NUM>. The shanks <NUM> are adapted to at least partly extend along corresponding shanks <NUM> at the first end <NUM> of each strap part <NUM>,<NUM> and at the second end <NUM> of each strap part <NUM>,<NUM> and comprises through holes <NUM> at their free ends which are adapted to aligned with corresponding through holes <NUM> at the first end <NUM> and at the second end <NUM>. Pins <NUM>,<NUM> preferably clevis pins, are adapted to extend through the holes <NUM>,<NUM> with its longitudinal direction transversely to the longitudinal direction of the tensioning device <NUM> to connect the first fastening element <NUM> pivotally to the first end <NUM> and the second fastening element <NUM> pivotally to the second end <NUM>. The pins <NUM>,<NUM> may have thinner portions close to their ends for seating in the holes <NUM>,<NUM> so as to prevent the pins <NUM>,<NUM> from escaping from the holes <NUM>,<NUM>. Locking rings, collars or similar can also be used for this purpose. Further, <FIG> shows that the second end <NUM> may comprise an U-shaped end having two shanks <NUM> spaced apart from one another and arranged essentially parallel, both with through holes <NUM> through which the pin <NUM> (<FIG>) is adapted to extend. <FIG> also shows that the first end <NUM> may be connected to the holding devise <NUM> by the first pin <NUM>, which holding device <NUM> in turn may be connected to the bracket <NUM> by the second pin <NUM> (<FIG>). In an alternative embodiment the first end <NUM> may be connected to the first and/or the second free shank <NUM>,<NUM> (<FIG>) without any intermediate holding devise <NUM>. The spring means <NUM> may also be referred to as resilient means <NUM> since any spring-type, elastic element or resilient element may be used for causing the holding force in the embodiments herein.

As can be seen in <FIG>, which shows a longitudinal section in the plane A-A in <FIG> when the fuel tanks <NUM> are in their expanded phase, each crosspiece <NUM> comprises a through hole <NUM>, a first surface <NUM> and a second surface <NUM>. The first fastening element <NUM> and the second fastening element <NUM> are arranged with the first surfaces <NUM> turned towards each other and with their holes <NUM> aligned with each other. A connecting element <NUM>, e.g. a screw or a at least partially threaded rod or the like extends displaceably through the holes <NUM> in the crosspiece <NUM>, between the first fastening element <NUM> and the second fastening element <NUM>. A first end of the connecting element <NUM> has a first fastening member <NUM> which for example may be a nut or the head of a screw. A second end of the connecting element <NUM> has a second fastening member <NUM> which for example may be a nut or the head of a screw. The nuts may be selflocking nuts. At least one spring means <NUM> is arranged in each fastening element <NUM>,<NUM> and is acting between the first end <NUM> and the second end <NUM> of the tensioning strap <NUM> (<FIG>) whereby a spring load of the spring means <NUM> applies a holding force of the tensioning strap <NUM> to the gas tanks <NUM> regardless of whether the gas tanks <NUM> are expanded or not by allowing the first fastening element <NUM> and the second fastening element <NUM> to be moved along the connecting element <NUM> in its longitudinal direction and thereby increase or decrease the gap <NUM> between the first- and the second fastening element <NUM>,<NUM> when the diameter of the tanks <NUM> changes. The spring means <NUM> may be arranged coaxially around the connecting element <NUM> and extends between the second surfaces <NUM> and the fastening members <NUM>,<NUM>. The spring means <NUM> may for example be a helical spring, e.g. a compression spring, or a number of cup springs stacked on each other or one or several gas springs. At least one washer <NUM> may be fitted between the spring means <NUM> and the fastening members <NUM>,<NUM>.

In <FIG> corresponding surfaces and parts of the first and second fastening elements <NUM>, <NUM> are denominated with same reference numbers <NUM>, <NUM>, <NUM>, <NUM>, <NUM> for facilitated reading. The surfaces and parts related to the first fastening element <NUM> may alternatively be denominated with reference numbers <NUM>', <NUM>', <NUM>', <NUM>', <NUM>' and the surfaces and parts related to the second fastening element <NUM> may alternatively be denominated with reference numbers <NUM>", <NUM>", <NUM>", <NUM>", <NUM>".

When cup springs are used 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 and number it is possible to obtain different holding forces and spring characteristics in an advantageous manner. <FIG> shows a single cup spring <NUM>, cup springs in parallel <NUM> i.e. cup springs laid one on the other, cup springs in series <NUM> i.e. cup springs laid one against another and a combination of cup springs in series and cup springs in parallel <NUM>. All these formations have different spring characteristic. The cup springs in a formation may be of identical dimensions but it is feasible to stack numbers of cup springs with different thickness 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> the cup springs may be stacked according to what is shown in <FIG> or in any other way suitable for the application in question. In one preferred embodiment, for example the one in <FIG>, the cup springs may be stacked in series and parallel <NUM>. Such a combination may consist of six packages <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM> each including <NUM> cup springs in parallel, which packages are arranged in series. Such a combination may have a length of <NUM>-<NUM>.

<FIG> and <FIG> shows the tensioning device <NUM> when the gas tanks <NUM> are in their contracted phase and surrounded by the tensioning strap <NUM>. The gap <NUM> between the first fastening element <NUM> and the second fastening <NUM> may be relatively small or absent. The spring means <NUM> brings about a suitable holding force in the longitudinal direction of the tensioning strap <NUM> to the gas tanks <NUM>. The holding force may be <NUM>-<NUM> kN. When the gas tanks <NUM> expands, the first fastening element <NUM> and the second fastening element <NUM> moves away from one another in the longitudinal direction of the connecting element <NUM>. The gap <NUM> expands as can be seen in <FIG> and the spring means <NUM> are pressed together and absorbs the expansion so that the tensioning strap <NUM> can enlarge its diameter to fasten the gas tanks <NUM> as before the expansion. During gas consumption the gas tanks <NUM> contracts and the first fastening element <NUM> and the second fastening element <NUM> moves towards each other in the longitudinal direction of the connecting element <NUM> by spring force from the spring means <NUM> which expands and tensions the tensioning strap <NUM> to fasten the gas tanks <NUM> as before the contraction.

Claim 1:
A fuel tank attaching structure (<NUM>) for a motor vehicle (<NUM>) having at least one expandable and contractible fuel tank (<NUM>) for storing compressed gas mounted thereon, the fuel tank attaching structure (<NUM>) comprising at least one bracket (<NUM>) arranged to be fixed to a vehicle chassis (<NUM>) for support of the at least one fuel tank (<NUM>) and at least one tensioning strap (<NUM>) arranged to be mounted around the fuel tank (<NUM>) and adapted to fasten the fuel tank (<NUM>) to the bracket (<NUM>), which tensioning strap (<NUM>) comprises a first end (<NUM>) and a second end (<NUM>) between which a tensioning device (<NUM>) is arranged to apply a holding force of the tensioning strap (<NUM>) to the gas tank (<NUM>), characterised in that the tensioning device (<NUM>) comprises at least one first fastening element (<NUM>) which is adapted to be connected to the first end (<NUM>) of the tensioning strap (<NUM>) and a crosspiece (<NUM>) having a first surface (<NUM>) and a second surface (<NUM>), at least one second fastening element (<NUM>) which is adapted to be connected to the second end (<NUM>) of the tensioning strap (<NUM>) and a further crosspiece (<NUM>) having a first surface (<NUM>) and a second surface (<NUM>), the first fastening element (<NUM>) and the second fastening element (<NUM>) are adapted to be arranged with their first surfaces (<NUM>) turned towards each other, at least one connecting element (<NUM>) adapted to extend displaceably through a hole (<NUM>) in each crosspiece (<NUM>) between the first fastening element (<NUM>) and the second fastening element (<NUM>), a first fastening member (<NUM>) adapted to be connected to a first end of the connecting element (<NUM>), a second fastening member (<NUM>) adapted to be connected to a second end of the connecting element (<NUM>) and spring means (<NUM>) adapted to extend between the first fastening member (<NUM>) and the second surface (<NUM>) and between the second fastening member (<NUM>) and the second surface (<NUM>) whereby the spring means (<NUM>) is arranged to apply a holding force of the tensioning strap (<NUM>) to the gas tanks (<NUM>) regardless of whether the gas tanks (<NUM>) are in an expanded or contracted state by allowing the first fastening element (<NUM>) and the second fastening element (<NUM>) to be moved in the longitudinal direction of the connecting element (<NUM>).