Seal, Especially for a Coupling Between an Air Intake on a Tilting Truck Cab and a Pipe Securely Mounted on the Chassis

The present invention relates to a device for establishing a tight communication between an air intake mounted on a spring-balanced tilting truck cab and a connecting pipe securely mounted on the truck chassis, comprising a hose of elastic material, which at least over a portion of its length has a wall folded in the form of a bellows, the hose having one end designed to be secured to a first tubular element and the other end designed to be detachably coupled to a second tubular element.

A seal of this type can be designed for example to prevent dust, water, snow and the like from penetrating into the intake conduit from the engine air filter. It must permit a resilient movement of the cab relative to the chassis without any risk to the sealing function. Furthermore, it must be easily detachable and connectable when tilting the cab upward down. Ideally, it should be detachable without any particular manipulation when the cab is tilted and returned to its original sealing position automatically when the cab is tilted back to its operational position.

Sealing devices known up to now for the stated purpose fulfill the requirements to varying degrees. One device consists of a simple rubber bellows which merely abuts against a flange on the connecting pipe when the cab is tilted from the forward position back to the operational position.

This seal does not require any particular manipulation to be detached and reconnected, but on the other hand the risk of leakage is great, especially if there is a great bouncing movement of the cab relative to the chassis. It is also known to fix an equally simple rubber bellows to the connecting pipe on the chassis with the aid of a hose clamp. This does provide an effective seal in all positions, but it does require extra manipulation for detaching and reconnecting.

In a third device, a spring is used which presses the rubber bellows against the connecting pipe. It is true that this seal does not require any extra manipulation when the cab is tilted, but it is relatively expensive and complicated.

A fourth known device uses permanent magnets embedded in the bellows, which hold the bellows tightly to the connecting pipe. This solution is relatively expensive and requires that the connecting pipe be made of magnetic material.

The purpose of the present invention is to achieve a sealing device of the type described by way of introduction which is uncomplicated and inexpensive and provides a completely satisfactory seal even if there is significant movement of the cab as well as being automatically uncoupled and recoupled when the cab is tilted forward and back.

This is achieved according to the invention by a device which is characterized in that the second end of the hose is provided on its inside with at least one annular lip inclined towards the first end of the hose and that the second tubular element is provided on its outside with at least one annular bead, which, when the hose is mounted, is disposed axially inside the lip, the hose and the second tubular element having interacting parts, abutting against each other and causing a compression of the folded portion when the tubular elements are moved towards each other. By virtue of this design with an inclined lip, the lower portion of the hose can be pressed with very little force over the bead on the chassis connecting pipe. Due to the direction of incline of the lip and the friction between the lip and the connecting pipe, however, a much greater force is required to pull the lip over the bead in the opposite direction, which means that the hose will be held securely in place and provide a fully satisfactory seal even during large cab movement. When the cab is tilted, however, this force is not so great as to present any problem in pulling the hose off the connecting pipe. An advantage of the design according to the invention over the known design with embedded magnets is that a secure coupling is achieved regardless of the material in the connecting pipe. It need not consist of a ferromagnetic material, but can be made of plastic for example.

The invention will be described in more detail below with reference to examples shown in the accompanying drawing. The FIGURE shows a side view in partial section of a sealing device.

The hose 1 shown in the FIGURE consists of a flexible material, e.g. rubber, and has a folded bellows portion 2, a connecting portion 3 and a connecting portion 4. The portion 3 has smooth interior and exterior lateral surfaces and is designed to be securely attached with the aid of a hose clamp to a connecting pipe (not shown), e.g. to an intake air filter mounted on a tiltable truck cab. The portion 4 is coupled to a connecting pipe 5 securely mounted on the chassis.

According to the invention, the portion 4 is provided with an interior annular lip 6, which is inclined axially inwards, i.e. in the direction of the end portion 3. Furthermore, the pipe 5 is provided at its end edge with a bead 7 of semicircular cross section, which when the hose has been mounted, is disposed axially inside the lip 6, as can be seen in the FIGURE. With this construction, the lip will provide relatively little resistance when the portion 4 is slipped on to the pipe 5. On the other hand, the lip will provide significantly greater resistance when the hose is pulled off the pipe 5, since the pressure of the lip against the pipe will increase when the lip strikes the bead. Only after the lip has been deformed enough to fold outwards can the hose be pulled off the pipe. The lip and the bead thus function as a sort of snaplock.

As can be seen in the FIGURE, the connecting portion 4 has a substantially greater wall thickness than the rest of the hose. A metal stiffener ring 8 is embedded in the wall, in order to ensure that the portion 4 will keep its shape adapted to the pipe end. The thickness of the material and the ring will provide weight to the portion 4 to keep the bellows extended when hanging free (cab tilted forward). This in addition to the height of the pipe 5 will ensure that when the cab is tilted back in place and the bellows is compressed against the bead, there will be sufficient force to snap the locking lip over the bead, i.e. so that the force to press the lip downwards over the bead will not be greater than the force required for a certain predetermined compression of the bellows portion 2 of the hose.

The bouncing movement of the cab is compensated for primarily by compression and expansion of the bellows portion 2. Axially inside the lip, there is a radial flange 9 which in the lower end position forms an abutment against the bead 7. To prevent the deposit of contaminents on the outside of the pipe 5, which could cause heavy wear on the lip 6 as it moves relative to the pipe, the hose portion 4 is provided at its lower end with an extra sealing lip 10 which is in contact with a radial flange 11 on the pipe 5. The length of the lip 10 is selected so that the edge of the lip rests against the flange 11 even when the lip 6 abuts against the lower edge of the bead 7.