GB2299380A - Vehicle air compressor - Google Patents

Abstract

A vehicle compressor comprises an electrically operated compressor (16) driven by a motor (14) arranged to be connected to the vehicle's electrical supply, output supply means (22) from the compressor for attachment to a vehicle tyre to inflate the tyre and pressure release valve means (42) subject to the output pressure from the compressor. The release means comprises a moveable valve urged by resilient means against a valve seat, a housing defining an enclosure into which air from the pressure release valve releases; and means for adjusting the pressure at which the release valve means opens. Adjustment is via a knob (56) mounted so as to be rotatably movable over a planar surface of the housing which carries a pressure - calibrated scale. Means (76) which detect the release of air into the enclosure (64) are arranged to de-energise the motor.

Description

VEHICLE AIR COMPRESSOR This invention relates to an air compressor for inflating or re-inflating the pneumatic tires of vehicles.

Such compressors are well-known and generally comprise an electric motor which drives a suitable air compressor using the electrical energy from the vehicle's own electrical supply system. This is usually achieved by means of a plug which can fit into the cigar lighter of a vehicle to connect the compressor to the vehicle's battery.

A pressure gauge can be provided on the outlet line from the compressor so that the user can judge the air pressure to which the tyre is being inflated. This requires careful attention on the part of the user, however, to watch the pressure and ensure that he stops the inflation at the right moment.

It is an object of the present invention to avoid this problem and to allow the user to readily pre-set a desired inflation pressure and have the compressor stop at that point.

According to the invention, there is provided a vehicle compressor comprising an electronically operated compressor driven by a motor arranged to be connected to the vehicle's electrical supply, output supply means from the compressor for attachment to a vehicle tyre to inflate the tyre, pressure release valve means subject to the output pressure from the compressor comprising a moveable valve urged by resilient means against a valve seat, a housing defining an enclosure into which air from the pressure release valve releases; means for adjusting the pressure at which the release valve means release comprising a rotary knob mounted so as to be rotatably movable over a planar surface of the housing which carries a pressure - calibrated scale; and means for detecting the release of air into the enclosure and de-energising the motor.

In a preferred embodiment the means for detecting the release of air into the enclosure comprise an outlet, a movable closure for the outlet, resilient means urging the closure to close the outlet, and electrical contact means movable by the movable closure, movement of the electrical contact de-energising the electric motor.

Preferably, the resilient means bears against an intermediate element which is movable relative to the housing on rotation of the knob, the knob is provided with a threaded shaft portion fixed thereto, and the intermediate element includes an internal thread, the intermediate element and the housing being adapted to allow only axial movement relative the housing as the knob is rotated. The housing defines an upstanding cavity portion in which the intermediate element is arranged, said upstanding portion being of complementary non-circular shape, to prevent relative rotation.

With such an arrangement, the user can pre-set a desired inflation pressure by means of the rotary knob; the pressure can be readily set by aligning an appropriate part of the knob with the desired pressure on the calibrated scale. Once this desired pressure is reached, the device will automatically stop at this point.

The pressure release valve can comprise a spring loaded plunger closing an inlet from the output supply, the load on the spring being adjustable so as to pre-set the pressure at which the valve will release. Then that valve may be placed in the sealed enclosure such that release of air into the enclosure by lifting of the valve will cause a flow of air out from the sealed enclosure which will in turn actuate an electrical contact. Then the completion of the circuit by that electrical contact can be used to deactivate the motor. By way of an example, this can be achieved using a relay whose coil becomes energised by the completion of a circuit by the contact and current can flow to the switch contact and retaining the energisation of the coil until the user is ready to start the operation again.

Preferably, the pressure release valve means is adapted to be locked in a closed position in which said movable valve is prevented from movement out of said valve seat. The intermediate element is movable into a position in which it abuts said valve means on rotation of said knob, in order to lock the valve means against the valve seat. This allows the valve to be locked and the pressure release valve means to be internally pressurized to a higher internal pressure than would normally be applied to a tire, for testing purposes.

The invention will now be described by way of an example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic view of a car tyre compressor according to the invention; Figure 2 is an enlarged detail showing the pressure release valve; Figure 3 is a further enlarged detail of the pressure release valve when actuated; Figure 4 is a circuit diagram of the wiring in the compressor; Figure 5 is a view of the top of the pressure release valve, showing the graduated scale; Figure 6 shows the pressure release valve in a by pass condition; Figure 7 is a top view of the pressure release valve in a by pass condition; Figure 8 is an enlarged detail of an end region of the pressure release valve in a closed condition; and Figure 9 is an enlarged detail of an end region of the pressure release valve in an actuated condition.

The car compressor unit 10 as shown in the drawings includes an outer casing 12 in which is housed an electrical motor 14 driving a compressor 16. The motor drives the compressor through a reduction gear box 20 (not shown in detail) and the motor and compressor unit are well-known from widely used car compressor units of this type and are not believed to need further explanation or description.

The compressor has an outlet tube 22 on the end of which is a conventional fitting 24 for attachment to a pneumatic tyre. When the compressor operates and the fitting is attached to the tyre, the tyre can be inflated.

The electric motor 14 is actuated by a vehicle's cigar lighter and includes a plug 26 of conventional construction. This has a central resilient contact 28 constituting a first terminal, and a radially resilient contact 30 constituting a second terminal, for obtaining the supply of electrical energy from the vehicle's battery.

Plug 26 is attached to the unit 12 by means of an electrical cord 32.

A branch tube 40 extends from the compressor outlet to a pressure detection valve unit 42. This unit is best shown in Figure 2 and includes an inlet connector 44 attached to the tube 40 whose end is closed by a valve pin 46. This sits tightly in the end of the inlet 44 and is urged tightly into the inlet 44 by a spring 48. The valve pin 46 is integrally formed with a hollow cylinder 50 in which the end of the coil spring is positioned and so that the coil spring can urge the pin 46 downwardly in the sense viewed in Figures 2 and 3 so as to close the inlet 44. Figure 8 is an enlarged view showing the pin 46 and valve seat.

The inlet 44 forms part of a cylindrical housing 52 comprising a lower housing part 53 which, as seen in Figure 5, has an outer threading 54. Threaded onto this is an upper housing part 56 with an inner threading 60. As best seen in Figure 2, the upper planar surface of the upper housing part 56 has graduations corresponding to the pressure at which the valve is to operate.

The upper housing part 56 is provided with an upstanding central region 57 on which is supported a knob 58. Knob 58 carries a central threaded shaft 60 which extends through a central threaded aperture of an intermediate element in the form of a nut 62.

The upstanding central region 57 and nut 62 have a complementary shape, and are adapted such that the nut 62 may move only axially within the central region 57 and may not rotate therein, for example, the region 57 and nut 62 may both be of non-circular shape, such as of hexagonal shape, or alternatively, the region 57 may include splines and the nut 52 corresponding grooves to prevent rotation.

Accordingly, the further the knob 58 is screwed in a clockwise sense relative the housing 52, the more the spring 48 is compressed and therefore the greater the force with which the spring forces the pin 46 to close the inlet 44 and vice versa. The user can therefore dial in a required pressure by twisting the knob 58 so that an indicating mark thereon is aligned with pressure graduations or calibrations on the upper end face of the housing. Then when the pressure in the inlet 44 reaches that pre-set position, it will have sufficient force to overcome the force of the spring 48 and the pin 46 will be moved upwardly as is shown in Figure 3 and Figure 9 against the action of spring 48. The arrangement of a knob 58 which is moved over the generally planar upper surface of the housing allows the pressure to be very easily set.

The housing 52 defines an enclosed space 64 from which there is only one outlet, namely an outlet opening 66.

This opening is normally closed by means of a valve 68.

The latter is in the form of a flat head 68a with an integral shaft 68b, indicated in Figure 3 and seen more clearly in Figures 8 and 9. A coil spring 70 urges the head 68a into a sealing position with the outlet 66. The spring however does not need to be particularly strong or accurately calibrated since its objective is solely to keep the head 68a normally against the inlet 66 and to close it.

However, once pressurized air escapes from the inlet 44 because the pin 46 is displaced, the resulting air will readily overcome the force of the spring 70 and escape through the opening outlet 66 so moving the valve 68.

The shaft 68k is in contact with a resilient electrical arm 72. This arm originates from one contact 74, and insulated from the contact 74 is a second contact 76. As soon as the valve 68 lifts however, the shaft 68t presses the arm 72 into electrical contact with the contact 76.

Referring to Figure 3 or 9, as soon as the arm 72 completes the circuit with the contact 76, current is supplied to the coil 80 of a solenoid 82. The solenoid 82 controls a switch contact 84. This is normally in the "off" position and completes, via a contact 86, the circuit to the electric motor 14. Accordingly, as soon as an on/off switch 88 is actuated the motor will work. However, once the solenoid coil 80 is energised as described above, it will move the switch 84 to the contact 90, so opening the circuit to the motor and de-energising it. Now even though the arm 72 ceases to make contact with the contact 76, the circuit to the solenoid coil 80 is still completed through the switch 84 and contact 90.

Therefore, when a pre-set pressure is reached and the pin 46 raises, air will release through the outlet 66 so displacing the valve 68a, momentarily at least causing the arm 72 to contact the contact 76.

This energises the coil 80 and immediately de-activates the motor and therefore stops further pressurization of the tyre. Also, this maintains the energisation of the coil 80 via the switch 84 and contact 90 so preventing the switch 84 returning to re-energise the motor.

If the user has then finished he can un-couple the plug 26 from the car and this will cause the de-energisation of the coil 80, so releasing the switch 84 and re-setting this ready for use. As an alternative, if the user wishes to inflate another tyre, he merely has to operate the on-off switch 88 which then automatically re-sets everything ready to inflate the new tyre.

The pressure to which the tyre is to be inflated can very quickly and easily be pre-selected by rotating the knob 58 to the desired pressure release value.

The compressor is also adapted to allow internal pressurisation of the unit 46 to a pressure in excess of a value which would be used for pressuring a tyre, in the manner as now described. As seen in Figure 2 or 3, in a normal operating condition there is a clearance between the upper end 92 of the cylinder 50 and the nut 62 so that as the output pressure in the line 40 exceeds the set pressure, the cylinder 50 can move upwardly, opening the inlet 44. Figures 6 and 7 show a "bypass" condition in which the knob 58 is turned in a clockwise direction until the indicating mark 59 is aligned with the word "BYPASS", so that the lower surface of the nut 62 abuts the upper end 92 of the cylinder 50, thereby locking the cylinder in position. This allows the valve unit 42 to be internally pressurized to an excess pressure, for example through inlet 66, in a pressure test.

Claims (8)

1. A vehicle compressor comprising an electronically operated compressor driven by a motor arranged to be connected to the vehicle's electrical supply, output supply means from the compressor for attachment to a vehicle tyre to inflate the tyre, pressure release valve means subject to the output pressure from the compressor comprising a moveable valve urged by resilient means against a valve seat, a housing defining an enclosure into which air from the pressure release valve releases; means for adjusting the pressure at which the release valve means release comprising a rotary knob mounted so as to be rotatably movable over a planar surface of the housing which carries a pressure - calibrated scale; and means for detecting the release of air into the enclosure and de-energising the motor.

2. A compressor as claimed in claim 1 wherein the means for detecting the release of air into the enclosure comprise an outlet, a movable closure for the outlet, second resilient means urging the closure to close the outlet, and electrical contact means movable by the movable closure, movement of the electrical contact de-energising the electric motor.

3. A compressor as claimed in claim 2, further comprising a relay including a coil and switch contacts movable by the coil, in which movement of the electrical contact by the movable closure completes a circuit to energise the coil, whereupon the such contacts de activate the motor and maintain energisation of the coil.

4. A compressor as claimed in claim 1, 2 or 3 wherein the resilient means bears against an intermediate element which is movable relative to the housing on rotation of the knob, the knob is provided with a threaded shaft portion fixed thereto, and wherein the intermediate element includes an internal thread, the intermediate element and the housing being adapted to allow only axial movement relative the housing as the knob is rotated.

5. A compressor as claimed in claim 4 wherein the housing defines an upstanding cavity portion in which the intermediate element is arranged, said upstanding portion being of complementary non-circular shape, to prevent relative rotation.

6. A compressor as claimed in any proceeding claim wherein said pressure release valve means is adapted to be locked in a closed position in which said movable valve is prevented from movement out of said valve seat.

7. A compressor as claimed in claim 6 as appendant to claim 4 wherein said intermediate element is movable into a position in which it abuts said valve means on rotation of said knob, in order to lock the valve means against the valve seat.

8. A vehicle compressor substantially as herein described with reference to the accompanying drawings.