GB2047516A

GB2047516A - Electronically-locked reel

Info

Publication number: GB2047516A
Application number: GB7914278A
Authority: GB
Original assignee: Proctor R A
Current assignee: Proctor R A
Priority date: 1979-04-24
Filing date: 1979-04-24
Publication date: 1980-12-03

Abstract

A safety belt reel which normally allows paying out of a strap of the belt, but which is locked following production of an electrical signal, or a change in an electrical signal, by an electric or electronic transducer when the latter experiences a deceleration greater than a predetermined value.

Description

SPECIFICATION Electronically-locked reel This invention relates to a safety belt reel which normally operates to allow paying out of a strap of the belt against the force of a retracting spring of the reel to allow the wearer freedom of forward movement but which locks in the event of sudden deceleration of the vehicle in which the reel is fitted to prevent the wearer being thrown forward. The reel can be made to lock as a result of irregular movement of the strap, or of the vehicle, or both.

Hitherto, irregular movement of the vehicle has been sensed by the movement of a pendulum, ball or other inertial mass acting solely through a mechanical coupling to effect locking of the reel. One disadvantge of such a locking mechanism is that, if the vehicle is on a slant, for example due to the slope of a hill or camber in the road, the reel may lock even though the vehicle is not suddenly decelerating. This may result in the driver or a passenger of the vehicle being unable to fit the safety belt at the start of his journey.

It is an aim of the present invention to provide a remedy. Accordingly, the present invention is directed to a safety belt reel comprising a locking member which is movable between a free position, permitting the reel to operate for paying out a strap of the belt, and a locking position in which the reel is prevented from paying out the strap, and an electric or electronic transducer, (as defined herein) capable of producing an electrical signal or a change in an electrical signal in response to deceleration it experiences, which signal is used to actuate, or to initiate actuation of, means for moving the locking member into its locking position when the deceleration is greater than a predetermined value.

The term "transducer" is used herein to mean a component or apparatus which comprises or includes electronic means. As such, it can take many different forms. Normally, however, it will comprise one or more micro processors, crystals, or chips. Alternatively, it could be a mechanical, electrical, electronic or other sensor which incorporates, or is combined with, such electronic means. Preferably, the transducer will respond to deceleration in any direction, so that the reel will operate equally well whichever way up it is installed in the vehicle. For example, the transducer may comprise three components arranged to deliver electrical signals in response to deceleration respectively in three mutually perpendicular directions. The signals can be delivered to electronic circuitry constructed to calculate the magnitude of the actual deceleration from these three signals.

The means for moving the locking member into its locking position can be actuated electronically, electrically, hydraulically, pneumatically or mechanically.

An example of a safety belt reel in accordance with the invention is shown in the accompanying drawings, in which Figure 1 is an exploded perspective view of the reel; Figure 2 is a perspective view of an end portion of the reel shaft and an end-plate keyed thereto; Figure 3 is another end view of the reel shaft; Figure 4 is a perspective view of the frame of the reel; Figure 5 shows in greater detail a front view of a flywheel of the reel, the periphery of which flywheel is acted on by a stop; Figure 6 shows diagrammatically a transducer device of the reel; and Figure 7 shows circuitry associated with the transducer device.

The illustrated safety belt reel comprises a safety belt 10 of flexible webbing material having a fastening member 1 2 at its free end.

The belt is wound on a reel shaft 1 4 and is firmly secured to the latter at its inner end.

The shaft 14 is supported at its ends by a frame 1 6 (see Fig. 4) comprising a member 1 8 of channel section and two wall retaining pins 20. The two opposing walls 22 and 24 of the member 1 8 are held "square" to each other, i.e., in exact parallelism, by the pins 20 which have notches 26 near their ends for reception, as a tight fit, in respective grooves 28 in the outer edge portions of the walls 22 and 24. The pins 20 are thus securely keyed to the walls. This is in contrast to screwthreaded pins and nuts used hitherto.

As shown in Fig. 2, one end portion 30 of the reel shaft 14 carries, as a separate component, an end-plate 32. This end plate 32 has a central opening in it so that, during assembly of the reel, a first end of the shaft (not shown) can be passed through the opening, and the end plate can be moved axially along the shaft to the other end 30 thereof so as to occupy an end position (Fig. 2) in which cooperating abutments described below prevent the end plate 32 from moving axially beyond the said end 30 of the shaft and also prevent the end plate from rotating with respect to the shaft.

As shown in Fig. 3, the extreme end 40 of the shaft 1 4 has an integral out-turned flange 42 which, in the position shown in Fig. 2, engages the end plate 32 around the opening therein. That end face of the plate shown in Fig. 1 has a recess 33 which extends around the opening in the end plate, this recess 33 serving to receive the flange 42, with flange 42 engaging flange 35 on the end plate. The end plate has a recess 34 into which a projection 37 on the shaft fits to prevent relative rotation between the shaft and the end plate. The inner face 36 of the end plate is formed with three shallow cups 38 at 120 intervals to receive balls (not shown).

Carried on the shaft 14 adjacent the end plate 32 is a flywheel 44. The face 46 of the flywheel opposing the face 36 of the end plate is formed, like the latter, with three shallow cups 48 at 120 intervals to receive the balls previously mentioned. When the flywheel and the end plate are in their normal positions of rest on the shaft, the balls lie partially in the cups of the flywheel and partially in the cups of the end plate.

The inner periphery of the flywheel 44 has a central opening, and a projection 45 extends inwardly towards the centre of the opening. The shaft 14 has a groove 47 extending along its length, and this projection 45 runs along the groove 47 when the flywheel is assembled on to the shaft in a manner similar to the way that the end plate is assembled on to the shaft.

However, at the end of the groove 47 adjacent the end 30 of the shaft, the shaft has a circumferentially-extending recess 76. This permits limited rotational movement between the shaft and the flywheel.

On the outer face 50 of the wall 22 of the frame there is a fixed, non-rotatable, toothed ring 52 surrounding the shaft 14 and opposing the inner face 54 of the flywheel which has a ring of teeth 56 adapted to engage the teeth of the ring 52. When such engagement occurs, the flywheel is locked by the ring 52 against rotation. Normally, however, the teeth of the ring 52 and the teeth of the flywheel are out of engagement with each other due to the action of a helical compression spring 58 which surrounds the shaft 14 and urges the flywheel away from the toothed ring 52.

The operation of the reel described above is as follows: When the belt 10 is drawn off the reel without jerking, the shaft 14 turns and so does the end plate 32 and the flywheel 44. If, now, the belt is suddenly jerked or snatched, as happens for example when a road vehicle is suddenly braked or otherwise suddenly stopped in its forward motion, the speed of rotation of the flywheel will momentarily lag behind the speed of rotation of the shaft 14 and the end plate 32. This causes the balls in the cups of the flywheel and the end plate to ride up the sides of the cups in the flywheel and thus force the flywheel axially away from the end plate and into engagement with the toothed ring 52, the end plate 32 providing the reaction for the force which moves the flywheel axially.The flywheel is thereby locked against rotation, and this causes the shaft 1 4 to be locked too by means of the projection 45. The belt 10 is thus held fast by the reel, and remains so until the tension on the belt is released at which time the flywheel is above to resume its normal position.

Fig. 5 shows the form of the flywheel 44 in greater detail. This shows that the flywheel is toothed over its outer periphery 60 as well as on its inner face 54. This allows a springloaded stop 62 to stop rotation of the flywheel whenever an electrical signal is supplied to an electromechanical device 64. Such a signal is supplied by a transducer device and associated circuitry contained in a casing 77. When rotation of the flywheel is stopped, it is caused to move axially to a locked position by the ball and cup arrangement already described above with reference to Fig. 1. The purpose of the spring 66 which acts on the stop is simply to take up manufacturing tolerances and to prevent damage to the stop.

The transducer device is shown in Fig. 6. It comprises three components a, b and c arranged to detect deceleration respectively in three mutually perpendicular directions x, y and z. Each component is a seismic system comprising an inertial mass and a quartz crystal sandwiched between the inertial mass and a base of the component which is fixed securely to the structure of the reel. Electrodes are attached to the quartz crystal, one on the inertial mass side and one on the component base side. A potential difference is developed across the electrodes in the event of deceleration along the crystal axis by virtue of the Piezoelectric effect.

The signal given by a component of the transducer can be increased by having several flat crystals lying with their main faces adjacent to one another, the crystals being sandwiched between the mass and the base and one electrode being connected to the inertial mass sides of the crystals and the other to the component base sides.

Piezoelectric materials other than quartz may be used for these components. Alternatively, the transducer components may comprise bonded or unbonded strain gauge accelerometers, or Piezoresistive accelerometers.

The outputs of such accelerometers are obtained from a Wheatstone Bridge arrangement. The components may also be constructed so that a signal is obtained by means of a magnet and coil, or by the change in a capacitance device under the effect of acceleration.

As shown in Fig. 7, respective outputs of the components a, b and c are connected to three inputs of addition circuitry 71. This delivers an output signal the magnitude of which is Drooortional to the value

where x, y and z are the magnitudes of the output signals from the components a, b and c of the transducer device. The output signal is received by a discriminator 72 which only allows the signal through if it is beyond a certain threshold value. A large enough signal to do this will change the state of a bistable multivibrator 73 to cause supply of a continuous electrical current, from ampli fier 74, to output 75. This current operates the electro-mechanical device 64 to raise the stop 62.

The power source for the electro-mechanical device operating current may be a main battery of the vehicle. Auxiliary batteries (not shown) may be provided, to be switched in automatically in the event of failure in the supply from the main battery. Alternatively, an electromechanical relay (not shown) may be incorporated. Current from the main battery could then be used to keep the stop 62 down against the action of a biasing spring (not shown). The current would be interrupted by failure of the main battery or by an electrical signal at the output 45 operating on the electromechanical relay. Either a cash shock or failure of the main battery supply, or both, wuld cause the stop 62 to rise under the action of the biasing spring, to provide a fail safe system.

The addition circuitry 71, discriminator 72, multi-multivabrator 73 and amplifier 74 may all be part of the same silicon chip, possibly constituted by a micro-processor. The components a, b and C may be embedded in this chip, or manufactured as part of the chip if suitable materials are used.

Piezoelectric transducers tend to be most responsive to shock rather than continued acceleration. If these are used, therefore, it would probably not be necessary to take account of gravitional force affecting the device.

Strain gauges, on the other hand, will give a continued reading under the effect of gravity.

However, this can easiiy be compensated for by setting the threshold value of the discriminator 72 an appropriate amount above the value corresponding to acceleration or deceleration of 1 g.

The use of a transducer device with three components in this way, with the addition circuitry 71, ensures that the signal fed to discriminator 72 is proportional to the magnitude of the deceleration of the reel, but independent of the direction of deceleration. As a result, the device will operate equally effectively whichever way up the reel is installed in the vechicle.

Claims

1. A safety belt reel comprising a locking member which is movable between a free position, permitting the reel to operate for paying out a strap of the belt, and a locking position in which the reel is prevented from paying out the strap, and an electric or electronic transducer (as defined hereinbefore) capable of producing an electrical signal or a change in an electrical signal in response to deceleration it experiences, which signal is used to actuate, or to initiate actuation of, means for moving the locking member into its locking position when the deceleration is greater than a predetermined value.

2. A safety belt reel according to claim 1, in which the electric or electronic transducer produces an electrical signal or a change in an electrical signal by means of the Piezoelectric effect.

3. A safety belt reel according to claim 2, in which the electric or electronic transducer comprises a quartz crystal.

4. A safety belt reel according to claim 1, in which the electric or electronic transducer comprises a strain gauge accelerometer.

5. A safety belt reel according to claim 1, in which the electric or electronic transducer comprises a Peizoresistive accelerometer.

6. A safety belt reel according to claim 1, in which the electric or electronic transducer comprises a magnet and coil arrangement.

7. A safety belt reel according to claim 1, in which the electric or electronic transducer comprises a capacitance device constructed so that its capacitance changes under the effect of deceleration.

8. A safety belt reel according to any preceding claim, in which the electric or electronic transducer comprises three components arranged to detect deceleration in directions mutually perpendicular to one another respectively.

9. A safety belt reel according to claim 8, in which the electric or electronic transducer is connected to additional circuitry constructed to deliver an output signal the magnitude of which is proportional to the square root of the sums of the squares of the magnitudes of the output signals of the three components.

10. A safety belt reel according to any preceding claim, in which a discriminator device is connected to receive an input electrical signal produced by or in dependence upon the deceleration experienced by the electric or electronic transducer, the discriminator device being such as to provide an output electrical signal when the input electrical signal reaches or exceeds a given threshold value.

11. A safety belt reel according to any preceding claim, in which a bistable multivibrator is connected to provide an output signal in dependence upon an electrical signal produced by or in dependence upon the deceleration experienced by the electric or electronic transducer.

1 2. A safety belt reel according to any preceding claim, in which mechanical means are provided which urge the locking member in the locking position, and electromechanical means are also provided to hold the locking member in the free position against the action of the mechanical means so long as an electrical signal is applied to the electro-mechanical means unless and until that electrical signal ceases by failure or by virtue of the electric or electronic transducer experiencing a deceleration greater than the said predetermined value, to provide a fail safe system.

1 3. A safety belt reel according to any preceding claim, in which the effect of gravity is overcome by setting the said predetermined value above 1 g.

1 4. A safety belt reel according to any preceding claim, in which co-operating abutments form a positive stop between a rotary shaft of the reel and an end-plate which rotates with it to prevent the end plate from moving axially beyond an end of the shaft and also to prevent the end plate from rotating with respect to the shaft.

1 5. A safety belt reel according to claim 14, in which a further stop is provided at one end of the shaft to disperse any residual end load.

1 6. A safety belt reel according to claim 15, in which the said further stop is provided at that end of the shaft where the said endplate is disposed and comprises an out-turned flange integral with the shaft.

1 7. A safety belt reel according to any one of claims 14 to 16, in which the endplate is provided with ball-cups on a face which opposes a corresponding face of a flywheel which also has ball-cups so that balls in the cups normally lie partially in the cups of the flywheel and partially in the cups of the end-plate.

1 8. A safety belt reel according to claim 17, in which the shaft of the reel is supported on a frame which carries a fixed non-rotatable toothed ring adapted to engage a corresponding toothed ring on the flywheel so as to stop rotation of the latter.

19. A safety belt reel according to claim 18, in which the two toothed rings are normally held out of engagement with each other by a spring.

20. A safety belt reel according to any preceding claim, in which a shaft of the reel is supported on a frame comprising a pair of opposing walls which are held "square" to each other by two or more pins having notches which are received, as a tight fit, in respective grooves in outer edge portions of the said opposing walls.

21. A safety belt reel according to any preceding claim, in which the electrical signal or change in electrical signal produced by the electric or electronic transducer is used to actuate a spring-loaded flywheel stop, the spring serving to take up manufacturing tolerances and to prevent damage to the stop.

22. A safety belt reel substantially as described herein with reference to the accompanying drawings.