GB2129077A

GB2129077A - Anti-roll back device

Info

Publication number: GB2129077A
Application number: GB08327041A
Authority: GB
Inventors: Keith Hobson; Brian Hartley
Original assignee: FAIREY WINCHES Ltd
Current assignee: FAIREY WINCHES Ltd
Priority date: 1982-10-08
Filing date: 1983-10-10
Publication date: 1984-05-10
Also published as: GB8327041D0; GB2129077B

Abstract

The device has engagement means for association with a rotary drive shaft (5) of a drive unit, said means being such as to allow free rotation of the drive shaft in one direction, and being such as to prevent its rotation when the drive shaft attempts to rotate in the opposite direction, and there being further means selectively activatable to hold said engagement means in an inoperative position during any period where the shaft is required to be rotated in the reverse direction. For use in a vehicle, the engagement means prevent the vehicle rolling back: the means selectively actuatable respond to gear lever being in reverse gear position and may comprise electric means using a motor 16 or solenoid, or mechanical means. Various forms of engagement means are disclosed e.g. brake belt 10 engaging a brake drum 7 fitted to a vehicle said drive shaft; pawl and ratchet mechanisms, brake shoes engageable with a drum. <IMAGE>

Description

SPECIFICATION Vehicle anti-roll back device This invention relates to an anti-roll back device, for location between drive and driven means, and is particularly, but not necessarily exclusively concerned with an anti-roll back device for motor vehicles.

In the ordinary way when a vehicle is being driven uphill and is brought to a halt, the handbrake is applied to hold the vehicle stationary.

With many vehicles the handbrake is not nearly so efficient as the footbrake and consequently to guarantee preventing the vehicle from rolling backwards, the vehicle may need to be left in gear.

When the bringing of a vehicle to a halt is a temporary manoeuvre such as at a junction, at traffic lights, or because of traffic congestion, there is a temptation for the driver to use the clutch and not apply the handbrake. Because the vehicle is held stationary by having the engine driving in a forward gear and by holding the clutch partly open so that there is slip at the clutch plates, this inevitably causes unnecessary wear on the clutch plates. Particularly when a vehicle is being brought to a temporary halt, the possibility of the vehicle rolling backwards is greatly increased with inexperienced drivers, particularly those who are at the learning stage, and it is quite well known that vehicles rolling backwards down a hill is a source of many traffic accidents.

The object of the present invention is to provide means for application to a vehicle which will prevent the accidental rolling back of a vehicle when brought to a permanent or a temporary halt facing up a hill.

According to the present invention, an anti-roll back device comprises engagement means associated with a rotary drive shaft of a drive unit, said means being such as to allow free rotation of the drive shaft when rotating in a direction to drive the driven unit in the required direction, and being such as to engage the drive shaft and prevent its rotation when the drive shaft attempts to rotate in the opposite direction, and there being further means selectively activatable to hold said engagement means in an inoperative position during any period where the driven unit is required to be rotated in the reverse direction.

It will be understood that by "drive shaft" is meant any rotatable shaft lying between the drive and driven units, for example, the drive shafts of a front wheel drive vehicle or the propelling shaft of a rear wheel drive vehicle.

Thus, the engagement means associated with the drive shaft may be a loop or noose of a flexible material formed from friction material, or may be, e.g., of nylon material faced with a friction material, the loop passing around the drive shaft and when the arrangement is such that when the drive shaft is rotating in a direction e.g., to drive a vehicle forwardly, the effect on the loop or noose is to cause it to slacken and hence allow the shaft to freely rotate in that direction, and the instant the drive shaft attempts to rotate in the opposite direction the loop or noose is caused to tighten on the shaft and hence prevent that opposite rotation.

Whilst the loop or noose may contact the drive shaft itself, it is preferred to secure to the drive shaft a brake drum, said brake drum being coaxial with the shaft, and for the loop or noose to engage around the brake drum.

As an alternative, the means associated with the drive shaft may be brakeshoes which again preferably engage a brake drum associated with the drive shaft. Here the arrangement is such that the brakeshoes engage the brake drum to hold it against rotation, there being a ratchet mechanism on the brake drum to be engaged by pawl mechanism associated with the drive shaft, which pawl mechanism engages the ratchet mechanism when the drive shaft comes to rest, the interengagement between the pawl mechanism and the ratchet mechanism, and the brakeshoes holding the brake drum stationary, preventing reverse rotation of the drive shaft.

As a still further alternative, pawl and ratchet mechanism can be provided where the ratchet mechanism is secured to and rotates with the shaft to be engaged by the pawl mechanism when the shaft comes to rest and again when reverse rotation of the shaft is prevented.

The means that can be selectively activated to disconnect the engagement means and hence allow positive driving of e.g., a vehicle in the reverse direction may be electrically operable.

Thus it is common to all vehicles that a switch is provided associated with the gear lever, which switch is activated as the gear lever is brought into its reverse position. Said switch can therefore be utilised to activate motor drive means, solenoid means or the like associated with the engagement means to bring about disengagement for so long as the gear lever is in its reverse position.

Thus, with the form of construction where the engagement means is constituted by a loop or noose engaging, e.g., around a brake drum, the motor drive means, solenoid means, or the like connected to said reverse gear switch can be attached to the free end of the loop or noose and when operation of the motor drive means, solenoid means of the like positions the free end of the loop or noose in either a first position where tightening of the loop or noose around the shaft will take place to a position where such tightening is prevented.Alternatively the free end of the loop or noose can be attached within the casing, and the motor drive means, solenoid means of the like adapted to bear against the loop or noose to induce sufficient tension to permit tightening and move to a position where such tensioning is relaxed and when the loop or noose is prevented from such tightening around, e.g., a brake drum on the drive shaft. When the engagement means is a combination of pawl means secured to the drive shaft and ratchet means on a brake drum held stationary by brakeshoes, said motor drive means, solenoid means or the like can be caused to activate cam-like mechanism to release the brakeshoes from the brake drum to allow it to rotate and hence allow positive reverse rotation of the drive shaft.

When the engagement means is ratchet means secured for rotation with the drive shaft to be engaged by pawl means when the drive shaft becomes stationary, said motor drive means, solenoid means or the like activate cam-like means to hold the paw means clear of the ratchet means and allow positive reverse rotation of the drive shaft.

In addition to utilising the reverse gear switch to activate electric means to disconnect the engagement means, it is possible for disengagement to be effected mechanically. Thus, the types of release mechanism mentioned hitherto can have the motor drive means, solenoid means or the like replaced by, e.g., boden cable or the like activated means extending to a suitable operating handle within the vehicle. To provide mechanically for the automatic operation of the disengaging means, in the form of construction where a loop or noose extends around, e.g., a brake drum, one end of the loop or noose may be secured within the casing and the other end of the loop or noose slidably mounted on connecting means located within the casing and with the end of the loop or noose provided with an abutment member.Also mounted on the connecting means is a pivotally mounted weighted arm having a stepped formation at its end adjacent the abutment member. Thus with a vehicle ascending a hill a relative angular disposition is created between the pivoted weighted arm and the abutment means on the belt and when the stepped end of the arm provides a greater clearance between the arm and the abutment means. That clearance is sufficient to allow tightening of the belt on to, e.g., a brake drum when the vehicle attempts to roll back.

Irrespective as to the relative angular disposition the clearance between the abutment means and the end of the pivoted arm of closest approach is such that the anti-roll back device will function.

However on positively loading the loop or noose by engaging the vehicle in reverse gear and deliberately driving the vehicle in reverse, the belt attempts to tighten further on the brake drum and inevitably stretches to a point where the abutment means contacts the end of the arm of closest approach and hence prevents further tightening of the loop or noose on the brake drum. Whilst a degree of friction is generated by rotating the brake drum in this condition, the vehicle is permitted to move in reverse as and when required.

These and other aspects of the invention will become clearer in the following description of several embodiments of the invention described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic view of an anti-roll back device for a rear wheel drive vehicle; Figure 2 is an exploded perspective view of an anti-roll back device in accordance with one embodiment of the invention; Figure 3 shows to a larger scale the loop or noose mechanism of Figure 2; Figure 4 is an exploded perspective view of an anti-roll back device in accordance with a second embodiment of the invention; Figure 5 is an elevation of part of an anti-roll back device according to a third embodiment of the invention; Figure 6 is a side elevation of Figure 5; Figure 7 is an exploded perspective view of a fourth embodiment of the invention; and Figure 8 is a side elevation of part of a fifth embodiment of the invention In Figures 1, 2 and 3 an anti-roll back device for a motor vehicle is formed as a unit 1 attached to the differential of the vehicle by two U bolts 2 and 3. The unit is a push fit over the differential casing 4 at the pinion to the drive shaft 5 connection.

As is shown particularly by Figure 2 within the unit casing 6 is a brake drum 7 fitted on the vehicle drive shaft (not shown) and attached to the vehicle drive plate 8 by four screws 9. Also within the unit is a noose brake belt 10 secured at one end between the arms of a slide bar 11, the belt extending around the brake drum from a pin 12 at one end, over a pin 13 centrally of the arm and around a pin 14 at the other end of the arm. The central pin has a roller 1 5 mounted on it to assist in the movement of the belt, and the slide bar is secured in the casing by the pin 12.

Externally of the unit, an electric motor 1 6 is provided, secured to the unit casing by screws and electrically connected to a reverse switch on the vehicle gear lever via an appropriate relay. The spindle 1 7 of the motor extends into the casing and has a cranked end section 1 8 to which the free end of the belt is secured.

Also mounted on the casing is a motor drive plate 1 9 where the electrical connections to the motor are made, overlaid by a plate 20 carrying two micro-switches to be contacted by a cam 21 mounted on the motor drive spindle.

The casing is closed by a cover plate 22 secured to the casing by screws 23.

Thus, when the vehicle is moving in a forward direction, the direction of rotation of the drive shaft and hence the brake drum is such as to cause the noose to slacken around the brake drum and thereby allow the brake drum to run freely within the noose. With the vehicle ascending a hill and with the vehicle brought to a halt any tendency for the vehicle to roll backwards causes an attempted reverse rotation of the drive shaft and hence the brake drum and when the noose belt tightens on the brake drum to prevent its rotation in this, opposite, reverse direction. Thus, with the vehicle in any forward gear and with the clutch depressed, or with the vehicle in neutral, there is no need to apply the hand brake, as the anti-roll back device effectively serves as a brake to prevent the accidentai rolling back of the vehicle.

When the vehicle is required to move in a reverse direction, the gear lever first has to be put into its reverse position. The conventional reverse switch is then activated to drive the motor through the relay. The motor then rotates to drive its spindle by half a revolution and until the first micro limit switch activated by the cam cuts the electrical supply to the motor. Thus with a cranked end section of the motor spindle turned towards the brake drum,the noose is prevented from tightening on the brake drum when the brake drum is driven in the opposite, reverse, direction.

At the end of the reversing operation the gear lever is taken out of reverse gear condition, the reverse switch associated with it is deactivated and when the relay activates the second microswitch to cause the motor to return to its original position and when the noose is brought to its position which allows it to tighten on the brake drum when required.

As a safety measure, a ratchet wheel 24 is fitted to the motor spindle 17, to be engaged by a pawl 25 mounted on the slide bar lock pin 14.

Thus, if the vehicle is rapidly replaced in reverse gear after being taken out of reverse gear and before the motor has had time to function to return the loop to the operative position, engagement of the paw with the ratchet wheel prevents unacceptable loading of the motor spindle. In Figure 4, an anti-roll back device is again formed as a unit 1 attached to the differential of the vehicle by U bolts 2, 3, with the unit a push-fit over the differential casing at the pinion to the drive shaft connection. Again, within the casing is a brake drum 26 fitted on the drive shaft (not shown) and secured to the vehicle drive plate 8 by screws 9. Externally of the casing is a motor 16 the drive spindle 1 7 of which extends into the casing and has a cranked end section 1 8.

Also mounted on the casing is a motor drive plate 1 9 to which electrical connection to the motor is made, overlaid by a micro-switch plate 20 carrying two micro-switches to be contacted by a cam 21 mounted on the motor spindle. There is again a cover plate 22 to close the casing and there secured by screws.

In this embodiment, the brake drum 26 is flanged to each side, one flange 27 being formed with ratchet teeth, and a ratchet pawl 28 is provided mounted on the cranked end of the motor spindle, the spindle engaging in a recess 29 formed between the pawl body and a removable end piece 30. At the opposite side of the pawl is a roller 31 which rides on gear teeth 32 formed on the flange on the brake drum to that side.

Thus, with the vehicle in a forward gear, the motor spindle is in a position where the pawl 28 can engage the ratchet teeth 27, the roller 31 riding on the gear teeth 32 lessening any chatter or noise by lifting the pawl clear of the ratchet teeth as the brake drum 26 rotates in a forward direction. In this condition the vehicle drive plate and drive shaft can freely rotate. As the drive plate and hence brake drum are brought to rest, the pawl engages the ratchet, and when any attempt by the brake drum to rotate in the opposite direction is prevented. Thus, if the vehicle is ascending a hill, any tendency to roll back is prevented.

To permit the vehicle to be positively moved in the reverse direction, the motor gear lever is placed in its reverse position thus activating the reverse gear switch to which the motor is connected. This causes rotation of the spindle to draw the pawl 28 clear of the ratchet, until the cam 21 contacts the first micro-switch to cut-out the motor. With the pawl held clear of the ratchet, the brake drum can freely rotate, and hence the vehicle reversed. On taking the gear lever out of reverse position, the reverse switch is deactivated, causing the second micro-switch to be activated via a relay, to drive the motor in the opposite direction to return the pawl to its operative position.

In Figures 5 and 6 a still further alternative is shown. In its essential respects, the anti-roll back device is substantially similar to that shown in Figure 4, but here, a single ratchet wheel 33 is provided on the brake drum to be contacted by a pawl 34. Mounted on the brake drum are two arcuate arms 35 held to the brake drum by springs 36 and the pawl is pivotally mounted in the casing and attached to the cranked end 18 of the motor spindle 1 7.

During forward movement of the vehicle, rotation of the brake drum causes the arcuate arms to move outwardly under the action of centrifugal force, the arms contacting the pawl to hold it clear of the ratchet. When the brake drum comes to rest, the pawl is allowed to engage the ratchet, and hence prevent reverse rotation of the drum, and hence the vehicle drive plate and shaft, thereby preventing the vehicle from rolling back To allow positive reversing of the vehicle, the motor is activated after the manner described in Figure 3 to pivot the pawl and hence hold it clear of the ratchet, and return the pawl to the ratchet at the end of the reverse manoeuvre.

In Figure 7, a still further alternative is disclosed. Here, a unit base plate 35 is secured to a vehicle differential, to which is secured a casing 36 closed by a cover plate 37. Within the casing a drive plate 37 is provided secured to the pinion bearing drive shaft plate of the differential unit there being pivotally mounted on the drive plate 37 four pawl members 38. Mounted on the drive plate is a shaft 39 which extends through the bore of a brake drum 40 within the casing, which shaft extends to and is connected to a drive plate 41 for connection to the propelling shaft of the vehicle.

The brake drum is provided with a ratchet ring 42 to cooperate with the pawls 38.

Mounted in the casing and surrounding the brake drum is a brake shoe unit 39, spring loaded by springs 40 into contact with the brake drum, and there being a cam member 43 disposed to open the brake shoe unit to free the brake drum as and when required. The cam member has a splined shaft 44 engaging in a splined hole 45 of an arm 46 of a solenoid unit 47.

Thus, during normal forward driving of the vehicle, the brake shoe unit is held in contact with the brake drum, to hold it against rotation, and rotation of the drive plate imposes a centrifugal force on the pawls to hold them clear of the ratchet. As the drive plate comes to rest, at least two pawls will be in a position where they fall by gravity into contact with the ratchet ring and as a consequence reverse rotation of the drive plate, and hence rolling back of the vehicle is prevented.

To allow the vehicle to be reversed, the vehicle gear lever is placed in position hence activating the reverse gear switch to activate the solenoid 47 in connection via a suitable relay. On activation of the solenoid, the arm 46 is rotated to rotate the cam 43, and release the brake shoe unit from the brake drum. In this condition, the brake drum can rotate with the drive plate 37 to allow the reverse manoeuvre to take place. At the end of that manoeuvre, the gear stick is taken out of the reverse position, its switch de-activated and hence the solenoid, and when the springs close the brake shoe unit on to the brake drum.

In Figure 8, a still further form of construction is shown. Here a loop or noose 48 is provided which, also not shown, again extends around a brake drum associated with the drive shaft. One end of the loop or noose is secured within the unit case, and the other end of the loop or noose is provided with an abutment means 49 and is siidably mounted on a connecting member 50 located within the casing. Located within the connecting member is a pivoted weighted arm 51 the end 52 of which adjacent the abutment means is stepped.

When the vehicle is on level ground or descending a hill, the arm is so disposed in relation to the abutment means that the end face 53 is of closest approach, and is spaced from the abutment means by an amount insufficient to allow movement of the belt by tightening on the drum. However when the vehicle is ascending a hill, the pivoted arm assumes an angular disposition in relation to the abutment means such that one or other of the stepped faces is brought to a position in line with the abutment means thereby providing greater clearance between the abutment means and the arm, and a clearance sufficiently great such that should the vehicle attempt to roll back the loop or noose can tighten on to the brake drum. If, in this condition, positive reverse manoeuvering must take place, the vehicle can be engaged in third gear and the drive shaft and hence the brake drum deliberately driven in that direction. This attempts to tighten still further the loop or noose on the brake drum with inevitable stretching of the loop or noose until such time as the abutment means contacts the one or other of the stepped faces thereby preventing further tightening and when the vehicle can be driven in the reverse direction albeit with the generation of a degree of friction between the loop or noose and the brake drum.

Claims

1. An anti-roil back device comprising engagement means associated with a rotary drive shaft of a drive unit, said means being such as to allow free rotation of the drive shaft when rotating in a direction to drive the driven unit in the required direction, and being such as to engage the drive shaft and prevent its rotation when the drive shaft attempts to rotate in the opposite direction, and there being further means selectively activatable to hold said engagement means in an inoperative position during any period where the driven unit is required to be rotated in the reverse direction.

2. An anti-roll back device as in Claim 1, wherein the engagement means is a loop or noose of a flexible material formed from or faced with a friction material, the loop passing around the drive shaft and when the arrangement is such that when the drive shaft is rotating in a direction e.g., to drive a vehicle forwardly, the effect on the loop or noose is to cause it to slacken and hence allow the shaft to freely rotate in that direction, and the instant the drive shaft attempts to rotate in the opposite direction the loop or noose is caused to tighten on the shaft and hence prevent that opposite rotation.

3. An anti-roll back device as in Claim 2, wherein a brake drum is secured to the drive shaft, said brake drum being coaxial with the shaft, and said loop or noose engages around the brake drum.

4. An anti-roll back device as in Claim 1, wherein the means associated with the drive shaft are brakeshoes, the brakeshoes engaging a brake drum associated with the drive shaft to hold it against rotation, there being a ratchet mechanism on the brake drum to be engaged by pawl mechanism associated with the drive shaft, which pawl mechanism engages the ratchet mechanism when the drive shaft comes to rest, the interengagement between the pawl mechanism and the ratchet mechanism, and the brakeshoes holding the brake drum stationary, preventing reverse rotation of the drive shaft.

5. An anti-roll back device as in Claim 1 wherein pawl and ratchet mechanism is provided, the ratchet mechanism being secured to and rotating with the drive to be engaged by pawl mechanism when the shaft comes to rest and when reverse rotation of the shaft is prevented.

6. An anti-roll back device as in any of Claims 1 to 5, wherein the means to be selectively activated to disconnect the engagement means is electrically operabie.

7. An anti-roil back device as in Claim 6, when appended to Claim 2, wherein motor drive means, solenoid means or the like engage with the loop or noose to put the loop or noose in a first condition where tightening on the drive shaft is permitted or a second condition where tightening of the loop or noose is prevented.

8. An anti-roll back device as in Claim 6, when appended to Claim 4, wherein motor drive means, solenoid means or the like activate cam-like means to release said brakeshoes from said brake drum to allow it to rotate and hence allow positive reverse rotation of the drive shaft.

9. An anti-roll back device as in Claim 6, when appended to Claim 5, wherein motor drive means, solenoid means or the like activate cam-like means to hold the pawl means clear of the ratchet means and allow positive rotation of the drive shaft.

10. An anti-roll back device as in any of Claims 6 to 9, and when the drive shaft is a drive shaft of a motor vehicle, said motor drive means, solenoid means or the like are electrically connected to the switch associated with the gear lever when in reverse gear position whereby to activate said motor drive means, solenoid means or the like to disengage the engagement means when the vehicle is placed in reverse gear.

11. An anti-roll back device as in any of Claims 1 to 5, wherein said engagement means are selectively disengaged by mechanical means.

12. An anti-roll back device as in Claim 11, wherein said selectively activatable means are driven by a boden cable from a suitable hand lever.

13. An anti-roll back device as in Claim 11, and with the form of construction where a loop or noose extends around the shaft or a brake drum associated with the shaft, wherein one end of the loop or noose is provided with abutment means and there is provided in proximity to said abutment means a pivoted weighted arm having a stepped configuration at its end of closest approach to the abutment means, said pivoted arm assuming a relative angular position dictated by the angular disposition of the drive shaft to provide clearance between the abutment means the stepped end of the shaft such that a sufficient clearance is provided to render the engagement means operative in preventing reverse rotation of the shaft and said clearance being such that deliberate loading of the drive shaft by positive rotation in the reverse direction casing stretching of the loop or noose until the abutment means contacts the stepped end face of the arm to prevent further tightening of the loop or noose and when positive reverse rotation can be effected.

14. An anti-roll back device substantially as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.

1 5. An anti-roll back device substantially as hereinbefore described with reference to Figures 1 and 4 of the accompanying drawings.

1 6. An anti-roll back device substantially as hereinbefore described with reference to Figures 5 and 6 of the accompanying drawings.

1 7. An anti-roll back device substantially as hereinbefore described with references to Figures 1 and 7 of the accompanying drawings.

1 8. An anti-roll back device substantially as hereinbefore described with reference to Figure 8.