GB1602139A - Vehicle stopping apparatus - Google Patents

Description

(54) VEHICLE STOPPING APPARATUS (71) We, WESTINGHOUSE ELEC TRIC CORPORATION of Westinghouse Building, Gateway Center, Pittsburgh, Pennsylvania, United States of America, a corporation organised and existing under the laws of the State of Pennsylvania, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- The present invention generally relates to the stopping operation of a vehicle along a road track ending at one or more desired stopping locations; more particularly, it concerns a stopping apparatus to provide overrun protection at the end of a track to bring a moving vehicle to a stop with controlled deceleration and preventing undesirable vehicle overspeeds having regard to passenger comfort.

A transportation system employing selfpropelled rubber-tired vehicles moving along a roadway, including a guide beam mounted in the center of the roadway, is disclosed in U.S.

Patent 3,312,180 of E. O. Mueller, with the vehicles being steered by laterally spaced guide wheels depending from the undercarriage of the vehicle and rotating in a horizontal plane to engage opposite vertical faces of the guide beam. A similar transportation system is described in an article published in the "Westinghouse Engineer" for January 1969 at pages 9 to 15 by E. E. Hogwood et al.

It is known in the prior art to provide a vehicle-stopping apparatus moving in the form of a braking skate, including a shoe adapted to slide along a track rail while exerting pressure on the rail to provide friction for ab sorbing the energy of momentum of the vehicle as shown by U.S. Patent 306,574 of M. F.

Bonzano. It is also known to provide a wedge shaped member operative with a guideway slid ing along the track rail and moved by the train vehicle to produce considerable friction between the guideway and the rail for absorbing the kinetic energy of the rolling vehicle as shown by U.S. Patent 1,204,189 and 2,807,220.

It is known in the prior art to provide a predetermined speed distance profile for a vehicle travelling between first and second stations and to sense any overspeed condition of the vehicle to provide a controlled stop prior to reaching any physical barrier along the vehicle travel path as shown by U.S. Patent 3,727,046 of D. H. Woods et al.

However, prior art apparatus do not take an accurate account of parameters such as the desired stopping distance, the highest vehicle weight or travel speed in deciding the taper and length of the wedge members used on the track for stopping. The present invention provides for considering such parameters in desgning an apparatus to stop a train vehicle.

The invention in its broad form comprises a vehicle-stopping apparatus to stop in a jerkfree manner a moving vehicle which is steered by a longitudinal guide member fixedly disposed to steer and guide the vehicle in its direction of motion, the moving vehicle being stopped after it hits the stopping apparatus which is stationary, said apparatus comprising at least one ramp means disposed in fixed relation to said guide member, a cart means disposed to move along said guide member and including means to resist any tendency of the cart means to disengage from said guide member, a frictional pad means supported by the cart means and disposed to engage said ramp means in such a manner that movement of said pad means in the direction of the guide member and in engagement with the ramp means progressively increases a frictional force between the pad means and the ramp means, and ajustable means to select and maintain an initial pressure-loading of the frictional pad means on the ramp means so that depending on the ramp profile, a desired characteristic of vehicle velocity versus stopping distance can be achieved by suitably setting said adjustable means.

A more detailed understanding of the invention can be had from the following description of an exemplary embodiment to be read in conjunction with the accompanying drawing in which: Figure 1 is a cross-sectional view of a prior art and well-known rubber-tired vehicle operative with a roadway including a central guide beam; Figure 2 is a perspective view of the vehiclestopping apparatus and a portion of the wedge member corresponding to a first described embodiment; Figure 3 is a curve showing the vehiclestopping characteristic provided by the present vehicle stopping apparatus; Figure 4 provides curves illustrating practical limits for the deceleration and jerk-limited stopping operation desired for a passenger vehicle; Figure 5 shows a top view of a modification of the first embodiment of the vehicle-stopping apparatus;; Figure 6 shows a side view of the modified apparatus shown in Figure 5; Figure 7 illustrates the relationship between the frictional retarding force and the break pad force against the guide beam; Figure 8 is a curve showing the vehiclestopping characteristic provided by the prior art stopping apparatus; Figure 9 shows second modification of the described embodiment; Figure 10 is a curve showing the vehiclestopping characteristic provided by the apparatus shown in Figure 9; Figure 11 shows a modification of the stopping apparatus shown in Figure 2 and with the lower front wheel extending forward to further prevent a tendency of the stopping apparatus to rotate because of a force couple; Figure 12 shows an end view of the vehicle stopping apparatus of Figure 2; and Figure 13 illustrates how the support plate of Figure 12 is retained in position.

In Figure 1 there is shown a cross-sectional view of a rubber-tired transit vehicle such as disclosed in U.S. Patent 3,312,180 of E. O.

Mueller. The roadway includes tracks 10 and 12 and a central guide beam 14. The vehicle 16 rides on rubber-tired wheels 18 and 20 and includes guide wheels 22 and 24 depending from the undercarriage of the vehicle 16 and rotating in a plane perpendicular to the web of the guide beam 14 and engaging the opposite sides of the guide beam web for retaining the vehide 16 on the roadway tracks 10 and 12.

Each end of the vehicle includes a bumper member positioned a known height, e.g. two feet, above the roadway tracks.

In Figure 2 there is shown an exemplary embodiment of the present invention, including a cart having a frame member 30 having upper support wheels, 32 and 33, operative below the top flange 36, and lower support wheels 34 and 35 operative above the bottom flange 38 of the guide beam 14. Similar support wheels not shown are provided and operative with the top flange 36 and the bottom flange 38 on the other side of the guide beam 14.

The support wheels resist any tendency of the cart getting disengaged from the guide beam 14; such a feature is particularly helpful when the moving vehicle impinges on the vehiclestopping apparatus, which would have a tendency to be knocked out of engagement from the guide beam because of a force couple.

The vehicle-stopping apparatus is operative with the roadway at a location adjacent to and about two feet beyond the normal and desired vehicle-stopping position, such as a passenger station, and provides an emergency stopping of the vehicle when connected by the vehicle to prevent the vehicle from running off the roadway or running into an obstruction like a wall or building. The stopping apparatus includes a frictional pad means or one or more serially provided brake shoes 37, 39 and 41 loaded by springs 42, 43 and 45 to press the brake shoes against the top of a wedge member 44 fixed above and to the top flange 36. The wheels 32, 33, 34 and 35 provide guidance of the stopping apparatus along the guide beam 14 after a moving vehicle contacts the bumper 46.

The wheels 32 and 35 prevent an initial rotation of the stopping apparatus to obviate an undesired step increase of frictional force which would otherwise be generated by the vehicle input force tending to rotate the stopping apparatus relative to the guide beam 14.

In Figure 3 the curve 47 shows the desired gradual increase in the frictional force retarding the vehicle as a function of stopping distance provided by the frictional force between the brake shoes 37, 39 and 41 and the top of the wedge member 44. The maximum provided deceleration friction force and the rate of change or jerk limit of that force is controlled by selection of the wedge ramp angle in relation to the length of the wedge member 44 and the spring force applying the brake shoes against the top of the wedge member in conjunction with the wheel 33 below the guide beam top flange 36.If the moving vehicle is stopped in 22 feet, such as shown by the curve of Figure 3, the area under the curve represents the kinetic energy of about 601,242 foot pounds that is absorbed in braking to a stop a typical vehicle weighing 20,000 pounds normally loaded with passengers and travelling at 30 mph. The retarding friction force should not exceed 100,000 pounds for this example if it is desired to limit the maximum deceleration rate to 5 g's, and the buildup of force should not exceed 200,000 pounds per second if the jerk is to be limited to 10 g's. The initial impact of the vehicle connecting with the sledstopping apparatus is cushioned by the rubber bumper 46 which could include a mechanical or hydraulic spring to limit the initial acceleration of the sled mass of about 500 pounds in a jerk-limiting manner.

The vehicle-stopping apparatus shown in Figure 2 is illustrated to include three sets of spring-loaded brake shoes 37, 39 and 41 located in series along the longitudinal axis of the guide beam 14. The respective springloaded brake shoes 37, 39 and 41 are initially positioned on the wedge-tapered ramp 44 at the beginning of the wedge 44, so the frictional force will increase linearly as shown by Figure 3 assuming a substantially constant spring rate and starting at approximately zero frictional force. The frictional force buildup would otherwise occur in three steps as each set of brake shoes 37, 39 and 41 successively engages the ramp 44. So all three of the brake-shoe assemblies are initially positioned to engage the ramp and the rate of frictional force increase will remain substantially constant.

The curves of Figure 4, assuming that the rubber bumper will provide the desired jerk limit of the initial acceleration of the braking apparatus, show illustrative operational conditions to satisfy the above deceleration and jerk limits of stopping the vehicle.

In Figure 5 there is shown a top view of a modified stopping apparatus, having a first wedge ramp 70 fixed to one side of the vertical web 72 of the guide beam 74 and a second wedge ramp 76 fixed to the opposite side of the web 72. The vehicle-stopping apparatus 78 includes a cart having a frame 80 supporting a plurality of spring-loaded and serially positioned brake shoes 82 disposed in apposition with the ramp 70 and a like plurality of brake shoes 84 operative with the ramp 76. The bumper 86 is contacted by the moving vehicle prior to stopping.

In Figure 6 there is provided a side view of the apparatus shown in Figure 5 with the brake shoes 84 being initially operative against the web 72 of the guide beam 74 and subsequently riding on the ramp 76, when a moving vehicle contacts the bumper 86 to push the stopping apparatus in the direction of travel of the vehicle.

In Figure 7 is illustrated the relationship between the vehicle-retarding frictional force F and the normal force N down on the brake shoes. The general relationship is F = UN, where U is the known coefficient of friction.

The ramp 44 keeps compressing the brake shoe springs as the stopping apparatus is moved along the ramp by the moving vehicle, so the frictional force F correspondingly increases. If desired, the ramp can be designed to reach a predetermined maximum thickness and thereafter have the maximum thickness constant over a length so that the frictional force reaches a known maximum value and thereafter remains substantially constant. In this way, the characteristic curve shown in Figure 3 can be modified as desired.

After a moving vehicle has required an emergency stop by operation of the stopping apparatus of the present invention, the lock nuts 15, 17 and 19 shown in Figure 2 operative with threaded posts 21, 23 and 25 for holding the brake shoe springs can be released or an overcenter cam device can be provided to release the brake shoes, and to enable the frame 30 and the brake shoes 37, 39 and 41 to be backed off the ramp and into the ready position such as shown in Figure 2.

It is contemplated that a maximum ramp rise of between 1 inch and 2 inches should be adequate. If desired, the brake shoe springs can be nonlinear and the profile shape of the ramp can be selected to provide a particular desired vehicle-braking characteristic.

Figure 8 shows the vehicle-stopping characteristic provided by the prior art apparatus, resulting from a wedge member having relative movement with a vehicle, but without considering the desired jerk limit or a desired variable force versus stopping distance characteristic of the vehicle.

Figure 9 shows a wedge member 44 shaped to achieve an increasing thickness which stays constant a short distance along the travel path of the vehicle to be stopped; the consequent maximum frictional retarding force is provided as shown by the curve of Figure 10. One or more of such constant thickness portions of the wedge member 44 can be provided as desired to have the vehicle-stopping characteristic curve shown in Figure 10.

In Figure 11 there is shown a modification of the stopping apparatus shown in Figure 2, with the frame member 30 being extended forward to hold the lower support wheel 35 ahead of the upper support wheel 33, when the stopping apparatus moves to the left along the ramp or wedge 44 when stopping the passenger vehicle.

In Figure 12 there is shown an end view of the apparatus of Figure 2, with the frame member 30 extending down both sides of the guide beam to hold the support wheel 33 at an angle corresponding to the underside of top flange 36, the other support wheel 32 being similarly supported. The wedge 44 is suitably fastened to the top of flange 36, such as by welding or by countersunk bolts and can be made of stainless steel or like material. The material of brake member 41 can be any wellknown type having a coefficient of friction in the order of 0.5 with the wedge. A support plate 92 is positioned within the channel sides 94 and 96 of the frame member 30 to prevent movement with the top surface of the wedge 44 when a vehicle is being stopped.A plurality of compression springs 45, 98 and 100 are provided between the support plate 92 and the compression force adjusting threaded posts 25, 102 and 104. The latter threaded posts are each operative with respective threaded inserts 106, 108 and 110 to determine the desired initial preloading compression of the springs 45, 98 and 100, if it is desired to increase the initial frictional retarding force provided by the stopping apparatus.

In Figure 13, the support plate 92 and the brake member 41 are shown retained in lateral position by the channel sides 94 and 96.

In relation to Figure 2, the support wheel 35 prevents the stopping apparatus from nosediving upon the initial impact of the moving vehicle into the pad 46 and the support wheel 33 holds the brake pads in position and forcing down against the top surface of the wedge 44 as the apparatus moves to the right during a vehicle-stopping operation. These wheels could be well known and readily available ball-bearing devices having inner and outer race members, with an axle extending through the inner race. These wheels can be removed from the frame member 30 when the stopping apparatus is initially positioned relative to the guidebeam 14 and wedge 44, and thereafter the wheels are replaced to hold the stopping apparatus in the desired operating position.

If the bumper pad 46 is about two feet high and the stopping apparatus has a length of about four feet, it is reasonable to expect brakeshoe pressures against the wedge 44 in the order of 120,000 pounds or so for a typical vehicle weight of 20,000 lbs. and operational relationships such as shown in Figure 4; each brake shoe may have dimensions of about six inches by 10 inches, with the six-inch dimension being parallel to the longitudinal axis of the guide beam 14.

It is desired to provide a gradually increasing braking force as shown in Figure 4, so the wheel 35 is provided to prevent a tendency of the stopping apparatus to nose dive while accelerating after initial impact by the vehicle and to prevent a corresponding undesired increase in brake pressure against the wedge 44; this would cause undesired initial bumps in each of the force curves, the jerk curves and the deceleration curves shown in Figure 4.

When it is desired to restore the stopping apparatus to its original position after a vehicle has been stopped, the brake pads can be released by loosening the compression springs for each of the brake pads in relation to the wedge.

The support plate 92 can be in the order of 1/2 inch thick, and the brake pad 41 can be about 1/4 inch thick. The number of compression springs operative with each support plate 92 can be two or three, depending on the desired brake pad force against the wedge and the physical size of the available springs for this purpose. Also, three or four brake pads can be employed, depending upon the kinetic energy of the moving vehicle to be absorbed in braking to a stop a normal vehicle. The brake pad should be kept thin to reduce the turnover moment of the support plate 92.The height of the wedge is related to (K), the modulus of elasticity of the compression spring; for example, if a 2,000-pound spring force is desired at maximum compression by the wedge, then a four-inch spring when compression-deflected two inches by a two-inch high wedge would be suitable for this application to provide a substantially linear increase in force as the stopping apparatus moves along the length of the wedge. The length of the wedge is selected to be adequate to satisfactorily bring the moving vehicle to a full stop at a place clear of the physical obstruction to be avoided. The initial vehicle velocity upon hitting the bumper pad 46 determines how far along the wedge the vehicle will travel before the vehicle is stopped. The normal vehicle stop in the passenger station is before the vehicle hits the pad 46 of the stopping apparatus here described.Some available adjustments here are to tighten the brake pad compression springs as desired to increase the level of initial braking force, or change the modulus of elasticity of the springs or to change the frictional characteristic of the brake pad material itself. The wedge is relatively expensive to change and would probably be left alone once it is installed on the top surface of the flange 36. The top surface of the wedge 44 should be kept relatively clean and dry to function as desired. If water is a problem, a metal brake pad can be used since a metal brake pad will not absorb water and the brake pressures can be considerably higher to minimize the operational disturbance by a water film. The location of the web along the respective sides of the guide beam wedge as shown in Figures 5 and 6 should help keep the braking surface of the wedges more clean and more dry.

WHAT WE CLAIM IS: 1. A vehicle-stopping apparatus to stop in a jerk-free manner a moving vehicle which is steered by a longitudinal guide member fixedly disposed to steer and guide the vehicle in its direction of motion, the moving vehicle being stopped after it hits the stopping apparatus which is stationary, said apparatus comprising: at least one ramp means disposed in fixed relation to said guide member; a cart means disposed to move along said guide member and including means to resist any tendency of the cart means to disengage from said guide member; a frictional pad means supported by the cart means and disposed to engage said ramp means in such a manner that movement of said pad means in the direction of the guide member and in engagement with the ramp means progressively increases a frictional force between the pad means and the ramp means; and adjustable means to select and maintain an initial pressure-loading of the frictional pad means on the ramp means so that depending on the ramp profile, a desired characteristic of vehicle velocity versus stopping distance can be achieved by suitably setting said adjustable means.

2. The stopping apparatus of claim 1, with said frictional pad means including a plurality of spring-loaded brake shoes.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. position by the channel sides 94 and 96. In relation to Figure 2, the support wheel 35 prevents the stopping apparatus from nosediving upon the initial impact of the moving vehicle into the pad 46 and the support wheel 33 holds the brake pads in position and forcing down against the top surface of the wedge 44 as the apparatus moves to the right during a vehicle-stopping operation. These wheels could be well known and readily available ball-bearing devices having inner and outer race members, with an axle extending through the inner race. These wheels can be removed from the frame member 30 when the stopping apparatus is initially positioned relative to the guidebeam 14 and wedge 44, and thereafter the wheels are replaced to hold the stopping apparatus in the desired operating position. If the bumper pad 46 is about two feet high and the stopping apparatus has a length of about four feet, it is reasonable to expect brakeshoe pressures against the wedge 44 in the order of 120,000 pounds or so for a typical vehicle weight of 20,000 lbs. and operational relationships such as shown in Figure 4; each brake shoe may have dimensions of about six inches by 10 inches, with the six-inch dimension being parallel to the longitudinal axis of the guide beam 14. It is desired to provide a gradually increasing braking force as shown in Figure 4, so the wheel 35 is provided to prevent a tendency of the stopping apparatus to nose dive while accelerating after initial impact by the vehicle and to prevent a corresponding undesired increase in brake pressure against the wedge 44; this would cause undesired initial bumps in each of the force curves, the jerk curves and the deceleration curves shown in Figure 4. When it is desired to restore the stopping apparatus to its original position after a vehicle has been stopped, the brake pads can be released by loosening the compression springs for each of the brake pads in relation to the wedge. The support plate 92 can be in the order of 1/2 inch thick, and the brake pad 41 can be about 1/4 inch thick. The number of compression springs operative with each support plate 92 can be two or three, depending on the desired brake pad force against the wedge and the physical size of the available springs for this purpose. Also, three or four brake pads can be employed, depending upon the kinetic energy of the moving vehicle to be absorbed in braking to a stop a normal vehicle. The brake pad should be kept thin to reduce the turnover moment of the support plate 92.The height of the wedge is related to (K), the modulus of elasticity of the compression spring; for example, if a 2,000-pound spring force is desired at maximum compression by the wedge, then a four-inch spring when compression-deflected two inches by a two-inch high wedge would be suitable for this application to provide a substantially linear increase in force as the stopping apparatus moves along the length of the wedge. The length of the wedge is selected to be adequate to satisfactorily bring the moving vehicle to a full stop at a place clear of the physical obstruction to be avoided. The initial vehicle velocity upon hitting the bumper pad 46 determines how far along the wedge the vehicle will travel before the vehicle is stopped. The normal vehicle stop in the passenger station is before the vehicle hits the pad 46 of the stopping apparatus here described.Some available adjustments here are to tighten the brake pad compression springs as desired to increase the level of initial braking force, or change the modulus of elasticity of the springs or to change the frictional characteristic of the brake pad material itself. The wedge is relatively expensive to change and would probably be left alone once it is installed on the top surface of the flange 36. The top surface of the wedge 44 should be kept relatively clean and dry to function as desired. If water is a problem, a metal brake pad can be used since a metal brake pad will not absorb water and the brake pressures can be considerably higher to minimize the operational disturbance by a water film. The location of the web along the respective sides of the guide beam wedge as shown in Figures 5 and 6 should help keep the braking surface of the wedges more clean and more dry. WHAT WE CLAIM IS:

1. A vehicle-stopping apparatus to stop in a jerk-free manner a moving vehicle which is steered by a longitudinal guide member fixedly disposed to steer and guide the vehicle in its direction of motion, the moving vehicle being stopped after it hits the stopping apparatus which is stationary, said apparatus comprising: at least one ramp means disposed in fixed relation to said guide member; a cart means disposed to move along said guide member and including means to resist any tendency of the cart means to disengage from said guide member; a frictional pad means supported by the cart means and disposed to engage said ramp means in such a manner that movement of said pad means in the direction of the guide member and in engagement with the ramp means progressively increases a frictional force between the pad means and the ramp means; and adjustable means to select and maintain an initial pressure-loading of the frictional pad means on the ramp means so that depending on the ramp profile, a desired characteristic of vehicle velocity versus stopping distance can be achieved by suitably setting said adjustable means.

2. The stopping apparatus of claim 1, with said frictional pad means including a plurality of spring-loaded brake shoes.

3. The stopping apparatus of claim 1, with

said ramp means including a wedge-shaped ramp member having a length determined by a desired stopping distance of said vehicle.

4. The stopping apparatus of claim 1, wherein said cart means includes a bumper which in use will be impinged upon by the moving vehicle so as to cause the frictional pad means move along said ramp means to stop said vehicle.

5. The stopping apparatus of claim 1, with the ramp means having a profile so as to provide a controlled and substantially linear increase in frictional retarding force between the ramp means and said frictional pad means.

6. The stopping apparatus of any preceding claim wherein said means to resist comprises a plurality of rollers mounted on said cart, said rollers being guided by. faces of the guide member.

7. The stopping apparatus as in any preceding claim, wherein said adjustable means comprises a plurality of screw members provided to impart movement under pressure to said frictional pad means.

8. The stopping apparatus as in any preceding claim, wherein said guide member comprises an "I" beam installed along the length of a roadway, wherein said ramp means is mounted on the top flange of the "I" beam.

9. The stopping apparatus as in any of claims 1 to 7, wherein said guide member comprises an "I" beam, and wherein the apparatus includes two of said ramp means disposed one each on each side of the web of the "I" beam said web being aligned vertically in space.