US2892418A - Road tunnels - Google Patents

Description

l 'auf June 30, 1959 Filed May 20. 1953 F. CENA 2,892,418

ROAD TUNNELS 5 Sheets-Shea?I 1 13' off/wf- June 3o, 1959v F. cl-:NA

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June 30, 1959 F. CENA 2,892,418

R/OAD TUNNELS l Filed May 2,0'. 1955 l 5 Sheets-Sheet. 3

y June 3o, 1959 F. CENA l 2,892,418

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ROAD TUNNELS Filed May 20. 1953 5 Sheets-Sheet 5 United y States Patent O ROAD TUNNELS Ferdinando Cena, Turin, Italy Application May 20, 1953, Serial No. 356,136 Claims priority, application Italy January 17, 1953 4 claims. (ci. 104-172) Y This invention relates to improvements in road tunnels. It is known that all road tunnels exceeding in length a certain limit, should be artificially ventilated. This limit can vary in accordance with t-he tunnel profile and section, importance of traffic, climate and weather conditions, prevailing wind, etc. v

Broadly, it may be assumed that natural ventilation without the use of special Ventilating plants should be limited to tunnels not exceeding 600-700 meters in length. When the intensity of traffic ranges within moderate limits, and weather conditions are exceptionally favourable to natural air circulation in the tunnel, tunnel lengths up to about 3 kilometers may be reached without the vneed for forced ventilation of the tunnel.

However, wit-h a great traic, even in the last-mentioned cases, the carbon monoxide concentration in the air filling the tunnel rapidly increases, often with a considerable reduction in visibility owing to smoky exhaust from the engines of motor vehicles travelling through the tunnel.

Consequently, any road tunnel of a certain importance should in the end be provided with a forced ventilation plant. Now, the cost of such plant audits upkeep is very high and appreciably affects the `cost of installation and service.

It has, however, been found that any type forced ventilation plant for road tunnels is insufficient for totally eliminating the danger of pollution Ifrom toxic stuffs from the inside of the tunnel and reduction in visibility therethrough when the traic through the `tunnel reaches a given intensity, which necessitates holding up traffic during more Vor less long periods of time,` at any rate till the air within the gallery has been sufliciently purified to admit'of resuming traffic. Y

This invention provides road tunnels with means adapted to eliminate forced draught plants or to considerl ably reduce them in capacity, thereby cutting down cost of installation upkeep and service.

A road tunnel according to this inventionis provided with means permitting travel therethrough of vehicles with their engines in an inoperative condition, the vehicle weight resting on the vehicle wheels without loading the vehicle on carriages, platforms or similar transporting means.

With this object in view, a motor vehicle convoy is formed at the inlet ofthe tunnel, the vehicles being connected together through suitable means to a suitableV propelling means, such as an electric locomotive or endless rope or belt conveyor which pulls them with theirA engines in an inoperative condition through the tunnel to the outlet thereof where the vehicles are released from the trailer or propelling means and are allowed 'to run on their engines again. v

It is 4understood that when endless rope or belt conveyors are used, they should be operated by driving means of such type and in such arrangement as not to pollute the air in the tunnel during operation.

z For a safer propelling of a convoy comprising vehicles fcc connected to a trailing means and in order toV avoid traction of the individual vehicles attached in line to one another according to this invention, each vehicle is secured to a carriage slidable on rails preferably arranged in a small auxiliary tunnel situated beneath the road surfaces, and extending throughout the length of the tunnel. These carriages can be connected together by suitable couplings and to trailing means, such as au electric locomotive or an endless rope or belt conveyor extending throughout the length of the tunnel or part thereof. v

The vehicle is secured to the carriage through suitable means provided with hooks, such as ropes, draw-bars or push-bars provided with members for engaging the motor vehicles projecting above the road surface from the auxiliiary tunnel through a narrow longitudinal slot symmetrically situated with respect to the plane of symmetry of the road surface of the actual or main tunnel.

The attachment of the vehicles and individual carriages as well as the arrangement of the electric locomotive according to this invention can be such that the unit forming the vehicle train to be conveyed through the tunnel can all be pushed or drawn during its movement.

According to this invention the use of the above described carriages does not necessarily imply building an auxiliary tunnel underneath the road surface. The carriages c an run on guide or rails arranged in any suitable manner in the tunnel, for instance in proximity of the roof. A

The invention is more particularly advantageous in sloping tunnels in which the translational movement of the vehicles secured to the abovementioned carriages with their engines in an inoperative condition partly takes place by gravity by virtue of the weight of the vehicles and carriages, thereby assisting the electric locomotive which action may be limited to a controlling and braking function, in order to vavoid exceeding a determined safety speed of the convoy. In an opposite uphill direction, the electric locomotive or suitably trailing or pushing means of another type propel the convoy. Tunnels of this type afford highly [favourable natural conditions for ventilation.

v According to this invention the plant of the ytype referred to above can be combined with a tunnel of a special type, Idesigned, if local conditions permit, to include -two runs opposite in slope, each comprising successive por-l tions of gradually decreasing inclination from the inlet athigher level -towards the outlet lower level of the tunnel of each run.

It is then possible -to propel the convoy at high speed from the inlet of the tunnel and gnadually decrease its speed towards the outlet. In this case also motor-ve hicles with their engines in an inoperative condition travel through the gallery substantially under the action of their own weight and the battery of carriages connected to a propelling means `or an electric locomotive is more particularly intended to act as safety devices for adjusting both the spacing between the vehicles depending upon the spacing of the carriages, and the speed through the effect of the braking action exerted by the electric locomotive or propelling means.

Itis understood that the vehicles could in this ease be started with their engines of without attaching them in any manner, adjustment of their speed of transit through the tunnel being effected merely by the length and slope of the individual sections of the down-hill run of the tunnel.

j connections.

'Further features and objects of this invention will be more clearly understood from the appended description referring to the drawings, wherein:

Figure l is a longitudinal section of a tunnel portion according to this invention,

Figure 2 is a sectional view of a section of a modified tunnel according to this invention,

Figure 3 is a side view of a carriage,

Figure 4 is a section on line IV-IV of Figure 3,

Figure 5 is a side view of a constructional detail of the carriage,

Figure 6 is a plan view, of the carriage shown in Fig. 5,

Figure 7 is a part sectional side view of a constructional detail ofthe carriage according to a modification,

Figure 8 is a section on line VIIl-VIII 0f Figure 7,

Figure 9 is a side view of a carriage according to an other modification,

Figure 10 is a section on line X--X of Figure 9,

Figure 1l is a sectional view of a portion of a road tunnel provided with an endless rope conveyor,

Figure 12 is a sectional view on line XII- XII of Figure ll,

Figure 13 is a view of a constructional detail of the endless rope conveyor on an enlarged scale.

Figure 14 isa section on line XIV- XIV of Figure 13 on a further enlarged scale,

Figure 15 is a diagrammatic sectional view of a tunnel with downwardly directed slope,

Figure 16 is a diagrammatic sectional view of a con structioual detail of a tunnel shown in Fig. ll,

Figure 17 is cross sectional view of a railway tunnel converted to a road tunnel equipped according to this invention,

Figure 18 is a cross sectional view of a similar tunnel according to a modification.

Referring to Figure l, 1 denotes the vehicles conveyed through the road tunnel 2 with their engines in an inoperative condition, their weight bearing on their respective wheels rolling on the road surface 3 in the tunnel. The rear axle of each motor vehicle is secured to a carriage 4 running onv rails 5 arranged in an auxiliary tunnel 6 beneath the road surface 3 in the tunnel 2.

The carriages 4 are connected together by means of spacing bars 7, `the lforemost carriage being connected with the electric locomotive 8 by means of a bar 9.

The electric locomotive 8 is operated by the electric current derived by means of a trolley 10 from the overhead conductor 11 hung to the tunnel roof 12, and is provided with reserve storage batteries to ensure further operation on accidental failure of current.

The construction shown in Figure 2 differs from Figure l in that the carriages having secured thereto the vehicles conveyed through the tunnel with their engines in an inoperative condition, are translated by means of endless band conveyors 13, 14, instead of by an electric locomotive. The conveyor bands 15, 16 are formed with projections 17 at right angles to the band surfaces which during motion of the conveyors engage suitable abutments on the carriages 4.

The vehicles are conveyed one by one through the tunnel, without connecting together the carriages to which the vehicles are attached.

By employing the endless bands a variable feed rate launching band is arranged at the inlet of the tunnel. This band of reduced length is intended to accelerate the vehicles secured to the carriages at a speed substantially equalling the feed rate of the band conveying the vehicle through the tunnel. As, for example, the conveyor 15 in Fig. 2 can be driven at a progressively increasing speed after projections 17 engage an individual carriage 4 and thereby accelerate the carriage to a selected speed. The carriage is then automatically transferred to conveyor 16 which moves it and the vehicle throughout the length of the tunnel at said selected speed through.-

4 out the full length of the tunnel to the exit thereof. It willV be understood that rather than using a sole constant speed conveyor such as conveyor 16 a plurality of constant speed conveyors may be employed with the individual carriages and towed vehicles being autovmatically transferred from conveyor to conveyor.

Figures 3 to 9 show some types of the carriages to which the vehicles to be conveyed through the tunnel are attached, as well as constructional details.

The carriage construction shown in Figure 3 and 4 is substantially similar to the construction diagrammatically shown in Figures l and 2.

The carriage shown in Figures 3 and 4 comprises a frame 18 carried by four upper wheels 19 running on the rails 5 carried by the cross members 20 anchored to the side walls 21 of the auxiliary gallery 6. A pair of lower wheels 22 engage below the rails 5 and prevent any sticking of the carriage.

As mentioned above, the carriages are connected together by spacing draw-bars 7 connected thereto through the interposition of cardan joints 23 to assist the carriages in going over from one tunnel portion to another portion differing in slope.

The frame 18 has attached to opposite ends hooks 24 reaching slightly above the road surface 3 through a central slot 25 connecting the road tunnel 2 with the auxiliary tunnel 6.

Each hook 24 is connected to the frame 18 through the interposition of a spring 26 in order to be capable of a slight displacement in a vertical direction.

The hooks 24 can have attached thereto a rope 27 provided with a shock damper 28 and two jaws 29 adapted to clamp, for instance, the rear axle housing portions'actuated on both sides of the diierential casing of the vehicle, said jaws being anchored to the carriage and connected to ithe shock damper over a cross member 30.

The rope 27 can be made a shorter or longer and since this rope is capable of oscillation in a vertical and a horizontal plane, the jaws 29 can be easily suited to the axle of a vehicle of any height and transverse displacement of the trailed vehicle during feed cannot injure the attachment means.

The attachment means for fastening motor vehicles to the carriages shown in Figures 3 and 4 are arranged to draw the motor vehicle axle connected thereto during their movement through the tunnel.

Figs. 5 and 6 show a modified structure of the means for connecting the carriage to the vehicle to be conveyed. Each end of the cross rod 30 has secured thereto a clamping device formed by a pair of lower jaws 31 keyed to the ends of a cross shaft 32 rotatably supported by the cross rod 30 and carrying at half-length a lever 33 hinged at one end to the core of an electromagnet 35, the upper jaws 36 of the clamping device arranged on either side of the bar 30 being iixedly connected to the cross member 30. A spring 7 fastened between the shock absorber casing 28 and the end of lever 33 remote from the core of the electromagnet tends to maintain the clamping device 31, 36 in its opened position. Current ows to the electromagnet through a cable 38 which is preferably connected by a longitudinal conductor formed by portions interconnected by plugs and socket members extending throughout the carriages and connected to the electric locomotive for controlling from the drivers cabin engagement and disengagement of the clamping devices 31 and 36 of the motor vehicle axles with respect to the electric locomotive by connecting and disconnecting by means of a switch Ithe current energising the electromagnets 35.

In the example shown, during transit through the tunnel all the electromagnets are fed by the current and hold the clamping devices 31, 36 closed. 0n reaching the tunnel outlet, the engineer on the electric locomotive cuts out the current automatically and all the clamping devices 31, 36 open under the action of their respective springs 37.

Figures 7 and 8 show a modified fastening, comprising a hook 39 connected over'a shock absorber 28 to a helically wound band spring 40 connected by its inner end to the carriage frame 18.

This arrangement is advantageous inasmuch as the fastening hooks together with their shock absorber are automatically withdrawn by the action of the helical spring 40 into the slot 25 in the road surface, from which they do not project when they are released from the vehicles. Figures 9 and 10 show a modified carriage construction, comprising a top wheel 41 rolling on the upper surface of a rail 42, which is, for instance, anchored below Ain the oor of the auxiliary tunnel 6, provided with four rollers 43 with a vertical axis adjacent to the sides of the rail web and holding the carriage ina vertical position. The connection between the carriages as well as the means for attaching the vehicles thereto do not differ appreciably from those described above.

An embodiment of the invention employing an endless rope conveyor is shown in Figures l1 to 14.

Referringto Figures 1l `and 12, the tunnel 70, of a size suitable for meeting the requirements of traic in both directions has arranged therein in proximity to the roof an endless rope driven at a constant speed by a driving or transmission wheel rotated by suitable means, for instance from an electric motor (not shown). The rope is arranged in such manner that its two runs 72 and 73 parallel with each other and arranged at the same height are carried by bearings 74 provided with rollers 75 and anchored in the tunnel roof. The direction of movement of each run (indicated on the drawing by the arrows) of the rope is opposite to the direction of movement of the other run. Carriages 76 are fastened to the rope by means of suitable vices, each carriage having hinged to its lower portion a ring 77 to which is fastened the hook 78 secured to the upper end of a rope, of which the lower end is secured through the interposition of a shock absorber 79 to the frame of a Vehicle 80. The spacingof the two runs 72, 73, respectively of the rope isA such as to admit of travel through the tunnel of vehicles in opposite directions, each vehicle being drawn by a carriage secured to its respective rope run.

.The above described arrangement would be impractical if the carriages were constantly attached to the rope which necessarily moves at highspeed. In fact, it would be extremely diflicult, if not impossible, to disconnect the trailed vehicle reaching the outlet end of the tunnel and to connect the vehicle at the inlet end.

In order to avoid this drawback, the invention provides an arrangement substantially known per se in other fields, which permits of disconnecting the rope and stopping the carriage as it reaches the tunnel end, its stoppage toV wait fora vehicle to be conveyed through the tunnel, and` its acceleration and subsequent connection to the rope run opposite that which has reached the tunnel outlet.

With this object in view, the carriage frame, which is substantially in the form of a vertical plate 81 (Figures 13 and 14) is provided with a vice which clamps and releases the conveyor rope 72, respectively. This vice comprises a stationary member 82 and a movable member 83 in the form of a lever rotating about the shaft 84 fixed to the frame 81. The spring 85 tends to maintain the vice constantly in its open position, in which the members81 and 82 do not engage the rope 72.

The end 83a of the member 83 contact an eccentric 86 keyed to the pivot 87 rotatably mounted on the carriage frame 81.

Al laterally projecting lever 88 is fixedly connected to the pivot 87. v

Two rails or guides 89, 90, respectively (Figures 13 and 14) are suspended near the region at which the conveyor rope travels over the driving or transmission wheel 71 on either side thereof, said rails o r guides being jarranged in a vertical plane extending through the associated rope run, over and beneath the rope, respectively.

A set of rollers 91 95 and 91 95 (Fig. 12) are aligned over each of the top rails 89, said rollers being mounted in a frame 96 anchored to the tunnel roof which further carries the rails 89 and 90. The rollers are constantly rotated by a motor, such as an electric motor through a drive (not shown) such that the successive rollers'rotate at a speed such that their peripheral speed gradually decreases from the roller 91, 91', respectively, of which the peripheral speed nears the feed rate of the conveyor rope. The peripheral speed of the roller 95 and 95', respectively is very low, near zero.

Assuming the rollers above the run 72 of the rope rotate in the direction denoted by the arrows in Figure 13, the rollers over the side 73 rotate at equal peripheral speeds butin opposite directions.

The mechanism described operates as follows.

When the carriage 76 trailing the vehicle 80, anchored to the run 72 of the rope reaches the end of the rails 89 and 90, the latter engage the rollers 97, 98, respectively (Figures 13, 14). At the same time the end of lever 88 is engaged by stationary guide 99 which moves it from its lowered position, in which the vice is closed, by the action of the eccentric 86 to the raised position shown in Figure 14, in which the carriage 76 is disconnected from the run 72 of the rope. At the same time the shoe fast with the carriage frame 81 successively comes into contact with the rollers 91 95 and the carriage speed is reduced nearly to nil by the effect of the friction between the upper surface of the shoe and the rollers 91 to 95. The vehicle can then be released and leaves the tunnel outlet by self-propulsion, as the carriage is moved by hand by pulling the rope on to the rail 101 connecting the rails 89 together (Fig. 12).

When a vehicle comes in front of the tunnel inlet, it is fastened to the carriage carried by the rails 101, the carriage being drawn by hand in the direction of movevment of the run 73 of the conveyor rope till the shoe by a guide similar to the guide 99 which lowers the leverA 88, thereby fastening the carriage to the run 73 of the conveyor rope.A The carriage is thus moved to the opposite end of the tunnel carrying along the vehicle.

It is understood that the plant has been described and illustrated in a diagrammatic manner for the purpose of explanation and can undergo various modiiicatoins without departing from the scope of this invention.

Figure l5 shows diagrammatically a preferred embodiment of a sloping road tunnel, with which the above described arrangement can be usefully combined for the transit through the tunnel of motor vehicles with their engine in an inoperative condition.

As is visible from the drawing, the tunnel is made up of two'runs, each of which is intended for travel of the vehicles in one direction, denoted by the arrows in Figure 15.

Each run is arranged in such manner as to bring about a difference in level between its inlet I, I', respectively and outlet O, O', respectively, the vehicles constantly running down-hill through the tunnel.

The inlets I, I' of the two sides of the tunnel are of course connected with the main road by sloping connections (not shown). l

Preferably, the slope is not uniform through the length of each tunnel side.

Each side is composed of a plurality of successive portions decreasing in slope 43, 44 47 and 43', 44' 47', respectively. l

Y The vehicles entering the tunnel inlet I or I' with oneway tralic first travel over a short launching track 43 in order to acquire an initial speed of about 40-50 km./h. (for x motor vehicles of an average weight of about 2, metric tons), which is maintained over the portion 44 or 44 of suitable slope.

The subsequent sections 45, 46 or 45', 46' should be such in slope that the speed of the vehicles travelling through the tunnel is gradually reduced to 30-35 km./ h. and 20-30 km./h. respectively.

The nal section 47 or 47 is of further reduced steepness, so that the vehicle stops at the tunnel outlet O or O'. For the sake of safety a short up-hill section 49 can be provided at the outlet (Fig. 16).

The tunnel of the abovedescribed type is equipped with carriages and propelling means according to this invention as previously described with reference to Figures l to 10.

It will be understood that for the sake of economy at lirst one side only for two rows of vehicles may be provided, allowing the vehicles to freely travel downhill through the tunnel, the propelling-means being employed merely on the up-hill path.

The propelling means are in any case operated only when the composition of the atmosphere and visibility within the tunnel, detected for instance automatically by suitable means make it advisable to hold up trafc with the engines running.

This invention may be particularly advantageous with road tunnels resulting from the adaptation of existing railway tunnels to the tratiic of road motor vehicles.

The necessity of such adaptation may arise, for instance, upon disruption of the railway lines owing to war damage. In this case it is convenient to utilize railway tunnels, which would otherwise remain inoperative and useless, for the traic of special military vehicles by, removing from the tunnels the rails and replacing them by a road surface of suitable type.

It is further convenient to equip such converted tunnels with one of the previously described propelling means, both for regulating traic and because the trafc will obviously be very great.

Two manners of carrying out road tunnels by converting railway tunnels shall now be described with reference to Figures 17 and 18. As will be clearly seen from the drawing, the rails have been removed from the tunnel 50 and replaced by a concrete road paving 51. The road paving is interrupted by two longitudinal slots 52, 53, respectively about 25 centimeters wide, symmetrically arranged with respect to the longitudinal middle plane of the tunnel and parallel therewith. A rail 54, 55, vrespectively is anchored to the bottom of each of said slots through the interposition of wood slabs 56, 57, respectively, for the sake of quick replacement. These rails form the guide for the carriages, for instance of the type shown in Figures and 6, to which are secured the motor vehicles travelling through the tunnel in both directions.

with their engines in an inoperative condition, propelled for instance by an electric locomotive. v

The profile of the road paving is of special shape designed to form two ilat road surfaces 58, 59 (Fig. 17) laterally confined by lateral inclined surfaces 60, 61 and 62, 63, respectively, so that the vehicle is guided on its transit through the tunnel. A further shape of the prole of the road paving is shown in Fig. 18 in which the elements corresponding to those of Fig. 17 are denoted by the same reference numerals.

In the construction shown in Figure 18 the grooves 52 and 53 accommodating the rails 54, 55 are arranged further away from the longitudinal central plane of the tunnel, the inclined surfaces 61, 62 being eliminated to form a at central road surface 64 which may be used for the transit of special large-sizer vehicles, such as, for instance, trailers for transporting heavy armoured cars. In order to enhance the action of the sloping surfaces 60 63, the latter may be lined with sheet metal.

Of course the rails on which the carriages roll may be in the number of two on either side and can be arranged in auxiliary tunnels such as shown in Figures l and 2Q The propelling means can be of any suitable previously described type.

What I claim is:

1. In a tunnel having a road and a channel beneath the surface of the road communicating with the surface of the road a vehicle towing system comprising, in combination, a plurality of movable carriages disposed in said channel for towing the vehicles along the road, means individually and releasably connectable to a corresponding carriage for selectively connecting and disconnecting vehicles individually to individual carriages, means in said channel for guiding said carriages through said channel when the carriages are moved therethrough, means releasably engageable with said carriage for selectively moving the individual carriages in tandem and in spaced relationship at selected speeds collectively along said channel, said last mentioned means comprising at least one` rotatably driven first endless-band towing means disposed in said channel extending longitudinally therein for engaging said carriages to move them along said channel at a constant rate of speed and a short rotatably :driven second endless-band towing means driven at a variable rate of speed and disposed at the inlet of the tunnel for accelerating the carriages together with the vehicles connected thereto and delivering them to said first constant speed endless band towing means, and non-combustion type motors operably connected to said first and second towing means respectively to drive them independently of each other so that the atmosphere in the tunnel is not affected by said motors, whereby vehicles are propelled along the surface of the road with their engines inoperative so as not to contaminate the atmosphere in the tunnel by exhaust gases.

2. In the combination according to claim 1, in which said guiding means comprises a rail in the channel, said rail having a web portion and in which a carriage 'comprises a rotatable wheel riding on said rail, a plurality of rollers spaced from the axis of the wheel and positioned on either side of the web said rollers slidably engaging the rail, substantially rigid connection means between the rollers and the wheel, whereby a carriage is movable on the rail and guided thereon.

3. In the combination according to claim l, in which said guiding means comprises two rails fixed on opposite side walls of the channel beneath the surface of the road, each of said rails having an upper and a lower transverse portion substantially normal to a web, means mounting the rails in fixed position with the webs substantially parallel to the side wall of the channel, and in which a carriage comprises a first frame, two pairs of rotatable wheels mounted on said frame, said wheels having a peripheral projection on the inner side adjacent the frame so as to ride on the upper transverse portion of the rails, a second frame removably connected to said first frame and extending downwardly from said first frame, a pair of spaced wheels mounted on said second frame each of said last mentioned wheels having peripheral projections so as to ride and be guided on the lower transverse portions of the rails, whereby said carriage is movable and guided on the rails.

4. A system for towing vehicles through a tunnel having a road, while the vehicles bear on the road surface by means of their respective wheels and have their engines inoperative, comprising, in combination, means comprising a plurality of like devices connectable to respective vehicles individually for towing and guiding the vehicles collectively through said tunnel in tandem, means individually connectable to said devices for selectively connecting and disconnecting vehicles individually to said towing and guiding devices, means cooperating with said devices to guide them along a predetermined path in Said tunnel, means releasably engageable with said de s Vf vices for moving said towing and guiding devices along the tunnel in said predetermined path, said moving means comprising at least one rotatably driven irst endless band propelling means disposed extending longitudinally in a direction corresponding with a direction in which said tunnel extends and having means fixed thereon for releasably engaging said devices for propelling said towing and guiding devices along the tunnel in tandem at a constant speed and a second endless band propelling means movable at a variable speed and arranged in tandem with said rst endless band at the tunnel inlet and having means fixed thereon for releasably engaging said towing and guiding devices successively together with individual vehicles connected thereto to accelerate said devices until they reach the constant speed of travel of said rst mentioned endless band propelling means disposed along the tunnel and for subsequently releasing said towing and guiding devices and delivering them with the vehicles connected thereto to the first propelling means successively, driving means of the non-combustion type operably connected to the first and second propelling means for reversibly driving said rst and second propelling means independently of one another so that the atmosphere in the tunnel is not affected by the driving means and the vehicles.

References Cited in the le of this patent UNITED STATES PATENTS Creighton Ian. 17, 1888 McLaughlin July 15, 1890 Dunne May 17, 1892 Ashland May 15, 1906 Neebe May 5, 1908 Willson Oct. 13, 1908 McDonagh et al Dec. 15, 1908 Harling Dec. 14, 1909 Smith Sept. 10, 1912 Bates Feb. 29, 1916 Hiss et al. Dec. 7, 1920 Mason Dec. 5, 1922 Hunter May 6, 1924 Hewes Ian. 1, 1929 Butler Nov. 26, 1935 McCaul Dec. 16, 1952 Boyko et al. Dec. 16, 1952 Kendall et al. July 3l, 1956

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